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   30008篇
  免费   2869篇
  国内免费   2235篇
耳鼻咽喉   332篇
儿科学   356篇
妇产科学   354篇
基础医学   3601篇
口腔科学   545篇
临床医学   4010篇
内科学   4433篇
皮肤病学   367篇
神经病学   1571篇
特种医学   1112篇
外国民族医学   17篇
外科学   2730篇
综合类   5045篇
现状与发展   7篇
一般理论   6篇
预防医学   2203篇
眼科学   876篇
药学   3277篇
  19篇
中国医学   1778篇
肿瘤学   2473篇
  2024年   96篇
  2023年   465篇
  2022年   1211篇
  2021年   1553篇
  2020年   1203篇
  2019年   1060篇
  2018年   1097篇
  2017年   1098篇
  2016年   1001篇
  2015年   1374篇
  2014年   1787篇
  2013年   1643篇
  2012年   2357篇
  2011年   2505篇
  2010年   1553篇
  2009年   1245篇
  2008年   1640篇
  2007年   1595篇
  2006年   1481篇
  2005年   1472篇
  2004年   1027篇
  2003年   977篇
  2002年   834篇
  2001年   672篇
  2000年   595篇
  1999年   599篇
  1998年   404篇
  1997年   363篇
  1996年   270篇
  1995年   284篇
  1994年   248篇
  1993年   177篇
  1992年   201篇
  1991年   189篇
  1990年   136篇
  1989年   138篇
  1988年   131篇
  1987年   101篇
  1986年   80篇
  1985年   61篇
  1984年   28篇
  1983年   42篇
  1981年   17篇
  1980年   13篇
  1979年   15篇
  1978年   7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 15 毫秒
101.
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   
102.
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   
103.
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   
104.
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   
105.
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   
106.
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   
107.
108.
109.
目的观察高频重复经颅磁刺激(rTMS)联合认知行为治疗对脑卒中后焦虑(PSA)、脑卒中后抑郁(PSD)共病状态患者的影响。 方法采用随机数字表法将160例脑卒中后焦虑抑郁状态患者分为对照组和观察组。两组患者均给予脑卒中常规治疗、抗抑郁药物治疗和认知行为治疗,对照组同时给予高频rTMS假刺激治疗,观察组则给予高频rTMS真刺激治疗。观察4周后2组患者抑郁症状、焦虑症状、睡眠质量、日常生活能力改善情况。 结果两组患者汉密尔顿抑郁量表(HAMD)评分、汉密尔顿焦虑量表(HAMA)评分、匹兹堡睡眠指数量表(PSQI)、改良Barthel指数(MBI)在治疗前差异无统计学意义(P均>0.05)。治疗4周后,对照组和观察组的HAMD评分、HAMA评分、PSQI较治疗前下降,差异有统计学意义(P均<0.05),其中观察组下降更为明显,与对照组相比,差异有统计学意义(P<0.05)。对照组和观察组MBI与治疗前相比,均有明显提高,差异有统计学意义(P<0.05),而观察组和对照组相比,观察组分数提高更显著,差异有统计学意义(P<0.05)。观察组治疗有效率为87.50%,高于对照组的71.25%。两组之间差异有统计学意义(Uc=-3.45,P<0.001)。 结论高频rTMS治疗联合认知行为治疗和认知行为治疗均能有效改善PSA+PSD患者的焦虑抑郁症状、睡眠质量及日常生活能力,但高频rTMS治疗联合认知行为治疗的效果更加明显。  相似文献   
110.
目的调查少数民族地区青少年对新冠疫情的认知及应对情况。方法采用分层抽样的方法,通过“问卷星”在线平台对香格里拉市1949名在校学生进行调查。结果结果显示,81.94%的学生在2020年1月初之前已知晓疫情;83.12%的学生通过电视和微信知晓疫情;9333%的学生认为病毒通过飞沫传播;94.80%的学生会通过戴口罩、不聚餐等方式进行防护;疫情相关知识的正确率为71.44%。不同年龄、性别、民族、专业、生源地、家庭年收入的学生对部分调查问题的差异有统计学意义(P<0.05)。结论学生对疫情认知整体情况较好,部分问题仍有较大提升空间。学校应做好疫情常态化防控,完善心理疏导体系,多措并举,引导学生做好自我防护。  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