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   2517篇
  免费   261篇
  国内免费   127篇
耳鼻咽喉   29篇
儿科学   48篇
妇产科学   25篇
基础医学   352篇
口腔科学   61篇
临床医学   202篇
内科学   384篇
皮肤病学   13篇
神经病学   182篇
特种医学   53篇
外科学   271篇
综合类   256篇
一般理论   1篇
预防医学   263篇
眼科学   62篇
药学   230篇
中国医学   82篇
肿瘤学   391篇
  2022年   50篇
  2021年   44篇
  2020年   33篇
  2019年   15篇
  2018年   33篇
  2017年   17篇
  2016年   23篇
  2015年   39篇
  2014年   36篇
  2013年   66篇
  2012年   94篇
  2011年   280篇
  2010年   191篇
  2009年   168篇
  2008年   141篇
  2007年   125篇
  2006年   113篇
  2005年   134篇
  2004年   262篇
  2003年   175篇
  2002年   98篇
  2001年   77篇
  2000年   77篇
  1999年   45篇
  1998年   29篇
  1997年   24篇
  1996年   21篇
  1995年   11篇
  1994年   12篇
  1993年   10篇
  1992年   40篇
  1991年   27篇
  1990年   26篇
  1989年   18篇
  1988年   16篇
  1987年   29篇
  1986年   25篇
  1985年   21篇
  1984年   13篇
  1983年   17篇
  1982年   10篇
  1979年   15篇
  1975年   10篇
  1974年   15篇
  1973年   12篇
  1972年   14篇
  1971年   13篇
  1970年   10篇
  1968年   13篇
  1966年   12篇
排序方式: 共有2905条查询结果,搜索用时 15 毫秒
1.
2.
Background Although prostate cancer is a leading cause of cancer death, its aetiology is not well understood. We aimed to identify novel biochemical factors for prostate cancer incidence and mortality in UK Biobank.Methods A range of cardiovascular, bone, joint, diabetes, renal and liver-related biomarkers were measured in baseline blood samples collected from up to 211,754 men at recruitment and in a subsample 5 years later. Participants were followed-up via linkage to health administrative datasets to identify prostate cancer cases. Hazard ratios (HRs) and 95% confidence intervals were calculated using multivariable-adjusted Cox regression corrected for regression dilution bias. Multiple testing was accounted for by using a false discovery rate controlling procedure.Results After an average follow-up of 6.9 years, 5763 prostate cancer cases and 331 prostate cancer deaths were ascertained. Prostate cancer incidence was positively associated with circulating vitamin D, urea and phosphate concentrations and inversely associated with glucose, total protein and aspartate aminotransferase. Phosphate and cystatin-C were the only biomarkers positively and inversely, respectively, associated with risk in analyses excluding the first 4 years of follow-up. There was little evidence of associations with prostate cancer death.Conclusion We found novel associations of several biomarkers with prostate cancer incidence. Future research will examine associations by tumour characteristics.Subject terms: Predictive markers, Prostate cancer, Risk factors  相似文献   
3.
Metabolomics may reveal novel insights into the etiology of prostate cancer, for which few risk factors are established. We investigated the association between patterns in baseline plasma metabolite profile and subsequent prostate cancer risk, using data from 3,057 matched case–control sets from the European Prospective Investigation into Cancer and Nutrition (EPIC). We measured 119 metabolite concentrations in plasma samples, collected on average 9.4 years before diagnosis, by mass spectrometry (AbsoluteIDQ p180 Kit, Biocrates Life Sciences AG). Metabolite patterns were identified using treelet transform, a statistical method for identification of groups of correlated metabolites. Associations of metabolite patterns with prostate cancer risk (OR1SD) were estimated by conditional logistic regression. Supplementary analyses were conducted for metabolite patterns derived using principal component analysis and for individual metabolites. Men with metabolite profiles characterized by higher concentrations of either phosphatidylcholines or hydroxysphingomyelins (OR1SD = 0.77, 95% confidence interval 0.66–0.89), acylcarnitines C18:1 and C18:2, glutamate, ornithine and taurine (OR1SD = 0.72, 0.57–0.90), or lysophosphatidylcholines (OR1SD = 0.81, 0.69–0.95) had lower risk of advanced stage prostate cancer at diagnosis, with no evidence of heterogeneity by follow-up time. Similar associations were observed for the two former patterns with aggressive disease risk (the more aggressive subset of advanced stage), while the latter pattern was inversely related to risk of prostate cancer death (OR1SD = 0.77, 0.61–0.96). No associations were observed for prostate cancer overall or less aggressive tumor subtypes. In conclusion, metabolite patterns may be related to lower risk of more aggressive prostate tumors and prostate cancer death, and might be relevant to etiology of advanced stage prostate cancer.  相似文献   
4.
5.
