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   38684篇
  免费   3728篇
  国内免费   2644篇
耳鼻咽喉   399篇
儿科学   476篇
妇产科学   388篇
基础医学   4057篇
口腔科学   682篇
临床医学   5049篇
内科学   5184篇
皮肤病学   430篇
神经病学   1756篇
特种医学   1433篇
外国民族医学   16篇
外科学   3721篇
综合类   7343篇
现状与发展   13篇
一般理论   6篇
预防医学   3290篇
眼科学   917篇
药学   4236篇
  33篇
中国医学   2800篇
肿瘤学   2827篇
  2024年   145篇
  2023年   585篇
  2022年   1511篇
  2021年   1883篇
  2020年   1501篇
  2019年   1225篇
  2018年   1253篇
  2017年   1369篇
  2016年   1194篇
  2015年   1722篇
  2014年   2222篇
  2013年   2192篇
  2012年   3125篇
  2011年   3390篇
  2010年   2356篇
  2009年   1967篇
  2008年   2332篇
  2007年   2221篇
  2006年   2062篇
  2005年   1862篇
  2004年   1365篇
  2003年   1278篇
  2002年   1029篇
  2001年   846篇
  2000年   741篇
  1999年   656篇
  1998年   407篇
  1997年   370篇
  1996年   276篇
  1995年   295篇
  1994年   251篇
  1993年   177篇
  1992年   203篇
  1991年   191篇
  1990年   136篇
  1989年   140篇
  1988年   133篇
  1987年   104篇
  1986年   80篇
  1985年   62篇
  1984年   29篇
  1983年   43篇
  1982年   8篇
  1981年   17篇
  1980年   13篇
  1979年   15篇
  1977年   8篇
  1976年   7篇
  1974年   7篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
74.
We have constructed cDNA microarrays from the human testis large insert cDNA library, containing 9216 genes, together with several housekeeping genes. The cDNA microarrays were used to identify gene expression differences between human fetal and adult testes. Of >8700 hybridized clones, 731 exhibited significant differential expression characteristics. About 7500 genes were identified when the same cDNA microarrays were used for hybridization with cDNA probes from mouse testis, with 256 genes having significant differential expression between the age of 1-4 weeks. Among these genes, 101 were identified as critically related to testis development and possibly to spermatogenesis since they were found in both human and mouse testes, and expressed differentially at different stages of testis development. Of the 101 development-related genes, 59 full-length cDNAs have been sequenced previously, while the full-length cDNAs of the other 42 genes have not been published. We have obtained 11 full-length sequences of the 42 genes and deposited them in the GenBank. The conserved testis development-related genes found in both human and mouse testes may include genes that are likely to be involved in testicular functions, especially spermatogenesis, thus providing a basis for further functional characterization of the genes in mouse models.  相似文献   
75.
Biomaterial-related infections continue to represent a significant challenge to the medical community. Several approaches have been utilized to incorporate antimicrobial agents at the surface of implant devices in attempts to delay or eliminate the formation of biofilms. To date, most of these strategies have focused on drug conjugation or diffusion-limited systems for the delivery of such pharmaceutical agents. More recently, work has been presented on the feasibility of incorporating drugs into the backbone of polymers as a main-chain monomer. When sequenced into the backbone of the polymer with other monomers that are hydrolytically sensitive to enzyme-catalyzed breakdown, it is thought that drugs may be able to be selectively released. Specifically, degradable polyurethanes have been synthesized with fluoroquinolone antibiotics and have shown an ability to kill bacteria when released following degradation of the polymer chains by the macrophage-derived enzyme cholesterol esterase. However, specificity of the cleavage sites in the polymer was difficult to control. Since cholesterol esterase has specificity for hydrophobic moieties, it is desirable to alter the formulation of the polyurethanes to incorporate long hydrophobic monomers immediately adjacent to the ciprofloxacin molecule. Hence, the current study focuses on evaluating the enzyme-catalyzed degradation of a degradable polyurethane synthesized with 1,12 diisocyanatododecane as a substitute for 1,6 diisocyanatohexane, which was used in previous work. Validation of specific ciprofloxacin release and the generation of antimicrobial are shown. A preliminary cell study to assess the cytotoxicity of this biodegradable antibiotic polymer shows that the material has no observable effects on cell proliferation or cell membrane structure.  相似文献   
76.
