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   900902篇
  免费   62645篇
  国内免费   2329篇
耳鼻咽喉   12521篇
儿科学   28785篇
妇产科学   26236篇
基础医学   126708篇
口腔科学   24736篇
临床医学   74878篇
内科学   183445篇
皮肤病学   19035篇
神经病学   71471篇
特种医学   36540篇
外国民族医学   336篇
外科学   142392篇
综合类   19045篇
一般理论   247篇
预防医学   64577篇
眼科学   20107篇
药学   63889篇
中国医学   1803篇
肿瘤学   49125篇
  2018年   9070篇
  2017年   7192篇
  2016年   7723篇
  2015年   8774篇
  2014年   12450篇
  2013年   19312篇
  2012年   25781篇
  2011年   27360篇
  2010年   16631篇
  2009年   15823篇
  2008年   26202篇
  2007年   27834篇
  2006年   28025篇
  2005年   27566篇
  2004年   26395篇
  2003年   25546篇
  2002年   25113篇
  2001年   41369篇
  2000年   42571篇
  1999年   36273篇
  1998年   9969篇
  1997年   9158篇
  1996年   9086篇
  1995年   8449篇
  1994年   8085篇
  1993年   7587篇
  1992年   28203篇
  1991年   26982篇
  1990年   26412篇
  1989年   25348篇
  1988年   23554篇
  1987年   23175篇
  1986年   22252篇
  1985年   21155篇
  1984年   15809篇
  1983年   13477篇
  1982年   8088篇
  1979年   14591篇
  1978年   10209篇
  1977年   8632篇
  1976年   8149篇
  1975年   8961篇
  1974年   10698篇
  1973年   10182篇
  1972年   9661篇
  1971年   8917篇
  1970年   8584篇
  1969年   8026篇
  1968年   7684篇
  1967年   7086篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
We evaluated the consistency of three questionnaire methods of assessing work and leisure activity in the rural biethnic population of the San Luis Valley Diabetes Study. A 7-d physical activity recall (PAR), a ranking of usual activity, and a history of usual participation in vigorous activity were used. Energy expenditure (kJ.kg-1.wk-1) (EE) was estimated from PAR. Subjects were 503 adults [49% non-Hispanic white (NHW), 51% Hispanic]. Physical activity at work rather than leisure-time activity largely determined total energy expenditure. Average EE at work increased with work rank for all subjects combined [mean EE (SEE) for rank 1 (low) = 324.2 (24.4), rank 4 (high) = 874.0 (102.1)] and within sex, ethnic, and occupational subgroups. Leisure EE increased with leisure rank only for NHW men and employed women. Similar patterns were observed in comparisons of PAR data with history of vigorous activity. Further development and validation of instruments appropriate for use across population subgroups are needed.  相似文献   
942.
The study was undertaken to analyze the basal and metoclopramide-stimulated serum PRL levels in healthy parous women users (group 1, n = 12) and non-users (group 2, n = 12) of a TCu-380 IUD. All women had regular menses and were studied between days 18 to 22 of their cycle; none had lactated nor regularly ingested any type of medication during the last six months. After a 10-12 hour overnight fast, peripheral venous blood samples were obtained through an indwelling catheter at -30, -15 and 0 minutes and at 60, 90 and 120 minutes after oral metoclopramide (10 mg). There were no significant differences in serum PRL between both groups, in basal levels nor throughout the test, whether analyzing the mean values at each sampling time, the sum of PRL levels from 60-120 minutes, or the peak levels. No correlation was observed between PRL levels and any of the clinical or obstetric characteristics of the women in both groups. Serum progesterone was greater than or equal to 4.0 ng/ml in all women. Thus, the use of alpha TCu-380 IUD did not induce any significant changes in basal nor in stimulated serum PRL levels.  相似文献   
943.
