全文获取类型
收费全文 | 3471篇 |
免费 | 369篇 |
国内免费 | 1篇 |
出版年
2021年 | 52篇 |
2020年 | 30篇 |
2019年 | 42篇 |
2018年 | 63篇 |
2017年 | 32篇 |
2016年 | 85篇 |
2015年 | 135篇 |
2014年 | 133篇 |
2013年 | 148篇 |
2012年 | 259篇 |
2011年 | 190篇 |
2010年 | 141篇 |
2009年 | 142篇 |
2008年 | 194篇 |
2007年 | 174篇 |
2006年 | 166篇 |
2005年 | 164篇 |
2004年 | 157篇 |
2003年 | 160篇 |
2002年 | 140篇 |
2001年 | 58篇 |
2000年 | 49篇 |
1999年 | 69篇 |
1998年 | 43篇 |
1997年 | 36篇 |
1996年 | 25篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 62篇 |
1991年 | 49篇 |
1990年 | 48篇 |
1989年 | 43篇 |
1988年 | 42篇 |
1987年 | 56篇 |
1986年 | 32篇 |
1985年 | 34篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 30篇 |
1980年 | 19篇 |
1979年 | 43篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1975年 | 21篇 |
1972年 | 21篇 |
1971年 | 18篇 |
1970年 | 20篇 |
1968年 | 21篇 |
排序方式: 共有3841条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
6.
Brain and body weights, contents of DNA and protein and activities of 1,6-diphosphofructoaldolase (aldolase, EC 4.1.2.13), creatine phosphokinase (CPK, EC 2.7.3.2), and isocitric dehydrogenase (ICD, EC 1.1.1.42) in brain (minus cerebellum and brain stem) were studied in control and food-deprived rats at 7, 14 and 21 days of postnatal age. Activities of all three enzymes per brain were less in the food-deprived animals. In both groups of rats the ratios of aldolase/DNA and CPK/DNA increased with maturation, indicating that increasing activity per brain during maturation was the result of both increased activity per cell and increased numbers of cells. The ratio of ICD/DNA decreased with maturation but was essentially the same in both the food-deprived and control groups. Increase of ICD activity per brain with maturation was attributable to increased numbers of cells. Food deprivation in immature animals resulted in lowered activities per brain for aldolase, CPK and ICD because of diminished cell multiplication. 相似文献
7.
8.
Nina Fudge Charles D A Wolfe Christopher McKevitt 《BMJ (Clinical research ed.)》2008,336(7639):313-317
Objectives To understand how the policy of user involvement is interpreted in health service organisations and to identify factors that influence how user involvement is put into practice.Design Ethnographic study using participant observation, interviews, and collection of documentary evidence.Setting A multiagency modernisation programme to improve stroke services in two London boroughs.Participants Service users, National Health Service managers, and clinicians.Results User involvement in the programme was initiated and led by professionals. Professionals determined the areas of service improvement service users could participate in. A wide range of activities were considered “user involvement,” from patient satisfaction surveys to service users delivering peer support. Involvement tended to be most active in the least technical areas and areas with least input from clinicians. Factors that might explain this included organisational structure, the vagueness of the concept of user involvement, the value attributed to service users’ experiential knowledge, and variations in professional and service user understandings of and commitment to involvement. The gains of involvement were harder to identify in terms of impact on services. More evident were the personal gains for those involved: satisfaction of feeling listened to by professionals, social opportunities of meeting others in a similar situation, and increased knowledge about stroke and services available.Conclusions User involvement may not automatically lead to improved service quality. Healthcare professionals and service users understand and practise user involvement in different ways according to individual ideologies, circumstances, and needs. Given the resource implications of undertaking user involvement in service development there is a need for critical debate on the purpose of such involvement as well as better evidence of the benefits claimed for it. 相似文献
9.
A cohort of 169 births to women who were exposed throughout pregnancy to chloroquine 300 mg base once a week for chemosuppression of malaria was studied. The birth defects in this cohort were compared with those in a control group of 454 births to women who were not exposed to chloroquine, most of whom lived in non-malarious areas. The proportion of birth defects in the exposed group was not significantly different from that in the control group. This observation must be considered within the limitations of the study, which could detect only a strong teratogenic effect. It could not exclude risks lower than a 5.7-fold increase in the incidence of birth defects when chloroquine was used. Women using chloroquine during pregnancy for chemosuppression of malaria can be reassured that it is not a strong teratogen, but if it is to be used the risk of developing malaria should be balanced against the lack of data to determine whether it carries a low teratogenic risk. 相似文献
10.
Carole L. Harker Philip M. Mullineaux John A. Bryant Andrew J. Maule 《Plant molecular biology》1987,8(3):275-287
Specific antisera were prepared to the inclusion body protein (gene VI product) and the gene I product of cauliflower mosaic virus (CaMV). Translational fusions between the lacZ gene and gene VI or gene I were constructed by cloning the relevant DNA fragments into the expression vectors pUR290, pUR291 or pUR292. Large amounts of fusion protein were synthesized when the inserted DNA fragment was in frame with the lacZ gene of the expression vector. These fusion proteins were used to raise specific antisera to gene VI and gene I proteins of CaMV. Antiserum to the gene VI product detected a range of proteins in crude extracts and in a subcellular fraction enriched for virus inclusion bodies. This range of proteins was further shown to be related to gene VI by Staphylococcus aureus V8 partial proteolysis. Antiserum to the gene I product detected viral specific proteins of 46, 42 and 38 K in preparations of CaMV replication complexes from infected plants but not in any other subcellular fraction. 相似文献