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   4970篇
  免费   483篇
  国内免费   32篇
耳鼻咽喉   85篇
儿科学   167篇
妇产科学   90篇
基础医学   680篇
口腔科学   112篇
临床医学   662篇
内科学   796篇
皮肤病学   105篇
神经病学   354篇
特种医学   377篇
外科学   607篇
综合类   81篇
现状与发展   1篇
一般理论   1篇
预防医学   556篇
眼科学   100篇
药学   373篇
  1篇
肿瘤学   337篇
  2022年   34篇
  2021年   59篇
  2020年   37篇
  2019年   58篇
  2018年   81篇
  2017年   42篇
  2016年   66篇
  2015年   94篇
  2014年   115篇
  2013年   178篇
  2012年   230篇
  2011年   207篇
  2010年   175篇
  2009年   157篇
  2008年   216篇
  2007年   231篇
  2006年   263篇
  2005年   193篇
  2004年   172篇
  2003年   181篇
  2002年   176篇
  2001年   160篇
  2000年   142篇
  1999年   131篇
  1998年   132篇
  1997年   94篇
  1996年   103篇
  1995年   95篇
  1994年   67篇
  1993年   81篇
  1992年   94篇
  1991年   97篇
  1990年   102篇
  1989年   112篇
  1988年   116篇
  1987年   81篇
  1986年   68篇
  1985年   75篇
  1984年   63篇
  1983年   43篇
  1982年   48篇
  1981年   39篇
  1980年   33篇
  1979年   48篇
  1978年   32篇
  1977年   34篇
  1976年   34篇
  1975年   39篇
  1973年   34篇
  1970年   30篇
排序方式: 共有5485条查询结果,搜索用时 15 毫秒
101.
The determination of the percentage of CO2 in the alveolar air, by the method of Haldane and Priestley, is sufficiently accurate for clinical purposes when the individual is at rest. It is evident, however, that an error may arise in the determination of the percentage of CO2 in the alveolar air, due to the time during the forced expiration, short of the extreme limit, at which the sample may be unconsciously taken. This error can only be overcome by taking several samples. In individuals at rest having a tidal air below 425 cubic centimeters, the method of Douglas and Haldane for the calculation of the dead space gives approximately accurate results; with a tidal air above 425 cubic centimeters the results obtained may be wholly inaccurate. In patients with marked pulmonary tuberculosis so slight an effort as that involved in collecting the expired air tends to lower the percentage of CO2 in the alveolar air. In collecting the expired air by the rubber bag method, it is absolutely essential that the bag be washed out with ordinary atmospheric air after every observation.  相似文献   
102.
Community coalitions are a recognized strategy for addressing pressing public health problems. Despite the promise of coalitions as an effective prevention strategy, results linking coalition efforts to positive community outcomes are mixed. To date, research has primarily focused on determining organizational attributes related to successful internal coalition functioning. The authors' research complements and adds to this literature by offering a network conceptualization of coalition formation in which coalition participation is studied within the broader context of local organizational networks both within and beyond a coalition. The authors examine participation in the first year of a youth violence prevention coalition exploring both differences between participating and nonparticipating organizations and levels of participation. Each network variable, reflecting prior collaboration and being viewed by other organizations as a local leader, approximately doubled the explained variance in coalition participation beyond the predictive power of all available organizational attributes combined. Results suggest that initial coalition participation emerged out of a preexisting network of interorganizational relations and provide an alternative perspective on coalition formation that goes beyond conceptual orientations that treat coalitions as bounded organizational entities that exist apart from the communities in which they are embedded.  相似文献   
103.
104.
105.
孙爱军  盛杰  王荣  马骏 《医学争鸣》2007,28(22):2103-2104
恶性肿瘤靶向给药是指利用具有一定肿瘤靶向性的导向分子(载体)携带治疗肿瘤的药物,在肿瘤局部选择性杀伤肿瘤细胞(及转移的肿瘤细胞),以避免药物的全身毒副作用,提高疗效的一种治疗方法.由于抗癌药物在杀伤肿瘤细胞的同时也杀伤正常细胞,增加了全身的毒副作用.因此,近几年来,对恶性肿瘤靶向治疗的研究突飞猛进,发展了人源性抗HER-2mAb、依西美坦、放射性核素、  相似文献   
106.
Human monoclonal antibodies neutralizing varicella-zoster virus   总被引:3,自引:0,他引:3  
Hybridomas secreting human monoclonal antibodies to varicella-zoster virus were produced by fusing B cells of a patient recovering from acute varicella infection with a human-mouse cell line. Two hybrid lines have continued to secrete IgG1, one with kappa and the other with lambda chains, for at least 12 months. Each antibody neutralizes virus infectivity between 1-5 micrograms of partially purified immunoglobulin/ml, each shows a different pattern of immunofluorescent staining of virus-infected cells, and one identifies three viral proteins with molecular weights of 60,000, 95,000, and 97,000.  相似文献   
107.

Background

The effectiveness of diclofenac versus paracetamol in primary care patients with pain caused by knee osteoarthritis is unclear.

