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   280203篇
  免费   22217篇
  国内免费   9866篇
耳鼻咽喉   2075篇
儿科学   4618篇
妇产科学   3255篇
基础医学   43063篇
口腔科学   4678篇
临床医学   20672篇
内科学   48094篇
皮肤病学   4285篇
神经病学   21127篇
特种医学   5435篇
外国民族医学   65篇
外科学   19611篇
综合类   36337篇
现状与发展   29篇
一般理论   6篇
预防医学   15840篇
眼科学   3240篇
药学   44371篇
  54篇
中国医学   12431篇
肿瘤学   23000篇
  2024年   728篇
  2023年   4933篇
  2022年   10658篇
  2021年   12914篇
  2020年   10002篇
  2019年   9567篇
  2018年   9272篇
  2017年   8924篇
  2016年   8849篇
  2015年   10214篇
  2014年   15891篇
  2013年   18074篇
  2012年   15693篇
  2011年   18402篇
  2010年   15230篇
  2009年   14958篇
  2008年   14477篇
  2007年   13236篇
  2006年   11819篇
  2005年   10436篇
  2004年   8903篇
  2003年   7919篇
  2002年   6413篇
  2001年   5297篇
  2000年   4500篇
  1999年   4090篇
  1998年   3655篇
  1997年   3406篇
  1996年   3027篇
  1995年   2724篇
  1994年   2457篇
  1993年   2110篇
  1992年   1776篇
  1991年   1679篇
  1990年   1400篇
  1989年   1169篇
  1988年   1146篇
  1987年   934篇
  1986年   878篇
  1985年   1884篇
  1984年   2072篇
  1983年   1586篇
  1982年   1740篇
  1981年   1520篇
  1980年   1214篇
  1979年   1084篇
  1978年   763篇
  1977年   596篇
  1976年   658篇
  1975年   499篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
We report a 24-year-old male with an unusual combination of two inherited neuromuscular disorders – Charcot-Marie-Tooth (CMT) disease type 1A and Duchenne muscular dystrophy (DMD). A phenotypic presentation of this patient included features of both these disorders. Nerve conduction studies revealed demyelinating peripheral neuropathy. Electromyography showed a profound myogenic pattern. The serum creatine kinase level was highly elevated. Muscle biopsy revealed a dystrophic picture with deficient dystrophin immunostaining. CMT1A duplication on chromosome 17p11.2 was found. The frame-shift mutation c.3609–3612delTAAAinsCTT (p.K1204LfsX11) was detected in the dystrophin gene by analysing mRNA isolated from the muscle tissue. The patient inherited both these mutations from his mother. The combination of CMT1A and DMD has not been reported as yet.  相似文献   
72.
Administration of cholinotoxin etylcholine aziridinium (AF64A) into the brain selectively induces nonrever-sible cholinergic deficit. Wistar rats were injected intracerebroventricularly bilaterally with AF64A at doses of 1–3 nmol/ventricle. 28 days later the number of neurons survived was counted in dorsolateral, intermediate and medial groups of cells of the medial septum. AF64A induced a decrease in neuronal density and expression of cholineacetyl transferase at all doses used as well as in all regions studied. Brain sections were also stained for NADPH-diaphorase representing neuronal NO-synthase. Effects of AF64A on NADPH-diaphorase expression depended on the region studied. The number of NADPH-diaphorase-positive cells increased in the medial cellular group where more cholineacetly transferase-positive cells survived. In contrast, decrease in NADPH-diaphorase expression in the dorsolateral group of cells coincided with low level of cholineacetyltransferase-po-sitive neurons. The data presented suggest that in the AF64A-dependent model of neurodegeneration NO may play a neuroprotective function.  相似文献   
73.
目的 探讨护理干预在2型糖尿病患康复中的作用。方法 对80例2型糖尿病患,随机分成干预组和对照组,干预组实施全程护理干预,对照组实施常规的治疗护理。结果 干预组血糖控制良好,并发症发生率明显降低。结论 护理干预是2型糖尿病康复治疗的有效方法。  相似文献   
74.
