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   2544972篇
  免费   210748篇
  国内免费   15692篇
耳鼻咽喉   35803篇
儿科学   74532篇
妇产科学   65146篇
基础医学   354460篇
口腔科学   70560篇
临床医学   238311篇
内科学   492702篇
皮肤病学   49895篇
神经病学   209490篇
特种医学   101953篇
外国民族医学   983篇
外科学   377417篇
综合类   85259篇
现状与发展   40篇
一般理论   995篇
预防医学   202259篇
眼科学   59981篇
药学   196078篇
  193篇
中国医学   15166篇
肿瘤学   140189篇
  2021年   25640篇
  2019年   23267篇
  2018年   30519篇
  2017年   24604篇
  2016年   25981篇
  2015年   31626篇
  2014年   43636篇
  2013年   60131篇
  2012年   82219篇
  2011年   86911篇
  2010年   51911篇
  2009年   48082篇
  2008年   78222篇
  2007年   81990篇
  2006年   82558篇
  2005年   80419篇
  2004年   74593篇
  2003年   71778篇
  2002年   70183篇
  2001年   115168篇
  2000年   119477篇
  1999年   101512篇
  1998年   29940篇
  1997年   27711篇
  1996年   27104篇
  1995年   26247篇
  1994年   24579篇
  1993年   22389篇
  1992年   80360篇
  1991年   77270篇
  1990年   74261篇
  1989年   71464篇
  1988年   66416篇
  1987年   65258篇
  1986年   61669篇
  1985年   58681篇
  1984年   44344篇
  1983年   37760篇
  1982年   22948篇
  1979年   41367篇
  1978年   29017篇
  1977年   24371篇
  1976年   22857篇
  1975年   23981篇
  1974年   29663篇
  1973年   28061篇
  1972年   26239篇
  1971年   24165篇
  1970年   22761篇
  1969年   21101篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The effects of nonprotein energy source (ie, glucose only vs glucose and lipid) on nitrogen retention and total-body protein turnover were studied in 20 parenterally fed newborn infants. All infants received approximately 3 g amino acids and 80-90 kcal.kg body wt.d. Total-body protein synthesis was estimated by using three constant-infusion, end-product methods: enrichment of urinary urea and ammonia in response to a [15N]glycine label and exhaled carbon dioxide enrichment in response to a [1-13C]leucine label. No differences were seen in nitrogen retention between the two energy sources. The estimate of total-body protein turnover obtained from the 13C label was similar to that obtained with the [15N]urea label. No differences in turnover rates were observed between the two diet groups. Use of the glucose-plus-lipid fuel system enhanced energy storage and the reutilization of amino acid for protein synthesis.  相似文献   
992.
993.
The authors present 50 cases of cervical spondylotic myelopathy treated by anterior or posterior approach. To assess the severity of the pre- and postoperative neurological symptoms, they define an original ten-point classification scale taking into account gait and urinary disturbance, ability to manipulate objects and pain. With C2-C7 laminectomy, 60% of the patients are improved, essentially for walk. A few cases only (14%) are upgraded for upper limbs function. The authors conclude that this surgical treatment should be applied only when there is a multi-level narrowed canal and predominant lower limbs deficits. The efficacy of the anterior approach depends on complete removal of osteophytes. In cases with complete osteophytectomy, this surgical treatment can improve both the upper and lower limbs function and 77.8% good results are obtained. In a few cases it may be necessary to use both approach successively. Discriminant analysis applied to 12 factors shows that pre-operative scores of upper and lower limbs and sagittal diameter of spinal canal are the most important factors for neurological prognosis.  相似文献   
994.
Neuropeptide Y-like immunoreactivity in neurons of the human retina   总被引:1,自引:0,他引:1  
The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) was investigated in wholemounts and in transverse sections of the human retina. NPY-LI was localized to the soma and axonal processes of large ganglion cells (GCs) and to the soma and dendritic arborization of amacrine cells (ACs). NPY-LI GCs were unevenly distributed across the retina, the highest density of 875 cells/mm2 was found in the fovea centralis and the lowest density of 15 cells/mm2 in the peripheral retina. The total number of NPY-LI GCs in the retina was estimated to be about 85,000. The soma sizes of NPY-LI GCs increased from 116 microns 2 +/- 23 (s.d.) in the retinal centre to 251 microns 2 +/- 57 in the retinal periphery. The soma size of NPY-LI ACs was in the range of 40 and 50 microns 2. In transverse sections NPY-LI was seen to be localized to the optic fibre layer, to the somata of GCs, to the scleral sublamina of the inner plexiform layer (AC dendrites) and to the innermost part of the inner nuclear layer (somata of ACs). The gradients of soma sizes and retinal distribution of NPY-LI GCs were taken as an indication that they correspond to the class of large to very large GCs, previously identified in the human retina by Golgi impregnation.  相似文献   
995.
