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   497篇
  免费   72篇
  国内免费   89篇
化学   386篇
晶体学   5篇
力学   28篇
数学   47篇
物理学   192篇
  2023年   8篇
  2022年   16篇
  2021年   18篇
  2020年   15篇
  2019年   15篇
  2018年   27篇
  2017年   25篇
  2016年   28篇
  2015年   16篇
  2014年   28篇
  2013年   51篇
  2012年   43篇
  2011年   42篇
  2010年   28篇
  2009年   22篇
  2008年   44篇
  2007年   22篇
  2006年   12篇
  2005年   15篇
  2004年   13篇
  2003年   12篇
  2002年   11篇
  2001年   10篇
  2000年   9篇
  1999年   9篇
  1998年   7篇
  1997年   5篇
  1995年   5篇
  1994年   5篇
  1993年   5篇
  1992年   7篇
  1990年   4篇
  1986年   4篇
  1985年   3篇
  1984年   4篇
  1983年   7篇
  1982年   3篇
  1981年   5篇
  1980年   4篇
  1979年   4篇
  1978年   5篇
  1977年   4篇
  1974年   3篇
  1973年   3篇
  1971年   3篇
  1970年   2篇
  1969年   4篇
  1961年   2篇
  1958年   2篇
  1957年   3篇
排序方式: 共有658条查询结果,搜索用时 640 毫秒
71.
In this paper it has been experimentally proved that the dislocation density of annealed copper ribbons grows up to saturation during repeated quenching. The effect is explained on the basis of a simple idea: During each annealing a certain part of the excessive dislocation density is removed and during each quenching a constant increase in dislocation density is generated.  相似文献   
72.
In the great majority of papers dealing with non-linear dynamic buckling of plates it is assumed that the edge at which the in-plane load is applied is not deformable (rigid). In those few references in which buckling with deformable edges is examined normally a variational approach is used, based on “trial” functions for the in-plane displacements, which approach often leads to incorrect results. In this paper an exact form of the solution is found for the in-plane displacements, it being assumed that the membrane force is, at all times, exactly equal to the load applied at the corresponding loaded edge. As is well known, when the plate is buckled through a rigid beam these two forces are only on average equal to each other. It is shown here that the deformability of the loaded edges for plates undergoing large deformations should be taken into account for square-shaped plates, especially for those close to the so-called “golden-cut” shape (the aspect ratio between the edges equal to √2), while for long rectangular plates this effect may be disregarded.  相似文献   
73.
In the reaction of N-[2-(5-bromouracil-1-yl)ethyl]alkylamines with alkylamines at 40 °C kine-substitution takes place with the formation of N-[2-(6-alkylamino-uracil-1-yl)ethyl]alkylamines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1260–1261, September, 1984.  相似文献   
74.
The magnetostriction constant of three iron-nickel alloys and one Fe-Ni-Co alloy was measured as a function of the plastic elongation up to about 25%. The magnetostriction constant decreases with deformation in all materials. In Fe-Ni-Co alloy the volume magnetostriction also decreases. The influence of crystallographic texture is discussed and it is shown that it is not a decisive factor. The observed decrease is explained by assuming the influence of lattice deformation on spin-orbital interaction.
-
- Fe-Ni-Co 25%. . Fe-Ni-Co . , . .


In conclusion the authors thank Z. Málek and S. Libovický for carefully reading this paper and for remarks, J. Míová for help in the measurements, J. Cáslavský for X-ray determination of the texture and members of the chemical department of the Institute of Physics for thermal treatment and analysis of the samples.  相似文献   
75.
76.
A direct spectrophotometric method has been developed for the determination of the amount of proteins immobilized on bead cellulose. The method is based on dissolution of conjugates in cadmium tris(ethylenediamine) hydroxide (trivial name, cadoxene) that is optically transparent in the region of the UV spectrum in which proteins absorb. The method developed for the determination of immobilized proteins is simple, rapid, and readily reproducible. The sensitivity of the method is dependent on theA 1cm 1% value of the free protein and on the amount of bound proteinm (mg protein/g carrier). In the terms ofA 1cm 1% ≥25 andm≥120 mg/g, the sensitivity of the mentioned method was comparable with those obtained by amino acids analyses by the ninhydrin reaction, by the modified Lowry reaction, or by radiometric determination. The possibility of substituting the direct spectrophotometric method for amino acid analysis was statistically evaluated; it does not seem to be rejected at the highest level of significance,P≤1%. The differences in paired observations were significant, but nonetheless proportional over the whole range of protein concentrations, making both methods correlable. The absolute accuracy of the direct spectrophotometric method could be influenced by the change ofA 1cm 1% value during solvolysis of the conjugate in cadoxene.  相似文献   
77.
One of the types of pyurinylpeptides (i.e., peptides constructed of pyrimidyl-and purinyl--amino acids) consists of peptides including residues of only those -amino acids the lateral radicals of which contain nucleic bases. Below, such amino acids will be called nucleoamino acids and the peptides derived from them nucleopeptides. The latter are hybrid analogs of nucleic acids and proteins. Their study may lead to important theoretical and practical results.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7,pp. 1002–1003, July, 1970.We are continuing the synthesis and study of the properties of the pyurinylpeptides and nucleopeptides.  相似文献   
78.
79.
80.
We investigate the collective mode dispersions for the tight-binding dielectric matrix with two one-dimensional electron bands per donor and acceptor chains, and the three-dimensional long-range Coulomb electron-electron interaction within the random phase approximation. The hybridized collective modes are the result of the strong coupling between the intraband plasmon and the interband dipolar modes due to strong dipole Coulomb interactions. Our calculations show the existence of the low-energy renormalized plasmon mode above the electron-hole quasi-continuum in the long wavelength limit. The obtained modes are brought into correspondence with the optical data of quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ). Namely, the renormalized plasmon and the dipolar mode are assigned to the observed excitations at respective energy scales of roughly 10 meV and 0.75 eV, explaining why lower excitation is eliminated while higher excitation persists below the temperature of the Peierls phase transition.  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