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   2589095篇
  免费   184590篇
  国内免费   7573篇
耳鼻咽喉   34278篇
儿科学   85236篇
妇产科学   71629篇
基础医学   363723篇
口腔科学   69665篇
临床医学   234704篇
内科学   515661篇
皮肤病学   62483篇
神经病学   213586篇
特种医学   99900篇
外国民族医学   736篇
外科学   386474篇
综合类   50419篇
现状与发展   5篇
一般理论   970篇
预防医学   196445篇
眼科学   56682篇
药学   188041篇
  8篇
中国医学   5333篇
肿瘤学   145280篇
  2021年   19998篇
  2019年   20641篇
  2018年   29317篇
  2017年   22622篇
  2016年   26250篇
  2015年   29535篇
  2014年   40488篇
  2013年   60492篇
  2012年   80314篇
  2011年   84577篇
  2010年   51048篇
  2009年   49197篇
  2008年   79121篇
  2007年   83913篇
  2006年   85634篇
  2005年   81789篇
  2004年   78802篇
  2003年   76122篇
  2002年   73399篇
  2001年   128425篇
  2000年   131337篇
  1999年   110505篇
  1998年   31269篇
  1997年   27926篇
  1996年   28227篇
  1995年   27394篇
  1994年   25076篇
  1993年   23424篇
  1992年   85166篇
  1991年   81567篇
  1990年   78788篇
  1989年   76064篇
  1988年   69474篇
  1987年   68000篇
  1986年   63547篇
  1985年   60513篇
  1984年   44944篇
  1983年   37948篇
  1982年   22465篇
  1981年   19986篇
  1979年   38960篇
  1978年   27441篇
  1977年   23253篇
  1976年   21496篇
  1975年   22813篇
  1974年   26787篇
  1973年   25373篇
  1972年   23749篇
  1971年   21957篇
  1970年   20184篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Fifty-five children (34 boys, 21 girls; age range, 1 day to 18 years) with increased echogenicity of the renal medullary pyramids at ultrasound evaluation were identified. The clinical diagnoses associated with hyperechoic medullary pyramids could be separated based on the presence or absence of hypercalciuria. Patients with drug-induced hypercalciuria included 10 infants treated with furosemide, two treated with long-term steroid therapy, and one treated with excessive amounts of vitamin D. Other clinical conditions associated with hypercalciuria included renal tubular acidosis (n = 10), Bartter syndrome (n = 5), hyperparathyroidism (n = 3), Williams syndrome (n = 2) and medullary sponge kidney (n = 2). Ten children with transient renal insufficiency and three with sickle cell disease had normal urine calcium concentration. Isolated disease entities accounted for the remainder of cases. A specific diagnosis can usually be made in a patient with hyperechoic renal medullary pyramids by using a systematic clinical approach that includes evaluation of patient age, serum and urine calcium concentration, and renal function.  相似文献   
993.
The authors present an improvement to a sigma-filter extrapolation method for the reconstruction of magnetic resonance (MR) images from symmetric discrete Fourier data. By making use of the phase information in the image data, the proposed method can overcome the data inconsistency problem of the original method for handling MR image data with large phase variations, such as those obtained in gradient-echo pulse sequences. Reconstruction results show that its performance is comparable with that of the modified complex sigma-filter method proposed previously to handle the inconsistency problem. However, the new approach has the advantage of reducing computation time by a factor of two with use of a sigma filter applied to real instead of complex images. It is expected that this method will be more practical for use in clinical MR imaging systems.  相似文献   
994.
Seventy seven antral biopsies were collected from patients attending endoscopy clinic at King Khalid University Hospital, Riyadh, Saudi Arabia during a period of six months between December 1988 to May 1989. Of these 69 (89.6%) showed chronic gastritis as well as Helicobacter-like organisms (HLOs) in the biopsy specimens while 63 (81.8%) of biopsies grew Helicobacter pylori on culture. These findings indicate a good correlation between the histological diagnosis of chronic gastritis and isolation of H. pylori on culture.  相似文献   
995.
996.