Left ventricular contractility can be assessed from the end-systolic pressure-volume relationship (ESPVR). In this study we test the hypothesis that the same ESPVR can be obtained by varying LV loading with different levels of negative intrathoracic pressure as by varying LV filling. In six dogs mean aortic transmural pressure was used to approximate LV end-systolic pressure and LV volume was determined from data gathered from biplane cineradiograms of multiple markers placed in the LV midwall. In each preparation right heart bypass allowed control of cardiac output while the thoracic pressure was varied with a box surrounding a midsternal thoracotomy. Reflex effects were minimized by ganglionic blockade and bilateral vagotomy. ESPVRs were obtained by varying the cardiac output at constant thoracic pressure or by changing intrathoracic pressure at constant cardiac output. The slopes of the ESPVRs were not significantly different. This result implies that LV loading by negative intrathoracic pressure, in this highly controlled preparation, can be used to generate a systolic LV elastance similar to that obtained by varying LV filling.  相似文献   
77.
彩色多普勒超声对肠套叠的诊断价值与治疗体会   总被引:1,自引:0,他引:1  
肠套叠是外科常见急腹症之一,临床以小儿为多见,若不能及时诊治,可并发肠坏死和中毒性休克,甚至危及生命。我科自1998年至2007年12月,采用彩色多普勒超声对124例(共132人次)进行诊治,收到满意疗效,现将其诊断价值和治疗体会报告如下。  相似文献   
78.
目的研究CD54和LFA-1的相互作用在6A8 α-甘露糖苷酶表达抑制的Jurkat细胞(AS)的黏附性增强中的作用。方法用细胞凝集试验确证AS细胞间黏附的增强,用细胞与细胞间黏附分子-1-人IgG的Fc片段(ICAM-1-Fc)的黏附试验和阻断性抗CD11a抗体的阻断试验研究CD54-LFA-1的作用,用单克隆抗体MEM-148检测As细胞LFA-1亲和力的变化,用单克隆抗体NKI-L16检测AS细胞LFA-1亲合力的变化,用鬼笔环肽染色细胞骨架,用Jurkat-Raji细胞间的作用作模型研究6A8α-甘露糖苷酶表达抑制对T和B细胞间黏附的影响,用ConA结合试验检测细胞中蛋白质N-糖基化的变化。结果(1)AS细胞间的黏附性增强主要与CD54及CD11a表达的增强相关,也与LFA-1亲和力的增高相关;(2)AS细胞的细胞骨架发生重排;(3)As细胞与Raji细胞间的黏附也增强;(4)ConA与AS细胞的结合增强。结论CD54和LFA-1的相互作用在AS Jurkat T细胞的黏附性增强中起重要作用。细胞骨架重排也可能起作用。As细胞的蛋白质发生了N-糖基化修饰。  相似文献   
79.
The concept and taxonomy of periodic psychosis still remains in controversy for the past 100 years. In China, it was first reported by Ji, and thereafter various rinds of terminology and views were given by different authors. In the presentation, clinical investigation and follow up were carried out in 62 cases. In many of these cases, the so-called "periodic psychosis" or "phasophrenia" was early clinical features of schizophrenia or manic-depression. In those cases with apparent symptoms and signs of diencephalic function, differential diagnosis should be carried out from organic brain syndrome. In a small number of cases, their clinical manifestations, conforming to previous diagnostic criteria, might be an uncommon syndrome. It was concluded by the authors that until now periodic could be considered only as a clinical syndrome rather than a disease entity.  相似文献   
80.
通过查阅古代相关本草、医籍、经史及近现代文献资料,笔者对藿香类药材的名称、基原、产地、品质评价、栽培、采收加工及炮制方法等进行了系统梳理与考证,可为含藿香类药材的经典名方开发利用提供依据。通过本草考证分析可知,历代本草多以“藿香”为正名,所用主流基原均为Pogostemon cablin,为区别于明代以来我国民间习用的同科另一种植物土藿香Agastache rugosa及推崇道地产区而有“广藿香”之名;广藿香原产于越南等东南亚国家,早期因作香料经广东等地传入我国,宋代以来便已在我国南方引种成功;药用部位多为其干燥地上部分,亦有将其叶、梗分开单独使用;历代推崇的道地产区为广东,现广东广州、肇庆、湛江和海南省多有栽培,以石牌所产最为知名;广藿香主要为扦插繁殖,二月生苗,六月采收;产地加工方法主要为闷晒法,放置阳光下反复闷晒至有芳香气味、颜色转黄;炮制方法多以净选后生品入药。基于考证结果,建议养胃汤中所用藿香以P. cablin为基原,取叶片生品入药,而藿朴夏苓汤则建议选择土藿香A. rugosa除去根及老茎的生品入药。  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