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   13589篇
  免费   1132篇
  国内免费   19篇
耳鼻咽喉   85篇
儿科学   442篇
妇产科学   414篇
基础医学   1750篇
口腔科学   413篇
临床医学   2167篇
内科学   2450篇
皮肤病学   225篇
神经病学   965篇
特种医学   337篇
外科学   1580篇
综合类   193篇
一般理论   14篇
预防医学   1715篇
眼科学   221篇
药学   911篇
  1篇
中国医学   11篇
肿瘤学   846篇
  2023年   76篇
  2022年   121篇
  2021年   230篇
  2020年   150篇
  2019年   239篇
  2018年   266篇
  2017年   218篇
  2016年   235篇
  2015年   235篇
  2014年   362篇
  2013年   555篇
  2012年   738篇
  2011年   842篇
  2010年   453篇
  2009年   375篇
  2008年   744篇
  2007年   777篇
  2006年   786篇
  2005年   744篇
  2004年   681篇
  2003年   658篇
  2002年   662篇
  2001年   271篇
  2000年   277篇
  1999年   308篇
  1998年   155篇
  1997年   162篇
  1996年   141篇
  1995年   109篇
  1994年   86篇
  1993年   111篇
  1992年   223篇
  1991年   183篇
  1990年   177篇
  1989年   149篇
  1988年   173篇
  1987年   137篇
  1986年   138篇
  1985年   159篇
  1984年   125篇
  1983年   102篇
  1982年   95篇
  1981年   88篇
  1980年   66篇
  1979年   86篇
  1978年   78篇
  1977年   71篇
  1974年   83篇
  1973年   79篇
  1971年   63篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Oligosaccharides were made from Haemophilus influenzae type b capsular polysaccharide and conjugated to CRM197 by reductive amination. Conjugates were made with a range of lengths and multiplicities of saccharide chains. All elicited a strongly enhanced anti-H. influenzae type b capsular polysaccharide response when injected into weanling rabbits. One series of conjugates also elicited antibodies to diphtheria toxin.  相似文献   
82.
BACKGROUND: Although diurnal variation of mood is a widely recognized symptom of depression, the clinical, neurobiological and psychopharmacological significance of this symptom has not previously been reported. METHOD: A total of 195 depressed out-patients underwent a detailed clinical and neurobiological assessment, and were then randomized to treatment with either fluoxetine or nortriptyline. RESULTS: Of the 195 depressed patients, 62 had a pattern of reversed diurnal variation (i.e. worse in the evening). Those with reversed diurnal variation had a poorer response to a serotonergic anti-depressant, were less likely to have bipolar II disorder, had a higher tryptophan: large neutral amino acid ratio and had different allele frequencies of the polymorphisms in the promoter region of the serotonin transporter. CONCLUSIONS: These findings raise the possibility of serotonergic influence on diurnal variation, and that the symptom of reversed diurnal variation is of relevance to antidepressant prescribing.  相似文献   
83.
P J Davis  S H Parry    P Porter 《Immunology》1978,34(5):879-888
The serological and secretory immune responses of the chicken to infection with Eimeria tenella were evaluated in terms of various anti-coccidial activities. Serological responses were detected in the forms of precipitating, sporozoite neutralizing, anti-merozoite and anti-schizont antibodies. Similarly, anti-schizont and sporozoite neutralizing activities were found in caecal contents (containing mainly IgA) from infected birds and these also had the capacity to damage second generation merozoites. Moreover, the functional importance of IgA could be implied from the substantial predominance of IgA synthesizing cells in the intestinal immunocyte response as revealed by immunohistology. This was reflected in the immunoglobulin profile of caecal contents, for primary and secondary infection resulted in elevated levels of IgA whilst IgG and IgM generally remained extremely low or were usually undetectable. Taken with the well established lack of correlation between serum antibody and protection, these results suggest that the intestinal secretory IgA system plays an essential role in the protective immune response to E. tenella.  相似文献   
84.
85.
