全文获取类型
收费全文 | 51518篇 |
免费 | 1784篇 |
国内免费 | 128篇 |
专业分类
化学 | 34848篇 |
晶体学 | 360篇 |
力学 | 1096篇 |
数学 | 7517篇 |
物理学 | 9609篇 |
出版年
2023年 | 381篇 |
2022年 | 359篇 |
2021年 | 631篇 |
2020年 | 896篇 |
2019年 | 874篇 |
2018年 | 940篇 |
2017年 | 904篇 |
2016年 | 1828篇 |
2015年 | 1537篇 |
2014年 | 1657篇 |
2013年 | 3103篇 |
2012年 | 3466篇 |
2011年 | 3776篇 |
2010年 | 2189篇 |
2009年 | 1829篇 |
2008年 | 3113篇 |
2007年 | 3025篇 |
2006年 | 2733篇 |
2005年 | 2547篇 |
2004年 | 2122篇 |
2003年 | 1663篇 |
2002年 | 1494篇 |
2001年 | 977篇 |
2000年 | 877篇 |
1999年 | 696篇 |
1998年 | 563篇 |
1997年 | 458篇 |
1996年 | 615篇 |
1995年 | 485篇 |
1994年 | 438篇 |
1993年 | 491篇 |
1992年 | 448篇 |
1991年 | 341篇 |
1990年 | 332篇 |
1989年 | 315篇 |
1988年 | 283篇 |
1987年 | 253篇 |
1986年 | 238篇 |
1985年 | 353篇 |
1984年 | 317篇 |
1983年 | 255篇 |
1982年 | 268篇 |
1981年 | 272篇 |
1980年 | 225篇 |
1979年 | 243篇 |
1978年 | 252篇 |
1977年 | 196篇 |
1976年 | 190篇 |
1975年 | 195篇 |
1973年 | 164篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
E. Hernández L. Rodríguez-Marín 《Journal of Optimization Theory and Applications》2007,134(1):119-134
In this paper, we study optimization problems where the objective function and the binding constraints are set-valued maps
and the solutions are defined by means of set-relations among all the images sets (Kuroiwa, D. in Takahashi, W., Tanaka, T.
(eds.) Nonlinear analysis and convex analysis, pp. 221–228, 1999). We introduce a new dual problem, establish some duality theorems and obtain a Lagrangian multiplier rule of nonlinear type
under convexity assumptions. A necessary condition and a sufficient condition for the existence of saddle points are given.
The authors thank the two referees for valuable comments and suggestions on early versions of the paper. The research of the
first author was partially supported by Ministerio de Educación y Ciencia (Spain) Project MTM2006-02629 and by Junta de Castilla
y León (Spain) Project VA027B06. 相似文献
52.
Martin I. Karakhanyan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(3):146-150
The paper proves some general facts on commutators that refer to Fuglede-Putnam classical theorem in the spectral theory of not necessarily selfadjoint operators. 相似文献
53.
Fe–Al alloys around the concentration of 30 at. % Al present re-entrant spin-glass behaviour at low temperatures. This behaviour is not completely understood and Mössbauer spectroscopy, combined with other experimental techniques, is useful to describe and explain this behaviour. Results show that the Mössbauer spectra coincide with the magnetic behaviour showed in literature and they can be explained as a magnetic cluster system whose magnetic clusters are getting smaller when the temperature is decreasing. When the temperature is reaching to the spin-glass transition at 92 K the spins in the paramagnetic matrix are moving slower and below this transition the spins are completely frozen. 相似文献
54.
G.M. Bilmes D.J.O. Orzi O.E. Martínez A. Lencina 《Applied physics. B, Lasers and optics》2006,82(4):643-648
The measurement of surface cleanliness is a significant problem in many industrial and technological processes. Existing methods are based on laboratory procedures, that are not performed in real time, can not be automated, and usually are restricted to a small portion of the sample. In this study we describe a new method for real time measurement of the amount of surface dirt or contamination deposited on a surface. It relies on the ablation of the surface dirt film by means of a short laser pulse, and the subsequent measurement of the emitted sound. The intensity of the sound is proportional to the amount of surface dirt and provides a direct measurement of the cleanliness of the surface. We also developed a reference sample for calibration, based on a uniform distribution of dots printed on white paper. The density and the dot size can be easily modified providing a homogeneous, uniform and reproducible standard for the measurement. Based on this method, we designed, developed and patented the first industrial instrument for on-line determination of the degree of cleanliness of manufactured cold rolled steel plate bobbins. PACS 79.20.D; 81.70.C; 42.62. 相似文献
55.
A. Veiga N. Martínez P. Mendoza Zélis G. A. Pasquevich F. H. Sánchez 《Hyperfine Interactions》2006,167(1-3):905-909
A prototype of a programmable constant-velocity scaler is presented. This instrument allows the acquisition of partial Mössbauer spectra in selected energy regions using standard drivers and transducers. It can be fully operated by a remote application, thus data acquisition can be automated. The instrument consists of a programmable counter and a constant-velocity reference. The reference waveform generator is amplitude modulated with 13-bit resolution, and is programmable in a wide range of frequencies and waveforms in order to optimize the performance of the transducer. The counter is compatible with most standard SCA, and is configured as a rate-meter that provides counts per selectable time slice at the programmed velocity. As a demonstration of the instrument applications, a partial Mössbauer spectrum of a natural iron foil was taken. Only positive energies were studied in 512 channels, accumulating 20 s per channel. A line width of 0.20 mm/s was achieved, performing with an efficiency of 80%. 相似文献
56.
In this paper a cubic lattice L(S) is endowed with a symmetric implication structure and it is proved that L(S) \ {0} is a power of the three-element simple symmetric implication algebra. The Metropolis–Rota’s symmetries are obtained as partial terms in the language of symmetric implication algebras. 相似文献
57.
Martin Fuchs 《manuscripta mathematica》1989,63(4):381-419
We prove an extension theorem for Sobolev functions which plays an important role in the partial regularity theory of vector valued functions which minimize degenerate variational integrals subject to some nonlinear side conditions in the image space. 相似文献
58.
59.
Nikolaií N. Nekhoroshev Dmitrií A. Sadovskií Boris I. Zhilinskií 《Annales Henri Poincare》2006,7(6):1099-1211
We introduce fractional monodromy in order to characterize certain non-isolated critical values of the energy–momentum map
of integrable Hamiltonian dynamical systems represented by nonlinear resonant two-dimensional oscillators. We give the formal
mathematical definition of fractional monodromy, which is a generalization of the definition of monodromy used by other authors
before. We prove that the 1:( − 2) resonant oscillator system has monodromy matrix with half-integer coefficients and discuss
manifestations of this monodromy in quantum systems.
Communicated by Eduard Zehnder
Submitted: February 25, 2005; Accepted: November 17, 2005 相似文献
60.