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   819篇
  免费   36篇
  国内免费   9篇
耳鼻咽喉   4篇
儿科学   48篇
妇产科学   36篇
基础医学   77篇
口腔科学   75篇
临床医学   65篇
内科学   181篇
皮肤病学   12篇
神经病学   10篇
特种医学   137篇
外科学   98篇
综合类   12篇
预防医学   25篇
眼科学   2篇
药学   39篇
  1篇
中国医学   6篇
肿瘤学   36篇
  2021年   9篇
  2018年   7篇
  2016年   4篇
  2015年   5篇
  2014年   13篇
  2013年   17篇
  2012年   20篇
  2011年   15篇
  2010年   29篇
  2009年   31篇
  2008年   29篇
  2007年   31篇
  2006年   23篇
  2005年   14篇
  2004年   9篇
  2003年   19篇
  2002年   12篇
  2001年   21篇
  2000年   13篇
  1999年   21篇
  1998年   28篇
  1997年   34篇
  1996年   41篇
  1995年   40篇
  1994年   36篇
  1993年   19篇
  1992年   8篇
  1991年   14篇
  1990年   12篇
  1989年   27篇
  1988年   31篇
  1987年   27篇
  1986年   20篇
  1985年   23篇
  1984年   19篇
  1983年   14篇
  1982年   8篇
  1981年   9篇
  1980年   14篇
  1979年   5篇
  1978年   6篇
  1977年   10篇
  1976年   7篇
  1975年   7篇
  1973年   7篇
  1972年   5篇
  1971年   6篇
  1970年   9篇
  1969年   4篇
  1965年   4篇
排序方式: 共有864条查询结果,搜索用时 375 毫秒
91.
92.
PURPOSE: Based on the findings of a previous study of pressure differentials in the external and internal urinary sphincters during electroejaculation we determined whether semen retrieval in men with spinal cord injury would be improved by interrupting current delivery during electroejaculation. MATERIALS AND METHODS: We tested continuous versus interrupted current delivery in the same group of 12 men with spinal cord injury. Patients underwent a mean of 4 randomly assigned continuous or interrupted trials 4 to 8 weeks apart. Antegrade and retrograde semen parameters were analyzed per trial. Multiple trials of each method per patient were averaged and semen parameters by the continuous and interrupted methods were compared. RESULTS: Interrupted delivery resulted in significantly greater mean antegrade volume versus continuous delivery (2 versus 0.9 cc). In this antegrade fraction mean total sperm count and mean total motile sperm was higher for interrupted (130 million and 35 million) versus continuous (79 million and 26 million, respectively) delivery. The mean retrograde total sperm count was 4-fold higher for continuous (120 million) versus interrupted (29 million) delivery. In the total ejaculate of the combined antegrade and retrograde fractions the mean total sperm count and mean total motile sperm were not significantly different for the 2 methods. CONCLUSIONS: Each method resulted in a similar mean total sperm count and total motile sperm in the total ejaculate but a higher proportion of sperm was found in the antegrade fraction using the interrupted method. We recommend interrupted current delivery as the technique of choice when electroejaculation is performed to obtain sperm for fertilization.  相似文献   
93.
Twenty-six patients over the age of 50 years with proven iron deficiency anaemia were identified, investigated and followed up in general practice over a five-year period. The anaemia was symptomatic in 50% of patients but only 20% had symptoms related to the gut. Faecal occult blood testing was positive in five patients only and negative tests occurred in three patients with significant disease, including one caecal carcinoma. All patients agreed to oesophagogastroduodenoscopy (OGD) and fibreoptic sigmoidoscopy carried out on the same occasion. In eight patients, significant abnormalities were found on OGD and in two patients on sigmoidoscopy. Four patients declined barium enema examinations, two of whom had significant OGD abnormalities. Barium enema examination of the other 22 patients showed polyposis of the colon and a caecal carcinoma and initially missed one carcinoma of the caecum which was found subsequently. The likelihood of finding significant disease in iron-deficient patients over 50 years of age is high and should be assumed to be due to blood loss into the gut. Investigation by OGD, sigmoidoscopy and barium enema in the first instance seems warranted and is a condition that can be safely managed by the GP. (Br J Clin Pract 1997; 51(2) : 78-80)  相似文献   
94.
