全文获取类型
收费全文 | 17833篇 |
免费 | 3097篇 |
国内免费 | 2697篇 |
专业分类
化学 | 13789篇 |
晶体学 | 234篇 |
力学 | 1127篇 |
综合类 | 197篇 |
数学 | 2306篇 |
物理学 | 5974篇 |
出版年
2024年 | 39篇 |
2023年 | 304篇 |
2022年 | 613篇 |
2021年 | 620篇 |
2020年 | 709篇 |
2019年 | 748篇 |
2018年 | 629篇 |
2017年 | 570篇 |
2016年 | 891篇 |
2015年 | 930篇 |
2014年 | 1034篇 |
2013年 | 1330篇 |
2012年 | 1562篇 |
2011年 | 1630篇 |
2010年 | 1199篇 |
2009年 | 1164篇 |
2008年 | 1292篇 |
2007年 | 1053篇 |
2006年 | 924篇 |
2005年 | 863篇 |
2004年 | 711篇 |
2003年 | 633篇 |
2002年 | 724篇 |
2001年 | 610篇 |
2000年 | 422篇 |
1999年 | 376篇 |
1998年 | 320篇 |
1997年 | 259篇 |
1996年 | 247篇 |
1995年 | 225篇 |
1994年 | 189篇 |
1993年 | 148篇 |
1992年 | 134篇 |
1991年 | 117篇 |
1990年 | 85篇 |
1989年 | 63篇 |
1988年 | 50篇 |
1987年 | 46篇 |
1986年 | 24篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 7篇 |
1981年 | 17篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1974年 | 6篇 |
1957年 | 5篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
2.
Zeng Qing-Wei Wen Zhuo-Yu Fu Jun-Feng Zhou Nan-Run 《International Journal of Theoretical Physics》2021,60(9):3306-3333
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution... 相似文献
3.
4.
Pengjin Qin Li-An Wang Prof. Joseph M. O'Connor Prof. Kim K. Baldridge Yifan Li Burak Tufekci Jiyue Chen Prof. Arnold L. Rheingold 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18114-18121
Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. 相似文献
5.
6.
Qin Yin Shou-Guo Wang Xiao-Wei Liang De-Wei Gao Jun Zheng Shu-Li You 《Chemical science》2015,6(7):4179-4183
An organocatalytic asymmetric chlorinative dearomatization of naphthols was realized for the first time, providing chiral naphthalenones with a Cl-containing all-substituted stereocenter in excellent yields and enantioselectivity (up to 97% yield and 96% ee). The reaction features mild reaction conditions, good tolerance of diverse functional groups and simple reaction operation. 相似文献
7.
讨论一类非齐次非线性椭圆边界值问题.利用极大值原理证明了该问题解的梯度估计.作为它的应用得到了解的效率比估计. 相似文献
8.
9.
10.