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   798篇
  免费   62篇
  国内免费   22篇
耳鼻咽喉   1篇
儿科学   39篇
妇产科学   13篇
基础医学   78篇
口腔科学   15篇
临床医学   99篇
内科学   224篇
皮肤病学   1篇
神经病学   44篇
特种医学   174篇
外科学   47篇
综合类   13篇
预防医学   63篇
眼科学   4篇
药学   37篇
中国医学   1篇
肿瘤学   29篇
  2023年   4篇
  2022年   2篇
  2021年   5篇
  2020年   2篇
  2019年   6篇
  2018年   12篇
  2017年   7篇
  2016年   4篇
  2015年   9篇
  2014年   13篇
  2013年   31篇
  2012年   16篇
  2011年   22篇
  2010年   17篇
  2009年   12篇
  2008年   19篇
  2007年   32篇
  2006年   23篇
  2005年   30篇
  2004年   27篇
  2003年   20篇
  2002年   24篇
  2001年   14篇
  2000年   18篇
  1999年   21篇
  1998年   31篇
  1997年   28篇
  1996年   39篇
  1995年   24篇
  1994年   19篇
  1993年   29篇
  1992年   28篇
  1991年   19篇
  1990年   22篇
  1989年   31篇
  1988年   34篇
  1987年   30篇
  1986年   20篇
  1985年   23篇
  1984年   13篇
  1983年   11篇
  1982年   20篇
  1981年   10篇
  1980年   10篇
  1979年   6篇
  1978年   2篇
  1977年   9篇
  1976年   19篇
  1975年   7篇
  1935年   2篇
排序方式: 共有882条查询结果,搜索用时 15 毫秒
1.
2.
3.
The effect of sera and purified IgG isolated from plasma of 46 patients with systemic lupus erythematosus (SLE) and 9 healthy donors on the endothelial cell (EC) mediated protein C activation was investigated. Out of the 46 SLE sera used, 19 were antiphospholipid antibodies (aPL) positive. From 12 patients IgG was isolated, of which 6 contained aPL. EC were first incubated with IgG (7 mg/ml) or serum (1:1 diluted) for 1 h and then tested for their ability to promote protein C activation by thrombin, with the cells either in a monolayer or in a suspension. The normal range (mean of control values +/- 2 SD) of protein C activation was 80-120%. In contrast to others, we could not detect an inhibition of protein C activation by any of the patient IgG's or sera. The recently described cofactor for binding of antiphospholipid antibodies to phospholipids, beta 2-glycoprotein I, was purified and added to the purified IgG's. A combination of these two components did not inhibit the EC mediated protein C activation by thrombin. This study suggests that the inhibition of the protein C activation, mediated by EC, is not a general mechanism by which aPL related thrombosis can be explained.  相似文献   
4.
Retrosternal dislocation of the clavicle is an uncommon injury which may affect the mediastinal structures in a life-threatening way. Therefore, computed tomography is mandatory. Manipulation in the acute situation is the treatment of choice. In case of failure or old dislocation, open reduction with stabilization of the joint is required. The literature on this subject has been reviewed and an additional two cases are reported.  相似文献   
5.
Ultrasound scans of 51 consecutive patients with gallbladder wall thickening were reviewed, and specific sonographic features were correlated with surgical and clinical follow-up. Two patterns of thickening were identified as specific indicators of the presence or absence of acute cholecystitis. "Striated" wall thickening, consisting of several alternating, irregular, discontinuous, lucent and echogenic bands, was seen in eight of 13 patients (62%) with acute cholecystitis. This pattern was not encountered in any of the patients who did not have acute cholecystitis. Conversely, "three-layer" thickening, consisting of a single circumferential lucent zone between two relatively uniform echogenic layers, was seen in only one of 13 patients (8%) with acute cholecystitis but in 11 of 38 patients (29%) with other diagnoses. Other abnormalities, including the presence of intramural echogenic foci and wall irregularities, were more frequently seen in patients with acute cholecystitis but were not as helpful. Use of these features may suggest or help exclude a diagnosis of acute cholecystitis in those patients in whom the cause of gallbladder wall thickening is otherwise not apparent.  相似文献   
6.
