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   13263篇
  免费   1109篇
  国内免费   34篇
耳鼻咽喉   187篇
儿科学   471篇
妇产科学   355篇
基础医学   1712篇
口腔科学   168篇
临床医学   2142篇
内科学   2470篇
皮肤病学   116篇
神经病学   1270篇
特种医学   373篇
外科学   1374篇
综合类   211篇
一般理论   11篇
预防医学   1573篇
眼科学   198篇
药学   911篇
中国医学   16篇
肿瘤学   848篇
  2022年   60篇
  2021年   170篇
  2020年   140篇
  2019年   191篇
  2018年   212篇
  2017年   190篇
  2016年   190篇
  2015年   238篇
  2014年   344篇
  2013年   507篇
  2012年   731篇
  2011年   787篇
  2010年   461篇
  2009年   386篇
  2008年   738篇
  2007年   770篇
  2006年   799篇
  2005年   808篇
  2004年   731篇
  2003年   768篇
  2002年   754篇
  2001年   322篇
  2000年   320篇
  1999年   271篇
  1998年   186篇
  1997年   153篇
  1996年   139篇
  1995年   114篇
  1994年   108篇
  1993年   119篇
  1992年   210篇
  1991年   184篇
  1990年   191篇
  1989年   173篇
  1988年   161篇
  1987年   150篇
  1986年   126篇
  1985年   137篇
  1984年   108篇
  1983年   102篇
  1982年   61篇
  1981年   84篇
  1980年   60篇
  1979年   85篇
  1978年   82篇
  1977年   62篇
  1976年   57篇
  1974年   60篇
  1973年   93篇
  1972年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
BACKGROUND: A single nucleotide polymorphism in the tumor necrosis factor type II receptor (TNFRII) gene, codon 196, results in the substitution of arginine (R allele) for methionine (M allele). The 196R allele is reportedly associated with an increased susceptibility to autoimmune disease, and donor 196R allele carriage correlates with increased severity of acute graft-versus-host disease (GVHD) after matched unrelated bone marrow transplantation (BMT). METHODS: We investigated the impact of donor and recipient TNFRII genotype on GVHD incidence and severity among 104 adult recipients of myeloablative sibling BMTs. RESULTS: 196R allele frequency was 0.28 among recipients, donors, and controls. There was an increased incidence of acute GVHD among 196R-positive recipients (odds ratio [OR] 3.6, P=0.05). This association was confirmed in multivariate analysis (relative risk 4, P=0.04), correcting for previously established clinical and genetic risk factors. Donor 196R homozygosity was associated with an increased incidence of extensive chronic GVHD (OR 18.5, P=0.02). This association was also confirmed in multivariate analysis (OR 11, P=0.02). To investigate the functional impact of the TNFRII 196 M/R polymorphism, 79 volunteer blood donors were genotyped at this locus, by polymerase chain reaction and single-strand conformational polymorphism analysis, and plasma soluble TNFRII (sTNFRII) levels were measured by ELISA. Mean plasma sTNFRII levels (pg/mL: +/-SEM) were 1224 (+/-26) and 1063 (+/-65) for 196M-postive (196 M homozygous or heterozygous) individuals and 196R homozygotes, respectively (P=0.02). CONCLUSIONS: Because sTNFRIIs can act as TNF antagonists, the association between recipient and donor TNFRII 196R allele status and acute or extensive chronic GVHD incidence, respectively, may reflect reduced circulating sTNFRII.  相似文献   
982.
983.
Elevated mammographic density is associated with increased risk of breast cancer. We conducted a reliability study on mammographic density assessments to determine their potential usefulness for projecting individual breast cancer risk. We used baseline screening mammograms from 7251 women in the Breast Cancer Detection Demonstration Project (BCDDP). Repeated measurements from the same images were used to assess measurement variability by an experienced evaluator. Intraclass correlations of assessments over time usually exceeded 0.9, indicating usefulness for prospective applications. Data also indicated it may be reasonable to include cases identified in the first year of screening together with other cases in developing a risk model. Older ages and increased weight were associated with decreased mammographic density. The density of the right breast slightly exceeded that of the left. Among women who developed breast cancer, the baseline mammographic density of the ipsilateral (diseased) breast was 0.53 (95% confidence interval (CI) 0.20-0.86) percentage units higher than in the contralateral breast.  相似文献   
984.
