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   134957篇
  免费   12475篇
  国内免费   9303篇
耳鼻咽喉   1260篇
儿科学   1605篇
妇产科学   1490篇
基础医学   15274篇
口腔科学   2445篇
临床医学   17335篇
内科学   19175篇
皮肤病学   1379篇
神经病学   7112篇
特种医学   5287篇
外国民族医学   73篇
外科学   14368篇
综合类   24630篇
现状与发展   46篇
一般理论   7篇
预防医学   9220篇
眼科学   3352篇
药学   13877篇
  121篇
中国医学   8001篇
肿瘤学   10678篇
  2024年   384篇
  2023年   2002篇
  2022年   4693篇
  2021年   6843篇
  2020年   5216篇
  2019年   4405篇
  2018年   4539篇
  2017年   4286篇
  2016年   3920篇
  2015年   6338篇
  2014年   7562篇
  2013年   7261篇
  2012年   10754篇
  2011年   11829篇
  2010年   7740篇
  2009年   6132篇
  2008年   7507篇
  2007年   7455篇
  2006年   7181篇
  2005年   6818篇
  2004年   4538篇
  2003年   4170篇
  2002年   3444篇
  2001年   2672篇
  2000年   2777篇
  1999年   2904篇
  1998年   1880篇
  1997年   1782篇
  1996年   1406篇
  1995年   1252篇
  1994年   1029篇
  1993年   709篇
  1992年   831篇
  1991年   733篇
  1990年   660篇
  1989年   571篇
  1988年   472篇
  1987年   414篇
  1986年   312篇
  1985年   257篇
  1984年   168篇
  1983年   128篇
  1982年   92篇
  1981年   96篇
  1980年   77篇
  1979年   75篇
  1978年   47篇
  1975年   39篇
  1974年   39篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 507 毫秒
991.
992.
993.
The biologically active substance P (SP) N-terminal metabolite SP1–7 has been reported to modulate several neural processes such as learning, locomotor activity and reaction to opioid withdrawal. Although all these processes are believed to be associated with dopaminergic transmission no evidence of an interaction between SP1–7 and dopamine in the case of morphine withdrawal has so far been reported. Therefore, in this work we applied in vivo microdialysis to investigate the effect of SP1–7 injection into the ventral tegmental area on dopamine release in nucleus accumbens of male rats during naloxone precipitated morphine withdrawal. The result showed that the heptapeptide enhances dopamine release and also elevates the level of the dopamine metabolite dihydroxyphenylacetic acid in this brain area. It was suggested that the observed action of the SP fragment on the dopamine system represents the underlying mechanism for a previously observed ability of SP1–7 to counteract the aversion response to morphine withdrawal.  相似文献   
994.
We have generated, by ethylmethane sulfonate mutagenesis, loss-of-function mutants in the Drosophila homolog of the mammalian I-kappa B kinase (IKK) complex component IKK gamma (also called NEMO). Our data show that Drosophila IKK gamma is required for the Relish-dependent immune induction of the genes encoding antibacterial peptides and for resistance to infections by Escherichia coli. However, it is not required for the Toll-DIF-dependent antifungal host defense. The results indicate distinct control mechanisms of the Rel-like transactivators DIF and Relish in the Drosophila innate immune response and show that Drosophila Toll does not signal through a IKK gamma-dependent signaling complex. Thus, in contrast to the vertebrate inflammatory response, IKK gamma is required for the activation of only one immune signaling pathway in Drosophila.  相似文献   
995.
T细胞性淋巴瘤组织CD56的检测及其与EB病毒的关系   总被引:3,自引:1,他引:3  
目的探讨T细胞性淋巴瘤(TCL)中CD56的表达情况及CD56阳性表达同爱波斯坦-巴尔病毒(EpsteinBarVirus,EBV)感染的关系。方法对46例TCL进行CD56的免疫组织化学LSAB法检测及EBERs的原位杂交检测。结果(1)46例TCL中8例CD56阳性(17.4%),其中鼻腔、咽部和口腔阳性率最高(5/17例,29.4%)。弥漫性大细胞型淋巴瘤CD56阳性率最高(6/16例,37.5%)。(2)46例TCL中24例EBERs阳性(52.2%)。(3)8例CD56阳性病例中,4例EBERs阳性。结论CD56的表达同TCL发生部位和类型有一定关系。CD56阳性表达与EB病毒感染未发现相关性  相似文献   
996.
戊型肝炎病毒结构区基因的克隆表达及其在诊断中的 …   总被引:1,自引:0,他引:1  
目的 研制戊型肝炎病毒诊断试剂。方法 利用融合蛋白表达载体PGEX-3X表达了戊型肝炎病毒第二读码框区(ORF2402-660)优势怕表位,表达抗原溶于水,可利用商品化的谷胱甘肽Sepharose-4B亲合层析柱得到纯化的抗原。结果 经应用发现,此基因重组抗原作为酶联免疫试剂的抗原,用于检测血清中戊型肝炎病毒抗体,与新加坡进口试剂盒有高度的一致性。和血清中的抗体反应性更强。结论 预示该基因抗原可能  相似文献   
997.
