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   34324篇
  免费   2788篇
  国内免费   412篇
耳鼻咽喉   362篇
儿科学   1012篇
妇产科学   616篇
基础医学   4976篇
口腔科学   519篇
临床医学   3234篇
内科学   7367篇
皮肤病学   763篇
神经病学   2592篇
特种医学   1294篇
外国民族医学   16篇
外科学   4277篇
综合类   1282篇
现状与发展   1篇
一般理论   2篇
预防医学   2645篇
眼科学   706篇
药学   2591篇
  6篇
中国医学   618篇
肿瘤学   2645篇
  2023年   246篇
  2022年   592篇
  2021年   1089篇
  2020年   676篇
  2019年   853篇
  2018年   1051篇
  2017年   760篇
  2016年   751篇
  2015年   925篇
  2014年   1183篇
  2013年   1541篇
  2012年   2210篇
  2011年   2212篇
  2010年   1365篇
  2009年   1134篇
  2008年   1635篇
  2007年   1666篇
  2006年   1599篇
  2005年   1503篇
  2004年   1337篇
  2003年   1273篇
  2002年   1202篇
  2001年   1115篇
  2000年   1101篇
  1999年   978篇
  1998年   349篇
  1997年   300篇
  1996年   265篇
  1995年   211篇
  1994年   208篇
  1993年   175篇
  1992年   518篇
  1991年   499篇
  1990年   475篇
  1989年   432篇
  1988年   452篇
  1987年   380篇
  1986年   372篇
  1985年   365篇
  1984年   255篇
  1983年   187篇
  1982年   119篇
  1981年   103篇
  1979年   210篇
  1978年   111篇
  1977年   124篇
  1976年   113篇
  1974年   130篇
  1972年   128篇
  1969年   104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
目的 研究性别对癫痫患者维库溴铵量效关系的影响,为维库溴铵个体化应用提供参考. 方法 选取择期癫痫手术患者100例,美国麻醉医师协会(ASA)分级Ⅰ~Ⅱ级,年龄19岁~4l岁,病史2年~23年,分为男性组(M组)与女性组(F组),每组各50例,均有服用抗癫痫药物史,术前无酸碱平衡及水电解质紊乱,心、肺、肝、肾功能正常.每组患者按随机数字表法分为20、30、40、50、60 μg/kg 5个剂量组,每组10例.记录拇内收肌四个成串刺激(train of four stimulation,TOF)第1次反应最大抑制的百分率并进行概率单位转换,将维库溴铵的首次剂量进行对数转换,用直线回归方法分别建立男、女患者维库溴铵剂量-反应曲线,并记录起效时间. 结果 男性癫痫患者维库溴铵50%有效量(50% effective dose,ED50)、75%有效量(75%effective dose,ED75)、90%有效量(90% effective dose,ED90)、95%有效量(95% effective dose,ED95)值分别为(31±6)、(40±8)、(50±9)、(57±7)tμg/kg,女性癫痫患者维库溴铵ED50、ED75、ED90、ED95值分别为(31±6)、(40±7)、(50±9)、(58±9) μg/kg,两者间差异无统计学意义(P>0.05);5个剂量组起效时间在性别组间比较,差异无统计学意义(P>0.05). 结论 性别不影响癫痫患者维库溴铵的剂量-反应曲线.  相似文献   
982.
983.

Background:

Spinocerebellar ataxias (SCAs) are a group of neurodegenerative disorders that primarily cause the degeneration in the cerebellum, spinal cord, and brainstem. We study the clinical characteristics, radiological features and gene mutation in Chinese families with SCAs.

Methods:

In this study, we investigated 10 SCAs Chinese families with SCA1, SCA3/Machado–Joseph disease (MJD), SCA7, SCA8. There were 27 people who were genetically diagnosed as SCA, of which 21 people showed clinical symptoms, and 6 people had no clinical phenotype that we called them presymptomatic patients. In addition, 3 people with cerebellar ataxia and cataracts were diagnosed according to the Harding diagnostic criteria but failed to be recognized as SCAs on genetic testing. Clinical characteristic analyses of each type of SCAs and radiological examinations were performed.

Results:

We found that SCA3/MJD was the most common subtype in Han population in China, and the ratio of the pontine tegmentum and the posterior fossa area was negatively correlated with the number of cytosine-adenine-guanine (CAG) repeats; the disease duration was positively correlated with the International Cooperative Ataxia Rating Scale score; and the CAG repeats number of abnormal alleles was negatively correlated with the age of onset.

Conclusions:

