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   130365篇
  免费   12232篇
  国内免费   8168篇
耳鼻咽喉   1402篇
儿科学   1853篇
妇产科学   1326篇
基础医学   13086篇
口腔科学   2242篇
临床医学   16722篇
内科学   17655篇
皮肤病学   2000篇
神经病学   5535篇
特种医学   5323篇
外国民族医学   56篇
外科学   12550篇
综合类   24230篇
现状与发展   30篇
一般理论   7篇
预防医学   10711篇
眼科学   3147篇
药学   14560篇
  133篇
中国医学   8874篇
肿瘤学   9323篇
  2024年   488篇
  2023年   1828篇
  2022年   4766篇
  2021年   6293篇
  2020年   4974篇
  2019年   3987篇
  2018年   4158篇
  2017年   4267篇
  2016年   3928篇
  2015年   6310篇
  2014年   7986篇
  2013年   7974篇
  2012年   11542篇
  2011年   12044篇
  2010年   8708篇
  2009年   7190篇
  2008年   8220篇
  2007年   7614篇
  2006年   7361篇
  2005年   6394篇
  2004年   4386篇
  2003年   3943篇
  2002年   3300篇
  2001年   2381篇
  2000年   2045篇
  1999年   1744篇
  1998年   1005篇
  1997年   982篇
  1996年   746篇
  1995年   696篇
  1994年   566篇
  1993年   391篇
  1992年   462篇
  1991年   442篇
  1990年   309篇
  1989年   227篇
  1988年   239篇
  1987年   197篇
  1986年   133篇
  1985年   101篇
  1984年   82篇
  1983年   43篇
  1982年   37篇
  1981年   41篇
  1980年   31篇
  1979年   48篇
  1978年   18篇
  1975年   15篇
  1973年   15篇
  1972年   17篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
The role of cytokines in rhinosinusitis   总被引:1,自引:0,他引:1  
Since the last decade, new insights into inflammatory processes have become possible by investigating the pattern of cytokines in acute and chronic sinus diseases. This review aims to update and discuss the findings of in vitro and in vivo studies concerning the role of cytokines in sinusitis and nasal polyposis. The proinflammatory cytokines interleukin-1beta, interleukin-6 and the neutrophil-chemoattractant interleukin-8 may play a major role in acute sinusitis, as shown in viral and allergic rhinitis. In chronic sinusitis interleukin-3 dominates the cytokine profiles, giving support to a variety of inflammatory cells. Interleukin-5 is a key protein in the pathogenesis of nasal polyposis. Activation and survival of eosinophils in nasal polyps are thought to be regulated by interleukin-5. Further investigation of cytokine expression patterns in inflammatory sinus diseases will lead to a better understanding of their pathogenesis and to a development of new therapeutic modality.  相似文献   
92.
目的 探讨新生儿C6PD缺陷病和晚发性维生素K缺乏症的危害与预防措施。方法 回顾分析1995-2000年儿内科住院的1周-2月(不含2月)的婴儿3104例次,其中病死56例。结果 1周-2月的小婴儿占住院患儿的19.34%,其中新生儿G6PD缺陷病239例,占7.70%;晚发性维生素K缺乏症92例,占2.96%。死因的第2、3位分别是晚发性维生素K缺乏症(13例,占23.21%)和新生儿C6PD缺陷病(12例,占21.43%),两者的病死率分别为14.13%和5.02%,极显著高于(x^2=17.59,P<0.01)或相近于(x^2=0.88,P>0.05)肺炎的3.57%。新生儿G6PD缺陷病合并感染占38.49%、低氧血症占23.35%、低血糖占19.25%、酸中毒占15.90%,继发胆红素脑病占13.81%。晚发性维生素K缺乏症出现抽搐占90.22%、胃肠、注射部位出血占60.89%;CT证实颅内出血占98.91%。结论 1周-2月的小婴儿约占住院患儿的两成,新生儿G6PD缺陷病和晚发性维生素K缺乏症的病死率均很高,两者是除肺炎外最主要的死因。提议制定并推广预防这2种疾病的常规措施,并参照国内外相应的现状拟出其具体内容。  相似文献   
93.
Pleomorphic xanthoastrocytoma (PXA) is a rare, low-grade astrocytic tumor found in the central nervous system. Histologically, the tumor is characterized by markedly pleomorphic and lipidized cells. Although most of the patients have a favorable prognosis, a small number of cases undergoing recurrence or progression to anaplastic astrocytoma were reported. Very few genetic studies have been performed on PXA because of its rarity and the pathogenesis of this neoplasm is largely unknown. In order to provide an overview of genetic alterations in PXA, we performed comparative genomic hybridization to identify chromosomal imbalances (DNA gains and losses) in three cases of PXA. Genetic imbalance was detected on at least one chromosome for each case. One case, which revealed multiple genetic alterations, showed a poor prognosis. DNA gain on chromosome 7 and loss on 8p were demonstrated in two of three cases, suggesting that the candidate gene(s) located on these regions may play a role in the development of PXA. Further studies are needed to identify the residing candidate genes that are involved in the tumorigenesis of PXA. In addition, the histopathological features and previous genetic studies on PXA are reviewed.  相似文献   
94.
