全文获取类型
收费全文 | 704048篇 |
免费 | 5615篇 |
国内免费 | 2064篇 |
专业分类
化学 | 343849篇 |
晶体学 | 10120篇 |
力学 | 37137篇 |
综合类 | 19篇 |
数学 | 112533篇 |
物理学 | 208069篇 |
出版年
2021年 | 5703篇 |
2020年 | 6229篇 |
2019年 | 7057篇 |
2018年 | 18993篇 |
2017年 | 18904篇 |
2016年 | 18917篇 |
2015年 | 8124篇 |
2014年 | 12498篇 |
2013年 | 28721篇 |
2012年 | 25157篇 |
2011年 | 35412篇 |
2010年 | 24416篇 |
2009年 | 24747篇 |
2008年 | 30430篇 |
2007年 | 32172篇 |
2006年 | 22484篇 |
2005年 | 21024篇 |
2004年 | 19851篇 |
2003年 | 18497篇 |
2002年 | 17418篇 |
2001年 | 17920篇 |
2000年 | 13948篇 |
1999年 | 10711篇 |
1998年 | 9270篇 |
1997年 | 9072篇 |
1996年 | 8574篇 |
1995年 | 7720篇 |
1994年 | 7641篇 |
1993年 | 7378篇 |
1992年 | 7908篇 |
1991年 | 8292篇 |
1990年 | 7931篇 |
1989年 | 7844篇 |
1988年 | 7639篇 |
1987年 | 7475篇 |
1986年 | 7143篇 |
1985年 | 9145篇 |
1984年 | 9525篇 |
1983年 | 8103篇 |
1982年 | 8494篇 |
1981年 | 7879篇 |
1980年 | 7534篇 |
1979年 | 8129篇 |
1978年 | 8384篇 |
1977年 | 8219篇 |
1976年 | 8160篇 |
1975年 | 7846篇 |
1974年 | 7688篇 |
1973年 | 8106篇 |
1972年 | 5772篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
A double monochromator is developed and manufactured on the basis of an acousto-optic filter made of a potassium dihydrogen phosphate (KDP) single crystal. The device has an operating range of 260–540 nm and improved optical characteristics: high aperture ratio (an angular aperture of 2° and a linear aperture of 6.5x15 mm), high polarization contrast (~108), and low level of transmission sidelobes (~103). The spectral resolution of the monochromator at the edges of the operating range is 0.5 and 3 nm, respectively. The control frequency band is 60–150 MHz. Experimentally, it is shown that, for sound beams with equivalent geometric parameters, the diffraction efficiency provided by the KDP-based acousto-optic filter is an order of magnitude higher than that obtained with a noncollinear acousto-optic filter fabricated on the basis of crystalline quartz. 相似文献
993.
994.
This paper investigates the mathematical well‐posedness of the variational model of quasi‐static growth for a brittle crack proposed by Francfort and Marigo in [15]. The starting point is a time discretized version of that evolution which results in a sequence of minimization problems of Mumford and Shah type functionals. The natural weak setting is that of special functions of bounded variation, and the main difficulty in showing existence of the time‐continuous quasi‐static growth is to pass to the limit as the time‐discretization step tends to 0. This is performed with the help of a jump transfer theorem which permits, under weak convergence assumptions for a sequence {un} of SBV‐functions to its BV‐limit u, to transfer the part of the jump set of any test field that lies in the jump set of u onto that of the converging sequence {un}. In particular, it is shown that the notion of minimizer of a Mumford and Shah type functional for its own jump set is stable under weak convergence assumptions. Furthermore, our analysis justifies numerical methods used for computing the time‐continuous quasi‐static evolution. © 2003 Wiley Periodicals, Inc. 相似文献
995.
Wolfgang Staubach 《Journal d'Analyse Mathématique》2003,91(1):389-400
In this paper, we present an explicit calculation of the heat kernel, fundamental solution and Schwartz kernel of the resolvent
for the Heisenberg Laplacian using Wiener path integrals and their realizations via the Trotter product formula. This also
gives another derivation of mehler’s formula. 相似文献
996.
Summary The detachment of a rubber matrix from a rigid inclusion under monotonic loading and at subsequent relaxation is investigated within two dimensional analysis. Examined are stress–strain experimental data acquired with the help of a test bed equipped with a digital image-acquisition device. The influence of the interfacial bonding strength and the particle size on the detachment process is analyzed. The influence of the interfacial bonding strength is visible in the stress–strain diagram of loading and in the recorded images. The relaxation test reveals no influence of the bonding strength on the stress-relaxation. However, the image analysis indicates a secondary transient creep of the contour of detachment, which depends on the interfacial bonding. 相似文献
997.
A. Rusetsky 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):491-494
In the perturbative field-theoretical models we investigate the inclusion of the electromagnetic interactions into the purely strong theory that describes hadronic processes. In particular, we study the convention for splitting electromagnetic and strong interactions and the ambiguity of such a splitting. The issue of the interpretation of the parameters of the low-energy effective field theory in the presence of electromagnetic interactions is addressed, as well as the scale and gauge dependence of the effective theory couplings. We hope, that the results of these studies are relevant for the electromagnetic sector of ChPT.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.40.Ks Electromagnetic corrections to strong- and weak-interaction processes - 13.40.Dk Electromagnetic mass differences - 11.30.Rd Chiral symmetries - 11.10.Hi Renormalization group evolution of parameters 相似文献
998.
999.
Rü diger W. Braun Reinhold Meise B. A. Taylor 《Proceedings of the American Mathematical Society》2003,131(8):2423-2433
We give a sufficient condition for a local radial Phragmén-Lindelöf principle on analytic varieties. This condition is expressed in terms of existence of hyperbolic directions.
1000.