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   4487篇
  免费   285篇
  国内免费   20篇
耳鼻咽喉   25篇
儿科学   183篇
妇产科学   62篇
基础医学   569篇
口腔科学   234篇
临床医学   464篇
内科学   909篇
皮肤病学   64篇
神经病学   330篇
特种医学   202篇
外科学   583篇
综合类   152篇
一般理论   3篇
预防医学   341篇
眼科学   36篇
药学   306篇
中国医学   1篇
肿瘤学   328篇
  2022年   29篇
  2021年   53篇
  2020年   49篇
  2019年   63篇
  2018年   63篇
  2017年   65篇
  2016年   72篇
  2015年   80篇
  2014年   133篇
  2013年   180篇
  2012年   270篇
  2011年   244篇
  2010年   134篇
  2009年   149篇
  2008年   195篇
  2007年   181篇
  2006年   200篇
  2005年   188篇
  2004年   173篇
  2003年   147篇
  2002年   123篇
  2001年   144篇
  2000年   118篇
  1999年   132篇
  1998年   89篇
  1997年   77篇
  1996年   79篇
  1995年   50篇
  1994年   66篇
  1993年   40篇
  1992年   107篇
  1991年   66篇
  1990年   69篇
  1989年   77篇
  1988年   71篇
  1987年   103篇
  1986年   67篇
  1985年   71篇
  1984年   41篇
  1983年   48篇
  1982年   43篇
  1981年   23篇
  1980年   33篇
  1979年   45篇
  1978年   33篇
  1977年   33篇
  1976年   27篇
  1975年   35篇
  1974年   36篇
  1973年   27篇
排序方式: 共有4792条查询结果,搜索用时 15 毫秒
41.
Using intact ethanol-fixed cytokeratin monoclonal (CAM 5.2) and propidium iodide dual-stained cells, we have performed two-color multiparametric flow cytometric (FCM) DNA analysis and S-phase fraction (SPF) determination on 165 mechanically dissociated breast carcinomas. Sixty-seven patients were axillary node positive, 33 patients node negative; 59 had biopsy only and in 8, FCM was performed on tissue from metastatic lesions. Overall, 62% of the tumors contained aneuploid cell populations. Abnormal cellular DNA content (aneuploidy) was significantly correlated with high nuclear grade (p less than 0.001), lack of estrogen receptors (p less than 0.001), presence of vascular invasion (p less than 0.04), high histologic grade (p less than 0.04), and tumor size (p less than 0.03) but not with patient age (p greater than 0.07) or axillary node status (p greater than 0.50). SPF values derived from ungated histograms had a positively skewed frequency distribution (range 2 to 30%, N = 152) with an overall median of 11% (diploid, 8.9%; aneuploid, 15.7%). Higher SPF values were significantly correlated with aneuploidy (p less than 0.001), presence of necrosis (p less than 0.001), lack of estrogen receptor (p less than 0.0001), high nuclear grade (p less than 0.001), vascular invasion (p less than 0.003), tumor size (p less than 0.006), and high histologic grade (p less than .004) but not the presence of lymph node metastases (p greater than 0.56). Mean SPF values were significantly higher when calculated from cytokeratin gated DNA histograms (14.1% versus 11.5%, p less than 0.001), probably due to exclusion of contaminating stromal/inflammatory cells; and significantly lower when calculated from debris subtracted histograms (7.8% versus 11.4%). Cytokeratin gated and debris subtracted SPF values both had a greater degree of correlation than ungated values with clinicopathologic factors of known prognostic significance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
42.
Several reports suggest that the glutathione-S-transferase (GST) family of enzymes is involved in a variety of cancers, due to their carcinogen-detoxification properties. A polymorphism in codon 105 of the pi variant (GSTP1 I105V), which affects the enzymatic activity of the enzyme, has been linked to the incidence of cancers from different organs. However, the published data in prostate cancer (PCa) is controversial. Some studies report an association with the GSTP1 I105V polymorphism and sporadic PCa, whereas other studies report no association. Recently, one study showed a positive correlation between the GSTP1 I105V polymorphism and familial PCa in a Japanese population. In the present study, we assessed the correlation of the GSTP1 I105V polymorphism with familial and sporadic PCa in an American population. We analyzed DNA samples from 438 patients with familial PCa, 499 patients with sporadic PCa, and 510 controls. We found no significant association between the GSTP1 I105V polymorphism and familial or sporadic PCa when compared to the control group [odds ratio (OR) =1.0 (0.74-1.37); P=0.58]. Moreover, no association was found after stratification for age of diagnosis, Gleason grade, or lymph node involvement [OR =0.84 (0.65-1.09), P=0.37]. These data indicate that there is no associated risk for sporadic or familial PCa in American families containing the GSTP1 I105V polymorphism.  相似文献   
43.
