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   4552篇
  免费   404篇
  国内免费   7篇
耳鼻咽喉   49篇
儿科学   135篇
妇产科学   95篇
基础医学   519篇
口腔科学   165篇
临床医学   512篇
内科学   798篇
皮肤病学   76篇
神经病学   361篇
特种医学   172篇
外科学   689篇
综合类   157篇
一般理论   3篇
预防医学   473篇
眼科学   59篇
药学   385篇
中国医学   4篇
肿瘤学   311篇
  2023年   30篇
  2022年   44篇
  2021年   108篇
  2020年   64篇
  2019年   107篇
  2018年   131篇
  2017年   93篇
  2016年   98篇
  2015年   98篇
  2014年   149篇
  2013年   202篇
  2012年   251篇
  2011年   249篇
  2010年   169篇
  2009年   136篇
  2008年   222篇
  2007年   203篇
  2006年   214篇
  2005年   184篇
  2004年   190篇
  2003年   179篇
  2002年   183篇
  2001年   100篇
  2000年   120篇
  1999年   114篇
  1998年   43篇
  1997年   41篇
  1996年   26篇
  1995年   33篇
  1993年   23篇
  1992年   71篇
  1991年   74篇
  1990年   74篇
  1989年   83篇
  1988年   53篇
  1987年   64篇
  1986年   55篇
  1985年   64篇
  1984年   47篇
  1983年   46篇
  1981年   25篇
  1979年   34篇
  1978年   23篇
  1976年   27篇
  1974年   33篇
  1972年   24篇
  1971年   28篇
  1970年   23篇
  1967年   21篇
  1966年   20篇
排序方式: 共有4963条查询结果,搜索用时 328 毫秒
1.
2.
Reluctance to use kidneys from older donors (>50 years of age) is based on reports of inferior results. We reviewed our experience with 45 kidneys transplanted from older donors. Primary nonfunction, immediate graft function, and 1-, 2- and 3-year graft survival rates were similar to those obtained with kidneys transplanted from donors aged between 20 and 40 years. Renal function at 1 year (as measured by serum creatinine) was poorer in kidneys from older donors. No beneficial effect with respect to graft survival was noted with cyclosporin therapy compared to conventional immunosuppression; however, the numbers are small. We conclude that kidneys from older donors are a valuable source for transplantation.  相似文献   
3.
S M Donovan  Y Oh  H Pham  R G Rosenfeld 《Endocrinology》1989,125(5):2621-2627
Insulin-like growth factors (IGF-I and -II) are peptide growth factors that may be important for neonatal development. Specific high affinity IGF binding proteins (BPs) have been characterized in serum and extracellular fluids. The major serum binding complex in the adult has an apparent Mr of 150 K, while the predominant BP in the neonate is approximately 30 K. In the rat, the transition from the neonatal BP to the adult form occurs during the third postnatal week, concomitant with an increase in serum IGF-I and a decrease in serum IGF-II concentrations. Using specific RIAs and Western ligand blot analyses we have characterized the changes in serum IGF and IGF BPs, respectively, during the early postnatal period. Seven BPs were identified in serum with apparent Mr values of 42, 41, 40, 38, 28, 26, and 22 K. After deglycosylation, the 42, 41, 40, and 38 K BPs were reduced to two bands with apparent Mr values of 35 and 32 K, while the 28, 26, and 22 K BP were unchanged. In the neonate, the 28, 26, and 22 K BPs were present, with the 28 K BP in highest concentration. With increasing age, the 28 K BP decreased and the 42, 41, 40, and 38 K BPs appeared at approximately 19 days of age. Comparison of Western ligand blots of neonatal serum, BRL-3A conditioned media, rat amniotic fluid, and rat cerebrospinal fluid (CSF) demonstrated that all contained a prominent 28 K BP. A polyclonal antibody (alpha Hec 1) developed against the 31 K human IGF-BP (hBP-31) immunoprecipitated the 28 K BP from neonatal rat serum, BRL-3A media, rat amniotic fluid, and rat CSF, but did not react with adult rat serum. These findings suggest that, in the rat, the predominant neonatal serum BP is structurally and immunologically similar to the major BRL-3A, amniotic fluid, and CSF BPs, but distinct from the predominant adult serum BP.  相似文献   
4.
5.
6.
