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   669762篇
  免费   60101篇
  国内免费   42999篇
耳鼻咽喉   5399篇
儿科学   8861篇
妇产科学   9502篇
基础医学   71742篇
口腔科学   11668篇
临床医学   91284篇
内科学   92664篇
皮肤病学   7592篇
神经病学   31896篇
特种医学   24029篇
外国民族医学   306篇
外科学   62372篇
综合类   121079篇
现状与发展   141篇
一般理论   77篇
预防医学   50536篇
眼科学   18456篇
药学   72033篇
  722篇
中国医学   42177篇
肿瘤学   50326篇
  2024年   2180篇
  2023年   9129篇
  2022年   23780篇
  2021年   30629篇
  2020年   23840篇
  2019年   19577篇
  2018年   20626篇
  2017年   19996篇
  2016年   18242篇
  2015年   28527篇
  2014年   35836篇
  2013年   34307篇
  2012年   50769篇
  2011年   56163篇
  2010年   38633篇
  2009年   31697篇
  2008年   38965篇
  2007年   38676篇
  2006年   36605篇
  2005年   34873篇
  2004年   23558篇
  2003年   22030篇
  2002年   18443篇
  2001年   16101篇
  2000年   15486篇
  1999年   15230篇
  1998年   9160篇
  1997年   8979篇
  1996年   6930篇
  1995年   6386篇
  1994年   5558篇
  1993年   3597篇
  1992年   4751篇
  1991年   4177篇
  1990年   3478篇
  1989年   3034篇
  1988年   2594篇
  1987年   2370篇
  1986年   1904篇
  1985年   1447篇
  1984年   868篇
  1983年   663篇
  1982年   368篇
  1981年   368篇
  1980年   305篇
  1979年   396篇
  1978年   215篇
  1977年   165篇
  1974年   161篇
  1973年   137篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
PURPOSE: Perineural invasion is a frequent occurrence in salivary adenoid cystic carcinoma (ACC) and may prevent complete surgical resection. Studies have indicated that nerve growth factor (NGF) and its high-affinity receptor tyrosine kinase A (TrkA) may play a role in perineural invasion in several malignancies in which perineural invasion is observed. The present study was conducted to investigate the expression of NGF and TrkA in salivary ACC and to examine the effects of NGF on adhesion, migration and invasion capacities of a salivary ACC cell line (SACC-83) in vitro. PATIENTS AND METHODS: Expression of NGF and TrkA was explored using immunohistochemistry in paraffin-embedded tissues of 32 cases of salivary ACC. The effects of NGF on in vitro adhesion, migration, and invasion capacities of the SACC-83 cell line were examined using an MTT assay and a modified Boyden chamber assay respectively. RESULTS: In ACC specimens, 31 (96.9%) and 32 (100%) tumors showed immunoreactivity for NGF and TrkA respectively. Significant correlations were found between NGF/TrkA expression levels and perineural invasion (P < .05). In cell adhesion assay, the percent adherences of SACC-83 cells co-cultured with 25 ng/ml NGF at 1.5 hours and 5, 25 ng/ml NGF at 6 hours were significantly higher than that co-cultured with 0 ng/ml NGF (P < .05). However, high concentration of NGF (500 ng/ml) resulted in a significant inhibition of invasion (P < .05). CONCLUSION: Overexpression of NGF and TrkA in human salivary ACC tissues may constitute a reason for perineural invasion in salivary ACC.  相似文献   
72.
73.