Derry JJ  Prins GS  Ray V  Tyner AL 《Oncogene》2003,22(27):4212-4220
Breast tumor kinase (BRK) is an intracellular tyrosine kinase expressed in differentiating epithelial cells of the gastrointestinal tract and skin, and in several epithelial cancers including carcinomas of the breast and colon. We examined expression of BRK and its mouse ortholog Src-related intestinal kinase (Sik) in prostate tissues and detected it in the nuclei of normal luminal prostate epithelial cells. BRK localization was then examined in 58 human prostate biopsy samples representing various grades of prostate cancer. While nuclear localization of BRK was present in well-differentiated tumors, it was absent in poorly differentiated tumors. However localization of Sam68, a nuclear substrate of BRK/Sik, was unaltered in all prostate tumors examined. Consistent with these results, nuclear BRK was detected in the more differentiated androgen-responsive LNCaP human prostate cancer cell line that is poorly tumorigenic in host animals, but it was primarily cytoplasmic in the undifferentiated androgen-unresponsive PC3 prostate cancer cell line that forms aggressive tumors. While PC3 cells expressed higher levels of endogenous BRK than LNCaP cells, BRK was less active in these cells. Our data suggest that BRK plays a role in differentiation of prostate epithelial cells. Altered BRK localization and/or activity may provide a prognostic indicator for prostate tumor progression and be a potential target for therapeutic intervention.  相似文献   
985.
986.
987.
American Cancer Society guidelines for breast cancer screening: update 2003   总被引:34,自引:0,他引:34  
In 2003, the American Cancer Society updated its guidelines for early detection of breast cancer based on recommendations from a formal review of evidence and a recent workshop. The new screening recommendations address screening mammography, physical examination, screening older women and women with comorbid conditions, screening women at high risk, and new screening technologies.  相似文献   
988.
OBJECTIVE: We assessed the contribution of variation in risk factor prevalence to population-density and county-level variation in breast cancer mortality rates. METHODS: In 1995 we collected risk factor information in a telephone interview of a random digit dialed sample of: (1) 1241 women from counties in the upper and lower tertiles of population density as of 1970 in the Northeast and South of the United States (Design A); (2) 2492 women from counties in the upper and lower tertiles of 1970-1979 breast cancer mortality rates in the four populations from Design A, and; (3) 276 women in Nassau County in New York State. We calculated 1990-94 mortality ratios (MRs) adjusted for breast cancer risk factors. RESULTS: The high/low population-density fully-adjusted MRs in women > or = 55 years were 1.01 (95% CI 0.9-1.2) and 1.00 (95% CI 0.8-1.2). The fully-adjusted MRs for high versus low mortality counties ranged from 0.95 (95% CI 0.8-1.2) to 1.29 (95% CI 1.0-1.6) in women > or = 55 years. CONCLUSIONS: Differences in risk factor prevalence explained higher rates in high-density versus low-density areas in older women. Modest elevations in the adjusted high/low breast cancer MRs among older women in certain groups of counties may reflect unidentified risk factors but more likely are due to chance.  相似文献   
989.
The objective of this study was to investigate the perceptions of patients with cancer, their caregivers and healthcare professionals (HCPs) about fatigue and its impact on quality of life. It was a cross-sectional survey, the respondents were patients with cancer attending three UK regional cancer centres ( n  = 1370), their informal caregivers ( n  = 1370) and a random selection of HCPs (oncologists/nurses/radiographers/haematologists; n  = 1098). The response rates for patients, caregivers and HCPs were 42%, 33% and 34% respectively. Fatigue was reported to affect 56% of patients and to have a considerable impact on quality of life. Caregivers also recognized that fatigue was a common problem, with significant effects on patients' quality of life and impact on themselves. Healthcare professionals recognized that fatigue was a common problem for their patients but overestimated its impact on some aspects of patients' daily lives. Although most HCPs reported that they prescribed/recommended treatment for over half of their patients, only 14% of patients reported receiving any such treatment. The most common advice was to take more rest and relaxation. Conclusions: patients with cancer report that fatigue is a common and distressing symptom and the importance of this symptom is generally recognized by both HCPs and lay-carers. Healthcare professionals need more information about the effectiveness of existing interventions for cancer-related fatigue and further research is required to improve the current management of this debilitating symptom.  相似文献   
990.
The present review paper uses the available evidence to make a case for a reconsideration of the practice of undertaking pre-discharge home visits with frail older people as part of decisions regarding a return home. This practice is embedded into the routine activity of acute medical wards for older people and occupies a large proportion of the time of hospital employed therapy staff, with consequent financial and resource implications. Assessments are often conducted to provide information on safe discharge rather than being located in the interests of the older person and their carer. The introduction of a new range of services bridging hospital and home raises the need for an urgent, critical appraisal of this practice.  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