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   302428篇
  免费   1910篇
  国内免费   583篇
化学   140096篇
晶体学   4699篇
力学   17010篇
综合类   42篇
数学   42618篇
物理学   100456篇
  2021年   3224篇
  2020年   3533篇
  2019年   4329篇
  2018年   6333篇
  2017年   6534篇
  2016年   8108篇
  2015年   3683篇
  2014年   7063篇
  2013年   12409篇
  2012年   10391篇
  2011年   12071篇
  2010年   10170篇
  2009年   10345篇
  2008年   11667篇
  2007年   11415篇
  2006年   10157篇
  2005年   8796篇
  2004年   8547篇
  2003年   7924篇
  2002年   8257篇
  2001年   7832篇
  2000年   6174篇
  1999年   4589篇
  1998年   4316篇
  1997年   4174篇
  1996年   3783篇
  1995年   3348篇
  1994年   3410篇
  1993年   3416篇
  1992年   3430篇
  1991年   3818篇
  1990年   3818篇
  1989年   3811篇
  1988年   3578篇
  1987年   3643篇
  1986年   3336篇
  1985年   3884篇
  1984年   4104篇
  1983年   3503篇
  1982年   3719篇
  1981年   3391篇
  1980年   3154篇
  1979年   3632篇
  1978年   3696篇
  1977年   3873篇
  1976年   3945篇
  1975年   3681篇
  1974年   3543篇
  1973年   3697篇
  1972年   3184篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Kirsh  V. A.  Kirsh  A. A. 《Colloid Journal》2021,83(3):318-325
Colloid Journal - The deposition of aerosol particles in a filter composed of fibers coated with highly porous layers of radially oriented needles and the deposition of needle-coated particles onto...  相似文献   
92.
93.
94.
95.
In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm2-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.  相似文献   
96.
Russian Journal of General Chemistry - A method was developed for the synthesis of an organofluorine derivative of β-D-ribofuranoside. Biological tests revealed high insecticidal activity and...  相似文献   
97.
Journal of Analytical Chemistry - Studies on the separation of the Se and Te trace components from Co, Ni, Cu, Fe, Cr, Mo, and W macrocomponents for their determination by inductively coupled...  相似文献   
98.
Oral microbes have the capacity to spread throughout the gastrointestinal system and are strongly associated with multiple diseases. Given that tonsils are located between the oral cavity and the laryngopharynx at the gateway of the alimentary and respiratory tracts, tonsillar tissue may also be affected by microbiota from both the oral cavity (saliva) and the alimentary tract. Here, we analyzed the distribution and association of the microbial communities in the saliva and tonsils of Korean children subjected to tonsillectomy because of tonsil hyperplasia (n = 29). The microbiome profiles of saliva and tonsils were established via 16S rRNA gene sequencing. Based on the alpha diversity indices, the microbial communities of the two groups showed high similarities. According to Spearman’s ranking correlation analysis, the distribution of Treponema, the causative bacterium of periodontitis, in saliva and tonsils was found to have a significant positive correlation. Two representative microbes, Prevotella in saliva and Alloprevotella in tonsils, were negatively correlated, while Treponema 2 showed a strong positive correlation between saliva and tonsils. Taken together, strong similarities in the microbial communities of the tonsils and saliva are evident in terms of diversity and composition. The saliva microbiome is expected to significantly affect the tonsil microbiome. Furthermore, we suggest that our study creates an opportunity for tonsillar microbiome research to facilitate the development of novel microbiome-based therapeutic strategies.Subject terms: Comparative genomics, Metagenomics  相似文献   
99.
ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.  相似文献   
100.
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