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   55284篇
  免费   4459篇
  国内免费   117篇
耳鼻咽喉   509篇
儿科学   2007篇
妇产科学   1414篇
基础医学   6849篇
口腔科学   639篇
临床医学   7075篇
内科学   10258篇
皮肤病学   1059篇
神经病学   5531篇
特种医学   1144篇
外科学   5941篇
综合类   503篇
现状与发展   1篇
一般理论   102篇
预防医学   7717篇
眼科学   893篇
药学   3845篇
中国医学   62篇
肿瘤学   4311篇
  2024年   63篇
  2023年   533篇
  2022年   856篇
  2021年   1919篇
  2020年   1168篇
  2019年   1901篇
  2018年   2017篇
  2017年   1536篇
  2016年   1633篇
  2015年   1720篇
  2014年   2439篇
  2013年   3211篇
  2012年   4741篇
  2011年   4703篇
  2010年   2572篇
  2009年   2134篇
  2008年   3737篇
  2007年   3671篇
  2006年   3366篇
  2005年   3217篇
  2004年   2820篇
  2003年   2381篇
  2002年   2107篇
  2001年   446篇
  2000年   356篇
  1999年   420篇
  1998年   381篇
  1997年   291篇
  1996年   243篇
  1995年   220篇
  1994年   177篇
  1993年   144篇
  1992年   249篇
  1991年   231篇
  1990年   221篇
  1989年   213篇
  1988年   188篇
  1987年   174篇
  1986年   149篇
  1985年   149篇
  1984年   128篇
  1983年   124篇
  1982年   77篇
  1981年   81篇
  1980年   74篇
  1979年   80篇
  1978年   90篇
  1977年   53篇
  1973年   42篇
  1972年   50篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
Mediastinitis is a rare but serious postoperative complication of cardiac surgery that increases mortality rates, hospital length of stay, and medical costs. A clinical trial was conducted to investigate whether the type of postoperative surgical dressing (silver nylon or standard gauze) affects the rate of mediastinal infections. The sample consisted of 1,600 surgical cardiac patients. Infection rates in the standard gauze group (control, n = 1,235) were collected retrospectively from 24 months of infection control records. In the prospective treatment arm of the study, the wounds of all consecutive surgical patients (n = 365) were covered with a silver nylon dressing and patients were assessed during the 3-week postoperative visit. Thirteen (13) patients in the control group (1%) and none of the patients in the treatment group developed mediastinitis (chi2 [1, N = 1,600] = 3.88, P <0.05). Study findings support the need for a large, prospective, controlled clinical study to confirm the effects of these dressings on mediastinitis, resultant morbidity, and costs of care.  相似文献   
962.
In a cross-sectional study of 641 Schistosoma japonicum-infected individuals in Leyte, Philippines, who were 7-30 years old, we determined the grade of hepatic fibrosis (HF) by ultrasound and used anthropometric measurements and hemoglobin levels to assess nutritional status. Serum levels of interleukin (IL)-1, IL-6, and IL-10; tumor-necrosis factor (TNF)-alpha; soluble TNF- alpha receptor I; and C-reactive protein (CRP) were measured to examine the association between these markers of inflammation and HF grade. HF was present in 8.9% of the cohort; the majority of cases were mild (grade I), and severe (grade II or grade III) cases occurred only in male individuals. Compared with individuals without HF, those with severe HF--and, to a lesser degree, those with mild HF--had a significantly lower body-mass index (BMI) and BMI z-score, a higher prevalence of anemia, and a higher level of CRP and were more likely to produce IL-6; furthermore, those with severe HF had a significantly higher level of IL-1, compared with those either without HF or with mild HF. These findings suggest that even mild HF is associated with nutritional morbidity and underscore the importance of early recognition and treatment. In addition, our data are consistent with the hypothesis that, by systemically increasing the levels of the proinflammatory cytokines IL-1 and IL-6, HF causes undernutrition and anemia.  相似文献   
963.
The article represents the proceedings of a symposium at the 2001 RSA Meeting in Montreal, Canada. The organizer/chair was Stephen Magura. The presentations examined: (1) How managed care organization policies may affect enrollees' use of alcohol and other drug (AOD) treatment, by Constance Horgan and associates; (2) The determinants of patients' access to and utilization of AOD treatment in a large health maintenance organization, by Jennifer R. Mertens and Constance Weisner; (3) The impact on treatment access and costs of a statewide carve-out for AOD treatment for Medicaid, by Donald Shepard and associates; and (4) The predictive validity of a new patient assessment technology developed, in part, to better justify AOD treatment in response to the demands of managed care, by Stephen Magura and associates.  相似文献   
964.
