全文获取类型
收费全文 | 2723篇 |
免费 | 491篇 |
国内免费 | 710篇 |
专业分类
测绘学 | 207篇 |
大气科学 | 574篇 |
地球物理 | 687篇 |
地质学 | 1344篇 |
海洋学 | 417篇 |
天文学 | 114篇 |
综合类 | 237篇 |
自然地理 | 344篇 |
出版年
2024年 | 36篇 |
2023年 | 73篇 |
2022年 | 186篇 |
2021年 | 180篇 |
2020年 | 173篇 |
2019年 | 149篇 |
2018年 | 167篇 |
2017年 | 146篇 |
2016年 | 155篇 |
2015年 | 130篇 |
2014年 | 165篇 |
2013年 | 143篇 |
2012年 | 136篇 |
2011年 | 136篇 |
2010年 | 128篇 |
2009年 | 161篇 |
2008年 | 136篇 |
2007年 | 125篇 |
2006年 | 110篇 |
2005年 | 109篇 |
2004年 | 78篇 |
2003年 | 93篇 |
2002年 | 81篇 |
2001年 | 78篇 |
2000年 | 79篇 |
1999年 | 126篇 |
1998年 | 82篇 |
1997年 | 77篇 |
1996年 | 83篇 |
1995年 | 73篇 |
1994年 | 57篇 |
1993年 | 62篇 |
1992年 | 50篇 |
1991年 | 29篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1979年 | 8篇 |
1975年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有3924条查询结果,搜索用时 15 毫秒
1.
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
2.
Chen Tieyun Zhu Zhenghong
Professor Dept. of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai Lecturer 《中国海洋工程》1991,(1)
The plastic node method is reformulated by the variational principle and is applied to elasto-plastic finite element analysis of tubular joints, eventually including the effect of internal and external gussets, stiffener rings, etc., if necessary. Four different joints are studied here in detail for the elasto-plastic behavior, the strain at the hot spot, the strain concentration factor around the intersection line, and the propagation of the plastic region with loading up to collapse in order to determine the ultimate strength, safety factor, and development of the plastic field. The present results are in good agreement with the experimental results. 相似文献
3.
Tang Rongqing Wang Daoyan Zhang Xixian Egnineer Shanghai Jiao Tong University Shanghai Associate Professor Shanghai Jiao University Shanghai 《中国海洋工程》1993,(3)
- The authors have used a low-cost ROV of observation type for underice surveying of the Nen-Jiang Cross-river oil pipe line in the Da Qing oil field. The operation method, process and the safety measures for severe cold areas are presented. The fruitful tries and experience may be useful to ROV operators in severe cold areas. 相似文献
4.
龙感湖地区近3000年来的植被及其气候定量重建 总被引:18,自引:1,他引:18
本文依据龙感湖钻孔的孢粉及硅藻资料,探讨了该地区近3000年来的植被发展及气候变化,通过数值分析方法,重建了年均温及年降水的时间序列,发现气候波动存在的两个阶段,(依1.5kaB.P.前后划分)四个旋回(0.8ka的准周期)两个突变事件(3kaB.P)前后的冷暖急剧变化及1kaB.P的降温事件)。这些变化与敦德冰心及固城湖孢粉反映的气候波动有较好的一致性,具有全球变化意义。 相似文献
5.
Xie Simei Hao Chunjiang Zou Bin Jing Qiyi Liao Xiaohong Sheng Xiaowen Zhang Canrong 《海洋学报(英文版)》2000,19(1):35-46
INTRODUCTIONTheSMSRPSisstalledontheshipnavigatingovertheseaandreceivessatellitecloudmapsatanytimetoprovidereliablereal-timedataofmeteorologyandocean.Itisanimportantequipmentforsafeguardofshipnavigation.Chinahasthousandsofoceanicships.Butalmostallships,withonlyveryfewexception,arenotstalledbySMSRPS.Thecausesareasfollows:1.Thetechniqueisverycomplicated.2.Thedevelopmentcostisveryhigh.3.Ifweintroduceforeignequipment,thecostistooexpensive.4.Foreignequipmentanditssoftwarearecompletelyclo… 相似文献
6.
7.
8.
9.
The response of low‐ductility reinforced concrete (RC) frames, designed typically for a non‐seismic region, subjected to two frequencies of base excitations is studied. Five half‐scaled, two‐bay, two‐storey, RC frames, each approximately 5 m wide by 3.3 m high, were subjected to both horizontal and/or vertical base excitations with a frequency of 40 Hz as well as a lower frequency of about 4 Hz (close to the fundamental frequency) using a shake table. The imposed acceleration amplitude ranged from 0.2 to 1.2g. The test results showed that the response characteristics of the structures differed under high‐ and low‐frequency excitations. The frames were able to sustain high‐frequency excitations without damage but were inadequate for low‐frequency excitations, even though the frames exhibited some ductility. Linear‐elastic time‐history analysis can predict reasonably well the structural response under high‐frequency excitations. As the frames were not designed for seismic loads, the reinforcement detailing may not have been adequate, based on the crack pattern observed. The effect of vertical excitation can cause significant additional forces in the columns and moment reversals in the beams. The ‘strong‐column, weak‐beam’ approach for lateral load RC frame design is supported by experimental observations. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
10.
Vertical Ozone Profile over Tibet Using Sage I and II Data 总被引:8,自引:0,他引:8
VerticalOzoneProfileoverTibetUsingSageIandIData①ZouHan(邹捍)andGaoYongqi(郜永祺)InstituteofAtmosphericPhysics,ChineseAcademyofScie... 相似文献