全文获取类型
收费全文 | 1389篇 |
免费 | 49篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 60篇 |
大气科学 | 78篇 |
地球物理 | 304篇 |
地质学 | 597篇 |
海洋学 | 113篇 |
天文学 | 172篇 |
综合类 | 8篇 |
自然地理 | 115篇 |
出版年
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 20篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 47篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 69篇 |
2012年 | 58篇 |
2011年 | 68篇 |
2010年 | 72篇 |
2009年 | 92篇 |
2008年 | 64篇 |
2007年 | 58篇 |
2006年 | 60篇 |
2005年 | 71篇 |
2004年 | 56篇 |
2003年 | 58篇 |
2002年 | 36篇 |
2001年 | 34篇 |
2000年 | 24篇 |
1999年 | 20篇 |
1998年 | 20篇 |
1997年 | 17篇 |
1996年 | 24篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1970年 | 5篇 |
1969年 | 5篇 |
排序方式: 共有1447条查询结果,搜索用时 187 毫秒
491.
Roberto Bertoni Wade H. Jeffrey Mireille Pujo-Pay Louise Oriol Pascal Conan Fabien Joux 《Aquatic Sciences - Research Across Boundaries》2011,73(3):377-387
The scaling of the solar ultraviolet radiation (UVR, 280–400 nm) effect on phyto- and bacterio-plankton at the ecosystem level
is difficult since its estimate is often based on short-time incubation experiments performed at fixed depths, neglecting
the previous days’ radiation history and the variable radiation caused by vertical mixing. To examine this issue, we measured
primary (PP) and bacterial (BP) production in samples from coastal water in the Northwest Mediterranean Sea incubated at fixed
depths or moving vertically within the water column (0–8 m) with a periodicity of 22 min, exposed to full sun, PAR or maintained
in dark. Three experiments were carried out on consecutive days to measure day-to-day variations in planktonic response. In
surface waters, PP was inhibited by ~32 to 42% by UVR, and BP was inhibited by ~50 to 70% by solar radiation (UVR + PAR).
We observed a general decrease in the integrated inhibition of PP due to UVR for both fixed and moving incubations over the
3 days from ~27% of inhibition to non-significant inhibition. In contrast, large discrepancies were observed in the integrated
inhibition of BP due to solar radiation (UVR + PAR) between fixed and moving incubations. Whereas both type of incubations
gave similar estimation of solar radiation inhibition on day 1 (~25%), inhibition became much higher for fixed incubation
compared to moving incubation on days 2 and 3. Differences in responses between days suggest that light history, spectral
quality, photoadaptation or acclimation may be important factors in daily observed responses. Our results also underline,
for the first time, the importance of the vertical mixing in the BP inhibition by solar radiation. 相似文献
492.
Three intrusive systems of detection and quantification of coastal erosion events (using thermocouples and thermal pins) were developed and tested from 2005 to 2008 in different regions of the Gulf and maritime estuary of the St Lawrence (Quebec, Canada). The 3‐m‐long thermal pins inserted inside unconsolidated deposits allow the monitoring of erosion for a time period sometimes extending over several seasons. The thermocouple or thermocable method allows not only the instrumentation of unconsolidated deposits but also of rocky and cohesive substrate to a depth of 85 cm. An autonomous microclimatic station located near the experimental sites simultaneously samples temperature parameters, precipitation, snow cover, wind speed and direction as well as global radiation. The differential analysis of cliff thermal regime performed simultaneously with an analysis of air temperature makes it possible to determine the activation periods of coastal erosion processes. The results also make it possible to establish with precision the actual influence of rapid variations of certain climatic and microclimatic parameters (radiation, presence of snow cover, precipitation, etc.) on the physical state of surfaces and also on the activation of certain physical processes connected to coastal erosion events. The automated thermal erosion pin system (ATEPS) allows high temporal resolution (i.e. continuous) monitoring, enabling a real coupling of coastal erosion rates and climatic parameters. Preliminary results with the ATEPS system indicate that mild winter temperature and direct solar radiation are significant factors controlling cliff retreat rates. Moreover, the melting of segregation ice during the spring thaw contributed for more than 70% of cliff retreat against only 30% for frost shattering. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
493.
