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   1967篇
  免费   82篇
  国内免费   25篇
化学   1258篇
晶体学   4篇
力学   70篇
数学   345篇
物理学   397篇
  2023年   8篇
  2021年   21篇
  2020年   28篇
  2019年   35篇
  2018年   21篇
  2017年   22篇
  2016年   59篇
  2015年   51篇
  2014年   51篇
  2013年   82篇
  2012年   122篇
  2011年   160篇
  2010年   76篇
  2009年   71篇
  2008年   107篇
  2007年   126篇
  2006年   133篇
  2005年   121篇
  2004年   85篇
  2003年   89篇
  2002年   96篇
  2001年   35篇
  2000年   25篇
  1999年   19篇
  1998年   22篇
  1997年   28篇
  1996年   17篇
  1995年   11篇
  1994年   14篇
  1993年   17篇
  1992年   21篇
  1991年   16篇
  1990年   9篇
  1989年   11篇
  1988年   9篇
  1987年   12篇
  1986年   8篇
  1985年   18篇
  1984年   19篇
  1983年   17篇
  1982年   16篇
  1981年   20篇
  1980年   11篇
  1979年   8篇
  1978年   17篇
  1977年   12篇
  1976年   11篇
  1975年   8篇
  1973年   11篇
  1969年   8篇
排序方式: 共有2074条查询结果,搜索用时 15 毫秒
111.
The equality between the spontaneous magnetization and the long range order is established for the Ising model with nearest neighbour interactions for low and high temperatures. The proof is presented for the two-dimensional lattice but works also in higher dimensions. The result verifies that the valuem*=(1–(Sh)–4)1/8 of the spontaneous magnetization below the critical point calculated by Onsager and Yang is the true value, which has been a long standing open question.  相似文献   
112.
113.
A new source for producing YMξ radiation in an ESCA spectrometer is described. The system makes use of continuous evaporation of yttrium on a rotating anode. It is demonstrated that this scheme allows YMξ-excited electron spectra to be recorded without gradual loss of resolution and intensity due to anode oxidation. Electron spectra of Ar, Hg and N2 excited by YMξ radiation are studied. Relative photoelectric cross-sections of the 5d52, 5d52 and 6s orbitals in Hg and the four valence orbitals in N2 are measured. The valence electron shake-up spectrum of N2 is discussed.  相似文献   
114.
115.
116.
The efficiencies of three groups of potential sulfite-stabilizing compounds were found to be in the order: carbonyls > alcohols = saccharides. A mole ratio of 1:1 between formaldehyde and sulfite was sufficient for stabilizing a sulfite solution for at least 72 h. The lower stabilizing efficiencies of the alcohols and saccharides examined could be compensated by using large excesses of these compounds. For example, if a 100-fold excess of glycerol over sulfite was used, the recovery of sulfite was 96% after 72 h compared with only 40% without addition of stabilizer. During separations by ion chromatography, almost no oxidation of the sample occurs provided the sample solution is directly injected into a deaerated eluent. For formaldehyde, the peak heights were found to depend on the molar ratio of the stabilizer to sulfite as well as on the concentration of sulfite. This effect was not found for the other stabilizers tested.  相似文献   
117.
At the Hamburger Isochronous Cyclotron the formation of the particle unstable ground state of 5Li(32? has been investigated in the reaction α + d → α + p + n at Eα = 28.3 MeV. The neutrons were detected in two liquid scintillation counters, while a large Si (Li) detector was used to observe the α-particles. In a first analysis, the tensor polarization parameters of the five-nucleon system 5Li are determined from the experimental data. The results are in quite good agreement with theoretical predictions of Hackenbroich et al.  相似文献   
118.
A controlled temperature controlled atmosphere atomization system is described. The sample is placed on a tungsten wire provided with temperature-controlled heating. After thermal pretreatment of the sample the wire is inserted into a hot quartz tube and rapid vaporization is accomplished by separate electrothermal heating. The pyrolysis products formed are mixed with a gas buffer and are passed through two equilibrium zones. The residence time of the analyte in the system is of the order of seconds so that the probability of attaining a state close to equilibrium is high for high temperatures. A third zone is placed perpendicularly to the others and constitutes the atomic absorption measuring cell. The usefulness of the system is illustrated for the determination of lead, bismuth, cadmium and zinc. The system provides unique possibilities in controlling interference effects in complex matrices. Examples are given for lead in concentrated chloride and sulphate solutions. Good agreement between the experimental results and high-temperature equilibrium calculations was obtained for a large variation in the composition of the gas phase.  相似文献   
119.
In this note some problems of asymptotic inference in a class of non-stationary stochastic processes are considered. In particular, it is shown that no criterion based on the existence of uniformly most powerful tests over a local neighborhood can be used in this situation.  相似文献   
120.
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