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   729篇
  免费   43篇
  国内免费   2篇
耳鼻咽喉   79篇
儿科学   21篇
妇产科学   13篇
基础医学   92篇
口腔科学   4篇
临床医学   66篇
内科学   109篇
皮肤病学   20篇
神经病学   108篇
特种医学   72篇
外科学   50篇
综合类   4篇
一般理论   1篇
预防医学   43篇
眼科学   2篇
药学   78篇
肿瘤学   12篇
  2021年   12篇
  2020年   8篇
  2019年   6篇
  2018年   10篇
  2017年   7篇
  2016年   6篇
  2015年   14篇
  2014年   13篇
  2013年   28篇
  2012年   26篇
  2011年   24篇
  2010年   20篇
  2009年   23篇
  2008年   22篇
  2007年   22篇
  2006年   25篇
  2005年   35篇
  2004年   26篇
  2003年   25篇
  2002年   22篇
  2001年   13篇
  2000年   25篇
  1999年   19篇
  1998年   20篇
  1997年   16篇
  1996年   12篇
  1995年   17篇
  1994年   14篇
  1993年   8篇
  1992年   16篇
  1991年   14篇
  1990年   15篇
  1989年   12篇
  1988年   16篇
  1987年   18篇
  1986年   15篇
  1985年   15篇
  1984年   23篇
  1983年   7篇
  1982年   11篇
  1981年   9篇
  1980年   4篇
  1979年   6篇
  1978年   7篇
  1977年   9篇
  1976年   10篇
  1975年   7篇
  1974年   10篇
  1971年   5篇
  1966年   4篇
排序方式: 共有774条查询结果,搜索用时 15 毫秒
11.
Amphiphilic AB and ABA block copolymers have been prepared from poly (ortho esters) and poly (ethylene glycol). Such block copolymers readily form micellar dispersions in water, or buffers. The CMC is in the range of 3 × 10-4–5 × 10-4 g/l which is a value low enough to assure retention of micelle integrity upon intravenous injection. The size, as determined by dynamic light scattering was in the 40–70 nm range. The micelles can be stored in lyophilized form for at lest 8 months and easily reconstituted to the original properties. The micelles are stable in PBS at pH 7.4 and 37°C for 3 days and in a citrate buffer at pH 5.5 and 37°C for 2 h. Stability in the presence of bovine serum albumin depends on the structure of the block copolymer and especially the length of the POE block.  相似文献   
12.
Adolescent cannabis use is associated with working memory impairment. The present randomized controlled trial assigned adolescents ages 14 to 21 enrolled in cannabis use treatment to receive either working memory training (experimental group) or a control training (control group) as an adjunctive treatment. Cognitive function, drug use, and other outcomes were assessed before and after training. We observed few differences in cognitive, functional, or self-reported drug use outcomes as a function of training group, although tetrahydrocannabinol (THC) urinalysis results favored the experimental group. These findings are similar to previous studies in substance users, which have shown limited transfer effects for working memory training.  相似文献   
13.
Four uremic patients on maintenance hemodialysis developed intractable heart failure and atrioventricular block. All had persistently high (over 60) calcium-phosphorus products. At autopsy, all had metastatic myocardial calcification. Their inability to take phosphate-binding agents orally is responsible for this fatal complication.  相似文献   
14.
Bowen  BJ; Morgan  EH 《Blood》1987,70(1):38-44
The mechanisms underlying the impaired utilization of transferrin-bound iron by erythroid cells in the anemia of the Belgrade laboratory rat were investigated using reticulocytes from homozygous anemic animals and transferrin labeled with 59Fe and 125I. The results were compared with those obtained using reticulocytes from phenylhydrazine-treated rats and iron-deficient rats. Each step in the iron uptake mechanism was investigated, ie, transferrin-receptor interaction, transferrin endocytosis, iron release from transferrin, and transferrin exocytosis. Although there were quantitative differences, no fundamental difference was found in any of the abovementioned aspects of cellular function when the reticulocytes from Belgrade rats were compared with those from iron-deficient animals. The basic defect in the Belgrade reticulocytes must therefore reside in subsequent steps in iron uptake, after it is released from transferrin within endocytotic vesicles, ie, in the mechanism by which it is transferred across the lining membrane of the vesicles into the cell cytosol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of reticulocyte ghosts extracts demonstrated a prominent protein band of mol wt 69,000 that was absent or present only in low concentration extracts from the other two types of reticulocytes. This may be a result of the genetic defect.  相似文献   
15.
16.

Introduction

Fast track methodology or enhanced recovery schemes have gained increasing popularity in perioperative care. While evidence is strong for colorectal surgery, its importance in gastric and oesophageal surgery has yet to be established. This article reviews the evidence of enhanced recovery schemes on outcome for this type of surgery.

