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   742篇
  免费   59篇
耳鼻咽喉   19篇
儿科学   20篇
妇产科学   11篇
基础医学   165篇
口腔科学   21篇
临床医学   62篇
内科学   100篇
皮肤病学   13篇
神经病学   21篇
特种医学   12篇
外科学   73篇
综合类   11篇
一般理论   1篇
预防医学   25篇
眼科学   9篇
药学   46篇
中国医学   2篇
肿瘤学   190篇
  2023年   11篇
  2022年   16篇
  2021年   25篇
  2020年   18篇
  2019年   19篇
  2018年   28篇
  2017年   23篇
  2016年   26篇
  2015年   27篇
  2014年   48篇
  2013年   51篇
  2012年   66篇
  2011年   55篇
  2010年   39篇
  2009年   35篇
  2008年   56篇
  2007年   38篇
  2006年   27篇
  2005年   34篇
  2004年   27篇
  2003年   23篇
  2002年   21篇
  2001年   8篇
  2000年   8篇
  1999年   14篇
  1998年   6篇
  1997年   2篇
  1996年   2篇
  1993年   4篇
  1992年   2篇
  1990年   5篇
  1989年   3篇
  1986年   1篇
  1985年   3篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   3篇
  1971年   4篇
  1969年   1篇
  1968年   2篇
  1966年   1篇
排序方式: 共有801条查询结果,搜索用时 0 毫秒
1.
BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease.  相似文献   
2.
Currently, antiretroviral therapy has become more affordable even in developing countries and it is being used in India. Fifteen HIV-1 infected individuals, who were on highly active antiretroviral therapy (HAART), were followed up for an average period of one year. The plasma viral load and CD4+ T cell estimation done at mean intervals of 5 months and 11 months after initiation of therapy showed a good response to therapy in 14 (93%) individuals.  相似文献   
3.
Breast masses due to benign disease and malignant tumors related to breast cancer differ in terms of shape, edge-sharpness, and texture characteristics. In this study, we evaluate a set of 22 features including 5 shape factors, 3 edge-sharpness measures, and 14 texture features computed from 111 regions in mammograms, with 46 regions related to malignant tumors and 65 to benign masses. Feature selection is performed by a genetic algorithm based on several criteria, such as alignment of the kernel with the target function, class separability, and normalized distance. Fisher's linear discriminant analysis, the support vector machine (SVM), and our strict two-surface proximal (S2SP) classifier, as well as their corresponding kernel-based nonlinear versions, are used in the classification task with the selected features. The nonlinear classification performance of kernel Fisher's discriminant analysis, SVM, and S2SP, with the Gaussian kernel, reached 0.95 in terms of the area under the receiver operating characteristics curve. The results indicate that improvement in classification accuracy may be gained by using selected combinations of shape, edge-sharpness, and texture features.  相似文献   
4.
The 16-kDa cytosolic antigen of M. tuberculosis was purified to homogeneity by molecular sieving chromatography, and the diagnostic potential of the antigen was evaluated in various categories of patients by enzyme-linked immunosorbent assay (ELISA). The immunoglobulin G (IgG), IgA, and IgM antibody levels to 16-kDa antigen were estimated in the two polar groups, namely, smear- and culture-positive pulmonary tuberculosis (S+C+) patients and healthy subjects (HS). Sensitivities of 62, 52 and 11% with specificities of 100, 97, and 95% were obtained for the three isotypes, respectively. The total number of positives by a combination of the three isotypes was analyzed in the polar groups, and the sensitivity improved to 83% with a specificity of 93%. Even when a combination of IgG and IgA alone was considered, the sensitivity was 82% with a specificity of 97%. Polyethylene glycol precipitation of the circulating immune complex (CIC) in sera was carried out. The CIC-bound antibodies to 16-kDa antigen were assessed by ELISA in the S+C+, SC+, and SC categories of patients. Measuring the IgG-IgA-IgM combination positivities of the CIC-bound antibodies gave sensitivities of 97.5, 100, and 45.3%, respectively. The specificity of the assay with these combinations was maintained at 95.4%.  相似文献   
5.
Reports about the effects of ascorbate (vitamin C) on cultured cells are confusing and conflicting. Some authors show inhibition of cell death by ascorbate, whereas others demonstrate that ascorbate is cytotoxic. In this report, using three different cell types and two different culture media (Dulbecco's modified Eagle's medium and RPMI 1640), we show that the toxicity of ascorbate is due to ascorbate-mediated production of H2O2, to an extent that varies with the medium used to culture the cells. For example, 1 mM ascorbate generates 161 +/- 39 microM H2O2 in Dulbecco's modified Eagle's medium and induces apoptosis in 50% of HL60 cells, whereas in RPMI 1640 only 83 +/- 17 microM H2O2 is produced and no apoptosis is detected. Apoptosis is prevented by catalase, and direct addition of H2O2 at the above concentration to the cells has similar effects to ascorbate. These results show that ascorbate itself is not toxic to the cell lines used and that effects of ascorbate in vivo cannot be predicted from studies on cultured cells. The ability of ascorbate to interact with different cell culture media to produce H2O2 at different rates could account for many or all of the conflicting results obtained using ascorbate in cultured cell assays.  相似文献   
6.
The low density lipoprotein receptor (LDLR) is an attractive candidate gene for genetic association with Alzheimer's disease (AD) because: (i) the LDLR is an apolipoprotein E (apoE) receptor, alleles of which have been associated with AD, (ii) LDLR resides at chromosome 19p13.3 within a region linked to AD, and (iii) LDLR modulates the homeostasis of cholesterol, which itself appears associated with AD. Therefore, we evaluated whether LDLR haplotypes alter the odds of AD by performing an association study examining three LDLR single nucleotide polymorphisms (SNPs) in 118 AD patients and 133 non-AD subjects. LDLR genotypes were obtained by TaqMan allelic discrimination assays. Although individual LDLR SNPs were not associated with AD, analyses of unambiguous haplotypes suggested the hypothesis that the 211 LDLR haplotype was associated with reduced odds of AD. We then evaluated this hypothesis in a second study cohort, i.e., the Religious Orders Study. These results supported the hypothesis that the 211 LDLR haplotype is associated with reduced odds of AD. Moreover, these data suggested further associations between LDLR variants and AD. Thus, LDLR variants appear significantly associated with AD and merit additional study.  相似文献   
7.
8.

Background  

CD4+ T lymphocyte (CD4) cell count testing is the standard method for determining eligibility for antiretroviral therapy (ART), but is not widely available in sub-Saharan Africa. Total lymphocyte counts (TLCs) have not proven sufficiently accurate in identifying subjects with low CD4 counts. We developed clinical algorithms using TLCs, hemoglobin (Hb), and body mass index (BMI) to identify patients who require ART.  相似文献   
9.

Background  

This study was undertaken to investigation the effect of Diasulin, a poly herbal drug composed of ethanolic extract of ten medicinal plants on blood glucose, plasma insulin, tissue lipid profile, and lipidperoxidation in alloxan induced diabetes.  相似文献   
10.
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