全文获取类型
收费全文 | 42777篇 |
免费 | 1134篇 |
国内免费 | 1135篇 |
专业分类
测绘学 | 1111篇 |
大气科学 | 3381篇 |
地球物理 | 8993篇 |
地质学 | 15630篇 |
海洋学 | 3848篇 |
天文学 | 8850篇 |
综合类 | 262篇 |
自然地理 | 2971篇 |
出版年
2022年 | 310篇 |
2021年 | 528篇 |
2020年 | 515篇 |
2019年 | 572篇 |
2018年 | 1024篇 |
2017年 | 976篇 |
2016年 | 1194篇 |
2015年 | 860篇 |
2014年 | 1237篇 |
2013年 | 2173篇 |
2012年 | 1568篇 |
2011年 | 2013篇 |
2010年 | 1735篇 |
2009年 | 2305篇 |
2008年 | 1963篇 |
2007年 | 2007篇 |
2006年 | 1908篇 |
2005年 | 1396篇 |
2004年 | 1323篇 |
2003年 | 1209篇 |
2002年 | 1177篇 |
2001年 | 971篇 |
2000年 | 951篇 |
1999年 | 778篇 |
1998年 | 817篇 |
1997年 | 774篇 |
1996年 | 651篇 |
1995年 | 639篇 |
1994年 | 553篇 |
1993年 | 482篇 |
1992年 | 478篇 |
1991年 | 448篇 |
1990年 | 521篇 |
1989年 | 431篇 |
1988年 | 409篇 |
1987年 | 499篇 |
1986年 | 387篇 |
1985年 | 499篇 |
1984年 | 604篇 |
1983年 | 519篇 |
1982年 | 516篇 |
1981年 | 475篇 |
1980年 | 473篇 |
1979年 | 411篇 |
1978年 | 383篇 |
1977年 | 392篇 |
1976年 | 370篇 |
1975年 | 340篇 |
1974年 | 365篇 |
1973年 | 385篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Seasonal variation of global surface pressure and water vapor 总被引:1,自引:0,他引:1
TSING-CHANG CHEN JAU-MING CHEN SIEGFRIED SCHUBERT LAWRENCE L. TAKACS 《地球,A辑:动力气象学与海洋学》1997,49(5):613-621
Previous studies have shown that the seasonal variation of global-mean surface pressure ( p s ) results from variation of global-mean water vapor pressure ( p w ). The current study, employing the global data generated by Version 1 of the Goddard Earth Observing System (GEOS-1) Data Assimilation System, shows that seasonal variations of regional p s and p w tend to be out of phase (particularly in the subtropics of the two hemispheres) and that the magnitude of the former variation is generally much larger than that of the latter. The seasonal variations of these two quantities are maintained by airmass and water vapor transports by the global divergent circulation, which is driven by the latent heat released by cumulus convection over the water vapor sink, as the "water mass forcing" mechanism predicted. Since p w and p s are used often in depicting the climate system, assessments of climate change in terms of the global-mean and regional variations of these two variables should be interpreted with caution. 相似文献
113.
114.
L. Frlin T. Andersson B.-E. Bengtsson J. Hrdig . Larsson 《Marine environmental research》1985,17(2-4)
The present preliminary report on studies of the influence of pulp bleach plant effluents on hepatic biotransformation enzymes in fish is a part of a major characterisation of biochemical and physiological effects of effluents from pulp industries in Sweden. Our studies on the xenobiotic biotransformation enzymes demonstrate, so far, that the pulp effluents have the potential to strongly induce 7-ethoxyresorufin-O-deethylase activity (EROD) in fish liver and that fish living in the receiving water of an effluent from a pulp bleach plant have induced hepatic EROD activities as well as higher hepatic UDP glucuronyltransferase activities than those living in an unpolluted area. It is thus apparent that measures of induction of biotransformation enzymes in fish liver may be a useful approach in monitoring the presence of potential hazardous compounds released from pulp industries. 相似文献
115.
The paper is concerned with the evaluation of the drift current parameters derived through the use of an analytical model.
In this model, effective when stratification is stable and indifferent, the vertical turbulence coefficient profile is prescribed
by the power function, and hydrodynamic quantities are prescribed using the external parameters of the problem (wind stress,
the Coriolis parameter, and the dimensionless stratification parameter). Model data are compared with the observations of
the upper mixed layer in the vicinity of the oceanic Station C, conducted during one year. It is shown that, under the spring-summer-time
warming conditions, the model at issue is capable of adequately simulating the upper ocean layer dynamics.
Translated by Vladimir A. Puchkin. 相似文献
116.
117.
The importance of the diet as a source of tributyltin (TBT) in Nucella lapillus was studied using [14C]tributyltin chloride. In N. lapillus provided with prelabelled mussels, Mytilus edulis, in labelled water (mean 20·5 ng/litre TBT) the rate of accumulation of total 14C was 2–3 times that in unfed animals. Owing to its degradation in the tissues of both fed and unfed animals, concentrations of [14C]TBT tended to reach a plateau after only 28 days. However, total concentrations of 14C were still increasing after 49 days. Under experimental conditions (15°C, ample food, no disturbance) the diet accounted for about 50% of the body burden of TBT in N. lapillus after 49 days exposure: concentration factors (dry tissue/water) for [14C]TBT in both male and female N. lapillus were similar at about 60 000 in fed and 30 000 in unfed animals. It is concluded that the diet may contribute less than half of the body burden of TBT found in natural populations subjected to life-long exposure. 相似文献
118.
M. Tiwari R. Ramesh B. L. K. Somayajulu A. J. T. Jull G. S. Burr 《Geo-Marine Letters》2006,26(1):23-30
Rapid shifts in past climate recorded in polar ice sheets have elicited various explanations relating to either thermohaline
circulation changes by ice-rafting or natural greenhouse gas concentrations modulated by climatic conditions in the tropics.
To compare the tropical paleoclimate record with the polar record, one must choose sediment cores from highly productive ocean
regions. Necessarily, such regions reflect the wind records in the tropics, because high productivity is associated with upwelling
driven by winds. Comparing tropical precipitation records with high-latitude records is, however, a more difficult task because
sediments recording paleoprecipitation usually have low sedimentation rates, and offer coarser resolution relative to polar
ice cores. Here, we present δ
18O data of three planktonic species of Foraminifera (a proxy for precipitation) from such a sediment core, spanning the past
35 ka for the equatorial Indian Ocean, which falls under the southwest monsoon (SWM) realm. Results show that minimum SWM
precipitation occurred at the Last Glacial Maximum, with a subsequent increase at Termination IA. During the Holocene, SWM
precipitation intensified uniformly up to the core top (∼2.2 ka b.p.), as revealed by generally decreasing δ
18O values. Variations in precipitation are consistent with climate changes recorded in polar ice sheets. Although the different resolutions of the two records preclude
a rigorous comparison, abrupt cooling/warming events appear to be accompanied by sudden reduction/enhancement in (SWM) rainfall.
Thus, mechanisms with time scales much shorter than a millennium, such as natural greenhouse warming (e.g., CH4 concentration), controlled by emissions from the tropics, could have played a major role in high-latitude climate change. 相似文献
119.
120.