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   48623篇
  免费   1244篇
  国内免费   203篇
电工技术   653篇
综合类   636篇
化学工业   5881篇
金属工艺   816篇
机械仪表   1240篇
建筑科学   934篇
矿业工程   392篇
能源动力   733篇
轻工业   2537篇
水利工程   631篇
石油天然气   55篇
武器工业   7篇
无线电   2765篇
一般工业技术   4779篇
冶金工业   21688篇
原子能技术   251篇
自动化技术   6072篇
  2024年   60篇
  2023年   262篇
  2022年   210篇
  2021年   270篇
  2020年   162篇
  2019年   185篇
  2018年   643篇
  2017年   854篇
  2016年   1250篇
  2015年   928篇
  2014年   681篇
  2013年   763篇
  2012年   2566篇
  2011年   2931篇
  2010年   1015篇
  2009年   1158篇
  2008年   965篇
  2007年   924篇
  2006年   788篇
  2005年   3551篇
  2004年   2721篇
  2003年   2182篇
  2002年   1004篇
  2001年   861篇
  2000年   404篇
  1999年   720篇
  1998年   6284篇
  1997年   3919篇
  1996年   2583篇
  1995年   1516篇
  1994年   1110篇
  1993年   1140篇
  1992年   270篇
  1991年   319篇
  1990年   321篇
  1989年   296篇
  1988年   308篇
  1987年   233篇
  1986年   208篇
  1985年   174篇
  1984年   71篇
  1983年   87篇
  1982年   134篇
  1981年   180篇
  1980年   191篇
  1979年   62篇
  1978年   98篇
  1977年   613篇
  1976年   1325篇
  1975年   100篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Hemiballism is a rare hyperkinetic disorder which is characterized by irregular vigorous rotatory movements of the limbs of one side of the body. The disabling and exhausting movements with their high risk of severe injuries require an acute drug treatment. However, there are no common guidelines for the treatment of this disorder. Therefore we reviewed the available literature to establish a concept for a rational symptomatic drug treatment. Furthermore, own observations in 6 patients with hemiballism of different origins are reported.  相似文献   
92.
93.
It was found, that To?pa Peat Preparation (TPP) administered to healthy volunteers in doses of 100-300 mg/day during 14 days evoked the stimulation of the phagocytic and bactericidal activity of the granulocytes. The dose of 600 mg/day causes only a transient and insignificant increase of phagocytic and bactericidal properties of the granulocytes.  相似文献   
94.
A total of 259 Gram-negative Porphyromonas-like rods isolated from subgingival plaque samples of 16 family-owned dogs with naturally occurring periodontitis were characterized phenotypically by biochemical reactions, metabolic end products and enzymatic activities (API-ZYMTM, RoscoTM). Four distinct groups were found. Group A isolates (63) were asaccharolytic, lipase negative, trypsin positive and produced phenylacetic acid (PAA) from peptone-yeast extract glucose broth. Unlike P. gingivalis strains they were catalase positive. Group B isolates (42) differed from those of group A by a positive lipase reaction and from those of group D by failing to ferment sugars. Group C isolates (88) were asaccharolytic and did not produce PAA. They were alpha-fucosidase, N-acetyl-beta-glucosaminidase (beta-NAG) and trypsin negative, resembling P. endodontalis, but unlike human isolates, they were catalase positive. Subgroup C.1 isolates (6) differed from those of parent group C by producing minor amounts of PAA, and subgroup C.2 isolates (12) were beta-NAG positive. Group D isolates (46) were weakly fermentative, lipase, catalase and trypsin positive, and produced PAA. They resembled the B (P.) salivosus type strain which, in our hands, fermented weakly glucose, lactose and mannose. Two isolates could not be assigned to any of the previous groups.  相似文献   
95.
The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2.  相似文献   
96.
97.
The interaction of human peripheral blood leukocytes with alpha 1-acid glycoprotein (AGP), its glycoforms as well as neoglyco-conjugates representing carbohydrate chains of AGP or its fragments was studied by flow cytometry. It was shown that the main target cells for AGP as well as for conjugates of its carbohydrate chains with polyacrylamide (PAA) are monocytes and polymorphonuclear leukocytes but not lymphocytes. The interaction of AGP with monocytes and granulocytes are mediated by its carbohydrate chains: the binding of AGP with cells was inhibited by AGP, AGP oligosaccharides as well as conjugates of oligosaccharides and its fragments with PAA. The data obtained show the existence of monocyte (and granulocyte) receptors which interact with complex type sialooligosaccharides of AGP.  相似文献   
98.
99.
Here we present a case of a patient with a massive ossification of annulus fibrosus and longitudinal ligament at the level C3-C4, C4-C5 and C5-C6, also called the Van Swaay bridge. One can observe a propulsion of the pharingeal tissue at the level of the massive Van Swaay bridge between C5 and C6 which caused pressure and dysphagia.  相似文献   
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