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   104462篇
  免费   10410篇
  国内免费   3204篇
耳鼻咽喉   866篇
儿科学   1198篇
妇产科学   1079篇
基础医学   12158篇
口腔科学   3682篇
临床医学   10737篇
内科学   11041篇
皮肤病学   1305篇
神经病学   6643篇
特种医学   3224篇
外国民族医学   11篇
外科学   7603篇
综合类   15146篇
现状与发展   8篇
一般理论   3篇
预防医学   16709篇
眼科学   1213篇
药学   13795篇
  114篇
中国医学   5770篇
肿瘤学   5771篇
  2024年   356篇
  2023年   1866篇
  2022年   3712篇
  2021年   5161篇
  2020年   4922篇
  2019年   4285篇
  2018年   3916篇
  2017年   4141篇
  2016年   4183篇
  2015年   4139篇
  2014年   7290篇
  2013年   7762篇
  2012年   6953篇
  2011年   7305篇
  2010年   5443篇
  2009年   5112篇
  2008年   4921篇
  2007年   4851篇
  2006年   4128篇
  2005年   3598篇
  2004年   2978篇
  2003年   2732篇
  2002年   2128篇
  2001年   2014篇
  2000年   1599篇
  1999年   1385篇
  1998年   1330篇
  1997年   1202篇
  1996年   1038篇
  1995年   934篇
  1994年   902篇
  1993年   689篇
  1992年   660篇
  1991年   551篇
  1990年   479篇
  1989年   489篇
  1988年   423篇
  1987年   375篇
  1986年   288篇
  1985年   385篇
  1984年   300篇
  1983年   178篇
  1982年   205篇
  1981年   158篇
  1980年   161篇
  1979年   116篇
  1978年   79篇
  1977年   51篇
  1976年   74篇
  1974年   41篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Liu JH  Okazaki K  Mweene A  Shi WM  Wu QM  Su JL  Zhang GZ  Bai GR  Kida H 《Virus genes》2004,29(3):329-334
The hemagglutinin (HA) genes of 12 H9N2 influenza virus strains isolated from chickens in Mainland China during the period 1995–2002 were genetically analyzed. All the isolates possessed the same amino acid motif -R-S-S-R/G-L- at the cleavage site of HA. Except for the conserved amino acids, as is the case in the other avian influenza viruses, located in the receptor binding site, all of the 12 isolates possessed N at amino acid position 183; A, T, or V at position 190; K at position 137, whereas the representative strains of the other lineage (except Dk/HK/Y280/97-like lineage) virus of H9N2 viruses had H, E, and R at these positions respectively. These could be considered as the partial molecular markers of the H9 viruses isolated from chickens in Mainland China. Phylogenetic analyses showed HA genes of these isolates belonged to that of A/duck/Hong Kong/Y280/97-like virus lineage. No A/quail/Hong Kong/Gl/97-like virus was found in chicken, population since the outbreak of H9N2 influenza in Mainland China in 1992. The available evidence indicates that HA genes of H9 influenza virus circulating in Mainland China during the past years were well conserved.  相似文献   
992.
We have identified a novel missense transition (362G→A) in exon 3 of the COL4A5 gene in a male patient with late-onset Alport syndrome. We used non-isotopic single strand conformation polymorphism, heteroduplex analysis, and automated DNA sequencing. The mutation changes a conserved glycine at codon 54 for an aspartic acid (Gly54Asp), which abolishes a BstNI site. Using restriction analysis, we identified the heterozygous carrier status in the two daughters of the proband. Our findings are in keeping with the hypothesis that slower progressive forms of Alport syndrome are more often associated with missense mutations rather than large deletions or frameshifts. This is the first mutation described in the N-terminus triple helical 7S domain of the COL4A5 gene in an Alport syndrome patient.  相似文献   
993.
A. Linder    K. Strandberg  H. Deuschl 《Allergy》1987,42(2):126-134
The prerequisites for using the assayed histamine concentration in nasal secretion as an objective measure of disease activity in allergic rhinitis were investigated. It was demonstrated that in histamine determination procedures the presence of quenching substances in the nasal secretion could lead to underestimation of the histamine concentration. This bias was eliminated in a modified spectrofluorometric assay. Only an insignificant fraction of the histamine in samples collected by nasal spray washing was bound to unfiltrable particles or cells. The mean histamine concentration in nasal secretions from 15 healthy subjects was 11.2 micrograms/ml and in a group of nine patients with allergic rhinitis out of season 3.36 micrograms/ml. The histamine concentration in the latter group decreased during the pollen season and after positive allergen challenge. It is suggested that this decrease is caused by the increase in volume of the secretion during the allergic response. The use of lithium as an exogenous marker permitted quantitation of the increase in the relative amount of nasal secretion recovered by washing in the symptomatic subjects.  相似文献   
994.
995.
Xia J  Deng H  Feng Y  Zhang H  Pan Q  Dai H  Long Z  Tang B  Deng H  Chen Y  Zhang R  Zheng D  He Y  Xia K 《Journal of human genetics》2002,47(12):0635-0640
 Hearing impairment is an extremely heterogeneous disorder. A total of 35 loci and 17 related genes for autosomal dominant nonsyndromic hearing loss have been identified. In a Chinese pedigree characterized by autosomal dominant inheritance with bilateral, postlingual, progressive, and sensorineural nonsyndromic hearing impairment, the putative disease gene locus was localized to chromosome 5q31.1-32 by a genome-wide scan. Fine mapping indicated that the disease gene was located within an 8.8-cM region between markers D5S2056 and D5S638, with a maximum two-point logarithm of differences (LOD) score of 6.89 (θ = 0) at D5S2017. By the candidate gene approach, mutation screening of the DIAPH1 and POU4F3 genes at 5q31 was performed. No mutation was found, suggesting that this is a novel deafness locus, which has been named DFNA42. Received: May 8, 2002 / Accepted: October 1, 2002  相似文献   
996.
Antimicrobial resistance profiles, restriction fragment length polymorphism of the coagulase gene and repetitive element sequence-based PCR were used to classify 210 methicillin-resistant Staphylococcus aureus isolates recovered between 1997 and 2005 in two hospitals in Vigo, north-west Spain. Representative isolates belonging to the epidemic clones were analysed by spa typing and multilocus sequence typing, and the staphylococcal chromosomal cassette (SCC)mec type was determined for all isolates. The New York/Japan clone (t002-ST5-II) was detected in Spain for the first time. However, the New York/Japan and the Brazilian (t037-ST239-IIIA) clones were replaced by EMRSA-16 (t018-ST36-II), which at present is the predominant clone.  相似文献   
997.
大学生就业效能量表的编制   总被引:1,自引:0,他引:1  
目的编制适用于我国大学生的就业的效能量表。方法在深入访谈和文献综述的基础上,编制出大学生就业效能量表,运用探索性和验证性因素分析技术对568名全日制在校本科生的就业效能的内在结构进行了探讨。结果大学生就业效能主要有3个因素组成:个性自我了解、就业信息与技能和就业应对信心,问卷的各项测量指标良好。结论本问卷可以作为测量大学生就业效能的工具。  相似文献   
998.
Background: Investigation of haplotype/allele frequency data of Y-STR loci in ethnically diverse populations is essential for forensic reference database construction and genetic application. However, the population genetic characteristics of the Chinese Miao minority from Guizhou Province remain uncharacterised.

