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   143111篇
  免费   2765篇
  国内免费   481篇
化学   64980篇
晶体学   1153篇
力学   7868篇
综合类   1篇
数学   43393篇
物理学   28962篇
  2023年   458篇
  2022年   433篇
  2021年   749篇
  2020年   1037篇
  2019年   1031篇
  2018年   11168篇
  2017年   10976篇
  2016年   8143篇
  2015年   2820篇
  2014年   2402篇
  2013年   4622篇
  2012年   7670篇
  2011年   14104篇
  2010年   7976篇
  2009年   7975篇
  2008年   9747篇
  2007年   11630篇
  2006年   3128篇
  2005年   4062篇
  2004年   3960篇
  2003年   4001篇
  2002年   2858篇
  2001年   1562篇
  2000年   1589篇
  1999年   1159篇
  1998年   1011篇
  1997年   868篇
  1996年   1086篇
  1995年   827篇
  1994年   826篇
  1993年   798篇
  1992年   778篇
  1991年   675篇
  1990年   720篇
  1989年   637篇
  1988年   624篇
  1987年   547篇
  1986年   537篇
  1985年   715篇
  1984年   686篇
  1983年   530篇
  1982年   580篇
  1981年   592篇
  1980年   504篇
  1979年   515篇
  1978年   518篇
  1977年   437篇
  1976年   461篇
  1975年   442篇
  1974年   419篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
26.
27.
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   
28.
The development of novel, tumor-selective and boron-rich compounds as potential agents for use in boron neutron capture therapy (BNCT) represents a very important field in cancer treatment by radiation therapy. Here, we report the design and synthesis of two promising compounds that combine meta-carborane, a water-soluble monosaccharide and a linking unit, namely glycine or ethylenediamine, for facile coupling with various tumor-selective biomolecules bearing a free amino or carboxylic acid group. In this work, coupling experiments with two selected biomolecules, a coumarin derivative and folic acid, were included. The task of every component in this approach was carefully chosen: the carborane moiety supplies ten boron atoms, which is a tenfold increase in boron content compared to the l-boronophenylalanine (l-BPA) presently used in BNCT; the sugar moiety compensates for the hydrophobic character of the carborane; the linking unit, depending on the chosen biomolecule, acts as the connection between the tumor-selective component and the boron-rich moiety; and the respective tumor-selective biomolecule provides the necessary selectivity. This approach makes it possible to develop a modular and feasible strategy for the synthesis of readily obtainable boron-rich agents with optimized properties for potential applications in BNCT.  相似文献   
29.
30.
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   
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