全文获取类型
收费全文 | 82036篇 |
免费 | 707篇 |
国内免费 | 131篇 |
专业分类
化学 | 44445篇 |
晶体学 | 1296篇 |
力学 | 3365篇 |
综合类 | 1篇 |
数学 | 8426篇 |
物理学 | 25341篇 |
出版年
2022年 | 710篇 |
2021年 | 981篇 |
2020年 | 1042篇 |
2019年 | 1172篇 |
2018年 | 1658篇 |
2017年 | 1750篇 |
2016年 | 2310篇 |
2015年 | 1129篇 |
2014年 | 1842篇 |
2013年 | 3529篇 |
2012年 | 3233篇 |
2011年 | 3640篇 |
2010年 | 2834篇 |
2009年 | 2786篇 |
2008年 | 3307篇 |
2007年 | 3160篇 |
2006年 | 3003篇 |
2005年 | 2714篇 |
2004年 | 2448篇 |
2003年 | 2256篇 |
2002年 | 2289篇 |
2001年 | 2288篇 |
2000年 | 1676篇 |
1999年 | 1284篇 |
1998年 | 1166篇 |
1997年 | 1066篇 |
1996年 | 955篇 |
1995年 | 858篇 |
1994年 | 841篇 |
1993年 | 849篇 |
1992年 | 885篇 |
1991年 | 961篇 |
1990年 | 911篇 |
1989年 | 927篇 |
1988年 | 841篇 |
1987年 | 795篇 |
1986年 | 754篇 |
1985年 | 892篇 |
1984年 | 980篇 |
1983年 | 830篇 |
1982年 | 851篇 |
1981年 | 757篇 |
1980年 | 714篇 |
1979年 | 782篇 |
1978年 | 896篇 |
1977年 | 919篇 |
1976年 | 811篇 |
1975年 | 776篇 |
1974年 | 794篇 |
1973年 | 762篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
751.
When can a k-edge-coloring of a subgraph K of a graph G be extended to a k-edge-coloring of G? One necessary condition is that for all X ? E(G) - E(K), where μi(X) is the maximum cardinality of a subset of X whose union with the set of edges of K colored i is a matching. This condition is not sufficient in general, but is sufficient for graphs of very simple structure. We try to locate the border where sufficiency ends. 相似文献
752.
For an exactly soluble classical spin model with long-range inhomogeneous coupling it is proved that in the absence of external magnetic field the free energy is aC
function of the temperature at the critical point. 相似文献
753.
Th. Brückel Y. Chernenkov B. Dorner V. P. Plakhty O. P. Smirnov 《Zeitschrift für Physik B Condensed Matter》1990,79(3):389-395
We have measured the spin wave spectrum for the garnet Ca3Cr2Ge3O12 by means of inelastic neutron scattering. The data can be well described in the framework of linear spin wave theory if we assume a Heisenberg model with two exchange parameters up to the next nearest neighbours (J
1 andJ
2) and a staggered anisotropy field (A). A least squares fit to the observed dispersion relations yield the following values for these parameters: J
1=–0.582(8)K,J
2=0.416(4)K,A=0.25(8)K. Although symmetry requires that two nearest neighbour exchange constantsJ
1 andJ
1
'
must be distinguished, only the average J
1=(J
1+3J
1
'
)/4 and the condition –0.35 K <J
1=J
1-J
1
'
<0.50 K could be deduced from the experiment. The most striking result is the positive value ofJ
2. We discuss the implications for an understanding of superexchange mediated by more than one oxygen atom. In an extension of the conventional analysis we have calculated the integrated intensities in order to check the eigenvectors directly. Good agreement between observed and calculated intensities was obtained. 相似文献
754.
The behavior of effective charges i(t) corresponding to the parameters of nonminimal coupling of scalar and gravitational fields in E6 Grand Unification Theory (GUT) in curve spacetimes is studied. It is shown that in a strong gravitational field ¦i(t)¦ grows indefinitely.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 74–11, September, 1990. 相似文献
755.
756.
