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881.
2008������Ms7.3����ǰ��������̬�仯������ 总被引:1,自引:1,他引:0
????1998?????????й??????????????????????????2008??3?????????7.3?????????????????????仯?????????????????????????????????????????????????????г????2~10???????????????????????????????????????????????????仯?????????????????????仯????????????????????????????????????????????????????????????????????????????????仯?????????????????????????????1976?????7.8????????????????????????й?????8?????????????仯??200??10 -8 ms -2 ?? 相似文献
882.
???????Envisat??????????????2004??7??12???2005??4??8?????????Ms6.7??Ms6.5?????InSAR????α??????????????ε????????????20 km??20 km??Χ???EW?????????Σ??????η???19.0 cm??30.5 cm???????????????????????????ε???????????????????????,????λ??83.71??E,30.70??N,??Mw6.1,83.72??,E30.52??N????Mw6.2??????????????? 1 m??1.4 m?????ε??????????NW?????3?????????????NS?????????-????????????λ 相似文献
883.
The longitudinal dispersion coefficient (D) is an important parameter needed to describe the transport of solutes in rivers and streams. The dispersion coefficient is generally estimated from tracer studies but the method can be expensive and time consuming, especially for large rivers. A number of empirical relations are available to estimate the dispersion coefficient; however, these relations are known to produce estimates within an order of magnitude of the tracer value. The focus of this paper is on using the shear-flow dispersion theory to directly estimate the dispersion coefficient from velocity measurements obtained using an Acoustic Doppler Current Profiler (ADCP). Using tracer and hydrodynamic data collected within the same river reaches, we examined conditions under which the ADCP and tracer methods produced similar results. Since dead zones / transient storage (TS) are known to influence the dispersion coefficient, we assessed the relative importance of dead zones in different stream reaches using two tracer-based approaches: (1) TS modeling which explicitly accounts for dead zones and (2) the advection–dispersion equation (ADE) which does not have separate terms for dead zones. Dispersion coefficients based on the ADE tend to be relatively high as they describe some of the effects of dead zones as well. Results based on the ADCP method were found to be in good agreement with the ADE estimates indicating that storage zones play an important role in the estimated dispersion coefficients, especially at high flows. For the river sites examined in this paper, the tracer estimates of dispersion were close to the median values of the ADCP estimates obtained from multiple datasets within a reach. The ADCP method appears to be an excellent alternative to the traditional tracer-based method if care is taken to avoid spurious data and multiple datasets are used to compute a distance-weighted average or other appropriate measure that represents reach-averaged conditions. 相似文献
884.
885.
Yao Daquan Shuo Zhi Shen Xiaoqi Chen Anguo Zheng Yingping Zheng Haigang Li Lingli 《中国地震研究》2010,24(3):363-370
During an excavation survey to the Daijiayuan vestige of the Western Zhou Dynasty-Late Spring and Autumn Period at Huoshan in Western Anhui,a ground crack related to tectonic movement and filled with silty fine sand was found. This phenomenon was initially confirmed to be due to seismic liquefaction. Many microscopic seismic relics,such as load structure,flow structure,cutoff plane and flotation of organic matter were found in the directional microscopic analysis of deformation. These discoveries and cognitions prove that there were two earthquake events taking place in the Western Zhou Dynasty-Late Spring and Autumn Period in this area. Above-mentioned works enrich and develop the research methods to identify prehistoric earthquake event in eastern China area to a certain extent. 相似文献
886.
用统计学上的χ~2检验方法对华东地区M_L≥4.0地震平静进行了统计检验,得出在较高的置信概率下可以将平静时间T≥140天作为平静异常的判别标准。总结了华东地区自1970年以来出现的平静异常,并分析了其对应中强地震的情况。研究表明,M_L≥4.0地震平静异常是华东地区中强震前的一种普遍现象。62.5%的平静异常后发生了M_S≥4.5地震;绝大多数平静异常前存在着地震活动的增强过程,多次活动增强后连续发生了平静异常且之后发生了M_S≥5.0地震。 相似文献
887.