Aim

To assess the effectiveness of diclofenac compared with paracetamol over a period of 2, 4, and 12 weeks in patients with knee osteoarthritis.

Design and setting

Randomised controlled trial in general practice.

Method

There were 104 patients included in the study, they were aged ≥45 years consulting their GP with knee pain caused by knee osteoarthritis. Patients were randomly allocated to diclofenac (n = 52) or paracetamol (n = 52) for at least 2 weeks. Primary outcomes were daily knee pain severity, and knee pain and function measured with the Knee Injury and Osteoarthritis Outcome Score (KOOS).

Results

Over a period of 2- and 4-weeks follow-up, no significant difference in daily knee pain was found between the patient groups: estimated differences of 0.5 (95% CI = −0.2 to 1.3) and −0.2 (95% CI = −1.0 to 0.7), respectively. Over the 12-weeks follow-up, no significant differences were found between both groups for KOOS pain: estimated difference of −2.8 (95% CI = −10.7 to 5.1) and KOOS function of −2.7 (−10.6 to 5.0).

Conclusion

Over a period of 2- and 4-weeks follow-up no significant difference in daily measured knee pain severity was found between primary care patients with knee osteoarthritis taking paracetamol or diclofenac. Also, over a period of 12-weeks follow-up no significant differences were found regarding KOOS pain and KOOS function between both groups. Patients more frequently reported minor adverse events after taking diclofenac (64%) than paracetamol (46%).  相似文献   
108.
Anaplastic large cell lymphoma (ALCL) comprises 10-15% of childhood non-Hodgkin lymphomas (NHL). Systemic ALCL is highly associated with anaplastic lymphoma kinase (ALK) gene translocations with over-expression of ALK protein. We studied ALK rearrangements using fluorescence in situ hybridisation (FISH) and ALK immunohistochemical staining in 43 paediatric systemic ALCLs. FISH (performed on 35 cases) identified a translocation in 29 cases (83%). Immunohistochemistry identified ALK over-expression in 42/43 cases (97%) with the single ALK-negative case demonstrating an ALK rearrangement by FISH, indicating 100% incidence of ALK translocations.  相似文献   
109.
Phospholipase A2 levels in acute chest syndrome of sickle cell disease   总被引:4,自引:2,他引:4  
Acute chest syndrome (ACS) is associated with significant morbidity and is the leading cause of death in patients with sickle cell disease (SCD). Recent reports suggest that bone marrow fat embolism can be detected in many cases of severe ACS. Secretory phospholipase A2 (sPLA2) is an important inflammatory mediator and liberates free fatty acids, which are felt to be responsible for the acute lung injury of the fat embolism syndrome. We measured SPLA2 levels in 35 SCD patients during 20 admissions for ACS, 10 admissions for vaso-occlusive crisis, and during 12 clinic visits when patients were at the steady state. Eleven non-SCD patients with pneumonia were also evaluated. To determine if there was a relationship between sPLA2 and the severity of ACS we correlated SPLA2 levels with the clinical course of the patient. In comparison with normal controls (mean = 3.1 +/- 1.1 ng/mL), the non- SCD patients with pneumonia (mean = 68.6 +/- 82.9 ng/mL) and all three SCD patient groups had an elevation of SPLA2 (steady state mean = 10.0 +/- 8.4 ng/mL; vaso-occlusive crisis mean = 23.7 +/- 40.5 ng/mL; ACS mean = 336 +/- 209 ng/mL). In patients with ACS sPLA2 levels were 100- fold greater than normal control values, 35 times greater than values in SCD patients at baseline, and five times greater than non-SCD patients with pneumonia. The degree of SPLA2 elevation in ACS correlated with three different measures of clinical severity and, in patients followed sequentially, the rise in SPLA2 coincided with the onset of ACS. The dramatic elevation of SPLA2 in patients with ACS but not in patients with vaso-occlusive crisis or non-SCD patients with pneumonia and the correlation between levels of SPLA2 and clinical severity suggest a role for SPLA2 in the diagnosis and, perhaps, in the pathophysiology of patients with ACS.  相似文献   
110.
Mice lacking the erythroid Kruppel-like factor (EKLF) die in utero at embryonic day 15 (E15) from severe anemia. EKLF(-/-) embryos display a marked deficit in beta-globin gene expression. To test whether beta-globin deficiency was solely responsible for the anemia and intrauterine death, we corrected the globin chain imbalance in EKLF(-/-) embryos by breeding with a strain of mice that express high levels of human gamma-globin. Despite efficient production of hybrid malpha(2)-hgamma(2) hemoglobin in the fetal livers of EKLF(-/-) animals, hemolysis was not corrected and survival was not prolonged. We concluded that deficiency of nonglobin EKLF target genes is a major contributor to the definitive red blood cell abnormalities and prenatal death in EKLF(-/-) embryos. These results suggest that strategies designed to antagonize EKLF function in adults with hemoglobinopathy, in an attempt to reactivate gamma-globin gene expression, may adversely affect other essential aspects of red blood cell physiology. (Blood. 2000;95:1827-1833)  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