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   592113篇
  免费   31215篇
  国内免费   21314篇
化学   328643篇
晶体学   9070篇
力学   27680篇
综合类   412篇
数学   70488篇
物理学   208349篇
  2021年   4947篇
  2020年   5698篇
  2019年   6524篇
  2018年   7876篇
  2017年   8489篇
  2016年   11999篇
  2015年   8919篇
  2014年   11981篇
  2013年   28118篇
  2012年   22376篇
  2011年   27926篇
  2010年   23342篇
  2009年   23170篇
  2008年   24158篇
  2007年   23512篇
  2006年   21926篇
  2005年   20389篇
  2004年   19881篇
  2003年   17071篇
  2002年   16764篇
  2001年   18693篇
  2000年   14112篇
  1999年   11725篇
  1998年   9756篇
  1997年   9320篇
  1996年   9394篇
  1995年   8937篇
  1994年   8826篇
  1993年   8763篇
  1992年   9081篇
  1991年   8818篇
  1990年   8233篇
  1989年   8230篇
  1988年   8144篇
  1987年   7498篇
  1986年   7180篇
  1985年   8828篇
  1984年   9108篇
  1983年   7086篇
  1982年   7735篇
  1981年   7488篇
  1980年   7133篇
  1979年   7369篇
  1978年   7608篇
  1977年   7471篇
  1976年   7702篇
  1975年   6666篇
  1974年   6570篇
  1973年   6892篇
  1972年   4885篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
在本文中,我们证明了具有次亚B性质的ωα+1-紧T1空间是ωα-Lindel?f空间,此结果改进并推广了[1]中的主要结果。  相似文献   
992.
Magnetic Properties of the Cobaltates Na6CoS4, Na6CoSe4, and K6CoS4 The alkali metal cobalt chalcogenides Na6CoS4, Na6CoSe4, and K6CoS4 crystallize in the space group P63mc with Z = 4. The structure is characterized by isolated [CoX4]-tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. The deviations at low temperatures are caused by antiferromagnetic interactions. The magnetic moments are discussed with regard to ligand-field parameters.  相似文献   
993.
The electrochemical behavior of the copper-tyrosine complex has been studied by linear-sweep adsorption voltammetry. In 0.02 mol/L Na2HPO4 buffer solution (pH=9.6), the complex can be adsorped on a hanging mercury drop electrode and reduced at a peak potential of about –0.42 V (vs. SCE). The secondary derivative peak height is linear proportional to the concentration of tyrosine in the range 1.0×10–7–5.0×10–5 mol/L. The detection limit is 5×10–8 mol/L.Project supported by the Provincial Science Foundation of Shandong Province  相似文献   
994.
Modified Stern-Volmer equation is obeyed by bovine serum albumin (BSA)-iodide system showing selective quenching of tryptophanyl fluorescence of BSA. The fraction of accessible protein fluorescence is 0.56 and the effective Stern-Volmer constant is 290 M-1 at pH 7.4 in 0.005 M phosphate buffer at 25°C. Collisional quenching is operative both in the BSA -I−1 system and the model system, tryptophan-I−1. It is supported by the observed relationship between the ratio of quenching rate constants (k q ) and diffusion coefficients and alsok q with bulk viscosity.  相似文献   
995.
Plasma Chemistry and Plasma Processing - Nonequilibrium nitrogen dissociation-recombination kinetics in the boundary layer and on the surface of a solid body during hypersonic flow. the subsequent...  相似文献   
996.
We study the conjugate boundary-value problem with boundary conditions whose orders can be as large as the order of the differential equation or larger. We construct the Green's function of the problem over the entire space when the separating surface is a hyperplane, and we describe its properties. Bibliography: 6 titles.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 30, 1989, pp. 20–24.  相似文献   
997.
998.
Barium ferrite particulates prepared by a salt-melt method   总被引:1,自引:0,他引:1  
Barium ferrite particulates have been prepared by coprecipitation and calcination in a flux of NaCl-KCl. It was found that a flux containing more than 30 wt% KCl tends to seriously deteriorate the magnetic properties of resultant perticulates. The flux with 10 wt% KCl or less showed promising results. A Ba(CoZr)0.75Fe10.5O19 particulate showed the best properties, i.e., a saturation magnetization of 68.5, a squareness ratio of 0.49, and a coercivity of 1280 Oe, when calcined in NaCl at 900°C for 4 h.  相似文献   
999.
A. V. Pomyalov  I. Laulicht  J. Barak 《Physica A》1993,200(1-4):267-277
The microwave subsidiary absorption threshold in tangentially magnetized yttrium-iron-garnet (YIG) films was measured as a function of the static magnetic field, film thickness and decrease in the 0.3–3 μm range is observed. The effect is explained quantitatively by using modified Damon-Eshbach dispersion relations which take into account exchange interactions.

The effect of temperature on hcrit, the smallest threshold field amplitude, in the 250<T< 450 K temperature range can be expressed by an empirical relationship hcrit Ms(T)-1.6 where Ms is the saturation magnetization. This hcrit vs Ms relationship is similar to that obtained for the magnetization dependence of parallel pump thresholds in Li-Ti ferrite compounds.  相似文献   

1000.
We discuss the possible new electroweak interactions which may be generated by the Higgs sector at the scale of theZ mass. For this purpose, we give a set ofSU(2)×U(1) gauge invariant operators constructed in terms ofW, Z, γ and Higgs fields which in the unitary gauge describe all possible γWW andZWW anomalous couplings. The dimension of these operators varies from 6 to 12. This fact allows us to consider various scenaria for the manifestations of the New Physics. We conclude that the underlying dynamics induced by the Higgs sector can be tested through a model-independent amplitude analysis of gauge boson pair production at LEP2 and future colliders.  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