Summary Bone loss was confirmed after 90 days in 50 6-month-old male Sprague Dawley rats that were sham-operated or orchidectomized (ORX). In this study, we have shown that dried plum (DP) has potent effects on bone in terms of bone mass, microarchitecture, and strength in osteopenic male rats. Although these changes may be mediated through the suppression of bone resorption, the fact that the restoration in some of the bone structural and biomechanical parameter shares some similarities with parathyroid hormone (PTH) should not be overlooked. Further investigation is needed on a mechanistic level to clarify the influence of DP on bone metabolism. Introduction This study was designed to investigate the extent to which DP reverses bone loss in osteopenic ORX rats and to compare its effects to PTH. Materials and methods Fifty, 6-month-old male Sprague Dawley rats were sham-operated or ORX, and bone loss was confirmed after 90 days. The ORX groups were assigned to control (AIN-93M) diet, 25% DP diet, or PTH (80 μg/kg) for 90 days. Results DP induced an 11% increase in vertebral and femoral BMD compared to ORX-controls. BMD in the PTH-treated group was increased by 20.7% (vertebra) and 17.9% (femur). Vertebral trabecular bone volume (BV/TV) and number were increased by DP and trabecular separation was decreased compared to controls, which were similar to PTH. Alterations in trabecular bone of the femur were similar to those in the vertebra, but DP did not restore BV/TV to the same extent. Cortical thickness was improved by DP and further enhanced by PTH. DP tended to decrease urinary deoxypyridinoline and calcium, but did not alter alkaline phosphatase or osteocalcin. Conclusion We conclude that though the degree of improvement was not equivalent to PTH with regard to all parameters, DP reverses bone loss due to ORX and the mechanisms should be further investigated.  相似文献   
95.
The amino acid sequence of guinea pig MSEL-neurophysin has been determined using tryptic peptides derived from the performic acid-oxidized protein and staphylococcal proteinase peptides obtained from the reduced-carboxamidomethylated neur-ophysin. Guinea pig MSEL-neurophysin consists of a 93-residue polypeptide chain that shows 12 substitutions and 2 deletions when compared to bovine MSEL-neurophysin. It displays the highest number of variations among known mammalian MSEL-neurophysins. These variations are mainly found in the C-terminal region (residues 88–93). Moreover guinea pig MSEL-neurophysin, like rat homologous protein, exhibits substitutions in positions 2, 5, 29 and 81 and lacks an arginine in the penultimate position. Comparison between eight mammalian MSEL-neurophysins reveals a highly conserved region (residues 1 to 88) and a hypervariable region (residues 89 to 93/95). On the other hand the eight species examined are endowed with arginine vasopressin except pig, which has a lysine vasopressin. In the vasopressin-MSEL-neurophysin precursor, the hormonal moiety and the MSEL region of neurophysin (residues 1–9) are encoded by a common exon in ox, rat and man; it can be concluded that this exon is evolutionarily conservative in contrast to the one encoding the C-terminal region of MSEL-neurophysin.  相似文献   
96.
Erythropoietin kinetics in rats: generation and clearance   总被引:1,自引:0,他引:1  
Steinberg  SE; Garcia  JF; Matzke  GR; Mladenovic  J 《Blood》1986,67(3):646-649
Detailed studies to analyze the early events of erythropoietin (Ep) secretion and clearance were performed in a rat model using a double antibody radioimmunoassay. Ep clearance was determined following intravenous injection of 1 mL of Ep-rich plasma, 1,080 mU/mL, obtained from phlebotomized rats. Analysis revealed a disappearance curve that conformed to a two-compartment model with an alpha half-life t1/2 of 3.6 minutes and a beta t1/2 of 86 minutes. The volume of distribution was similar to the calculated plasma volume. In anephric animals, there was no change in the plasma clearance rate or the volume of distribution. Rapid Ep secretion was elicited by a single 15 mL/kg phlebotomy (hematocrit decrement 45% to 30%), so that levels reached 20 to 30 times baseline (524 +/- 76 v 24 +/- 7 mU/mL) at five hours, whereas they plateaued for at least 33 hours. The increase in the rate of secretion was geometric, from 9.9 mU/h baseline secretion to 429 mU/h. These data identify a very sensitive and rapidly responsive system for Ep modulation in the rat.  相似文献   
97.
Clinicians need standard terminology to communicate effectively about remaining autonomic function in persons after spinal cord injury. This article illustrates the development of standard nomenclature that describes the impact of injury on sexual functioning. A standard anatomic diagnosis and a secondary means of describing the presence of male and female sexual dysfunction, genital arousal, and orgasmic function are discussed.  相似文献   
98.
99.
100.
Linkage analysis was performed on a large pedigree with an autosomal dominant platelet disorder and a striking propensity in affected family members to develop hematologic malignancy, predominantly acute myelogenous leukemia. We report the linkage of the autosomal dominant platelet disorder to markers on chromosome 21q22. Four genetic markers completely cosegregate with the trait and yield maximum logarithm of difference scores ranging from 4.9 to 10.5 (theta = .001). Two flanking markers, D21S1265 and D21S167, define a critical region for the disease locus of 15.2 centimorgan. Further analysis of this locus may identify a gene product that affects platelet production and function and contributes to the molecular evolution of hematologic malignancy.  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