目的探讨血肿局部炎症、假膜新血管生成、局部纤溶状况及其在CSDH发生、发展中的作用。进而探讨CSDH的发病机制,并为CSDH的治疗及预防复发提供理论依据。方法以78例CSDH患者作为病例组,20例健康人作为正常对照组。采用ELISA法测定患者血清及血肿液中VEGF及IL-6的含量。比较患者末梢静脉血及血肿液中四种因子的含量变化并与正常对照组比较。结果病例组血肿液FDP、d-dimer检测均为阳性,血液为阴性;正常对照组血液FDP、d-dimer检测均为阴性;病例组血清VEGF含量与正常对照组比较差异无统计学意义。血肿液中VEGF浓度高于血清中。病例组血清IL-6浓度与正常对照组差异无统计学意义,血肿液中IL-6浓度高于血清中。CSDH患者血肿液VEGF、IL-6水平没有相关性。结论CSDH患者血肿液局部纤溶亢进,局部VEGF分泌旺盛,新血管生成活跃,局部炎症活跃,可导致CSDH不断扩大而参与CSDH发病机制。抗炎治疗、抑制VEGF的生理作用、有选择的对病人施行促凝治疗,可成为部分CSDH病人保守治疗及预防复发的有效手段。  相似文献   
75.
The objective of this study was to assess the in vivo fate of poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA)-based polyplexes after intravenous administration into mice. Circulation kinetics and tissue distribution in terms of plasmid localization and transfection efficiency were assessed. To gain more insight into the observed biodistribution and gene expression profile, the interaction of pDMAEMA-based polyplexes with blood components (erythrocytes and albumin) was investigated in vitro. In the case of i.v. injection of positively charged polyplexes at a dose of 30 microg DNA most of the radioactivity was found in the lungs and the liver 60 min after injection. In the case of pDMAEMA/DNA polyplexes with a negative charge, uptake occurred mainly by the liver. Administration of positively charged complexes at a 30 microg DNA dose resulted in reporter gene expression primarily in the lungs. Injection of negatively charged complexes and naked plasmid did not result in luciferase expression in any of the organs examined. In vitro turbidity experiments showed the induction of a charge dependent aggregation process upon addition of albumin to the polyplexes pointing out to the involvement of aggregate formation in the dominant lung uptake of the positively charged polyplexes. Also, incubations of polyplexes after pre-incubation with a physiological concentration of albumin with washed erythrocytes confirmed that polyplexes induce the formation of extremely large structures. This paper underlines the need for the design of systems with reduced interaction with blood components to promote the delivery of DNA to target tissues outside the lungs.  相似文献   
76.
Exposure of captodative enone systems to deuterium in the presence of Crabtree's catalyst ( 1 ) results in deuteration at the vinylic site β‐ to the ketone carbonyl, as well as at any accessible ortho‐position. β‐exchange is also observed during the reduction of ethyl cinnamate ( 3 ) catalyzed by 1 . Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
77.
川芎嗪对肾缺血再灌注时c-fos bcl-2 ICAM-1蛋白表达的影响   总被引:1,自引:0,他引:1  
目的 探讨大鼠肾缺血再灌注损伤不同时间c -fos、细胞淋巴瘤 /白血病 - 2、细胞间粘附分子- 1蛋白的表达及川芎嗪对其影响。方法 用免疫组化法检测大鼠急性肾缺血再灌注不同时间内及川芎嗪干预后c -fos、细胞淋巴瘤 /白血病 - 2、细胞间粘附分子 - 1蛋白表达的分布及强度变化。结果 c -fos蛋白分布于近曲小管、远曲小管、集合管上皮细胞的细胞核、细胞浆内 ,再灌注后 1h表达明显增强 ,3h达高峰 ,6h锐减。细胞淋巴瘤 /白血病 - 2蛋白主要分布于近曲小管上皮细胞的细胞浆 ,再灌注后 1h表达明显增强 ,6h达高峰 ,2 4h仍有较强表达。细胞间粘附分子 - 1蛋白分布在肾血管、肾小管等部位 ,其中以肾血管为著 ,其表达增强于再灌注后 1h ,直到 2 4h仍有增高趋势。川芎嗪干预后c -fos、细胞间粘附分子 - 1蛋白表达明显下降 (P <0 0 1 )。细胞淋巴瘤 /白血病 - 2表达明显增高 (P <0 .0 1 )。结论 川芎嗪对肾缺血再灌注损伤有较好的保护作用  相似文献   
78.
