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   3580911篇
  免费   263670篇
  国内免费   8725篇
耳鼻咽喉   48909篇
儿科学   118601篇
妇产科学   99819篇
基础医学   503506篇
口腔科学   102170篇
临床医学   325158篇
内科学   697086篇
皮肤病学   82631篇
神经病学   293739篇
特种医学   139399篇
外国民族医学   1129篇
外科学   535979篇
综合类   79299篇
现状与发展   6篇
一般理论   1400篇
预防医学   278661篇
眼科学   81773篇
药学   265094篇
  10篇
中国医学   6969篇
肿瘤学   191968篇
  2018年   37606篇
  2017年   29139篇
  2016年   33507篇
  2015年   38109篇
  2014年   52423篇
  2013年   79475篇
  2012年   105696篇
  2011年   111678篇
  2010年   67171篇
  2009年   64376篇
  2008年   105105篇
  2007年   111417篇
  2006年   113275篇
  2005年   109091篇
  2004年   105930篇
  2003年   101996篇
  2002年   98871篇
  2001年   167389篇
  2000年   172025篇
  1999年   145570篇
  1998年   42009篇
  1997年   37549篇
  1996年   37575篇
  1995年   36488篇
  1994年   33779篇
  1993年   31730篇
  1992年   116018篇
  1991年   112589篇
  1990年   109328篇
  1989年   105900篇
  1988年   97661篇
  1987年   95942篇
  1986年   90737篇
  1985年   86984篇
  1984年   65118篇
  1983年   55663篇
  1982年   32971篇
  1981年   29629篇
  1979年   59674篇
  1978年   41848篇
  1977年   35548篇
  1976年   33153篇
  1975年   35344篇
  1974年   42329篇
  1973年   40370篇
  1972年   37727篇
  1971年   35249篇
  1970年   32468篇
  1969年   31057篇
  1968年   28385篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Despite being of fundamental importance, the late results of major arterial reconstruction rarely have been documented throughout a large metropolitan area. In this study of 932 patients entered into the computer registry of the Cleveland Vascular Society, 19 surgeons representing 13 community hospitals and referral centers in Cleveland and Akron report the intermediate-term outcome during a mean interval of 35 months after infrainguinal lower extremity revascularization performed in northeastern Ohio from 1978 through 1982. Operative risk (5%), the early amputation rate (7%), and actuarial 5-year survival (48% to 55%) for patients with rest pain or tissue necrosis were significantly worse (p less than 0.05) than comparable figures (0.6%, 0%, and 77%, respectively) for others who underwent procedures for disabling claudication. Although both materials had similar success above the knee, the cumulative 3-year patency rate of autogenous vein bypass to the distal popliteal (69% to 88%; p less than 0.05) and tibioperoneal arteries (43%; 0.05 less than p less than 0.1) was superior to the results of polytetrafluoroethylene grafts (32% to 50% and 19%, respectively). Moreover, polytetrafluoroethylene grafts required reoperations at three times the rate of vein grafts to maintain limb salvage.  相似文献   
992.
The use of autologous blood transfusion in cardiac surgery is still controversial. This study was prospectively designed to evaluate the haemodynamic and haematological benefits of this method, with special attention to its impact on reducing bank blood requirements. Between November 1983 and October 1984, 160 patients underwent cardiac surgery with extracorporeal circulation and were randomly assigned to two groups: group I (81 patients) was the control group and group II (79 patients) received autologous transfusion following extracorporeal circulation. Blood was withdrawn immediately after the induction of anaesthesia via a jugular catheter and stored in CPD solution at room temperature. The volume of blood removed was replaced with gelatin solutions; after bypass, blood was returned to the patient. There was no difference in systolic, diastolic or mean blood pressures between the two groups. Right atrial pressure and heart rate were not statistically different in both groups. Myocardial perfusion and myocardial oxygen consumption remained unchanged in group II compared with group I. Complete haematological evaluation was carried out before and during bypass, and thereafter daily for the first twelve days of the postoperative period. There was no significative difference between the two groups in platelet counts, fibrinogen levels, prothrombin and partial thromboplastin times. During extracorporeal circulation, mean haematocrit was 22.9 +/- 0.4% in group II and 25.3 +/- 0.5% in group I (p less than 10(-3)). The mean haematocrit time course was similar in both groups during the postoperative period and returned to preoperative value at discharge.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
993.
994.
Summary Short traumatic strictures of the membranous urethra can be repaired by excision and end-to-end urethroprostatic anastomosis. Long membranous or bulbomembranous strictures with or without associated periurethral fibrosis, abscess or urinary fistulae require substitution urethroplasty. Tubed full-thickness skin grafts have a poor chance of survival in such circumstances. Scrotal flaps are hairy, but the penile/preputial island flap, which is relatively hairless, is ideal for such reconstructions in one stage. Difficult perineal exposure led to the development of the transpubic and the abdominoperineal routes. Modification of the incision for perineal prostatectomy by dividing the posterior part of the urogenital diaphragm in the midline up to the urethra improves the exposure so that almost all such reconstructions can be done by the perineal route. A total of 21 cases are reviewed. Flap survival is 100%, but stenosis or restricture at the anastomotic sites can occur as a result of faulty technique. These can be treated by internal urethrotomy or excision and reanastomosis.  相似文献   
995.
996.
997.
998.
M Lorenzi  J A Nordberg  S Toledo 《Diabetes》1987,36(11):1261-1267
There is evidence suggesting that the diabetic state adversely affects replication of certain cell populations. We document that exposure to high ambient glucose (20 mM) induces delay in various phases of the cell cycle of human endothelial cells in primary culture. Cells in S phase were labeled with bromodeoxyuridine (an analogue of thymidine), and the cell-cycle position of the labeled cohort was analyzed by flow cytometry at successive time points. The movement of cells exposed to high glucose for 7-8 days was retarded both in S and G2 phases so that the increase in bromodeoxyuridine-positive cells over 24 h was 1.6-fold, versus 2.0-fold in control cultures. In experiments in which mitotic arrest with vinblastine was used to investigate the movement of cells out of G1 phase without interference from reentering cells, depletion of the G1 compartment was significantly inhibited in cultures grown in high glucose. The effects of chronic high glucose on cell cycle occurred while total protein synthesis was not diminished. Acute exposure to high glucose had no effect on cell-cycle traversal or cell generation time. Cell-cycle abnormalities observed in this study may relate to the DNA damage we have previously observed in endothelial cells exposed to high glucose and, if occurring in vivo, could be of pathogenetic importance for the vascular lesions and teratogenicity of diabetes.  相似文献   
999.
Failure of genetically selected miniature swine to model NIDDM   总被引:2,自引:0,他引:2  
Ten young adult miniature swine from a line reported to be genetically selected for glucose intolerance and eight normal controls were obtained from Colorado State University. They were consecutively exposed to 4 mo of a high-fiber, low-fat standard swine diet; 4 mo of a high-sucrose, high-fat, low-fiber diabetogenic diet; and 4 mo of excess diabetogenic diet for obesification. Results of oral glucose tolerance and intravenous insulin tolerance tests conducted at the end of each regimen were compared. Hyperglycemia was not observed in any animals after any manipulation. Insulin sensitivity was also not influenced by diet. We conclude that F7 low-K miniature swine from this colony fail to model human non-insulin-dependent diabetes.  相似文献   
1000.
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