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   379228篇
  免费   24185篇
  国内免费   2811篇
耳鼻咽喉   5184篇
儿科学   8201篇
妇产科学   10085篇
基础医学   53132篇
口腔科学   11782篇
临床医学   30095篇
内科学   78322篇
皮肤病学   8551篇
神经病学   27190篇
特种医学   13938篇
外国民族医学   82篇
外科学   60654篇
综合类   9954篇
现状与发展   1篇
一般理论   64篇
预防医学   17434篇
眼科学   9440篇
药学   30991篇
  1篇
中国医学   2194篇
肿瘤学   28929篇
  2021年   2616篇
  2019年   2723篇
  2018年   4519篇
  2017年   3440篇
  2016年   3526篇
  2015年   4022篇
  2014年   5702篇
  2013年   7382篇
  2012年   10025篇
  2011年   10206篇
  2010年   6198篇
  2009年   5852篇
  2008年   9469篇
  2007年   10293篇
  2006年   10209篇
  2005年   9264篇
  2004年   8784篇
  2003年   8512篇
  2002年   8188篇
  2001年   28243篇
  2000年   28779篇
  1999年   23660篇
  1998年   5164篇
  1997年   4251篇
  1996年   3832篇
  1995年   3478篇
  1994年   3110篇
  1993年   2845篇
  1992年   16054篇
  1991年   14817篇
  1990年   14161篇
  1989年   13961篇
  1988年   12581篇
  1987年   12069篇
  1986年   11102篇
  1985年   10330篇
  1984年   6915篇
  1983年   5599篇
  1982年   2718篇
  1979年   5479篇
  1978年   3347篇
  1977年   2971篇
  1975年   2648篇
  1974年   3064篇
  1973年   2867篇
  1972年   2832篇
  1971年   2776篇
  1970年   2517篇
  1969年   2545篇
  1968年   2251篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The pharmacokinetics of 1-(tetrahydro-2-furanyl)-5-fluorouracil (FT) and its conversion into 5-fluorouracil (FUra) in liver tissue were studied in ten patients with hepatocellular carcinoma (HCC). The plasma concentration of FT after its intravenous injection (dosage: 800 mg) was computerfitted to a bi-exponential function (C = Ae-alpha t + Be-beta t), indicating a two-compartment disposition. The pharmacokinetic parameters did not significantly differ between the five patients with, and the five without cirrhosis of the liver. The plasma concentrations of FUra likewise showed no significant difference between the two groups. The rates of FT degradation in the liver tissue homogenate were similar for four of the patients with cirrhosis (0.10 +/- 0.05 mumol/g liver protein/30 min) and four of those without it (0.13 +/- 0.05). The rates of cytochrome P-450-dependent FUra formation in the microsomal fraction of liver tissue from two patients (1.1 and 1.3 nmol/mg microsomal protein/30 min) were dramatically reduced to less than half of those of two control subjects (2.4 and 2.7). The estimated rates of FUra formation in the soluble fraction (105,000 X g supernatant fraction) from the two patients (0.1 and 0.13 nmol/mg protein/30 min) were almost identical to those from the controls (0.12 and 0.14), suggesting that the rate in the soluble fraction from HCC patients may not be as strongly affected as the rate in the microsomal fraction.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
72.
73.
A case of Ullrich disease was presented. The patient was a 3-year-old girl with torticollis, generalized muscle weakness and acroatonia since birth. High-arched palate, protruded calcaneus, and mild contracture of proximal joints were also recognized. Intellectual development was normal. Serum level of CPK was slightly increased. In histological and histochemical examinations of quadriceps femoris muscle, proliferated connective tissue, marked variation in the muscle fiber diameter, and a lot of degenerated and regenerated fibers were recognized. Minimal injury easily causes subcutaneous hemorrhage, but no abnormality was found in the structure of collagen.  相似文献   
74.
75.
76.
BACKGROUND: Stress can aggravate the allergic inflammation, but determinants of disturbed immune regulation are largely unknown. OBJECTIVE: To determine systemic immunological, local inflammatory and functional airway responses to stress in healthy and atopic individuals. METHODS: Forty-one undergraduate students, 22 with allergy of whom 16 had asthma, and 19 healthy controls, were studied in a low-stress period and in association with a large exam. Subjects completed questionnaires on stress and health behaviours, underwent lung function tests, bronchial methacholine challenge, measurements of exhaled nitric oxide and urine cortisol. Blood cells were phenotyped, and cytokines from mononuclear blood cells were analysed. RESULTS: Perceived stress and anxiety increased in both groups during the exam period while cortisol increased only in the atopy group. Cytokine production decreased broadly in response to stress in both groups, which was paralleled by an increase in the proportion of regulatory T cells (CD4(+)CD45RO(+)CD25(bright)). Interestingly, atopic individuals, but not controls, reacted with a decreased T-helper type 1/T-helper type 2 (Th1/Th2) ratio and a decrease in natural killer (NK) cell numbers in response to stress. In control subjects only, exhaled nitric oxide decreased and forced expiratory volume in one second increased during stress. CONCLUSION: Atopic and non-atopic subjects shared some immune changes in response to stress, such as a dramatic decline in cytokines and an increase in the number of regulatory T cells in peripheral blood. However, other stress-induced immune changes were unique to atopic individuals, such as a skewed Th1/Th2 ratio and reduced NK cell numbers, indicating that some pathogenic mechanisms in atopics may be more strongly affected by stress than others.  相似文献   
77.
78.
Paradoxical embolism, describing the passage of venous or right-sided cardiac thrombus into the arterial or systemic circulation through patent foramen ovale, is an uncommon cause of acute arterial occlusion. Here, we report acute Leriche syndrome in a young woman attributable to paradoxical embolism. Ischaemia, patent foramen ovale, and venous thrombosis were the triad of evidence for paradoxical embolism.  相似文献   
79.
BACKGROUND: Although many histopathologic factors in squamous cell carcinoma of the tongue predict the prognosis, the major predictive factors have not been identified clearly. This study analyzed the prognostic value of the histologic grade at the deep invasive front of tongue squamous cell carcinoma. METHODS: The clinicopathologic features of 124 consecutive patients seen between January 1985 and December 1999 with previously untreated squamous cell carcinoma of the tongue were reviewed. Their mean age was 58.5 years (range: 23-90) and the male-female ratio was 1.8: 1 (79 men and 45 women). There were 41, 40, 30, and 13 cases at stage I to stage IV, respectively. The clinicopathologic factors, especially the histologic grade at the deep invasive front (invasive front grade, IFG), were analyzed to determine factors predicting prognosis. RESULTS: The 5-year disease-free survival rate of the patients treated with curative aim only was 66.7%. Clinicopathologic factors significantly associated with the prognosis were T classification, tumor size, stage classification, tumor depth, macroscopic appearance, cervical lymph node metastasis (nodal metastasis), microvascular invasion, and IFG. In a multivariate analysis, patients with tumor depth >/=4 mm, IFG >/=8 points, and nodal metastasis had a reduced disease-free survival and IFG >/=11 points had a predictive value for nodal metastasis (odds ratio: 7.34; P = 0.0019). CONCLUSION: This study found that a high IFG malignancy score had a high prognostic value for squamous cell carcinoma of the tongue.  相似文献   
80.
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