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   210篇
  免费   9篇
  国内免费   2篇
化学   139篇
力学   5篇
数学   40篇
物理学   37篇
  2023年   1篇
  2022年   8篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   9篇
  2017年   5篇
  2016年   12篇
  2015年   14篇
  2014年   10篇
  2013年   15篇
  2012年   20篇
  2011年   26篇
  2010年   19篇
  2009年   9篇
  2008年   10篇
  2007年   6篇
  2006年   6篇
  2005年   8篇
  2004年   5篇
  2003年   5篇
  2002年   2篇
  2000年   3篇
  1999年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1986年   1篇
  1966年   1篇
  1955年   1篇
排序方式: 共有221条查询结果,搜索用时 125 毫秒
81.
Let and be two n-tuples of nonnegative integers. An all-4-kings n-partite tournament T(V1,V2,…Vn) is said to have a -property if there exists an n-partite tournament T1(W1,W2,…,Wn) such that for each i∈{1,…,n}:
(1)
ViWi;
(2)
exactly ti 4-kings of Vi are not 4-kings in T1;
(3)
exactly ci 4-kings of Wi are not vertices of Vi.
We describe all pairs such that there exists an n-partite tournament having -property.  相似文献   
82.
We investigate the notion of CR transversality of a generic holomorphic map f: ℂ n → ℂ m to a smooth CR submanifold M of ℂ m . We construct a stratification of the set of non-CR transversal points in the preimage M′ = f −1 (M) by smooth submanifolds, consisting of points where the CR dimension of M′ is constant. We show the existence of a Whitney stratification for sets which are locally diffeomorphic to the product of an open set and an analytic set. Work on this paper was supported by ARRS, Republic of Slovenia.  相似文献   
83.
Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monolithic supports were prepared by radical polymerisation of the continuous phase of water in oil high internal phase emulsions. Morphology of monolithic materials was studied by scanning electron microscopy and mercury intrusion porosimetry. The ratio of phase volume and the degree of crosslinking influenced the void size and pore size distribution of resulting polymers. Void sizes between 1 and 10 microm were observed and average pore sizes around 100 nm. Polymers with 60, 75, 80 and 90% pore volume were prepared and even samples with highest pore volume showed good mechanical stability. They were modified to bear weak-anion exchange groups and tested on the separation of standard protein mixture containing myoglobin, conalbumine and trypsin inhibitor. Good separation was obtained in a very short time similar to the separation obtained by commercial methacrylate monoliths. However, higher dispersion was observed. Bovine serum albumin dynamic binding capacity for monolith with 90% porosity was close to 9 mg/ml.  相似文献   
84.
The preparation of molybdenum-modified hematite electrodes by means of chemical bath deposition and their photoelectrochemical behavior toward water oxidation are reported in this work. The addition of a molybdenum precursor to the bath solution for hematite deposition induces a remarkable change of morphology in the resulting film from (110)-oriented nanorods to polyhedral nanoparticles. Despite the resulting loss of order, by controlling the Mo/Fe molar ratio in the bath solution, a significant improvement of the water oxidation photocurrent is achieved compared to nanorod pristine hematite electrodes. Such a (photo)electrochemical enhancement is mainly explained by an effective surface state passivation in Mo-modified hematite films. FE-SEM, TEM, XRD, and XPS were employed for electrode structural and morphological characterization.
Graphical abstract ?
  相似文献   
85.
86.
We put forward a novel index of molecular complexity, ξ, taking into account the symmetry of a molecular graph and the specificity of structural components considered. The ξ index is defined as the sum of augmented valences of all mutually nonequivalent vertices in a molecular graph. The augmented valence of a vertex in a graph is the sum of its valence and valences of all neighboring vertices with the weight 1/2d depending on their distance, d, from the vertex. The ξ index is examined on the set of octane isomers and some special classes of graphs. It is also compared with a certain number of alternative complexity measures considered in the literature. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003  相似文献   
87.
88.
89.
90.
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