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   10646篇
  免费   2004篇
  国内免费   1036篇
化学   7113篇
晶体学   85篇
力学   680篇
综合类   96篇
数学   1238篇
物理学   4474篇
  2024年   10篇
  2023年   245篇
  2022年   246篇
  2021年   373篇
  2020年   444篇
  2019年   430篇
  2018年   361篇
  2017年   351篇
  2016年   533篇
  2015年   497篇
  2014年   581篇
  2013年   773篇
  2012年   956篇
  2011年   1069篇
  2010年   658篇
  2009年   697篇
  2008年   686篇
  2007年   590篇
  2006年   549篇
  2005年   451篇
  2004年   359篇
  2003年   290篇
  2002年   259篇
  2001年   210篇
  2000年   219篇
  1999年   205篇
  1998年   210篇
  1997年   194篇
  1996年   158篇
  1995年   201篇
  1994年   171篇
  1993年   131篇
  1992年   104篇
  1991年   89篇
  1990年   95篇
  1989年   66篇
  1988年   42篇
  1987年   35篇
  1986年   37篇
  1985年   23篇
  1984年   19篇
  1983年   20篇
  1982年   12篇
  1981年   6篇
  1980年   10篇
  1979年   2篇
  1978年   4篇
  1975年   3篇
  1974年   2篇
  1957年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This paper considers a stochastic variational inequality problem (SVIP). We first formulate SVIP as an optimization problem (ERM problem) that minimizes the expected residual of the so-called regularized gap function. Then, we focus on a SVIP subclass in which the function involved is assumed to be affine. We study the properties of the ERM problem and propose a quasi-Monte Carlo method for solving the problem. Comprehensive convergence analysis is included as well. This work was supported in part by SRF for ROCS, SEM and Project 10771025 supported by NSFC.  相似文献   
992.
993.
Porous carbon counter electrodes have been fabricated at low temperature by coating an organic binder free carbon slurry onto F-doped tin oxide conducting glass. The carbon slurry is prepared by ball-milling a dispersion of activated carbon in aqueous SnCl4 solution. During ball-milling, SnCl4 hydrolyzes and transforms into stannic acid gel, which acts as an inorganic “glue” to connect the carbon particles during film preparation. Dye-sensitized solar cells employing this carbon electrode achieve efficiency as high as 6.1% which is comparable to that of the cells using sputtering Pt as counter electrode.  相似文献   
994.
It is shown that every non-compact hyperbolic manifold of finite volume has a finite cover admitting a geodesic ideal triangulation. Also, every hyperbolic manifold of finite volume with non-empty, totally geodesic boundary has a finite regular cover which has a geodesic partially truncated triangulation. The proofs use an extension of a result due to Long and Niblo concerning the separability of peripheral subgroups.

  相似文献   

995.
Zhang  Wei-Wei  Luo  Jian-Guang  Wang  Jun-Song  Lu  Yuan-Yuan  Kong  Ling-Yi 《Chromatographia》2009,70(11):1635-1643

Qualitative characterization and quantitative analysis of labdane diterpenoids from Coleus forskohlii have been achieved by liquid chromatography hyphenated with photodiode-array detection and tandem electrospray ionization mass spectrometry (LC–DAD–ESI-MSn). By use of this method, thirteen forskolin-type diterpenoids were identified in the crude extract on the basis of their fragmentation mechanisms. Fragmentation rules were deduced from nine forskolin-type standards by ESI-MS in positive-ion mode. It was found that fragmentation behavior varied with the position and number of the substituents on the skeleton; this could be used for convenient identification of this type of compound. Six marker diterpenoids were also quantified, and the quality of both the cultivated and wild plants was evaluated.

  相似文献   
996.
Luo  Yun  Li  Yi  Lv  Baoqiang  Zhou  Zaide  Xiao  Dan  Choi  Martin M. F. 《Mikrochimica acta》2009,164(3-4):411-417
Microchimica Acta - A new luminol derivative has been synthesized and its fluorescence has been studied. The luminol derivative emits at 460 nm in pH 10.0 phosphate buffer which is...  相似文献   
997.
998.
磁光图像显示Bi-2223/Ag带材中单根超导芯的宽面两侧边缘分布有较大的超导电流密度,Bi-2223单根超导芯的横截面是纺锤形的,单位宽度上的横截面面积之比与电流密度在横截面上不同部分的分布之比相当,高的电流密度在单根超导芯两则的分布可能是由单芯横截面的形状引起的。  相似文献   
999.
The energy increment spectrum method is developed for the numerical prediction of the appearance and disappearance of a primary (2M: 1)-librational or (M: 1)-rotational resonant separatrix band in a parametrically excited pendulum. The analytical conditions for the presence of such separatrix bands are also obtained. Illustrations of the analytical and numerical results for the appearance and destruction of the resonant bands are given for a comparison.  相似文献   
1000.
We calculated the contributions of the two-particle one-hole (2p-1h) and the one-particle two-hole (1p-1h) excitations to the imaginary partW(E, R) of then-40Ca optical potential. The bound single particle states and energies of the40Ca nucleus are calculated quantum mechanically by solving the Schrödinger equation with a Woods-Saxon potential. For the excited states in the continuum we use the Thomas-Fermi approximation. Different forms of contact residual interactions have been tested. A combination of aδ-force and a smeared SDI can fit the phenomenologicalW(E, R).  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