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   105621篇
  免费   10763篇
  国内免费   3210篇
耳鼻咽喉   841篇
儿科学   1233篇
妇产科学   996篇
基础医学   12720篇
口腔科学   3747篇
临床医学   11275篇
内科学   10474篇
皮肤病学   1350篇
神经病学   6919篇
特种医学   3406篇
外国民族医学   12篇
外科学   7224篇
综合类   15633篇
现状与发展   8篇
一般理论   3篇
预防医学   17091篇
眼科学   1324篇
药学   14344篇
  115篇
中国医学   6207篇
肿瘤学   4672篇
  2024年   290篇
  2023年   1875篇
  2022年   2990篇
  2021年   5302篇
  2020年   5009篇
  2019年   4371篇
  2018年   3967篇
  2017年   4303篇
  2016年   4315篇
  2015年   4242篇
  2014年   7382篇
  2013年   7925篇
  2012年   7059篇
  2011年   7434篇
  2010年   5544篇
  2009年   5170篇
  2008年   4972篇
  2007年   4936篇
  2006年   4207篇
  2005年   3687篇
  2004年   3046篇
  2003年   2799篇
  2002年   2175篇
  2001年   2054篇
  2000年   1620篇
  1999年   1405篇
  1998年   1333篇
  1997年   1235篇
  1996年   1039篇
  1995年   957篇
  1994年   913篇
  1993年   720篇
  1992年   678篇
  1991年   582篇
  1990年   492篇
  1989年   497篇
  1988年   436篇
  1987年   389篇
  1986年   308篇
  1985年   401篇
  1984年   311篇
  1983年   187篇
  1982年   221篇
  1981年   177篇
  1980年   158篇
  1979年   121篇
  1978年   86篇
  1977年   56篇
  1976年   75篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A gene (DYT1) for susceptibility to early-onset torsion dystonia in Ashkenazi Jewish and Gentile kindreds is situated on chromosome 9q32-q34 in a 6–7 cM span between markers AK1 and ASS. To determine whether transmission of familial dystonia with myoclonic jerks responsive to alcohol was consistent with a gene in this region, we studied the 37 members of a Swedish family, of whom 20 were so affected. A lod score of < −2.00 from a two-point linkage analysis with six DNA markers covering a 30 cM span from D9S26 to D9S10 that included the region of the DYT gene indicated that this gene is not located in this region, and that two or more autosomal loci are responsible for hereditary dystonia in humans.  相似文献   
992.
儿童青少年心理健康量表的编制和信效度检验   总被引:7,自引:0,他引:7  
目的:编制一个用于儿童和青少年的心理健康量表,检验其信度和效度。方法:用新编的心理健康量表测查全国12个省(市)9278名儿童或他们的父母和143名异常样本,间隔5周的重测样本有87人,父母和儿童报告一致性检验样本56人,效标效度样本30人。用相关分析和因素分析考查量表的信度和效度。结果:新编量表的重测信度为0·713,Crobachα系数为0·847,分半信度为0·800,评定者信度为0·874;正常儿童在量表上的得分显著高于异常样本的得分(F=63·34-238·8,P<0·01);新编量表总分及分量表与儿童行为量表(CBCL)得分有一定的正或负的相关(r=0·27~0·609,P<0·05或0·01);探索性因素分析和验证性因素分析结果显示因素模式与量表编制者的理论构想一致。结论:儿少心理健康量表具有较好的信度和效度,可以用于儿童和青少年的心理健康评估。  相似文献   
993.
白塞氏病相关抗原的重组表达及抗原性初步分析   总被引:1,自引:0,他引:1  
目的:探讨Kinectin的抗原性,为下一步研究Kinectin在白塞氏病中的意义奠定基础。方法:从人Hep2细胞抽提RNA,利用RT—PCR扩增能覆盖Kinectin全长的3个片段,其位置分别相当于氨基酸22—510(kin—5),503-994(kin-M)和920-1346(kin-3)。将扩增的PCR片段克隆到pET42—a( )载体中,诱导表达的融合蛋白用白塞氏病病人血清进行Western blot分析。结果:构建的3个表达Kinectin部分片段载体(pET/kin—5、pET/kin-M和pET/Kin-3)具有正确的阅读框架,DNA测序符合率为99%,能在大肠杆菌中表达相应的肽段。8份阳性血清中,用Western blot分析发现,6份血清与kin-M反应,5份血清与kin-3反应,只有一份血清与kin-5有反应。结论:成功地构建表达覆盖Kinectin全长的3个载体,并初步发现Kinectin的抗原性可能主要位于其中间段和羧基端。  相似文献   
994.
