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   8702篇
  免费   99篇
  国内免费   10篇
电工技术   44篇
综合类   2篇
化学工业   736篇
金属工艺   61篇
机械仪表   60篇
建筑科学   50篇
矿业工程   5篇
能源动力   92篇
轻工业   219篇
水利工程   12篇
石油天然气   7篇
无线电   302篇
一般工业技术   534篇
冶金工业   6361篇
原子能技术   27篇
自动化技术   299篇
  2023年   27篇
  2022年   61篇
  2021年   76篇
  2020年   74篇
  2019年   66篇
  2018年   87篇
  2017年   64篇
  2016年   64篇
  2015年   58篇
  2014年   82篇
  2013年   177篇
  2012年   107篇
  2011年   110篇
  2010年   79篇
  2009年   87篇
  2008年   86篇
  2007年   78篇
  2006年   86篇
  2005年   61篇
  2004年   49篇
  2003年   56篇
  2002年   46篇
  2001年   22篇
  2000年   43篇
  1999年   248篇
  1998年   2108篇
  1997年   1229篇
  1996年   802篇
  1995年   436篇
  1994年   338篇
  1993年   415篇
  1992年   80篇
  1991年   73篇
  1990年   75篇
  1989年   86篇
  1988年   68篇
  1987年   68篇
  1986年   61篇
  1985年   66篇
  1984年   21篇
  1983年   27篇
  1982年   49篇
  1981年   68篇
  1980年   78篇
  1979年   23篇
  1978年   31篇
  1977年   158篇
  1976年   332篇
  1975年   24篇
  1973年   26篇
排序方式: 共有8811条查询结果,搜索用时 15 毫秒
61.
62.
63.
Cell cycle. The NIMA kinase joins forces with Cdc2   总被引:1,自引:0,他引:1  
The NIMA and Cdc2 protein kinases cooperate to regulate mitosis in Aspergillus nidulans. NIMA-related pathways have now begun to emerge in higher eukaryotes.  相似文献   
64.
65.
66.
The aim of this randomized cross-over trial was to evaluate the dose effect and systemic absorption of epinephrine nebulized at 2 and 5 mg in comparison with salbutamol (5 mg). Thirteen asthmatic patients (29 +/- 15 years, 4 men and 9 women) were randomly assigned to receive one nebulization of each of the three treatment regimens at 24 h interval. The evaluation concerned forced expiratory volume in 1 second (FEV1), heart rate, respiratory rate and arterial pressure. All measurements were done at baseline, every 15 minutes during the first hour, and hourly thereafter until return to baseline FEV1. Serum potassium was measured at baseline (T0) and sixty minutes after (T60). Plasma levels of epinephrine were measured at T0, T20, T60. Fifteen minutes after the beginning of nebulization FEV1 improved significantly over baseline in the three groups. These changes were similar in the three groups until T45, while FEV1 improvement was significantly greater in A5 and S groups than A2 group (+640 +/- 470 ml, +721 +/- 349 ml, +406 +/- 306 ml in A5, S and A2 groups respectively, p < 0.01). Bronchodilation lasted significantly longer with salbutamol than with epinephrine (p < 0.05). No side effects were recorded in spite of substantial and dose-dependent systemic absorption of epinephrine. CONCLUSION: Increasing epinephrine doses produces greater bronchodilation without additional side effects. However this bronchodilation lasts shorter than with salbutamol.  相似文献   
67.
Twenty seven Aeromonas strains (5A. hydrophila, 8A. sobria and 14A. caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A. hydrophila, 7A. sobria an 18A. caviae) isolated from children without diarrhoea were tested from haemolysin production. The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea. Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay.  相似文献   
68.
Monitoring respiratory epithelial biology may reveal individuals with incipient lung cancer. The expression of neuroendocrine (NE) markers in pulmonary epithelium is thought to be central to lung development, repair of injury and may contribute to carcinogenesis. In this study, we evaluate several candidate NE markers to determine the feasibility of prospective analysis of clinical specimens. The potential NE markers include the enzyme L-DOPA decarboxylase (DDC), the neuropeptide gastrin releasing peptide (GRP), and peptidyl-glycine alpha-amidating monooxygenase (PAM), the bifunctional enzyme responsible for the final bioactivation step of many neuropeptides. A comparison of PAM activity and DDC levels in 30 lung cancer cell lines indicated that peptide amidating activity may be an indicator of NE status. Bronchoalveolar lavage (BAL) fluid from subjects at risk of developing second primary lung cancer and from volunteers was obtained. The activity of the first PAM enzyme, peptidylglycine alpha-hydroxylating monooxygenase (PHM), ranged from not detectable to 507 pmol/h/mg protein in 57 specimens. The second PAM enzyme, peptidylamidoglycolate lyase (PAL), ranged from not detectable to 414 pmol/h/mg protein in 56 specimens. Using cluster analysis by the average linkage method, a group of enzyme values with PHM greater than 230 pmol/h/mg protein was determined. Long-term follow-up of these patients for new second primary lung cancers may help to determine the potential predictive value of PAM detected in the BAL fluid.  相似文献   
69.
L Minsk  AM Polson 《Canadian Metallurgical Quarterly》1998,19(9):859-62, 864; quiz 866
To determine if hormone supplementation reduces the risk of failure for osseointegration of dental implants in postmenopausal women, the treatment outcomes of 116 women older than age 50, treated with 450 endosseous dental implants, were analyzed in this retrospective study. The findings indicated that hormone replacement therapy may not be linked with improved outcomes of endosseous dental implant treatment in postmenopausal women. Smoking, however, appears to significantly increase the implant failure rate in the group observed in this study.  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