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   9677篇
  免费   301篇
  国内免费   3篇
化学   4938篇
晶体学   82篇
力学   187篇
数学   1854篇
物理学   2920篇
  2023年   63篇
  2021年   127篇
  2020年   140篇
  2019年   129篇
  2018年   217篇
  2017年   256篇
  2016年   513篇
  2015年   306篇
  2014年   373篇
  2013年   816篇
  2012年   497篇
  2011年   613篇
  2010年   419篇
  2009年   375篇
  2008年   393篇
  2007年   330篇
  2006年   285篇
  2005年   188篇
  2004年   178篇
  2003年   144篇
  2002年   154篇
  2001年   139篇
  2000年   129篇
  1999年   111篇
  1998年   129篇
  1997年   122篇
  1996年   90篇
  1995年   92篇
  1994年   81篇
  1993年   74篇
  1992年   77篇
  1991年   74篇
  1990年   68篇
  1988年   72篇
  1987年   75篇
  1986年   68篇
  1985年   100篇
  1984年   93篇
  1983年   87篇
  1982年   76篇
  1981年   80篇
  1980年   89篇
  1979年   84篇
  1978年   89篇
  1977年   92篇
  1976年   73篇
  1974年   71篇
  1973年   79篇
  1966年   67篇
  1965年   70篇
排序方式: 共有9981条查询结果,搜索用时 15 毫秒
1.
2.
JETP Letters - The results of the first run (December 2020) for the commissioning of the new superconducting synchrotron Booster at the Joint Institute for Nuclear Research are presented. Vacuum...  相似文献   
3.
Technical Physics - The effect of power-frequency (50 Hz) electromagnetic field on variation in the physicochemical properties of aluminum powders with different dispersities is studied. It is...  相似文献   
4.
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed.  相似文献   
5.
Central European Journal of Operations Research - Digital competences are among the most important competences in modern society, with the education system playing a key role in the acquisition of...  相似文献   
6.
Nonlinear Dynamics - Two types of constitutive equations consisting of instantaneous and power type hereditary contributions are proposed in order to model generalized capacitor (inductor). The...  相似文献   
7.
Czechoslovak Mathematical Journal - We give a complete characterization of closed sets F ? ?2 whose distance function dF:= dist(·, F) is DC (i.e., is the difference of two convex...  相似文献   
8.
Journal of Thermal Analysis and Calorimetry - The main energy source in marine industry is fossil fuel. Diesel engines are main power supply in sea transport at present times and will also be in...  相似文献   
9.
Journal of Thermal Analysis and Calorimetry - The structure of binary glasses xMgO·(1?x)P2O5 (x?=?0.30, 0.35, 0.40, 0.45, 0.50, and 0.55) was studied by thermodynamic model...  相似文献   
10.
A series of dinuclear half-sandwich Ru(II), Os(II) and Ir(III) complexes [Ru2(μ-Ln)(η6-pcym)2Cl2](PF6)2 ( 1 , 4 ), [Os2(μ-Ln)(η6-pcym)2Cl2](PF6)2 ( 2 , 5 ) and [Ir2(μ-Ln)(η5-Cp*)2Cl2](PF6)2 ( 3 , 6 ), based on 4,4′-biphenyl-based bridging Schiff base ligands N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)methanamine (L1; for 1 – 3 ) and N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)ethanamine (L2; for 4 – 6 ) is reported; pcym = 1-methyl-4-(propan-2-yl)benzene, Cp* = pentamethylcyclopentadienyl. The complexes were characterized by relevant analytical techniques (i.e. elemental analysis, FT-IR, NMR, ESI-MS), and their in vitro cytotoxicity was assessed at six cancerous and two non-cancerous (healthy) human cell lines. Overall, complexes 4 – 6 , containing the L2 bridging ligand, revealed higher cytotoxicity as compared with 1 – 3 and, thus, they were studied in greater detail. The best-performing complex 6 exceeded at least twice the in vitro cytotoxicity of cisplatin and showed high selectivity towards the cancer cells over the normal ones, including the primary culture of human hepatocytes. In contrast to cisplatin, complexes 4 – 6 did not induce the cell cycle modification of the treated A2780 human ovarian carcinoma cells (studied by flow cytometry and Western blot analysis). High levels of superoxide anion were induced by complexes 4 – 6 at the A2780 cells. The levels of activated forms of Caspase-3 and Caspase-8 at the A2780 cells treated by Ru(II) complex 4 were comparable with cisplatin, while complexes 5 and 6 had only a minor effect on activation of these caspases.  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