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   477213篇
  免费   8014篇
  国内免费   2267篇
化学   259242篇
晶体学   6730篇
力学   19798篇
综合类   124篇
数学   58760篇
物理学   142840篇
  2021年   4372篇
  2020年   5024篇
  2019年   5320篇
  2018年   6848篇
  2017年   6665篇
  2016年   10545篇
  2015年   7007篇
  2014年   10074篇
  2013年   23148篇
  2012年   18527篇
  2011年   21992篇
  2010年   15343篇
  2009年   14951篇
  2008年   19920篇
  2007年   19567篇
  2006年   18039篇
  2005年   16315篇
  2004年   15008篇
  2003年   13182篇
  2002年   12873篇
  2001年   14224篇
  2000年   10820篇
  1999年   8539篇
  1998年   7045篇
  1997年   6738篇
  1996年   6610篇
  1995年   5872篇
  1994年   5868篇
  1993年   5632篇
  1992年   6274篇
  1991年   6276篇
  1990年   6013篇
  1989年   5797篇
  1988年   5783篇
  1987年   5635篇
  1986年   5354篇
  1985年   6914篇
  1984年   7010篇
  1983年   5557篇
  1982年   5645篇
  1981年   5635篇
  1980年   5175篇
  1979年   5570篇
  1978年   5695篇
  1977年   5584篇
  1976年   5543篇
  1975年   5113篇
  1974年   5070篇
  1973年   5087篇
  1972年   3575篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
We consider conformal gravity as a gauge natural theory. We study its conservation laws and superpotentials. We also consider the Mannheim and Kazanas spherically symmetric vacuum solution and discuss conserved quantities associated to conformal and diffeomorphism symmetries.  相似文献   
102.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented.  相似文献   
103.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  相似文献   
104.
The synthesis of vinyl alcohol copolymers is limited due to the poor radical reactivity of vinyl acetate (VAc), the traditional precursor to polyvinyl alcohol (PVA). Main group monomers such as BN 2-vinylnaphthalene (BN2VN) have attracted attention as alternatives to VAc to form side chain hydroxyls via oxidation, but outstanding questions of molecular weight control remain. Herein we report systematic investigation of solvent, temperature, and initiator concentration as factors influencing BN2VN degree of polymerization. We find increased chain transfer to toluene, hypothesized to arise from differences in radical stabilization and reactivity by aromatic and BN aromatic rings. As a result of these combined efforts, high molecular weight (Mw ~ 105 g mol−1) BN2VN homopolymers and BN2VN-styrene copolymers were obtained.  相似文献   
105.
Journal of Computer-Aided Molecular Design - Accurate predictions of acid dissociation constants are essential to rational molecular design in the pharmaceutical industry and elsewhere. There has...  相似文献   
106.
Russian Journal of Organic Chemistry - Herein, we report the sulfonamide-functionalized covalent organic framework (COF-SO3H), prepared by condensation of melamine and terephthalaldehyde and...  相似文献   
107.
108.
The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole‐containing 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) dendrons are reported. The liquid‐crystal behaviour was investigated by means of differential scanning calorimetry, polarised‐light optical microscopy and X‐ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role.  相似文献   
109.
110.
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