全文获取类型
收费全文 | 1681篇 |
免费 | 88篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 47篇 |
大气科学 | 122篇 |
地球物理 | 416篇 |
地质学 | 608篇 |
海洋学 | 166篇 |
天文学 | 209篇 |
综合类 | 4篇 |
自然地理 | 214篇 |
出版年
2023年 | 6篇 |
2021年 | 19篇 |
2020年 | 34篇 |
2019年 | 28篇 |
2018年 | 41篇 |
2017年 | 50篇 |
2016年 | 50篇 |
2015年 | 40篇 |
2014年 | 49篇 |
2013年 | 93篇 |
2012年 | 54篇 |
2011年 | 105篇 |
2010年 | 84篇 |
2009年 | 94篇 |
2008年 | 84篇 |
2007年 | 52篇 |
2006年 | 87篇 |
2005年 | 68篇 |
2004年 | 56篇 |
2003年 | 61篇 |
2002年 | 52篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 24篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 30篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 21篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 20篇 |
1980年 | 8篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 15篇 |
排序方式: 共有1786条查询结果,搜索用时 93 毫秒
191.
192.
The first fossil echinoids are recorded from the Cayman Islands. A regular echinoid, Arbacia? sp., the spatangoids Brissus sp. cf. B. oblongus Wright and Schizaster sp. cf. S. americanus (Clark), and the clypeasteroid Clypeaster sp. are from the Middle Miocene Cayman Formation. Test fragments of the mellitid clypeasteroid, Leodia sexiesperforata (Leske), are from the Late Pleistocene Ironshore Formation. Miocene echinoids are preserved as (mainly internal) moulds; hence, all species are left in open nomenclature because of uncertainties regarding test architecture. All Miocene taxa are recorded from single specimens apart from the 27 assigned to Brissus. Schizaster sp. cf. S. americanus (Clark) is compared to a species from the Oligocene of the south‐east USA. Brissus sp. cf. B. oblongus is close in gross morphology to a taxon from the Miocene of Malta. Leodia sexiesperforata is identified from fragments with confidence, being the only extant Antillean sand dollar with elongate ambulacral petals that is limited to carbonate substrates. The Miocene echinoids of Grand Cayman, although of limited diversity, are mainly comprised of genera common in comparable mid‐Cenozoic carbonate environments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
193.
Jutta ZIPFEL Bradley L. JOLLIFF Ralf GELLERT Kenneth E. HERKENHOFF Rudolf RIEDER Robert ANDERSON James F. BELL III Johannes BRÜCKNER Joy A. CRISP Philip R. CHRISTENSEN Benton C. CLARK Paulo A.
De SOUZA Jr. Gerlind DREIBUS Claude
D’USTON Thanasis ECONOMOU Steven P. GOREVAN Brian C. HAHN Göstar KLINGELHÖFER Timothy J. McCOY Harry Y. McSWEEN Jr. Douglas W. MING Richard V. MORRIS Daniel S. RODIONOV Steven W. SQUYRES Heinrich WÄNKE Shawn P. WRIGHT Michael B. WYATT Albert S. YEN 《Meteoritics & planetary science》2011,46(1):1-20
Abstract– The Opportunity rover of the Mars Exploration Rover mission encountered an isolated rock fragment with textural, mineralogical, and chemical properties similar to basaltic shergottites. This finding was confirmed by all rover instruments, and a comprehensive study of these results is reported here. Spectra from the miniature thermal emission spectrometer and the Panoramic Camera reveal a pyroxene‐rich mineralogy, which is also evident in Mössbauer spectra and in normative mineralogy derived from bulk chemistry measured by the alpha particle X‐ray spectrometer. The correspondence of Bounce Rock’s chemical composition with the composition of certain basaltic shergottites, especially Elephant Moraine (EET) 79001 lithology B and Queen Alexandra Range (QUE) 94201, is very close, with only Cl, Fe, and Ti exhibiting deviations. Chemical analyses further demonstrate characteristics typical of Mars such as the Fe/Mn ratio and P concentrations. Possible shock features support the idea that Bounce Rock was ejected from an impact crater, most likely in the Meridiani Planum region. Bopolu crater, 19.3 km in diameter, located 75 km to the southwest could be the source crater. To date, no other rocks of this composition have been encountered by any of the rovers on Mars. The finding of Bounce Rock by the Opportunity rover provides further direct evidence for an origin of basaltic shergottite meteorites from Mars. 相似文献
194.