We have determined the liquid metal-liquid silicate partitioning of Ni, Co, Mo, W, V, Cr and Nb at 1.5 GPa/1923 K and 6 GPa/2123 K under conditions of constant silicate melt composition with variable amounts of Si in the Fe-rich metallic liquid. Partitioning of Ni, Co, Mo, W and V is sensitive to the Si content of the metal with, in all five cases, increasing Si tending to make the element more lithophile than for conditions where the metal is Si-free. In contrast, metal-silicate partitioning of Cr and Nb is, at constant silicate melt composition, insensitive to the Si content of the metal.The implications of our data are that if, as indicated by the Si isotopic composition of the silicate Earth (
[Georg et al., 2007] and [Fitoussi et al., 2009]), the core contains significant amounts of Si, the important siderophile elements Ni, Co, W and Mo were more lithophile during accretion and core formation than previously believed.We use our new data in conjunction with published metal-silicate partitioning results to develop a model of continuous accretion and core segregation taking explicit account of the partitioning of Si (this study) and O (from Ozawa et al., 2008) between metal and silicate and their effects on metal-silicate partitioning of siderophile elements. We find that the effect of Si on the siderophile characteristics of Ni, Co and W means that the pressures of core segregation estimated from these elements are ∼5 GPa lower than those derived from experiments in which the metal contained negligible Si (e.g., Wade and Wood, 2005). The core-mantle partitioning of Cr and Nb requires that most of Earth accretion took place under conditions which were much more reducing than those implied by the current FeO content of the mantle and that the oxidation took place late in the accretionary process. Paths of terrestrial accretion, oxidation state and partitioning which are consistent with the current mantle contents of Ni, Co, W, V, Cr and Nb lead to Si and O contents of the core of ∼4.3 wt.% and 0.15%, respectively. 相似文献
494.
495.
Vincent Busigny Pierre Cartigny Pascal Philippot 《Geochimica et cosmochimica acta》2011,75(23):7502-7521
Nitrogen contents and isotope compositions together with major and trace element concentrations were determined in a sequence of metagabbros from the western Alps (Europe) in order to constrain the evolution and behavior of N during hydrothermal alteration on the seafloor and progressive dehydration during subduction in a cold slab environment (8 °C/km). The rocks investigated include: (i) low-strain metagabbros that equilibrated under greenschist to amphibolite facies (Chenaillet Massif), blueschist facies (Queyras region) and eclogite facies (Monviso massif) conditions and (ii) highly-strained mylonites and associated eclogitic veins from the Monviso Massif. In all samples, nitrogen (2.6-55 ppm) occurs as bound ammonium () substituting for K or Na-Ca in minerals. Cu concentrations show a large variation, from 73.2 to 6.4 ppm, and are used as an index of hydrothermal alteration on the seafloor because of Cu fluid-mobility at relatively high temperature (>300 °C). In low-strain metagabbros, δ15N values of +0.8‰ to +8.1‰ are negatively correlated with Cu concentrations. Eclogitic mylonites and veins display Cu concentrations lower than 11 ppm and show a δ15N-Cu relationship that does not match the δ15N-Cu correlation found in low-strain rocks. This δ15N-Cu correlation preserved in low-strain rocks is best interpreted by leaching of Cu-N compounds, possibly of the form Cu(NH3)22+, during hydrothermal alteration. Recognition that the different types of low-strain metagabbros show the same δ15N-Cu correlation indicates that fluid release during subduction zone metamorphism did not modify the original N and Cu contents of the parent hydrothermally-altered metagabbros. In contrast, the low Cu content present in eclogitic veins and mylonites implies that ductile deformation and veining were accompanied either by a loss of copper or that externally-derived nitrogen was added to the system.We estimate the global annual flux of N subducted by metagabbros as 4.2 (±2.0) × 1011 g/yr. This value is about half that of sedimentary rocks, which suggests that gabbros carry a significant portion of the subducted nitrogen. The net budget between subducted N and that outgassed at volcanic arcs indicates that ∼80% of the subducted N is not recycled to the surface. On a global scale, the total amount of N buried to the mantle via subduction zones is estimated to be three times higher than that released from the mantle via mid-ocean ridges, arc and intraplate volcanoes and back-arc basins. This implies that N contained in Earth surface reservoirs, mainly in the atmosphere, is progressively transferred and sequestered into the mantle, with a net flux of ∼9.6 × 1011 g/yr. Assuming a constant flux of subducted N over the Earth’s history indicates that an amount equivalent to the present atmospheric N may have been sequestered into the silicate Earth over a period of 4 billion years. 相似文献
496.
Jeffery A. Thompson David W. Lamb Paul S. Frazier Bernard Ellem 《Environmental Earth Sciences》2011,62(5):973-984
This paper reports on the design and implementation of a program to monitor the surface effects of longwall mining-induced
subsidence on wine grape yields within vineyards of Australia’s Hunter Valley. Implemented in 2003, this five-year project
incorporated a multi-scale, multi-temporal, sliding window monitoring design synchronised with progression of longwall panels.
