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   5523篇
  免费   529篇
  国内免费   26篇
耳鼻咽喉   57篇
儿科学   173篇
妇产科学   186篇
基础医学   696篇
口腔科学   208篇
临床医学   584篇
内科学   1119篇
皮肤病学   226篇
神经病学   415篇
特种医学   297篇
外国民族医学   1篇
外科学   677篇
综合类   199篇
预防医学   522篇
眼科学   132篇
药学   311篇
中国医学   4篇
肿瘤学   271篇
  2022年   38篇
  2021年   76篇
  2020年   56篇
  2019年   81篇
  2018年   81篇
  2017年   76篇
  2016年   74篇
  2015年   91篇
  2014年   133篇
  2013年   168篇
  2012年   279篇
  2011年   256篇
  2010年   159篇
  2009年   183篇
  2008年   219篇
  2007年   261篇
  2006年   249篇
  2005年   212篇
  2004年   236篇
  2003年   220篇
  2002年   212篇
  2001年   212篇
  2000年   207篇
  1999年   177篇
  1998年   126篇
  1997年   96篇
  1996年   69篇
  1995年   71篇
  1994年   58篇
  1993年   66篇
  1992年   117篇
  1991年   110篇
  1990年   100篇
  1989年   109篇
  1988年   86篇
  1987年   112篇
  1986年   104篇
  1985年   74篇
  1984年   58篇
  1983年   75篇
  1982年   57篇
  1980年   33篇
  1979年   39篇
  1978年   45篇
  1975年   34篇
  1973年   39篇
  1972年   32篇
  1971年   40篇
  1970年   33篇
  1969年   32篇
排序方式: 共有6078条查询结果,搜索用时 31 毫秒
1.
2.
Background: Gastrointestinal stromal tumors (GIST) are one of the most common mesenchymal tumors of the gastrointestinal tract. GIST are defined by positive immunohistochemical staining for KIT or CD34 and thus are generally diagnosed after surgery. Because small GIST are rarely diagnosed before surgery, the clinical course of these small tumors is not clear. The aim of the present study was to follow changes in size and configuration of small GIST that were pathologically confirmed using endoscopic ultrasonography‐guided fine‐needle aspiration biopsy (EUS‐FNAB). Methods: Between July 1997 and December 2003, 16 tumors in 16 patients (10 men and 6 women) with an immunohistochemical diagnosis of GIST were regularly followed in our hospital. The median patient age when EUS‐FNAB was performed was 62 years (range 26–82 years) and the median follow‐up period was 4.9 years (range 0.5–9.6 years). Results: Fourteen tumors showed no remarkable changes in size and shape during follow up compared with the initial diagnosis. Two tumors enlarged: one tumor approximately doubled its diameter in 8 years and the other tumor increased from 1.8 cm at diagnosis to up to 10 cm after only 2 years. Doubling time of the latter tumor was calculated as 3.1 months. Conclusions: We conclude that EUS‐FNAB might be a good modality for final diagnosis of GIST without surgery, and that GIST without rapid growth on follow up can be endoscopically followed.  相似文献   
3.
Reproductive problems, including congenital malformations, reduced hatching success, and decreased survival of hatchlings, have been observed in colonial-nesting water birds at the San Francisco Bay National Wildlife Refuge (SFBNWR). Twenty-four black-crowned night heron (Nycticorax nycticorax) eggs were collected from SFBNWR in 1983. Twelve of these were collected from separate nests when late-stage embryos were pipping, and an additional egg was randomly collected from each nest for organochlorine analysis. Overt anomalies and skeletal defects were not apparent. Embryonic weights (with partially absorbed yolk sacs removed) were 15% lower (p less than 0.05) in SFBNWR embryos compared to control embryos from the Patuxent Wildlife Research Center (PWRC). Crown-rump length and femur length were shorter for SFBNWR embryos. The geometric mean polychlorinated biphenyl (PCB) concentration in SFBNWR eggs was 4.1 ppm wet weight, with a range of 0.8-52.0 ppm. A negative correlation (r = -0.61; p less than 0.05) existed between embryonic weight and log-transformed PCB residues in whole eggs collected from the same nest at SFBNWR, suggesting a possible impact of PCBs on embryonic growth. A correlation with embryonic weight did not occur for DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene] residues. Liver microsomal aryl hydrocarbon hydroxylase activity was neither significantly elevated nor correlated with PCB, DDE, or PCB plus DDE log-transformed residues. It is unknown whether the apparent association between PCBs and lower weight is persistent through hatching.  相似文献   
4.
