全文获取类型
收费全文 | 22238篇 |
免费 | 701篇 |
国内免费 | 92篇 |
专业分类
化学 | 14297篇 |
晶体学 | 190篇 |
力学 | 344篇 |
数学 | 3364篇 |
物理学 | 4836篇 |
出版年
2022年 | 153篇 |
2021年 | 219篇 |
2020年 | 368篇 |
2019年 | 336篇 |
2018年 | 294篇 |
2017年 | 268篇 |
2016年 | 577篇 |
2015年 | 506篇 |
2014年 | 593篇 |
2013年 | 1176篇 |
2012年 | 1104篇 |
2011年 | 1276篇 |
2010年 | 808篇 |
2009年 | 700篇 |
2008年 | 1121篇 |
2007年 | 1052篇 |
2006年 | 1096篇 |
2005年 | 968篇 |
2004年 | 817篇 |
2003年 | 646篇 |
2002年 | 711篇 |
2001年 | 422篇 |
2000年 | 399篇 |
1999年 | 361篇 |
1998年 | 303篇 |
1997年 | 287篇 |
1996年 | 317篇 |
1995年 | 269篇 |
1994年 | 287篇 |
1993年 | 264篇 |
1992年 | 243篇 |
1991年 | 213篇 |
1990年 | 206篇 |
1989年 | 167篇 |
1988年 | 151篇 |
1987年 | 145篇 |
1986年 | 143篇 |
1985年 | 238篇 |
1984年 | 238篇 |
1983年 | 186篇 |
1982年 | 255篇 |
1981年 | 213篇 |
1980年 | 188篇 |
1979年 | 215篇 |
1978年 | 210篇 |
1977年 | 206篇 |
1976年 | 216篇 |
1975年 | 176篇 |
1974年 | 158篇 |
1973年 | 157篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Frank W. Schmidt 《Linear and Multilinear Algebra》1991,30(3):229-230
This section appears from time to time. Contributions are invited, and should be submitted to R. C. Thompson, Mathematics Department, University of California, Santa Barbara, CA 93106. 相似文献
72.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
73.
Dashan Huang Yoshitaka Kai Frank J. Fabozzi Masao Fukushima 《European Journal of Operational Research》2007
This paper presents a model for optimally designing a collateralized mortgage obligation (CMO) with a planned amortization class (PAC)-companion structure using dynamic cash reserve. In this structure, the mortgage pool’s cash flow is allocated by rule to the two bond classes such that PAC bondholders receive substantial prepayment protection, that protection being provided by the companion bondholders. The structure we propose provides greater protection to the PAC bondholders than current structures during periods of rising interest rates when this class of bondholders faces greater extension risk. We do so by allowing a portion of the cash flow from the collateral to be reserved to meet the PAC’s scheduled cash flow in subsequent periods. The greater protection is provided by the companion bondholders exposure to interest loss. To tackle this problem, we transform the problem of designing the optimal PAC-companion structure into a standard stochastic linear programming problem which can be solved efficiently. Moreover, we present an extended model by considering the quality of the companion bond and by relaxing the PAC bondholder shortfall constraint. Based on numerical experiments through Monte Carlo simulation, we show the utility of the proposed model. 相似文献
74.
In [NR] the authors introduced the notion of superstable operators on a Banach space E using ultrapowers Eu of E. In [HR] this notion was extended to strongly continuous one-parameter semigroups again by means of ultrapowers.It is the aim of the present paper to give an equivalent intrinsic definition of superstability (without the reference to ultrapowers). This definition allows us to improve the results of [NR] as well as of [HR]. We apply our results to semigroups of positive linear operators on Banach lattices and C*-algebras, respectively. 相似文献
75.
Søren Riis 《Archive for Mathematical Logic》1997,36(3):157-188
For each there exists a model of which satisfies the Count() principle. Furthermore, if contains all prime factors of there exist and a bijective map mapping onto . A corollary is a complete classification of the Count() versus Count() problem. Another corollary shows that the pigeon-hole principle for injective maps does not follow from any of the Count() principles. This solves an open question [Ajtai 94].
Received August 16, 1994 / Revised version received April 29, 1996 相似文献
76.
Gabor Schmera Adi Bulsara David Pierson Frank Moss Enrico Di Cera 《Journal of statistical physics》1993,71(5-6):1179-1190
We consider the class of experiments which can be characterized by a Fokker-PIanck dynamics corresponding to the overdamped motion of a state point in a suitable stochastic potential. We assume that the general form of the potential is known (or can be guessed with reasonable accuracy), but that its parameters are to be determined experimentally by measurements made with a noisy instrument. This possible method for determining the potential parameters, which exploits the system's own internal stochastic motion in order to explore rapidly its available parameter space, is substantially more efficient than traditional methods involving time averages of single point measurements, and yet does not appear to have been previously considered. The method could be important when, for example, the experiment must be completed in a limited time owing either to the expense of the experimental materials or to the temporary stationarity of the preparation, situations which are commonly encountered in experimental biochemistry and biology. 相似文献
77.
Presented by R. Freese. 相似文献
78.
Örn Helgason Haraldur P. Gunnlaugsson Siguröur Steinthorsson Steen Mørup 《Hyperfine Interactions》1992,70(1-4):981-984
Mössbauer spectroscopy of basalt lava samples, exhibiting reversible thermal magnetization (JS-T) curves with Curie temperatures of about 580°C, has revealed considerable amounts of maghemite (γ-Fe2O3) in many samples. In view of the expected instability, of maghemite at temperatures above 350°C, this reversibility is rather surprising. Here we report Mössbauer studies on heated lava samples, showing high content of maghemite. The samples were kept at 600°C in oxidizing, reducing, and inactive atmospheres, respectively, for different lengths of time, and then analyzed with Mössbauer spectroscopy at room temperature. The Mössbauer spectra showed that maghemite is stable in the oxidizing atmosphere for at least several hours. In the inactive atmosphere a considerable amount of maghemite still exists after two hours heating. In the reducing atmosphere maghemite had transformed to magnetite after only 30 minutes. 相似文献
79.
80.
The sulphur K-edge x-ray absorption spectra of SO2 multilayer and of SO2 submonolayer adsorbed on Cu(100) are analysed. It is found that the dominant spectral features are of a molecular origin. The results support earlier findings that the SO2 molecule stands perpendicular to the surface. Use of non-selfconsistent potentials does not lead to a good quantitative agreement between theory and experiment. 相似文献