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   686篇
  免费   1篇
  国内免费   1篇
电工技术   1篇
化学工业   15篇
建筑科学   1篇
矿业工程   22篇
能源动力   2篇
轻工业   19篇
水利工程   2篇
无线电   3篇
一般工业技术   14篇
冶金工业   589篇
原子能技术   9篇
自动化技术   11篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   2篇
  2019年   1篇
  2017年   4篇
  2016年   1篇
  2014年   4篇
  2013年   27篇
  2012年   7篇
  2011年   5篇
  2010年   4篇
  2009年   5篇
  2008年   2篇
  2007年   7篇
  2006年   3篇
  2004年   3篇
  2003年   2篇
  2002年   2篇
  2000年   1篇
  1999年   8篇
  1998年   174篇
  1997年   95篇
  1996年   63篇
  1995年   41篇
  1994年   27篇
  1993年   26篇
  1992年   8篇
  1991年   3篇
  1990年   3篇
  1989年   4篇
  1988年   8篇
  1987年   1篇
  1986年   3篇
  1985年   3篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   13篇
  1978年   3篇
  1977年   28篇
  1976年   72篇
  1975年   2篇
  1970年   2篇
  1963年   1篇
  1955年   1篇
排序方式: 共有688条查询结果,搜索用时 15 毫秒
61.
The response to antigen is an important factor in the development of airway inflammation. Segmental bronchoprovocation (SBP) with antigen and subsequent bronchoalveolar lavage (BAL) have provided valuable insight into the mechanisms of allergic inflammation. To determine the features of allergic airway response in asthma, 19 subjects with mild asthma underwent antigen SBP in a dose-dependent manner. The amount of antigen used in SBP was 0 (saline), and 1, 5, or 20% of the antigen dose required to drop the FEV1 by 20% (APD20). BAL was done at 5 min and 48 h after SBP. BAL histamine levels increased modestly 5 min after antigen SBP. At 48 h, there was a marked increase in eosinophils and IL-5 concentration even in airway segments where the release of histamine was small. Moreover, eosinophils correlated with IL-5 levels at 48 h (r = 0.63; p < 0.001), but not with BAL histamine concentrations at 5 min. GM-CSF levels did not increase after antigen SBP and did not correlate with eosinophils. These observations indicate that asthmatic subjects can develop a dose-dependent response to antigen SBP that is characterized by a modest increase in histamine immediately after antigen exposure, and marked eosinophilia, which appears proportionately greater than the histamine response and relatively greater than what is seen in allergic nonasthmatic subjects. This feature might be important to the eventual development of airway inflammation in asthma.  相似文献   
62.
A correct access opening is the key to endodontics. An adequate anatomical access preparation maximizes cleaning, shaping, and obturation. The major objectives of access preparation are straight line access to the apical area, conservation of tooth structure, and unroofing of the pulp chamber. The safe-ended diamond bur technique provides an efficient and rapid means to obtain the objective of access preparation in posterior teeth.  相似文献   
63.
BACKGROUND AND OBJECTIVE: To evaluate the adjunctive use of mitomycin-C (MMC) during trabeculotomy and trabeculectomy for eyes with high-risk congenital glaucoma. PATIENTS AND METHODS: A prospective, randomized, double-blind study was performed to compare the effect of a single, 4-minute intraoperative exposure to 0.2 mg/ml (group 1) or 0.4 mg/ml (group 2) of MMC on trabeculotomy with trabeculectomy in 16 high-risk cases (30 eyes) of congenital glaucoma. RESULTS: The preoperative and final postoperative intraocular pressures (IOPs) of the two groups did not differ significantly. At the final follow-up, IOP control (< 21 mm Hg) without medications was achieved in 60% of the eyes in group 1 and in 86.67% of the eyes in group 2 (P = 21). With medication, IOP control was achieved in 86.7% of the eyes of each group. In both groups, the rate of surgical failure was 13.3%. Avascular, thin, sharply demarcated blebs were noted in 33.3% of the eyes from group 1 and in 66.67% of those from group 2 (P = .14). Intraoperative and postoperative hyphema and postoperative hypotony were the complications encountered in both groups, whereas serous choroidal detachment and wound leakage were seen only in group 2. CONCLUSIONS: Intraoperative MMC applied at a concentration of 0.2 mg/ml controlled postoperative IOP as effectively as a 0.4-mg/ml concentration in high-risk cases of congenital glaucoma, but with a lower incidence of complications and thin-walled blebs.  相似文献   
64.
An extensively trypsin-digested Na+/K+-ATPase, which retains the ability to bind Na+, K+, and ouabain, consists of four fragments of the alpha-subunit that contain all 10 transmembrane alpha domains, and the beta-subunit, a fraction of which is cleaved at Arg142-Gly143. In previous studies, we solubilized this preparation with a detergent and mapped the relative positions of several transmembrane helices of the subunits by chemical cross-linking. To determine if these detected helix-helix proximities were representative of those existing in the bilayer prior to solubilization, we have now done similar studies on the membrane-bound preparation of the same digested enzyme. After oxidative sulfhydryl cross-linking catalyzed by Cu2+-phenanthroline, two prominent products were identified by their mobilities and the analyses of their N termini. One was a dimer of a 11-kDa alpha-fragment containing the H1-H2 helices and a 22-kDa alpha-fragment containing the H7-H10 helices. This dimer seemed to be the same as that obtained in the solubilized preparation. The other product was a trimer of the above two alpha-fragments and that fraction of beta whose extracellular domain was cleaved at Arg142-Gly143. This product was different from a similar one of the solubilized preparation in that the latter contained the predominant fraction of beta without the extracellular cleavage. The cross-linking reactions of the membrane preparation, but not those of the solubilized one, were hindered specifically by Na+, K+, and ouabain. These findings indicate that (a) the H1-H2 transmembrane helices of alpha are adjacent to some of its H7-H10 helices both in solubilized and membrane-bound states, (b) the alignment of the residues of the single transmembrane helix of beta with the interacting H1-H2 and H7-H10 helices of alpha is altered by detergent solubilization and by structural changes in the extracellular domain of beta, and (c) the three-dimensional packing of the interacting transmembrane helices of alpha and beta are regulated by the specific ligands of the enzyme.  相似文献   
65.
The zeta protein kinase C isoform (PKC-zeta) was purified from the testis of the grey mullet Mugil cephalus and has relative masses (M(r)) of 65,000 and 63,000. The subunits of PKC-zeta from spermatozoa degenerated to M(r) 58,000 and 53,000 after continuous freezing and thawing. Proteins of M(r) 48,000 on the oolemma of the grey mullet Mugil cephalus were found to be the reaction proteins of the PKC-zeta from spermatozoa.  相似文献   
66.
67.
68.
69.
To specify shape of the vertebra in relation to age and sex, the authors studied roentgenomorphometric evidence upon examination of the thoracic and lumbar spine in 600 patients over 50. Vertebral deformities were found in 45.1 and 44.5% of the examined males and females, respectively. Changes corresponding to vertebral body fracture were recorded in 12.3% of the males and 15.3% of the females. Age-related trends in the frequency of various defects have been analyzed. The frequency differed in males and females.  相似文献   
70.
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