全文获取类型
收费全文 | 21937篇 |
免费 | 3579篇 |
国内免费 | 1770篇 |
专业分类
化学 | 4459篇 |
晶体学 | 56篇 |
力学 | 2826篇 |
综合类 | 556篇 |
数学 | 10828篇 |
物理学 | 8561篇 |
出版年
2024年 | 34篇 |
2023年 | 214篇 |
2022年 | 420篇 |
2021年 | 526篇 |
2020年 | 563篇 |
2019年 | 523篇 |
2018年 | 525篇 |
2017年 | 772篇 |
2016年 | 888篇 |
2015年 | 695篇 |
2014年 | 1205篇 |
2013年 | 1613篇 |
2012年 | 1169篇 |
2011年 | 1358篇 |
2010年 | 1219篇 |
2009年 | 1386篇 |
2008年 | 1537篇 |
2007年 | 1599篇 |
2006年 | 1318篇 |
2005年 | 1195篇 |
2004年 | 1157篇 |
2003年 | 970篇 |
2002年 | 926篇 |
2001年 | 737篇 |
2000年 | 646篇 |
1999年 | 605篇 |
1998年 | 531篇 |
1997年 | 465篇 |
1996年 | 397篇 |
1995年 | 387篇 |
1994年 | 255篇 |
1993年 | 231篇 |
1992年 | 171篇 |
1991年 | 205篇 |
1990年 | 127篇 |
1989年 | 87篇 |
1988年 | 115篇 |
1987年 | 79篇 |
1986年 | 65篇 |
1985年 | 68篇 |
1984年 | 49篇 |
1983年 | 31篇 |
1982年 | 34篇 |
1981年 | 40篇 |
1980年 | 34篇 |
1979年 | 31篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
Ding-kang WANG~ Yan ZHANG Key Laboratory of Mathematics Mechanization Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2007,50(10):1441-1450
We present an algorithm to decompose a polynomial system into a finite set of normal ascending sets such that the set of the zeros of the polynomial system is the union of the sets of the regular zeros of the normal ascending sets.If the polynomial system is zero dimensional,the set of the zeros of the polynomials is the union of the sets of the zeros of the normal ascending sets. 相似文献
212.
We propose objectives consisting of two mirrors with central holes for passage of a light beam. The optical layout ensures
multiple reflection of rays from both mirrors. We consider several approaches to calculating the design parameters for which
three and four aberrations do not occur. The objectives can be used in optical devices operating in the UV and IR regions
of the spectrum.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 267–270, March–April, 2007. 相似文献
213.
We investigate a multicomponent anisotropic liquid system. The first spatial moment of the direct correlation function is taken into account to obtain asymptotic expressions for the pairwise correlation functions. In this approximation, we obtain the pairwise correlation functions that describe the system behavior not only in the critical-state neighborhood but also in the noncritical domain. We show that the critical parameters for the anisotropic system differ from those for the isotropic system. 相似文献
214.
通过两个积分 (一个是不定积分 ,一个是定积分 )及一个极限 ,说明如何灵活使用积分法解决积分问题 ,方法灵活、巧妙 ,适用范围广 . 相似文献
215.
We consider quasi-isometric mappings of domains in multidimensional Euclidean spaces. We establish that a mapping depends continuously in the sense of the topology of Sobolev classes on its metric tensor to within isometry of the space. In the space of metric tensors we take the topology determined by means of almost everywhere convergence. We show that if the metric tensor of a mapping is continuous then the length of the image of a rectifiable curve is determined by the same formula as in the case of mappings with continuous derivatives. (Continuity of the metric tensor of a mapping does not imply continuity of its derivatives.) 相似文献
216.
Jie-Fang Zhang 《Acta Mechanica Solida Sinica》1991,4(2):139-151
Based on D'Alembert's principle of a mechanical system relative to non-inertial frame and by introducing the concept of the generalized inertial potential, new forms of differential equations of motion of a mechanical system with holonomic and the non-holonomic constraints relative to the non-inertial frame are obtained. The merits and demerits between our method and the Newtonian dynamic method as well as the analytic dynamic method are discussed comparatively. Finally, two examples are given to illustrate the application of the motive differential equations in the new forms. 相似文献
217.
In this paper, we discuss the controllability of a nonlinear degenerate parabolic system with bilinear control. Based on the shrinking property of the solutions, we prove that the system is not globally approximately controllable. Furthermore, we give an approximate null controllability result. We also prove that the system is not globally exactly null controllable by a comparison principle. 相似文献
218.
一类拟线性大系统的稳定性 总被引:1,自引:0,他引:1
彭晓林 《新疆大学学报(理工版)》1991,8(1):41-45
本文应用大系统的分解方法和一个推广的不等式,研究了一类拟线性大系统的稳定性问题,所得结果简洁、易于验证,且推导过程不复杂,最后给出了应用实例。 相似文献
219.
Bünyamin Demir Vakif Dzhafarov ?ahin Koçak Mehmet Üreyen 《Journal of Mathematical Analysis and Applications》2007,332(1):735-740
We give an iterated function system (IFS) on the plane with the circle as attractor. In doing this, we also give a sufficient condition for radially contracting functions on the plane (or on Rn) to be a contraction. A counterexample shows that radial contractiveness is not enough to be a contraction. 相似文献