Deborah L. Domingue Faith Vilas Johan Warell Scott L. Murchie David T. Blewett Brian J. Anderson 《Icarus》2010,209(1):101-124
Disk-integrated and disk-resolved measurements of Mercury’s surface obtained by both the Mercury Dual Imaging System (MDIS) and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft were analyzed and compared with previous ground-based observations of Mercury at 11 wavelengths. The spectra show no definitive absorption features and display a red spectral slope (increasing reflectance with increasing wavelength) typical of space-weathered rocky surfaces. The MDIS spectra show evidence of phase reddening, which is not observed in the MASCS spectra. The MDIS spectra are commensurate with ground-based observations to within 10%, whereas the MASCS spectra display greater discrepancies with ground-based observations at near-infrared wavelengths. The derived photometric calibrations provide corrections within 10% for observations taken at phase angles less than ∼100°. The derived photometric properties are indicative of a more compact regolith than that of the lunar surface or of average S-type asteroids. The photometric roughness of the surface is also much smoother than the Moon’s. The calculated geometric albedo (reflectance at zero phase) is higher than lunar values. The lower reflectance of immature units on Mercury compared with immature units on the Moon, in conjunction with the higher geometric albedo, is indicative of more complicated grain structures within Mercury’s regolith. 相似文献
195.
Natalia Astudillo Pierrick Roperch Brian Townley Cesar Arriagada Annick Chauvin 《Mineralium Deposita》2010,45(1):23-41
El Teniente porphyry copper deposit, the world’s greatest intrusion-related Cu–Mo ore body, is hosted within basaltic–andesitic
volcanic and gabbroic rocks (mafic complex). This ore body is strongly affected by multiple events of alteration/mineralization
with pervasive potassic and chloritic alteration and coetaneous with associated copper mineralization. We present paleomagnetic
results obtained from oriented samples at four locations within the mine and from two drill cores, 200 and 400 m long, respectively.
Samples are representative of all the main hydrothermally altered rock units, with emphasis on the mafic host rock and dacitic
(Teniente dacite porphyry) and dioritic porphyry intrusions. Magnetic experiments [hysteresis loop, isothermal remanent magnetization
(IRM), k–T curves, thermal, and alternating field demagnetization] show the presence of prevailing magnetite. Microscope and SEM observations
show two families of magnetite, (a) large multidomain magnetite grains, associated with biotite and chlorite of various different
hydrothermal alteration events, and (b) abundant small to medium grain-size magnetite (<10 μm) contained within plagioclase,
either related to an early Na–Ca–Fe alteration or included within plagioclase during magmatic crystal growth. While the Teniente
dacite porphyry and the quartz diorite–tonalite have low magnetic susceptibility (<0.0005 SI) and low natural remanent magnetization
(NRM, 10−4–10−3 Am−1), the mineralized mafic host rocks have usually high susceptibility (>0.01 and up to 0.2 SI) with NRM in the range 0.1–2 Am−1. Most mafic complex rock samples have univectorial magnetizations during alternating field or thermal demagnetization. Within
the mine, the magnetic polarity is spatially distributed. In the northern part of the deposit, the Teniente dacite porphyry,
the associated hydrothermal breccias, and the hosting mafic complex record a reverse polarity magnetization, also observed
in the El Teniente sub-6 mine sector immediately to the east and southeast. In the eastern part of the deposit, a normal polarity
is observed for samples of the mafic complex from the two long drill cores. There is no evidence for superimposed magnetizations
of opposite polarities in samples of the mafic complex. Anhysteretic remanent magnetization (ARM) in a DC field of 40 μT and
NRM have similar magnitude and comparable behavior upon alternating field demagnetization. The well-defined strong remanent
magnetizations associated with high unblocking temperatures (>500°C) indicate an acquisition of remanent magnetization during
mineralization by circulating high temperature fluids related with ore deposition. Paleomagnetic results and the recorded
polarity zonation suggest multiple mineralization events occurred at El Teniente, each one with its own evolution stages,
superimposed within the district. These results indicate that a simplified broad four-stage model for El Teniente, as presented
and overly employed by many authors, divided in (1) late magmatic, (2) main hydrothermal, (3) late hydrothermal, and (4) posthumous
stage, does not recognize various short-lived single mineralization events, some superimposed and some distinctly separated
in time and space. There is no paleomagnetic evidence for post-mineralization deformation 相似文献
196.
