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   1264326篇
  免费   94870篇
  国内免费   1734篇
耳鼻咽喉   16324篇
儿科学   41007篇
妇产科学   34981篇
基础医学   189454篇
口腔科学   34754篇
临床医学   117784篇
内科学   247842篇
皮肤病学   27296篇
神经病学   101941篇
特种医学   46785篇
外国民族医学   265篇
外科学   178867篇
综合类   25750篇
现状与发展   3篇
一般理论   568篇
预防医学   104673篇
眼科学   28047篇
药学   92597篇
  7篇
中国医学   2022篇
肿瘤学   69963篇
  2018年   13543篇
  2017年   10394篇
  2016年   11331篇
  2015年   13087篇
  2014年   18008篇
  2013年   27488篇
  2012年   37592篇
  2011年   39986篇
  2010年   23069篇
  2009年   22262篇
  2008年   37769篇
  2007年   40401篇
  2006年   39990篇
  2005年   39123篇
  2004年   37579篇
  2003年   35985篇
  2002年   34913篇
  2001年   56098篇
  2000年   57092篇
  1999年   48136篇
  1998年   13411篇
  1997年   12227篇
  1996年   12650篇
  1995年   11916篇
  1994年   11113篇
  1993年   10403篇
  1992年   38204篇
  1991年   37681篇
  1990年   36457篇
  1989年   35262篇
  1988年   32697篇
  1987年   32035篇
  1986年   30533篇
  1985年   28796篇
  1984年   21945篇
  1983年   19198篇
  1982年   11366篇
  1981年   10323篇
  1979年   20945篇
  1978年   15396篇
  1977年   12794篇
  1976年   11848篇
  1975年   12816篇
  1974年   15591篇
  1973年   15367篇
  1972年   14518篇
  1971年   13558篇
  1970年   12795篇
  1969年   12067篇
  1968年   11231篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
961.
Three dimensional (3D) phase contrast angiograms contain velocity data, which is discarded after the reconstruction of the projections. In extension to earlier work on velocity quantification with ungated 2D phase data, this paper shows that a useful estimate of the average velocity and flow rate can be extracted from ungated 3D phase contrast angiograms. Simulations and experiments in a phantom and in vivo were performed. For pulsatile flow and strong spin saturation, an over-estimation of the flow rate at the net in-flow end of the imaging volume and underestimation at the net out-flow end was observed. Imaging at lower RF tip angles yielded flow rates close to the correct value within the entire imaging volume. In contrast to ungated 2D experiments, the flow rates determined by repeated 3D experiments showed no variation.  相似文献   
962.
963.
964.
A variety of substances have been used at laminectomy sites to prevent postoperative epidural scarring. Free grafts of autologous subcutaneous fat are commonly used both clinically and experimentally. The free fat grafts usually survive, but decrease in size by about 50%. Postoperatively, subcutaneous seroma has been observed with the use of fat grafts, as well as recurrent symptoms of neural compression by the graft that required additional operations. When compared to the use of free grafts after laminectomy in dogs, Vicryl mesh produced slightly more scarring, but consistently less than that observed in control animals. The Vicryl mesh was resorbed by a minimal chronic inflammatory response over about 45 days. Seven of 11 fat-grafted zones showed signs of necrosis, at times with a greater collection of inflammatory cells than that associated with the Vicryl mesh. Of the 4 fat-grafted zones that showed good survival, 2 had gross evidence of neural compression. No surgical zone treated with Vicryl mesh exhibited evidence of neural compression. In view of these results, the use of Vicryl mesh at laminectomy sites may be a safer method of limiting postoperative epidural scar formation.  相似文献   
965.
Twelve patients in whom radial artery infections developed after catheterization in an intensive care unit over a 2-year period were reviewed. The incidence of local infection was 0.4%. An increased risk of infection was associated with prolonged catheterization (greater than 4 days). Aneurysms developed in five patients. Signs of septic emboli were present in two patients, including Osler's nodes, Janeway's lesions, and fingertip infarcts. In 6 of the 12 patients, the radial artery infection resolved with antibiotic treatment alone. The five patients with infected aneurysms were treated successfully with antibiotics and surgical excision. The radial artery was reconstructed by use of a vein graft in one patient. We believe that patients not responding promptly to antibiotics or patients with infected aneurysms are best treated by surgical excision.  相似文献   
966.
