全文获取类型
收费全文 | 6605篇 |
免费 | 1076篇 |
国内免费 | 1371篇 |
专业分类
测绘学 | 815篇 |
大气科学 | 1024篇 |
地球物理 | 2028篇 |
地质学 | 2854篇 |
海洋学 | 957篇 |
天文学 | 15篇 |
综合类 | 403篇 |
自然地理 | 956篇 |
出版年
2024年 | 22篇 |
2023年 | 104篇 |
2022年 | 229篇 |
2021年 | 283篇 |
2020年 | 278篇 |
2019年 | 356篇 |
2018年 | 288篇 |
2017年 | 315篇 |
2016年 | 371篇 |
2015年 | 340篇 |
2014年 | 504篇 |
2013年 | 520篇 |
2012年 | 481篇 |
2011年 | 467篇 |
2010年 | 426篇 |
2009年 | 434篇 |
2008年 | 432篇 |
2007年 | 487篇 |
2006年 | 450篇 |
2005年 | 372篇 |
2004年 | 296篇 |
2003年 | 266篇 |
2002年 | 243篇 |
2001年 | 172篇 |
2000年 | 150篇 |
1999年 | 128篇 |
1998年 | 128篇 |
1997年 | 92篇 |
1996年 | 88篇 |
1995年 | 72篇 |
1994年 | 66篇 |
1993年 | 54篇 |
1992年 | 44篇 |
1991年 | 27篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
排序方式: 共有9052条查询结果,搜索用时 625 毫秒
31.
1 .IntroductionTheappraisalofagooddesignforaverylargefloatingstructure(VLFS)thatwillserveinaspeci fiedoceanarearequiresthatthestructuralsystembeeconomicallydesigned ,therequirementsforitsfunctionbesatisfiedandthestructurekeepsstableinitswholeserviceperio… 相似文献
32.
33.
34.
人工鱼礁工程的风险评估 总被引:1,自引:0,他引:1
对台风暴潮影响下的嵊泗海域人工鱼礁工程做了风险评估,考虑了台风暴潮中出现的大浪和风暴潮减水对鱼礁联合作用的危害。风险评估分为危险灾害识别、失效概率计算、失效后果评估、风险准则评定和风险管理决策几个主要的步骤。在失效概率的计算中采用基于应用设计点的重点抽样法随机模拟的技术,这一随机模拟技术可以广泛的应用与海洋工程结构的风险评估当中。 相似文献
35.
The effects of different lateral confinement stress on the fatigue behavior of and cumulative damage to plain concrete are investigated experimentally. Eighty 100 mm x 100 mm x 100 mm specimens of ordinary strength concrete are tested under constant- or variable-amplitude fatigue loading and lateral confinement pressure in two orthogonal directions. A fatigue equation is developed by modifying the classical Aas-Jakobsen S-N equation for taking into account the effect of the confined stress on fatigue strength of plain concrete. The results of variable-amplitude fatigue tests indicate that the linear damage theory proposed by Palmgren and Miner is unreasonable in the biaxial stress state. A nonlinear cumulative damage model that could model the effects of the magnitude and sequence of variable-amplitude fatigue loading and lateral confinement pressure is proposed on the basis of the evolution laws of the residual strains in the longitudinal direction during fatigue tests. The residual fatigue life predic 相似文献
36.
Arthur C. R. Gleason Diego Lirman Dana Williams Nuno R. Gracias Brooke E. Gintert Hossein Madjidi R. Pamela Reid G. Chris Boynton Shahriar Negahdaripour Margaret Miller & Philip Kramer 《Marine Ecology》2007,28(2):254-258
Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video‐mosaic methodology that provides a high‐resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two‐dimensional video‐mosaic technology is well‐suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies. 相似文献
37.
本文推导了随机载荷下的疲劳损伤计算公式。数值计算结果表明:P.H.Wirsching给出的公式在宽带情况下与实际情况不符;G.Chaudhury给出的公式在窄带情况下与实际不符;本文绘出的公式不仅适合于窄带,也适合于具有各种不同带宽的宽带随机载荷。 相似文献
38.
应用模糊综合评价方法对大连臭水套海域疏浚物预选倾倒区的水质状况进行了评价,得到了有益的结论。 相似文献
39.
A bottom longline fishery operated in the EEZ of New Caledonia from 1988 to 1991. Fishing focused on five seamounts with summits at depths ranging from 500 to 750 m. The target species was alfonsino, Beryx splendens. As the soundings available from marine charts were not detailed enough, the fishing masters had to make their own charts in order to set the gear in the right location. A series of 11 scientific cruises devoted to a research program on alfonsino was launched in late 1991. During the first scientific cruises, several days were spent mapping the seabed to improve the existing knowledge of the topography of three seamounts by coupling the EDO echosounder depth measurements to the GPS positions. As this procedure is slow, it is applicable to limited areas or, if a wider grid is used, to large zones to locate major structures such as ridges and seamounts. The emergence of the multibeam echosounder has greatly improved seabed mapping performance. This tool seems to fit the requirement of exploratory deep-bottom fishing particularly well, as it covers large areas while providing details of the bottom. The EM 12 was used to obtain bathymetry and imagery of the SE portion of the EEZ of New Caledonia, covering an approximate area of 70,000 km2 in two weeks. For depths ranging from 500 to 4,500 m, the results were impressive. They confirmed the known major features and provided greater topographical detail, revealing fine unknown structures. They also provided information on the type of substratum, information which might influence the fishing strategy. Finally, they made it possible to obtain an accurate estimate of the exploitable area which in turn led to new stock estimates. 相似文献
40.