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   610535篇
  免费   4642篇
  国内免费   1479篇
化学   307138篇
晶体学   8731篇
力学   31529篇
综合类   24篇
数学   81703篇
物理学   187531篇
  2021年   5644篇
  2020年   6102篇
  2019年   6969篇
  2018年   9450篇
  2017年   9603篇
  2016年   13049篇
  2015年   6945篇
  2014年   11783篇
  2013年   26607篇
  2012年   20658篇
  2011年   24662篇
  2010年   18655篇
  2009年   18655篇
  2008年   23401篇
  2007年   23185篇
  2006年   21059篇
  2005年   18802篇
  2004年   17629篇
  2003年   15899篇
  2002年   15886篇
  2001年   17105篇
  2000年   13141篇
  1999年   10150篇
  1998年   8844篇
  1997年   8664篇
  1996年   8057篇
  1995年   7291篇
  1994年   7249篇
  1993年   7056篇
  1992年   7433篇
  1991年   8031篇
  1990年   7659篇
  1989年   7626篇
  1988年   7392篇
  1987年   7205篇
  1986年   6887篇
  1985年   8798篇
  1984年   9109篇
  1983年   7716篇
  1982年   8001篇
  1981年   7511篇
  1980年   7073篇
  1979年   7733篇
  1978年   8044篇
  1977年   7970篇
  1976年   7958篇
  1975年   7636篇
  1974年   7429篇
  1973年   7785篇
  1972年   5805篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
We recorded vibrational spectra of the CO poison resulting from the electrochemical decomposition of CH3OH on platinum by sum-frequency generation using the infrared free electron laser CLIO. At high CH3OH concentration (0.1 M) in the electrolyte, both multi-bonded and linearly bonded CO are equally present. At lower CH3OH concentration (0.004 M), the multi-bonded species is predominant. The CO poison still remains on the surface at potentials (0.05 V/NHE) close to the hydrogen evolution onset.  相似文献   
993.
The literature on the synthesis of heterocyclic compounds from aliphatic nitro derivatives in the past decade has been summarized.Moscow State Textile Academy, 117918, Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1336, October, 1994. Original article submitted October 6, 1994.  相似文献   
994.
We study the propagation of phase space singularities for the time dependent Schrödinger equation with potential having Coulomb-type singularities in space dimension equal tothree. We prove that the singularities (frequency set) of the solution are reflected by a Coulomb center exactly as in the classical problem, i.e. the frequency set follows theregularized trajectories of Classical Mechanics after a collision.  相似文献   
995.
We consider the application of the fictitious region method to solve the first and second boundary-value problems for a second-order quasilinear elliptical equation. Rate of convergence bounds are obtained for two versions of the fictitious region method.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 7–14, 1985  相似文献   
996.
997.
998.
A new approach to calculating the temperatures of boiling at atmospheric pressure (T b) of organic compounds from arbitrary homologous series is suggested. The approach is based on the linear dependence of these values on T b for the preceding homologues, T b(n) = aTb(n ? 1) + b. This dependence, revealed for the first time, was used to obtain a recurrence relation for calculating T b of organic compounds within any series from the data on three simpler homologues of the same series. The mean a and b values can be used to estimate T b of an arbitrary organic compound from T b for one preceding homologue with an accuracy not inferior to that provided by the modern ACD software. Correlations of the general form P(n) = aP(n ? 1) + b are observed not only for the boiling points of organic compounds but also for their other properties P (refractive indexes, relative densities, and ionization energies). This opens up the possibility of creating unified algorithms for calculating various physicochemical constants of organic compounds instead of particular algorithms for every particular property known earlier.  相似文献   
999.
1000.
A theoretical framework is provided for generalizing the inferences drawn from the results of earlier experimental studies of kinetics of crystallization in oriented poly(ethylene terephthalate). The framework is obtained by combining extensions of classical nucleation theories in polymers3,4 and a theory of crystal growth with anisotropic incorporation of segments into growing crystals.15 It is shown that, while a very strong dependence of rate of primary nucleation on orientation does exist, there is a only a much weaker dependence of rate of crystal growth on the orientation of the crystallizing polymer. The theoretical formulation provided here would allow qualitative estimates for comparison with experiments.  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