全文获取类型
收费全文 | 2889篇 |
免费 | 399篇 |
国内免费 | 1477篇 |
专业分类
测绘学 | 72篇 |
大气科学 | 61篇 |
地球物理 | 858篇 |
地质学 | 2681篇 |
海洋学 | 574篇 |
天文学 | 14篇 |
综合类 | 111篇 |
自然地理 | 394篇 |
出版年
2024年 | 12篇 |
2023年 | 61篇 |
2022年 | 121篇 |
2021年 | 118篇 |
2020年 | 175篇 |
2019年 | 201篇 |
2018年 | 179篇 |
2017年 | 148篇 |
2016年 | 230篇 |
2015年 | 180篇 |
2014年 | 238篇 |
2013年 | 276篇 |
2012年 | 202篇 |
2011年 | 255篇 |
2010年 | 218篇 |
2009年 | 212篇 |
2008年 | 228篇 |
2007年 | 239篇 |
2006年 | 243篇 |
2005年 | 221篇 |
2004年 | 153篇 |
2003年 | 129篇 |
2002年 | 106篇 |
2001年 | 89篇 |
2000年 | 64篇 |
1999年 | 60篇 |
1998年 | 56篇 |
1997年 | 62篇 |
1996年 | 66篇 |
1995年 | 41篇 |
1994年 | 33篇 |
1993年 | 35篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有4765条查询结果,搜索用时 0 毫秒
11.
Full-rangenonlinearanalysisoffatiguebehaviorsofreinforcedconcretestructuresbyfiniteelementmethod¥SongYupu;ZhaoShunbo;WangRuim... 相似文献
12.
Li Runpei Chen Weigang Gu Yongning
Professor Shanghai Jiao Tong University Shanghai Assistant Shanghai Jiao Tong University Shanghai 《中国海洋工程》1996,(1)
In this paper a numerical analysis method combining FEM incemental technique with limit analysis concept is proposed for the study of the static strength of offshore platform in collision. Large deformation and plasticity are accounted for and the limit yield surface expressed by generalized stress for a tubular section is derived. The modified stiffness matrix of space beam element is formulated by Plastic Node Method. The buckling behavior of beam columns can also be taken into account. It can trace the generation of plastic hinges during loading and finally the ultimate strength of offshore platform against collision is obtained. 相似文献
13.
14.
Claudio Campagna Alberto R. Piola Maria Rosa Marin Mirtha Lewis Teresita Fernndez 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1907-1924
This study describes the association between transient, mesoscale hydrographic features along the axis of the Brazil–Malvinas Confluence, in the SW Atlantic, and the foraging behavior of 2–3-year-old (focal) juvenile southern elephant seals, Mirounga leonina, from Península Valdés, Argentina. Departing from the dominant pattern of foraging on predictable bathymetric fronts on the Patagonian shelf and slope, three females out of 12 satellite-tracked juveniles remained at the edge of young warm-core eddies and near the outer core of cold-core eddies, coinciding with the most productive areas of these temperature fronts. Seal trajectories along high-temperature gradients were always consistent with the speed and direction of surface currents inferred from the temperature distribution and confirmed by surface drifters. Movements of foraging seals were compared with those of surface drifters, coinciding in time and space and yielding independent and consistent data on regional water circulation parameters. The diving pattern recorded for one focal seal yielded shallower dives and a loose diel pattern in the eddy, and a marked diurnal cycle compatible with foraging on vertically migrating prey in the cold waters of the Malvinas Current. Pre-reproductive females that use the mesoscale fronts of the Argentine Basin as an alternative foraging area would benefit from lower competition with more experienced seals and with other top predators that reproduce along the coast of Patagonia. 相似文献
15.
本文提出在小偏心受压构件正截面强度计算中,取消弯曲抗压强度fcm(Rw),采用轴心抗压强度fc,这与构件的实际破坏形态相符。对小偏心受压构件正截面强度计算提出了设计建议。特别是对工程上大量应用的矩形截面对称配筋小偏压构件提示了简捷的设计方法,与以往的近似计算方法相比具有物理概念明确,精度高,方法简捷的特点。 相似文献
16.
17.
18.
19.
This paper presents the findings from an in-depth analysis of the (axial) stiffness data recorded during tension–tension fatigue tests on wire ropes, particularly in relation to how changes in stiffness during testing relate to changes in rope strength. A linear relationship between stiffness and strength is shown to exist and a methodology presented for quantifying residual strength with applied cycles. New lower bound fatigue lines for six-strand rope and spiral strand are presented which are based on a 10% loss of strength. These new lines have the advantage of having been established using a common discard criterion for wire ropes. 相似文献
20.
The longitudinal strength of turret mooring productive/storage tanker is studied.A numeri-cal example has been implemented according to the method presented in this paper to give practical il-lustration.From the results of the numerical example,it is concluded that the turret hole located near theforward of the amidships has small effect on the longitudinal strength of the ship hull.As for design ex-treme value of wave bending moment of storage tanker,statistic method is a more reasonablemethodology,especially with the consideration of the servere environmental conditions.The primary esti-mation of design section modulus of turret storage tanker can be determined by this design bending mo-ment. 相似文献