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   21082篇
  免费   1369篇
  国内免费   778篇
耳鼻咽喉   399篇
儿科学   189篇
妇产科学   196篇
基础医学   1695篇
口腔科学   847篇
临床医学   3115篇
内科学   2085篇
皮肤病学   87篇
神经病学   292篇
特种医学   1071篇
外科学   3171篇
综合类   3510篇
现状与发展   5篇
预防医学   1951篇
眼科学   316篇
药学   1913篇
  23篇
中国医学   1169篇
肿瘤学   1195篇
  2024年   53篇
  2023年   185篇
  2022年   423篇
  2021年   554篇
  2020年   452篇
  2019年   264篇
  2018年   247篇
  2017年   355篇
  2016年   232篇
  2015年   507篇
  2014年   658篇
  2013年   791篇
  2012年   1432篇
  2011年   1916篇
  2010年   1460篇
  2009年   1033篇
  2008年   1551篇
  2007年   1684篇
  2006年   1574篇
  2005年   1393篇
  2004年   1284篇
  2003年   1274篇
  2002年   1176篇
  2001年   797篇
  2000年   980篇
  1999年   449篇
  1998年   138篇
  1997年   36篇
  1996年   35篇
  1995年   39篇
  1994年   29篇
  1993年   40篇
  1992年   14篇
  1991年   20篇
  1990年   10篇
  1989年   16篇
  1988年   19篇
  1987年   20篇
  1986年   14篇
  1985年   14篇
  1984年   9篇
  1983年   13篇
  1982年   9篇
  1981年   3篇
  1980年   4篇
  1978年   2篇
  1976年   6篇
  1975年   4篇
  1973年   3篇
  1972年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Different blood saving methods are analyzed in 2000 cardiac surgical patients undergoing coronary and vascular bypass surgery in 1993 to 2000. The basic blood saving methods are as follows: intraoperative autoreinfusion (normovolemic thermodilution), reinfusion of the patient's blood, preoperative autologous plasma donation in combination with aprotinine, aminocapronic acid, etc. An analysis revealed a decrease in homologous blood components intraoperatively. Red blood cell transfusion decreased from 100% in 1993 to 44% in 2000, fresh frozen plasma and platelet transfusions did from 98 to 39% and from 96 to 1%, respectively. Intraoperative homologous blood transfusion could be avoided in 70% of those undergone coronary bypass surgery.  相似文献   
22.
Indices of blood oxygen transport (hemoglobin-oxygen affinity, pCO2, pH, pO2, etc.) and prooxidant-antioxidant state (Schiff bases, conjugated dienes, catalase, retinal, alpha-tocopherol) were measured in rabbit blood and the liver during postischemic reperfusion. Hepatic ischemia was induced for 30 min by ligation of a hepatica propria, and reperfusion lasted for 120 min. Hepatic ischemia worsened blood oxygen transport. Restoration of arterial blood flow did not result in improvement of oxygen delivery. Moreover, marked metabolic acidosis was observed throughout 2 hr of reperfusion. Ischemia induced a shift of oxyhemoglobin dissociation curve to the right. This shift persisted after restoration of hepatic arterial blood flow facilitating increased oxygen transport to tissues. Changes in blood oxygen transport during hepatic ischemia/reperfusion were accompanied with high activity of free radical processes. During reperfusion, the largest increase in content of lipid peroxidation products and the greatest fall of some antioxidant levels except catalase were observed indicating impairment of liver prooxidant-antioxidant balance. The results showed that activation of lipid peroxidation and a decrease in some antioxidant levels during hepatic reperfusion were associated with lowering of hemoglobin-oxygen affinity and suggest participation of the latter in impairment of prooxidant-antioxidant balance.  相似文献   
23.
Gene P504S is considered as the most specific for prostatic carcinoma and its protein (alpha-methylacyl coenzyme A racemaze (AMACR/P504S) is higly sensitive and specific marker not only for adenocarcinoma cells but also for preceding changes - prostatic intraepithelial neoplasm (PIN). AMACR/P504S seems to be the first marker of malignant transformation and tumor progression. Use of immunohistochemical method for revealing this marker together with methods of basal prostatic cells observation (cytokeratin of a high molecular weight, cytokeratin 5/6, p63) improves morphological diagnosis of prostatic carcinoma, particularly on the material of needle biopsies. This combination allows one to identify neoplastic nature of some difficult lesions.  相似文献   
24.
