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   5935篇
  免费   544篇
  国内免费   454篇
化学   230篇
晶体学   1篇
力学   966篇
综合类   135篇
数学   4633篇
物理学   968篇
  2023年   50篇
  2022年   44篇
  2021年   63篇
  2020年   135篇
  2019年   114篇
  2018年   130篇
  2017年   175篇
  2016年   143篇
  2015年   120篇
  2014年   274篇
  2013年   457篇
  2012年   226篇
  2011年   430篇
  2010年   304篇
  2009年   355篇
  2008年   408篇
  2007年   372篇
  2006年   352篇
  2005年   321篇
  2004年   265篇
  2003年   283篇
  2002年   253篇
  2001年   197篇
  2000年   187篇
  1999年   186篇
  1998年   194篇
  1997年   160篇
  1996年   108篇
  1995年   91篇
  1994年   90篇
  1993年   61篇
  1992年   48篇
  1991年   33篇
  1990年   39篇
  1989年   21篇
  1988年   24篇
  1987年   26篇
  1986年   22篇
  1985年   17篇
  1984年   27篇
  1983年   11篇
  1982年   25篇
  1981年   21篇
  1980年   14篇
  1979年   7篇
  1978年   12篇
  1977年   7篇
  1976年   6篇
  1973年   6篇
  1936年   4篇
排序方式: 共有6933条查询结果,搜索用时 337 毫秒
41.
We introduce strong derivative, the corresponding Z-integrable and other related concepts. Also, we give an improved version of the fundamental theorem of calculus.  相似文献   
42.
In this work two non-local problems for the parabolic-hyperbolic type equation with non-characteristic line of changing type are considered. Unique solvability of these problems is proven. The uniqueness of the solution is proven by the method of energy integrals and the existence is proven by the method of integral equations.  相似文献   
43.
A complete boundary integral formulation for compressible Navier–Stokes equations with time discretization by operator splitting is developed using the fundamental solutions of the Helmholtz operator equation with different order. The numerical results for wall pressure and wall skin friction of two‐dimensional compressible laminar viscous flow around airfoils are in good agreement with field numerical methods. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
44.
关于多线性振荡奇异积分在加权Hardy-型空间上的一致估计   总被引:1,自引:0,他引:1  
吴丛明  杨大春 《数学进展》2002,31(6):527-536
本文对一类具有光滑位相函数的多线性振荡奇异积分算子建立了一致的加权(H^1(R^n),L^1(R^n))估计及一致的加权(HKp(R^n),Kp(R^n)估计。  相似文献   
45.
By an elementary calculation we obtain the exact mean values of Minkowksi functionals for a standard model of percolating sets. In particular, a recurrence theorem for the mean Euler characteristic recently put forward is shown to be incorrect. Related previous mathematical work is mentioned. We also conjecture bounds for the threshold density of continuum percolation, which are associated with the Euler characteristic.  相似文献   
46.
Positive and Nontrivial Solutions for the Urysohn Integral Equation   总被引:1,自引:0,他引:1  
We establish new criteria for the existence of either positive or nonzero solutions of the Urysohn integral equation. We also discuss the existence of an interval of positive eigenvalues and sufficient conditions for the existence of at least a positive eigenvalue with a nonzero or positive eigenfunction for the Urysohn integral operator. Among others, we employ techniques based on fixed point index theory for compact maps, which are new for this type of equation.  相似文献   
47.
Summary We study the integration theory for general integral metrics when restricted to upper integrals q, finding improvements in the relation between the classes of the q-integrable and the ql-integrable functions. We give new results and notions which lead to the desirable characterizations of q-integrable functions as ql-integrable f with q(|f|) < ∞, and of ql-integrable functions via the integrability of their upper truncations, under natural conditions which are fulfilled in most finitely additive integration theories.  相似文献   
48.
Let μ+(t) and μ(t) be the locations of the maximum and minimum, respectively, of a standard Brownian motion in the interval [0,t]. We establish a joint integral test for the lower functions of μ+(t) and μ(t), in the sense of Paul Lévy. In particular, it yields the law of the iterated logarithm for max(μ+(t),μ(t)) as a straightforward consequence. Our result is in agreement with well-known theorems of Chung and Erdős [(1952) Trans. Amer. Math. Soc. 72, 179–186.], and Csáki, F?ldes and Révész [(1987) Prob. Theory Relat. Fields 76, 477–497].   相似文献   
49.
The application of multi-attribute utility theory based on the Choquet integral requires the prior identification of a capacity if the utility scale is unipolar, or of a bi-capacity if the utility scale is bipolar. In order to implement a minimum distance principle for capacity or bi-capacity approximation or identification, quadratic distances between capacities and bi-capacities are studied. The proposed approach, consisting in solving a strictly convex quadratic program, has been implemented within the GNU R kappalab package for capacity and nonadditive integral manipulation. Its application is illustrated on two examples.   相似文献   
50.
We review the Lorentz-covariant approach to loop quantum gravity. This approach solves the Immirzi parameter problem occurring in the standard loop approach based on the SU(2) gauge group. We show that there exists a unique loop quantization preserving all the classical symmetries at the quantum level and that the results obtained with it, such as the area operator spectrum, are independent of the Immirzi parameter. The standard SU(2) approach violates the diffeomorphism invariance and is therefore an incorrect quantization of gravity.  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