Collectively our study is a systematic research on SCAs in China, which may help for the clinical diagnosis and prenatal screening of this disease, and it may also aid toward better understanding of this disease.  相似文献   
984.
探讨乌索酸通过调控miR-21表达从而诱导肝癌HepG2细胞凋亡的作用机制。采用MTT方法检测乌索酸对肝癌细胞增殖的抑制作用;qPCR检测肝癌细胞中miR-21的表达水平及乌索酸对HepG2细胞中miR-21表达的调控作用;转染miR-21 mimics进HepG2细胞中上调miR-21的表达后,MTT、流式细胞检测法、RT-PCR方法分别分析miR-21在乌索酸对细胞的增殖、凋亡以及对凋亡相关基因的调控过程中的作用。结果显示,与肝正常细胞L-02以及肝癌SMCC-7721、Bel-7402细胞相比较,乌索酸对肝癌HepG2细胞的增殖抑制效果最强,且HepG2细胞中miR-21的表达水平最高。乌索酸可下调HepG2细胞中miR-21的表达,且在24 h的下调作用最强。miR-21的表达上调可以部分抵消乌索酸对HepG2细胞的抑制增殖及促进凋亡,部分抵消下调凋亡抑制基因Bcl-2、survivin表达和上调促凋亡基因Bax表达的作用。结果提示,乌索酸通过抑制miR-21的表达诱导肝癌HepG2细胞凋亡。  相似文献   
985.
目的分析云南省玉龙县纳西族居民心血管疾病危险因素聚集性的社会经济影响因素.方法采用分层随机抽样的方法抽取1 402名≥35岁的纳西族村民进行问卷调查和现场体检.结果该地村民超重、肥胖、中心性肥胖、吸烟、饮酒、心血管疾病家族史、高盐饮食、被动吸烟、生活压力、情绪低落和缺乏体力活动的检出率、高血压和糖尿病的患病率分别为26.0%、8.9%、39.5%、32.9%、24.5%、10.34%、27.4、21.8%、9.3%、5.2%、32.2%,26.2%和4.1%;仅有6.2%的纳西族居民无心血管疾病危险因素聚集性;男性具有3个及以上危险因素的比例大于女性(P<0.01);户主、文化程度越高者和综合社会经济地位越高者的纳西族居民的心血管疾病危险因素聚集度越低(P<0.05).结论云南省纳西族居民存在较高的心血管疾病危险因素聚集性.应重点加强低社会经济地位以及低受教育水平纳西族居民的心血管疾病的预防和干预工作.  相似文献   
986.
Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) emerged, in November 2002, as a novel agent causing severe respiratory illness. To study sequence variation in the SARS-CoV genome, we determined the nucleic acid sequence of the S and N genes directly from clinical specimens from 10 patients--1 specimen with no matched SARS-CoV isolate, from 2 patients; multiple specimens from 3 patients; and matched clinical-specimen/cell-culture-isolate pairs from 6 patients. We identified 3 nucleotide substitutions that were most likely due to natural variation and 2 substitutions that arose after cell-culture passage of the virus. These data demonstrate the overall stability of the S and N genes of SARS-CoV over 3 months during which a minimum of 4 generations for transmission events occurred. These findings are a part of the expanding investigation of the evolution of how this virus adapts to a new host.  相似文献   
987.
Allogeneic hematopoietic stem cell transplantation (allo-SCT) recipients are prone to infections. The incidences of mycobacterial infections after allo-SCT in several case series vary from less than 0.1-5.5%. However, no study has been published on tuberculosis following unrelated cord blood transplantation (UCBT). We retrospectively reviewed medical records of 113 adult patients with a median age of 54 years who underwent reduced-intensity UCBT (RI-UCBT) at Toranomon Hospital from March 2002 to May 2004. Mycobacterium tuberculosis infections were diagnosed in three patients (2.7%), of these two patients developed primary infection and one patient developed reactivation of latent tuberculosis. The interval between RI-UCBT and the diagnosis of tuberculosis was 34, 41 and 61 days. All the patients had disseminated disease at diagnosis. Histological examination showed the lack of granuloma in caseous necrosis. Combination antituberculous treatments showed limited efficacy, and two patients died immediately after diagnosis. M. tuberculosis caused life-threatening illness, rapidly progressing in RI-UCBT recipients. The lack of granuloma in caseous necrosis suggests the impaired T-cell function in early post transplant phase of RI-UCBT. We should consider M. tuberculosis in the differential diagnoses of fever of unknown source after RI-UCBT.  相似文献   
988.
OBJECTIVES: The present study was designed as a face-to-face functional comparison of human skeletal myoblasts (SMs) and CD133(+) bone marrow-derived hematopoietic progenitors in an animal model of semichronic myocardial infarction. BACKGROUND: Compared with SMs, bone marrow-derived cells have the advantage of plasticity and might more effectively regenerate ischemic cardiac tissue. However, few data exist on the comparative efficacy of these two cell types in semichronic infarcts. METHODS: A myocardial infarction was created by coronary ligation in 32 nude rats. Ten days later, rats received in-scar injections of human SMs, CD133(+) progenitors, or culture medium. Left ventricular function was assessed before and one month after transplantation by echocardiography and pressure-volume loops. Immunofluorescence, polymerase chain reaction, and in situ hybridization were used to detect cells grafted in the hearts. RESULTS: One month after transplantation, left ventricular ejection fraction decreased by 8 +/- 4% in controls, whereas it increased by 7 +/- 3% in CD133(+)-grafted hearts (p = 0.0015 vs. controls) and further by 15 +/- 5% in SM-treated hearts (p = 0.008 vs. controls). Systolic indices yielded by pressure-volume loops paralleled these data. Engrafted myotubes were identified in all SM-treated hearts by immunofluorescence, whereas in CD133(+)-grafted hearts, few human cells were only detected by polymerase chain reaction. CONCLUSIONS: In the setting of postinfarction scars, the transplantation of bone marrow-derived CD133(+) progenitors improves cardiac function, but this benefit is not superior to that afforded by myogenic cells.  相似文献   
989.
990.
We report the case of a 19-year-old woman who consulted for low-back pain 3 weeks after her first delivery. This young woman had a personal history of protein C deficiency and was treated daily during her pregnancy with low-molecular-weight heparin. Her body mass index was 34 and she only gained 10 kg during her pregnancy. Since the delivery - which occurred without any complication - she had suffered from a gradually increasing right-buttock pain and limp. Magnetic resonance imaging (MRI) revealed a fracture of the right sacral ala. After analgesia and 1 month of home relative bed rest, the patient recovered her functional capacities. Regarding our patient, who had no potential clinical risk factors for osteoporosis, the causal effect of heparin is thus possible but not certain. This case report illustrates the fact that clinicians should have a high suspicion of pelvic fracture in post-partum women, even in very young ones, presenting sudden onset of low back and pelvic pain, especially when they have received heparin during pregnancy. MRI seems to be the key exam because it is able to detect and stage fractures or microfractures.  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