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   21313篇
  免费   1157篇
  国内免费   518篇
耳鼻咽喉   140篇
儿科学   535篇
妇产科学   287篇
基础医学   2275篇
口腔科学   379篇
临床医学   2038篇
内科学   3531篇
皮肤病学   165篇
神经病学   2201篇
特种医学   673篇
外国民族医学   1篇
外科学   1957篇
综合类   2869篇
现状与发展   1篇
预防医学   2129篇
眼科学   332篇
药学   1717篇
  10篇
中国医学   623篇
肿瘤学   1125篇
  2024年   26篇
  2023年   374篇
  2022年   905篇
  2021年   1001篇
  2020年   870篇
  2019年   748篇
  2018年   793篇
  2017年   672篇
  2016年   733篇
  2015年   734篇
  2014年   1477篇
  2013年   1678篇
  2012年   1242篇
  2011年   1383篇
  2010年   1081篇
  2009年   1050篇
  2008年   994篇
  2007年   946篇
  2006年   835篇
  2005年   690篇
  2004年   613篇
  2003年   481篇
  2002年   422篇
  2001年   324篇
  2000年   347篇
  1999年   300篇
  1998年   241篇
  1997年   217篇
  1996年   217篇
  1995年   191篇
  1994年   201篇
  1993年   151篇
  1992年   135篇
  1991年   134篇
  1990年   92篇
  1989年   92篇
  1988年   93篇
  1987年   64篇
  1986年   49篇
  1985年   63篇
  1984年   59篇
  1983年   38篇
  1982年   50篇
  1981年   27篇
  1980年   36篇
  1979年   28篇
  1978年   26篇
  1977年   19篇
  1976年   9篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Background. The National Heart, Lung, and Blood Institute (NHLBI) guidelines recommend that patients receive a follow-up outpatient asthma visit after being discharged from an emergency department (ED) for asthma. Objective. To measure the frequency of follow-up outpatient asthma visits and its association with repeat ED asthma visit. Design. We conducted a retrospective cohort study of children with asthma using claims data from a university-based managed care organization from 01 1998 to 10 2000. We performed a multivariate survival analysis using Cox proportional hazards model to determine the effect of follow-up outpatient asthma visits on the likelihood of a repeat ED asthma visit, after controlling for severity of illness, patient age, gender, insurance, and the specialty of the primary care provider. Results: A total of 561 children had 780 ED asthma visits. Of these, 103 (17%) had a repeat ED asthma visit within 1 year. Almost two-thirds of children (66%) did not receive outpatient follow-up for asthma within 30 days of an ED asthma visit. Outpatient asthma visits within 30 days of an ED asthma visit are associated with an increased likelihood (relative risk = 1.80; 95% confidence interval 1.19, 2.72) for repeat ED asthma visits within 1 year. Conclusions. Most patients do not have outpatient follow-up after an ED asthma visit. However, those patients that present for outpatient follow-up have an increased likelihood for repeat ED asthma visits. For the primary care provider, these outpatient follow-up visits signal an increased risk that a patient will return to the ED for asthma and are a key opportunity to prevent future ED asthma visits.  相似文献   
12.
Summary This cross-sectional study was conducted to investigate the prevalence of intestinal parasites among primary school children in Northern Jordan. Stool specimens were collected from 1100 children of both sexes from urban and rural schools. A questionnaire covering relevant informations was completed for each child. Wet mount preparation, formaline-ether concentration technique, and trichrome stain were prepared for the recovery and identification of parasites. Giardia lamblia was observed in 396 (36%) of the stool specimens examined. The infection rates were higher in the younger age group where several of them had diarrhoea and reported variable symptoms. The infection rates declined with age and children were asymptomatic. Rates were higher in children from the rural areas, from low income families, and it was higher in boys than girls.
Contaminated drinking water is suspected to be the major potential source of infection. The importance of the asymptomatic cases and the epidemiological factors contributing to the transmission in these areas are discussed.  相似文献   
13.
本文用X线摄片的方法,对西宁地区胎龄为17—36周的60例胎儿脊柱的骨化及生长动态进行了研究。结果:1、提供了高原地区人胎儿脊柱长轴生长发育的资料。脊柱各段以胸段为最长,其次为腰、颈、骶段。2、计算出胎龄与脊柱各段长度间的回归方程,据此可以胎龄推算脊柱的长度,反之亦可以脊柱的长度估计胎龄。3、报道了颈、骶、尾段亿发骨化点出现顺序的规律。  相似文献   
14.