On the vineyard-block scale, individual vine panels were sampled for grape yield. On the regional scale measures of vine photosynthetically
active biomass were obtained from remotely sensed, Quickbird satellite imagery. All data were analysed in conjunction with
three identified subsidence “zones”: minimum subsidence associated with chain-pillars, maximum subsidence associated with
the longwall, and a zone corresponding to the transition between them. Visual observations conducted throughout the campaign
confirmed the occurrence of isolated localised surface cracking, particularly in areas of maximum soil tension. However, both
vineyard and block-scale data indicated no obvious, systematic mining-induced viticultural effects in the study site investigated
during the study period. Rather, observed trends in vine yields were better explained by vine biophysical responses to climatic
factors. 相似文献
497.
S��bastien Migeon Antonio Cattaneo Virginie Hassoun Christophe Larroque Nicola Corradi Francesco Fanucci Alexandre Dano Bernard Mercier de Lepinay Fran?oise Sage Christian Gorini 《Marine Geophysical Researches》2011,32(1-2):225-243
Based on new multibeam bathymetric data, seismic-reflection profiles and side-scan sonar images, a great number of submarine failures of various types and sizes was identified along the northern margin of the Ligurian Basin and characterized with 3 distinct end-members concerning their location on the margin, sedimentary processes and possible triggering mechanisms. They include superficial landslides mainly located in the vicinity of the main mountain-supplied rivers and on the inner walls of canyons (typically smaller that 108 m3 in volume: Type 1), deep scars 100?C500 m high along the base of the continental slope (Type 2), and large-scale scars and Mass Transport Deposits (MTDs) affecting the upper part of the slope (Type 3 failures). The MTDs are located in different environmental contexts of the margin, including the deep Var Sedimentary Ridge (VSR) and the upper part of the continental slope in the Gulf of Genova (Finale Slide and Portofino Slide), with volumes of missing sediment reaching up to 1.5 × 109 m3. High sedimentation rates related to hyperpycnal flows, faults and earthquake activity, together with sea-level fluctuations are the main factors invoked to explain the distribution and sizes of these different failure types. 相似文献
498.
499.
Recent advances on study of hadrosaurid dinosaurs in Heilongjiang(Amur) River area between China and Russia
下载免费PDF全文
![点击此处可从《世界地质(英文版)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pascal Godefroit Pascaline Lauters Jimmy Van Itterbeeck Yuri L. Bolotsky Ivan Y. Bolotsky 《世界地质(英文版)》2011,(3):160-191
Four main dinosaur-bearing sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation) ,Blagoveschensk and Kundur in Rus- sia (Udurchukan Formation) . More than 90% of the bones discovered in these localities belong to hollowcrested lambeosaurine hadrosaurids: Charonosaurus jiayinensis at Jiayin,Amurosaurus riabinini at Blagoveschensk, Olorotitan arharensis at Kundur,and Sahaliyania elunchunorum at Wulaga. Flat-headed hadrosaurine hadrosau- rids are much less numerous,but appear well diversified as well: Kerberosaurus manakini at Blagoveschensk, Wulagasaurus dongi at Wulaga,and a new genus at Kundur. Theropods are represented by shed teeth and isolated bones; isolated scutes and teeth discovered at Kundur are tentatively attributed to nodosaurids. Palynologi- cal studies suggest that these sites are probably synchronous with the Lancian’ vertebrate localities of western North America,which represent the youngest dinosaur faunas in this area. However,the latest Cretaceous dinosaur assemblages are completely different in the Amur/Heilongjiang region (lambeosaurines abundant,ceratopsids absent) and in western North America (ceratopsids abundant,lambeosaurines extremely rare or absent) . This probably reflects some kind of geographical barrier between both areas by Maastrichtian time rather than strong differences in palaeoecological conditions. 相似文献
500.
Gregor J. Golabek Bernard Bourdon Taras V. Gerya 《Meteoritics & planetary science》2014,49(6):1083-1099
The acapulcoite‐lodranite meteorites are members of the primitive achondrite class. The observation of partial melting and resulting partial removal of Fe‐FeS indicates that this meteorite group could be an important link between achondrite and iron meteorites, on the one hand, and chondrite meteorites, on the other. Thus, a better understanding of the thermomechanical evolution of the parent body of this meteorite group can help improve our understanding of the evolution of early planetesimals. Here, we use 2‐D and 3‐D finite‐difference numerical models to determine the formation time, initial radius of the parent body of the acapulcoite‐lodranite meteorites, and their formation depth inside the body by applying available geochronological, thermal, and textural constraints to our numerical data. Our results indicate that the best fit to the data can be obtained for a parent body with 25–65 km radius, which formed around 1.3 Ma after calcium‐aluminum‐rich inclusions. The 2‐D and 3‐D results considering various initial temperatures and the effect of porosity indicate possible formation depths of the acapulcoite‐lodranite meteorites of 9–19 and 14–25 km, respectively. Our data also suggest that other meteorite classes could form at different depths inside the same parent body, supporting recently proposed models (Elkins‐Tanton et al. 2011 ; Weiss and Elkins‐Tanton 2013 ). 相似文献