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911.
Evaluating relationships between soil chemical properties and vegetation cover at different slope aspects in a reclaimed dump 总被引:1,自引:0,他引:1
Xiaoyang Liu Yingui Cao Zhongke Bai Jinman Wang Wei Zhou 《Environmental Earth Sciences》2017,76(23):805
Conducting research about the relationships between soil chemical properties and vegetation coverage at different slope aspects is especially important in reconstructed ecosystems of vulnerable ecological regions. This study was conducted in the first reclaimed dump within the Pingshuo mining area of Shanxi Province, China, to analyze patterns of soil chemical properties (soil organic matter (SOM), soil total nitrogen (STN), soil available phosphorus (SAP) and soil available potassium (SAp) and vegetation coverage (NDVI) and their correlations at different slope aspects. In the reclaimed dump, 26 quadrats were established along four slope aspects (i.e., shady, semi-shady, sunny and semi-sunny slopes). There was no significant difference in SOM or STN among different slope aspects, while SAP differed between shady slopes compared to semi-shady, sunny and semi-sunny slopes; SAP differed significantly between semi-shady and semi-sunny slopes. The NDVI of semi-sunny slopes differed significantly from that of the other three aspects. There was variation in the relationships between NDVI and soil chemical properties, depending on the slope aspects. The logarithm of SOM and NDVI was related linearly on shady and semi-shady slopes, while NDVI was inversely related to the natural logarithm of the logarithm of SOM on sunny and semi-sunny slopes. STN and NDVI had a first-order function relationship on shady and semi-shady slopes, yet a quadratic function relationship on sunny and semi-sunny slopes. The relationships between SAP and NDVI were inverse on all types of slopes. On shady and semi-shady slopes, NDVI had a quadratic relationship with the logarithm of SAp, but it was well fitted by using a cubic function on sunny and semi-sunny slopes. The sensitivity coefficients of soil chemical properties and NDVI were different, and soil chemical properties changed differently depending on changes in NDVI at different slope aspects. 相似文献
912.
高岭石与碱剂作用后反应液中硅铝元素变化规律研究 总被引:1,自引:2,他引:1
本文系统地研究了高岭石与碱剂间的作用对反应后的液相参数进行全面测定,以查清温度,反应时间,碱性驱替剂的种类浓度等因素与液相参数和固相参数的关系。提出高岭石的非一致性溶蚀趋势,并探讨高岭石与碱性驱替剂的作用机理,丰富了化学驱油过程中化学剂与矿物作用方面的基础理论。 相似文献
913.
Quartz–amphibole–pyroxene gneiss from the island of Akilia, Southwest Greenland has been claimed to contain the earliest traces
of life on Earth in the form of biogenic carbonaceous matter encapsulated as inclusions in apatite crystals. Various lines
of evidence, including petrography, geochronology, field relations, and geochemistry, have, however, been presented that challenge
this interpretation. Textural relationships and geochemical signatures in this controversial gneiss presented here manifest
a complex, spatially variable metamorphic history that includes granulite- and amphibolite-facies overprints and metasomatism.
A peak metamorphic, granulite-facies, quartz–orthopyroxene–clinopyroxene–amphibole–magnetite assemblage is preserved in only
a few centimeter-scale layers within the 5-m-thick, quartz–amphibole–pyroxene gneiss unit. Calcite veinlets that appear to
postdate the peak metamorphism occur in pyroxene. The quartz–amphibole–pyroxene gneiss unit has subsequently experienced isochemical
(except hydration) amphibolite-facies alteration during which pyroxenes were retrogressed to amphiboles and magnetite, and
calcite was consumed. Parts of the quartz–amphibole–pyroxene gneiss that contain texturally late hornblende have experienced
metasomatic alteration by Al-carrying fluids. These fluids controlled the alteration of pyroxenes and amphiboles to hornblende,
and modified the trace-element composition by remobilizing LREE and Eu. Apatite has variable REE composition and 87Sr/86Sr in the quartz–amphibole–pyroxene gneiss, but on the local scale (cm) is in equilibrium with co-existing silicates. Effective
recrystallization of apatite crystals as well as co-existing silicates during several stages of the metamorphic history makes
the intact preservation of diagenetic apatite with encapsulated primary carbonaceous matter implausible. Hence, it is highly
unlikely that Akilia apatite could serve as repository of the earliest traces of life on Earth. 相似文献
914.
