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   388968篇
  免费   32216篇
  国内免费   14440篇
耳鼻咽喉   3876篇
儿科学   8802篇
妇产科学   5095篇
基础医学   57951篇
口腔科学   9661篇
临床医学   29142篇
内科学   52543篇
皮肤病学   7042篇
神经病学   23587篇
特种医学   11286篇
外国民族医学   126篇
外科学   48349篇
综合类   55528篇
现状与发展   73篇
一般理论   12篇
预防医学   19568篇
眼科学   6852篇
药学   38898篇
  90篇
中国医学   17672篇
肿瘤学   39471篇
  2024年   595篇
  2023年   4986篇
  2022年   8396篇
  2021年   14502篇
  2020年   12703篇
  2019年   12528篇
  2018年   12837篇
  2017年   13743篇
  2016年   14055篇
  2015年   14592篇
  2014年   19831篇
  2013年   25189篇
  2012年   20700篇
  2011年   24237篇
  2010年   18321篇
  2009年   18064篇
  2008年   19987篇
  2007年   21186篇
  2006年   19960篇
  2005年   18195篇
  2004年   15618篇
  2003年   13654篇
  2002年   10956篇
  2001年   9563篇
  2000年   7984篇
  1999年   6878篇
  1998年   6013篇
  1997年   5768篇
  1996年   5236篇
  1995年   4567篇
  1994年   4297篇
  1993年   3454篇
  1992年   3155篇
  1991年   2850篇
  1990年   2324篇
  1989年   2029篇
  1988年   1947篇
  1987年   1629篇
  1986年   1496篇
  1985年   2049篇
  1984年   1714篇
  1983年   1245篇
  1982年   1320篇
  1981年   1079篇
  1980年   994篇
  1979年   764篇
  1978年   517篇
  1977年   426篇
  1976年   375篇
  1975年   235篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Angiogenesis,the formation of new bloodvessels,is necessary for the growth of tumors andtheir metastasis.TNP- 470 is a synthetic analogueof fumagillin and has stronger antiangiogenic  ac-tivity and less side- effects than fumagillin.Thiscompound has been reported to suppress the prolif-eration and metastasis of various kinds of tu-mors[1] . Using nude mice xenografts of ACHN hu-man renal cell carcinoma ( RCC) ,the presentstudyattempted to examine the action of TNP- 470 ongrowth,metastasi…  相似文献   
972.
Purpose Reelin is important in the guidance of neuronal stem cells in the central nervous system during normal development. We wished to determine whether reelin is expressed in the retina and cornea after injury. Methods Mice underwent laceration of their retina as well as corneal epithelial debridement. The mice were sacrificed at 3 days, and eyes were fixed and stained for reelin expression and reelin messenger ribonucleic acid (mRNA). Results In normal eyes, reelin was expressed only at very low levels in the ganglion cell layer of the retina and the endothelial cell layer of the cornea. In injured eyes, there was marked expression in reelin immunoreactivity in the retina and cornea. Reelin gene expression was seen in the retina and cornea. Conclusions Reelin is expressed during normal retinogenesis. This study shows that reelin is also upregulated following injury to the retina and cornea. The expression of reelin following injury suggests that reelin may play an important role in regulating stem cell trafficking in neuronal and nonneuronal tissues following injury similar to its role in normal organogenesis. For consideration of publication in Graefe’s Archive for Clinical and Experimental Ophthalmology.  相似文献   
973.
目的探讨闭合性脑外伤患者恢复后期的记忆障碍特点。方法用临床记忆量表对 2 0例闭合性脑外伤患者恢复后期及 2 0例正常人进行记忆测验。结果闭合性脑外伤患者恢复后期 5项分测验及记忆商均明显低于正常人对照组 ,MQ≤ 79的比例较正常人明显增高。结论闭合性脑外伤患者恢复后期有非常严重的记忆障碍 ,其回忆比再认受损更严重  相似文献   
974.
螺旋藻多糖对人宫颈癌Hela细胞体外生长的影响   总被引:6,自引:1,他引:5  
目的:探讨螺旋藻多糖(PSP)对体外培养的Hela细胞生长的影响。方法:采用MTT法测定 PSP的抗肿瘤活性,并观察其对Hela细胞形态学的影响。结果:随PSP浓度的升高,Hela细胞存活率逐渐降低,抑制率逐渐增加;光镜下观察显示,PSP作用24-48h后,细胞出现明显的形态学改变。结论:PSP能抑制Hela细胞增殖。  相似文献   
975.
Background A recombinant form of the α2(IV)NC1 domain of type IV collagen has been shown to have potent anti-angiogenic activity although this peptide has not been studied in the context of proliferative retinopathies. In the current investigation we examined the potential for α2(IV)NC1 to regulate retinal microvascular endothelial cell function using a range of in vitro and in vivo assay systems. Materials and methods α2(IV)NC1 at concentrations between 0.1 and 1 μg/ml was added to retinal microvascular endothelial cells (RMECs) followed by assessment of cell attachment, proliferation and survival. This agent was also tested within a novel in vitro three-dimensional retinal angiogenesis assay and the number of angiogenic sprouts quantified. α2(IV)NC1 was also delivered intra-vitreally to mice with oxygen-induced proliferative retinopathy (OIR) and neovascularisation evaluated in comparison with vehicle-treated controls. Results RMECs treated with α2(IV)NC1 (0.1, 0.5 and 1 μg/ml) showed delayed attachment at 3 h post-seeding, although this deficit had been restored at the 6-h time point. BrdU assay of DNA replication revealed that confluent RMECs treated with α2(IV)NC1 showed no measurable response in comparison with vehicle-treated controls. By contrast, proliferation of sub-confluent RMECs was significantly reduced by α2(IV)NC1 at 0.5 μg/ml (P<0.01). α2(IV)NC1 also induced apoptosis in RMECs and inhibited angiogenesis of pre-existing retinal vascular networks in vitro (P<0.001). Intra-vitreal injection of α2(IV)NC1 in the OIR model significantly inhibited pre-retinal neovascularisation compared with vehicle-treated controls (P<0.001). Conclusion α2(IV)NC1 inhibits angiogenesis in the retinal microvasculature. This recombinant protein has potential for the treatment of neovascularisation in proliferative retinopathies. BioStratum Inc. did not sponsor this research in any way. None of the authors are paid consultants with this company.  相似文献   
976.
