全文获取类型
收费全文 | 799篇 |
免费 | 2篇 |
专业分类
化学工业 | 5篇 |
轻工业 | 4篇 |
无线电 | 4篇 |
一般工业技术 | 4篇 |
冶金工业 | 780篇 |
自动化技术 | 4篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 25篇 |
1998年 | 224篇 |
1997年 | 121篇 |
1996年 | 75篇 |
1995年 | 42篇 |
1994年 | 36篇 |
1993年 | 39篇 |
1992年 | 9篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1978年 | 4篇 |
1977年 | 21篇 |
1976年 | 49篇 |
1975年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有801条查询结果,搜索用时 8 毫秒
131.
132.
133.
In Denmark the number of cataract extractions has increased 350% from 1980 to 1991. During the same period the elderly population at risk has only increased 17%, and thus cannot account for the large increase in the number of extractions. In order to investigate whether more comprehensive clinical indications could be a possible explanation, we compared pre-operative visual acuity and visual impairment in two consecutive samples of Danish cataract surgery patients obtained in 1980 (n = 73) and in 1992 (n = 290). Criteria for inclusion were similar and both samples were representative for the whole country. During the period mean pre-operative visual acuity increased from 0.04 to 0.16 in the eye enlisted for surgery (p < 0.00001). Visual functional impairment could be compared by using the same questionnaire for patient interview in 1992 as was used in 1980. In 1992 the degree of impairment was significantly less for reading, outdoor orientation and self care activities. A change in surgical threshold or clinical indications for surgery appears to be a major contributing factor to the large increase in surgical rates, even though a trend to perform second eye cataract surgery more often might also be of some importance. 相似文献
134.
TF Greten B Sinha C Haslberger A Eigler S Endres 《Canadian Metallurgical Quarterly》1996,299(1-3):229-233
Suppression of tumor necrosis factor-alpha (TNF) synthesis is one major target in pharmacological immunomodulation. We now showed the synergistic suppressive effect of the specific type IV phosphodiesterase inhibitor, rolipram, and of the stable prostacyclin analogue, cicaprost, on TNF synthesis. This effect was seen with lipopolysaccharide and Staphylococcus epidermidis as stimuli in human peripheral blood mononuclear cells and in whole blood. Lipopolysaccharide-induced TNF synthesis by mononuclear cells decreased from 3.4 ng/ml to 1.5 ng/ml in the presence of 100 nM rolipram and to 0.7 ng/ml in the presence of 10 nM cicaprost. The combination of both agents suppressed TNF synthesis more than 10-fold, to 0.3 ng/ml. Synergistic suppression was also demonstrated for TNF mRNA. 相似文献
135.
136.
137.
138.
139.
140.
H Kastrissios JR Suárez D Katzenstein P Girard LB Sheiner TF Blaschke 《Canadian Metallurgical Quarterly》1998,12(17):2295-2303
OBJECTIVE: To characterize drug-taking behavior using continuous electronic monitoring in an AIDS clinical trial. SETTING: This was a substudy of AIDS Clinical Trials Group (ACTG) protocol 175, a phase II/III study of dideoxynucleoside monotherapy versus combination therapy in asymptomatic HIV-positive subjects. Participants were required to comply with regimens containing zidovudine, zalcitabine and didanosine, or matching placebos; the total daily pill count was 16. DESIGN: For participants at two ACTG 175 sites, electronic devices were used to monitor drug-taking behavior of all study medications over a period of approximately 90 days. MEASUREMENTS: Four indices of drug-taking behavior were calculated and their distributions and relationship to the prescribed regimen were examined. RESULTS: Data from 41 subjects were analyzed. Of the prescribed doses of zidovudine, zalcitabine and didanosine, 88, 84 and 82%, respectively, were taken. Of these, 55, 66 and 79%, respectively, were taken at the prescribed dosing frequency. The median percentage of days on which participants failed to take any of the doses was 2-5%. There was a trend towards lower adherence in the combination therapy arms compared with those assigned to receive monotherapy. In this analysis, older patients demonstrated better adherence, although patient characteristics, in general, were poorly predictive of adherence. CONCLUSION: Drug-taking behavior for all three active study medications differed from that prescribed. One result of this erratic adherence was that study participants sustained little antiretroviral effect during more than 25% of the monitoring period. 相似文献