R K Parker  B Holtmann  P F White 《JAMA》1991,266(14):1947-1952
OBJECTIVE.--To assess the influence of a continuous (basal) morphine infusion as part of a patient-controlled analgesia (PCA) system on the postoperative analgesic requirement and on recovery parameters following abdominal hysterectomy. DESIGN.--Single-center, randomized, controlled protocol. SETTING.--University medical center. PARTICIPANTS.--A total of 230 adult women were randomly assigned to receive no morphine infusion (control group) or a continuous 0.5-, 1.0-, or 2.0-mg/h morphine infusion. Each patient was able to self-administer supplemental intravenous bolus doses of morphine (1 to 2 mg) using a PCA infuser. MAIN OUTCOME MEASURES.--Use of the PCA device, opioid-related side effects, recovery times, and the patients' assessment of pain and sedation on linear visual analog scales were recorded during the 72-hour study period. Follow-up questionnaires were completed by the patients and their health care professionals to assess the overall adequacy of PCA therapy. RESULTS.--Patients who received the 2-mg/h morphine infusions received significantly more opioid medication 9 to 72 hours after their operation than those who received no infusion (control group). The presence of a continuous morphine infusion of 0.5 to 2 mg/h did not significantly decrease the number of patient demands or supplemental bolus doses administered compared with the control group. Overall, 168 (84%) of the 199 patients who completed the 72-hour study were able to achieve adequate analgesia without requiring changes in the PCA regimen or experiencing major side effects. Recovery times and outcome variables were similar in all four groups. CONCLUSION.--The routine use of a continuous opioid infusion in combination with a standard PCA regimen does not improve pain management compared with PCA alone after abdominal hysterectomy.  相似文献   
944.
945.
946.
947.
948.
There are several possible determinants of obesity, including impaired thermogenesis and the differential utilization of fuels in different tissues. Whereas hypometabolism may initiate obesity in some people, once obese, individuals tend to manifest a higher resting metabolic rate because of their greater fat-free mass, exhibit an impaired thermic response to food, and expend more calories than lean individuals for equivalent amounts of activity. As a result, over a 24-h period, obese people generally expend more energy than lean people. A second determinant of obesity is related to fuel utilization and suggests that those predisposed to be obese may have an innate insulin resistance in muscle, leading to decreased uptake, oxidation, and storage of glucose in this tissue. As a result, the glucose is shunted to adipose tissue, where it is stored. With regard to treatment of obesity, emphasis on increased energy expenditure through the inclusion of reasonable amounts of activity is essential. However, this must always be combined with restraint in caloric intake.  相似文献   
949.
Idiopathic retroperitoneal fibrosis. A retrospective analysis of 60 cases   总被引:5,自引:0,他引:5  
Sixty patients with idiopathic retroperitoneal fibrosis presenting between 1965 and 1984 are reviewed. Their mean age at presentation was 56 years and the male:female ratio was 3:1. The commonest presenting symptoms were flank and abdominal pain, weight loss, nausea and polyuria. Physical examination was usually normal, expect for the presence of hypertension. Anaemia and elevation of erythrocyte sedimentation rate were usually present. Proteinuria was found in less than a third of patients at presentation and significant bacteriuria was uncommon. The correct diagnosis was made or suspected in very few patients before referral. The cumulative actuarial survival rate was 86% at 1 year and 78% at 2 years. Seventeen patients died; they were significantly older and more uraemic at the time of referral than those who survived. A few patients did well with either corticosteroid therapy or ureterolysis alone. In the majority, both operation and steroid treatment were necessary. In bilateral obstruction with residual function in both kidneys, bilateral ureterolysis proved superior to unilateral operation (each followed by steroid therapy) in conserving renal function. Operation alone or steroid therapy alone should be considered in cases where steroids or surgery respectively present particular hazards. The less traumatic unilateral operation should be considered in poor risk patients and in those whose renal function is absent on one side. In many survivors, disease activity has persisted for many years. Life-long follow-up is recommended.  相似文献   
950.
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