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   1471450篇
  免费   32120篇
  国内免费   8196篇
化学   631892篇
晶体学   19951篇
力学   73681篇
综合类   108篇
数学   237334篇
物理学   354737篇
无线电   194063篇
  2021年   14700篇
  2020年   17325篇
  2019年   17475篇
  2016年   28926篇
  2015年   21562篇
  2014年   32659篇
  2013年   78433篇
  2012年   36975篇
  2011年   31325篇
  2010年   37717篇
  2009年   43145篇
  2008年   35493篇
  2007年   31799篇
  2006年   40513篇
  2005年   31534篇
  2004年   33970篇
  2003年   32611篇
  2002年   34026篇
  2001年   33180篇
  2000年   30028篇
  1999年   28254篇
  1998年   27204篇
  1997年   27150篇
  1996年   26713篇
  1995年   24547篇
  1994年   23997篇
  1993年   23346篇
  1992年   22970篇
  1991年   23187篇
  1990年   22004篇
  1989年   21621篇
  1988年   20808篇
  1987年   19628篇
  1986年   18368篇
  1985年   24914篇
  1984年   26171篇
  1983年   22134篇
  1982年   23575篇
  1981年   22771篇
  1980年   22015篇
  1979年   21881篇
  1978年   23166篇
  1977年   22735篇
  1976年   22238篇
  1975年   20896篇
  1974年   20503篇
  1973年   20971篇
  1972年   15200篇
  1968年   12940篇
  1967年   13052篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
201.
Journal of Experimental and Theoretical Physics - This article presents a survey of many nontrivial effects connected with the coupling of electric and magnetic degrees of freedom in...  相似文献   
202.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
203.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
204.
Aequationes mathematicae - For $$p\in (1,\infty )$$ , we establish several criteria of one-sided invertibility on spaces $$l^p=l^p(\mathbb {Z})$$ for discrete band-dominated operators being either...  相似文献   
205.
206.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
207.
Russian Physics Journal - The paper shows that the values of zero-point energy and vibrations of atoms in a crystal determined by the uncertainty principle, depend on the dynamic response of atoms....  相似文献   
208.
Journal of Applied and Industrial Mathematics - We study the problem of optimal location of the ambulance fleet at the base stations. The objective is to minimize the average waiting time for...  相似文献   
209.
Treating neuroinflammation-related injuries and disorders through manipulation of neuroinflammation functions is being heralded as a new therapeutic strategy. In this study, a novel pectic galactan (PG) polysaccharide based gene therapy approach is developed for targeting reactive gliosis in neuroinflammation. Galectin-3 (Gal-3) is a cell protein with a high affinity to β-galactoside sugars and is highly expressed in reactive gliosis. Since PG carries galactans, it can target reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 on the cell membrane, and therefore can be utilized as a carrier for delivering genes to these cells. The carrier is synthesized by modifying quaternary ammonium groups on the PG. The resulting quaternized PG (QPG) is found to form complexes with plasmid DNA with a mean diameter of 100 nm and have the characteristics required for targeted gene therapy. The complexes efficiently condense large amounts of plasmid per particle and successfully bind to Gal-3. The in vivo study shows that the complexes are biocompatible and safe for administration and can selectively transfect reactive glial cells of an induced cortical lesion. The results confirm that this PG-based delivery system is a promising platform for targeting Gal-3 overexpressing neuroinflammation cells for treating neuroinflammation-related injuries and neurodegenerative diseases.  相似文献   
210.
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