全文获取类型
收费全文 | 738138篇 |
免费 | 5728篇 |
国内免费 | 1778篇 |
专业分类
化学 | 367224篇 |
晶体学 | 10666篇 |
力学 | 38197篇 |
综合类 | 26篇 |
数学 | 105676篇 |
物理学 | 223855篇 |
出版年
2021年 | 5854篇 |
2020年 | 6519篇 |
2019年 | 7316篇 |
2018年 | 13760篇 |
2017年 | 14100篇 |
2016年 | 15894篇 |
2015年 | 8072篇 |
2014年 | 12818篇 |
2013年 | 30237篇 |
2012年 | 25299篇 |
2011年 | 33751篇 |
2010年 | 23871篇 |
2009年 | 23716篇 |
2008年 | 31075篇 |
2007年 | 32970篇 |
2006年 | 24000篇 |
2005年 | 24076篇 |
2004年 | 21147篇 |
2003年 | 19619篇 |
2002年 | 18525篇 |
2001年 | 18885篇 |
2000年 | 14888篇 |
1999年 | 11442篇 |
1998年 | 9909篇 |
1997年 | 9844篇 |
1996年 | 9352篇 |
1995年 | 8419篇 |
1994年 | 8540篇 |
1993年 | 8100篇 |
1992年 | 8688篇 |
1991年 | 9117篇 |
1990年 | 8775篇 |
1989年 | 8540篇 |
1988年 | 8475篇 |
1987年 | 8316篇 |
1986年 | 7915篇 |
1985年 | 10245篇 |
1984年 | 10797篇 |
1983年 | 9095篇 |
1982年 | 9445篇 |
1981年 | 8974篇 |
1980年 | 8662篇 |
1979年 | 9069篇 |
1978年 | 9548篇 |
1977年 | 9356篇 |
1976年 | 9377篇 |
1975年 | 8873篇 |
1974年 | 8767篇 |
1973年 | 9107篇 |
1972年 | 6591篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
G. Ch. Shushkevich 《Technical Physics》1998,43(7):743-748
The electrostatic problem for a thin, unclosed spherical shell and a torus is reduced to paired summation equations in the
Legendre polynomials by means of formulas relating the spherical and toroidal harmonic functions. The paired equations are
transformed to a Fredholm integral equation of the second kind. Formulas are obtained for computing the charges of the conductors
in the form of a series in a small parameter. The capacitance is computed for certain geometrical parameters of the conductors.
Zh. Tekh. Fiz. 68, 1–6 (July 1998) 相似文献
22.
A. N. Grishkov 《Algebra and Logic》1998,37(5):294-306
Ordinary cohomologies in an algebra most often exhibit themselves either as objects that describe extensions (of algebras,
groups, or modules) or as subjects hindering the existence of algebraic constructions. We introduce the notion of nonlinear
cohomologies at a level of cochain complexes, furnish particular examples for Lie algebras, and give an interpretation of
first nonlinear cohomologies in terms of “quasiextensions” of orthogonal modules.
Translated fromAlgebra i Logika, Vol. 37, No. 5, pp. 522–541, September–October, 1998. 相似文献
23.
M. Georgelin A. Pocheau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):169-174
The polycrystalline perovskitelike manganese oxides La1-xAxMnO (A = Na, and K, ) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation
state is practically constant, at for A = Na, and for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (Tc) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates
for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie
temperature.
Received: 12 September 1997 / Revised: 18 December 1997 / Accepted: 21 January 1998 相似文献
24.
The interaction of isotactic polypropylene with ethylene propylene diene terpolymer in their blends has been investigated by use of differential scanning calorimetry, dynamic mechanical analysis, wide- and small-angle x-ray scattering, and by investigating the nucleation and kinetics of crystallization of the iPP component under the polarization microscope. It is found, that the dispersion of the EPDM component in the iPP matrix is dependent on blend composition and is maximal at 10% EPDM content. An interface layer between the two components is formed by migration of iPP molecules into the EPDM phase. A model for this interface is proposed. 相似文献
25.
An optimal control model of exhaustible resources is used to clarify the long run relationship between mineral rent and depletion cost at the industry level. A standard first order condition of the time rate of change of rents is reformulated to reveal that rent data may be used to help forecast the rise in extraction costs resulting from resource depletion. This application of the theory of exhaustible resources is illustrated using historical mineral industry rent and extraction cost data. A forecast of U.S. coal extraction costs, following the method proposed in this paper, suggests that future rates of extraction cost increases will be similar to rates experienced in the past. 相似文献
26.
C. Fallnich B. Ruffing Th. Herrmann A. Nebel R. Beigang R. Wallenstein 《Applied physics. B, Lasers and optics》1995,60(5):427-436
We report on a cw mode-locked non-critically phase matched KTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. High average signal output power of up to 950 mW over a large tuning range has been achieved. For this OPO the influence of resonator-length detuning on the output power, pulse duration and spectral bandwidth has been investigated. The measured data are in good agreement with the results of a numerical simulation using a split-step Fourier method which considers the group-velocity mismatch, the group-velocity dispersion and the self-phase modulation. The numerical simulation also describes the measured strong pump depletion and its influence on the OPO output and efficiency. 相似文献
27.
Myagchenkov V. A. Chichkanov S. V. Proskurina V. E. Myagchenkov A. V. 《Russian Journal of Applied Chemistry》2002,75(9):1485-1488
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant. 相似文献
28.
A. M. Nikitin 《Journal of Mathematical Sciences》1997,87(6):4138-4146
An explicit way for producing invariants for 6-valent graphs with rigid vertices within the framework of Kauffman's approach
to graph invariants is presented. These invariants can be used to detect the chirality of a 6-valent graph with rigid vertices.
A relevant example is considered. Bibliography: 19 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 223, 1995, pp. 251–262.
Translated by A. M. Nikitin 相似文献
29.
30.
A. K. Lopatin 《Ukrainian Mathematical Journal》1997,49(1):51-74
We consider the method of normal forms, the Bogolyubov averaging method, and the method of asymptotic decomposition proposed by Yu. A. Mitropol’skii and the author of this paper. Under certain assumptions about group-theoretic properties of a system of zero approximation, the results obtained by the method of asymptotic decomposition coincide with the results obtained by the method of normal forms or the Bogolyubov averaging method. We develop a new algorithm of asymptotic decomposition by a part of the variables and its partial case — the algorithm of averaging on a compact Lie group. For the first time, it became possible to consider asymptotic expansions of solutions of differential equations on noncommutative compact groups. 相似文献