Aim: To assess forensic characteristics for 23 Y-Chromosomal STR loci in Guizhou Miao and explore population genetic relationships with geographically neighbouring populations.

Subjects and methods: Twenty-three Y-Chromosomal STRs were genotyped using the Powerplex® Y23 system in 103 unrelated Chinese Miao males from Guizhou Province, southwest China. Haplotypes and forensic parameters were obtained. Population relationships of Guizhou Miao with others were revealed using AMOVA and an MDS plot.

Results: A total of 96 haplotypes were identified with overall haplotype diversity (HD) and discrimination capacity (DC) of 0.9985 and 0.9320, respectively. Genetic differentiation was observed with most of the comparison populations, prominently for Guizhou Shui.

Conclusion: The 23 Y-STR loci were highly polymorphic and discriminating in the Guizhou Miao population and could be used for forensic practice and population genetic studies. Population relationship analysis revealed Guizhou Miao had a close genetic relationship with geographically close Guizhou Gelao, as well as Han majorities derived from different regions.  相似文献   

999.
Despite extensive genomic scans, linkage studies of multiplex pedigrees have been unable to produce replicable evidence of genes predisposing to schizophrenia. This indicates that it is unlikely that a single gene accounts for a majority of cases of schizophrenia, even in multiplex pedigrees. It is most likely that schizophrenia is caused by the nonlinear interaction of multiple genetic and environmental factors influencing brain development and function. This conclusion has strong implications for the design of linkage and association studies. Recently designed linkage studies involve several improvements to deal with extensive locus heterogeneity and multiplicative interaction. These improvements include much larger samples of pedigrees, systematic ascertainment and sequential extension rules, and standardized procedures at multiple sites to facilitate collaboration and replication. Future improvements are likely to require advances in the assessment of clinical and neurobiological variability in multiplex pedigrees, more systematic environmental assessment, and advances in analytic methods to deal with multiplicative interaction. Rather than focusing only on schizophrenia as one or more discrete disorders, future linkage efforts should also consider the etiology of individual clinical syndromes or dimensional components of risk that interact to cause the complex pattern of syndromal comorbidity observed within schizophrenics and their families. © 1994 Wiley-Liss, Inc.  相似文献   
1000.
Ectodermal dysplasias (EDs) are developmental disorders affecting tissues of ectodermal origin including hair, nails, teeth and sweat glands. Ectodermal dysplasia of hair, nails and teeth is a rare type of congenital disorder characterized by sparse and thin hair, dystrophic finger-and toenails and missing and abnormal teeth. In an effort to understand the molecular basis of this form of ED a family of Pakistani origin with an autosomal recessive pattern of inheritance was ascertained from a remote region in Pakistan. The clinical features of the affected individuals included thin and fine hair on the scalp, dystrophic and flat nails, absent or sparse eyebrows and eyelashes, missing and abnormal teeth, and thin body hair. A human genome scan carried out using microsatellite markers mapped the disease locus in this family to chromosome 18q22.1–18q22.3. A maximum two-point LOD score of 2.73 (θ= 0.0) was obtained at marker D18S541. Multipoint linkage analysis resulted in a maximum LOD score of 3.42 obtained with several markers, including D18S1125, ATA82B02, D18S848, D18S488, D18S1091, and D18S485, which supported the linkage. The linkage interval is flanked by markers D18S857 and D18S815, which corresponds to a region of 17.32 cM according to Rutgers combined linkage and physical map (build 36). This region covers 8.63 Mb according to the sequence-based physical map. Three candidate genes, CDH7, CDH19 and ZNF407 , from the linkage interval were sequenced and found to be negative for functional sequence variants. This study is the first step towards the identification of a gene involved in hair, nails and teeth type ED.  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