全文获取类型
收费全文 | 40249篇 |
免费 | 6836篇 |
国内免费 | 9277篇 |
专业分类
测绘学 | 3792篇 |
大气科学 | 6460篇 |
地球物理 | 7537篇 |
地质学 | 20841篇 |
海洋学 | 5371篇 |
天文学 | 3427篇 |
综合类 | 2739篇 |
自然地理 | 6195篇 |
出版年
2024年 | 274篇 |
2023年 | 729篇 |
2022年 | 1468篇 |
2021年 | 1719篇 |
2020年 | 1598篇 |
2019年 | 1958篇 |
2018年 | 1409篇 |
2017年 | 1664篇 |
2016年 | 1669篇 |
2015年 | 1869篇 |
2014年 | 2333篇 |
2013年 | 2299篇 |
2012年 | 2423篇 |
2011年 | 2546篇 |
2010年 | 2199篇 |
2009年 | 2732篇 |
2008年 | 2613篇 |
2007年 | 2758篇 |
2006年 | 2677篇 |
2005年 | 2535篇 |
2004年 | 2215篇 |
2003年 | 2075篇 |
2002年 | 1780篇 |
2001年 | 1598篇 |
2000年 | 1600篇 |
1999年 | 1381篇 |
1998年 | 1227篇 |
1997年 | 894篇 |
1996年 | 749篇 |
1995年 | 648篇 |
1994年 | 610篇 |
1993年 | 521篇 |
1992年 | 382篇 |
1991年 | 327篇 |
1990年 | 217篇 |
1989年 | 179篇 |
1988年 | 153篇 |
1987年 | 86篇 |
1986年 | 52篇 |
1985年 | 42篇 |
1984年 | 27篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 18篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1954年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
122.
冬至初春黄海暖流的路径和起源 总被引:18,自引:0,他引:18
主要根据近几年来中韩黄海水循环动力学合作调查结果,结合有关观测资料,进一步分析了冬至初春黄海暖流的路径和起源.与以往类似研究不同的主要有两点:(1)初步探讨了黄海暖流路径的季节和年际变异,并指出这种变异与北向风的强弱密切相关;(2)通过分析济州岛西侧海域混合水的去向,进一步确认了部分混合水绕济州岛运行,并进入济州海峡这一事实.同时,初步揭示进入黄海的混合水,即黄海暖流水,含有更多的东海陆架水成分. 相似文献
123.
Seasonal and annual variations of marine sinking particulate flux during 1993~1996 in the central South China Sea 总被引:1,自引:0,他引:1
CHEN Ronghu WIESNER M G ZHENG Yulong CHENG Xinrong JIN Haiyan ZHAO Qingying ZHENG Lianfu 《海洋学报(英文版)》2007,26(3):33-43
A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species (Globigerinoides sacculifer, G. ruber, Globigerinita glutinata, Neogloboquadrina dutertrei) and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution. 相似文献
124.
125.
126.
Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green‘s scond identity. This theory can be reduced to a number of the most typical mild-slope equations curreutly in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms. 相似文献
127.
128.
The Ocean Drilling Program Leg 175 recovered a unique series of stratigraphically continuous sedimentary sections along the SW African margin, an area which is presently affected by active coastal upwelling. The accumulation rates of organic and inorganic carbon are a major component of this record. Four Leg 175 sites (1082, 1084, 1085, 1087) are chosen as part of a latitudinal transect from the present northern to southern boundaries of the Benguela Current upwelling system, to decipher the Pliocene–Pleistocene history of biogenic production and its relationship with global and local changes in oceanic circulation and climate. The pattern of CaCO3 and Corg mass accumulation rates (MARs) over 0.25-Myr intervals indicates that the evolution of carbon burial is highly variable between the northern and the southern Benguela regions, as well as between sites that have similar hydrological conditions. This, as well as the presence over most locations of high-amplitude, rapid changes of carbon burial, reflect the partitioning of biogenic production and patterns of sedimentation into local compartments over the Benguela margin. The combined mapping of CaCO3 and Corg MARs at the study locations suggests four distinct evolutionary periods, which are essentially linked with major steps in global climate change: the early Pliocene, the mid-Pliocene warm event, a late Pliocene intensification of northern hemisphere glaciation and the Pleistocene. The early Pliocene spatially heterogeneous patterns of carbon burial are thought to reflect the occurrence of mass-gravitational movements over the Benguela slope which resulted in disruption of the recorded biogenic production. This was followed (3.5–3 Ma) by an episode of peak carbonate accumulation over the whole margin and, subsequently, by the onset of Benguela provincialism into a northern and a southern sedimentary regime near 2 Ma. This mid and late Pliocene evolution is interpreted as a direct response to changes in the ventilation of bottom and intermediate waters, as well as to dynamics of the subtropical gyral circulation and associated wind stress. 相似文献
129.
东海温度锋的分布特征及其季节变异 总被引:8,自引:4,他引:8
根据1934-1988年东海水文观测资料,重点分析东海温度锋的分布特征及其季节变异,并结合近期中日黑潮合作调查研究成果,初步探讨温度锋季节变异和水团演变的关系,所得主要结论是:(1)东海不仅常年存在浙闽沿岸锋,东海北部陆架锋和黑潮锋,而且、春、夏两季,在东海南部还出现一条东海中部出架锋。(2)江海温度锋季节变化的特点是:冬季,锋的宽度和强度皆是表层最强,夏季,表层温度锋仅出现在浙江近岸小范围海域。 相似文献
130.
AnomalouschangeoftheAntarcticseaiceandglobalsealevelchange¥XieSimei;ZouBing;WangYiandBaoChenglan(1.NationalMarineEnvironmentF... 相似文献