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   1910篇
  免费   319篇
  国内免费   8篇
耳鼻咽喉   2篇
儿科学   144篇
妇产科学   282篇
基础医学   144篇
口腔科学   27篇
临床医学   846篇
内科学   179篇
皮肤病学   60篇
神经病学   14篇
特种医学   235篇
外科学   55篇
综合类   56篇
预防医学   87篇
眼科学   5篇
药学   47篇
肿瘤学   54篇
  2024年   4篇
  2023年   43篇
  2021年   7篇
  2020年   34篇
  2019年   18篇
  2018年   57篇
  2017年   90篇
  2016年   76篇
  2015年   98篇
  2014年   101篇
  2013年   97篇
  2012年   38篇
  2011年   59篇
  2010年   101篇
  2009年   100篇
  2008年   51篇
  2007年   54篇
  2006年   44篇
  2005年   31篇
  2004年   19篇
  2003年   37篇
  2002年   30篇
  2001年   43篇
  2000年   22篇
  1999年   57篇
  1998年   102篇
  1997年   114篇
  1996年   110篇
  1995年   97篇
  1994年   66篇
  1993年   52篇
  1992年   32篇
  1991年   31篇
  1990年   18篇
  1989年   32篇
  1988年   41篇
  1987年   22篇
  1986年   30篇
  1985年   29篇
  1984年   16篇
  1983年   15篇
  1982年   18篇
  1981年   12篇
  1980年   15篇
  1979年   4篇
  1978年   16篇
  1977年   15篇
  1976年   15篇
  1975年   16篇
  1974年   2篇
排序方式: 共有2237条查询结果,搜索用时 15 毫秒
81.
82.
Confluent cultures of endothelial cells from human umbilical cord were used to study the effect of activated human protein C (APC) on the production of plasminogen activators, plasminogen activator-inhibitor, and factor VIII-related antigen. Addition of APC to the cells in a serum-free medium did not affect the production of tissue-type plasminogen activator (t-PA) or factor VIII-related antigen; under all measured conditions, no urokinase activity was found. However, less plasminogen activator-inhibitor activity accumulated in the conditioned medium in the presence of APC. This decrease was dose dependent and could be prevented by specific anti-protein C antibodies. No decrease was observed with the zymogen protein C or with diisopropylfluorophosphate-inactivated APC. APC also decreased the t-PA inhibitor activity in endothelial cell-conditioned medium in the absence of cells, which suggests that the effect of APC is at least partly due to a direct effect of APC on the plasminogen activator- inhibitor. High concentrations of thrombin-but not of factor Xa or IXa-- had a similar effect on the t-PA inhibitor activity. The effect of APC on the plasminogen activator-inhibitor provides a new mechanism by which APC may enhance fibrinolysis. The data suggest that activation of the coagulation system may lead to a secondary increase of the fibrinolytic activity by changing the balance between plasminogen activator(s) and its (their) fast-acting inhibitor.  相似文献   
83.
84.
Objective  To determine which interventions for managing placenta accreta were associated with reduced maternal morbidity.
Design  Retrospective cohort study.
Setting  Two tertiary care teaching hospitals in Utah.
Population  All identified cases of placenta accreta from 1996 to 2008.
Methods  Cases of placenta accreta were identified using standard ICD-9 codes for placenta accreta, placenta praevia, and caesarean hysterectomy. Medical records were then abstracted for maternal medical history, hospital course, and maternal and neonatal outcomes. Maternal and neonatal complications were compared according to antenatal suspicion of accreta, indications for delivery, preoperative preparation, attempts at placental removal before hysterectomy, and hypogastric artery ligation.
Main outcome measures  Early morbidity (prolonged maternal intensive care unit admission, large volume of blood transfusion, coagulopathy, ureteral injury, or early re-operation) and late morbidity (intra-abdominal infection, hospital re-admission, or need for delayed re-operation).
Results  Seventy-six cases of placenta accreta were identified. When accreta was suspected, scheduled caesarean hysterectomy without attempting placental removal was associated with a significantly reduced rate of early morbidity compared with cases in which placental removal was attempted (67 versus 36%, P = 0.038). Women with preoperative bilateral ureteric stents had a lower incidence of early morbidity compared with women without stents (18 versus 55%, P = 0.018). Hypogastric artery ligation did not reduce maternal morbidity.
Conclusions  Scheduled caesarean hysterectomy with preoperative ureteric stent placement and avoiding attempted placental removal are associated with reduced maternal morbidity in women with suspected placenta accreta.  相似文献   
85.
86.
Every day in clinical settings, nurses practise in complex and dynamic situations. Nurses work to achieve emergent order in these situations through nursing prioritization of the patient need for care. As direct research on nursing prioritization had not been reported, a study, using critical realism as method, was designed to discern the profession's embedded understanding from within the clinical decision-making literature. The research synthesizes a tacit knowledge on nursing prioritization of the patient need for care from key international literature (from 1966 to 2003). Nursing prioritization was discerned in both education and practice literatures; interrelationships between these and theoretical approaches were also identified. Nursing prioritization of the patient need for care was revealed both as a non-sequential decision-making process throughout unfolding patient situations and as an advanced skill of nursing practice. Increasing confidence with this skill is the hallmark of developing expertise.  相似文献   
87.
88.
Chronic active plasmacytic gastritis (CAPG) is characterized by the presence of chronic inflammatory cell infiltrates, mainly formed by plasma cells, involving the neck of gastric glands. This lesion, as well as Ménétrier disease, has been linked to cytomegalovirus (CMV). To test this association we evaluated the foveolar/glandular (F/G) index and the presence of CMV DNA (desoxirribonucleic acid) by means of polymerase chain reaction (PCR) in 12 cases of CAPG and 13 controls. Cases exhibiting CAPG included 2 with Ménétrier disease, 6 with foveolar hyperplasia, and 3 with normal foveolar/glandular (F/G) index. None showed either lymphocytic gastritis or CMV inclusions. Three CAPG cases were associated with gastric carcinoma. The F/G index was less than 1 in all controls. Eleven out of the 12 cases with CAPG showed amplification for CMV DNA while all controls were negative. Findings suggest a very close association, probably in progressive stages, between CMV infection, CAPG, foveolar hyperplasia (with or without Ménétrier disease) and gastric carcinoma. CAPG might be a histologic marker for CMV infection in the germinative zone of the neck of gastric glands. These findings resemble those of hepatitis B virus (HBV) infection, chronic hepatitis, cirrhosis, and hepatocellular carcinoma saga.  相似文献   
89.

Background  

Problematic waiting lists in public health care threaten the equity and timeliness of care provision in several countries. This study assesses different stakeholders' views on the acceptability of waiting lists in health care, their preferences for priority care of patients, and their judgements on acceptable waiting times for surgical patients.  相似文献   
90.
目的:评估人工流产(指手术流产)对乳腺癌危险性的可能影响。方法:研究在上海267040例妇女的一项乳房自我检查随机试验的队列人群中进行,由队列研究和巢式病例对照研究两部分组成。结果:依据基线调查表采集的资料分析,人工流产不增加乳腺癌危险性。调整潜在的混淆因素后,OR=1.06(95%CI:0.91~1.25)。人工流产次数增加无危险性趋势增加。从更详细的652例乳腺癌病例和694例对照资料分析,得出相似的结果。人工流产发生在首次生育后不增加危险性;少数妇女在首次生育前人工流产以及妊娠13周后人工流产,虽然被观察到危险性有增加,但无显著性统计学意义。结论:在中国,人工流产不是乳腺癌发生的重要原因。  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