Histological, histochemical and immunohistochemical studies of 50 solitary juvenile polyps (JP) and 50 JP from children with juvenile polyposis syndrome (JPS) were performed. Observations of the focal complex glandular structures with high mitotic rate were more frequent in JP from patients with JPS (n = 29, 58%) than in solitary JP (n = 17, 34%) (p < 0.03). The immunohistochemical study demonstrated p53 overexpression in individual cells and more than 50% of Ki-67-positive cells in 5 (10%) solitary JP and in 17(34%) JP from patients with JPS (p < 0.007). The finding of microglandular pattern is more typical for JP from patients with JPS. Pathological data, expression of p53 and Ki-67 by immunohistochemistry could help to pick out the group of JP with dysplastic changes.  相似文献   
25.
26.
交互信息是一种检测系统之间相依性的方法 ,它可以同时检测线性和非线性相关。本文介绍了交互信息的计算方法和性质 ,讨论了它在单个时间序列上的应用 ,并将它应用于心脏状态研究上。利用实验动物的数据 ,我们发现了心搏的运动既不是随机的也不是周期的 ;并且 ,不同心脏状态下的交互信息有很大的差别 ,浅麻 ,机控呼吸和开胸状态下交互信息都相对较小 ,心肌损伤后有明显增大 ,提示心搏的交互信息与心脏健康程度有很大关系  相似文献   
27.
28.
The lamellar bone mineral component in mature and senile age was studied using the methods of transmission electron microscopy and cryofractography. This component was shown to be formed by crystals (13-4 x 7-8 x 3-4 nm) of the prismatic shape that formed coplanar units (29-3 x 18-21 x 3-4 nm). The peculiarities of mineral particle distribution inside and between the collagen fibrils, as well as on the completely formed areas of bone surface, were detected. It was established that the length and the width of coplanar crystal aggregates was significantly higher in senile age as compared to similar linear parameters defined in persons of mature age (by 17-20 and 5-9%, respectively).  相似文献   
29.
目的通过对57例妊娠分别使用二维、三维超声测量相关参数估计胎重,并作统计学比较,从而评价三维超声对于估测胎儿体重、诊断胎儿发育迟缓及巨大胎的优势和价值。方法对2005年10月至2006年3月间在我院分娩的57例妊娠,研究组用三维超声测胎儿股容积估计胎重,对照组用二维超声同步测量相关参数估计胎重。结果对两组估重结果与胎儿实际出生体重作相关统计学分析,研究组相关系数为0.983,对照组为0.906(P〈0.05),前者与实际体重关系更密切。结论三维超声测量胎儿股容积估测胎儿体重,较传统二维超声具有更大优势,对于发现胎儿发育迟缓(FGR)及巨大胎意义重大,有利于指导临床冶疗、选择分娩方式。  相似文献   
30.
The aim of this work was to demonstrate the role of interferon alpha (IA) in apoptosis control of cells of hypothalamohypophysial adrenocortical system (HHAS) in young and old mice under conditions of hyperoxia. The increase of functional activity of neurosecretory cells of hypothalamic paraventricular nucleus in old mice treated with IA was demonstrated, while no effect was found in young mice. This differences could be associated with aging changes in HHAS in intact old animals. Oxidative stress caused an increase in the number of cells synthesizing proapoptotic c-fos protein in paraventricular nucleus of mice of both age groups. However, the protective action of IA against the stress is expressed more actively and in more early stage of apoptosis in young mice. Thus, the degree of IA participation in the control of programmed cell death of hypothalamic cells depends on the age of the animal. In the adrenal zona fasciculata of young mice the number of apoptotic cells was significantly increased after IA administration while after hyperoxia or its combination with IA it remained at control level. In the adrenal gland of old mice the proportion of apoptotic cells was not different from that found in young mice and remained unchanged after all experimental challenges.  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