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   24091篇
  免费   4719篇
  国内免费   3533篇
化学   18011篇
晶体学   348篇
力学   1404篇
综合类   267篇
数学   2918篇
物理学   9395篇
  2024年   54篇
  2023年   565篇
  2022年   727篇
  2021年   1018篇
  2020年   1177篇
  2019年   1212篇
  2018年   954篇
  2017年   894篇
  2016年   1238篇
  2015年   1398篇
  2014年   1589篇
  2013年   1926篇
  2012年   2302篇
  2011年   2333篇
  2010年   1621篇
  2009年   1679篇
  2008年   1737篇
  2007年   1448篇
  2006年   1326篇
  2005年   1065篇
  2004年   860篇
  2003年   653篇
  2002年   719篇
  2001年   540篇
  2000年   465篇
  1999年   442篇
  1998年   352篇
  1997年   296篇
  1996年   272篇
  1995年   224篇
  1994年   188篇
  1993年   197篇
  1992年   134篇
  1991年   117篇
  1990年   103篇
  1989年   99篇
  1988年   84篇
  1987年   55篇
  1986年   56篇
  1985年   61篇
  1984年   38篇
  1983年   21篇
  1982年   26篇
  1981年   13篇
  1980年   5篇
  1979年   9篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
  1972年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Baik  Jinho  Lee  Ji Oon  Wu  Hao 《Journal of statistical physics》2018,173(5):1484-1522
Journal of Statistical Physics - We consider the spherical spin glass model defined by a combination of the pure 2-spin spherical Sherrington–Kirkpatrick Hamiltonian and the ferromagnetic...  相似文献   
972.
973.
We investigate the Cauchy problem of a multidimensional chemotaxis model with initial data in critical Besov spaces. The global existence and uniqueness of the strong solution is shown for initial data close to a constant equilibrium state.  相似文献   
974.
975.
Abstract . The solvothermal reaction between cuprous iodide and the rigid triangular imidazole ligand in mixed N,N′‐dimethylacetamide (DMA)‐acetonitrile solvent leads to the isolation of the 3D metal‐organic framework [(Cu4I4)3(TIPA)4] · 7DMA ( 1 ) [TIPA = tri(4‐imidazolylphenyl) amine], which was characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Topologically, the structure of 1 is an unprecedented 3,3,4,4‐connected net with a point symbol of {4.8.10}2{4.82}2{42.82.102}2{84.122}. Compound 1 exhibits orange‐red photoluminescence with an emission maximum at 622 nm at room temperature.  相似文献   
976.
977.
The moving particle semi‐implicit (MPS) method has been widely applied in free surface flows. However, the implementation of MPS remains limited because of compressive instability occurred when the particles are under compressive stress states. This study proposed an inter‐particle force stabilization and consistency restoring MPS (IFS‐CR‐MPS) method to overcome this numerical instability. For inter‐particle force stabilization, a hyperbolic‐shaped quintic kernel function is developed with a non‐negative and smooth second order derivative to satisfy the stability criterion under compressive stress state. Then, a contrastive study is conducted on the contradiction between the common understanding of the conventional MPS hyperbolic‐shaped kernel function and its performance. The result shows that the conventional MPS hyperbolic‐shaped kernel function can easily cause violent repulsive inter‐particle force and then lead to the compressive instability. Therefore, the first order derivative of the modified hyperbolic‐shaped quintic kernel function is recommended as the form of the contribution of the neighbor particles to achieve a more stable inter‐particle repulsive force. For consistency restoring, the Taylor series expansion and the hyperbolic‐shaped quintic kernel are combined to improve the accuracy of the viscosity and pressure calculation. The IFS‐CR‐MPS algorithm is subsequently verified by the inviscid hydrostatic pressure, jet impacting, and viscous droplet impacting problems. These results can be used for choosing kernel function and the contribution of neighbor particles in particle methods. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
978.
The metal-catalyzed Baeyer-Villiger oxidation of cyclohexanone with molecular oxygen (latm) in the presence of benzaldehyde gives δ -caprolactone in high yield. The same oxidation in the absence of metal catalysts is also studied. Additives to the system can improve the reaction highly efficiently.  相似文献   
979.
980.
In this report, a palladium-catalyzed redox-relay Heck process to access optically active alkenylated α,β-unsaturated lactams is described. Under mild reaction conditions, electron-deficient alkenyl triflates and electron-rich alkenyl iodonium salts undergo enantioselective and site-selective coupling with enelactams to deliver the products in high yields and excellent enantioselectivities. Furthermore, the products allow facile access to natural products such as (+)-calvine and (+)-2-epicalvine in addition to the bioactive molecule aza-goniothalamin.  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