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   2483987篇
  免费   199445篇
  国内免费   4503篇
耳鼻咽喉   35674篇
儿科学   75595篇
妇产科学   65383篇
基础医学   350993篇
口腔科学   71861篇
临床医学   222210篇
内科学   491335篇
皮肤病学   51027篇
神经病学   209781篇
特种医学   98224篇
外国民族医学   886篇
外科学   371885篇
综合类   56767篇
现状与发展   1篇
一般理论   998篇
预防医学   205128篇
眼科学   58260篇
药学   186263篇
  4篇
中国医学   4861篇
肿瘤学   130799篇
  2018年   28045篇
  2017年   21180篇
  2016年   22948篇
  2015年   25958篇
  2014年   36478篇
  2013年   55200篇
  2012年   76495篇
  2011年   80416篇
  2010年   46425篇
  2009年   43748篇
  2008年   75175篇
  2007年   79879篇
  2006年   80408篇
  2005年   78096篇
  2004年   74812篇
  2003年   71987篇
  2002年   70934篇
  2001年   114310篇
  2000年   118585篇
  1999年   99929篇
  1998年   28233篇
  1997年   25756篇
  1996年   25667篇
  1995年   24812篇
  1994年   23323篇
  1993年   21711篇
  1992年   80361篇
  1991年   77254篇
  1990年   74491篇
  1989年   71647篇
  1988年   66592篇
  1987年   65516篇
  1986年   62157篇
  1985年   59113篇
  1984年   44771篇
  1983年   38142篇
  1982年   23142篇
  1981年   20560篇
  1979年   41978篇
  1978年   29440篇
  1977年   24805篇
  1976年   23241篇
  1975年   24459篇
  1974年   30306篇
  1973年   28768篇
  1972年   26879篇
  1971年   24803篇
  1970年   23360篇
  1969年   21736篇
  1968年   19802篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Twenty-four malnourished patients requiring total parenteral nutrition were randomly assigned to receive a daily infusion of either Lipofundin MCT-LCT [a new lipid preparation containing medium-chain triglycerides (MCTs)], or Lipofundin S [a long-chain triglyceride (LCT) preparation] for 6-28 d. No adverse clinical effects were apparent in patients receiving the new emulsion. Hematological indices were unchanged. Plasma urea concentrations rose less on MCT-LCT than on LCT and the plasma bilirubin concentration was lower. Plasma ketones were higher immediately after the MCT-LCT infusion but not at other times. Triglyceride and fatty acid concentrations were similar. Insulin concentrations were higher on MCT-LCT than on LCT. Daily nitrogen balance values were not significantly different between the two groups. Urinary carnitine excretion fell dramatically on both lipids.  相似文献   
992.
DNR in the operating room. Not really a paradox   总被引:1,自引:0,他引:1  
S J Youngner  H F Cascorbi  J M Shuck 《JAMA》1991,266(17):2433-2434
  相似文献   
993.
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts.  相似文献   
994.
Access to care     
J La Puma 《JAMA》1991,266(20):2832-2833
  相似文献   
995.
996.
Thiazide diuretics may preserve bone mass and prevent elderly women's osteopenic fractures, but studies have not distinguished between thiazide preparations or examined former users. We performed a case-control study looking at thiazide use and subsequent hip fracture in postmenopausal female members of the Framingham Study cohort. Cases who had experienced a first hip fracture (n = 176) were compared with age-matched controls (n = 672). Results showed a modest protective effect of any recent thiazide use (not significant). However, recent pure thiazide users experienced significant protection against fracture (adjusted odds ratio, 0.31; 95% confidence interval, 0.11 to 0.88), whereas recent users of combination drugs containing thiazides experienced no protection (adjusted odds ratio, 1.16; 95% confidence interval, 0.44 to 3.05). Combination drugs generally contained only 25 mg of hydrochlorothiazide, suggesting that the small amount of thiazide was insufficient to preserve bone mass. Former thiazide users were not protected against fracture. In sum, recent pure thiazide use in women protects against hip fracture.  相似文献   
997.
998.
Exposure of young children to group day-care settings increases the risk of illness and may result in higher use of medical care. These observations raise concerns that the use of such settings for early intervention programs for low-birth-weight infants may increase the already high burden of medical care costs incurred by these children and their families. To address the question of medical care use associated with center-based care, we examined the hospital-based and ambulatory care reported for participants of the Infant Health and Development Program. This project is a multisite randomized trial of an early intervention program for preterm low-birth-weight infants with an intervention including 2 years of center-based care. The Intervention group did not differ in hospital-based care and averaged only two more physicians' visits over the 3-year observation period than the comparison group. We conclude that early intervention programs involving high-quality group care are not accompanied by substantial increases in health care use.  相似文献   
999.
J Winkler  M Neuman-Levin  G Boner 《JAMA》1991,265(5):631-632
A 37-year-old woman patient, known to have poorly controlled arterial hypertension that was diagnosed following a cerebrovascular accident at the age of 15 years, was referred to our outpatient clinic for investigation in 1987. An intrarenal arteriovenous fistula was diagnosed by selective renal angiography. Embolization of the fistula was performed using four 15-mm/5-cm coils, which induced thrombosis and obstructed the fistula. The vascularization of the affected kidney improved immediately. During the following 4 months, the antihypertensive treatment was stopped gradually, and the patient remained normotensive. This is an unusual case of a large intrarenal arteriovenous fistula, whose etiology was not clear, that was successfully treated by percutaneous embolization.  相似文献   
1000.
In 1984, in addition to its standard traditional curriculum, Rush Medical College (Chicago, Ill) developed a Socratic problem-based method of teaching basic science material called the alternative curriculum. As part of an evaluation of this new curriculum, students in the two curricula were compared using three traditional measurements: (1) test scores from the National Board of Medical Examiners, Part I; (2) test scores from the National Board of Medical Examiners, Part II; and (3) performance on an oral examination. Alternative curriculum students did not differ significantly from their traditional curriculum classmates on National Board of Medical Examiners, Part I and Part II total scores, although their subset scores on Part I did tend to be lower, reaching significance in one subset area. Differences in performance favoring the traditional curriculum were primarily seen in the early years of the program. Alternative curriculum students in the class matriculated in 1987 scored significantly higher in three of five categories on the oral examination.  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