全文获取类型
收费全文 | 69881篇 |
免费 | 1433篇 |
国内免费 | 677篇 |
专业分类
测绘学 | 1902篇 |
大气科学 | 5099篇 |
地球物理 | 14157篇 |
地质学 | 24909篇 |
海洋学 | 6227篇 |
天文学 | 16101篇 |
综合类 | 197篇 |
自然地理 | 3399篇 |
出版年
2022年 | 457篇 |
2021年 | 791篇 |
2020年 | 913篇 |
2019年 | 976篇 |
2018年 | 2095篇 |
2017年 | 1981篇 |
2016年 | 2387篇 |
2015年 | 1352篇 |
2014年 | 2206篇 |
2013年 | 3803篇 |
2012年 | 2449篇 |
2011年 | 3030篇 |
2010年 | 2748篇 |
2009年 | 3479篇 |
2008年 | 2992篇 |
2007年 | 3034篇 |
2006年 | 2832篇 |
2005年 | 1982篇 |
2004年 | 1972篇 |
2003年 | 1819篇 |
2002年 | 1857篇 |
2001年 | 1642篇 |
2000年 | 1520篇 |
1999年 | 1313篇 |
1998年 | 1315篇 |
1997年 | 1296篇 |
1996年 | 1070篇 |
1995年 | 1018篇 |
1994年 | 967篇 |
1993年 | 809篇 |
1992年 | 737篇 |
1991年 | 731篇 |
1990年 | 782篇 |
1989年 | 688篇 |
1988年 | 628篇 |
1987年 | 754篇 |
1986年 | 657篇 |
1985年 | 830篇 |
1984年 | 923篇 |
1983年 | 807篇 |
1982年 | 805篇 |
1981年 | 704篇 |
1980年 | 660篇 |
1979年 | 620篇 |
1978年 | 628篇 |
1977年 | 543篇 |
1976年 | 498篇 |
1975年 | 507篇 |
1974年 | 487篇 |
1973年 | 520篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
D. Evans M.S. Stoker P.M. Shannon STRATAGEM Partners 《Marine and Petroleum Geology》2005,22(9-10):969
The EC-funded STRATAGEM project ran from 2000 to 2003 and was a study of the Neogene evolution of the glaciated northeast Atlantic margin from Lofoten to Porcupine, an area extending over nearly 20 degrees of latitude. An extensive seismic, borehole and sample database has been used, much of it supplied by the oil industry. The main products of STRATAGEM have been an integrated, unified stratigraphic framework in the form of an atlas documenting and illustrating the detailed stratigraphy of the entire margin, and a detailed evolution model for this margin. A brief summary of the background to, and organisation of, the project is presented, together with an outline of the main objectives, the physiographic setting of the area and the database. 相似文献
992.
In the present study, a methodology for reliability assessment of slack and taut mooring systems against instability has been presented. For this purpose, first, stability analysis of slack and taut mooring systems has been carried out and instable regions are obtained using procedure available in the literature. Having known the instable region(s), methodology for reliability assessment has been proposed which is based on Monte Carlo Simulation technique. After using the proposed methodology, probabilities of failure and reliability indices has been obtained for the above systems. Some parametric studies, such as, effect of lower and upper limits of instability and effect of frequency range of generations are also included to obtain the results of practical interest. 相似文献
993.
Diet restriction induced autophagy: a lysosomal protective system against oxidative- and pollutant-stress and cell injury 总被引:1,自引:0,他引:1
Moore MN 《Marine environmental research》2004,58(2-5):603-607
Nutrient deprivation or dietary restriction (DR) confers protection against ageing and stress in many animals and induced lysosomal autophagy is part of this mechanism. The effects of dietary restriction on the toxicity of copper and the polycyclic aromatic hydrocarbon phenanthrene have been investigated in the common marine mussel Mytilus edulis. The findings show that DR-induced autophagy facilitates the recovery of the digestive gland (i.e., molluscan liver analogue) from cell injury caused by both copper and phenanthrene. It is inferred that DR-induced autophagy and lysosomal proteolysis results in improved cellular "housekeeping" through the more efficient removal of oxidatively and pollutant damaged proteins (e.g., protein carbonyls, protein adducts, etc.) and that this contributes to stress resistance. 相似文献
994.
