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   618篇
  免费   1篇
综合类   1篇
化学工业   10篇
建筑科学   4篇
轻工业   8篇
无线电   6篇
一般工业技术   2篇
冶金工业   570篇
原子能技术   10篇
自动化技术   8篇
  2021年   2篇
  2018年   1篇
  2014年   2篇
  2013年   5篇
  2012年   2篇
  2011年   2篇
  2009年   2篇
  2008年   1篇
  2007年   3篇
  2005年   3篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   13篇
  1998年   156篇
  1997年   110篇
  1996年   61篇
  1995年   43篇
  1994年   37篇
  1993年   35篇
  1992年   9篇
  1991年   10篇
  1990年   11篇
  1989年   8篇
  1988年   4篇
  1987年   10篇
  1986年   5篇
  1985年   6篇
  1983年   3篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1979年   1篇
  1978年   3篇
  1977年   17篇
  1976年   32篇
  1975年   1篇
  1972年   1篇
  1965年   1篇
  1955年   1篇
排序方式: 共有619条查询结果,搜索用时 15 毫秒
51.
In this prospective study, we have compared women undergoing laparoscopic cholecystectomy, laparoscopic gynaecological surgery and laparoscopic minor gynaecological procedures (diagnostic, tubal, ligation) (n = 10 in each group) to determine if lower abdominal laparoscopy results in less postoperative pulmonary dysfunction than upper abdominal laparoscopy. Pulmonary testing was performed before operation, and 3 and 6 h after operation, on the first and second days after surgery. After operation, a significant reduction in forced vital capacity, forced expiratory volume in 1 s and peak expiratory flow rate occurred after laparoscopic cholecystectomy at each time. There were no significant changes after minor gynaecologic laparoscopy, whereas laparoscopic gynaecological surgery resulted in minor pulmonary dysfunction on the day of surgery only. We conclude that postoperative pulmonary function was less impaired after gynaecological laparoscopy than after laparoscopic cholecystectomy. This study suggests that the site of surgery is an important determinant of lung dysfunction after laparoscopy.  相似文献   
52.
53.
The surface oxygen content of selected wood‐based phosphoric acid‐activated carbons was quantified using X‐ray photoelectron spectroscopy (XPS) and correlated with the residual bulk phosphate levels of the carbons and their adsorptivity in solution. The adsorption of Al3+, Cu2+, and para‐chlorophenol, respectively, from water decreased as a function of increasing surface oxygen content of the carbons. When the carbon of lowest surface oxygen content was oxidized with ozone to impart a surface oxygen content comparable to that of a carbon with a much higher phosphate level, adsorption of Al3+, Cu2+, and para‐chlorophenol from water decreased proportionally. The increase in polarity of the carbon surface was accompanied by a decrease in pH and appeared to be the dominant factor with respect to the adsorption of the target species from water. Copyright © 2005 Society of Chemical Industry  相似文献   
54.
The conserved residue Asp477 in yeast transketolase is located in the substrate channel of the enzyme and forms a hydrogen bond with the C2-hydroxyl group of the acceptor substrate. The significance of this interaction for the recognition of the preferred acceptor substrates, D-alpha-hydroxyaldehydes was investigated by site-directed mutagenesis. In the wild-type enzyme the kcat/KM values are by three to four orders of magnitude lower for 2-deoxyaldoses or substrates with L-configuration at the C2-atom. In the Asp477 Ala mutant, the kcat/KM values for D-alpha-hydroxyaldehydes are decreased by a thousandfold, while the kcat/KM values for substrates with L-configuration or 2-deoxyaldoses are similar to wild-type enzyme. These results indicate that Asp477 is involved in determining the enantioselectivity of transketolase.  相似文献   
55.
Benign mesothelioma of the pleura is a very rare tumor. The cells responsible originate from either the mesothelium or the submesothelium. This is why such tumors are described in the literature as fibroma of the pleura, mesothelial fibroma, localized fibrous mesothelioma and monophasic spindle cell tumor. Their growth, is very slow taking several years or even decades. In contrast to the more common malignant mesothelioma of the pleura, it is not related to asbestos exposure. This report deals with a 47-year-old woman patient with a giant benign mesothelioma of the pleura in the region of the right thorax, which was completely removed by thoracotomy.  相似文献   
56.