Shipboard X-band radar images acquired on 24 June 2009 are used to study nonlinear internal wave characteristics in the northeastern
South China Sea. The studied images show three nonlinear internal waves in a packet. A method based on the Radon Transform
technique is introduced to calculate internal wave parameters such as the direction of propagation and internal wave velocity
from backscatter images. Assuming that the ocean is a two-layer finite depth system, we can derive the mixed-layer depth by
applying the internal wave velocity to the mixed-layer depth formula. Results show reasonably good agreement with in-situ
thermistor chain and conductivity-temperature-depth data sets. 相似文献
888.
LIAN Yi WANG Jie TU Gang REN Hongling SHEN Baizhu ZHI Keguang LI Shangfeng GAO Zongting 《中国地理科学(英文版)》2010,20(1):91-97
Interdecadal and interannual variations of saline-alkali land area in Qian’an County, Jilin Province, China were comprehensively
analyzed in this paper by means of satellite remote sensing interpretation, field flux observations and regional climate diagnosis.
The results show that on the interannual scale, the impact of climate factors accounts for 71.6% of the total variation of
the saline-alkali land area, and that of human activities accounts for 28.4%. Therefore the impact of climate factors is obviously
greater than that of human activities. On the interdecadal scale, the impact of climate factors on the increase of the saline-alkali
land area accounts for 43.2%, and that of human activities accounts for 56.8%. The impact of human activities on the variation
of saline-alkali land area is very clear on the interdecadal scale, and the negative impact of human activities on the environment
should not be negligible. Besides, changes in the area of heavy saline-alkali land have some indication for development of
saline-alkali land in Qian’an County. 相似文献
889.
Jige Shen Mazda Biglari ChangBo Jiang HongHai Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(8):1089-1096
As radioactive human doses are calculated through food chain and exposure pathways, it is important to take a pathway analysis
to determine all pathway contributions for further radiological environmental risk assessment. A challenge of contaminant
fate and environmental pathway analysis is to handle a large number of environmental components and to assign proper calculation
models to linked component pairs. This paper presents a model template called transfer pathway model template (TPMT) that
stores transfer models to environmental class pairs. When a site-specific calculation scenario is built, a source–receptor
transfer matrix (SRTM) is defined by the scenario. Then the calculation loops through all source–receptor component pairs
in SRTM and apply proper models stored in TPMT to calculate the transfer factors. TPMT can be used as the component pathway
verification template and model allocation template. This structure is used in an environmental risk assessment (ERA) application
called IMPACT that has been applied for a number of nuclear power plants and uranium mines in Canada. 相似文献
890.
The effectiveness of simulating surge inundation using the Eulerian–Lagrangian circulation (ELCIRC) model over multi-scale
unstructured grids was examined in this study. The large domain model grid encompasses the western North Atlantic Ocean, the
Gulf of Mexico, and the Caribbean Sea to appropriately account for remote and resonance effects during hurricane events and
simplify the specification of the open boundary condition. The U.S. East and Gulf Coasts were divided into 12 overlapping
basins with fine-resolution (up to 30 × 30 m) grids to model overland surge flooding. These overlapping basins have different
fine-resolution grids near the coastal region, but have an identical coarse-resolution grid in the offshore region within
the large model domain. Thus, the storm surge prediction can be conducted without reducing computation efficiency by executing
multiple model runs with local fine-resolution grids where potential hurricane landfalls may occur. The capability of the
multi-scale approach was examined by simulating storm surge caused by Hurricanes Andrew (1992) and Isabel (2003) along the
South Florida coast and in the Chesapeake Bay. Comparisons between simulated and observed results suggest that multi-scale
models proficiently simulated storm surges in the Biscayne Bay and the Chesapeake Bay during two hurricanes. A series of sensitivity
tests demonstrated that the simulation of surge flooding was improved when LiDAR topographic data and special bottom drag
coefficient values for mangrove forests were employed. The tests also showed that appropriate representation of linear hydrologic
features is important for computing surge inundation in an urban area. 相似文献