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   215959篇
  免费   3901篇
  国内免费   746篇
化学   119472篇
晶体学   2390篇
力学   8433篇
综合类   8篇
数学   26894篇
物理学   63409篇
  2021年   1580篇
  2020年   1869篇
  2019年   1829篇
  2018年   2116篇
  2017年   2070篇
  2016年   4082篇
  2015年   3353篇
  2014年   3906篇
  2013年   10682篇
  2012年   9135篇
  2011年   10695篇
  2010年   6701篇
  2009年   6605篇
  2008年   9681篇
  2007年   9477篇
  2006年   9029篇
  2005年   8578篇
  2004年   7656篇
  2003年   6506篇
  2002年   6226篇
  2001年   6857篇
  2000年   5419篇
  1999年   4089篇
  1998年   3121篇
  1997年   2999篇
  1996年   2870篇
  1995年   2613篇
  1994年   2600篇
  1993年   2408篇
  1992年   2764篇
  1991年   2647篇
  1990年   2398篇
  1989年   2313篇
  1988年   2342篇
  1987年   2237篇
  1986年   2144篇
  1985年   3161篇
  1984年   3115篇
  1983年   2497篇
  1982年   2680篇
  1981年   2578篇
  1980年   2481篇
  1979年   2433篇
  1978年   2486篇
  1977年   2441篇
  1976年   2394篇
  1975年   2333篇
  1974年   2256篇
  1973年   2349篇
  1972年   1327篇
排序方式: 共有10000条查询结果,搜索用时 921 毫秒
31.
32.
33.
Su  X. F.  Zhang  Y. L.  Maximov  A. L.  Zhang  K.  Xin  Q.  Feng  C. Q.  Bai  X. F.  Wu  W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,...  相似文献   
34.
35.
36.
37.
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   
38.
ABSTRACT

This study was to investigate the piezotolerance and diversity indices of microflora of Indian white prawn (Fenneropenaeus indicus) after high pressure (HP)-treatment. Indian white prawns subjected to HP-treatments and its effect was studied up to species level and compared with unpressurized samples. The bacterium was identified by using bacterial identification schemes, biochemical tests and API kits (bioMérieux, Marcyl’Etoile, France). Diversity analysis was performed using PRIMER (Plymouth Routines in Multivariate Research) software v 5.2.2. The significant elimination of microflora was found to be proportional with the pressure level. In the case of spore formers, mere destruction was noticed after HP-treatment. Arthrobacter spp., Listeria grayi and Corynebacterium spp. were the most piezotolerant bacteria in HP-treated samples. Diversity indices revealed a significant reduction of microflora of Indian white prawn. The apparent reduction of microflora with pressure level was clearly evident from the diversity indices; moreover a diminished piezotolerance of Gram negative spoilage bacteria was also observed.  相似文献   
39.
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   
40.
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