A protein S deficient family presenting a variant protein S molecule in plasma and platelets is described. The propositus, age 20, and two brothers suffered from venous thrombotic disease. The propositus, the only family member studied while taking oral anticoagulants, had a protein S antigen (ag) level of 17% and undetectable activity. As demonstrated by immunoblotting both the propositus and one clinically affected brother (42% ag, 7% activity) presented variant protein S molecules of 65,000 molecular weight (mol wt) while the other clinically affected brother (64% ag, 11% activity) had only protein S with normal electrophoretic mobility of 70,000 mol wt. The mother had normal protein S levels (93% ag, 100% activity) but had both normal and variant protein S molecules and based on her functional protein S data a normal anticoagulant activity of the variant molecule is suggested. One asymptomatic but protein S deficient sister (68% ag, 9% activity) as well as the asymptomatic protein S deficient father (59% ag, 10% activity) had only protein S molecules of 70,000 mol wt. The variant protein S bound to C4b-binding protein in plasma, and differed from normal protein S in carbohydrate content. Platelets of each family member contained the same immunoblotting pattern of normal and variant protein S forms as found in plasma, consistent with the hypothesis that protein S gene expression involves codominant expression of two alleles that is similar in cells that control the synthesis of both platelet and plasma forms of protein S.  相似文献   
965.
966.
OBJECTIVES: To examine the association between physical activity and inflammatory markers, with consideration for body fatness and antioxidant use. DESIGN: Cross-sectional study, using baseline data from the Health, Aging and Body Composition Study. SETTING: Metropolitan areas surrounding Pittsburgh, Pennsylvania, and Memphis, Tennessee. PARTICIPANTS: Black and white, well-functioning men and women (N=3,075), aged 70 to 79. MEASUREMENTS: Interviewer-administered questionnaires of previous-week household, walking, exercise, and occupational/volunteer physical activities. Analysis of covariance was used to examine the association between activity level and serum C-reactive protein (CRP), interleukin-6 (IL-6), and plasma tumor necrosis factor alpha (TNFalpha) with covariate adjustment. Antioxidant supplement use (multivitamin, vitamins E or C, beta carotene) was evaluated as an effect modifier of the association. RESULTS: Higher levels of exercise were associated with lower levels of CRP (P<.01), IL-6 (P<.001), and TNFalpha (P=.02) (e.g., CRP=1.95 mg/L for no exercise and 1.72 for >180 min/wk). Adjustment for body fatness attenuated the associations somewhat. Use of antioxidant supplements modified the CRP (P(interaction)=.01) and IL-6 (P(interaction)=.08) associations such that concentrations were low in those taking supplements (e.g., CRP=1.79-1.84 across exercise levels) and higher in nonsupplement users who did no exercise (2.03) than in those who did the most (1.72). Among nonexercisers, higher levels of other physical activity were related to lower levels of CRP (P<.01) and IL-6 (P=.02) but not TNFalpha (P=.36), even after accounting for body fat. CONCLUSION: Inflammatory markers are lower in older adults with higher levels of exercise and nonexercise activity and in antioxidant supplement users regardless of exercise level.  相似文献   
967.
OBJECTIVE: This qualitative study examines the "final gift exchange" process by which older adults give cherished possessions in return for lasting appreciation. METHODS: We interviewed 54 middle- and upper-middle-class people (39 women) aged 50-90 who had to dispose of personal objects when moving to smaller residences. RESULT: We used Goffman's spiraling strategy in our analysis of people's reports of disposing of personal possessions. We identified three salient dimensions (family, economy, and self) of this process and created a heuristic describing eight ideal-type gift exchange scenarios by categorizing objects as valued or not valued by family and the economy as well as being an important aspect of the gift giver's material self. DISCUSSION: By applying the heuristic, we observed that a lack of shared definitions of the meaning and value of objects created dilemmas in disposing of personal objects, particularly those connected to a person's material self. We also offer suggestions for making the process go more smoothly, such as inquiring about the preferences of others and telling stories associated with objects to create shared definitions of the objects' significance to the giver and/or to family history.  相似文献   
968.
Most estimates of the prevalence of peripheral atherosclerosis have been based on intermittent claudication or lower limb blood flow. The aim of this study was therefore to determine the prevalence of underlying femoral plaque, and to determine its association with other cardiovascular disease and risk factors. Presence of plaque was identified using ultrasound in a random sample of men (n=417) and women (n=367) aged 56-77 years. Coexistent cardiovascular disease, exercise and smoking were determined by questionnaire, blood pressure was recorded, and serum cholesterol and plasma fibrinogen were determined. Of the 784 subjects that were scanned, 502 (64%) demonstrated atherosclerotic plaque. Disease prevalence increased significantly with age (P<0.0001), and was more common in men (67.1 vs. 59.4%, P<0.05). Subjects with femoral plaque had a significantly greater odds of previous ischaemic heart disease (OR 2. 2, 95% CI 1.3, 3.7) and angina (OR 1.7, 95% CI 1.03, 2.7), but not of stroke or leg pain on exercise. Current and ex-smoking, raised serum total cholesterol and plasma fibrinogen levels, but not blood pressure, were associated with an increased risk of femoral plaque, independent of age and sex. Frequent exercise and a high HDL cholesterol were significantly associated with lower risk. In conclusion, therefore, atherosclerotic disease of the femoral artery affects almost two-thirds of the population in late middle age. It is associated with an increased prevalence of ischaemic heart disease and angina, but whether detecting at risk individuals using ultrasound offers advantages over simpler and less expensive risk factor scoring requires evaluation in trials.  相似文献   
969.
970.
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