OBJECTIVE: To describe regional trends in premature mortality in Manitoba. DESIGN: Comparison of all-cause and cause-specific mortality of persons less than age 75 in 11 Regional Health Authority populations over two time periods: 1985-89 and 1990-94. RESULTS: The provincial premature mortality rate declined over the two time periods (4.00/1,000 to 3.72/1,000). Declines were also observed in 9 of 11 regional populations. Premature mortality increased, however, in the 2 regional populations with the highest mortality rates in the first observation period. CONCLUSION: Declining premature mortality in low mortality populations and rising premature mortality in high mortality populations has resulted in a widening of regional mortality rates in Manitoba. Recent policy initiatives in many provinces, including the devolution of authority for the management and delivery of health services and the implementation of population need-based funding formulas to share health care resources among regional health authorities, if implemented, have the potential to partially mitigate the processes producing these widening regional health inequalities.  相似文献   
7.
8.
OBJECTIVE: To evaluate the impact of zinc supplementation on the clinical course, stool weight, duration of diarrhoea, changes in serum zinc, and body weight gain of children with acute diarrhoea. DESIGN: Randomised double blind controlled trial. Children were assigned to receive zinc (20 mg elemental zinc per day) containing multivitamins or control group (zinc-free multivitamins) daily in three divided doses for two weeks. SETTING: A diarrhoeal disease hospital in Dhaka, Bangladesh. PATIENTS: 111 children, 3 to 24 months old, below 76% median weight for age of the National Center for Health Statistics standard with acute diarrhoea. Children with severe infection and/or oedema were excluded. MAIN OUTCOME MEASURES: Total diarrhoeal stool output, duration of diarrhoea, rate of weight gain, and changes in serum zinc levels after supplementation. RESULTS: Stool output was 28% less and duration 14% shorter in the zinc supplemented group than placebo (p = 0.06). There were reductions in median total diarrhoeal stool output among zinc supplemented subjects who were shorter (less than 95% height for age), 239 v 326 g/kg (p < 0.04), and who had a lower initial serum zinc (< 14 mmol/l), 279 v 329 g/kg (p < 0.05); a shortening of mean time to recovery occurred (4.7 v 6.2 days, p < 0.04) in those with lower serum zinc. There was an increase in mean serum zinc in the zinc supplemented group (+2.4 v -0.3 mumol/l, p < 0.001) during two weeks of supplementation, and better mean weight gain (120 v 30 g, p < 0.03) at the time of discharge from hospital. CONCLUSIONS: Zinc supplementation is a simple, acceptable, and affordable strategy which should be considered in the management of acute diarrhoea and in prevention of growth faltering in children specially those who are malnourished.  相似文献   
9.
ObjectiveTo evaluate the effects of early pregnancy loss on subsequent health care use and costs.Data SourcesLinked administrative health databases from Manitoba, Canada.Study DesignThis was a population‐based cohort study. The exposure of interest was first recorded ectopic pregnancy or miscarriage (EPM). Outcomes included visits to all ambulatory care providers, family physicians (FPs), specialists, and hospitals, as well as the costs associated with these visits. We also assessed the impact of EPM on a global measure of health service utilization and the incidence and costs of psychotropic medications.Data Collection/Extraction MethodsWe identified women who experienced their first recorded loss (EPM) from 2003–2012 and created a propensity score model to match these women to women who experienced a live birth, with outcome measures available through 31 December 2014. We used a difference in differences approach with multivariable negative binomial models and generalized estimating equations (GEE) to assess the impact of EPM on the aforementioned health care utilization indicators.Principal FindingsEPM was associated with a short‐term increase in visits to, and costs associated with, certain ambulatory care providers. These findings were driven in large part by increased visits/costs to FPs (rate difference [RD]: $19.92 [95% CI: $16.33, $23.51]) and obstetrician‐gynecologists (OB‐GYNs) (RD $9.41 [95% CI: $8.42, $10.40]) in the year immediately following the loss, excluding care associated with the loss itself. We also detected an increase in hospital stays and costs and a decrease in the use of psychotropic medications relative to matched controls.ConclusionPregnancy loss may lead to subsequent increases in certain types of health care utilization. While the absolute costs associated with post‐EPM care are relatively small, the observed patterns of service utilization are informative for providers and policy makers seeking to support women following a loss.  相似文献   
10.
赵明  黄如衡 《药学学报》1990,25(11):801-806
用离体大鼠肝脏灌流方法,研究了胆碱酯酶抑制剂CXN的生物转化过程。径HPLC分离纯化及光谱分析,鉴定了CXN的六个脂溶性代谢产物的化学结构。产物Ⅰ为CXN原形,其余均为氧化产物。其中产物Ⅲ尚保留部分抑酶活力,而产物Ⅱ,Ⅴ及Ⅵ对小鼠全脑胆碱酯酶的抑酶活力明显下降。另外还观察到,代谢产物Ⅱ及Ⅴ对小鼠的急性毒性也明显减小。  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