Kita-Uebaru natural rock slope failure and its back analysis 总被引:1,自引:2,他引:1
A large landslide occurred in Kita-Uebaru (or Asato) area of Nakagusuku village in Okinawa Island (Japan) on 10 June 2006
after a rainy period of about 9 days. The total rainfall was 126 mm from June 8 till the time of the landslide this period.
This landslide destroyed several buildings and roads, and the total travel distance of the landslide was about 110 m. In this
article, the authors were concerned with the initiation conditions of Kita-Uebaru landslide and post-failure motions of the
landslide body. The observations made in the landslide area, structural geology analyses and outcomes of geotechnical investigations
are described first. Then, possible causes of the landslide are investigated through back analyses using as inputs the geological
structure and the strength properties of planes of discontinuities involved in the sliding processes. The final part of the
article is concerned with the simulation of post-failure motions of the landslide body. The results of the investigations
and back analyses indicate that the failure plane was bi-planar and the heavy torrential rainy period for about 3 days was
the main cause of initiation of the landslide. The mechanical model presented in this article was capable of capturing the
overall features of the landslide body following the initiation of the failure. 相似文献
915.
Groundwater recharge in arid areas induced by tropical cyclones: lessons learned from Gonu 2007 in Sultanate of Oman 总被引:3,自引:1,他引:3
Younger groundwater found in some Omani aquifers is a result of recent recharge from cyclonic and storm events [Weyhenmeyer
et al. (Science 287:842–845, 2000); Young et al. (J Appl Geophys 57:43–61, 2004)]. The analysis of the meteorological data in Oman indicates an anomalous rainfall on a decadal interval whereas cyclones
frequency is expected to increase due to global climatic changes. The cyclone Gonu has severely struck the eastern Omani coasts
in 2007 resulting in devastating floods. Huge volume of water (3,672 mm3) spread over the coastal plain calling for an assessment of potential groundwater recharge subsequent to this event. The
present study evaluates groundwater recharge with respect to Gonu 2007 to assess the potential of recharge induced by such
cyclones in the arid zones. The hydrographs of several piezometers sited along the coastal plain in Muscat Province have been
studied and variation in water table rise has been analyzed. Significant water table rise is indicated for areas with geological
and structural settings favoring rapid infiltration of water yielding considerable groundwater mound, whereas piezometers
located in less favorable zones show minimum rise of water table. However, soon after the floods the aquifer hydrodynamics
has readjusted to attain equilibrium and the groundwater mound dissipated. The cumulative rise of the water table on an areal
extent does not exceed a few centimeters indicating lesser volume of recharge. Comparatively, recharge from frequent precipitation
along favorable zones produces more significant recharge compared with cyclonic events where surface water residence time
is shorter to allow for efficient infiltration. 相似文献
916.
Heinz-Günter Stosch Rolf L. Romer Farahnaz Daliran Dieter Rhede 《Mineralium Deposita》2011,46(1):9-21
Iron oxide–apatite (IOA) deposits, often referred to as Kiruna-type iron ore deposits, are known to have formed from the Proterozoic
to the Tertiary. They are commonly associated with calc–alkaline volcanic rocks and regional- to deposit-scale metasomatic
alteration. In the Bafq District in east Central Iran, economic iron oxide–apatite deposits occur within felsic volcanic tuffs
and volcanosedimentary sequences of Early Cambrian age. In order to constrain the age of formation of these ores and their
relationship with the Early Cambrian magmatic event, we have determined the U–Pb apatite age for five occurrences in the Bafq
District. In a 206Pb/238U vs. 207Pb/235U diagram, apatite free of or poor in inclusions of other minerals plots along the Concordia between 539 and 527 Ma with four
out of five samples from one deposit clustering at the upper end of this range. For this deposit, we interpret this cluster
to represent the age of apatite formation, whereas the spread towards younger ages may reflect either minor Pb loss or several
events of IOA formation. Apatite with inclusions of monazite (±xenotime) yields disturbed systems with inclusions having developed
after formation of the iron ore–apatite deposits, possibly as late as 130–140 Ma ago. Obtained apatite ages confirms that
(IOA) and the apatite-rich rocks (apatites) of the Bafq district formed coevally with the Early Cambrian magmatic (-metasomatic)
events. 相似文献
917.
