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   34217篇
  免费   1825篇
  国内免费   36篇
电工技术   255篇
综合类   19篇
化学工业   6779篇
金属工艺   654篇
机械仪表   725篇
建筑科学   939篇
矿业工程   77篇
能源动力   595篇
轻工业   5648篇
水利工程   322篇
石油天然气   118篇
武器工业   5篇
无线电   1285篇
一般工业技术   5891篇
冶金工业   7979篇
原子能技术   133篇
自动化技术   4654篇
  2024年   81篇
  2023年   297篇
  2022年   320篇
  2021年   792篇
  2020年   701篇
  2019年   774篇
  2018年   1415篇
  2017年   1368篇
  2016年   1421篇
  2015年   1091篇
  2014年   1291篇
  2013年   2723篇
  2012年   1989篇
  2011年   1820篇
  2010年   1509篇
  2009年   1337篇
  2008年   1275篇
  2007年   1201篇
  2006年   794篇
  2005年   675篇
  2004年   639篇
  2003年   575篇
  2002年   563篇
  2001年   419篇
  2000年   402篇
  1999年   443篇
  1998年   2371篇
  1997年   1625篇
  1996年   1031篇
  1995年   621篇
  1994年   483篇
  1993年   564篇
  1992年   213篇
  1991年   214篇
  1990年   152篇
  1989年   157篇
  1988年   162篇
  1987年   137篇
  1986年   120篇
  1985年   142篇
  1984年   129篇
  1983年   101篇
  1982年   137篇
  1981年   150篇
  1980年   162篇
  1979年   88篇
  1978年   90篇
  1977年   282篇
  1976年   634篇
  1973年   68篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
It is essential to know how the immune system acts in different neurological diseases, some of them non very well known or of unknown etiology at all. It was applied Reiber and Felgenhauer's formula in 56 patients with different diseases. IgA, IgM, IgG and albumin were quantified in sera and cerebrospinal fluid by simple immunodiffusion. It was observed more frequent IgG local synthesis and IgA in this sample.  相似文献   
93.
BACKGROUND: An important agent of food intoxication is Staphylococcus aureus, that is able to produce enterotoxins. AIM: To detect Staphylococcus aureus contamination in cafeteria food handlers of a Chilean University. SUBJECTS AND METHODS: Nose, throat, hands and nail samples from 87 food handlers were obtained for microbiological examination. RESULTS: Fifty seven subjects (65.5%) were carriers of Staphylococcus aureus. Enterotoxigenic Staphylococcus aureus was found in 36 subjects (41%). The most frequently found enterotoxin was type B (18 samples) followed by type D (12 samples). Men bad a higher frequency of contamination than women (83 and 57% of positive samples respectively). CONCLUSIONS: The frequency of Staphylococcus aureus contamination among food handlers is high and should prompt personal and environmental hygienic measures.  相似文献   
94.
The main maturation stages of Norway rat megakaryocytic series, megakaryoblasts and mature megakaryocytes, stained by silver for demonstration of argyrophil nucleolus organizer regions (AgNORs) were investigated to provide basic information on the number of nucleoli and interphasic AgNORs in these cells. The results showed that megakaryoblasts as well as mature megakaryocytes possess numerous nucleoli; their number and also the number of AgNORs is significantly higher in less mature than in more mature cells. The number of AgNORs in megakaryocytes of the Norway rat and man are virtually the same, although the numbers of nucleolar organizers per haploid chromosome set differ markedly. This fact leads to the conclusion that the number of interphasic AgNORs depends on the function and metabolic state of the cell rather than on the number of nucleolar organizers.  相似文献   
95.
96.
Composite materials of steel sheets joined by interlayers of zinc or lead- tin, show very good impact and corrosion resistance properties. Resistance spot-weld characteristics of these composite materials made of steel sheets and non-ferrous metals have been tested. Spot welds of composites with both zinc and lead- tin interlayers present good behaviour in peeling tests. Shear tests of the welds also show very high strength, probably as a consequence of simultaneous brazing because of the alloyed layer of non-ferrous material around the weld spot. This good welding behaviour enhances the possibilities of application of this composite.  相似文献   
97.
A rearranged tpr-met oncogene was identified in a MNNG-transformed human Xeroderma pigmentosum (XP) cell line (ASKMN). A 2016 bp cDNA was cloned and sequenced, disclosing an ORF with a coding capacity for a 523 aa protein. The sequence of this tpr-met cDNA was very similar to that previously reported in another human MNNG-transformed cell line (MNNG-HOS).  相似文献   
98.
99.
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