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   3929518篇
  免费   293145篇
  国内免费   6743篇
耳鼻咽喉   56435篇
儿科学   124461篇
妇产科学   105522篇
基础医学   565096篇
口腔科学   112363篇
临床医学   361108篇
内科学   750607篇
皮肤病学   83421篇
神经病学   319411篇
特种医学   151304篇
外国民族医学   1277篇
外科学   590287篇
综合类   89540篇
现状与发展   13篇
一般理论   1601篇
预防医学   317308篇
眼科学   93796篇
药学   294075篇
  14篇
中国医学   7547篇
肿瘤学   204220篇
  2018年   42151篇
  2017年   31980篇
  2016年   35678篇
  2015年   40299篇
  2014年   57641篇
  2013年   87691篇
  2012年   119237篇
  2011年   126771篇
  2010年   75403篇
  2009年   71366篇
  2008年   119348篇
  2007年   127158篇
  2006年   128372篇
  2005年   124771篇
  2004年   120036篇
  2003年   115494篇
  2002年   113126篇
  2001年   175007篇
  2000年   180519篇
  1999年   152750篇
  1998年   45572篇
  1997年   40420篇
  1996年   40004篇
  1995年   38313篇
  1994年   35716篇
  1993年   33533篇
  1992年   121565篇
  1991年   118592篇
  1990年   115259篇
  1989年   111028篇
  1988年   102907篇
  1987年   101056篇
  1986年   95408篇
  1985年   91682篇
  1984年   69236篇
  1983年   59070篇
  1982年   35782篇
  1981年   32029篇
  1979年   64950篇
  1978年   46065篇
  1977年   38657篇
  1976年   36861篇
  1975年   39071篇
  1974年   47643篇
  1973年   45355篇
  1972年   42864篇
  1971年   40110篇
  1970年   37345篇
  1969年   35144篇
  1968年   32280篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
In order to assess the histological tissue changes over time around the site of implant, tissue biopsies were taken at 1 to 38 months post-implant from 54 (34 male) consenting human subjects who had received the Australian subcutaneous naltrexone-poly(DL-lactide) implant for heroin dependence. The implant consists of multiple tablets containing compressed naltrexone-poly[trans-3,6-dimethyl-1,4-dioxane-2,5-dione] (DL-lactide) loaded microspheres. Assessment of tissue samples by pathologists showed an early phase (up to 12 months post-implant) of inflammation, foreign body reaction, and fibrosis. This subsided gradually over the next 12 months until tissue returned to normal by 25+ months. Sufficient evidence was not available to conclude that the poly(DL-lactide) implant matrix was totally biodegradable within the study period. While implant material was not identified in most of the latter biopsies, its presence was noted in one biopsy at 26 months post-implant. Nevertheless the study results did demonstrate the implant's biocompatibility by the lack of inflammation, foreign body reaction, and fibrosis detected by 25+ months. It seems highly probable that surgical technique rather than the implant itself was associated with the additional finding of fat necrosis. Moderate fat necrosis was observed as a common feature of biopsies carried out during the first 6 months following implant. It subsided to mild levels over the next 18 months, and was notably absent by 25+ months. The results of the study indicated that the Australian naltrexone-poly(DL-lactide) implant is well tolerated and may have a role for use in the management of medical conditions such as heroin dependence.  相似文献   
993.
994.
995.
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   
996.
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   
997.
This study assessed the results of intensive care in elderly trauma patients and quantified the different factors involved in the final outcome. It included 116 patients, aged 65 years or more, and covered a two year period. The following parameters were obtained for each patient: age, severity of trauma (ISS and SAPS), head injury (GCS), prehospital health status (ESA), survival after three months and quality of survival. Three months after trauma, overall mortality was 45.7%. Survivors were 72.8 +/- 4.9 year old, while those that died were 75.3 +/- 7.5 year old (p = 0.01). Mean ISS was 19.7 +/- 8 and mean SAPS was 9.4 +/- 3.2. The risk of death was 3.6 (1.6 to 8.1) times greater if ISS was over 15. The same risk was 4.7 (2.1 to 11.1) times greater if SAPS was over 9. GCS was 8.8 +/- 4.4 in dead patients and 12.5 +/- 2.4 in survivors (p = 0.001). The risk of death was 10.4 (4.2 to 26.2) times greater if GCS was under 8. The final prognosis could be assessed with the following exponential model: Survival = 1/(1 + exp - (8.7 - 0.07 X age - 0.07 X ISS - 2.9 X GCS*), where GCS is equal to 0 if the real GCS was under 8, and equal to 1 otherwise. The ESA did not affect mortality. Three months after trauma, the degree of independence was the same as before in 87% of survivors. It was concluded that age and the severity of trauma were the most important factors in determining prognosis in geriatric trauma patients.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
998.
999.
1000.
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   
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