We analyzed performance and efficiency of the left ventricular myocardium on the basis of two new energetic parameters. The myocardial energy consumed during one cardiac cycle is related to performed work on the one hand (E1) and to the stress-time-integral on the other (E2). E1 was obtained by analysis of the pressure-volume integral divided by left ventricular muscle mass. E2 was obtained as follows: the stress-time integral was analyzed from pressure-volume data and wall thickness using an ellipsoidal calculation model. In order to transfer the stress-time integral into energy units, the value was multiplied by a constant factor which was obtained in experimental myothermal studies. In ten patients with coronary heart disease undergoing diagnostic heart catheterization, angiocardiography was performed before and after oral administration of nitroglycerin (1.6 mg). Total energy consumption (2E1 + E2) per gram myocardium per beat decreased from 6.1 +/- 1.3 mcal/g to 4.7 +/- 1.4 mcal/g (P less than 0.01), and myocardial efficiency (E1/[2E1 + E2]) increased from 27.0 +/- 3.1% to 28.4 +/- 4.3% (N.S.) on the average. This analysis explains quantitatively the beneficial effect of nitro-preparations on myocardial function and energetics.  相似文献   
74.
胸部类癌   总被引:2,自引:0,他引:2  
本文报道了31例胸部类癌,其中胸腺类癌14例,支气管类癌17例,伴有异位ACTH综合征者17例。12例患者发生转移(39%),24例行原发肿瘤全部或部分切除,术后放疗或化疗或两者均有者17例,4例仅行探查并取活检,28例经手术及病理证实。  相似文献   
75.
四氧嘧啶诱发糖尿病大鼠血管紧张素的变化   总被引:1,自引:0,他引:1  
实验观察了四氧嘧啶诱发糖尿病大鼠连续饲养110d后体内肾素一血管紧张素系统的变化。结果表明,血浆和心脏的血管紧张素Ⅱ含量无明显变化,而肾脏的AngⅡ含量却明显低于正常对照组。另外,心脏的心钠素(ANP)含量在糖尿病大鼠与正常对照组之间无差别,血中的糖化血红蛋白含量基本无变化。上述结果表明,糖尿病大鼠早期心脏可能无明显损伤,而肾脏的肾素一血管紧张素系统活性降低。  相似文献   
76.
An analysis of serum free amino acid profiles in 8 patients dying from major burns revealed that free amino acid began to decrease in shock period, decrease 31.12% in infection period and 41.3% before death in comparison with the control group. The amount of BCAA-also decrease 36.27% in infection period and 56.83% before death. If the serum free amino acid in major burn drops steadily, the prognosis will be worse.  相似文献   
77.
Type IIIC tibial fractures are complex injuries involving extensive bone and soft-tissue devascularization that result in a high percentage of complications and ultimate amputation. An emergency free flap transfer not only may salvage the limb but also may improve the aesthetic and functional results of reconstruction by placing the injured structures in a well-vascularized bed. Two cases of type IIIC tibial fracture were treated in this manner, and we present our experience with a 30-month follow-up of one patient and a 6-month follow-up of another patient.  相似文献   
78.
79.
神经肽Y(NPY)是广泛分布于中枢神经系统和外周神经各部位的神经肽类物质。本实验观察NPY在体外对几种免疫细胞活性的直接作用。结果表明,NPY对小鼠T淋巴细胞丝裂原反应性和NK细胞的杀伤活性均无明显影响(P>0.05),对巨噬细胞分泌溶菌酶有明显抑制作用(P<0.05);而对B淋巴细胞丝裂原反应性则有明显的促进作用(P<0.05)。上述结果提示,NPY对部分免疫细胞功能的影响因细胞种类而异。  相似文献   
80.
We describe a 15-y-old girl with Fechtner-like syndrome, who is the first Chinese reported to have this rare syndrome. She presented with left homonymous hemianopia and neuroimaging revealed haemorrhage in both parietal and occipital lobes. Peripheral blood smear showed macrothrombocytopenia and intracytoplasmic inclusion bodies inside leucocytes. Thrombocytopenia and proteinuria responded to intravenous immunoglobulin and pulsed methylprednisolone. This case illustrates that life-threatening haemorrhage can occur in patients with Fechtner syndrome. Although there was no effective treatment reported in the literature, high dose steroid and immunoglobulin seemed to be useful in our patient. Our patient also had nephritic-nephrotic syndrome with renal insufficiency, which is unusual in adolescent female patients.  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