全文获取类型
收费全文 | 2311篇 |
免费 | 244篇 |
国内免费 | 220篇 |
专业分类
化学 | 540篇 |
晶体学 | 3篇 |
力学 | 202篇 |
综合类 | 46篇 |
数学 | 1409篇 |
物理学 | 575篇 |
出版年
2024年 | 7篇 |
2023年 | 20篇 |
2022年 | 112篇 |
2021年 | 108篇 |
2020年 | 104篇 |
2019年 | 78篇 |
2018年 | 64篇 |
2017年 | 82篇 |
2016年 | 56篇 |
2015年 | 73篇 |
2014年 | 114篇 |
2013年 | 158篇 |
2012年 | 106篇 |
2011年 | 136篇 |
2010年 | 100篇 |
2009年 | 175篇 |
2008年 | 145篇 |
2007年 | 136篇 |
2006年 | 129篇 |
2005年 | 110篇 |
2004年 | 105篇 |
2003年 | 101篇 |
2002年 | 70篇 |
2001年 | 54篇 |
2000年 | 60篇 |
1999年 | 57篇 |
1998年 | 66篇 |
1997年 | 59篇 |
1996年 | 42篇 |
1995年 | 28篇 |
1994年 | 27篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有2775条查询结果,搜索用时 15 毫秒
51.
52.
Jaume Llibre Marco Antonio Teixeira Joan Torregrosa 《Mathematical Physics, Analysis and Geometry》2007,10(3):237-249
The goal of this paper is double. First, we illustrate a method for studying the bifurcation of limit cycles from the continuum
periodic orbits of a k-dimensional isochronous center contained in ℝ
n
with n ⩾ k, when we perturb it in a class of differential systems. The method is based in the averaging theory. Second, we consider a particular polynomial differential
system in the plane having a center and a non-rational first integral. Then we study the bifurcation of limit cycles from
the periodic orbits of this center when we perturb it in the class of all polynomial differential systems of a given degree.
As far as we know this is one of the first examples that this study can be made for a polynomial differential system having
a center and a non-rational first integral.
The first and third authors are partially supported by a MCYT/FEDER grant MTM2005-06098-C01, and by a CIRIT grant number 2005SGR-00550.
The second author is partially supported by a FAPESP–BRAZIL grant 10246-2. The first two authors are also supported by the
joint project CAPES–MECD grant HBP2003-0017. 相似文献
53.
54.
环境温度对燃气轮机功热并供装置及联合循环变工况性能的影响 总被引:14,自引:0,他引:14
采用动力机械变工况性能解析分析方法,研究了大气温度变化对燃气轮机功热并供和联合循环装置性能影响.指出燃气轮机在带有余热利用的条件下,大气温度的影响明显减弱,并对不同燃气轮机设计参数和蒸汽设计参数影响做了分析比较。 相似文献
55.
51.IntroductionLetF=[O,1],foranya,beF,definea b=max{a,b},a*b=min{a,b}.Mn(F)standsforthesetofa1lthenthordermatrixesinF,matrixAinMn(F)iscalledFuzzymatrixA.Letrbeanynon-negativeinteger.lnannthordermatrix,exclusiveofthefirstrow,theelementsofeveryotherrowarethee1ementsoftheprecedingrowthatcirculaterightwardr-co1umns.Thisnthordermatrixisannthorderr-circulantFuzzymatrix(alsocalledgenearLizedcirculantFuzzymatrix)-Wecallrthecircu1antindexofr-circulantFuzzymatrix.Inthebooklistedin[1j,thisisgiven:… 相似文献
56.
Zhang Xiang 《数学年刊B辑(英文版)》1997,18(4):429-434
ONTWOCONJECTURESOFTHEQUADRATICDIFFERENTIALSYSTEMSZHANGXIANG*AbstractManuscriptreceivedSeptember29,1995.*InstituteofMathematic... 相似文献
57.
Ken-ichi Kawarabayashi 《Discrete Mathematics》2010,310(20):2655-2661
A graph G is said to have property P(2,k) if given any k+2 distinct vertices a,b,v1,…,vk, there is a path P in G joining a and b and passing through all of v1,…,vk. A graph G is said to have property C(k) if given any k distinct vertices v1,…,vk, there is a cycle C in G containing all of v1,…,vk. It is shown that if a 4-connected graph G is embedded in an orientable surface Σ (other than the sphere) of Euler genus eg(G,Σ), with sufficiently large representativity (as a function of both eg(G,Σ) and k), then G possesses both properties P(2,k) and C(k). 相似文献
58.
For n∈N and D⊆N, the distance graph has vertex set {0,1,…,n−1} and edge set {ij∣0≤i,j≤n−1,|j−i|∈D}. Note that the important and very well-studied circulant graphs coincide with the regular distance graphs.A fundamental result concerning circulant graphs is that for these graphs, a simple greatest common divisor condition, their connectivity, and the existence of a Hamiltonian cycle are all equivalent. Our main result suitably extends this equivalence to distance graphs. We prove that for a finite set D of order at least 2, there is a constant cD such that the greatest common divisor of the integers in D is 1 if and only if for every n, has a component of order at least n−cD if and only if for every n≥cD+3, has a cycle of order at least n−cD. Furthermore, we discuss some consequences and variants of this result. 相似文献
59.
60.
We propose a new and simple estimating equation for the parameters in median regression models with designed censoring variables, and then apply the empirical log likelihood ratio statistic to construct confidence region for the parameters. The empirical log likelihood ratio statistic is shown to have a standard chi-square distribution, which makes this method easy to implement. At the same time, another empirical log likelihood ratio statistic is proposed based on an existing estimating equation and the limiting distribution of the empirical likelihood ratio statistic is shown to be a sum of weighted chi-square distributions. We compare the performance of the empirical likelihood confidence region based on the new estimating equation, with that based on the existing estimating equation and a normal approximation method by simulation studies. 相似文献