全文获取类型
收费全文 | 53927篇 |
免费 | 711篇 |
国内免费 | 565篇 |
专业分类
测绘学 | 1454篇 |
大气科学 | 3818篇 |
地球物理 | 9988篇 |
地质学 | 19320篇 |
海洋学 | 4938篇 |
天文学 | 12928篇 |
综合类 | 188篇 |
自然地理 | 2569篇 |
出版年
2022年 | 365篇 |
2021年 | 634篇 |
2020年 | 661篇 |
2019年 | 712篇 |
2018年 | 1592篇 |
2017年 | 1509篇 |
2016年 | 1876篇 |
2015年 | 996篇 |
2014年 | 1754篇 |
2013年 | 2877篇 |
2012年 | 1866篇 |
2011年 | 2392篇 |
2010年 | 2077篇 |
2009年 | 2696篇 |
2008年 | 2307篇 |
2007年 | 2358篇 |
2006年 | 2207篇 |
2005年 | 1630篇 |
2004年 | 1650篇 |
2003年 | 1561篇 |
2002年 | 1487篇 |
2001年 | 1308篇 |
2000年 | 1222篇 |
1999年 | 999篇 |
1998年 | 1046篇 |
1997年 | 950篇 |
1996年 | 822篇 |
1995年 | 787篇 |
1994年 | 692篇 |
1993年 | 609篇 |
1992年 | 595篇 |
1991年 | 596篇 |
1990年 | 629篇 |
1989年 | 498篇 |
1988年 | 507篇 |
1987年 | 530篇 |
1986年 | 493篇 |
1985年 | 614篇 |
1984年 | 678篇 |
1983年 | 592篇 |
1982年 | 564篇 |
1981年 | 501篇 |
1980年 | 473篇 |
1979年 | 478篇 |
1978年 | 462篇 |
1977年 | 371篇 |
1976年 | 346篇 |
1975年 | 357篇 |
1974年 | 312篇 |
1973年 | 348篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
The trophic relationships of the phytoplankton and zooplankton in the Vistula Lagoon in 2008?C2010 were investigated. In the current period, the lagoon is an eutrophic water body with summer blooms of blue-green algae. The trophic level of the Vistula Lagoon influences both the composition and quantitative characteristics of the communities of phytoplankton and zooplankton and the trophic relationships between them. In the analyzed period, the consumption of phytoplankton by the zooplankton on the average in the growing season was 28%, which is 1.5 times higher than in the late 1970s. The high grazing pressure of the zooplankton on the phytoplankton reduces its biomass, production, and the intensity of the blooming by the blue-green algae in the Vistula Lagoon. 相似文献
992.
I. G. Boyarskikh S. A. Khudyaev S. G. Platonova S. P. Kolotukhin A. V. Shitov T. A. Kukushkina O. V. Chankina 《Izvestiya Atmospheric and Oceanic Physics》2012,48(7):747-760
Local geophysical and geochemical anomalies affect the polymorphism of taste variations, berry shape, and content of some biologically active substances in Lonicera caerulea leaves in the tectonically active Altai Mountains (Dzhazator River basin). 相似文献
993.
A study was conducted to understand the mechanisms driving observed subtidal variability in the stratification of Saldanha Bay, located in the southern Benguela system. It was found that the 6–8 day period variability in bay stratification was caused by the inflow and outflow of cold upwelled water driven by changing baroclinic pressure gradients between the coastal and bay domains. The direction and magnitude of the pressure gradients were governed by coastal upwelling activity and a lag in the response of the bay to changes in density structure in the coastal ocean. When the pressure gradients were bayward and cold water was being driven into the bay the cycle was termed to be in an ‘ active phase ’ and the reverse was termed the ‘ relaxation phase ’. The upwelling-favourable equatorward wind stress impacted the bay stratification in two ways: on the regional scale, wind drives upwelling and governs the inflow–outflow of cold upwelled bottom water, which strengthens stratification; conversely, on the local bay scale, wind drives vertical mixing, which weakens stratification. A four-phase model is used to describe the observed variability in stratification in the bay. The associated density-driven exchange flows are capable of flushing the bay in 6–8 days, about one-third of the time for tidal exchange alone (c. 25 days). These inflows of cold bottom water are ecologically critical as they supply nutrients to the bay and thus impose a control on new production within the bay environment. Further ecological implications of this bay–ocean exchange include export of phytoplankton new production to the coast, limitation of the risk of harmful algal blooms (HABs) and the division of the system into two distinct ecosystems (bay and lagoon). 相似文献
994.
Alekseeva T. A. Raev M. D. Tikhonov V. V. Sokolova J. V. Sharkov E. A. Frolov S. V. Serovetnikov S. S. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(9):1076-1080
Izvestiya, Atmospheric and Oceanic Physics - The Arctic Sea ice area, calculated by the VASIA2 algorithm using the SSMIS data during the most intensive melting of the ice cover in 2019, is compared... 相似文献
995.
Dyment L. N. Aksenov P. V. Losev S. M. Porubaev V. S. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(9):1081-1086
Izvestiya, Atmospheric and Oceanic Physics - The values of the characteristics of ice-cover leads in the Laptev and East Siberian Seas calculated from satellite images with spatial resolution of... 相似文献
996.
The article presents information on the current experiment of research on wind wave parameters in the Black Sea coastal zone. Two wave-meter devices are the part of the measuring equipment of the Black Sea testing site Gelendzhik of the Shirshov Institute of Oceanology (IO RAS). The integral characteristics of wind waves accumulated and obtained in real time may be in demand by experts in operational and satellite oceanography.
相似文献997.
Pavlenko L. F. Barabashin T. O. Zhukova S. V. Korablina I. V. Anohina N. S. Klimenko T. L. Ekilik V. S. 《Oceanology》2022,62(1):59-67
Oceanology - The results of studies of oil pollution (by the sum of hydrocarbons and resinous substances) of water and bottom sediments in the northeast Black Sea in spring and autumn are... 相似文献
998.
Zavialov P. O. Zavialov I. B. Izhitskiy A. S. Izhitskaya E. S. Konovalov B. V. Krementskiy V. V. Nemirovskaya I. A. Chasovnikov V. K. 《Oceanology》2022,62(2):162-170
Oceanology - The paper presents the results of an analysis of the main pollutants (heavy metals, pesticides, detergents, hydrocarbons) in water, suspended particulate matter, and bottom sediments,... 相似文献
999.
Oceanology - A comparative analysis of the content and composition of organic matter (OM) in samples of bottom sediments and subaqueous permafrost rocks by the concentration of organic carbon (OC),... 相似文献
1000.
This study describes an automatic berthing system with mooring lines. It is designed to be berthed by using mooring device on the upper deck of a ship. It is to berth once maintaining parallel with the quay by controlling both forward and aft breast lines. Berthing method is used through length adjustment of mooring lines connected between ship and quay by controlling the angular velocity and the torque of hydraulic motor in mooring device. The study is conducted under three changing conditions of draft, such as even-keel, rise of the gravity center and trim to stern. Variables affecting berthing stability are determined based on the control performance of each condition. Bond graphs method is used to model the system. Controller is designed as PID control method of reference-model algorithm. The control program is composed of synchronous control system based on the equations derived with the numerical analysis. The tank test is conducted to verify the usefulness of the control program. 相似文献