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   382405篇
  免费   24343篇
  国内免费   2847篇
耳鼻咽喉   5206篇
儿科学   8239篇
妇产科学   10115篇
基础医学   53491篇
口腔科学   11896篇
临床医学   30255篇
内科学   79121篇
皮肤病学   8611篇
神经病学   27376篇
特种医学   14009篇
外国民族医学   82篇
外科学   61486篇
综合类   9970篇
现状与发展   1篇
一般理论   64篇
预防医学   17489篇
眼科学   9490篇
药学   31194篇
  1篇
中国医学   2196篇
肿瘤学   29303篇
  2021年   2699篇
  2019年   2797篇
  2018年   4609篇
  2017年   3498篇
  2016年   3590篇
  2015年   4103篇
  2014年   5800篇
  2013年   7504篇
  2012年   10208篇
  2011年   10418篇
  2010年   6313篇
  2009年   5945篇
  2008年   9601篇
  2007年   10422篇
  2006年   10365篇
  2005年   9430篇
  2004年   8955篇
  2003年   8669篇
  2002年   8367篇
  2001年   28333篇
  2000年   28864篇
  1999年   23717篇
  1998年   5203篇
  1997年   4270篇
  1996年   3852篇
  1995年   3506篇
  1994年   3122篇
  1993年   2858篇
  1992年   16088篇
  1991年   14866篇
  1990年   14199篇
  1989年   14005篇
  1988年   12629篇
  1987年   12101篇
  1986年   11148篇
  1985年   10355篇
  1984年   6934篇
  1983年   5628篇
  1982年   2729篇
  1979年   5497篇
  1978年   3360篇
  1977年   2992篇
  1975年   2656篇
  1974年   3070篇
  1973年   2877篇
  1972年   2837篇
  1971年   2775篇
  1970年   2520篇
  1969年   2550篇
  1968年   2262篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
Weaver mutant mice are characterized by a decrease in striatal dopamine (DA), which is associated with a progressive loss of DA neurones in the substantia nigra. This mutant thus provides the opportunity to examine the functional effects of DA neurones grafted to the striatum in a genetic model of parkinsonism. Ventral mesencephalic tissue from normal foetuses was placed on the surface of the right dorsal striatum of adult weaver mutants. After grafting, animals were tested for methamphetamine-induced circling behaviour. Mutants with DA containing grafts displayed a significant circling bias toward the left, non-grafted side. Mutants without grafts did not display any rotational bias to either side. These results demonstrate that grafted DA containing neurones establish a functional innervation of the weaver striatum and suggest that grafting of neural tissue is a viable approach in restoring function in genetic degenerative disorders of the nigrostriatal system.  相似文献   
73.
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   
74.
75.
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   
76.
77.
78.
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   
79.
80.
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   
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