全文获取类型
收费全文 | 20969篇 |
免费 | 711篇 |
国内免费 | 957篇 |
专业分类
化学 | 11615篇 |
晶体学 | 226篇 |
力学 | 1604篇 |
综合类 | 197篇 |
数学 | 3013篇 |
物理学 | 5982篇 |
出版年
2021年 | 271篇 |
2020年 | 319篇 |
2019年 | 380篇 |
2018年 | 435篇 |
2017年 | 463篇 |
2016年 | 573篇 |
2015年 | 323篇 |
2014年 | 529篇 |
2013年 | 754篇 |
2012年 | 707篇 |
2011年 | 745篇 |
2010年 | 741篇 |
2009年 | 744篇 |
2008年 | 756篇 |
2007年 | 746篇 |
2006年 | 589篇 |
2005年 | 564篇 |
2004年 | 526篇 |
2003年 | 521篇 |
2002年 | 583篇 |
2001年 | 555篇 |
2000年 | 441篇 |
1999年 | 326篇 |
1998年 | 268篇 |
1997年 | 256篇 |
1996年 | 247篇 |
1993年 | 248篇 |
1992年 | 247篇 |
1991年 | 253篇 |
1990年 | 273篇 |
1989年 | 269篇 |
1987年 | 246篇 |
1985年 | 276篇 |
1984年 | 289篇 |
1983年 | 262篇 |
1982年 | 277篇 |
1980年 | 258篇 |
1979年 | 301篇 |
1978年 | 329篇 |
1977年 | 320篇 |
1976年 | 404篇 |
1975年 | 360篇 |
1974年 | 388篇 |
1973年 | 396篇 |
1972年 | 369篇 |
1971年 | 332篇 |
1970年 | 314篇 |
1969年 | 298篇 |
1968年 | 253篇 |
1967年 | 250篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
V. Ya. Martens 《Technical Physics》1998,43(10):1247-1249
It is shown that the existence of a current in the external circuit of a double insulated probe without electrical bias between
its electrodes is evidence of the presence of a stream (beam) of charged particles in a plasma. The species of particles forming
a beam in a plasma, the direction and divergence of the beam, and information on the distribution of the current density over
the beam cross section in the plasma can be obtained by determining the direction and strength of the current in the external
circuit of the probe as it is positioned at various sites in the investigated system.
Zh. Tekh. Fiz. 68, 121–123 (October 1998) 相似文献
112.
We construct a series of pairs of domains in the plane and pairs of surfaces with boundary that are isospectral but not isometric.
The construction is based on the existence of finite transformation groups that are spectrally equivalent but not isomorphic.
Translated fromMatematicheskie Zametki, Vol. 63, No. 5, pp. 660–664, May, 1998.
This research was partially supported by the Russian Foundation for Basic Research and by INTAS under joint grant No. 96-01-00043. 相似文献
113.
It is proved that the center of an automorphism group Aut(FVL2) of a free vector lattice FVL2 on a set of two free generators is isomorphic to a multiplicative group of positive reals. It is shown that the free vector lattice FVL2 has an isomorphic representation by continuous piecewise linear functions of the real line; as a consequence, the ideal lattice and the root system for rectifying ideals in FVL2 are amply described. Similar results are obtained for a free vector lattice FVL2
Q
2 generated by two elements over a field of rational numbers. 相似文献
114.
Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells 下载免费PDF全文
A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias. 相似文献
115.
Solid-phase extraction (SPE) is an effective tool for the preconcentration of trace elements and their separation from various sample constituents. Octadecyl and other alkyl-bonded silica gels are most widely used for these purposes. The fundamentals of the SPE of inorganic ions are reviewed and compared with those of related techniques (liquid-liquid extraction and reversed-phase liquid chromatography). The extraction of ions in the form of chelate compounds, inorganic salts solvated by neutral reagents, and ion-pair compounds is considered. Numerous applications of SPE to the separation and preconcentration of different elements and their species, including on-line combinations with instrumental determination techniques, are described and tabulated. 相似文献
116.
E. V. Gavryushin T. I. Gorbunova A. Ya. Zapevalov V. I. Saloutin 《Russian Journal of Applied Chemistry》2006,79(5):861-864
Wetting angles and limits of thermal stability of esters derived from pentaerythritol and perfluoro-, ω-chloropolyfluoro-, and perfluoropolyethercarboxylic acids were studied. 相似文献
117.
S. A. Dieva R. M. Eliseenkova Yu. Ya. Efremov D. R. Sharafutdinova A. A. Bredikhin 《Russian Journal of Organic Chemistry》2006,42(1):12-16
Dioxirane generated in situ by reaction of chiral 1,2:4,5-di-O-isopropylidene-D-erythro-hexo-2,4-diulo-2,6-pyranose with Oxone oxidizes prochiral sulfides to the corresponding sulfoxides with an enantiomeric excess of 2 to 25%. 相似文献
118.
We study different moment characteristics of (mostly discrete) distributions: general, central, binomial, and factorial moments,
and also ordinary and factorial semi-invariants. We establish the relations that connect various kinds of “moments” of arbitrary
order, and we derive recursion formulas.
Translated fromMetody Matematicheskogo Modelirovaniya, pp. 34–41, 1998. 相似文献
119.
Experimental study of the stability of stiffened shells (review) 总被引:1,自引:0,他引:1
120.
Using the relations of the improved model of layered anisotropic shells based on the straight line assumption taking account of the thermal compression over the thickness we obtain a resolvent system of equations for shells whose properties depend on temperature. We carry out a study of the stresses in a two-layer cylindrical shell formed by winding as a function of the winding angle.
Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 35, 1992, pp. 82–85. 相似文献