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   9398篇
  免费   857篇
  国内免费   870篇
化学   1334篇
晶体学   37篇
力学   694篇
综合类   204篇
数学   7142篇
物理学   1714篇
  2024年   10篇
  2023年   58篇
  2022年   96篇
  2021年   112篇
  2020年   168篇
  2019年   196篇
  2018年   201篇
  2017年   291篇
  2016年   325篇
  2015年   226篇
  2014年   407篇
  2013年   798篇
  2012年   492篇
  2011年   539篇
  2010年   503篇
  2009年   687篇
  2008年   653篇
  2007年   672篇
  2006年   551篇
  2005年   491篇
  2004年   467篇
  2003年   457篇
  2002年   367篇
  2001年   273篇
  2000年   272篇
  1999年   256篇
  1998年   238篇
  1997年   220篇
  1996年   176篇
  1995年   123篇
  1994年   125篇
  1993年   92篇
  1992年   81篇
  1991年   68篇
  1990年   59篇
  1989年   43篇
  1988年   31篇
  1987年   31篇
  1986年   18篇
  1985年   40篇
  1984年   25篇
  1983年   22篇
  1982年   31篇
  1981年   34篇
  1980年   21篇
  1979年   20篇
  1978年   23篇
  1977年   13篇
  1976年   7篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The aim of this paper is to present an efficient analytical and numerical procedure for solving systems of nonlinear Fredholm–Volterra integral equations of the Hammerstein type with the aid of fixed point techniques and the usual Schauder basis in an adequate Banach space.  相似文献   
72.
In this paper, we propose some su?cient conditions to obtain the existence of common fixed points for a pair of self-mappings satisfying Lipschitz-type conditions in noncomplete metric space. Our results improve and extend the results of Pant [Common fixed points of Lipschitz-type mapping pairs, J. Math. Anal. Appl. 240, (1999), 280–283] and Khan et al. [Coincidences of Lipschitz-type hybrid maps and invariant approximation, Numer. Funct. Anal. Optim. 28(9–10), (2007), 1165–1177]. As an application of our results we solve an eigenvalue problem for operators defined on a normed space.  相似文献   
73.
In this article, a multiobjective problem with a feasible set defined by inequality, equality and set constraints is considered, where the objective and constraint functions are locally Lipschitz. Several constraint qualifications are given and the relations between them are analyzed. We establish Kuhn-Tucker and strong Kuhn-Tucker necessary optimality conditions for (weak) quasi e?ciency in terms of the Clarke subdifferential. By using two new classes of generalized convex functions, su?cient conditions for local (weak) quasi e?cient are also provided. Furthermore, we study the Mond-Weir type dual problem and establish weak, strong and converse duality results.  相似文献   
74.
Recently Haezendonck–Goovaerts (H–G) risk measure has received much attention in (re)insurance and portfolio management. Some nonparametric inferences have been proposed in the literature. When the loss variable does not have enough moments, which depends on the involved Young function, the nonparametric estimator in Ahn and Shyamalkumar (2014) has a nonnormal limit, which challenges interval estimation. Motivated by the fact that many loss variables in insurance and finance could have a heavier tail such as an infinite variance, this paper proposes a new estimator which estimates the tail by extreme value theory and the middle part nonparametrically. It turns out that the proposed new estimator always has a normal limit regardless of the tail heaviness of the loss variable. Hence an interval with asymptotically correct confidence level can be obtained easily either by the normal approximation method via estimating the asymptotic variance or by a bootstrap method. A simulation study and real data analysis confirm the effectiveness of the proposed new inference procedure for estimating the H–G risk measure.  相似文献   
75.
In this paper, first, we consider the existence of a positive solution for the nonlinear fractional differential equation boundary value problem where 0≤λ < 1,CDα is the Caputo's differential operator of order α, and f:[0,1] × [0,)→[0,) is a continuous function. Using some cone theoretic techniques, we deduce a general existence theorem for this problem. Then, we consider two following more general problems for arbitrary α, 1≤n < αn + 1: Problem 1: where , 0≤λ < k + 1; Problem 2: where 0≤λα and Dα is the Riemann–Liouville fractional derivative of order α. For these problems, we give existence results, which improve recent results in the literature. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
76.
In this paper, we investigate the effect of delay on the asymptotic behavior of Nicholson's blowflies model with patch structure and multiple time‐varying delays. By using the fluctuation lemma and some differential inequality technique, delay‐dependent criteria are obtained for the global attractivity of the addressed system. Meanwhile, some numerical examples are given to illustrate the feasibility of the theoretical results. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
77.
The authors consider the difference of Reidemeister traces and difference cochain of given two self-maps,and find out a relation involving these two invariants.As an application,an inductive formula of the Reidemeister traces for self-maps on a kind of CW-complex,including spherical manifolds is obtained.  相似文献   
78.
79.
80.
This paper is concerned with the classification of non-self-adjoint second-order difference equations. The relationship between the number of summable solutions of non-self-adjoint difference equations and that of the discrete linear Hamiltonian system is discussed. A classification for non-self-adjoint second-order difference equations is established, which is independent of the choice of the rotated half plane and the fixed point.  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