全文获取类型
收费全文 | 4799篇 |
免费 | 134篇 |
国内免费 | 35篇 |
专业分类
化学 | 2793篇 |
晶体学 | 23篇 |
力学 | 163篇 |
数学 | 683篇 |
物理学 | 1306篇 |
出版年
2023年 | 30篇 |
2022年 | 116篇 |
2021年 | 163篇 |
2020年 | 112篇 |
2019年 | 175篇 |
2018年 | 163篇 |
2017年 | 144篇 |
2016年 | 206篇 |
2015年 | 134篇 |
2014年 | 180篇 |
2013年 | 249篇 |
2012年 | 333篇 |
2011年 | 347篇 |
2010年 | 199篇 |
2009年 | 199篇 |
2008年 | 292篇 |
2007年 | 267篇 |
2006年 | 256篇 |
2005年 | 213篇 |
2004年 | 170篇 |
2003年 | 121篇 |
2002年 | 120篇 |
2001年 | 61篇 |
2000年 | 55篇 |
1999年 | 42篇 |
1998年 | 53篇 |
1997年 | 41篇 |
1996年 | 39篇 |
1995年 | 29篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 25篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1975年 | 17篇 |
1974年 | 15篇 |
1970年 | 14篇 |
1968年 | 15篇 |
1967年 | 13篇 |
排序方式: 共有4968条查询结果,搜索用时 31 毫秒
91.
The results of an investigation of the recovery of the elasticoviscous characteristics after thixotropic reduction by periodic deformation in the nonlinear zone are reported. The rate of recovery of the mechanical properties depends on the deformation frequency and the previous history of dynamic deformation is shown to affect the dependence of the elasticoviscous characteristics on the shear rate gradient. The effects of stationary and dynamic deformation regimes on the relaxation spectrum of the material are compared.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 528–533, May–June, 1969. 相似文献
92.
M. N. Yakovlev 《Journal of Mathematical Sciences》1983,22(2):1270-1274
One proves theorems regarding the estimates of the solutions of systems of linear algebraic equations and inequalities. On the basis of these theorems one suggests a method for estimating the norm of the inverse matrix of a system of difference equations which approximates a boundary-value problem for an integrodifferential equation. The method allows us to eliminate the restrictions which are usually imposed on the coefficients of the integrodifferential equation in order to ensure the diagonal dominance in the system of the difference equations. One considers an application to nonlinear problems. 相似文献
93.
Let (A,α) be a C*-dynamical system. We introduce the notion of pressure P
α(H) of the automorphism α at a self-adjoint operator H∈A. Then we consider the class of AF-systems satisfying the following condition: there exists a dense α-invariant *-subalgebra
? of A such that for all pairs a,b∈? the C*-algebra they generate is finite dimensional, and there is p=p(a,b)∈ℕ such that [α
j
(a),b]= 0 for |j|≥p. For systems in this class we prove the variational principle, i.e. show that P
α(H) is the supremum of the quantities h
φ(α) −φ(H), where h
φ(α) is the Connes–Narnhofer–Thirring dynamical entropy of α with respect to the α-invariant state φ. If H∈A, and P
α(H) is finite, we show that any state on which the supremum is attained is a KMS-state with respect to a one-parameter automorphism
group naturally associated with H. In particular, Voiculescu's topological entropy is equal to the supremum of h
φ(α), and any state of finite maximal entropy is a trace.
Received: 19 April 2000 / Accepted: 14 June 2000 相似文献
94.
Michael V. Klibanov Sergey I. Kabanikhin Dmitrii V. Nechaev 《Waves in Random and Complex Media》2006,16(4):473-494
The problem of computational time reversal is posed as the inverse problem of the determination of an unknown initial condition with a finite support in a hyperbolic equation, given the Cauchy data at the lateral surface. Two such two-dimensional inverse problems are solved numerically in the case when the domain is a quadrant and the Cauchy data are given at finite parts of the coordinate axes. The previously obtained Lipschitz stability estimate implies refocusing of the time-reversed wave field in the case of a small amount of noise in the data. It also indicates the possibility of good performance of a proper numerical method. Such performance is demonstrated in this paper for a particular problem and a particular numerical method. 相似文献
95.
96.
Sergey Chervon 《General Relativity and Gravitation》2004,36(7):1547-1553
A new strategy of exact solutions construction in inflationary cosmology within the self-interacting scalar field theory is proposed. It is shown that inflationary models have no restrictions dictated by the slow-roll approximation on the self-interacting potential. The suggested approach makes it possible to compute precisely the e-folds numbers in inflationary scenarios. The scalar field with a logarithmic evolution in time is analyzed in details. Other possible types of scalar field evolution are discussed. 相似文献
97.
98.
The Soreq Applied Research Accelerator Facility (SARAF): Overview,research programs and future plans
Israel Mardor Ofer Aviv Marilena Avrigeanu Dan Berkovits Adi Dahan Timo Dickel Ilan Eliyahu Moshe Gai Inbal Gavish-Segev Shlomi Halfon Michael Hass Tsviki Hirsh Boaz Kaiser Daniel Kijel Arik Kreisel Yonatan Mishnayot Ish Mukul Ben Ohayon Michael Paul Amichay Perry Hitesh Rahangdale Jacob Rodnizki Guy Ron Revital Sasson-Zukran Asher Shor Ido Silverman Moshe Tessler Sergey Vaintraub Leo Weissman 《The European Physical Journal A - Hadrons and Nuclei》2018,54(5):91
99.
100.
Monika Kořenková Dr. Ing. Martin Hejda Prof. Milan Erben Dr. Ing. Robert Jirásko Prof. Dr. Roman Jambor Prof. Aleš Růžička Dr. Elena Rychagova Prof. Sergey Ketkov Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12884-12888
The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound. 相似文献