Comparisons of five morphological characters, 12 enzyme electrophoresis profiles, and Wolbachia pipientis infection rates were used to characterize populations of members of the Culex pipiens L. complex in California and South Africa. In South Africa, male phallosome DV/D ratio, male maxillary palp index, branching of siphonal seta 1a, the enzyme locus Mdhp-1, and W. pipientis infection rates proved highly diagnostic for separating Culex quinquefasciatus from Cx. pipiens phenotypes. In Johannesburg, where sympatric members of the Cx. pipiens complex were analyzed as one population, a significant Wahlund Effect was observed in the enzyme loci such as Ao, 6-Pgdh, Mdh-2, and Pgm. In California, all populations of the Cx. pipiens complex were in Hardy Weinberg equilibrium at all polymorphic enzyme loci examined. Additionally, in California, all populations had similar W. pipientis infection rates and appeared morphologically identical (except for DV/D ratio, in extreme north and south). These findings indicate that in South Africa, Cx. pipiens and Cx. quinquefasciatus remain as genetically distinct populations and behave as separate species. Conversely, in California, there is considerable genetic introgression between Cx. pipiens and Cx. quinquefasciatus, and they behave as a single species.  相似文献   
86.
The case of a retarded child with trisomy of the short arm of chromosome 8 associated with translocation between the short arm of chromosome 8 and the long arm of chromosome 22 is reported. Balanced translocation involving the same chromosomes was present in the mother and brother of the propositus. The specific chromosomes involved in the abnormality in this family were identified by use of fluorescence microscopy with quinacrine mustard staining, autoradiography and Giemsa banding. This appears to be the first case report of this anomaly, although trisomy of the short arm of chromosome 9 has been reported previously.  相似文献   
87.
88.
89.
OBJECTIVES: To examine factors influencing the rate of transmitted drug resistance (TDR) among seroconverters, with particular emphasis on 3 widely used genotypic drug resistance algorithms. METHODS: The study used data from CASCADE (Concerted Action on Seroconversion to AIDS and Death in Europe), a collaboration of seroconverter cohorts in Europe and Canada. Genotypic resistance data were derived within 18 months of the last seronegative test or date of laboratory evidence of acute infection and before the initiation of antiretroviral therapy. The Stanford algorithm was used to analyze each individual's nucleotide sequence. A multivariate logistic model was used to assess independent relationships between the presence of TDR and exposure category, sex, age at seroconversion, and year of seroconversion. The paper also describes 3 alternative definitions of resistance: the Stanford algorithm, the key resistance mutations defined by the International AIDS Society, and the Agence Nationale de Recherches sur le Sida (ANRS) algorithm. RESULTS: Forty-five of 438 patients (10.3%) seroconverting between 1987 and 2003 were infected with a drug-resistant HIV-1 variant. Forty patients (9.1%) showed resistance mutations to only 1 class of antiretroviral drugs, 2 (0.5%) to 2 classes, and 3 (0.7%) to 3 classes of antiretroviral therapy. It was suggested that individuals seroconverting later in calendar time were more likely to have TDR (relative risk 3.89 and 95% CI: 0.84 to 18.02, and relative risk 4.69 and 95% CI: 1.03 to 21.31, for 1996-1999 and 2000-2003, respectively, compared with pre-1996; P trend = 0.08). This trend was apparent regardless of the definition of TDR used. The total estimated proportion of individuals with TDR varied between 10.3% and 15.5% according to which definition was used. CONCLUSIONS: Evidence was found for the rise of TDR over time. A specific definition of what constitutes TDR rather than a simple list of mutations is needed.  相似文献   
90.
The T-cell receptor β locus (TCRB) on chromosome 7q35 was studied as a candidate region for genetic susceptibility to type 1 insulin-dependent diabetes (IDDM). A highly polymorphic microsatellite marker mapping to the TCRBV6.7 gene and a TCRB C-region RFLP were used to genotype the members of a total of 21 multiplex IDDM families from two different geographical areas. There was no evidence to support linkage to either of these markers with IDDM, and conventional two-point analysis excluded linkage to the telomeric end of the TCRB complex, in the region of the highly informative TCRBV6.7 marker. There was significant linkage of IDDM to the class II HLA-D locus with significant lod scores >3.0 obtained for the HLA-DRB1 and HLA-DQB1 genes. Affected sib-pair (ASP) and transmission disequilibrium (TDT) association tests confirmed these findings.  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