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   3407篇
  免费   276篇
  国内免费   325篇
化学   353篇
晶体学   18篇
力学   293篇
综合类   89篇
数学   2583篇
物理学   672篇
  2024年   2篇
  2023年   41篇
  2022年   49篇
  2021年   48篇
  2020年   70篇
  2019年   85篇
  2018年   77篇
  2017年   87篇
  2016年   91篇
  2015年   72篇
  2014年   130篇
  2013年   258篇
  2012年   129篇
  2011年   131篇
  2010年   169篇
  2009年   208篇
  2008年   215篇
  2007年   246篇
  2006年   210篇
  2005年   206篇
  2004年   176篇
  2003年   175篇
  2002年   166篇
  2001年   138篇
  2000年   147篇
  1999年   114篇
  1998年   109篇
  1997年   93篇
  1996年   79篇
  1995年   57篇
  1994年   60篇
  1993年   22篇
  1992年   28篇
  1991年   14篇
  1990年   17篇
  1989年   14篇
  1988年   7篇
  1987年   10篇
  1986年   2篇
  1985年   5篇
  1984年   12篇
  1983年   6篇
  1982年   4篇
  1981年   4篇
  1980年   9篇
  1979年   6篇
  1978年   4篇
  1977年   2篇
  1970年   1篇
  1936年   1篇
排序方式: 共有4008条查询结果,搜索用时 31 毫秒
101.
We study a simple model based upon the Lucas framework where heterogeneous agents behave rationally in a fully intertemporal setting but do not know other investors' personal preferences, wealth or investment portfolios. As a consequence, agents initially do not know the equilibrium asset pricing function and must make guesses, which they update via adaptive learning with constant gain. We demonstrate that even in this simple environment the economy can, depending on parameters, exhibit either stable convergence to equilibrium, or chaotic dynamical behavior of asset prices and trading volume without converging to the rational expectations equilibrium of the Lucas model. This contradicts the assertion that the Lucas model is stable in the face of modest deviations from the strong assumptions required to compute the equilibrium. © 2013 Wiley Periodicals, Inc. Complexity 19: 38–55, 2014  相似文献   
102.
In this paper, we prove a conjecture by T. Suzuki, which says if a smooth Fano manifold satisfies some positivity condition on its Chern characters, then it can be covered by rational N-folds. We prove this conjecture by using purely combinatorial properties of Bernoulli numbers.  相似文献   
103.
Terpolymers based on propylene with 1‐pentene and 1‐hexene as comonomeric units are satisfactorily synthesized using a metallocene catalyst. Thus, several terpolymers are prepared with distinct overall compositions in comonomers as well as three different 1‐pentene/1‐hexene ratios at a given composition to evaluate the influence on polymerization activity, intrinsic viscosity, and microstructural details. The new trigonal δ polymorph is observed in those quenched terpolymers with a global content in comonomers of about 14 mol %, independently of the ratio between both comonomers. However, preliminary results indicate a profound influence of that ratio on the crystallization rate. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3251–3259  相似文献   
104.
对于一类00型或∞0型未定式,给出其极限为1的一个充分条件,并通过实例展示其应用。  相似文献   
105.
106.
本文对二道全国大学生数学竞赛决赛试题(数学类)给予了诠释与解析.  相似文献   
107.
Pin Han  Hone-Ene Hwang 《Optik》2009,120(16):809-813
The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented.  相似文献   
108.
We extend the notion and basic properties of quadratic differential divisors to a Klein surface, using the corresponding form’s divisors from the double cover of the Klein surface.  相似文献   
109.
110.
From a viewpoint of physical and chemical form estimation, ultra-trace analytical techniques of nuclear materials in environmental samples for safeguards have been investigated at Japan Atomic Energy Research Institute. This article deals with (1) an outline of the developed techniques for bulk and particle analyses of uranium and plutonium in the safeguards environmental samples; (2) current R&D on techniques relating to estimation of the physical and chemical form, such as SEM images and EDX spectra for fine particles of nuclear materials and fission track observation applicable to fissile materials; and (3) possible analytical methodologies, as future works, applicable to ultra-trace amounts of nuclear materials in environmental samples.  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