We sought to determine whether there are indirect costs of teaching in Canadian hospitals. To examine cost differences between teaching and nonteaching hospitals we estimated two cost functions: cost per case and cost per patient-day (dependent variables). The independent variables were number of beds, occupancy rate, teaching ratio (number of residents and interns per 100 beds), province, urbanicity (the population density of the county in which the hospital was situated) and wage index. Within each hospital we categorized a random sample of patient discharges according to case mix and severity of illness using age and standard diagnosis and procedure codes. Teaching ratio and case severity were each highly correlated positively with the dependent variables. The other variables that led to higher costs in teaching hospitals were wage rates and number of beds. Our regression model could serve as the basis of a reimbursement system, adjusted for severity and teaching status, particularly in provinces moving toward introducing case-weighting mechanisms into their payment model. Even if teaching hospitals were paid more than nonteaching hospitals because of the difference in the severity of illness there should be an additional allowance to cover the indirect costs of teaching.  相似文献   
997.
Evidence indicates that endogenous opioid peptides and glucocorticoids participate in the control of cardiovascular regulation during hemorrhagic shock. In the present study, we investigated a possible interaction between brain opioid peptides and adrenal corticosteroids regarding the control of arterial pressure during hemorrhage. The bleeding volumes required to lower arterial pressure to 80, 60 and 40 mmHg were studied in anesthetized sham-operated (SHAM) and adrenalectomized (ADX) rats. I.c.v. administration of 10 micrograms of naloxone resulted in a significant increase in the bleeding volume required to lower arterial pressure from 60 to 40 mmHg in SHAM animals, whereas no effect of naloxone was observed in ADX animals. Replacement therapy with a 100% corticosterone pellet (100 mg, s.c.), but not with a 12.5% corticosterone pellet (12.5 mg corticosterone and 87.5 mg cholesterol, s.c.), resulted in an effect of naloxone on the bleeding volume in ADX animals. The effect of replacement therapy could be inhibited by i.c.v. pretreatment with the synthetic glucocorticoid receptor antagonist, RU38486 (100 ng). These data suggest that (1) opioid mechanisms are involved in the regulation of blood pressure during hemorrhage, and (2) occupancy of glucocorticoid receptors is required for naloxone to exert its hemodynamic effect during hemorrhagic hypotension in ADX rats.  相似文献   
998.
Circulating immune complexes in pre-eclampsia.   总被引:3,自引:0,他引:3  
Serum samples from 20 non-pregnant women, 30 women with normal pregnancy and 50 women with pregnancy associated with pre-eclampsia were tested for circulating immune complexes using the polyethyleneglycol precipitation method. A highly significant positive correlation was found between circulating immune complexes and severe pre-eclampsia (BP greater than 140/90 mm Hg, albuminuria greater than 0.25 g/l). In contrast to this the difference in immune complex levels between non-pregnant subject, normal pregnancy cases and patients with mild pre-eclampsia was not statistically significant. A significant positive correlation was found between the level of circulating immune complexes and the severity of albuminuria. These findings suggest that circulating immune complexes, though not seeming to play an aetiological role in pre-eclampsia may very well be involved in its pathogenesis.  相似文献   
999.
Existing triage algorithms consider, for the most part, only the primary casualty with physical trauma. Algorithms fail to appreciate the primary, secondary, or tertiary neuropsychiatric casualty. Research advances on neuropsychiatric casualties must link with the mandates of emergency medical services and disaster management to improve triage sensitivity and specificity. Early recognition and management of neuropsychiatric casualties will diminish the potential for long-term consequences. Expanded triage algorithm supplements are proposed to improve the recognition of those victims at risk.  相似文献   
1000.
The authors suggest additional criteria evidencing inflammations in the gallbladder and colloid stability of the bile: bile acid absorption and cholesterol sedimentation coefficients. Derivation of these coefficients is based on biochemical examination of the bile with measurements of bile acid, cholesterol, and bilirubin concentrations in both portions. The results of examinations of 99 subjects evidence the diagnostic value and specificity of the characteristics, and availability of this method for clinical practice.  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