全文获取类型
收费全文 | 106690篇 |
免费 | 7741篇 |
国内免费 | 9243篇 |
专业分类
化学 | 42361篇 |
晶体学 | 635篇 |
力学 | 9374篇 |
综合类 | 1632篇 |
数学 | 33434篇 |
物理学 | 36238篇 |
出版年
2023年 | 867篇 |
2022年 | 1762篇 |
2021年 | 2002篇 |
2020年 | 2144篇 |
2019年 | 2337篇 |
2018年 | 2083篇 |
2017年 | 2456篇 |
2016年 | 2790篇 |
2015年 | 2372篇 |
2014年 | 3570篇 |
2013年 | 6808篇 |
2012年 | 4252篇 |
2011年 | 4815篇 |
2010年 | 4069篇 |
2009年 | 5944篇 |
2008年 | 6538篇 |
2007年 | 7047篇 |
2006年 | 6311篇 |
2005年 | 5328篇 |
2004年 | 4774篇 |
2003年 | 4963篇 |
2002年 | 5076篇 |
2001年 | 3957篇 |
2000年 | 3810篇 |
1999年 | 3381篇 |
1998年 | 3210篇 |
1997年 | 2408篇 |
1996年 | 2167篇 |
1995年 | 1930篇 |
1994年 | 1870篇 |
1993年 | 1504篇 |
1992年 | 1517篇 |
1991年 | 1135篇 |
1990年 | 991篇 |
1989年 | 836篇 |
1988年 | 747篇 |
1987年 | 633篇 |
1986年 | 553篇 |
1985年 | 595篇 |
1984年 | 590篇 |
1983年 | 310篇 |
1982年 | 467篇 |
1981年 | 519篇 |
1980年 | 379篇 |
1979年 | 378篇 |
1978年 | 306篇 |
1977年 | 291篇 |
1976年 | 212篇 |
1974年 | 140篇 |
1973年 | 152篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Steven J. Sepanski 《Journal of Theoretical Probability》1997,10(4):1053-1063
For independent identically distributed random vectors belonging to the generalized Domain of Attraction of the multivariate normal law, we define two partial sum processes analogous to that of Donsker's Theorem. We prove that each converges in distribution to a Brownian Motion in the space of continuous functions. One process uses nonrandom operator normalization, and the other is a studentization of the first, using normalization by the empirical covariance operator. 相似文献
992.
V. A. Potemkin M. A. Grishina E. V. Bartashevich 《Journal of Structural Chemistry》2007,48(1):155-160
The BiS algorithm is suggested for modeling the drug molecule orientation within a receptor cavity. It is based on the assumption of complementarity of the field created by biologically active compounds and the field of the responsive receptor. The comparison of predicted orientations of various biologically active compounds on the relevant receptors with the data of X-ray structural studies (Protein Data Bank) reveals that the results obtained with this approach surpasses those reported in the literature. The suggested technique made it possible to elucidate the details of the action mechanism of DNA antimetabolites, dihydrofolate reductase inhibitors. The dependence of the activity on the structural parameters of “ligand-receptor” complexes is determined. 相似文献
993.
R. Souzy B. Ameduri B. Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5077-5097
The radical co‐ and terpolymerization of 4‐[(α,β,β‐trifluorovinyl)oxy]bromo benzene (TFVOBB) with 1,1‐difluoroethylene (or vinylidene fluoride, VDF, or VF2), hexafluoropropene (HFP), perfluoromethyl vinyl ether (PMVE), and chlorotrifluroroethylene (CTFE) is presented. Although TFVOBB could be thermocyclodimerized, it could not homopolymerize under radical initiation. TFVOBB could be copolymerized in solution under a radical initiator with VDF or CTFE comonomers, while its copolymerization with HFP or PMVE were unsuccessful. The terpolymerization of TFVOBB with VDF and HFP, or VDF and PMVE, or VDF and CTFE also led to original fluorinated terpolymers bearing bromoaromatic side‐groups. The conditions of co‐ and terpolymerization were optimized in terms of the nature of the radical initiators, and of the nature of solvents (fluorinated or nonhalogenated). Various monomer concentrations in the co‐ and terpolymers were assessed by 19F and 1H‐NMR spectroscopy. The thermal and physico chemical properties were also studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5077–5097, 2004 相似文献
994.
因子分析在企业竞争力评价中的应用 总被引:22,自引:1,他引:21
根据因子分析原理,建立了企业竞争力的规模因子、效益因子和成长因子得分模型。通过现实竞争力和潜在竞争力分析,实现了企业竞争力和可持续发展的评价。 相似文献
995.
本利用矩阵给出了几类数列的通项公式的求法,把数列通项公式的求法转化为矩阵幂的计算,思路简单、计算简便,并能判别其敛散性。 相似文献
996.
关于RNP和SCS的若干等价条件 总被引:1,自引:0,他引:1
使用切片方法,讨论了Banach空间中有界闭凸子集的RNP和SCS的若干等价条件. 相似文献
997.
998.
Yang Lingxia Ge Debiao Wei Bing 《International Journal of Infrared and Millimeter Waves》2003,24(11):1893-1897
A modified formulation for fringe component of diffraction coefficient is implemented to TD-EEC method. An example of diffraction by perfectly conducting plate is used to illustrate our scheme. Comparing with the FDTD results we observe that the improved expression for fringe component is more accurate than that of Michaeli's formulation. This high frequency time domain technique is available for treating the bistatic scattering problems for millimeter waves. 相似文献
999.
In distinction from the well-known double-negation embeddings of the classical logic we consider some variants of single-negation embeddings and describe some classes of superintuitionistic first-order predicate logics in which the classical first-order calculus is interpretable in such a way. Also we find the minimal extensions of Heyting's logic in which the classical predicate logic can be embedded by means of these translations. 相似文献
1000.
Summary We discuss some recent theoretical studies of the kinetics of the collapse transition in homopolymers. An isolated polymer
is modelled using computer simulation, and a time-dependent mean-field theory. The mean-field theory is analysed analytically
for early stages, and for short polymers the equations are studied numerically. The results of simulation and theory are compared
yielding, we argue, a consistent physical picture. Quantitative comparisons are not yet given, but seem relatively promising.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4– 1994. 相似文献