We have reviewed some of the factors which contribute to lung damage by various toxicants. These include disposition of the chemical, its metabolism, individual cell type susceptibility and the potential for the tissue to repair. We have discussed the use of biochemical parameters to measure the functional activity of individual cell types in order to predict the damage to specific cell types and concluded that careful morphological analysis of lung tissue is likely to provide a more sensitive and informative measure of specific cell type injury. However, in order to investigate the mechanism of toxicity of pulmonary toxicants it is essential to establish the primary biochemical event that leads to cell damage and morphological change. The importance of separating the relevant biochemical change(s) from the cascade of biochemical events associated with dead and dying cells and the reparative response of the lung is emphasised.This report results from a discussion sponsored and organised by the Advisory Subgroup in Toxicology (AST) of the European Science Foundation's Standing Committee for the European Medical Research Councils and held at the Medical Research Council Toxicology Unit, Carshalton, U. K. Those taking part were: W. N. Aldridge (AST; as above); J. Bignon (Unit for Research in Renal and Pulmonary Pathology, University of Paris, Creteil, France); P. H. Burri (Section of Developmental Biology, Institute of Anatomy, University of Berne, Switzerland); G. M. Cohen (as above); D. Dinsdale (MRC Toxicology Unit, Carshalton U. K.); P. Hedqvist (Dept. of Physiology, Karolinska Institute, Stockholm, Sweden); D. Henschler (AST; Dept. of Toxicology and Pharmacology, University of Wurzburg, FDR); G. J. Laurent (Biochemistry Unit, Cardiothoracic Institute, University of London, London, U. K.); R. Lauwerys (AST Industrial and Medical Toxicology Unit, University of Louvain, Brussels, Belgium); F. Lembeck (AST; Dept. for Experimental and Clinical Pharmacology, University of Graz, Austria); N. Lery (AST; Poison Control Centre, Lyon, France); P. Moldeus (Dept. of Forensic Medicine, Karolinska Institute, Stockholm, Sweden); B. Nemery (MRC Toxicology Unit, Carshalton, U. K.); A. Saria (Dept. for Experimental and Clinical Pharmacology, University of Graz, Austria); L. L. Smith (as above);B. Terracini (AST; Dept. of Pathology and Cancer Epidemiology, University of Turin, Italy)  相似文献   
977.
978.
目的探讨环境致癌物苯并(a)芘代谢物反式二羟环氧苯并芘(BPDE)对人支气管上皮细胞HER2/neu基因表达的影响。方法利用半定量RT-PCR、SYBR GreenI实时定量RT-PCR(QRT-PCR)、Western blot及免疫细胞化学方法分别检测经2.0μmol/L反式BPDE诱发人支气管上皮细胞恶性转化细胞(16HBE-T)与对照DMSO溶剂组未恶性转化细胞(16HBE-N)之间HER2/neu基因mRNA和蛋白表达水平的差异,及两组细胞内HER2/neu蛋白表达定位分析。结果经几种不同方法检测反式BPDE恶性转化人支气管上皮细胞中HER2/neu基因mRNA和蛋白水平都比对照溶剂组细胞(16HBE-N)表达显著升高(P<0.05)。HER2/neu蛋白定位在胞膜。结论反式BPDE诱发人支气管上皮细胞恶性转化存在HER2/neu表达增高,其可能与原癌基因HER2/neu被激活作用有关。  相似文献   
979.
庆大霉素中毒性耳聋   总被引:1,自引:0,他引:1  
庆大霉素目前仍是主要的致聋抗生素,庆大霉素中毒性耳聋的发病机制包括自由基损伤学说、内耳微循环障碍学说、毛细胞线粒体功能失常学说、细胞凋亡等,并发现一些与耳聋相关的基因。聚DL-天冬氨酸(PAA)、表皮生长因子(EGF)表皮生长因子(EGF)、碱性成纤维细胞生长因子(bFGF)、神经营养凼子3(NT3)、高压氧等对庆大霉素的耳毒性有一定的拈抗作用。中医药丹参、天鼓冲剂、复聪片、耳聋左慈丸等也可减轻庆大霉素的耳毒性。庆大霉素中毒性耳聋基因治疗具有良好的前景。制造一种由病毒DNA序列和非病毒载体结构共同组成的复合型载体,也许是未来基因治疗载体得到完善、基因治疗得到突破性进展的着手点之一。  相似文献   
980.
用20只Wistar大鼠以PHA—L免疫组织化学顺行追踪技术研究了下丘脑室旁核及其邻近区域对脑室系统室管膜的传出联系。在脑室系统某些部位的室管膜层或其下方见有丰富的标记纤维并见许多膨结和终末膨突。这些纤维似乎参与形成室管膜上、下丛,构成脑—脑脊液神经体液回路的重要环节。  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