全文获取类型
收费全文 | 396471篇 |
免费 | 4474篇 |
国内免费 | 1786篇 |
专业分类
化学 | 219108篇 |
晶体学 | 6439篇 |
力学 | 16181篇 |
综合类 | 72篇 |
数学 | 42236篇 |
物理学 | 118695篇 |
出版年
2020年 | 3273篇 |
2019年 | 3584篇 |
2018年 | 4440篇 |
2017年 | 4559篇 |
2016年 | 6719篇 |
2015年 | 4358篇 |
2014年 | 6670篇 |
2013年 | 16974篇 |
2012年 | 13329篇 |
2011年 | 16267篇 |
2010年 | 11544篇 |
2009年 | 11408篇 |
2008年 | 14960篇 |
2007年 | 14927篇 |
2006年 | 14009篇 |
2005年 | 12736篇 |
2004年 | 11489篇 |
2003年 | 10350篇 |
2002年 | 10064篇 |
2001年 | 11820篇 |
2000年 | 9019篇 |
1999年 | 6728篇 |
1998年 | 5424篇 |
1997年 | 5351篇 |
1996年 | 5285篇 |
1995年 | 4759篇 |
1994年 | 4757篇 |
1993年 | 4502篇 |
1992年 | 5310篇 |
1991年 | 5274篇 |
1990年 | 5036篇 |
1989年 | 5005篇 |
1988年 | 4943篇 |
1987年 | 4892篇 |
1986年 | 4751篇 |
1985年 | 6216篇 |
1984年 | 6315篇 |
1983年 | 5120篇 |
1982年 | 5405篇 |
1981年 | 5238篇 |
1980年 | 4828篇 |
1979年 | 5324篇 |
1978年 | 5493篇 |
1977年 | 5631篇 |
1976年 | 5478篇 |
1975年 | 5010篇 |
1974年 | 5062篇 |
1973年 | 5089篇 |
1972年 | 3769篇 |
1968年 | 3223篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
The problem of the vector and axial-vector dominance of weak interactions within the framework of the quark model of superconductivity type is discussed. 相似文献
22.
23.
V. L. Topunov 《Acta Appl Math》1989,16(2):191-206
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented. 相似文献
24.
G. L. Booth 《Acta Mathematica Hungarica》1989,54(3-4):201-208
25.
26.
L. A. Khalfin 《Journal of Mathematical Sciences》1987,36(5):616-626
The article surveys the main results of the statistical approach to the solution of ill-posed problems of mathematical physics, in application to specific ill-posed inverse problems in geophysics.Invited paper presented at the International Seminar on Mathematical Foundations of the Interpretation of Geophysical Fields, Moscow, May–June 1972.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 79, pp. 67–81, 1978. 相似文献
27.
Rajiv Manohar G. Tripathi A.K. Srivastava A.K. Prajapati 《Journal of Physics and Chemistry of Solids》2006,67(11):2300-2304
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared. 相似文献
28.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this
addendum is to present a correct argument for it. 相似文献
29.
Mark L. Agranovsky E. K. Narayanan 《Proceedings of the American Mathematical Society》2006,134(7):2117-2123
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.
30.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献