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   1587篇
  免费   1篇
电工技术   10篇
化学工业   6篇
机械仪表   1篇
轻工业   2篇
水利工程   5篇
石油天然气   1篇
无线电   5篇
一般工业技术   12篇
冶金工业   1543篇
自动化技术   3篇
  2021年   3篇
  2020年   2篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   2篇
  2012年   2篇
  2011年   2篇
  2010年   2篇
  2009年   4篇
  2008年   1篇
  2007年   3篇
  2006年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   1篇
  2000年   3篇
  1999年   38篇
  1998年   471篇
  1997年   276篇
  1996年   177篇
  1995年   102篇
  1994年   72篇
  1993年   109篇
  1992年   12篇
  1991年   14篇
  1990年   12篇
  1989年   20篇
  1988年   24篇
  1987年   20篇
  1986年   28篇
  1985年   18篇
  1984年   1篇
  1983年   1篇
  1982年   8篇
  1981年   8篇
  1980年   13篇
  1978年   2篇
  1977年   39篇
  1976年   84篇
  1975年   2篇
  1972年   1篇
  1971年   1篇
  1955年   1篇
排序方式: 共有1588条查询结果,搜索用时 11 毫秒
91.
A membrane-bound protease induced by sulfur mustard in cultured normal human epidermal keratinocytes (NHEK) was purified and partially characterized. Maximum enzyme stimulation occurred at 16 hr after normal human epidermal keratinocytes were exposed to 300 microM sulfur mustard. Purification to homogeneity of the protease was accomplished by Triton X-100 solubilization, ultracentrifugation, and dialysis, followed by ion-exchange chromatography through DEAE-cellulose and finally hydrophobic column chromatography through phenyl Sepharose. Analysis of the purified enzyme by SDS-PAGE revealed a single polypeptide at the 80 kDa region. Further investigation of biochemical properties showed that a synthetic serine-specific Chromozym TRY peptide and the physiological protein laminin were good substrates for this enzyme. Moreover, this enzyme was inhibited mostly by the serine-protease inhibitors leupeptin and di-isopropyl fluorophosphate and not by the cysteine protease inhibitor E-64 or the metalloprotease inhibitor 1,10-phenanthroline (Component H, CH), indicating the serine protease nature of this enzyme. This enzyme had a pH optimum in the range of 7.0 to 8.0. Amino acid sequencing of the purified enzyme revealed that this enzyme belongs to the endopeptidase family (serine protease), and is homologous with a mammalian-type bacterial serine endopeptidase that can preferentially cleave K-X, including K-P. These results suggest that serine-protease stimulation may be one of the mechanisms of mustard-induced skin blister formation, and that some specific serine-protease inhibitors may be useful for the treatment of this sulfur mustard toxicity.  相似文献   
92.
OBJECTIVE: To assess the modern morbidity of hemoptysis and the contribution of therapeutic bronchial artery embolization to its management. METHODS: Medical record review of patients admitted for the treatment of hemoptysis from January 1991 to November 1995 and of patients who had therapeutic bronchial artery embolization from June 1986 to August 1995. Hemoptysis was labeled major or minor. RESULTS: A total of 138 patients were admitted with hemoptysis, 31 with major and 107 with minor hemoptysis. No emergency pulmonary resections were required. Mean follow-up was 13.5 months. Mortality was 29.7% (41/138) but was caused by bronchial bleeding in only 4.3% (6/138). Twenty-six patients underwent therapeutic bronchial artery embolization (mean follow-up [range], 14 months [0.3-69.0 months]). The initial success rate (no further bleeding during the initial admission) was 85% (22/26). The long-term success rate (no further bleeding during follow-up) was 58% (15/26). Only 2 patients with therapeutic bronchial artery embolization died of further hemoptysis. CONCLUSIONS: Hemoptysis signals life-threatening diseases. Therapeutic bronchial artery embolization is a good treatment adjunct to control bronchial bleeding and reduces the need for high-risk emergency lung resections.  相似文献   
93.
94.
95.
96.
To detect new genetic variation in human plasma proteins, a panel of 63 radioactive substances were screened as potential radioligands using polyacrylamide gel electrophoresis (PAGE) and autoradiography. Vitamins, hormones, drugs, amino acids, purines, pyrimidines, sugars and lipids labeled with 14C or other radionuclides were among those substances tested. A majority bound to albumin and a smaller fraction to prealbumins and lipoproteins. Several vitamins and hormones bound to specific alpha and beta globulins. (1) Electrophoretic polymorphisms of vitamin D-binding protein (group-specific component), a vitamin B12-binding protein (transcobalamin II), and thyroxine-binding alpha-globulin are described elsewhere. (2) Testosterone-binding beta-globulin (TeBG) showed an electrophoretic polymorphism in Caucasians and a possible deficiency allele. (3) Transcortin showed an electrophoretic doublet in all persons tested but no electrophoretic variation. (4) A protein binding derivative of norepinephrine or epinephrine was identified as transferrin. (5) A nonpolymorphic protein running cathodal to albumin and binding a derivative of riboflavin was tentatively identified as a fraction of albumin with mobility altered as a result of interaction with the ligand.  相似文献   
97.
98.
99.
Heterozygous rabbits of genotype a1n81f73g74/a2n82f71g75 were injected at birth with anti-al antiserum. The suppression of the VHa1 allotype resulted in a similar concommitant suppression of the constant region allotypes coded by genes of the same allogroup as a1. After 3 to 4 months the suppressed allotypes were re-expressed in measurable amounts. At 6 months in the 3 suppressed animals, the proportion of suppressed allotypes (S) to the non-suppressed ones (NS) was higher among colostrum and serum IgA (50% S, 50% NS) than among IgG for IgM. Among these two latter classes the proportion S/(S + NS) remained low (about 15% S, 85% NS) over an 18 month period in two out of three suppressed rabbits. In the third one, the proportion S/(S + NS) among IgG molecules increased to increasing concentration of S allotypes is not compensated by a decrease in concentrations of NS allotypes. The study of these phenomena could bring a better understanding of mechanisms involved in regulation of Ig synthesis and in allotype suppression.  相似文献   
100.
This study develops a decision method for evaluating the social acceptability of industrial controls on hazardous materials. Decisions are based on a "multiple criteria approach" that jointly considers measures such as risk-benefit tradeoff, minimum reducible health risk, maximum acceptable cost and implicit value of human life. Health risks are calculated by combining separate estimates of production and usage patterns, emissions to air and water, effectiveness of controls, pollutant dispersion and human susceptibility. Economic benefits consider employment, trade and consumer impacts, as well as direct costs of controls. The analysis focuses on asbestos as an example hazard. Relative values of hazard reduction alternatives are examined for asbestos manufacturing exhaust filters and for asbestos substitutes in brake linings. Preliminary calculations indicate risk reductions of these alternatives cannot justify their social costs.  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