全文获取类型
收费全文 | 36449篇 |
免费 | 6677篇 |
国内免费 | 10034篇 |
专业分类
测绘学 | 2757篇 |
大气科学 | 7106篇 |
地球物理 | 9201篇 |
地质学 | 19756篇 |
海洋学 | 4266篇 |
天文学 | 1498篇 |
综合类 | 4164篇 |
自然地理 | 4412篇 |
出版年
2024年 | 113篇 |
2023年 | 429篇 |
2022年 | 1403篇 |
2021年 | 1611篇 |
2020年 | 1292篇 |
2019年 | 1570篇 |
2018年 | 1745篇 |
2017年 | 1605篇 |
2016年 | 1879篇 |
2015年 | 1665篇 |
2014年 | 1960篇 |
2013年 | 1936篇 |
2012年 | 1875篇 |
2011年 | 2357篇 |
2010年 | 2306篇 |
2009年 | 2332篇 |
2008年 | 1921篇 |
2007年 | 1967篇 |
2006年 | 1799篇 |
2005年 | 1795篇 |
2004年 | 2010篇 |
2003年 | 1603篇 |
2002年 | 1351篇 |
2001年 | 1305篇 |
2000年 | 1317篇 |
1999年 | 1697篇 |
1998年 | 1446篇 |
1997年 | 1355篇 |
1996年 | 1192篇 |
1995年 | 1027篇 |
1994年 | 881篇 |
1993年 | 985篇 |
1992年 | 812篇 |
1991年 | 565篇 |
1990年 | 360篇 |
1989年 | 366篇 |
1988年 | 286篇 |
1987年 | 201篇 |
1986年 | 166篇 |
1985年 | 90篇 |
1984年 | 101篇 |
1983年 | 75篇 |
1982年 | 69篇 |
1981年 | 56篇 |
1980年 | 34篇 |
1979年 | 36篇 |
1978年 | 18篇 |
1977年 | 25篇 |
1976年 | 16篇 |
1958年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Three continuous marine fish cell lines of FG (i. e., Hounder Gill) from flounder (Paralichthys olivaceus) gill, SPH (i. e. , Sea Perch Heart) from sea perch (Lateolabrax japonicus) heart and RSBF (i.e., Red Sea Bream Fin) from red sea bream (Pagrosomus major) fin, were characterized by lactate dehydrogenase (LDH) isozyme and morphological analysis. The LDH isozyme patterns of these three cell lines and their corresponding tissues of origin were investigated and compared. The results showed: (1) No difference was found in the LDH isozyme patterns of FG and flounder gill tissue. However, the LDH isozyme patterns of SPH and RSBF were significantly different from their corresponding tissues of origin; (2) LDH isozyme patterns of FG, SPH and RSBF were markedly different from each other and could serve as genetic markers for species identification and detection of cross contamination. Morphological change analysis of these three cell lines in comparison to their original tissues indicated that FG cells still appeared epithelioid without morphological transformation. However, morphological changes were found in SPH and RSBF compared to their original tissues. Therefore, the cellular morphology was still plastic in the relatively stable culture conditions, and it was possible that change of LDH patterns wasrelated to morphological changes of fish cells in vitro. 相似文献
92.
Technique for Controlling Spread of Limnotic Oncomelania 总被引:1,自引:0,他引:1
Schistosomiasis is a parasitic disease mostly found in areas along the Changjiang River of China. The disease is spread solely through an intermediary named oncomelania, so its spread of schistosomiasis can be controlled by properly designing water intakes which prevent oncomelania from entering farming land or residential areas. This paper reports a successful design process and a new oncomelania-free intake device. The design of the new intake is based on a sound research program in which extensive experimental studies were carried out to gain knowledge of oncomelania eco-hydraulic behavior and detailed flow field information through CFD simulation. 相似文献
93.
Qinghai Wang Wenliang Xu Dongyan Wang Jingqian LinCollege of Earth Sciences Jilin University Changchun China 《东北亚地学研究》2003,(2)
1IntroductionAdakite has specially sense in the resuming structure background of rock formed,because of its distinctive geochemistry feature and implying partic-ular petrogenesis and ore genesis mechanism (De-fant and Drummond,1990),as a result,it arouses numerous researchers widely concern. After adakite conception was drawn by Chinese (Wang etal.,2000), it was widely concerned by domestic re-searchers (Wang etal.,2000,2001a,2001b;Xu etal.,2000;Pan etal.,2001;Qian,2001;Xu etal.,2001;X… 相似文献
94.