Juraj Majzlan Peter Glasnák Robert A. Fisher Mary Anne White Michel B. Johnson Brian Woodfield Juliana Boerio-Goates 《Physics and Chemistry of Minerals》2010,37(9):635-651
Jarosite phases are common minerals in acidic, sulfate-rich environments. Here, we report heat capacities (C
p) and standard entropies (S°) for a number of jarosite samples. Most samples are close to the nominal composition AFe3(SO4)2(OH)6, where A = K, Na, Rb, and NH4. One of the samples has a significant number of defects on the Fe sites and is called the defect jarosite; others are referred
to as A-jarosite. The samples, their compositions, and the entropies at T = 298.15 K are:
There are additional configurational entropies of 13.14 and 8.23 J mol−1 K−1 in defect and NH4-jarosite, respectively. A detailed analysis of the synchrotron X-ray diffraction patterns showed a large anisotropic peak
broadening for defect and NH4-jarosite. The fits to the low-temperature (approx. <12 K) C
p data showed that our samples can be divided into two groups. The first group is populated by the K-, Na-, Rb-, and NH4-jarosite samples, antiferromagnetic at low temperatures. The second group contains the H3O-jarosite (studied previously) and the defect jarosite. H3O- and defect jarosite are spin glasses and their low-T
C
p was fit with the expression C
p = γT + ΣB
j
T
j
, where j = (3, 5, 7, 9). The linear term is typical for spin glasses and the sum represents the lattice contribution to C
p. Surprisingly, the C
p of the K-, Na-, Rb-, and NH4-jarosite samples, which are usually considered to be antiferromagnetic at low temperatures, also contains a large linear
term. This finding suggests that even these phases do not order completely, but have a partial spin-glass character below
their Néel transition temperature. 相似文献
Sample | Chemical composition | S o/(J mol−1 K−1) |
---|---|---|
K-jarosite | K0.92(H3O)0.08Fe2.97(SO4)2(OH)5.90(H2O)0.10 | 427.4 ± 0.7 |
Na-jarosite | Na0.95(H3O)0.05Fe3.00(SO4)2(OH)6.00 | 436.4 ± 4.4 |
Rb-jarosite | RbFe2.98(SO4)2(OH)5.95(H2O)0.05 | 411.9 ± 4.1 |
NH4-jarosite | (NH4)0.87(H3O)0.13Fe3.00(SO4)2(OH)6.00 | 447.2 ± 4.5 |
Defect jarosite | K0.94(H3O)0.06Fe2.34(SO4)2(OH)4.01(H2O)1.99 | 412.7 ± 4.1 |
197.
Atmospheric tracer monitoring and surface plume development at the ZERT pilot test in Bozeman,Montana, USA 总被引:1,自引:1,他引:0
Arthur Wells Brian Strazisar J. Rodney Diehl Garret Veloski 《Environmental Earth Sciences》2010,60(2):299-305
A controlled release of CO2 was conducted at a field site in Bozeman, Montana, USA in July of 2008 in a multi-laboratory study of near surface transport
and detection technologies. The development of a subsurface CO2 plume near the middle packer section of the horizontal release was studied using soil-gas and surface flux measurements of
CO2. A perfluorocarbon tracer was added to the CO2 released from this section of the horizontal well, and the development of atmospheric plumes of the tracer was studied under
various meteorological conditions using horizontal and vertical grids of monitors containing sorbent material to collect the
tracer. This study demonstrated the feasibility of using remote sensing for the ultra low level detection of atmospheric plumes
of tracers as means to monitor the near surface leakage of sequestered CO2. 相似文献
198.
