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   5312篇
  免费   548篇
  国内免费   423篇
化学   666篇
晶体学   32篇
力学   2012篇
综合类   84篇
数学   1704篇
物理学   1785篇
  2024年   11篇
  2023年   55篇
  2022年   86篇
  2021年   80篇
  2020年   148篇
  2019年   115篇
  2018年   160篇
  2017年   166篇
  2016年   201篇
  2015年   181篇
  2014年   243篇
  2013年   468篇
  2012年   200篇
  2011年   266篇
  2010年   184篇
  2009年   229篇
  2008年   264篇
  2007年   328篇
  2006年   312篇
  2005年   256篇
  2004年   265篇
  2003年   232篇
  2002年   229篇
  2001年   193篇
  2000年   196篇
  1999年   192篇
  1998年   166篇
  1997年   126篇
  1996年   108篇
  1995年   101篇
  1994年   95篇
  1993年   65篇
  1992年   66篇
  1991年   75篇
  1990年   36篇
  1989年   28篇
  1988年   27篇
  1987年   23篇
  1986年   19篇
  1985年   20篇
  1984年   10篇
  1983年   8篇
  1982年   7篇
  1981年   10篇
  1980年   4篇
  1979年   6篇
  1978年   6篇
  1977年   4篇
  1976年   6篇
  1957年   3篇
排序方式: 共有6283条查询结果,搜索用时 15 毫秒
81.
提出大型液相色谱分离过程FAD-SMT数学模型,把色谱分离连续性方程转变为对流扩散方程和常微分方程组,并提出模型的数值方法,分析了数值解的稳定条件和收敛条件以及空间和时间步长的选取。实验结果表明,FAD-SMT数学模型计算的液相色谱分离葡萄糖、果糖和分离甘露醇、山梨醇理论与实验流出曲线相吻合。灵敏度分析结果表明:相平衡常数比轴向扩散系数和总传质系数对色谱分离有较大的影响。  相似文献   
82.
Given n samples(viewed as an n-tuple) of a γ-regular discrete distribution π,in this article the authors concern with the weighted and unweighted graphs induced by the n samples. They first prove a series of SLLN results(of Dvoretzky-Erd¨os’ type). Then they show that the vertex weights of the graphs under investigation obey asymptotically power law distributions with exponent 1 + γ. They also give a conjecture that the degrees of unweighted graphs would exhibit asymptotically power law distribu...  相似文献   
83.
In this paper we establish the existence of the minimal large positive solution for a general class of nonlinear cooperative systems including the simplest prototype of García-Melián et al. (2016). Precisely, based on the existence of a large positive supersolution, we can infer the existence of the minimal large positive solution. Moreover, we also give some sufficient easily computable conditions for the existence of a large positive supersolution. Our results generalize, very substantially, some of the findings of García-Melián et al. (2016) adopting a rather novel methodology.  相似文献   
84.
1 Introduction and Main Results Consider the first Piola-Kirchhoff stress P defined as[1]P(F)=?W(F)/?F,(1.1)where F and W refer to the deformation tensor and strain energy density.Due to the principle of material frame-indifference and the material symmetry,two important constraints should be satisfied by these relations[1].  相似文献   
85.
The hysteresis of sorptive deformation of sorbents has been studied for the first time. Based on the results obtained, it is assumed that the deformation of sorbents could be the universal reason for the sorptive hysteresis.For Part 1, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1477–1479, August, 1995.  相似文献   
86.
Let(X i ) be a martingale difference sequence. LetY be a standard normal random variable. We investigate the rate of uniform convergence
  相似文献   
87.
We establish the large deviation principle (LDP) for the virtual waiting time and queue length processes in the GI/GI/1 queue. The rate functions are found explicitly. As an application, we obtain the logarithmic asymptotics of the probabilities that the virtual waiting time and queue length exceed high levels at large times. Additional new results deal with the LDP for renewal processes and with the derivation of unconditional LDPs for conditional ones. Our approach applies in large deviations ideas and methods of weak convergence theory.This work was supported in part by AT&T Bell Labs.  相似文献   
88.
From the measurements of surface potentials of quartz capillaries before and after adsorption of poly(ethylene oxides) (PEO) of various molecular mass, an assessment of the equilibrium hydrodynamic thickness of the adsorption layers has been obtained. The results have been compared with those of independent measurements of . The flow of the polymer solution under increasing pressure drops at the ends of a capillary, which causes the corresponding shear stress () on the surface of adsorbed PEO layers, results in the deformation of the latter, which manifests itself in decreasing 5. The values decrease by several times when the shear stress rises to 2×102 N m–2. Such values of have been obtained using thin capillaries (r = 5÷6 mm) and by application of the capillary electrokinetic method with pressure drops up to 5÷6 MPa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 31–37, January, 1994.  相似文献   
89.
IfB is a weakly compactly generated Banach space andf: (S,S, ) satisfies the strong law of large numbers, thenf=f 1+f 2, wheref 1 is Bochner -integrable andf 2 is Pettis -integrable with Pettis norm 0. The decomposition is unique.  相似文献   
90.
Some fifteen years ago, Shuler formulated three conjectures relating to the large-time asymptotic properties of a nearest-neighbor random walk on 2 that is allowed to make horizontal steps everywhere but vertical steps only on a random fraction of the columns. We give a proof of his conjectures for the situation where the column distribution is stationary and satisfies a certain mixing codition. We also prove a strong form of scaling to anisotropic Brownian motion as well as a local limit theorem. The main ingredient of the proofs is a large-deviation estimate for the number of visits to a random set made by a simple random walk on . We briefly discuss extensions to higher dimension and to other types of random walk.Dedicated to Prof. K. E. Shuler on the occasion of his 70th birthday, celebrated at a Symposium in his honor on July 13, 1992, at the University of California at San Diego, La Jolla, California.  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