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   1008篇
  免费   0篇
化学工业   2篇
轻工业   2篇
一般工业技术   2篇
冶金工业   1001篇
自动化技术   1篇
  2014年   1篇
  2003年   4篇
  2000年   2篇
  1999年   31篇
  1998年   290篇
  1997年   170篇
  1996年   107篇
  1995年   65篇
  1994年   58篇
  1993年   75篇
  1992年   9篇
  1991年   8篇
  1990年   10篇
  1989年   9篇
  1988年   8篇
  1987年   7篇
  1986年   14篇
  1985年   8篇
  1983年   3篇
  1982年   6篇
  1981年   6篇
  1980年   7篇
  1979年   1篇
  1978年   2篇
  1977年   32篇
  1976年   68篇
  1975年   5篇
  1970年   1篇
  1955年   1篇
排序方式: 共有1008条查询结果,搜索用时 0 毫秒
991.
OBJECTIVES: This study examines shifts in sexual experience and condom use among US teenaged males. METHODS: Results from the 1988 and 1995 National Surveys of Adolescent Males were compared. RESULTS: The proportion of never-married 15- to 19-year-old males who had had sex with a female declined from 60% to 55% (P = .06). The share of those sexually active using a condom at last intercourse rose from 57% to 67% (P < .01). Overall, the proportion of males who had sex without condoms last year declined from 37% to 27% (P < .001). CONCLUSIONS: Although protective behaviors among teenagers have increased, significant proportions of teenagers--especially Black and Hispanic males--remain unprotected.  相似文献   
992.
993.
A standardized elderberry extract, Sambucol (SAM), reduced hemagglutination and inhibited replication of human influenza viruses type A/Shangdong 9/93 (H3N2), A/Beijing 32/92 (H3N2), A/Texas 36/91 (H1N1), A/Singapore 6/86 (H1N1), type B/Panama 45/90, B/Yamagata 16/88, B/Ann Arbor 1/86, and of animal strains from Northern European swine and turkeys, A/Sw/Ger 2/81, A/Tur/Ger 3/91, and A/Sw/Ger 8533/91 in Madin-Darby canine kidney cells. A placebo-controlled, double blind study was carried out on a group of individuals living in an agricultural community (kibbutz) during an outbreak of influenza B/Panama in 1993. Fever, feeling of improvement, and complete cure were recorded during 6 days. Sera obtained in the acute and convalescent phases were tested for the presence of antibodies to influenza A, B, respiratory syncytial, and adenoviruses. Convalescent phase serologies showed higher mean and mean geometric hemagglutination inhibition (HI) titers to influenza B in the group treated with SAM than in the control group. A significant improvement of the symptoms, including fever, was seen in 93.3% of the cases in the SAM-treated group within 2 days, whereas in the control group 91.7% of the patients showed an improvement within 6 days (p < 0.001). A complete cure was achieved within 2 to 3 days in nearly 90% of the SAM-treated group and within at least 6 days in the placebo group (p < 0.001). No satisfactory medication to cure influenza type A and B is available. Considering the efficacy of the extract in vitro on all strains of influenza virus tested, the clinical results, its low cost, and absence of side-effects, this preparation could offer a possibility for safe treatment for influenza A and B.  相似文献   
994.
One hundred patients sustained gunshot wounds involving bone but not joint with a low-velocity bullet. Soft-tissue involvement was less than 1 cm at its greatest diameter. All patients were free from artery or nerve damage. No formal fixation of fracture was required. The results of the study suggest that patients need not be hospitalized longer than 2 days after an extra-articular, low-velocity gunshot wound that violates the cortex. In addition, through the use of long half-life antibiotics, such as ceftriaxone, the length of hospitalization may further be reduced to a day, while the potential for morbidity from infection is not increased.  相似文献   
995.
996.
Arsenic trioxide absorption and excretion in industry   总被引:1,自引:0,他引:1  
1. A study of 24 smelter workers routinely exposed to arsenic trioxide was conducted to evaluate some characteristics of its absorption and excretion. A statistically significant correlation was found between airborne arsenic trioxide concentrations below 300 mug/m3 and urinary arsenic values below 500 mug/liter. These men wore personal monitors for five consecutive work days and were determined to have been exposed to average airborne arsenic concentrations of 53 mug/m3 (70 mug/m3 of arsenic trioxide) which increased their urinary arsenic values from 152 mug/liter to 200 mug/liter (an average gain on 32%). 2. The background average urinary arsenic value for adult males not exposed to arsenic trioxide in industry was determined to be 52.6 mug/liter for 204 men during preemployment examinations. 3. After removal from industrial arsenic trioxide exposure, the rate of fall in urinary arsenic values varies with the magnitude of the urinary arsenic level. An initial decrease of 9.5% per day was measured for workers having urinary arsenic values below 200 mug/liter. The initial decrease is about 21% per day for workers with urinary arsenic values over 600 mug/liter. 4. It was determined that arsenic in seafood can alter, in a dramatic fashion, the urinary arsenic values determined for smelter workers within 24 hours following consumption. It is recommended, therefore, that the absorption of arsenic trioxide due to industrial exposure is best evaluated from urine samples collected at least two days after seafood has been eaten.  相似文献   
997.
998.
999.
1000.
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