5.
Plasma viscosity, molecular markers of activated coagulation and fibrinolysis (fibrinopeptides A and B beta 15-42), coagulation factors (fibrinogen and factor VII) and antiplasmins were measured in 529 men aged 35-54 years and related to new angina pectoris (n = 117) and to coronary risk factors in controls without angina (n = 412). Five major risk factors (cigarette-smoking, blood pressure, cholesterol, triglyceride and body mass index) were each associated with increases in plasma viscosity, coagulation factors, and imbalance of coagulation over fibrinolysis (increased ratio of fibrinopeptide A/fibrinopeptide B beta 15-42). Increased viscosity and fibrinogen in smokers were partly reversed in ex-smokers, but the imbalance of coagulation and fibrinolysis persisted. Cholesterol and triglyceride were also associated with increased antiplasmin activity. In men with angina, only fibrinogen was elevated compared to controls. We suggest that increased plasma viscosity and an imbalance of coagulation over fibrinolysis may be mechanisms by which known risk factors promote arterial thrombosis, but are not present in stable angina.  相似文献   
6.
Coronary artery bypass grafts: visualization with MR imaging   总被引:1,自引:0,他引:1  
Gomes  AS; Lois  JF; Drinkwater  DC  Jr; Corday  SR 《Radiology》1987,162(1):175
  相似文献   
7.
8.
We have compared the effects of acetyl salicylic acid (ASA, aspirin) and choline magnesium trisalicylate (CMT), a non-acetylated salicylate product, on platelet aggregation in human whole blood ex-vivo. Using a whole blood platelet counter, platelet aggregation was quantified by measuring the fall in the number of single platelets at peak aggregation in response to collagen, arachidonic acid (AA), as well as spontaneous aggregation. In double blind and random order, 12 healthy volunteers received, on two separate occasions 10 days apart, a single oral dose of 652 mg ASA or 655 mg CMT. Despite a comparable absorption of salicylic acid from the two drugs, ingestion of ASA resulted in a marked inhibition of platelet aggregation induced by collagen (p less than 0.005), AA (p less than 0.01) and spontaneous aggregation (p less than 0.01), whereas such effects were not observed after CMT ingestion. We suggest that CMT may have therapeutic potential as an alternative to aspirin when inhibition of platelet aggregation can induce bleeding complications.  相似文献   
9.
10.
Background Out of area placements for people with challenging behaviour represent an expensive and often ineffective strategy for meeting the needs of this service user group. Methods More than 800 agencies and service settings in a large area of South Wales were screened to identify children and adults with challenging behaviour against a number of defined operational criteria. Detailed data on identified individuals and the services they received were collected by interviewing key informants. Univariate and multivariate statistics were employed to identify predictors of out of area placement. Results In total, 1458 people were identified. Full data were available for 901 participants, 97 of whom were placed out of area. Predictors of out of area placement included behaviours resulting in physical injury and exclusion from service settings, a history of formal detention under the mental health act, the presence of mental health problems, a diagnosis of autism and higher total score on the Adaptive Behaviour Scale. Out of area placements were typically of high cost, and associated with only limited evidence of improved service quality. Conclusions Identifying predictors for out of area placement can be used to highlight deficiencies in local services and individuals at increased risk of exclusion from local services.  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