Longitudinal research studies focused on alcohol use initiation in adolescence were reviewed to determine which variables function as antecedent predictors or risk factors. Only studies that focused on time-1 abstainers were included. Classes of risk factors examined include sociodemographic, family, peer, personality, and behavioral variables. The most consistent antecedent risk factors for starting to drink in adolescence were parental and peer approval and models for drinking and drug use as well as adolescents’ own prior involvement in delinquent behavior. There was little evidence for gender differences in risk factors for alcohol use initiation. Secondary analyses of existing longitudinal data sets are encouraged to examine whether there are ethnic/racial differences in the risk factors for starting to drink and to establish those factors that serve a protective or buffering function, delaying onset of alcohol use in adolescence.  相似文献   
7.
J M Donovan  D M Gleason 《Urology》1990,35(5):458-463
The most specific radiographic findings characterizing stress incontinence (SI) on upright retrograde urethrocystography include replacement of a flat or rounded bladder base with a concave funnelled base; patency of the bladder neck with contrast material pooling in the proximal urethra; the descent of the intravesical Foley balloon beyond the internal meatus and into the proximal urethra. We found that neither a cystocele nor the dependent position of the urethra at the bottom of the bladder were diagnostic of SI if the above stigmata were absent. On the other hand the defect of urgency incontinence (UI) is functional. The bladder can usually be filled by retrograde urethral infusion (though in severe UI this may not be the case). An alert technician can frequently obtain a film when the patient is experiencing uninhibited voiding. The finding of contrast material throughout the urethra, in the distal urethra alone, or in the parameatal area is strongly suspicious for UI, especially when trabeculation is also seen. These findings in association with the stigmata of SI give warning of combined SI and UI.  相似文献   
8.
In a randomised controlled trial intensive individual anti-smoking advice given in parallel with hospital antenatal care did not influence the outcome of pregnancy. The belief that retardation of fetal growth caused by maternal smoking occurs in late pregnancy is not well based, and the advice may not have been given in time to be effective. Other possible interpretations of the results, that maternal smoking is merely an index of some other factor that retards growth or that those counselled did not reduce their smoking sufficiently to influence outcome, cannot be excluded.  相似文献   
9.
Empirical methods have been found to be superior to clinical judgment for the purpose of correctly identifying patients at risk for treatment failure and, hence, to enhance psychotherapy outcomes. The development and evaluation of an empirical approach aimed at supporting clinical decisions during the course of psychotherapy is described. The tool provides predictions based on a patient‐specific sampling strategy called the nearest neighbors method and on growth curve approaches to model an expected treatment course for each patient. Using session‐by‐session data from an outpatient center in the US (N = 4365), this new empirically derived decision model was evaluated and compared with a clinically based approach loosely based on an adaptation of clinically significant change concepts. The empirically derived decision system was found to be superior to the rational clinically based one in almost all measures of prediction accuracy, indicating its potential to identify patients at risk for treatment failure. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
10.
BACKGROUND: Little is known about parental experience and decision making with regard to premature infants requiring intensive care in developing countries. We undertook this study to characterise parents' experience of physician counselling and their role in making life-support decisions for very low-birth-weight (VLBW) (birth weight < 1 501 g) infants born in South Africa's public-sector neonatal intensive care units (NICUs). METHODS: Parents of surviving VLBW infants treated in three Johannesburg-area public hospitals and attending follow-up clinics in August 2001 were interviewed regarding their experience of perinatal counselling on outcomes (pain, survival, disability), perception of actual and optimal decision making, and satisfaction with NICU communication. RESULTS: Parents of 51 infants were interviewed. Seventy-five per cent of parents reported antenatal counselling by physicians on at least one perinatal topic (severe disability, pain, death, finances or religious/moral considerations). The majority of parents (> 60%) who received counselling thought that these topics had been discussed adequately. Most parents reported that doctors had the primary decision-making role, either without consulting them (41%) or after consulting them (37%). Joint decision making was rare (14%). Parents wanted more input in life-support decisions than they reported being given. CONCLUSION: Counselling is not consistently provided in public-sector hospitals in Johannesburg. Parents of premature infants want a larger share in NICU decision making than they currently experience. Most parents were satisfied with communication later during their infant's hospitalisation. South Africa presents a unique opportunity to study the use of advanced medical technologies in a nation with marked disparities in access to care.  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