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   3249篇
  免费   0篇
电工技术   2篇
化学工业   20篇
金属工艺   4篇
机械仪表   2篇
建筑科学   2篇
矿业工程   2篇
能源动力   2篇
轻工业   6篇
石油天然气   3篇
无线电   1篇
一般工业技术   8篇
冶金工业   3184篇
原子能技术   5篇
自动化技术   8篇
  2020年   2篇
  2018年   2篇
  2016年   1篇
  2015年   1篇
  2013年   2篇
  2012年   2篇
  2011年   4篇
  2010年   3篇
  2008年   1篇
  2006年   4篇
  2005年   4篇
  2004年   4篇
  2003年   4篇
  2002年   2篇
  2001年   1篇
  1999年   70篇
  1998年   924篇
  1997年   541篇
  1996年   391篇
  1995年   235篇
  1994年   164篇
  1993年   183篇
  1992年   20篇
  1991年   33篇
  1990年   29篇
  1989年   30篇
  1988年   25篇
  1987年   19篇
  1986年   18篇
  1985年   20篇
  1984年   1篇
  1983年   5篇
  1982年   19篇
  1981年   25篇
  1980年   34篇
  1979年   5篇
  1978年   12篇
  1977年   131篇
  1976年   258篇
  1975年   11篇
  1974年   2篇
  1973年   2篇
  1970年   1篇
  1965年   2篇
  1964年   1篇
  1954年   1篇
排序方式: 共有3249条查询结果,搜索用时 0 毫秒
991.
992.
993.
Vascular catheters coated with antiinfective compounds were evaluated as to their ability to prevent Staphylococcus aureus catheter infection in a rabbit model. Zones of inhibition of agar surface-plated S. aureus demonstrated the following hierarchy: dicloxacillin and clindamycin were each better than fusidic acid or chlorhexidine, which were better than ciprofloxacin, cefotaxime, or cefuroxime. In vivo half-lives of inhibitory activity for clindamycin and dicloxacillin were 5.6 and 17.7 h, respectively, with apparent first-order kinetics. Chlorhexidine disappeared in vivo with apparent two-compartment kinetics: first-compartment t1/2, 16.8 h; second-compartment t1/2, 115.6 h. In a rabbit model, dicloxacillin, clindamycin, fusidic acid, and chlorhexidine decreased the risk of infection compared with uncoated control catheters (P < .05). For dicloxacillin, clindamycin, and chlorhexidine, this was true even if the S. aureus inoculation was delayed 48 or 96 h after catheter implantation. These data suggest that vascular catheters with antiinfective coatings should be investigated further in hospitalized patients.  相似文献   
994.
995.
996.
997.
AIMS: To determine levels of injecting drug use and sexual risk behaviours in injecting drug users during and immediately following imprisonment in The Netherlands. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional survey of drug injectors attending methadone clinics, a sexually transmitted disease clinic and a central research site in Amsterdam. The mean age of the 188 participants was 35 years, 78% were male and 34% had HIV antibodies. MEASUREMENTS: Self-reported drug use and sexual behaviours during the last period of imprisonment in Dutch prisons within the previous 3 years and injecting drug use in the week following release from prison. FINDINGS: A period of imprisonment in the preceding 3 years was reported by 188 (41%) of 463 interviewed drug injectors. The mean duration of last imprisonment was 3.6 months. Any use of cannabis, heroin or cocaine during imprisonment was reported by 55%, 37% and 20%, respectively. Five injectors (3%) admitted to having injected in prison, but no sharing of needles and syringes was reported. Vaginal or anal sex was reported by two (1%) of the men and none of the women. Relapse to drug injecting during the week following release from prison was reported by 78/186 (42%) participants, in most cases (34%) at the very first day of release. Drug use behaviours during imprisonment were similar for those who were designated current injectors at the time of imprisonment and those who were not, but injecting in the first week following release from prison was far higher among 'current' injectors (63%) than among those who were not (11%). CONCLUSIONS: Contrary to findings from other countries, low levels of HIV risk behaviours occur among imprisoned drug injectors in The Netherlands. Intra-prison HIV preventive measures should be considered taking into account the nationally, regionally or locally varying conditions within the existing prisons.  相似文献   
998.
A seroprevalence survey was conducted using ELISA and Western blot (WB) assays for antibody to three Cryptosporidium antigens on 380 blood donors in Jackson County, Oregon. The purpose was to determine if either assay could detect serological evidence of an outbreak which occurred in Talent, Oregon 6 months earlier. The ELISA, which tested for combined IgG, IgA and IgM, and the WB, which tested separately for IgG and IgA, detected an almost twofold increase in serological response for persons who consumed Talent drinking water during the previous 11 months. The increases, however, were statistically significant (P < 0.05) only for the WB. The identification of serological evidence of infection, using sera collected 6 months after the end of the outbreak in a population not selected because of cryptosporidiosis-like illness, suggests that assays of Cryptosporidium-specific IgG and IgA may assist in estimating the magnitude of asymptomatic infections in the population.  相似文献   
999.
1000.
PURPOSE: To evaluate the efficacy of dynamic computed tomography (CT) for differentiating benign from malignant solitary pulmonary nodules (SPNs). MATERIALS AND METHODS: Sixty-five patients with noncalcified SPNs (diameter, < or = 30 mm; 42 malignant, 16 benign, seven inflammatory) underwent single-location dynamic contrast material-enhanced (100 mL, 4 mL/sec) serial CT. Peak height of time-attenuation curves and ratio of peak height of the SPN to that of the aorta were measured. Precontrast attenuation and enhancement pattern were recorded. Perfusion was calculated from the maximum gradient of the time-attenuation curve and the peak height of the aorta. RESULTS: Peak heights of malignant (41.9 HU +/- 2.8) and inflammatory (43.6 HU +/- 7.7) SPNs were significantly higher than that (13.4 HU +/- 2.2) of benign SPNs (P < .001; P < .01). SPN-to-aorta ratios in malignant and inflammatory SPNs were significantly higher than that in benign SPNs (P < .001, P < .05). No statistically significant differences in the peak height and SPN-to-aorta ratio were found between malignant and inflammatory SPNs. Precontrast attenuation of inflammatory SPNs was lower than that of malignant SPNs (P < .05). Perfusion values in malignant and inflammatory SPNs were significantly higher than that of the benign SPNs (P < .01). CONCLUSION: Dynamic CT provides quantitative information about blood flow patterns of SPNs and is an applicable diagnostic method for differentiating SPNs.  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