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   1174篇
  免费   139篇
  国内免费   49篇
耳鼻咽喉   9篇
儿科学   96篇
妇产科学   17篇
基础医学   98篇
口腔科学   44篇
临床医学   104篇
内科学   363篇
皮肤病学   29篇
神经病学   23篇
特种医学   189篇
外科学   66篇
综合类   101篇
预防医学   82篇
眼科学   9篇
药学   73篇
中国医学   3篇
肿瘤学   56篇
  2024年   3篇
  2023年   16篇
  2022年   13篇
  2021年   24篇
  2020年   23篇
  2019年   8篇
  2018年   19篇
  2017年   43篇
  2016年   37篇
  2015年   29篇
  2014年   63篇
  2013年   72篇
  2012年   27篇
  2011年   26篇
  2010年   63篇
  2009年   68篇
  2008年   27篇
  2007年   64篇
  2006年   35篇
  2005年   31篇
  2004年   30篇
  2003年   19篇
  2002年   14篇
  2001年   29篇
  2000年   13篇
  1999年   18篇
  1998年   77篇
  1997年   64篇
  1996年   59篇
  1995年   50篇
  1994年   46篇
  1993年   42篇
  1992年   12篇
  1991年   5篇
  1990年   18篇
  1989年   22篇
  1988年   24篇
  1987年   14篇
  1986年   19篇
  1985年   17篇
  1984年   9篇
  1983年   12篇
  1982年   9篇
  1981年   4篇
  1980年   8篇
  1979年   4篇
  1978年   6篇
  1977年   5篇
  1976年   12篇
  1975年   9篇
排序方式: 共有1362条查询结果,搜索用时 15 毫秒
81.
82.
The long-term effects of radiotherapy and chemotherapy are becoming increasingly reconginzed as the cure rates of certain childhood malignancies improve. The endocrine system is particularly sensitive to cancer therapies. Long-term survivors of childhood cancer who received cranial irradiation have been shown to have lower than predicted height, an increased prevalence of obesity and redutions in strength, exercise tolerance, bone mineral density, quality of life and academic achievement. Growth hormone deficiency (GHD) is the most frequent endocrine deficiency observed following cranial irradiation. Adults with GHD resulting from primary hypothalamic-pituitary disease during childhood have been shown to exhibit a clinical picture similar to that described in long-term survivors of childhood cancer: increased fat mass and reduced lean mass, strength, exercise tolerance, bone mineral density and quality of life. This review considers the possible contributin of GHD to the adverse sequelae observed in long-term survivors of childhood malignancy and includes our preliminary experience in treating 14 adults with GHD resulting from the treatment of childhood malignancies.  相似文献   
83.
Stratified randomization is widely used in clinical trials to achieve balance of the treatment assignment with regard to important prognostic factors. Sometimes the prognostic or stratification factor is concerned with patient medical and medication history, for which accurate information may not be available at the time of randomization. Therefore, the value of the stratification factor provided at randomization may later be identified to be incorrect. When such errors occur, patients may be allocated into strata they do not belong to. The intended treatment balance regarding the stratification factors may be disrupted. We evaluated the impact of such errors in stratification on the intended balance. We further investigated the analysis options in presence of stratification errors under both randomization and population models. Some simulations were performed to evaluate the treatment balance and properties of analysis approaches. We also provided experience with some real clinical trials.  相似文献   
84.
Trials which randomize practices II: sample size   总被引:3,自引:0,他引:3  
Kerry  SM; Bland  JM 《Family practice》1998,15(1):84-87
BACKGROUND: When practices are randomized in a trial and observations are made on the patients to assess the relative effectiveness of the different interventions, sample size calculations need to estimate the number of practices required, not just the total number of patients. OBJECTIVE: Our aims were to introduce the methodology for appropriate sample size calculation and discuss the implications for power. METHOD: A worked example from general practice is used. DISCUSSION: Designs which randomize practices are less powerful than designs which randomize patients to intervention groups, particularly where a large number of patients is recruited from each practice. Studies which randomize few practices should be avoided if possible, as the loss of power is considerable and simple randomization may not ensure comparability of intervention groups.   相似文献   
85.
For a clinical trial with a time-to-event primary endpoint, the rate of accrual of the event of interest determines the timing of the analysis, upon which significant resources and strategic planning depend. It is important to be able to predict the analysis time early and accurately. Currently available methods use either parametric or nonparametric models to predict the analysis time based on accumulating information about enrollment, event, and study withdrawal rates and implicitly assume that the available data are completely reported at the time of performing the prediction. This assumption, however, may not be true when it takes a certain amount of time (i.e., event-reporting lag) for an event to be reported, in which case, the data are incomplete for prediction. Ignoring the event-reporting lag could substantially impact the accuracy of the prediction. In this paper, we describe a general parametric model to incorporate event-reporting lag into analysis time prediction. We develop a prediction procedure using a Bayesian method and provide detailed implementations for exponential distributions. Some simulations were performed to evaluate the performance of the proposed method. An application to an on-going clinical trial is also described.  相似文献   
86.

