全文获取类型
收费全文 | 30028篇 |
免费 | 1497篇 |
国内免费 | 1927篇 |
专业分类
化学 | 3492篇 |
晶体学 | 97篇 |
力学 | 654篇 |
综合类 | 222篇 |
数学 | 8318篇 |
物理学 | 3255篇 |
综合类 | 17414篇 |
出版年
2024年 | 31篇 |
2023年 | 169篇 |
2022年 | 281篇 |
2021年 | 362篇 |
2020年 | 403篇 |
2019年 | 488篇 |
2018年 | 396篇 |
2017年 | 533篇 |
2016年 | 568篇 |
2015年 | 579篇 |
2014年 | 1167篇 |
2013年 | 1416篇 |
2012年 | 1446篇 |
2011年 | 1673篇 |
2010年 | 1446篇 |
2009年 | 1800篇 |
2008年 | 2074篇 |
2007年 | 2303篇 |
2006年 | 2089篇 |
2005年 | 1778篇 |
2004年 | 1489篇 |
2003年 | 1375篇 |
2002年 | 1313篇 |
2001年 | 1081篇 |
2000年 | 909篇 |
1999年 | 803篇 |
1998年 | 695篇 |
1997年 | 600篇 |
1996年 | 566篇 |
1995年 | 413篇 |
1994年 | 435篇 |
1993年 | 371篇 |
1992年 | 343篇 |
1991年 | 305篇 |
1990年 | 215篇 |
1989年 | 211篇 |
1988年 | 187篇 |
1987年 | 133篇 |
1986年 | 76篇 |
1985年 | 123篇 |
1984年 | 126篇 |
1983年 | 73篇 |
1982年 | 106篇 |
1981年 | 125篇 |
1980年 | 84篇 |
1979年 | 75篇 |
1978年 | 71篇 |
1977年 | 48篇 |
1976年 | 27篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
131.
Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was
investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer
and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider
constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various
types of compounds is documented by various examples. 相似文献
132.
基于傅立叶变换轮廓术的物面相位提取 总被引:1,自引:0,他引:1
采用傅立叶变换轮廓术,针对基频提取的关键技术采用逐行傅立叶变换,准确提取基频信息的方法恢复相位信息.在此基础上,以未畸变条纹为基准,得出被测物体的真实位相值.该方法只需一幅条纹图,节约了测量时间.实验证明可实现无接触面型的自动传感. 相似文献
133.
This paper investigates the existence of positive solutions of a singular boundary value problem with negative exponent similar
to standard Emden-Fowler equation. A necessary and sufficient condition for the existence of C[0, 1] positive solutions as
well as C1[0, 1] positive solutions is given by means of the method of lower and upper solutions with the Schauder fixed point theorem. 相似文献
134.
Banach空间二阶周期边值问题解的存在性 总被引:2,自引:0,他引:2
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。 相似文献
135.
Xian Xu 《Journal of Mathematical Analysis and Applications》2004,291(2):673-689
In this paper, some multiplicity results for positive solutions of some singular semi-positone three-point boundary value problem be obtained by using the fixed point index method. 相似文献
136.
Zhimin He 《Journal of Mathematical Analysis and Applications》2004,296(1):97-109
In this paper, by means of a new twin fixed-point theorem in a cone, the existence of at least two positive solutions of m-point boundary value problem for second order dynamic equations on time scales is considered. 相似文献
137.
Giuseppe Gaeta 《Annals of Physics》2004,312(2):511-540
In the Landau theory of phase transitions one considers an effective potential Φ whose symmetry group G and degree d depend on the system under consideration; generally speaking, Φ is the most general G-invariant polynomial of degree d. When such a Φ turns out to be too complicate for a direct analysis, it is essential to be able to drop unessential terms, i.e., to apply a simplifying criterion. Criteria based on singularity theory exist and have a rigorous foundation, but are often very difficult to apply in practice. Here we consider a simplifying criterion (as stated by Gufan) and rigorously justify it on the basis of classical Lie-Poincaré theory as far as one deals with fixed values of the control parameter(s) in the Landau potential; when one considers a range of values, in particular near a phase transition, the criterion has to be accordingly partially modified, as we discuss. We consider some specific cases of group G as examples, and study in detail the application to the Sergienko-Gufan-Urazhdin model for highly piezoelectric perovskites. 相似文献
138.
We present a general risk model where the aggregate claims, as well as the premium function, evolve by jumps. This is achieved by incorporating a Lévy process into the model. This seeks to account for the discrete nature of claims and asset prices. We give several explicit examples of Lévy processes that can be used to drive a risk model. This allows us to incorporate aggregate claims and premium fluctuations in the same process. We discuss important features of such processes and their relevance to risk modeling. We also extend classical results on ruin probabilities to this model. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
139.
Summary Our purpose is to extend results due to P. Chandra and L. Leindler concerning the order of approximation by means of Fourier series for functions belonging to generalized Lipschitz-classes. 相似文献
140.
进一步研究了具有三个cM公共值的亚纯函数的唯一性,改进了H.Ueda和仪洪勋等人的有关结果. 相似文献