Cytogenetic studies of an infant with malformations and a peculiar appearance showed a partial trisomy of chromosome 12. The mother carried a translocation of the distal part of chromosome 12 onto the short arm of chromosome 21, with breakpoints most likely at 12q24 and 21p11.  相似文献   
44.
We have reported associations between human leukocyte antigen (HLA) homozygosity and low measles antibody levels after one dose of the measles, mumps, and rubella (MMR) vaccine. Here, we examined associations between HLA homozygosity and immune responses to MMR after two doses of vaccine. We examined associations between HLA homozygosity and measles antibody levels in a group of 178 children (cohort 1) as well as associations between homozygosity and antibody levels and lymphoproliferative responses to MMR in 346 children (cohort 2). In cohort 1, HLA homozygotes and heterozygotes had similar increases in measles antibody levels after a second dose of measles vaccine. In cohort 2, HLA homozygosity was not associated with measles immune measures after two doses of vaccine. Homozygosity at the DPB locus was associated with increased rubella antibody levels, and homozygosity at the class IA alleles was associated with lower mumps lymphoproliferative response. Homozygosity at increasing numbers of loci was also associated with lower mumps antibody levels and lymphoproliferative response. Therefore, two doses of the MMR vaccine appear to induce sufficient antibody levels and lymphoproliferative responses against measles and rubella, regardless of HLA homozygosity status. However, children who are HLA homozygous may be less protected against mumps compared with children who are heterozygous.  相似文献   
45.
46.
Familial nocturnal cramping   总被引:1,自引:0,他引:1  
  相似文献   
47.
In a sample of 5483 adults who had been legally adopted early in life by persons not biologically related to them, 33 were identified, from mental hospital records, for whom a diagnosis of definite schizophrenia (chronic, latent, or acute) could be agreed upon by four raters. An equal number of matched controls were selected from the sample of adopted individuals who had never been admitted to a mental hospital. Ninety percent of the living parents, siblings, and half-siblings, biological and adoptive, cooperated in an extensive psychiatric interview permitting a consensus diagnosis by three blind raters. Schizophrenia and uncertain schizophrenia were found to be significantly concentrated in the population genetically related to the schiziphrenic adoptees. Their adoptive relatives did not differ from the control populations in the prevalence of schizophrenic illness.This was presented at the Annual Meeting of the American Society of Human Genetics, Portland. Oregon, October 18, 1974.  相似文献   
48.
The intercalated islands are intra-amigdaloid clusters of D1 receptor rich GABAergic neurons, which control impulse traffic between the basolateral complex and the central nucleus of the amygdala. As dopaminergic transmission within the amygdala may play a role in anxiety, the effect of the D1 antagonist SCH23390 microinjected mainly close to the rostral intercalated islands in rats was studied, using the White and Black Box test. SCH23390 reduced anxiety by an increase in the latency of the first entry into the black compartment and by an increase in the total time spent in the white compartment of the White and Black Box test, while there was no significant modification of locomotion. It is suggested that blockade of D1 receptors in the rostral intercalated islands may reduce anxiety through a reduction of GABA-mediated dishinibition of the central amygdaloid nucleus.  相似文献   
49.
50.
BACKGROUND: IgE is a major determinant of allergic disease. Twin analysis of serum levels of IgE has been carried out previously in children and adults with heritability estimates of 30% to 70% on the basis of ANOVA. OBJECTIVE: This study included the analysis of serum IgE in a population of 126 twins, 27 monozygotic pairs and 36 dizygotic pairs, studied at birth (cord blood [CB] IgE) and consecutively at the age of 6 to 9 years of age (serum IgE). METHODS: IgE was determined by means of RIA. ANOVA, correlation analysis, and structural equation modeling by maximal likelihood analysis was used for genetic analysis. RESULTS: Structural equation modeling by maximal likelihood analysis showed the best-fitting model to be the AE model (A for additive genetic variance and E for environmental variance) both at birth and later in childhood. The estimated heritability was 0.92 (95% CI, 0.84-0.95) for CB IgE and 0.78 (95% CI, 0.60-0.87) for serum IgE. The correlation between CB IgE and serum IgE was 0.04. CONCLUSIONS: The study demonstrated a higher genetic dependency of serum IgE than previously recognized. The low correlation between the IgE levels at birth and later in childhood suggested that different effector mechanisms may be operating at different ages.  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