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   490篇
  免费   12篇
  国内免费   2篇
化学   421篇
晶体学   13篇
力学   3篇
数学   10篇
物理学   57篇
  2023年   1篇
  2022年   5篇
  2021年   8篇
  2020年   10篇
  2019年   9篇
  2018年   2篇
  2017年   3篇
  2016年   11篇
  2015年   9篇
  2014年   10篇
  2013年   23篇
  2012年   30篇
  2011年   32篇
  2010年   26篇
  2009年   13篇
  2008年   37篇
  2007年   33篇
  2006年   31篇
  2005年   31篇
  2004年   28篇
  2003年   22篇
  2002年   22篇
  2001年   4篇
  2000年   6篇
  1999年   4篇
  1998年   6篇
  1997年   7篇
  1996年   6篇
  1995年   1篇
  1994年   3篇
  1993年   6篇
  1992年   7篇
  1990年   4篇
  1989年   4篇
  1988年   4篇
  1987年   1篇
  1986年   3篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   5篇
  1981年   7篇
  1980年   7篇
  1979年   5篇
  1978年   1篇
  1977年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
排序方式: 共有504条查询结果,搜索用时 15 毫秒
71.
The solid‐state chiral optical properties of a 4‐(2‐arylethynyl)‐benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4‐(2‐arylethynyl)‐benzoic acid component molecule rather than the chirality of the amine component molecule.  相似文献   
72.
A voice therapy program using pushing exercises to correct glottal incompetence is described. The program utilizes various types of instrumentation to determine whether or not a given patient is likely to benefit from the treatment. The program also provides feedback of target voices. Three cases with incomplete glottal closure and subsequent vocal dysphonia characterized by an asthenic breathy quality are used to illustrate the program. Details of the program, termination criteria, and problems and precautions learned from treating 29 patients over a 3-year period are presented.  相似文献   
73.
For a pair of vertices x and y in a graph G, we denote by dG(x,y) the distance between x and y in G. We call x a boundary vertex of y if x and y belong to the same component and dG(y,v)?dG(y,x) for each neighbor v of x in G. A boundary vertex of some vertex is simply called a boundary vertex, and the set of boundary vertices in G is called the boundary of G, and is denoted by B(G).In this paper, we investigate graphs with a small boundary. Since a pair of farthest vertices are boundary vertices, |B(G)|?2 for every connected graph G of order at least two. We characterize the graphs with boundary of order at most three. We cannot give a characterization of graphs with exactly four boundary vertices, but we prove that such graphs have minimum degree at most six. Finally, we give an upper bound to the minimum degree of a connected graph G in terms of |B(G)|.  相似文献   
74.
A flow-injection system with an enzyme reactor was proposed for the measurement of fructosyl amino acids and fructosyl peptides in protease-digested blood samples. A fructosyl-amino acid oxidase (FAOX-TE) and two fructosyl-peptide oxidases (FPOX-CE and FPOX-CET) were covalently immobilized onto an inert support. They were used as the enzyme reactor in a FIA system with a hydrogen peroxide electrode. In particular, the FPOX-CET reactor possessed high selectivity for the detection of fructosyl valine (FV) and fructosyl valyl histidine (FVH) and an excellent operational stability. The proposed FIA system with the FPOX-CET reactor responded linearly to the concentration of FV over the dynamic range of 7.8 x 10(-6) to 5.8 x 10(-4) M. The present method could be successfully applied to the assay of FV and FVH in the protease-digested blood samples.  相似文献   
75.
76.
SVL fluorescence spectra from principal bands in the S1 state of pyridine h5 and -d5 were measured. A large displacement of the normal coordinate origin of v6a and the Duschinskii rotation of v10a and v16a were established.  相似文献   
77.
Physical and chemical structure, as well as thermal behavior of solution-cast regenerated films, prepared from tussah (Antheraea pernyi) silk fibroin, were compared with those of solution-cast native films, in order to ascertain whether treatment (degumming, dissolution) used for preparation affected their properties. Regenerated fibroin films exhibited a higher thermal stability than native ones, as shown by differential scanning calorimetry, thermomechanical analysis, and dynamic mechanical behavior. Glass transition temperature and other relevant thermal transitions of the regenerated silk specimen shifted to higher temperatures compared with those of native specimen. Molecular conformation and crystalline structure did not show significant differences between the two kinds of silk films. Amino acid composition and molecular weight, however, distribution changed markedly after dissolving tussah silk fibroin fiber in concentrated LiSCN in polypeptide size was the main features for the regenerated silk fibroin. © 1994 John Wiley & Sons, Inc.  相似文献   
78.
We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 +/- 63, 20 +/- 11 and 17 +/- 8 [mean +/- SD] pg/cm2, respectively.  相似文献   
79.
80.
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