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   19048篇
  免费   3297篇
  国内免费   1690篇
化学   13175篇
晶体学   179篇
力学   1039篇
综合类   67篇
数学   2025篇
物理学   7550篇
  2024年   63篇
  2023年   402篇
  2022年   711篇
  2021年   764篇
  2020年   740篇
  2019年   755篇
  2018年   738篇
  2017年   589篇
  2016年   983篇
  2015年   876篇
  2014年   1090篇
  2013年   1421篇
  2012年   1732篇
  2011年   1762篇
  2010年   1159篇
  2009年   1083篇
  2008年   1197篇
  2007年   1039篇
  2006年   991篇
  2005年   788篇
  2004年   602篇
  2003年   425篇
  2002年   434篇
  2001年   333篇
  2000年   276篇
  1999年   389篇
  1998年   276篇
  1997年   292篇
  1996年   284篇
  1995年   245篇
  1994年   210篇
  1993年   215篇
  1992年   143篇
  1991年   159篇
  1990年   129篇
  1989年   99篇
  1988年   88篇
  1987年   71篇
  1986年   68篇
  1985年   54篇
  1984年   57篇
  1983年   30篇
  1982年   32篇
  1981年   23篇
  1980年   26篇
  1978年   13篇
  1976年   16篇
  1975年   15篇
  1973年   15篇
  1968年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Results are presented on Omega production in central Pb+Pb collisions at 40 and 158A GeV beam energy. For the first time in heavy ion reactions, rapidity distributions and total yields were measured for the sum Omega(-) + Omega(+) at 40A GeV and for Omega(-) and Omega(+) separately at 158A GeV. The yields are strongly underpredicted by the string-hadronic UrQMD model but agree better with predictions from hadron gas models.  相似文献   
102.
103.
104.
The microstructures and magnetic properties of nanoparticles, each composed of an antiferromagnetic (AFM) manganese-oxide shell and a ferromagnetic-like core of manganese-gallium (MnGa) compounds, are studied. The coreshell structure is confirmed by transmission electron microscope (TEM). The ferromagnetic-like core contains three kinds of MnGa binary compounds, i.e., ferrimagnetic (FI) DO22-type MnaGa, ferromagnetic (FM) Mn8Gas, and AFM DO19-type Mn3Ga, of which the first two correspond respectively to a hard magnetic phase and to a soft one. Decoupling effect between these two phases is found at low temperature, which weakens gradually with increasing temperature and disappears above 200 K. The exchange bias (EB) effect is observed simultaneously, which is caused by the exchange coupling between the AFM shell and FM-like core. A large coercivity of 6.96 kOe (1Oe = 79.5775 A·m^-1) and a maximum EB value of 0.45 kOe are achieved at 300 K and 200 K respectively.  相似文献   
105.
对潜空战术导弹的水下和空中运动分别建立了纵向质心运动方程,分析了出水前后的弹体纵向特性并完成了经典方法的控制系统设计,最后分别给出了Simulink质心弹道和六自由度弹道对比仿真验证;结果表明,潜空导弹质心运动方程可简捷有效地设计期望弹道和分析弹体特性,据此设计出的控制系统可以顺利实现对潜空导弹的全程控制,提供了一套完整的潜空战术导弹纵向特性分析方法和控制系统设计方法。  相似文献   
106.
In this article, a novel dual-color quantum dot–encoded fluorescent nanoprobe was prepared by the reverse microemulsion method and layer-by-layer assembly method. First, red fluorescence–emitting CdTe quantum dots were encapsulated in silica nanoparticles by the reverse microemulsion method. Yellow fluorescence–emitting quantum dots were deposited on the surface of silica nanoparticles to form a dual-color quantum dot@silica beads/quantum dot nanoprobe. Then capture DNA was linked to a QSQ nanoprobe via covalent bonding. We utilized the quantum dot@silica beads/quantum dot nanoprobe to capture and detect the mutant BRAF DNA sequence through the competitive immunoassay method. The resulting quantum dot@silica beads/quantum dot nanoprobe-capture DNA conjugates showed sequence-specific hybridization with target DNA. Furthermore, a multispectral imaging system was utilized to distinguish the quantum dot optical code in the quantum dot@silica beads/quantum dot nanoprobe. The quantum dot@silica beads/quantum dot nanoprobe was used in human osteoblast-like HepG2 cell imaging. The proposed quantum dot@silica beads/quantum dot nanoprobe and decoding analysis method could be used for targeting imaging, biological assays, and early detection of cancer.  相似文献   
107.
Circular-rectangular groove guide is a new type of structure we have presented for coupling between circular groove guide and rectangular groove guide. In this paper, as the continuity of our previous work, the characteristic equation of circular-rectangular groove guide has been solved and the numerical results have been given and discussed.The Project Supported by National Natural Science Foundation of P. R. China  相似文献   
108.
109.
110.
The photo-detachment cross section of H^- near two parallel elastic interfaces is derived and calculated by using the closed orbit theory. The photo-detachment cross section of H^- near two interfaces is shown to exhibit multi-periodic oscillations when the distance between the H^- and the interface is varied. Each peak in the Fourier transformed photo-detachment cross section corresponds to the length of a closed orbit, which is quite similar to the case of atomic spontaneous emissions in a dielectric slab. This study provides a new understanding of the photo=detachment process of H^- in the presence of interfaces.  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