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   538篇
  免费   30篇
  国内免费   1篇
耳鼻咽喉   3篇
儿科学   23篇
妇产科学   19篇
基础医学   73篇
口腔科学   19篇
临床医学   45篇
内科学   115篇
皮肤病学   4篇
神经病学   55篇
特种医学   72篇
外科学   33篇
综合类   13篇
预防医学   49篇
眼科学   1篇
药学   16篇
中国医学   3篇
肿瘤学   26篇
  2021年   3篇
  2019年   8篇
  2018年   5篇
  2017年   7篇
  2016年   7篇
  2015年   15篇
  2014年   19篇
  2013年   23篇
  2012年   37篇
  2011年   20篇
  2010年   14篇
  2009年   23篇
  2008年   18篇
  2007年   35篇
  2006年   24篇
  2005年   16篇
  2004年   13篇
  2003年   19篇
  2002年   14篇
  2001年   9篇
  2000年   7篇
  1999年   5篇
  1998年   28篇
  1997年   14篇
  1996年   20篇
  1995年   14篇
  1994年   9篇
  1993年   17篇
  1992年   3篇
  1991年   7篇
  1990年   5篇
  1989年   10篇
  1988年   6篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   4篇
  1980年   8篇
  1978年   3篇
  1976年   4篇
  1973年   2篇
  1959年   2篇
  1958年   2篇
  1957年   6篇
  1956年   4篇
  1955年   5篇
  1954年   5篇
  1950年   2篇
排序方式: 共有569条查询结果,搜索用时 171 毫秒
1.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence.  相似文献   
2.
3.
Isolated sperm from normo-, oligo- and astheno-spermic men were incubated for 20 h in medium supplemented with 8% heat-inactivated or untreated human serum, and in medium with heated or untreated serum deficient in complement factor C3. Before and after incubation, sperm motility was assessed by means of a computer-assisted semen analyser. The results did not show significant differences between the motility of sperm incubated in heated or untreated serum. It is concluded that heating of homologous serum is not necessary for preserving sperm motility and in some cases may even be disadvantageous.  相似文献   
4.
Image-directed percutaneous biopsies with a biopsy gun   总被引:3,自引:0,他引:3  
Core tissue for histologic study is believed by many pathologists to be more diagnostic than material from needle aspiration. Recently, a biopsy "gun" has been introduced, which simplifies core biopsies. With this device, 182 biopsies of multiple anatomic sites were performed with ultrasonic, computed tomographic, and fluoroscopic guidance and 18-gauge needles. High-quality histopathologic specimens were obtained in 177 of the biopsies, and diagnostic target tissue was obtained in 167. Only three significant complications occurred: one bleeding complication that required transfusion and two cases of pneumothorax that necessitated placement of chest tubes. The biopsy gun eliminated the disjointed movements of conventional "skinny" needle biopsies, and none of the samples demonstrated significant "crush" artifact or obscuring blood, problems that are commonly associated with manual biopsy techniques. Patient discomfort was decreased with this system compared with that of manual biopsies, and the total procedure time was reduced. Because of these distinct advantages, the authors now use the biopsy gun exclusively for all percutaneous biopsies and recommend that other institutions consider the use of this biopsy method.  相似文献   
5.
Exercise in the heat has detrimental effects on circulation that might negatively influence endurance performance. If blood is diverted away from the inspiratory muscles to the skin during exercise in the heat, exercise-induced inspiratory muscle fatigue might be exacerbated. Thus, we hypothesised that prolonged heavy endurance exercise in the heat would impair exercise performance and exacerbate inspiratory muscle fatigue compared to exercise in a thermo-neutral environment. Using a crossover design, seven male endurance trained subjects [mean (SEM) maximum oxygen uptake = 62.2 (1.5) ml·kg–1·min–1] were assigned at random to either a group that exercised in the heat at an ambient temperature of 35°C (H) or a group that exercised in the cool at 15°C (C). Maximum inspiratory mouth pressure at zero flow (P 0), pressure normalised maximum relaxation rate (MRR/P 0), time constant for the pressure decay (), and maximum inspiratory flow at 30% P 0 ( 30) were assessed immediately before and reassessed within 2, 30, and 60 min of completing a pre-loaded time trial [40 min at 65% peak power, plus ~30 min time trial] on a cycle ergometer . Group H completed the time trial 432 (135) s slower than group C [2,285 (180) vs 1,852 (122) s, respectively; =24 (8)%, P=0.0094]. Repeat measurements within 2 min post-exercise revealed significant declines in P 0, MRR/P 0, , and 30 from baseline values, but no between-group differences were observed. In conclusion, heavy sustained exercise in the heat impaired subsequent time-trial performance but did not exacerbate inspiratory muscle fatigue in endurance-trained subjects.  相似文献   
6.
7.
目的观察去甲硫氨酸全肠外营养对大鼠血清氨基酸谱等的影响.方法 Wistar大鼠24只,随机分为含甲硫氨酸(+MetTPN,n=12)和去甲硫氨酸全肠外营养2组(-MetTPN,n=12),分别给予相应的TPN支持.治疗7d后,每组随机抽取6只大鼠处死,检测血清FAA(HPLC法)、肝肾功能和全血常规,同时作心、肺、肝、肾组织病理学检查.两组其余大鼠继续原TPN治疗,观察生存期.结果 -MetTPN组大鼠血清游离Met、Cys明显降低,Asp、Glu、Ser等显著增高;大鼠体重下降;血清总蛋白和白蛋白水平下降;血常规和肾功能未见明显异常;组织学检查见肝细胞轻度肿胀,细胞核仁增粗,心肺肾未见明显异常;平均生存18d.对照组上述检查未见异常,除一只大鼠因导管并发症于TPN第16d死亡,其余大鼠全部存活.结论 -MetTPN一周可致大鼠血清游离Met、Cys明显降低和Asp、Glu、Ser等显著增高,及轻度肝功能改变;随着-MetTPN时间延长,出现严重的代谢紊乱和器官功能障碍导致死亡.  相似文献   
8.
To determine whether self-reported risk and protective behaviors, expectations, and attitudes are more similar among African-American early adolescents within a community-based friendship group than across groups, a cross-sectional study was conducted among 382 African-American youth 9 through 15 years of age forming 76 community-based groups of 3 through 10 same-gender friends. Each member of the friendship group reported his/her own past involvement in nine risk behaviors (sexual intercourse, substance abuse, drug-trafficking, and other delinquent activities) and two protective behaviors (high academic performance and regular church attendance) and their expectations and feelings regarding several of these behaviors. Intraclass correlation coefficients were calculated overall and by gender and age. Members were generally more similar within friendship groups than across groups with regard to several risk behaviors and expectations including sexual intercourse and drug-trafficking. Particularly striking was the similarity among members of "junior" friendship groups (e.g., median age of youth < 11 years) of both risk and protective behaviors and expectations. The finding of enhanced similarity of risk behaviors and expectations among members within groups suggests that intervention delivery through community-based friendship groups may be a useful approach for risk prevention efforts targeting pre-adolescent African-American youth living in low-income settings.  相似文献   
9.
10.
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