Methods

A systematic literature search was conducted up to March 2014. Studies were retrieved and analysed using predetermined criteria.

Results

From 34 articles reviewed, 18 eligible studies were identified: 7 on gastric and 11 on oesophageal resection. Three randomised controlled trials, five case-controlled studies and ten case series were identified. The reported protocols included changes to each stage of the patient journey from pre to postoperative care. The specific focus following oesophageal resections was on early mobilisation, a reduction in intensive care unit stay, early drain removal and early (or no) contrast swallow studies. Following gastric resections, the emphasis was on reducing epidural anaesthesia along with re-establishing oral intake in the first three postoperative days and early removal of nasogastric tubes.In the papers reviewed, mortality rates following fast track surgery were 0.8% (9/1,075) for oesophageal resection and 0% (0/329) for gastric resection. The reported morbidity rate was 16.5% (54/329) following gastric resection and 38.6% (396/1,075) following oesophageal resection. Length of stay was reduced in both groups compared with conventional recovery groups in comparative studies.

Conclusions

The evidence for enhanced recovery schemes following gastric and oesophageal resection is weak, with only three (low volume) published randomised controlled trials. However, the enhanced recovery approach appears safe and may be associated with a reduction in length of stay.  相似文献   
17.
Woods  VL Jr; Oh  EH; Mason  D; McMillan  R 《Blood》1984,63(2):368-375
Chronic idiopathic thrombocytopenic purpura (ITP) is caused by an antibody reactive with platelet-associated antigens. The present studies provide direct evidence that some patients with chronic ITP have autoantibodies against the platelet glycoprotein (GP) IIb/IIIa complex. Microtiter wells, coated with a monoclonal antibody (2G12) specific for GPIIb/GPIIIa were reacted with GPIIb/GPIIIa contained in a platelet extract. Control wells containing the same antibody were reacted with a cell extract containing no GPIIb/GPIIIa. After washing, the wells were reacted with patient or control plasma, and IgG binding was detected using 125I-Fab2-anti-human IgG. Assay values were expressed as binding ratios (cpm GPIIb/GPIIIa wells/cpm control wells). Plasma from 5 of 56 patients with chronic ITP had ratios (1.36-3.14) greater than 3 standard deviations above the mean (+/- SD) of control plasmas--0.93 +/- 0.12. Elevated values were also noted in two patients with anti-P1A1 antibody (ratios greater than 30) and in one patient with Hodgkin's disease and an ITP-like syndrome (ratio 1.53). Normal values were noted in 34 patients with a variety of immune and nonimmune diseases. Plasma from two of the positive ITP patients was reacted with 125I-surface-labeled platelets and, after solubilization, the IgG and bound antigen were precipitated with Staph-A. Autoradiographs from SDS- PAGE electrophoresis of the Staph-A-bound proteins shows two radioactive bands consistent in size with GPIIb and GPIIIa.  相似文献   
18.
19.

Background

The under-5 mortality rate (U5MR) is an important metric of child health and survival. Country-level estimates of U5MR are readily available, but efforts to estimate U5MR subnationally have been limited, in part, due to spatial misalignment of available data sources (e.g., use of different administrative levels, or as a result of historical boundary changes).

Methods

We analyzed all available complete and summary birth history data in surveys and censuses in six countries (Bangladesh, Cameroon, Chad, Mozambique, Uganda, and Zambia) at the finest geographic level available in each data source. We then developed small area estimation models capable of incorporating spatially misaligned data. These small area estimation models were applied to the birth history data in order to estimate trends in U5MR from 1980 to 2015 at the second administrative level in Cameroon, Chad, Mozambique, Uganda, and Zambia and at the third administrative level in Bangladesh.

Results

We found substantial variation in U5MR in all six countries: there was more than a two-fold difference in U5MR between the area with the highest rate and the area with the lowest rate in every country. All areas in all countries experienced declines in U5MR between 1980 and 2015, but the degree varied both within and between countries. In Cameroon, Chad, Mozambique, and Zambia we found areas with U5MRs in 2015 that were higher than in other parts of the same country in 1980. Comparing subnational U5MR to country-level targets for the Millennium Development Goals (MDG), we find that 12.8% of areas in Bangladesh did not meet the country-level target, although the country as whole did. A minority of areas in Chad, Mozambique, Uganda, and Zambia met the country-level MDG targets while these countries as a whole did not.

Conclusions

Subnational estimates of U5MR reveal significant within-country variation. These estimates could be used for identifying high-need areas and positive deviants, tracking trends in geographic inequalities, and evaluating progress towards international development targets such as the Sustainable Development Goals.
  相似文献   
20.
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