HAH1 is a 68-amino acid protein originally identified as a human homologue of Atx1p, a multi-copy suppressor of oxidative injury in sod1 delta yeast. Molecular modeling of HAH1 predicts a protein structure of two alpha-helices overlaying a four-stranded antiparallel beta-sheet with a potential metal binding site involving two conserved cysteine residues. Consistent with this model, in vitro studies with recombinant HAH1 directly demonstrated binding of Cu(I), and site-directed mutagenesis identified these cysteine residues as copper ligands. Expression of wild type and mutant HAH1 in atx1 delta yeast revealed the essential role of these cysteine residues in copper trafficking to the secretory compartment in vivo, as expression of a Cys-12/Cys-15 double mutant abrogated copper incorporation into the multicopper oxidase Fet3p. In contrast, mutation of the highly conserved lysine residues in the carboxyl terminus of HAH1 had no effect on copper trafficking to the secretory pathway but eliminated the antioxidant function of HAH1 in sod1 delta yeast. Taken together, these data support the concept of a unique copper coordination environment in HAH1 that permits this protein to function as an intracellular copper chaperone mediating distinct biological processes in eucaryotic cells.  相似文献   
57.
The division of CD4+ alpha beta T cells into Th1 and Th2 subsets has become an established and important paradigm. The respective activities of these subsets appear to have profound effects on the course of infectious and autoimmune diseases. It is believed that specific programs of differentiation induce the commitment of an uncommitted Th0 precursor cell to Th1 or Th2. A component of these programs is hypothesized to be the nature of MHC-peptide antigen presentation to the alpha beta T cell. It has heretofore remained uncertain whether a Th1/Th2 classification likewise defines, at the clonal level, gamma delta T cells. Such cells do not, as a general rule, express either CD4 or CD8 alpha beta, and they do not commonly recognize peptide-MHC. In this report, gamma delta cell clones are described that conform strikingly to the Th1/Th2 classification, both by cytokine expression and by functional activities of the clones in vitro and in vivo. Provocatively, both the gamma delta cell clones and primary gamma delta cells in vivo showed a strong association of the Th2 phenotype with CD4 expression. These results are discussed with regard to the immunoregulatory role that is increasingly emerging for gamma delta cells.  相似文献   
58.
59.
BACKGROUND: Tissue subjected to a period of ischemia undergoes morphological and functional damage that increases during the reperfusion phase. The aim of the present work was to assess the possible improvement induced by exogenous administration of nitric oxide (NO) on renal injury and inflammatory reaction in an experimental animal model of renal ischemia-reperfusion (I-R). METHODS: Ischemia was achieved by ligation of the left arteria and vein for 60 min, followed first by contralateral nephrectomy and then reestablishment of blood flow. Molsidomine, used as an NO donor, was administered by systemic injection 30 min before reperfusion. The effect of molsidomine was compared with the effect of hydralazine, a non-NO donor hypotensive agent. RESULTS: Treatment with molsidomine improved the renal dysfunction (increase in plasma creatinine and urea levels) caused by I-R. Moreover, molsidomine blunted the enhanced production of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha and interleukin [IL] 1alpha), the increase in tissular levels of superoxide anions and oxygen free radical scavengers, and the neutrophilic infiltration observed in the ischemic kidney. One hundred percent survival was achieved in the group of animals treated with the NO donor, whereas the groups of animals undergoing I-R that did not receive molsidomine showed a 40% mortality from the second day after reperfusion. CONCLUSIONS: The present work demonstrated that systemic treatment with an NO donor before reperfusion improved renal function and diminished inflammatory responses in a kidney subjected to an I-R process.  相似文献   
60.
The capabilities of current protein structure prediction methods have been assessed from the outcome of a set of blind tests. In comparative modeling, many of the numerical methods did not perform as well as expected, although the resulting structures are still of great practical use. The new methods of fold identification ('threading') were partially successful, and show considerable promise for the future. Except for secondary structure data, results from traditional ab initio methods were poor. A second blind prediction experiment is underway, and progress in all areas is expected.  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