目的:建立骨钙素酶免疫测定方法,并应用于临床检测血清骨钙素。方法:应用了3种检测模式,根据检测灵敏度、剂量反应曲线的形态进行分析,选择出合适的模式进一步应用于临床血清标本的骨钙素检测。结果:所采用的骨钙素单克隆抗体是钙离子依赖型的。固相抗原竞争法适合于临床定量测定骨钙素。最低可测限为1.4μg/L;20μg/L骨钙素样品批内CV=3.98%,批间CV=12.67%。测定正常献血员140名(年龄17-45岁),第5-95百分位点的骨钙素含量,男性为7.5-15.0μg/L女性为7.0-17.5μg/L。70例疑有骨质疏松症患者血清骨钙素含量2.91-30.20μg/L,以第95百分位点的骨钙素含量为cut-off值,升高5例。与进口试剂盒(Novocalcin,USA)相比较,有较好的相关性,r=0.81。结论:固相抗原竞争法酶免疫测定可以灵敏地检测血清中骨钙素含量,有实用价值。  相似文献   
6.
Existing guidelines advise adolescents with asthma and allergies against high-risk occupations. The aim of the current authors' analyses was to investigate the resulting self-selection in a prospective cohort study. The participants of Phase II of the International Study of Asthma and Allergies in Childhood in Germany (aged 9-11 yrs at baseline) were re-contacted after 7 yrs (response rate was 77%) and were asked to complete a questionnaire, which included items on atopic diseases. The subjects were also asked about the type of job they would like to have in the future (preferred job choice). Exposure to agents with potential asthma risk was evaluated using a job exposure matrix. The analyses were restricted to those in school-based vocational training programmes without occupational exposures. A total of 33% of subjects chose jobs with high asthma risk, 23% selected low asthma risk jobs and the remaining adolescents indicated jobs without known asthma risk (reference category). There were no statistically significant associations between asthma, allergic rhinitis or atopic dermatitis and selecting jobs with asthma risk. Participants with allergic rhinitis tended to select high risk jobs less frequently. In conclusion, self-selection into low risk jobs seems to play a minor role in teenagers with asthma or allergies.  相似文献   
7.
目的 采用反向Fick氏法和间接测热法测定心脏手术后病人的全身氧耗,并比较两种测量方法的相关性和准确性。方法8例心脏手术术后病人,分别在入ICU后2h和6h时同时采用反向Fick氏和间接测热法测定病人的全身氧耗量。结果 间接测热法和反向Fick法测得氧耗分别是(16±30)ml·min-1·m-2和(127±23)ml·min-1·m-2,前者的测定结果显著高于后者(P<0.01)。相关分析显示两者有较好的相关性(r=0.92,P<0.01)。采用Bland和Altman统计分析提示两种测定结果的平均偏离值为(35.5±13.4)ml·min-1·m-2,其95%的分布范围是(9~62)ml·min-1·m-2,提示两种测量结果间的一致性较差。结论 两种方法测定心脏病人术后全身氧耗的结果有明显差异,其中反向Fick氏法的测定结果误差大、准确性差,而间接测热法是较好的临床选择。  相似文献   
8.
9.
A diary method using household measures was employed to obtain dietary records in a large national prospective survey and a computer program, DIDO (Diet In Data Out), was designed for direct entry of the diaries. The accuracy of this computerized coding system was examined alongside that of the manual coding used for a similar diary in a previous wave, 7 years earlier, of the same survey. Accuracy was assessed by analysis of the errors in the coded and checked records by stringent re-checking of nominal 2% random subsamples of the diet diaries coded by each method. The mean time to code and check each of the 2086 7-day records in the whole survey using DIDO was 58 minutes (SD 30) compared with reported results of 1–4 hours for manual methods. The mean error rate of computerized coding and checking with DIDO was 2.3% (SD 2.1; range 0–8.9) per diary in the subsample. Correcting these mistakes made insignificant changes to the calculated mean energy and nutrient intakes for the subsample. The percentage of individuals changing to an adjacent third of nutrient distribution after correcting unambiguous errors ranged from none (for alcohol) to 11% (for carbohydrate and calcium intake). The mean error rate on a similar subsample of diaries from the earlier survey which had been coded manually was significantly higher at 5.9% (SD 4.1; range 0–17) per diary. Emphasis is laid on the importance, in coding, of dealing with ambiguities in the subjects' records, since this can affect the accuracy and the precision of the nutrient results obtained. We conclude that the DIDO coding method has the advantages of greater accuracy, speed, consistency and efficient data handling, and affords greater data accessibility for checking, compared with manual systems.  相似文献   
10.
Objective: To establish a prostatic hyperplasia model with beagle dogs. Methods: Twenty-four male beagle dogs, 2 years of age, were divided into the treatment and control groups at random and were administrated testosterone propionate (TP) i.m. two months after castration. Three treatment groups were set with the doses of TP at 0.8 mg/kg, 2.5 mg/kg and 7.5 mg/kg, respectively, and the control was given the same volume of vehicle. Two months later, half of the animals were killed and sera samples were obtained. The wet weight and volume of prostate were measured. The dihydro testosterone (DHT) level of the serum and prostate were determined with the commercial radioimmunoassay (RIA) kit. The prostate was sectioned, fixed and stained with hematoxylin and eosin. Pictures were taken with a digital camera under the microscope and were analyzed with a computer for the epithelial cell height and the acinar luminal area with micro image analysis software. The prostate volume was measured with ultrasonic diagnost  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