目的 研究腹腔内注射三氧化二砷(arsenic trioxide,As2O3)对小鼠CO2气腹下肝癌H22转移的影响. 方法 昆明鼠40只(清洁级),中腹部穿刺置入1 mm套管针,自套管针注入1×106肿瘤细胞后,建立CO2气腹,压力8 mm Hg,时间30 min.术后随机分4组,每组10只,分别腹腔内注入生理盐水,1 ml;As2O3(2 mg/kg),1 ml;As2O3(4 mg/kg),1 ml;As2O3(4mg/kg)+肝素(10 U/ml),共1 ml.气腹后第3、7天测量肿瘤黏附因子(CD44)、血管内皮生长因子(vascular endothelial growth factor,VEGF)的变化;比较各组生存状态、腹围、体重变化及转移瘤直径.结果 气腹后第3、7天,与对照组相比,各As2O3组CD44、VEGF表达均明显降低(P<0.05).2个高剂量组的气腹后第3天VEGF、第7天CD44比低剂量组降低明显(P<0.05).4组戳口种植率分别为9/10、8/10、7/10、6/10,差异无显著性(x2=2.667,P=0.446). 结论 As2O3对CO2气腹腹腔镜肿瘤生长转移有抑制作用.  相似文献   
79.
比较对新诊断2型糖尿病患者应用瑞格列奈(11例)和迪沙片(10例)治疗4周后空腹血糖(FPG)、餐后2h血糖(2hPG)、晨3点血糖(3aPG),空腹胰岛素(FIns)、餐后2h胰岛素(2hIns),糖化白蛋白的值。结果显示,与迪沙片组相比,瑞格列奈组治疗后空腹血糖、餐后2h血糖的下降幅度更为明显,但低血糖的发生次数反而减少。  相似文献   
80.
Mutations in PAX6/Pax6 lead to a variety of ocular anomalies in humans and mice. The aim of the study was to characterise the ocular abnormalities caused by the missense Pax6Leca4 mutation and compare them to published observations on Pax6 alleles that are functionally equivalent to Pax6 null alleles (such as Pax6Sey and Pax6Sey-Neu) and human inherited eye diseases. Ocular features of homozygous Pax6Leca4/Leca4 and heterozygous Pax6Leca4/+ embryos at E12.5-E18.5, heterozygous Pax6Leca4/+ young mice at P18 and heterozygous Pax6Leca4/+ adults at 12 weeks were analysed histologically with their wild-type Pax6+/+ littermates. Homozygous Pax6Leca4/Leca4 fetuses died perinatally with no eyes although an optic cup rudiment with pigmented cells developed. Pax6Leca4/+ mice were microphthalmic and a range of other severe ocular phenotypes affected both the anterior and the posterior segments. In contrast to Pax6+/−, the Pax6Leca4/+ eyes had no goblet cells in the corneal epithelium, the iris was not hypoplastic and there was no lens-corneal epithelial plug. However, microphthalmia was more severe, corneal vascularisation occurred earlier (during fetal stages), pigmented cells were present in the vitreous and corneal stroma and the ciliary body was malformed or abnormal. These results show that, although Pax6Leca4/+ lacked some eye abnormalities commonly seen in Pax6Sey/+ and Pax6Sey-Neu/+ eyes, in most respects their eyes were more severely affected. These differences probably reflect both differences between the Pax6Leca4 and the Pax6Sey-Neu mutations and differences in modifier gene expression in different genetic backgrounds. The presence of pigmented cells in the cornea is a novel observation. Some Pax6Leca4/+ ocular abnormalities were similar to those present in human Peters' anomaly and persistent hyperplastic primary vitreous (PHPV) so Pax6Leca4/+ mice provide a useful model for some inherited eye diseases.  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