首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   39827篇
  免费   7128篇
  国内免费   5895篇
化学   29303篇
晶体学   506篇
力学   2533篇
综合类   478篇
数学   4933篇
物理学   15097篇
  2024年   74篇
  2023年   717篇
  2022年   1206篇
  2021年   1387篇
  2020年   1641篇
  2019年   1683篇
  2018年   1359篇
  2017年   1349篇
  2016年   1835篇
  2015年   1938篇
  2014年   2354篇
  2013年   2980篇
  2012年   3566篇
  2011年   3778篇
  2010年   2699篇
  2009年   2687篇
  2008年   2864篇
  2007年   2442篇
  2006年   2331篇
  2005年   1941篇
  2004年   1595篇
  2003年   1279篇
  2002年   1345篇
  2001年   1097篇
  2000年   892篇
  1999年   870篇
  1998年   662篇
  1997年   632篇
  1996年   569篇
  1995年   485篇
  1994年   416篇
  1993年   373篇
  1992年   258篇
  1991年   272篇
  1990年   232篇
  1989年   189篇
  1988年   161篇
  1987年   116篇
  1986年   96篇
  1985年   96篇
  1984年   66篇
  1983年   58篇
  1982年   63篇
  1981年   37篇
  1980年   25篇
  1979年   16篇
  1978年   10篇
  1976年   18篇
  1975年   16篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
1.
Zhang  Hongchi  Liu  Rui  Li  Hui  Yang  Yang  Zhou  Feng 《Chemistry of Natural Compounds》2022,58(3):541-544
Chemistry of Natural Compounds -  相似文献   
2.
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom.  相似文献   
3.
4.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results.  相似文献   
5.
Sun  J.  Yuan  H. 《Experimental Mechanics》2021,61(3):565-580
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients...  相似文献   
6.
Huang  Renpei  Chen  Li  Yuan  Xiaoru 《显形杂志》2021,24(2):317-330
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts...  相似文献   
7.
8.
Li  Jun  Zheng  Dayong  Wei  Ning  Sun  Yunfeng  Liu  Li  Yuan  Yuan  Jiang  Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3)....  相似文献   
9.
Sun  Yekai  Yuan  Jie  Vizzaccaro  Alessandra  Salles  Loïc 《Nonlinear dynamics》2021,104(4):3077-3107
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative...  相似文献   
10.
Yu  Yangyang  Li  Jiajia  Yuan  Zhixuan  Fan  Yongchen  Wu  Ying 《Nonlinear dynamics》2022,109(4):3113-3132
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号