967.
Studies were performed to evaluate the effect of unilateral nephrectomy on glycerol-induced acute renal failure in the rat. Normal rats were subjected to either sham uninephrectomy (n = 43) or right uninephrectomy (n = 53). The functional compensation of the remaining kidney was followed after 1 and 2 weeks. Fourteen days after the operation, acute renal failure was induced by injection of 50% glycerol solution to both groups. Uninephrectomised rats developed a lesser degree of renal failure compared to sham-operated rats. Forty-eight hours after glycerol injection, PCr of uninephrectomised rats was 260 +/- 22 mumol/l compared with 338 +/- 26 in sham-operated rats (P less than 0.0125) and CCr in uninephrectomised rats was greater (0.10 +/- 0.01 ml/min vs 0.07 +/- 0.01; P less than 0.025) in sham rats. Uninephrectomised rats had significantly greater recovery of CCr compared to sham rats at 24 h (20.1% +/- 2.3 vs 13.1% +/- 2.2, P less than 0.025) and at 48 h (32.1% +/- 3.3 vs 19.2% +/- 3.3, P less than 0.005) after glycerol injection. FENa was significantly less in uninephrectomised rats: 0.96 +/- 0.16% vs 2.25 +/- 0.05% (P less than 0.025) in sham rats 24 h post glycerol. Urinary excretion of K+ was greater in rats following uninephrectomy compared to sham rats both after 24 h and 48 h post glycerol (P less than 0.01), accompanied by lower plasma potassium (P less than 0.05). A correlation coefficient (r) of 0.793 was observed between urinary potassium excretion rate and percentage recovery of CCr.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
968.
Laparoscopic cholecystectomy (LC) using electrocoagulation was successfully performed in 56 out of 58 selected patients. Cholangiography was performed in 53 patients. Six patients had common duct stones; five were unsuspected preoperatively. After the gallbladder was removed, three patients underwent open common duct exploration. In another five cases, anatomical anomalies were discovered. Cholangiography performed via the cystic duct before any structures are divided can prevent the most serious complication--common duct injury. Cholangiography should be attempted on all patients undergoing LC.  相似文献   
969.
Early changes in the morphology of the gastric mucosa after the skin had been burned were studied using a standardised model in rats. A full thickness burn was inflicted by exposing about 20% of the total body surface area to hot water (99 degrees C) for 10 s. Intragastric acidity was kept at pH 1.0 or pH 7.4 in six experimental groups of eight rats. Rats were subjected to burns with the stomach irrigated at pH 1.0 or pH 7.4. Parallel groups received fluid replacement with a solution of human albumin, and two uninjured groups served as controls. Lesions of the gastric mucosa were measured by planimetry of photographs, and light microscopy was used for histological examination. At an intragastric pH of 1.0, the burned rats developed mucosal erosions covering an average of 13% of the total glandular mucosa; the remaining groups had only minimal mucosal lesions. Erosions of the gastric mucosa after the skin had been burned could be prevented in two ways--either by establishing an alkaline (pH 7.4) milieu in the gastric lumen, or by replacing sufficient fluid to maintain aortic blood pressure at the pre-experiment level. Fluid replacement prevented mucosal erosions even if the intragastric pH was kept at 1.0. Thus both luminal acidity and local tissue blood flow are possible mechanisms for gastric epithelial damage following burns of the skin.  相似文献   
970.
This study reports our experience in 6 cases of acute idiopathic scrotal oedema. Although children were the primary targets, this pathologic condition was also encountered in adults. Specific diagnosis of acute idiopathic scrotal oedema, opposed to other causes of scrotal swelling, is based on history, an objective examination, velocimetric Doppler exam and echography. Correct diagnosis is important in order to avoid unnecessary surgery. We are inclined to consider acute idiopathic scrotal oedema as an allergic disorder and recommend a follow-up within two days.  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