全文获取类型
收费全文 | 5864篇 |
免费 | 1477篇 |
国内免费 | 1973篇 |
专业分类
测绘学 | 707篇 |
大气科学 | 898篇 |
地球物理 | 1436篇 |
地质学 | 3802篇 |
海洋学 | 1092篇 |
天文学 | 84篇 |
综合类 | 556篇 |
自然地理 | 739篇 |
出版年
2024年 | 38篇 |
2023年 | 104篇 |
2022年 | 338篇 |
2021年 | 390篇 |
2020年 | 278篇 |
2019年 | 401篇 |
2018年 | 354篇 |
2017年 | 334篇 |
2016年 | 342篇 |
2015年 | 360篇 |
2014年 | 358篇 |
2013年 | 478篇 |
2012年 | 435篇 |
2011年 | 448篇 |
2010年 | 457篇 |
2009年 | 483篇 |
2008年 | 457篇 |
2007年 | 452篇 |
2006年 | 387篇 |
2005年 | 371篇 |
2004年 | 252篇 |
2003年 | 210篇 |
2002年 | 225篇 |
2001年 | 183篇 |
2000年 | 147篇 |
1999年 | 162篇 |
1998年 | 104篇 |
1997年 | 115篇 |
1996年 | 86篇 |
1995年 | 80篇 |
1994年 | 69篇 |
1993年 | 82篇 |
1992年 | 69篇 |
1991年 | 47篇 |
1990年 | 46篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1954年 | 6篇 |
1944年 | 2篇 |
1937年 | 4篇 |
1933年 | 3篇 |
排序方式: 共有9314条查询结果,搜索用时 31 毫秒
31.
象山港、三门湾软相潮间带底栖动物数量的水平分布与港湾的屏蔽性程度有一定的关系,生物量是三门湾(180.95g/m2)高于象山港(94.47g/m2),生物密度是象山港(816个/m2)高于三门湾(347个/m2)。决定所面生物数量变化的主要底栖动物种类数随着港湾屏蔽性程度的提高而相应地减少。生物数量的垂直分布主要受潮汐作用的影响,以中潮区为最高。生物量以6月份最大,密度是4月份最大。 相似文献
32.
33.
Internal soliton is the large amplitude wave existing in the pycnocline, induced by internal tide in the condition of special bottom topography. During its propagation process, the induced disturbance can bring about strong convergence of sea water and sudden strong current (wave-induced-current), which can cause severe threat to the ocean engineering structures, such as oil drilling platform and pipeline. In this paper, Morison’s empirical method, modal separation and regression analyses are introduced to estimate the forces and torques exerted by internal soliton on cylindrical piles. As an example, a limited set of observational data recording a passage of the internal soliton near Dongsha Islands is used to estimate the horizontal velocity and its acceleration in a vertical section for computing the force and torque on a supposed pile, and the estimation results are reasonable. It is shown that, the higher number of the modes retained in the calculation, the better the estimation of velocity profile fits the observational one. A better overall approximation to the real solution can be reached if there are more observational current data acquired in a whole vertical profile. 相似文献
34.
NotesEcologicalstudyofmacrobenthosinFuqingBay¥//INTRODUCTIONTheecologicalstudyOfmacrobenthoshasnotbeenrePOrtedthoughthemarine... 相似文献
35.
Under the artificial condition the 59Fe morphology in sea water, its concentration in sediment and phytoplankton, its distribution and metabolism in tissue organs of marine animals were studied. The results showed that the morphology of 59Fe was in a particulate state in sea water. The adsorption rule of 59Fe by three kinds of sediments was similar. The concentration ability of 59Fe by phytoplankton was very strong. The critical concentration organs of S9Fe by marine animals were viscera. The gross radioactivity of 59Fe was mainly concentrated in protein. The concentration factor of 59Fe by DNA was the highest one. After excretion experiment, 59Fe of all the tissue organs was not detected. Small part of59Fe remained in the organic acid and protein state. There was a redistribution process in sediment for59Fe. 相似文献
36.
37.
Khalid Maskaoui Tianling Zheng Huasheng Hong Zhiming Yu Zhong Hu Yun Tian Lizhe Cai 《海洋学报(英文版)》2003,22(3):443-451
The surface and bottom waters samples were collected from six locations in Xiamen western sea. The quantified estimation of bacterial production (3H-thymidine method) and observation of bacterial heterotrophic activity (14C-glucose method) have been made in order to have a better understanding of the role of marine bacteria and their activities. The results showed that the mean value of bacterial heterotrophic activity was 9×108 cells/(L.h) in the surface waters and 2.6×108 cells/(L.h) in the bottom waters. The mean value of bacterial production was 38×108 cells/(L.h) in the surface waters and 7.1×108 cells/(L.h) in the bottom waters. The relationship between bacterial production, heterotrophic activity, POC and DOC measured during this survey were discussed. The good understanding of the relationship between bacteria activity and total coliform was addressed. 相似文献
38.
东太平洋地区DSDP573孔始新世末期的微玻璃陨石 总被引:5,自引:1,他引:5
通过研究 DSDP5 73孔的岩心样品 ,首次在该孔始新世与渐新世的界线地层含金属粘土层中发现了微玻璃陨石 ,且主要富集在其底部。一个样品 (5 g)中最多可达 12粒。这些微玻璃陨石主要呈球形、椭球形。用电子探针测试了其化学成分 ,Si O2 含量为 2 9.6 4%~ 5 8.93%,Al2 O3 为 3.42 %~ 2 0 .96 %,Fe O为 9.98%~ 2 9.5 5 %,Mg O为 4.32 %~ 16 .0 5 %,Ir为 0 .0 6 %~ 0 .81%。总体来说 ,微玻璃陨石的化学成分变化较大 ,可能与靶岩的成分变化较大有关。始新世末期北美微玻璃陨石场的展布方向约为 2 5 0°,这与太平洋板块运动方向改变所需要的矢量变化(2 45°)仅相差 5°,推测很可能是始新世末期陨星的撞击引起了太平洋板块在该时期的运动方向由 NNW突然变为NWW。 相似文献
39.
Species composition and distribution of marine nematode community in the North Taiwan Strait 总被引:9,自引:4,他引:9
Cai Lizhe Hong Huasheng Zou Chaozhong Fang Shaohu L Xiaomei Zhang Yueping 《海洋学报(英文版)》2001,20(2):221-229
I~IOW~ne nelnatode is a ban gIOup of benthic OrgAnsrns. Abbot 5 000 spotes Of free-livingnelnatedes have ben dedbo so far, and it has ho estimated that abbot 20 (XX) are as yetunknoWn. Chinese bothologist has Paid attention to marine nelnatodes in China seas in yare. The spatial distribution and shoes commotion of marine nelnatedes in the HUanghe EstUary, Qinhuangdao waters, QingdaO Bay and Xiamen ~ have ho reported (Zhang etal., 1990, 1991, 1993; ac and Li, 1998). ~ new shoes in the… 相似文献
40.
本文对南海地区(0—20°N,105—135°E)海气环境场进行EOF分析。其结果除了深入了解南海地区气候的基本场外,还揭示了叠加在基本场上的各种扰动场与热带天气系统的联系,为研究南海ITCZ等热带天气系统以及南海环境场对EL—Ni(?)o现象的反映提供了研究依据。 相似文献