全文获取类型
收费全文 | 4472篇 |
免费 | 454篇 |
专业分类
4926篇 |
出版年
2021年 | 51篇 |
2019年 | 43篇 |
2018年 | 63篇 |
2017年 | 40篇 |
2016年 | 72篇 |
2015年 | 106篇 |
2014年 | 146篇 |
2013年 | 198篇 |
2012年 | 221篇 |
2011年 | 207篇 |
2010年 | 133篇 |
2009年 | 118篇 |
2008年 | 153篇 |
2007年 | 156篇 |
2006年 | 155篇 |
2005年 | 140篇 |
2004年 | 166篇 |
2003年 | 166篇 |
2002年 | 154篇 |
2001年 | 152篇 |
2000年 | 129篇 |
1999年 | 118篇 |
1998年 | 65篇 |
1997年 | 54篇 |
1996年 | 51篇 |
1994年 | 44篇 |
1993年 | 38篇 |
1992年 | 75篇 |
1991年 | 75篇 |
1990年 | 75篇 |
1989年 | 61篇 |
1988年 | 54篇 |
1987年 | 54篇 |
1986年 | 57篇 |
1985年 | 53篇 |
1984年 | 71篇 |
1983年 | 48篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1978年 | 46篇 |
1977年 | 49篇 |
1976年 | 41篇 |
1975年 | 55篇 |
1974年 | 45篇 |
1973年 | 74篇 |
1972年 | 48篇 |
1971年 | 41篇 |
1970年 | 37篇 |
排序方式: 共有4926条查询结果,搜索用时 0 毫秒
1.
2.
3.
Clinical interest in the lipoproteins stems mainly from the association between serum cholesterol concentrations and coronary heart disease. Investigations of lipoproteins should be performed in patients with premature coronary heart disease, with a strong family history of coronary heart disease, or with certain cutaneous stigmata of hyperlipoproteinaemia and when fasting serum samples are seen to be lipaemic. Family studies should be performed in appropriate cases to identify relatives at increased risk of developing coronary heart disease. Patients with conditions known to cause secondary hyperlipoproteinaemia should be investigated if they fall into one of these categories but only after treatment of the underlying condition. Non-specialist laboratories should be able to measure total cholesterol and triglyceride concentrations and high density lipoprotein cholesterol concentrations. Lipoprotein electrophoresis has a limited role in such laboratories and is not necessary as a routine procedure. Specialist laboratories should in addition be able to measure individual lipoproteins and identify apolipoprotein E phenotypes. 相似文献
4.
Patricia A. Marshall 《Medical anthropology quarterly》1998,12(2):250-252
Sickness and Healing: An Anthropological Perspective. Robert A. Hahn. New Haven, CT: Yale University Press, 1995 (cloth and paper), viii. 327 pp. 相似文献
5.
6.
7.
8.
9.
V.M. Marshall A.P. Laws Y. Gu F. Levander P. Rådström L. De Vuyst B. Degeest F. Vaningelgem H. Dunn & M. Elvin 《Letters in applied microbiology》2001,32(6):433-437
AIMS: To compare galactose-negative strains of Streptococcus thermophilus and Lactobacillus delbrueckii subspecies bulgaricus isolated from fermented milk products and known to produce exopolysaccharides (EPSs). METHODS AND RESULTS: The structures of the EPSs were determined using nuclear magnetic resonance (NMR) and their genetic relationships determined using restriction endonuclease analysis (REA) and random amplification of polymorphic DNA (RAPD). Similar groupings were apparent by REA and RAPD, and each group produced an EPS with a particular subunit structure. CONCLUSION: Although none of the strains assimilated galactose, all inserted a high proportion of galactose into their EPS when grown in skimmed milk, and fell into three distinct groups. Significance and Impact of the Study: This information should help in an understanding of genetic exchanges in lactic acid bacteria. 相似文献
10.
Many commonly used anesthetics cause hypothermia by inhibiting central and peripheral thermoregulatory mechanisms. Although it is probable that a loss of thermal homeostasis contributes directly to the high mortality frequently reported following anesthesia of laboratory rodents, this adverse effect has been investigated rarely in the past. This study compared the effects of three parenteral anesthetics (pentobarbital, ketamine-xylazine and ketamine-diazepam) and a neuroleptanalgesic (fentanyl-droperidol) on core and surface body temperature regulation in rats. Results showed a profound hypothermia with all dosages of pentobarbital, while ketamine-xylazine and ketamine-diazepam caused a dose-dependent depression in core and surface body temperature. All dosages of fentanyl-droperidol (Innovar-Vet) caused minimal depression in thermoregulation, suggesting that it is the drug which requires the least external thermal support. Results of this study also suggested that inability to compensate for heat loss, particularly from the body core, may profoundly influence anesthetic toxicity and the safety of anesthetic procedures. 相似文献