Background

Cryptosporidium spp. is a coccidian parasite infected humans and animals. Prevalence rate of Cryptosporidium spp. infection associated with is some parameters such as sampling, age, season, country and contact to domestic animals. This study aimed to determine Cryptosporidium spp. Infection in humans and some animals in rural areas of Shushtar district from Khuzestan Province, south- west of Iran.

Methods

In this study, Stool specimens were randomly collected from 45 cattle, 8 buffalos, 35 calves, 22 turkeys, 3 sheep, 2 geese as well as 62 humans in different seasons selected from rural areas of Shushtar district located in Khuzestan in the south- west of Iran from August 2009 to April 2011. The collected stool samples were examined by modified Ziehl-Neelsen staining method.

Results

Altogether, 68/115 (59.1%) domestic animals and 9/62 (14.5%) of humans were showed Cryptosporidium spp. infection in the study areas.

Conclusion

In this study we found the high frequency of Cryptosporidium spp. infection in the studied areas.  相似文献   
87.
88.
TARO KONO  MD  PHD    BRIAN M. KINNEY  SM  MD    WILLIAM FREDERICK GROFF  DO    HENRY H. CHAN  MD  FRCP    ALI RIZA ERCOCEN  MD    MOTOHIRO NOZAKI  MD  PHD 《Dermatologic surgery》2008,34(S1):S25-S30
BACKGROUND At present, various hyaluronic acids are being used to rejuvenate facial skin. There is no comparative study of single cross-linked hyaluronic acid (SCHA) versus double cross-linked hyaluronic acid (DCHA). The objective of our study is to compare the effectiveness and complications of SCHA versus DCHA in the treatment of glabellar lines.
METHODS Ten female patients were enrolled in this randomized, evaluator-blind study. One side (left vs. right) of each patient's glabellar lines was treated with SCHA and the other side was treated with DCHA. Two independent blinded observers reviewed the clinical photographs at 3, 6, 9, and 12 months after the treatment and assessed for degree of improvement as well as complications.
RESULTS The two products were equally effective in producing an optimal cosmetic result, although at 6, 9, and 12 months posttreatment, a higher proportion of patients showed over 50% improvement with DCHA than with SCHA. At 12 months posttreatment, DCHA was considered superior in 70% of patients, whereas SCHA was superior in 10% of patients.
CONCLUSIONS Both SCHA and DCHA are equally effective in producing an optimal cosmetic result. DCHA provides a more durable esthetic improvement when compared to SCHA in the treatment of glabellar lines.  相似文献   
89.
ObjectivesTo optimize, apply, and validate a scoring algorithm that provides a utility index from a cancer-specific quality of life questionnaire called the Utility-Based Questionnaire-Cancer (UBQ-C) using data sets from randomized trials in breast cancer. The index is designed to reflect the perspective of cancer patients in a specific clinical context so as to best inform clinical decisions.MethodsWe applied the UBQ-C scoring algorithm to trials of chemotherapy for advanced (n = 325) and early (n = 126) breast cancer. The algorithm converts UBQ-C subscales into a subset index, and combines it with a global health status item into an overall HRQL index, which is then converted to a utility index using a power transformation. The optimal subscale weights were determined by their correlations with the global scale in the relevant data set. The validity of the utility index was tested against other patient characteristics.ResultsOptimal weights (range 0–1) for the subset index in advanced (early) breast cancer were: physical function 0.20 (0.09); social/usual activities 0.23 (0.25); self-care 0.04 (0.01); and distresses 0.53 (0.64). Weights for the overall HRQL index were health status 0.66 (0.63) and subset index 0.34 (0.37). The utility index discriminated between breast cancer that was advanced rather than early (means 0.88 vs. 0.94, P < 0.0001) and was responsive to the toxic effects of chemotherapy in early breast cancer (mean change 0.07, P < 0.0001).ConclusionsThe scoring algorithm for the UBQ-C utility index can be optimized in different clinical contexts to reflect the relative importance of different aspects of quality of life to the patients in a trial. It can be used to generate sensitive and responsive utility scores, and quality-adjusted life-years that can be used within a trial to compare the net benefit of treatments and inform clinical decision-making.  相似文献   
90.
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