全文获取类型
收费全文 | 16810篇 |
免费 | 4241篇 |
国内免费 | 5924篇 |
专业分类
测绘学 | 2512篇 |
大气科学 | 2691篇 |
地球物理 | 3457篇 |
地质学 | 10533篇 |
海洋学 | 3684篇 |
天文学 | 400篇 |
综合类 | 1485篇 |
自然地理 | 2213篇 |
出版年
2024年 | 134篇 |
2023年 | 359篇 |
2022年 | 952篇 |
2021年 | 1217篇 |
2020年 | 995篇 |
2019年 | 1205篇 |
2018年 | 1168篇 |
2017年 | 1021篇 |
2016年 | 1050篇 |
2015年 | 1179篇 |
2014年 | 1174篇 |
2013年 | 1410篇 |
2012年 | 1518篇 |
2011年 | 1514篇 |
2010年 | 1471篇 |
2009年 | 1345篇 |
2008年 | 1357篇 |
2007年 | 1266篇 |
2006年 | 1126篇 |
2005年 | 959篇 |
2004年 | 752篇 |
2003年 | 522篇 |
2002年 | 592篇 |
2001年 | 566篇 |
2000年 | 485篇 |
1999年 | 339篇 |
1998年 | 212篇 |
1997年 | 181篇 |
1996年 | 154篇 |
1995年 | 109篇 |
1994年 | 103篇 |
1993年 | 97篇 |
1992年 | 81篇 |
1991年 | 62篇 |
1990年 | 54篇 |
1989年 | 33篇 |
1988年 | 34篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1954年 | 10篇 |
1933年 | 3篇 |
1925年 | 4篇 |
1923年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Frequency-selective attenuation of sound propagaion and reverberation in shallow waterTXFrequency-selectiveattenuationofsoundp... 相似文献
92.
93.
94.
Young-Ok Kim Eun Jin Yang Jung-Hoon Kang Kyoungsoon Shin Man Chang Cheol Soo Myung 《Ocean Science Journal》2007,42(1):9-17
The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and
heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake
Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semienclosed, inner
area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. 0.4 mg L1) and high concentrations of inorganic nutrients (nitrogenous nutrients >36 μM, phosphate <4 μM) in the bottom layer. Higher
densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while
microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed
into more than 106 cells L1 at the surface layer of the inner area, while its abundance was much lower (103-104 cells L1) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p <
0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to theT. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing
of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates. 相似文献
95.
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
96.
The large cylinder is a new-type structure that has been applied to harbor and offshore engineering. An analytic method of the relationship between loads and the structure displacement is developed based on the failure mode of deep embedded large cylinder structures. It can be used to calculate directly the soil resistance and the ultirnate bearing capacity of the structure under usage. A new criterion of the large cylinder structure, which discriminates the deep embedded cylinder from the shallow embedded cylinder, is defined. Model tests prove that the proposed method is feasible for the analysis of deep embedded large cylinder structures. 相似文献
97.
98.
6个虾种基因组DNA多态性分析 总被引:2,自引:0,他引:2
采用RAPD方法检测了罗氏沼虾(Macrobrachium rosenbergii)、绿须虾(Aristeus virilis)、长毛对虾(Penaeus penicillatus)、日本对虾(P.japonicus)、斑节对虾(P.monodon)和周氏新对虾(Metapenaeus joyneri)等6个虾种的基因组DNA的多态性。用20个随机引物扩增得到492个DNA片段,根据这些片段的共享度计算出遗传距离并构建系统树。所得结果从DNA水平上反映出虾类在科属种不同分类阶元亲缘关系的远近,并为虾类现行的分类系统提供了分子生物学依据。 相似文献
99.
100.
探讨了windows编程环境下,编绘软件的网络实现方法。通过对WinSock编程方法的讨论,表明了编绘软件电子图板实现网络化编辑的可行性。 相似文献