V. O. Bytev 《Acta Appl Math》1989,16(1):117-142
The system of differential equations which describes the motion of continuum media of gas, liquid, Reiner-Rievling-type liquid, etc., is considered.% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaacqaHbp% GCdaWgaaWcbaGaamiDaaqabaGccqGHRaWkcaqGKbGaaeyAaiaabAha% caqGOaGaeqyWdiNaaeyDaiaabMcacaqG9aGaaeimaiaabUdaaeaacq% aHbpGCcaGGBbGaaeyDamaaBaaaleaacaqG0baabeaakiabgUcaRiaa% cIcacaqG1bGaeyyXICTaey4bIeTaaiykaiaabwhacaGGDbGaeyOeI0% IaamizaiaadMgacaWG2bGaey4dIuTaaiikaiabgEGirlaabwhacaGG% PaGaey4kaSIaey4bIeTaamiCaiaacUdaaeaacaWGWbWaaSbaaSqaai% aadshaaeqaaOGaey4kaSIaaeyDaiabgwSixlabgEGirlaadchacqGH% RaWkcaWGhbGaaeizaiaabMgacaqG2bGaaeiiaiaabwhacqGHRaWkca% WGibGaeqOXdyMaeyypa0JaaGimaiaac6caaaaa!7268!\[\begin{gathered} \rho _t + {\text{div(}}\rho {\text{u) = 0;}} \hfill \\ \rho [{\text{u}}_{\text{t}} + ({\text{u}} \cdot \nabla ){\text{u}}] - div\prod (\nabla {\text{u}}) + \nabla p; \hfill \\ p_t + {\text{u}} \cdot \nabla p + G{\text{div u}} + H\phi = 0. \hfill \\ \end{gathered} \]Solving the problem of its group classification, we obtained all the state equations which lead to the expansion of the main group assumed by the initial equations under the arbitrary elements , G, H. 相似文献
757.
Given an arbitrary point (x, u) inR
n
× R
+
m
, we give bounds on the Euclidean distance betweenx and the unique solution
to a strongly convex program in terms of the violations of the Karush-Kuhn-Tucker conditions by the arbitrary point (x, u). These bounds are then used to derive linearly and superlinearly convergent iterative schemes for obtaining the unique least 2-norm solution of a linear program. These schemes can be used effectively in conjunction with the successive overrelaxation (SOR) methods for solving very large sparse linear programs.Sponsored by the United States Army under Contract No. DAAG29-80-C-0041. This material is based on research sponsored by National Science Foundation Grant No. DCR-8420963 and Air Force Office of Scientific Research Grant No. AFOSR-ISSA-85-00080.On leave from CRAI, via Bernini 5, Rende, Cosenza, Italy. 相似文献
758.
O. V. Manturov 《Journal of Mathematical Sciences》1988,42(5):1944-1973
In the present survey a method is presented for the construction of invariant tensors (with respect to a given representation) called the inclusion principle and the possibility of applying the cited method to various problems of algebra, topology, geometry, and analysis.Translated from Itogi Nauki i Tekhniki, Seriya Problemy Geometrii, Vol. 18, pp. 105–142, 1986. 相似文献
759.
For an Ising ferromagnet with nearest-neighbour interactions of strengthK and surface magnetic fieldh, the surface free energy in the presence of a positively (or negatively) magnetized zero-field bulk phase is shown to be analytic inh for Reh<K–/, where =2.96 ... and is the inverse temperature. This puts the lower boundK–/ on the values ofh at which wetting and layering transitions can take place. 相似文献
760.
Linear mode conversion of waves near the maxima or minima of the density in a warm magnetized plasma
Behaviour of the h. f. electrostatic waves near the plasma or upper hybrid resonances was studied in the case that these resonances are situated at the maxima or minima of the plasma density. Supposing the parabolic density profile in these regions we obtained the connection formulae for the WKB solutions. In a weakly inhomogeneous magnetoplasma the effect of the parabolic profile manifests itself only in narrow frequency band centred at the resonance frequency corresponding to the extreme value of the density. The whole process can be then described by only two coefficients, viz. the power conversion and power transmission coefficients. 相似文献