During prenatal life, the ductus arteriosus connects the left pulmonary artery and the descending aorta. Morphometric features (length, external diameter, volume) of the ductus arteriosus in 131 human fetuses (65 males, 66 females) were studied by means of anatomical, digital and statistical methods. Regression analysis was used to investigate the growth of the ductus arteriosus during gestation. The values of the length of the ductus arteriosus ranged from 3.95 mm for the 15 week gestational group to 12.20 mm for the 34th week of gestation. The length of the ductus arteriosus related to fetal age (x) increased according to the linear function y = -3.0726 + 0.4381x. The mean values of the diameter of the ductus arteriosus ranged from 1.34 to 3.49mm for the 15 and 34 week gestational groups, respectively. The growth of the ductus arteriosus diameter followed in accordance with the linear function y = 0.2072 + 0.0935x. The mean values of the ductus arteriosus volume ranged from 5.08 mm3 for the 15 week group to 117.30 mm3 of the 34 week gestation group. The volume growth increased according to the function y = 0.0007x3.3782. Positive correlation coefficients between arterial parameters and fetal age were statistically significant (P < or = 0.01) and reached the following values: r1 = 0.98 for Length, r2 = 0.90 for diameter and r3 = 0.94 for volume. Despite the increase in absolute diameter, the relative diameter of the ductus arteriosus (ductus arteriosus-to-aortic bulb diameter ratio) decreased from 0.80 to 0.48.  相似文献   
995.
Congenital dysmorphic features are prevalent in schizophrenia and may reflect underlying neurodevelopmental abnormalities. A cluster analysis approach delineating patterns of dysmorphic features has been used in genetics to classify individuals into more etiologically homogeneous subgroups. In the present study, this approach was applied to schizophrenia, using a sample with a suspected genetic syndrome as a testable model. Subjects (n = 159) with schizophrenia or schizoaffective disorder were ascertained from chronic patient populations (random, n = 123) or referred with possible 22q11 deletion syndrome (referred, n = 36). All subjects were evaluated for presence or absence of 70 reliably assessed dysmorphic features, which were used in a three‐step cluster analysis. The analysis produced four major clusters with different patterns of dysmorphic features. Significant between–cluster differences were found for rates of 37 dysmorphic features (P < 0.05), median number of dysmorphic features (P = 0.0001), and validating features not used in the cluster analysis: mild mental retardation (P = 0.001) and congenital heart defects (P = 0.002). Two clusters (1 and 4) appeared to represent more developmental subgroups of schizophrenia with elevated rates of dysmorphic features and validating features. Cluster 1 (n = 27) comprised mostly referred subjects. Cluster 4 (n = 18) had a different pattern of dysmorphic features; one subject had a mosaic Turner syndrome variant. Two other clusters had lower rates and patterns of features consistent with those found in previous studies of schizophrenia. Delineating patterns of dysmorphic features may help identify subgroups that could represent neurodevelopmental forms of schizophrenia with more homogeneous origins. © 2001 Wiley‐Liss, Inc.  相似文献   
996.
We have developed a method for quantifying the complexity of activation patterns observed during ventricular fibrillation (VF) that is based on our previously reported methodology for decomposing epicardial mapping data into a set of isolated wavefronts. One-half second datasets are acquired from a 21×24 array of unipolar electrodes (1 mm spacing), and the wavefronts are isolated. A correlation technique is used to compute the similarity between all possible pairs of the isolated wavefronts. From these data, the wavefronts are sorted into clusters, each of which represents a recurring wavefront morphology. We define multiplicity (M) as the number of clusters needed to account for 90% of the total activations in the VF episode.M measures the complexity of the rhythm. In repetitive patterns (e.g., sinus rhythm),M=1, indicating that the same morphology repeatedly activates the mapped region. Typically, in VF,M>1, with larger numbers representing more complex, disorganized patterns. As an example, we computedM at 5, 10, 15, and 20 sec after electrical induction of VF in six pigs.M decreased significantly (p<0.001), suggesting increasing organization during this period.  相似文献   
997.
Mixed aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini.  相似文献   
998.
本文对30年前首次住院经CCMD-2再诊断的203例精神分裂症采用通径分析方法,进行了遗传流行病学对照研究。结果显示精神分裂症的发病与产次、性格、家族史有关。  相似文献   
999.
H1N2新亚型流感病毒神经氨酸酶基因来源的进一步研究   总被引:1,自引:0,他引:1  
对流感病毒H1N2亚型重组株A/哈防/1/88、A/哈防/12/92以及H3N2亚型病毒株A/雅防/2/87、A/京防/57/898和A/粤防/1/92神经氨酸酶(NA)基因核苷酸全序列的测定,进一步弄清了A/哈防/1/88病毒株的NA基因确来自当时人群中流行的H3N2亚型病毒株,很可能是来自A/雅防/2/87类病毒株;而A/哈防/12/92病毒株的NA基因可能是与A/哈防/1/88病毒株的NA基  相似文献   
1000.
The homeotic mutationspineless-aristapedia (ss a ) transforms the aristae into second tarsi. Flies with aSS a phenotype also show extremely positive geotaxis as measured in a Hirsch-type geotaxis maze. Other antennal mutants and flies with their aristae amputated do not show such extreme positive geotaxis. Deletion analysis has comapped the geotaxis effect withSS a in band 89C on the third chromosome. Finally, a biometrical analysis has detected additional genes on the X chromosome that also affects geotaxis.This work was supported by a Charles and Johanna Busch Memorial Award to T.R.M. and an Anne B. and James H. Leathem Scholarship Fund Award to P.A.M.Department of Biological Sciences and Bureau of Biological Research, Nelson Biological Laboratories  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