The HLA-B51 allele is known to be associated with Behcet's disease (BD) in many ethnic group. However, it has not yet been clarified whether the HLA-B51 gene itself is the pathogenic gene related to BD or whether it is some other gene in linkage disequlibrium with HLA-B51. Recently, the Triplet repeat (GCT/AGC) polymorphism in transmembrane region of the MHC class I chain-related A (MICA) gene was identified. To investigate the association of MICA with BD, we studied the MICA polymorphism in 108 Korean BD patients and 204 healthy controls in relation to the presence of HLA-B51 and clinical manifestations. The triplet repeat polymorphism was determined by polymerase chain reaction (PCR)-denaturing polyacrylamide gel electrophoresis (PAGE). The phenotype frequency of the MICA*A6 allele (relative risk, RR=2.15, p=0.002) and HLA-B51(RR=1.87, p=0.022) were significantly increased in the Korean patients with BD. A strong linkage disequilibrium was observed between the MICA*A6 and HLA-B51 in both the patients with BD and control subjects. Stratification analysis showed that MICA*A6 homozygosity was strongly associated with BD in the HLA-B51-negative population, and HLA-B51 was also associated with MICA*A6-negative population. In conclusion, MICA*A6 rather than HLA-B51 was strongly associated with Korean patients with BD, and the MICA*A6 allele is a useful susceptibility marker of BD, especially in the HLA-B5-negative  相似文献   
95.
人FascDNA的克隆及其在大肠杆菌中表达的研究   总被引:1,自引:1,他引:1  
为获得高质量及充足的Fas蛋白,采用PCR技术调整Fas基因的开放阅读框架,使之与生物素化蛋白基因阅读框架一致;缺失了FascDNA基因的起始密码子并增加一个大肠杆菌偏性终止密码子,构建FascDNA和生物素化融合原核表达质粒PinPoint-Fas。将重组质粒转入大肠杆菌HB101,经500mmolIPTG在37℃条件下诱导4h,SDS-PAGE及Western印迹检测融合蛋白在大肠杆菌得以高效表达,表达量为细菌总蛋白的13.8%。用亲和层析树脂对生物素化融合蛋白进行亲和层析纯化,得到Fas重组的蛋白,且表达的Fas融合蛋白具有抗体结合活性。此蛋白的表达成功将解决Fas膜蛋白不易提取的难题,为深入研究Fas提供了良好材料来源  相似文献   
96.
There is increasing support for the idea that excessive production of proinflammatory mediators such as tumor necrosis factor (TNF) and reactive oxygen species (ROS) contribute to the pathogenesis of cardiac dysfunction. However, the mechanisms by which cytokine/ROS production mediates cardiac dysfunction have not been established. Given that apoptosis signal-regulating kinase 1 (ASK1) is highly expressed in cardiac muscle and that ASK1 is an important mediator in the signaling pathways induced by tumor necrosis factor, interleukin-1, and ROS, we used the yeast two-hybrid system with ASK1 as bait to identify ASK1 substrates from a human heart cDNA library. The cDNA encoding the cardiac troponin T (cTnT) was isolated. ASK1 specifically interacted with cTnT, but not cTnI, in vitro and in vivo via the C-terminal ASK1 domain. ASK1 specifically phosphorylated cTnT in vitro and in vivo. Mutations in cTnT (T194/S198) at an ASK1-phosphorylation consensus sequence significantly reduced phosphorylation by ASK1. ROS-induced ASK1 activation, cTnT phosphorylation, and contractile dysfunction in cardiomyocytes showed similar kinetics. Moreover, overexpression of constitutively active ASK1 induces cTnT phosphorylation and inhibits shortening and calcium transient in adult cardiomyocytes. We conclude that ASK1 plays an important role in regulation of cardiac contractile function by phosphorylating cTnT and may participate in cytokine/ROS-induced pathogenesis of cardiomyopathy and heart failure.  相似文献   
97.
目的 构建小鼠甲胎蛋白(α-Fetoprotein,AFP)与结核杆菌热休克蛋白70(Mycobacterium tuberculosis heat shock protein 70,Mt.HSP70)基因融合载体.并研究其在真核细胞中的表达情况。方法 以pcDNA3.1为基本单位构建AFP及HSP70的融合表达载体,融合基因以G-S-G-G-S连接子连接;用脂质体将系列载体导入COS-7细胞.48h后以免疫化学方法检测其表达。结果 构建的AFP和HSP70的单独及融合表达载体导入COS-7细胞48h后经RT-PCR检测可扩增出相应片段,细胞免疫化学染色为阳性。结论 AFP和HSP70的单独及融合表达载体构建成功,并能在真核细胞中表达。  相似文献   
98.
99.
Attempts at protein transduction into specific restricted brain areas have remained unsuccessful. We attempted targeted, direct in vivo protein transduction by microinjecting beta-galactosidase (beta-gal) with hemagglutinating virus of Japan envelope (HVJ-E) vector into the rat nucleus tractus solitarius (NTS). The medulla oblongata including the NTS was removed 6h post-injection and cryostat sections were histochemically stained to detect beta-gal enzymatic activity. beta-gal-positive cells were present in these sections as was beta-gal activity determined by colorimetric analysis. beta-gal-positive cells were not present in the rats microinjected only beta-gal protein without HVJ-E vector. Our findings suggest that direct in vivo protein transduction into specific restricted brain areas is possible. The type of targeted delivery system we present may have wide applications in the administration of therapeutic proteins to the central nervous system.  相似文献   
100.
在心室晚电位的研究中,我们引入了信号的时间一频率表示法,并根据晚电位的具体特性用Wigner分布法(维格纳分布)把信号表示为在时间及频率空间中的能量分布。由于Wigner分布的优异性质使我们有可能更准确表示出心室晚电位的存在。但当输入信号是两个信号的线性叠加时,Wigner分布的结果会出现一个交叉项,相当于引入干扰。针对此不足,作者介绍改进方案,消除部分交叉项,收到较好的效果,并给出一些仿真及应用实例。  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