本文简述了国际天球参考架的发展历史和现在射电参考架的现状—基准源选择的标准和参考架的稳定性。描述了地面上光学观测在依巴谷参考架的维持和加密的一系列工作。介绍由天体测量卫星GAIA和SIM给出的天球参考架可能逵到的精度。详述了在今后十年中地面天体测量的作用以及正在开展有关天球参考架的研究课题 ,同时也列出了我国正在和即将开展天体测量的几个研究课题 相似文献
95.
The present paper reports 9 species of pontoniine shrimps collected from Hainan IS-land ,South China Sea ,by the Joint Chinese-German Marine Biology Expeditions,in which Peri-climenaeus arabicus (Calman,1939) and Periclimenaeus hecate (Nobili,1904) are recorded for the first time from Hainan Island. 相似文献
96.
地倾斜台站数字化、模拟观测数据频率特性研究 总被引:2,自引:2,他引:0
分析了四川、云南的部分地倾斜数字化观测与模拟观测资料的特性,从频率范围,周期10天以上的FFT谱特性,固体潮波振幅,相位特征值等方面,论述了地倾斜数字化资料较模拟记录资料的信息组成变化,并对资料的分析与应用进行了初步探讨。 相似文献
97.
Late Cretaceous-Paleogene Palynostratigraphy from the Arkhara-Boguchan Brown Coal Mine of Zeya-Bureya Depression, Russia 总被引:1,自引:1,他引:0
Tatyana V. Kezina 《东北亚地学研究》2003,(2)
1IntroductionThe Arkhara-Boguchan brown coal mine is lo-cated in the western Arkhara depression,southeast-ern part of the Zea-Bureya Basin (Fig.1). Late Creta-ceous-Paleogene coal-bearing strata are well out-cropped at the Arkhara-Boguchan quarry. It contains four coal-bearing beds (in descending order): “Ve-likan”, “Promezhutochny”,“Dvoinoy”and “Nyzhny”, and composed of three sedimentary cycles (Fig.2). The lower cycle can be divided into two sub-cycles:the lowest sub-cycle is … 相似文献
98.
1StrongtideandastronomicalconditionsPartial solar eclipse occurred 4 times in 1964, 1982 and 2000 respectively. Time interval is about 3 Saros periods (one Saros period is 18 years and 10.33~11.33 days). Total lunar eclipse occurred 2 times in 1964 and 2000 respectively and 3 times in 1982. However, there was no lunar eclipse in 1966, 1984 and 2002. It seems that they had similar astro-nomical conditions and the best was in 1982. The studies about the effect of tide on the global climate… 相似文献
99.
CORROSION AND ADHERENCE AT SEA OIL-PLATFORM 总被引:1,自引:0,他引:1
Measurements of the adhesive corrosion and protective potentials of 3 Bohai Sea oilplatforms under different cathodic protection showed corrosion still occurred on these platforms undertheir designed protective potentials. Preliminary conclusions from indoor experiments on the relation betweenadhesive corrosion and cathodic protection showed adhering organisms caused the corrosion onthese platforms. 相似文献
100.
A THREE-DIMENSIONAL ELASTIC NESTED-GRID MESO-(β-γ)SCALE ATMOSPHERIC MODEL——PARTI:MODEL DESCRIPTION 下载免费PDF全文
A three-dimensional elastic nonhydrostatic mesoscale(β-γ)model with nested-grid is presented.It uses a set of fullequations in terrain-following coordinates as its basic dynamic frame,which is solved with a time-splitting algorithmfor acoustic and gravity waves.The model physical parameterization includes a K-theory subgrid eddy mixing for cloudand free atmosphere,a bulk planetary boundary layer parameterization,and three types of sofisticated cloudmicrophysics schemes with double-parameters for hail-bearing clouds,warm clouds and snowing clouds respectively.The model is designed to be used flexibly for simulations of a variety of meso-and small-scale atmospheric processes,and can be improved as a regional and local operational NWP system in future. 相似文献