全文获取类型
收费全文 | 211190篇 |
免费 | 1813篇 |
国内免费 | 138篇 |
专业分类
化学 | 93325篇 |
晶体学 | 2803篇 |
力学 | 11091篇 |
综合类 | 1篇 |
数学 | 38315篇 |
物理学 | 67606篇 |
出版年
2022年 | 785篇 |
2021年 | 1149篇 |
2020年 | 1428篇 |
2019年 | 1409篇 |
2018年 | 10680篇 |
2017年 | 11541篇 |
2016年 | 7082篇 |
2015年 | 2642篇 |
2014年 | 2729篇 |
2013年 | 5374篇 |
2012年 | 8727篇 |
2011年 | 17605篇 |
2010年 | 10640篇 |
2009年 | 10596篇 |
2008年 | 15343篇 |
2007年 | 18848篇 |
2006年 | 4424篇 |
2005年 | 10434篇 |
2004年 | 6690篇 |
2003年 | 6459篇 |
2002年 | 4425篇 |
2001年 | 3080篇 |
2000年 | 2558篇 |
1999年 | 1713篇 |
1998年 | 1548篇 |
1997年 | 1434篇 |
1996年 | 1568篇 |
1995年 | 1369篇 |
1994年 | 1370篇 |
1993年 | 1443篇 |
1992年 | 1389篇 |
1991年 | 1343篇 |
1990年 | 1320篇 |
1989年 | 1287篇 |
1988年 | 1220篇 |
1987年 | 1174篇 |
1986年 | 1104篇 |
1985年 | 1420篇 |
1984年 | 1511篇 |
1983年 | 1325篇 |
1982年 | 1351篇 |
1981年 | 1258篇 |
1980年 | 1191篇 |
1979年 | 1232篇 |
1978年 | 1407篇 |
1977年 | 1321篇 |
1976年 | 1199篇 |
1975年 | 1132篇 |
1974年 | 1131篇 |
1973年 | 1160篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain
a decomposition of continuity. 相似文献
82.
83.
Wolfram Bremser Roland Becker Heinrich Kipphardt Petra Lehnik-Habrink Ulrich Panne Antje Töpfer 《Accreditation and quality assurance》2006,11(10):489-495
ISO Guide 35 deals with RM stability issues and scrutinizes the evaluation of stability testing results under the assumption that either there is no trend at all (a rather rare situation), or any observed deterministic change is insignificant and thus can be neglected. However, market demands for reliable reference materials are obviously not limited to stable or at least seemingly stable materials. In many analytical applications, analytes and measurands under consideration are known, or at least suspected, to be unstable on time scales that may vary widely from measurand to measurand. The Federal Institute for Materials Research and Testing (BAM) has developed (and successfully uses) an integrated approach in its certification practice. The approach is based on an initial stability study and subsequent post-certification monitoring. Data evaluation is model-based and takes advantage of all information collected in the stability testing scheme(s). It thus allows one to deal with any kind of instability observed, to assess limiting time intervals at any stress condition in the range tested, to estimate a final expiry date for materials with detected instabilities or the maximum admissible re-testing interval for seemingly stable materials, and to assess maximum admissible stress loads during delivery of the material to the customer. The article describes (and exemplifies) typical study layout, the model selection, and the integrated data assessment. 相似文献
84.
Abstract Under a suitable ellipticity condition, we show that classical SG-pseudodifferential operators of nonnegative order possess
complex powers. We show that the powers are again classical and derive an explicit formula for all homogeneous components.
Keywords: Complex power, Weighted symbols, Noncompact manifolds 相似文献
85.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
86.
Formalization for problems of multicriteria decision making under uncertainty is constructed in terms of guaranteed and weak
estimates. A relevant definition of the vector maximinimax value is given. Parameterization and approximation of maximum,
minimax, and maximinimax values based on the inverse logical convolution are suggested. An application for multicommodity
networks is considered.
Received: December 13, 2000 / Accepted: August 21, 2001?Published online May 8, 2002 相似文献
87.
The procedure for calculating the dispersion of the refractive and absorption indices and thickness of an optical film, based on measurements of spectral dependence of the transmittance, is described. The film parameters are calculated using a solution of the approximation problem. The effect of the film model on the calculated values of the refractive and absorption indices is analyzed. 相似文献
88.
Rainer Löwen 《Journal of Geometry》1989,36(1-2):110-116
We prove that a spread S over a locally compact nondlscrete field F defines a topological translation plane if and only if the spread is compact. For F=R, this is implicit in Breuning's thesis [Bre], cf. [B 2]. For the proof, we describe the point set of the projective translation plane as a quotient space of some projective space, with identifications taking place in one hyperplane. This is new even for F=R. 相似文献
89.
O. Babelon 《Communications in Mathematical Physics》2006,266(3):819-862
The classical Volterra model, equipped with the Faddeev-Takhtajan Poisson bracket provides a lattice version of the Virasoro algebra. The Volterra model being integrable, we can express the dynamical variables in terms of the so-called separated variables. Taking the continuum limit of these formulae, we obtain the Virasoro generators written as determinants of infinite matrices, the elements of which are constructed with a set of points lying on an infinite genus Riemann surface. The coordinates of these points are separated variables for an infinite set of Poisson commuting quantities including L
0. The scaling limit of the eigenvector can also be calculated explicitly, so that the associated Schroedinger equation is in fact exactly solvable. 相似文献
90.
The quantitative rainbow schlieren deflectometry (RSD) technique was applied to measure temperature and oxygen concentration in an axisymmetric hydrogen gas-jet diffusion flame burning in quiescent air at fuel jet exit Reynolds number of 70. Schlieren measurements were compared with conventional measurements using a thermocouple and a gas-sampling probe. Good agreement between the two measurement techniques was achieved on the fuel-lean side of the flame. 相似文献