Susan H. BeVille Benjamin B. Mirus Brian A. Ebel George G. Mader Keith Loague 《Environmental Earth Sciences》2010,61(6):1249-1257
Hydrologically driven mass wasting in the form of landslides on steep slopes is a worldwide occurrence. High-profile events
in, for example, Brazil, Chile, the Philippines, Puerto Rico, and Venezuela during the last three decades all clearly illustrate,
based upon significant losses of life and property, that hydrologically driven slope instability in developed (urban) areas
can be a major geologic/environmental hazard. The focus of this study is the 1973 hydrologically driven Lerida Court landslide
in Portola Valley, CA, USA. Physics-based hydrologic-response simulation, with the comprehensive Integrated Hydrology Model,
was employed to forensically estimate the spatiotemporal pore pressure distributions for the Lerida Court site. Slope stability,
driven by the simulated pore pressure dynamics, was estimated for the Lerida Court site with the infinite slope/Factor of
Safety approach. The pore pressure dynamics for the Lerida Court site were reasonably captured by the hydrologic-response
simulation. The estimated time of slope failure for the Lerida Court site compares well with field observations. A recommendation
is made that hydrologically driven slope stability estimates including variably saturated subsurface flow be standard protocol
for development sites in steep urban settings. 相似文献
199.
Brian Wei Khong Chong Sandric Chee Yew Leong Victor S. Kuwahara Teruaki Yoshida 《海洋学报(英文版)》2022,41(12):142-151
Assessments of phytoplankton diversity in Sabah waters, North Borneo, have primarily relied on morphology-based identification, which has inherent biases and can be time-consuming. Next-Generation Sequencing (NGS) technology has been shown to be capable of overcoming several limitations of morphology-based methods. Samples were collected from the Sepanggar Bay over the course of the year 2018 in different monsoon seasons. Morphology-based identification and NGS sequencing of the V8–V9 region of the 18S LSU rDNA were used to investigate the diversity of the phytoplankton community. Microscopy and NGS showed complementary results with more diatom taxa detected by microscopy whereas NGS detected smaller and rarer taxa. The harmful algal genera in the study site comprised of Skeletonema, Margalefidinium, Pyrodinium, Takayama, and Alexandrium as detected by NGS. This study showed that that an integrative approach of both morphological and molecular techniques could provide more comprehensive information about the phytoplankton community as the approach captured quantitative variability as well as the diversity of phytoplankton species. 相似文献
200.
Philip J. Wallis Michael B. Ward Jamie Pittock Karen Hussey Howard Bamsey Amandine Denis Steven J. Kenway Carey W. King Shahbaz Mushtaq Monique L. Retamal Brian R. Spies 《Climatic change》2014,125(2):209-220
A variety of proposed activities to mitigate greenhouse gas emissions will impact on scarce water resources, which are coming under increasing pressure in many countries due to population growth and shifting weather patterns. However, the integrated analysis of water and carbon impacts has been given limited attention in greenhouse mitigation planning. In this Australian case study, we analyse a suite of 74 mitigation measures ranked as highest priority by one influential analysis, and we find that they have highly variable consequences for water quantity. We find: (1) The largest impacts result from land-based sequestration, which has the potential to intercept large quantities of water and reduce catchment yields, estimated to exceed 100 Mm3/MtCO2-e of carbon mitigated (100,000 l per tonne CO2-e). (2) Moderate impacts result from some renewable power options, including solar thermal power with a water cost estimated at nearly 4 Mm3/MtCO2-e. However, the water impacts of solar thermal power facilities could be reduced by designing them to use existing power-related water supplies or to use air or salt-water cooling. (3) Wind power, biogas, solar photovoltaics, energy efficiency and operational improvements to existing power sources can reduce water demand through offsetting the water used to cool thermal power generation, with minor savings estimated at 2 Mm3/MtCO2-e and amounting to nearly 100 Mm3 of water saved in Australia per annum in 2020. This integrated analysis significantly changes the attractiveness of some mitigation options, compared to the case where water impacts are not considered. 相似文献