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   214809篇
  免费   43254篇
  国内免费   29468篇
化学   142457篇
晶体学   2274篇
力学   14519篇
综合类   805篇
数学   26423篇
物理学   101053篇
  2024年   827篇
  2023年   3533篇
  2022年   5609篇
  2021年   5751篇
  2020年   6656篇
  2019年   6696篇
  2018年   6140篇
  2017年   6178篇
  2016年   8874篇
  2015年   8852篇
  2014年   10147篇
  2013年   14305篇
  2012年   16530篇
  2011年   18011篇
  2010年   17179篇
  2009年   17035篇
  2008年   11921篇
  2007年   10551篇
  2006年   9669篇
  2005年   8669篇
  2004年   7994篇
  2003年   6391篇
  2002年   5870篇
  2001年   5790篇
  2000年   4757篇
  1999年   5355篇
  1998年   4546篇
  1997年   4359篇
  1996年   4654篇
  1995年   4657篇
  1994年   4469篇
  1993年   4212篇
  1992年   3698篇
  1991年   3206篇
  1990年   2706篇
  1989年   2580篇
  1988年   2395篇
  1987年   1629篇
  1986年   1667篇
  1985年   1273篇
  1984年   1239篇
  1983年   553篇
  1982年   1046篇
  1981年   845篇
  1980年   862篇
  1979年   573篇
  1978年   561篇
  1977年   673篇
  1976年   1071篇
  1972年   543篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results.  相似文献   
2.
Li  Zhixiang  Zhao  Zhen  Liu  Caishan  Wang  Qingyun 《应用数学和力学(英文版)》2021,42(11):1571-1580
Applied Mathematics and Mechanics - Spiral springs have a wide range of applications in various fields. As a result of the complexity of friction, few theoretical analyses of spring belts under...  相似文献   
3.
Kobayashi  M.  Zhang  Y.  Ishikawa  H.  Sun  J.  Oddershede  J.  Juul Jensen  D.  Miura  H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such...  相似文献   
4.
Liu  Jingze  Fei  Qingguo  Wu  Shaoqing  Tang  Zhenhuan  Zhang  Dahai 《Nonlinear dynamics》2021,106(3):1869-1890
Nonlinear Dynamics - Rolling bearing and squeeze film damper will introduce structural nonlinearity into the dynamic model of aeroengine. Rubbing will occur due to the clearance reduction design of...  相似文献   
5.
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...  相似文献   
6.
Xu  Mengtao  Li  Changyou  Sun  Yang  Yang  Tianzhi  Zhang  Hongzhuang  Liu  Zhendong  Liu  Haiyang  Li  Zhenyuan  Zhang  Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are...  相似文献   
7.
8.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results.  相似文献   
9.
10.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  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