996.
CGS 10078B (CGS; 1-[2,3-dihydro-1,4-(2S)-benzodioxin-2-yl]-5-[2,3-dihydro-1,4-(2R)- benzodioxin-2-yl]-3-(1R,5S)-aza-1,5-pentanediol methane sulfonate) is an agent with alpha- and beta-receptor and calcium channel blocking actions. To study its antiarrhythmic activity, cats were anesthetized with alpha-chloralose, ventilated, and given atropine and gallamine. CGS (10 or 20 mg/kg, i.v.) was infused 15 min prior to ouabain. Bolus injections of ouabain (25 micrograms/kg, i.v.) were given every 15 min until death (D). Some cats were pretreated with reserpine (R; 5 mg/kg, i.p.) 24 h prior to the experiment. In other cats 6-hydroxydopamine (6-OHDA; 20 mg/kg, i.v.) was administered 3 days prior to CGS 20 mg/kg and ouabain. Data were compared with those of Lathers [Eur. J. Pharmacol. 64: 95, 1980], i.e., with 12 cats who received only ouabain and with 11 pretreated with timolol (T; 5 mg/kg, i.v.) prior to ouabain. After CGS (10 or 20 mg/kg, i.v.), but just prior to the first dose of ouabain, the blood pressure (BP) was decreased (p less than 0.05) from control (165 +/- 6 vs. 96 +/- 7, and 136 +/- 5 vs. 90 +/- 10 mm Hg, respectively). Comparable heart rate (HR) values were also decreased (p less than 0.05) from 225 +/- 17 to 166 +/- 14 and from 193 +/- 8 to 152 +/- 6 beats/min. 11 min after T, BP and HR had decreased (p less than 0.05) from 133 +/- 6 to 103 +/- 7 mm Hg and from 134 +/- 4 to 104 +/- 6 beats/min, respectively. Ouabain did not influence these decreases in BP and HR. CGS (10 or 20 mg/kg, i.v.) increased (p less than 0.05) the time to ouabain-induced arrhythmia (AR) and D. The magnitude of the protection appeared to be similar to that afforded by T. R given prior to CGS (20 mg/kg, i.v.) also increased the time to ouabain-induced AR and D while 6-OHDA increased the time to AR. The CGS protection against ouabain-induced AR was still present in animals pretreated with R or 6-OHDA. This indicates that the antiarrhythmic affect is not dependent upon adrenergic neuronal blockade.  相似文献   
997.
998.
Pulmonary and cardiovascular function, oxygen delivery and mortality were compared in endotoxemic pigs spontaneously breathing air and with continuous i.v. infusion of ketamine anesthesia (n = 10) or the equianesthetic dose of metomidate (n = 10). Continuous 6-hour i.v. infusion of endotoxin caused profound pulmonary and cardiovascular derangement in both groups. Cardiac output, mean arterial blood pressure, oxygen delivery and base excess were significantly higher and pulmonary vascular resistance significantly lower from 2-3 hours onwards in the ketamine than in the metomidate group. Six-hour survival was 6/10 and 1/10 in the respective groups. Death was presumably due to insufficient oxygen delivery in relation to tissue demand, reflected in the metomidate group's low base excess values. Control, non-stressed pigs showed no notable physiologic changes with either anesthetic regimen. The study demonstrated the importance of the type of anesthesia in stressful endotoxemic animal models. Although extrapolation of animal data requires great caution, the results may favor use of ketamine over etomidate (the clinical analogue of metomidate) in septic shock states requiring surgical intervention.  相似文献   
999.
1000.
Two cases are presented in which the cause of small-bowel obstruction was enterolith originating in jejunal diverticula.  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