全文获取类型
收费全文 | 155726篇 |
免费 | 22298篇 |
国内免费 | 7021篇 |
专业分类
化学 | 118638篇 |
晶体学 | 1562篇 |
力学 | 8233篇 |
综合类 | 566篇 |
数学 | 15986篇 |
物理学 | 40060篇 |
出版年
2023年 | 4689篇 |
2022年 | 3520篇 |
2021年 | 4916篇 |
2020年 | 7143篇 |
2019年 | 5285篇 |
2018年 | 5377篇 |
2017年 | 3825篇 |
2016年 | 9339篇 |
2015年 | 8308篇 |
2014年 | 8893篇 |
2013年 | 10779篇 |
2012年 | 9217篇 |
2011年 | 7559篇 |
2010年 | 8389篇 |
2009年 | 8386篇 |
2008年 | 6405篇 |
2007年 | 5784篇 |
2006年 | 4779篇 |
2005年 | 4226篇 |
2004年 | 3692篇 |
2003年 | 3278篇 |
2002年 | 3417篇 |
2001年 | 2990篇 |
2000年 | 2393篇 |
1999年 | 1919篇 |
1998年 | 1741篇 |
1997年 | 1576篇 |
1996年 | 1523篇 |
1995年 | 1344篇 |
1994年 | 1354篇 |
1993年 | 1400篇 |
1992年 | 1224篇 |
1991年 | 1238篇 |
1990年 | 1215篇 |
1989年 | 1149篇 |
1988年 | 1051篇 |
1987年 | 1033篇 |
1985年 | 1037篇 |
1984年 | 1028篇 |
1978年 | 1001篇 |
1977年 | 1115篇 |
1976年 | 1280篇 |
1975年 | 1271篇 |
1974年 | 1317篇 |
1973年 | 1135篇 |
1972年 | 1120篇 |
1971年 | 1098篇 |
1970年 | 1150篇 |
1969年 | 1022篇 |
1968年 | 1088篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
An investigation was made of the kinetics of changes in the flow stress 0.1, modulation period , and electrical resistivity in the course of ageing of Cu-Ti, Cu-Ti-Al, Cu-Ti-Zn, and Cu-Ti-Ga alloys. There were no dispersion hardening effects during the early stages of the precipitation, corresponding to the = const condition. An increase in 0.1. was observed during the stage of coagulation of the secondary phases. The increase in the flow stress was described using a theory of hardening by coherent particles of the new phase but it did not agree with the theory of hardening of alloys exhibiting spinodal precipitation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 81–87, May, 1980. 相似文献
902.
V. A. Zhuravlev V. S. Korogodov Yu. N. Kotyukov N. B. Lysova 《Russian Physics Journal》1980,23(12):1026-1029
The method of transition probabilities is used to calculate the line width of ferromagnetic resonance in a medium with an inhomogeneous saturation magnetization. It is shown that in addition to linear (with respect to the Fourier components of the function describing inhomogeneities) terms, the perturbation Hamiltonian must include also quadratic terms. The frequency dependence of the contribution of the porosity to H is fundamentally different from the frequency dependence of the magnetic anisotropy contribution. This anisotropy contribution Ha() decreases on increase in the frequency and has a maximum at = (2/3)M, whereas the porosity contribution Hp increases on increase in the frequency and vanishes at = (2/3)M.deceasedTranslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp.48–52, December, 1980. 相似文献
903.
We consider the mechanism of macroscopic polarization of semiconducting plates owing to the interaction of free carriers with an impurity level, in which role the level of the residual impurity of compensated semiconductors may appear. This mechanism, in combination with the diffusion-drift mechanism of polarization, results in additional dispersion of the real () and imaginary () parts of the dielectric permittivity, this being particularly significant for semiconductors of thickness smaller than the screening length Ls of free carriers. The character of the behavior of and depends on the relation between the Maxwell relation time M and the times of carrier capture: c and ejection e by an impurity center. For cetm and (/Ls) e/c1 the dispersion of and is the same as for thick plates (/Ls1). For c m e and (/Ls)e/c1 the () curve has a characteristic kink in the region 1/e, indicating additional absorption associated with the ejection of carriers into the surface region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 11–13, October, 1981. 相似文献
904.
905.
Dr. H. G. Kopetzky 《Monatshefte für Mathematik》1977,84(3):213-217
Arithmetic formulae and an asymptotic expression for the order of magnitude of the arithmetic function
ged (s, n) and of a generalisation of it are derived. 相似文献
906.
Dr. Hartmut Pecher 《manuscripta mathematica》1977,20(3):227-244
This paper deals with the global classical solvability of the Cauchy problem for nonlinear wave equations of higher order of the following form where denotes the Laplacian, a real constant, m a positive integer, and f the nonlinearity. Using results of the first part [6] concerning estimations for the kernel of the associated integral equation a priori estimates for certain LP-norms of the local regular solution are established for higher space dimensions and for a class of nonlinearities satisfying certain growth and positivity conditions. This leads to completely regular solutions by means of the Sobolev embedding theorems. 相似文献
907.
Prof. Dr. Alexander Aigner 《Monatshefte für Mathematik》1977,83(2):89-91
It is shown by a simple induction that any square-free natural number is the square-free kernel of Euler's -function of infinitely many natural numbers. Furthermore every square-free natural number >1 is the square-free kernel of Euler's -function of infinitely many square-numbers. 相似文献
908.
Dr. Richard Koch 《Monatshefte für Mathematik》1977,83(2):133-146
Let ={e(u)|uI} be a one-parameter family of straight lines forming a ruledC
r-2-surface E
n (n2,r1) without singular generatorse(u) (uI). As a synopsis, a generalization and an improvement of various results already known about the strictional properties of ruled surfaces E
n (especially in the casen=3) the author demonstrates a uniform geometrical way of defining and uniquely obtaining thestriction point S(u) and theparameter of distribution d(u) of a generatore(u) under the minimal assumptions thate(u)E
n
(n2) be noncylindrical andr1. Other methods of obtainingS(u) andd(u) are discussed in comparison, and special strictional properties ofskew ruled surfaces E
n are proved.
Herrn Prof. Dr. H. R. Müller zum 65. Geburtstag 相似文献
Herrn Prof. Dr. H. R. Müller zum 65. Geburtstag 相似文献
909.
Dr. Moritz Armsen 《manuscripta mathematica》1977,20(3):245-253
The classical Gauss-Bonnet formula has the form I(gij)=2, where I(gij) represents a sum of three terms each of which depends on the metric tensor gij. It is shown that the first variation I of I(gij) with respect to the metric gij vanishes and that for the Euclidean metric ij we have I(ij)=2. From this the formula I(gij)=2 follows. In the process, explicit expressions are obtained for the first variation of each of the three terms which comprise I(gij). Furthermore, a general expression for the first variation of a multiple integral whose integrand is a scalar density depending on the metric tensor gij and its derivatives up to the second order is obtained with the aid of results of Rund [1]. 相似文献
910.
Dr. Bohuslav Diviš 《Monatshefte für Mathematik》1977,84(1):21-28
LetQ(u) be a positive definite quadratic form inr2 variables with a real symmetric coefficient matrix of determinantD. Given a real vectorb with 0b
j
<1, forx>0 letA(x) be the number of lattice points in the ellipsoidQ(u+b)x, letV(x) be the volume of this ellipsoid andP(x)=A(x)–V(x). Let
. By introduction of a parameter we shall show how the treatment of estimates onP(x) and onM(x) can be unified. 相似文献