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   752篇
  免费   12篇
化学   581篇
晶体学   10篇
力学   8篇
数学   29篇
物理学   136篇
  2021年   7篇
  2020年   15篇
  2019年   15篇
  2018年   6篇
  2017年   7篇
  2016年   11篇
  2015年   6篇
  2014年   14篇
  2013年   30篇
  2012年   40篇
  2011年   51篇
  2010年   28篇
  2009年   28篇
  2008年   39篇
  2007年   34篇
  2006年   40篇
  2005年   37篇
  2004年   40篇
  2003年   31篇
  2002年   27篇
  2001年   14篇
  2000年   11篇
  1999年   7篇
  1998年   6篇
  1997年   9篇
  1994年   6篇
  1993年   7篇
  1992年   9篇
  1991年   8篇
  1990年   8篇
  1988年   8篇
  1987年   6篇
  1986年   7篇
  1985年   9篇
  1984年   12篇
  1982年   7篇
  1981年   7篇
  1980年   8篇
  1979年   12篇
  1978年   7篇
  1977年   8篇
  1976年   8篇
  1975年   4篇
  1974年   4篇
  1973年   6篇
  1971年   5篇
  1970年   8篇
  1969年   8篇
  1968年   5篇
  1967年   4篇
排序方式: 共有764条查询结果,搜索用时 15 毫秒
81.
Zusammenfassung Die Löslichkeiten folgender Verbindungen wurden in Wasser bei 5°-Intervallen von 0° bis 40° bestimmt; Anilin, Mtrobenzol, Chlorbenzol,-Oxynaphthalin und-Nitronaphthalin. Aus diesen Ergebnissen wurden die thermodynamischen Parameter für den Lösungsprozeß der reinen flüssigen Verbindungen in Wasser berechnet. Das Resultat wurde mit Hilfe des Begriffs der Eisberge erklärt.Beim Benzol, Anilin und Chlorbenzol waren die Lösungswärmen negativ bei niedrigeren Temperaturen und wurden mit steigender Temperatur positiver. Dagegen traten beim Nitrobenzol,-Oxynaphthalin und-Nitronaphthalin stets die positiven Lösungswärmen auf. Dies sollte auf die großen intermolekularen Kräfte in der reinen Flüssigkeit zurückzuführen sein.  相似文献   
82.
Summary Measurements of photoluminescence and luminescence excitation spectra of ZnSiP2 have been performed at 4.2K and two results were obtained. One is the observation of a new sharp emission line at 1.980 eV, due to the bound exciton associated with the pseudodirect gap. The other is the observation of another new series of absorption lines in the luminescence excitation spectrum of an emission line, at 1.984 eV, in addition to those reported previously. These results indicate that in ZnSiP2 radiative transitions occur at both the indirect and the pseudodirect gaps. Paper presented at the ?V International Conference on Ternary and Multinary Compound?, held in Cagliari, September 14–16, 1982.  相似文献   
83.
84.
The far-infrared spectrum of an ethereal solution of the naphthalene radical anion prepared by reduction with an alkali metal shows an absorption band which is considered to be due to a vibration of an ion pair. The corresponding force constant was calculated for each ion pair from the observed frequency. The obtained values are of reasonable magnitude.  相似文献   
85.
86.
The mutual relations between s-channel discontinuities of reggeon diagrams with planar triple-Regge vertices are discussed. It is shown that, in general, contributions coming from different cuttings are not simply related to each other as certain vertices acquire non-trivial phase factors depending on the nature of the cutting. For diagrams with only triple-Regge vertices this phase may be related to the triple-Regge phase. The complete four-reggeon vertices are not known in general. An approximation is considered which amounts to preserving only the absorptive part of triple- or four-reggeon amplitudes in certain parts of the diagrams. This approximation turns out to be equivalent to a simple absorbed multiperipheral model. The problem of exchange degeneracy breaking within the dual unitarisation Scheme is briefly discussed as an example.  相似文献   
87.
Binding states of deposited Ga and Sn on the W and Mo substrates were studied by measuring the evaporation fields of the deposited metal atoms at various temperatures. Ga and Sn form two layers: an overlayer and an underneath pseudomorphic layer which directly contacts the substrate surface. The evaporation fieds of the overlayer Ga and Sn atoms were found to be the same on various crystal planes and significantly lower than that of the pseudomorphic Ga and Sn atoms, indicating that the binding between the overlayer atoms and the pseudomorphic atoms is much weaker than that between the pseudomorphic atoms and the substrate W and Mo atoms. The finding that the evaporation field of the pseudomorphic atoms on W is very close to that on Mo while the evaporation field of W is significantly higher than that of Mo was unexpected. Another interesting finding is that the field emission current from the (011) plane is not noticeably affected by the coverage of the mono-atomic Ga layer arranged in the superstructure while the current from other crystal planes covered by the pseudomorphic layer having the same atomic arrangement with the substrate surface is minimized. Furthermore, it has been found that the evaporation field of the Ga overlayer is lower than that of Sn, while the Ga pseudomorph is more stable than Sn pseudomorph on W surface at temperatures below about 100 K. The temperature dependence of the evaporation field was also examined and compared with existing models.  相似文献   
88.
It is argued that, in the leading logarithm approximation (LLA) of asymptotically free quantum chromodynamics (QCD), a simple algorithm (jet calculus) can be justified for computing a large number of quantities related to the longitudinal and transverse structure of quark and gluon jets.We formulate the rules of jet calculus in two variables, x and y which are related to longitudinal (energy) and transverse momentum respectively. Throughout the paper, quark and gluon jets are contrasted. After reviewing what has been done on longitudinal spectra, we turn to the transverse structure of jets down to relative transverse momenta of the order of a few GeV (independently of the total energy). The relation of our work to that of Dokshitzer, D'Yakonov and Troyan is elucidated. We also study jets generated by (almost) real photons and compare both with standard “final” parton jets.We also discuss calorimeter measured quantities, compare our results with those of other authors and propose a new and easy way for measuring QCD-predictable anomalous dimensions.We finally give a Lagrangian formulation of jet calculus, as a non-local theory in 1 + 1 dimensions to be solved in the tree approximation.  相似文献   
89.
This paper deals with asymptotic expansions for the non-null distributions of certain test statistics concerning a correlation matrix in a multivariate normal distribution. For this purpose an asymptotic expansion is given for the distribution of a function of the sample correlation matrix. As special cases of the resulting expansion, asymptotic expansions for the distributions of the sample correlation coefficient, Fisher's z-transformation and arcsine transformation are also given.  相似文献   
90.
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