 In order to determine the dynamics of hematopoietic cell turnover, proliferative activity and incidence of apoptosis (programmed cell death) were evaluated in bone marrow trephine biopsies. Selection of patients (20 in each group) included in addition to a control group, idiopathic thrombocytopenia (ITP), reactive thrombocytosis (TH), secondary polycythemia-smokers' polyglobuly (PG), primary (essential-hemorrhagic) thrombocythemia (PTH), polycythemia vera (PV), and finally acute myeloid leukemia (AML). Apoptosis was demonstrated by the in situ end-labeling technique (ISEL) and proliferative activity by applying the monoclonal antibody PC10 raised against proliferating cell nuclear antigen (PCNA). To assess dynamic features of hematopoiesis, an index was calculated consisting of the ratio between PCNA-positive nuclei and the apoptotic cell fraction. This factor was termed the hematopoietic turnover index (HTI). Morphometric analysis revealed that the HTI was significantly increased in AML and PV. According to cell culture studies both disorders are characterized by either a prevalent proliferation of the myeloid or erythroid cell mass. On the other hand, PG, PTH, and TH showed no relevant enhancement of this index in comparison to the control specimen. In vitro experiment results are in keeping with the finding that PG and PTH are not associated with a significant expansion of the erythroid lineage (CFU-E). Similar to ITP and TH, in PTH megakaryocyte proliferation (CFU-MEG) is the predominant feature of cell turnover. Differences between PTH and TH are in line with the reduced in vitro formation of CFU-MEG in the latter disorder. In conclusion, our in situ study on turnover rates of the bone marrow in various neoplastic and reactive lesions extends previous experimental data on hematopoietic cell kinetics. Received: 10 March 1997 / Accepted: 18 May 1997  相似文献   
15.
Splenic irradiation has been used in patients with HIV-related thrombocytopenia. This retrospective review deals with four patients treated with low dose splenic irradiation. All patients had an increase in platelet count and tolerated the treatment without side effects. However, the treatment response lasted for several months only.  相似文献   
16.
17.
Data on the effects of laser radiation on primary teeth are scarce. This study investigates the effects of exposing sound enamel, photo-initiated sound enamel, sound dentine and carious dentine of extracted primary teeth to a pulsed neodymium-yttrium aluminium garnet laser (Nd-YAG, wavelength 1.06 μm, pulse length 15μs). Each type of tissue was exposed to three fiuences. Qualitative and quantitative assessments of the irradiated areas revealed that the most marked changes were produced in carious dentine, followed in ranking order by sound dentine, photo-initiated enamel and sound enamel. Evidence of thermal damage to the hard tissues peripheral to the fibre-optic tip, and considerable inter-sample variation were found. The experimental evidence obtained in this in vitro study does not support the clinical use of pulsed laser at 1.06 μm wavelength for cutting primary enamel and dentine.  相似文献   
18.
Summary. We present a case of primary plasmocytoma of the left upper bronchus. Occlusion led to atelectasis of the left upper lobe and subsequent poststenotic pneumonia. Therapy consisted of local excision of the bronchus and postoperative radiotherapy. This type of lung-conserving therapy in a case of primary plasmocytoma has not been described before.   相似文献   
19.
66例成人原发肾病综合征临床治疗与病理分析   总被引:1,自引:0,他引:1  
刘然  田松 《北京医学》1995,17(4):217-220
本对66例原发肾病综合征患进行病理类型与临床疗效分析。最常见病理类型为系膜增殖性肾炎,占42.5%,其次为膜性肾病,占32.5%,IgA肾病占15.0%。微小病变型及系膜增殖性肾炎对激素及免疫抑制剂治疗效果好,膜性肾病治疗效果差。不同病理类型患病理损害程度与疗效相关。伴肾小管间质病变治疗效果差(P〈0.05)。NSⅠ型疗效明显优于NSⅡ型(P〈0.05)。50岁以下原发肾病综合征(PNS)  相似文献   
20.
本文报道100例原发全身性癫痫家系的遗传流行病学研究结果。先证者一级亲属患病率为6.86%,二级亲属为1.03%;分别是对照组一级亲属的13.83倍和2.08倍。原发全身性癫痫的遗传度为:一级亲属0.7521±0.0678,二级亲属0.3592±0.0746;加权平均0.5743±0.0502。说明遗传因素起重要作用。发病年龄影响因素分析表明:原发全身性癫痫有一定年龄依从性。EEG家系分析显示,该型癫痫一级亲属癫痫样放电明显高于对照组一级亲属,提示癫痫样放电的遗传倾向。  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