首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   542篇
  免费   26篇
  国内免费   50篇
化学   20篇
力学   10篇
综合类   11篇
数学   555篇
物理学   22篇
  2024年   1篇
  2023年   14篇
  2022年   8篇
  2021年   7篇
  2020年   8篇
  2019年   18篇
  2018年   9篇
  2017年   17篇
  2016年   11篇
  2015年   8篇
  2014年   31篇
  2013年   67篇
  2012年   9篇
  2011年   28篇
  2010年   24篇
  2009年   36篇
  2008年   46篇
  2007年   38篇
  2006年   32篇
  2005年   26篇
  2004年   25篇
  2003年   22篇
  2002年   26篇
  2001年   14篇
  2000年   25篇
  1999年   10篇
  1998年   15篇
  1997年   12篇
  1996年   10篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1985年   2篇
  1981年   1篇
  1975年   1篇
排序方式: 共有618条查询结果,搜索用时 31 毫秒
1.
We show that there is no (95, 40, 12, 20) strongly regular graph and, consequently, there is no (96, 45, 24, 18) strongly regular graph, no nontrivial regular two‐graph on 96 vertices, and no partial geometry pg(4, 9, 2). The main idea of the result is based on the star complement technique and requires a moderate amount of computation.  相似文献   
2.
3.
The present work investigates Ca2+‐crosslinked nanofibrillated cellulose hydrogels as potential hemostatic wound dressings by studying core interactions between the materials and a central component of wounds and wound healing—the blood. Hydrogels of wood‐derived anionic nanofibrillated cellulose (NFC) and NFC hydrogels that incorporate kaolin or collagen are studied in an in vitro whole blood model and with platelet‐free plasma assays. The evaluation of thrombin and factor XIIa formation, platelet reduction, and the release of activated complement system proteins, shows that the NFC hydrogel efficiently triggered blood coagulation, with a rapid onset of clot formation, while displaying basal complement system activation. By using the NFC hydrogel as a carrier of kaolin, the onset of hemostasis is further boosted, while the NFC hydrogel containing collagen exhibits blood activating properties comparable to the anionic NFC hydrogel. The herein studied NFC hydrogels demonstrate great potential for being part of advanced wound healing dressings that can be tuned to target certain wounds (e.g., strongly hemorrhaging ones) or specific phases of the wound healing process for optimal wound management.  相似文献   
4.
5.
In [1 Bannai, E. (1991). Subschemes of some association schemes. J. Algebra 14:167188.[Crossref], [Web of Science ®] [Google Scholar]], Bannai presents a fusion condition and uses this to consider central Schur rings (S-rings) over the simple groups PSL(2,q) where q is a prime power. In this paper, we concretely describe all such S-rings in terms of symmetric S-rings over cyclic groups. The final section discusses counting these.  相似文献   
6.
It is shown that the matrix sequence generated by Euler's method starting from the identity matrix converges to the principal pth root of a square matrix, if all the eigenvalues of the matrix are in a region including the one for Newton's method given by Guo in 2010. The convergence is cubic if the matrix is invertible. A modification version of Euler's method using the Schur decomposition is developed. Numerical experiments show that the modified algorithm has the overall good numerical behavior.  相似文献   
7.
Assume G is a finite group and H a subgroup of G. If there exists a subgroup K of G such that G = HK and HK = 1, then K is said to be a complement to H in G. A finite p-group G is called an NC-group if all its proper normal subgroups not contained in Φ(G) have complements. In this paper, some properties of NC-groups are investigated and some classes of NC-groups are classified.  相似文献   
8.
In this paper, we classify all capable nilpotent Lie algebras with the derived subalgebra of dimension 2 over an arbitrary field. Moreover, the explicit structure of such Lie algebras of class 3 is given.  相似文献   
9.
Symplectic self-adjointness of infinite dimensional Hamiltonian operators is studied, the necessary and sufficient conditions are given. Using the relatively bounded perturbation, the sufficient conditions about symplectic self-adjointness are shown.  相似文献   
10.
Affine semigroups are convex sets on which there exists an associative binary operation which is affine separately in either variable. They were introduced by Cohen and Collins in 1959. We look at examples of affine semigroups which are of interest to matrix and operator theory and we prove some new results on the extreme points and the absorbing elements of certain types of affine semigroups. Most notably we improve a result of Wendel that every invertible element in a compact affine semigroup is extreme by extending this result to linearly bounded affine semigroups.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号