The use of lysosomal stability in the mussel, Mytilus galloprovincialis, as a potential biomarker of environmental contamination has been evaluated along the Portuguese coast. To this end, the neutral red retention (NRR) time was measured in mussel haemocytes gathered from nine different locations reflecting different degrees of anthropogenic contamination. Mussels collected in the vicinity of industrial and urban areas showed the lowest lysosomal stability. Additionally, no significant seasonal variability (winter-spring/summer) for NRR time was observed. In order to further support the usefulness of this method as an integrated tool for monitoring marine coastal environments, we compared the levels of xenobiotics in mussel tissues with the obtained NRR values. The results highlighted a consistent pattern, with the lowest lysosomal stability intimately correlated with the higher contaminant concentrations. In summary, this integrated approach further demonstrated that the NRR assay can provide useful and objective indications of the real health status of organisms subjected to different stress agents, being a valid option for environmental monitoring. 相似文献
995.
Ivanov V. A. Kubryakov A. I. Lyubartseva S. P. Mikhailova É. N. Shapiro N. B. 《Physical Oceanography》2004,14(2):67-83
In the present work, we generalize the results of our investigations in the field of simulation of hydrophysical and ecological processes in coastal regions of various seas and some closed basins. The developed and applied mathematical models and the results of numerical experiments are briefly analyzed. 相似文献
996.
J. Acosta E. Uchupi A. Muñoz P. Herranz C. Palomo M. Ballesteros 《Marine Geophysical Researches》2003,24(1-2):41-57
Circular to elliptical mounds in the Canary Channel with reliefs of 75 to 375 m and diameters of 4 to 8 km partially surrounded by moats with reliefs of 25 to 75 m, were formed by piercement of the seafloor by Mesozoic evaporites. Several long gullies, < 1km wide, with abrupt terminations and pockmarks associated with these mounds were probably eroded by dense brine and hydrocarbon seeps. The salt brines that eroded the gullies were formed where salt diapirs intersect the seafloor, or in the subsurface by circulating ground water heated by igneous activity along the Canary Ridge. If the brines originated in the subsurface they reached the seafloor along faults. Displacement of the surficial sediments by sliding and creep is probably the result of the expulsion of hydrocarbons and/or vertical motion of the Mesozoic evaporites. Microtopographic features along or near the east flank of the Canary Ridge are the creation of uplift of the ridge, hydrothermal activity, mass wasting processes and turbidity currents. 相似文献
997.
A survey of imposex in Thais orbita (Neogastropoda) along the New South Wales (NSW) coast, Australia, found imposex was still widespread 10 years after a partial ban on tributyltin (TBT) based antifouling paints. Transplant experiments also revealed that imposex was induced in T. orbita over a period of 9 weeks in Sydney Harbour, NSW. A comparison of the imposex data with that collected shortly after the introduction of restrictions on TBT revealed a general decline in imposex frequency occurring at open coast sites, an exception being the site at South West Rocks. Sites located within harbour/bay areas did not display a decline in imposex frequency but a decline in the severity of imposex was apparent. The observed decrease in imposex values in T. orbita may reflect a general decrease of butyltin contamination within the coastal environment. However, the persistence of contamination "hotspots" within harbours and bays remains a concern. 相似文献
998.
999.
There is a growing body of evidence to suggest that certain polycyclic aromatic hydrocarbons (PAHs) pose a greater hazard to aquatic organisms than previously demonstrated, due to their potential to cause photo-induced toxicity when exposed to ultraviolet (UV) radiation. The consequences of photo-induced toxicity are reported here for embryo-larval stages of the pacific oyster Crassostrea gigas, following exposure to pyrene and benzo[a]pyrene. During laboratory investigations, significant increases in toxicity were observed in the presence of environmentally attainable levels of UV-radiation, compared with embryos exposed to PAH alone, at levels previously deemed to have little acute biological effect. The phototoxicity of pyrene and benzo[a]pyrene completely inhibited the development to the D-shell larval stage when embryos were simultaneously exposed to 5 microg l(-1) PAH and ultraviolet light (UVB = 6.3 +/- 0.1 microW/cm2 and UVA = 456.2 +/- 55 microW/cm2). A linear relationship was also demonstrated for benzo[a]pyrene phototoxicity with decreasing UV light intensity. 相似文献
1000.