目的评价帕罗西汀合并认知疗法治疗酒依赖伴发抑郁的疗效及对戒酒的影响。方法将98例酒依赖伴发抑郁的患者随机分为研究组和对照组,分别用认知疗法合并帕罗西汀、单用帕罗西汀治疗4个月。用汉密顿抑郁量表(HAMD)评定疗效;用复饮率评定戒酒效果。结果治疗1个月后,研究组HAMD评分16.79±6.50与对照组相近17.88±6.59(P>0.05)。治疗4个月后HAMD评分10.76±5.32、明显低于对照组14.54±5.12(P<0.01);临床疗效(痊愈率44.44%、显效率22.22%、有效率33.34%)明显高于对照组(21.74%、21.74%、56.52%)(P<0.05);复饮率(24.44%)低于对照对照组(45.56%)(P<0.05)。结论认知疗法合并帕罗西汀治疗酒依赖伴发抑郁疗效较好,戒酒效果较好。  相似文献   
998.
We hypothesize that remodelling of action potential and intracellular calcium (Cai) dynamics in the peri-infarct zone contributes to ventricular arrhythmogenesis in the postmyocardial infarction setting. To test this hypothesis, we performed simultaneous optical mapping of Cai and membrane potential ( V m) in the left ventricle in 15 rabbit hearts with myocardial infarction for 1 week. Ventricular premature beats frequently originated from the peri-infarct zone, and 37% showed elevation of Cai prior to V m depolarization, suggesting reverse excitation–contraction coupling as their aetiology. During electrically induced ventricular fibrillation, the highest dominant frequency was in the peri-infarct zone in 61 of 70 episodes. The site of highest dominant frequency had steeper action potential duration restitution and was more susceptible to pacing-induced Cai alternans than sites remote from infarct. Wavebreaks during ventricular fibrillation tended to occur at sites of persistently elevated Cai. Infusion of propranolol flattened action potential duration restitution, reduced wavebreaks and converted ventricular fibrillation to ventricular tachycardia. We conclude that in the subacute phase of myocardial infarction, the peri-infarct zone exhibits regions with steep action potential duration restitution slope and unstable Cai dynamics. These changes may promote ventricular extrasystoles and increase the incidence of wavebreaks during ventricular fibrillation. Whereas increased tissue heterogeneity after subacute myocardial infarction creates a highly arrhythmogenic substrate, dynamic action potential and Cai cycling remodelling also contribute to the initiation and maintenance of ventricular fibrillation in this setting.  相似文献   
999.
结直肠癌与人类乳头状瘤病毒(Human papilloma virus,HPV)感染有一定的关系,但由于检测方法、标本选择及样本数量不同,各研究结果之间差异很大。为进一步明确结直肠癌变与HPV16感染的关系,采用多聚酶链反应(Polymerase chain reaction,PCR)对82例原发性结直肠腺癌患者手术切除的新鲜癌及癌旁正常粘膜组织进行了前瞻性对照研究,检测了组织中HPV16E7DNA的表达并进行测序鉴定。结果显示,结直肠腺癌组织HPV16E7的表达阳性率(42/82)明显高于癌旁正常粘膜组织(4/82);直肠癌组织中HPV16E7的表达(64.10%)明显高于升结肠癌(18.18%),即癌灶部位距肛门越近,感染率越高;HPV16阳性率与Dukes分期相关,Dukes分期越晚感染率越高;与癌组织分化程度无相关性。结果提示结直肠癌的发生、发展可能与HPV16感染有关。  相似文献   
1000.
The simian-human immunodeficiency virus (SHIV)/ macaque model for human immunodeficiency virus type 1 has become a useful tool to assess the role of Vpu in lentivirus pathogenesis. In this report, we have mutated the two phosphorylated serine residues of the HIV-1 Vpu to glycine residues and have reconstructed a SHIV expressing this nonphosphorylated Vpu (SHIV(S52,56G)). Expression studies revealed that this protein was localized to the same intracellular compartment as wild-type Vpu. To determine if this virus was pathogenic, four pig-tailed macaques were inoculated with SHIV(S52,56G) and virus burdens and circulating CD4(+) T cells monitored up to 1 year. Our results indicate that SHIV(S52,56G) caused rapid loss in the circulating CD4(+) T cells within 3 weeks of inoculation in one macaque (CC8X), while the other three macaques developed no or gradual numbers of CD4(+) T cells and a wasting syndrome. Histological examination of tissues revealed that macaque CC8X had lesions in lymphoid tissues (spleen, lymph nodes, and thymus) that were typical for macaques inoculated with pathogenic parental SHIV(KU-1bMC33) and had no lesions within the CNS. To rule out that macaque CC8X had selected for a virus in which there was reversion of the glycine residues at positions 52 and 56 to serine residues and/or compensating mutations occurred in other genes associated with CD4 down-regulation, sequence analysis was performed on amplified vpu sequences isolated from PBMC and from several lymphoid tissues at necropsy. Sequence analysis revealed a reversion of the glycine residues back to serine residues in this macaque. The other macaques maintained low virus burdens, with one macaque (P003) developing a wasting syndrome between months 9 and 11. Histological examination of tissues from this macaque revealed a thymus with severe atrophy that was similar to that of a previously reported macaque inoculated with a SHIV lacking vpu (Virology 293, 2002, 252). Sequence analysis revealed no reversion of the glycine residues in the vpu sequences isolated from this macaque. These results contrast with those from four macaques inoculated with the parental pathogenic SHIV(KU-1bMC33), all of which developed severe CD4(+) T cell loss within 1 month after inoculation. Taken together, these results indicate that casein kinase II phosphorylation sites of Vpu contributes to the pathogenicity of the SHIV(KU-1bMC33) and suggest that the SHIV(KU-1bMC33)/pig-tailed macaque model will be useful in analyzing amino acids/domains of Vpu that contribute to the pathogenesis of HIV-1.  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