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   851篇
  免费   3篇
化学工业   10篇
机械仪表   3篇
能源动力   3篇
轻工业   3篇
水利工程   1篇
一般工业技术   4篇
冶金工业   827篇
自动化技术   3篇
  2021年   2篇
  2019年   1篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2011年   4篇
  2010年   3篇
  2006年   2篇
  2005年   3篇
  2004年   2篇
  2003年   4篇
  1999年   23篇
  1998年   254篇
  1997年   134篇
  1996年   114篇
  1995年   53篇
  1994年   33篇
  1993年   51篇
  1992年   10篇
  1991年   13篇
  1990年   13篇
  1989年   14篇
  1988年   6篇
  1987年   9篇
  1986年   5篇
  1985年   14篇
  1981年   5篇
  1980年   5篇
  1979年   2篇
  1978年   3篇
  1977年   20篇
  1976年   43篇
  1975年   2篇
  1954年   1篇
排序方式: 共有854条查询结果,搜索用时 39 毫秒
851.
Enterotoxin production by Staphylococcus species other than Staphylococcus aureus has been reported. Staphylococcus strains (104 in toto) representing twelve species and subspecies were examined for enterotoxins using a commercial staphylococcal enterotoxin ELISA immunoassay (TECRA, International Bioproducts). Staphylococcus intermedius (24 strains) and S. aureus (7 strains) were positive with this test. Western blots of S. aureus exoproteins demonstrated proteins of approximately 30 kD, consistent with known staphylococcal enterotoxins. The major antigen in all S. intermedius strains, a 75 kD protein, was not analogous to previously described staphylococcal enterotoxins. This protein was unique to S. intermedius. Gel filtration data indicate that the protein is a subunit of a larger protein in vivo. The 75 kD protein cross-reacts with several enterotoxin antibodies. It is unclear whether the protein is a toxin, but its homology with S. aureus enterotoxins may indicate a shared toxic region, or this protein may create false positive results in screening for enterotoxin.  相似文献   
852.
OBJECTIVES: This study sought to evaluate changes in early morbidity and mortality as well as predictors of outcome in our most recent 339 patients undergoing modified Fontan operations. BACKGROUND: The Fontan operation is the preferred definitive palliation for patients with functional single ventricles. Previously reported early mortality rates after Fontan operation have been substantial. METHODS: Records of 339 consecutive patients who had a Fontan operation at the Mayo Clinic between 1987 and 1992 (recent cohort) were reviewed. This cohort was compared with the previous 500 patients who had Fontan operations performed between 1973 and 1986 (early cohort). RESULTS: Recently, overall early mortality after Fontan has decreased significantly compared with that for the early cohort (from 16% to 9%, p = 0.002). This decline occurred despite increased anatomic complexity of patients. Short-term posthospital survival has also improved significantly in recent patients. One-year survival improved to 88% from 79%, and 5-year survival to 81% from 73% (p = 0.006). Patients with common atrioventricular valves and those who took daily preoperative diuretic medication or had either postoperative renal failure or elevated postbypass right atrial pressure were at increased risk for early mortality. Young age was not found to be a risk factor for early mortality. Early mortality for patients with heterotaxia decreased dramatically: recent 30-day mortality was 15% compared with 41% in the early heterotaxy cohort. CONCLUSIONS: Many factors may have contributed to decreased early mortality after Fontan. Improved patient selection, younger age at time of operation, refinements in surgical techniques and postoperative management may all have had important roles. Proposed technical modifications of the Fontan operation must be evaluated in light of these improved results.  相似文献   
853.
NADPH oxidase     
The antimicrobial activities of insoluble halogenated acetamidomethy1-styrene polymers (prepared by covalent bonding of iodine to polystyrene) were assessed as were the factors determining antimicrobial efficacy. The most active materials were selected from chlorinated or iodinated polymers. Antimicrobial activities were assessed for Escherichia coli (ATCC 25922; American Type Culture Collection, Rockville, MD, U.S.A.), Saccharomyces cerevisiae, and Candida albicans by determining time-course changes in microbial counts in vitro. A 2-iodoacetamidomethylstyrene polymer (No.6-I:-CH2I) was found to have the greatest antimicrobial activity against both bacteria and fungi. No.6-I is the first antimicrobial material that did not make an inhibition hollow in the conventional diffusion test or for which conjugated iodine showed antibacterial activity. This material can be introduced into styrene units on the surface of devices by chemical modification. This material was most active at 37 degrees C. For coated dishes, antimicrobial activity depended on the depth or swollen character of the reactive layer. NO.6-I requires not only a minimum width of polymer layer, but also frequent contact with microbes to have an antimicrobial effect. No.6-I is valuable as a new material because it has strong antimicrobial activity by itself but does not release active iodine. This material is expected to have various applications in implantable clinical devices.  相似文献   
854.
BACKGROUND: This study uses wrist actigrapy to assess the effects of 24-hr transdermal nicotine replacement on the sleep and daytime activity of smokers during smoking cessation. METHODS: Seventy-one subjects grouped as light (n = 23), moderate (n = 24), or heavy (n = 24) smokers were randomly assigned to placebo or 11, 22, or 44 mg/day doses of transdermal nicotine for 1 week of intensive inpatient treatment of nicotine dependence. Outpatient patch therapy continued for 7 weeks following the inpatient stay. Those initially on placebo were randomly assigned to 11 or 22 mg/day, and those initially on 44 mg/day were reduced to 22 mg/day at Week 4. RESULTS: There was a significant decrease in daytime wrist activity during patch therapy and the 1st week off patch therapy. These changes in daytime wrist activity were positively correlated with percentage of nicotine and cotinine replacement. No changes from baseline in sleep (sleep efficiency or wrist activity) were detected, nor were there differences in sleep among the four patch doses. CONCLUSIONS: Using wrist actigraphy, this study failed to show any disturbing effects of 24-hr high-dose nicotine replacement on sleep. Lower levels of nicotine replacement were associated with a decrease from baseline in daytime wrist activity.  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