Distribution of heavy metals in soils of Port Harcourt and its environs,Niger Delta,Nigeria 总被引:1,自引:0,他引:1
Geochemical evaluation of the distribution of heavy metals in soils of Port Harcourt and its environs in the Niger Delta region is presented in respect of anthropogenic factor and index of geoaccumulation. Sixteen (16) soil samples were collected from two horizons (0-10 cm and 100 cm) from the various grids and analyzed. The geo-chemical analyses showed the vertical and horizontal distributions of heavy metals. The results showed the ranges of the metals determined as follows: Pb (6.86-2.49)×10-6, with an average of 4.63×10-6; Cd (0.05-0.00)×10-6, with an average of 0.02×10-6, As (0.01-0.00)×10-6, with an average of 0.00×10-6. Cu (15.36-10.80) ×10-6, with an average of 13.36×10-6, and V (1.36-0.20)×10-6, with an average of 0.94×10-6. Quantification of the degree of pollution was carried out using anthropogenic factor (AF) and index of geoaccumulation (Igeo). The Igeo values of 0.06, 0.02 and 0.00 for Pb, Cd and As, respectively indicate low-level contamination while Zn (1.14) and V (1.40) show me-dium-level contamination. The sources of contamination are attributed to urbanized anthropogenic activities. The majority of the samples analyzed show that the AF values are less than 1 with the exception of vanadium (V) whose AF values range from 2.73 to 13.60×10-6. Vanadium is more enriched than As, Cd, Pb, and Cu. The order of degrees of anthropogenic contamination and index of geoaccumulation in the soil is V >Zn >Pb >Cu >Cd >AS. Metals were retained near the top soil and their concentrations in the deepest horizons were lower and normal for uncontaminated soils. Metal concentrations in the top soil horizons were significantly related to distance from the industrial and hu-man activities. 相似文献
918.
A continuous/discontinuous Galerkin framework for modeling coupled subsurface and surface water flow
Clint Dawson 《Computational Geosciences》2008,12(4):451-472
We consider conjunctive surface-subsurface flow modeling, where surface water flow is described by the shallow water equations
and ground water flow by Richards’ equation for the vadose zone. Coupling between the models is based on the continuity of
flux and water pressure. Numerical approximation of the coupled model using the framework of discontinuous Galerkin (DG) methods
is formulated. In the subsurface, the local discontinuous Galerkin (LDG) method is used to approximate ground water velocity
and hydraulic head; a DG method is also used to approximate surface water velocity and elevation. This approach allows for
a weak coupling of the models and the use of different approximating spaces and/or meshes within each regime. A simplified
LDG method based on continuous approximations to water head is also described. Numerical results that investigate physical
and numerical aspects of surface–subsurface flow modeling are presented.
This work was supported by National Science Foundation grant DMS-0411413. 相似文献
919.
Many Gulf of Mexico estuaries have low ratios of water volume to bottom surface area, and benthic processes in these systems
likely have a major influence on system structure and function. The purpose of this study was to determine the spatiotemporal
distribution of biomass and community composition of subtidal benthic microalgal (BMA) communities in Galveston Bay, TX, USA,
compare BMA community composition and biomass to phytoplankton in overlying waters, and estimate the potential contribution
of BMA to the trophodynamics in this shallow, turbid, subtropical estuary. The estimates of BMA biomass (mean = 4.21 mg Chl
a m−2) for Galveston Bay were within the range of the reported values for similar Gulf of Mexico estuaries. BMA biomass in the
central part of the bay was essentially homogeneous, whereas biomass at the seaward and upper bay ends of the transect were
significantly lower. Peridinin, fucoxanthin, and alloxanthin were the three carotenoids with the highest concentrations, with
fucoxanthin having the highest mean concentration (1.82 mg m−2). The seaward and landward ends of the transect differed from the central region of the bay with respect to the relative
abundances of chlorophytes, cyanobacteria, and photosynthetic bacteria. Benthic microalgal community composition also showed
a gradual shift over time due to changes in the relative abundances of photosynthetic bacteria, cryptophytes, dinoflagellates,
and cyanobacteria. Major changes in community composition occurred in the spring months (March to April). On an areal basis,
BMA biomass in Galveston Bay occurred at minor concentrations (16.5%) relative to phytoplankton. Furthermore, the concentrations
of carotenoid pigments for phytoplankton and BMA (fucoxanthin, alloxanthin, and zeaxanthin) were correlated (r = 0.48 to 0.61), suggesting a close linkage between microalgae in the water column and sediments. The contribution of BMA
to the primary productivity of the deeper waters (>2 m) of Galveston Bay is probably very small in comparison to shallower
waters along the bay margins. The significant similarities in the community composition of phytoplankton and BMA illustrate
the potential importance of deposition and resuspension processes in this turbid, shallow estuary. 相似文献
920.