全文获取类型
收费全文 | 355篇 |
免费 | 12篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 47篇 |
地球物理 | 124篇 |
地质学 | 130篇 |
海洋学 | 50篇 |
天文学 | 7篇 |
综合类 | 3篇 |
自然地理 | 14篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 16篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 20篇 |
2013年 | 29篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 23篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有377条查询结果,搜索用时 31 毫秒
111.
112.
A total of 29 vertical Ra profiles has been measured from the Pacific as part of the GEOSECS program. These profiles are located on an east-west section along ~30°N, and a north-south section, close to the western boundary of the major basins in the western Pacific. Profiles from the northeast Pacific show a deep Ra maximum, with an excess concentration relative to the potential temperature and salinity. This maximum extends westward in the direction with decreasing Ra content, and finally vanishes completely in the northwest Pacific near Japan.Ra profiles along the western boundary show a mid-depth maximum around 3 km and a near-bottom minimum due to southward intrusion of the high-Ra Pacific Deep Water and a northward spreading of the low-Ra Antarctic Bottom Water. The contrast between the maximum and the minimum intensifies toward the south, where the benthic front has clearly separated these two water masses. Ra is thus a useful tracer for the studies of oceanic mixing and circulation in the Pacific. 相似文献
113.
Profiles of226Ra and dissolved210Pb have been measured at several stations in the Red Sea. At one station in the central Red Sea an expanded profile was measured including226Ra and dissolved and particulate210Pb and210Po. These profiles show several distinct features: (1)226Ra displays a mid-depth maximum of about 13 dpm/100 kg at about 500 m; (2) dissolved210Pb concentrations are uniformly low at about 2 dpm/100 kg with little lateral or vertical variation; (3) the surface-water210Pb excess which is commonly observed in low-latitude open ocean regions is entirely lacking; (4)210Pb and210Po activities are essentially identical to each other in both particulate and dissolved phases although210Po activities appear somewhat lower; (5) about 20% of the210Pb and210Po in the water column residues on particulate matter.Assuming the atmospheric210Pb flux to be in the dissolved form and at the lower level of the normal range i.e. 0.5 dpm/cm2 yr, the residence time of the dissolved Pb is about 1.5 years. However, if the same atmospheric flux is entirely in particulate form, then the residence time of the dissolved Pb is about 5 years. The residence time of Pb in the particulate phase is less than 0.4 years if all the Pb is removed only by sinking particles. 相似文献
114.
115.
This article describes a methodology to localise areas with high potential towards natural snowpack instability under particular meteorological conditions, at the scale of an Alpine valley. Localisation is based on statistically relating known release areas of past avalanche events to maps of: (1) slope inclination, (2) slope orientation (aspect), (3) elevation, (4) distance from crest lines, (5) terrain roughness and (6) concavities/convexities. The maps have been built using two different GIS softwares while the statistical analyses have been performed with a specific software handling also Fuzzy Set theory algorithms. The results of the statistical analyses have been verified on test release—areas which have not been used as input data for the statistical analyses. Verification allowed to quantify how reliably the susceptibility values were calculated, to compare the values obtained using different combinations of terrain features and to finally decide on the most efficient combination. The susceptibility maps were calculated and verified for three different meteorological scenarios (given by three classes of snow depth). Verification has shown that the accuracy of the susceptibility maps was between 67% and 82%. The three susceptibility maps show a remarkable difference in the spatial pattern of the highest susceptibility pixels suggesting that for different meteorological scenarios different classes of terrain features need to be considered.The possibility to make combinations of terrain features and to assess and verify their statistical relationship with release areas of past avalanche events is the major original step made by STARTER. Linking those release areas to meteorological scenarios is an attempt to include in the analysis the combined influence of terrain features and meteorological conditions towards snowpack instability. 相似文献
116.
Two ungrouted post‐tensioned, precast concrete‐filled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal‐height circular CFT segments, and a footing. Strands were placed through the column and post‐tensioned to provide a precompression of the column against the footing. One specimen also contained energy‐dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy‐dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the segmental column. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
117.
Jinwon Kim Norman L. Miller Jai-Ho Oh Jun-Seok Chung Deukkyun Rha 《Global and Planetary Change》1998,19(1-4)
We present the hydrometeorology of eastern Asia during April 1995 simulated by the Regional Climate System Model. The amount and location of simulated monthly precipitation agrees well with observations. Soil water content variation was closely correlated with precipitation. Land-surface evaporation and the surface energy budget were strongly controlled by soil moisture content. A sensitivity test with reduced initial soil moisture content suggested that near-surface soil moisture spins up quickly after heavy precipitation events. However, variations in the initial soil moisture field may alter details of the simulated precipitation which can introduce further complexity in climate simulations. 相似文献
118.
Dong-Jin Kang Chang Soo Chung Suk Hyun Kim Kyung-Ryul Kim Gi Hoon Hong 《Marine pollution bulletin》1997,35(7-12):305-312
Surface and subsurface water samples for 137Cs and 239,240Pu analysis were collected in the East Sea (Sea of Japan) during August 1993. The 137Cs levels of the surface waters are quite homogeneous in the East Sea (average = 3.1±0.2 mBq kg−1). The 239,240Pu levels vary from 6 to 10 μBq kg−1 in the surface. 239,240Pu to 137Cs ratios in the surface water are within 0.002 to 0.003. The East Sea may be regarded as a part of the North Pacific Ocean in terms of 137Cs dispersal in the surface, where the 137Cs contents of the surface seawater seem to be controlled primarily by the atmospheric input. However, since our sampling was made just two months prior to the widely publicized Russian dumping incident on the 17th October 1993, our measurements may provide background data to assess the immediate impact of the Russian dumping on the levels of 137Cs and 239,240Pu in the East Sea. 相似文献
119.
Y. S. Chung 《Journal of Atmospheric Chemistry》1989,9(1-3):317-330
A meteorological analysis is presented for environmental data set obtained from the Canadian Arctic haze study, which is part of AGASP-II. Results of the study indicated that atmospheric carbon dioxide (CO2), methane (CH4), sulphate (SO4
=), ozone (O3) and other air pollutants observed at Alert, N.W.T. underwent periodical fluctuations. It was found that high concentrations of these atmospheric constituents were associated with a deep (1430–2074 m) inversion and with a major anticyclone. In contrast, relatively low values of these constituents were associated with a cyclonic disturbance near Alert. High concentrations of these constituents occurred with air trajectories coming from the N-W direction, while low values occurred with S trajectories. In addition, examinations of satellite imagery with other meteorological data suggested that volcanic inputs of ash and gases from Augustine Island, Alaska were negligible for the observed high values of these constituents at the ground level at Alert. 相似文献
120.
The geostatistical approach was applied to integrate MT (Magneto-telluric) resistivity data and borehole information for the spatial RMR (Rock Mass Rating) evaluation. Generally, resistivity of the subsurface is believed to be positively related to the RMR, thus the resistivity and borehole RMR information was combined in a geostatistical approach. To relate the two different sets of data, the MT resistivity data were used as secondary information and the RMR mean values were estimated at unsampled points by identification of the resistivity to the borehole data. Two types of approach are performed for the estimation of RMR mean values. Then the residuals of the RMR values around the borehole sites are geostatistically modeled to infer the spatial structure of difference between real RMR values and estimated mean values. Finally, this geostatistical estimation is added to the previous means. The result applied to a real situation shows prominent improvements to reflect the subsurface structure and spatial resolution of RMR information. 相似文献