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   84093篇
  免费   7673篇
  国内免费   2312篇
耳鼻咽喉   987篇
儿科学   2843篇
妇产科学   823篇
基础医学   6487篇
口腔科学   704篇
临床医学   12828篇
内科学   14459篇
皮肤病学   987篇
神经病学   5219篇
特种医学   2996篇
外国民族医学   2篇
外科学   7735篇
综合类   15262篇
现状与发展   3篇
预防医学   6734篇
眼科学   1044篇
药学   8414篇
  110篇
中国医学   4718篇
肿瘤学   1723篇
  2024年   118篇
  2023年   1314篇
  2022年   2343篇
  2021年   3785篇
  2020年   3928篇
  2019年   3188篇
  2018年   2909篇
  2017年   3296篇
  2016年   3387篇
  2015年   3043篇
  2014年   5766篇
  2013年   5890篇
  2012年   4861篇
  2011年   5169篇
  2010年   4205篇
  2009年   3977篇
  2008年   4012篇
  2007年   4196篇
  2006年   3708篇
  2005年   3199篇
  2004年   2628篇
  2003年   2305篇
  2002年   1898篇
  2001年   1758篇
  2000年   1422篇
  1999年   1283篇
  1998年   990篇
  1997年   956篇
  1996年   809篇
  1995年   880篇
  1994年   825篇
  1993年   652篇
  1992年   679篇
  1991年   561篇
  1990年   503篇
  1989年   449篇
  1988年   423篇
  1987年   390篇
  1986年   326篇
  1985年   319篇
  1984年   318篇
  1983年   191篇
  1982年   224篇
  1981年   151篇
  1980年   135篇
  1979年   145篇
  1978年   136篇
  1977年   100篇
  1976年   98篇
  1975年   77篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Objective: The main pathological change of Parkinson’s disease (PD) is progressive degeneration and necrosis of dopaminergic neurons in the midbrain, forming a Lewy body in many of the remaining neurons. Studies have found that in transgenic Drosophila, mutations in the PTEN-inducible kinase 1 (PINK1) gene may cause indirect flight muscle defects in Drosophila, and mitochondrial structural dysfunction as well.

Methods: In this study, Wnt4 gene overexpression and knockdown were performed in PINK1 mutant PD transgenic Drosophila, and the protective effect of Wnt4 gene on PD transgenic Drosophila and its possible mechanism were explored. The Wnt4 gene was screened in the previous experiment; And by using the PD transgenic Drosophila model of the MHC-Gal4/UAS system, the PINK1 gene could be specifically activated in the Drosophila muscle tissue.

Results: In PINK1 mutation transgenic fruit flies, the Wnt4 gene to study its implication on PD transgenic fruit flies’ wing normality and flight ability. We found that overexpression of Wnt4 gene significantly reduced abnormality rate of PD transgenic Drosophila and improved its flight ability, and then, increased ATP concentration, enhanced mitochondrial membrane potential and normalized mitochondrial morphology were found. All of these findings suggested Wnt4 gene may have a protective effect on PD transgenic fruit flies. Furthermore, in Wnt4 gene overexpression PD transgenic Drosophila, down-regulation autophagy and apoptosis-related proteins Ref(2)P, Pro-Caspase3, and up-regulation of Beclin1, Atg8a, Bcl2 protein were confirmed by Western Blotting.

Conclusion: The results imply that the restoring of mitochondrial function though Wnt4 gene overexpression in the PINK1 mutant transgenic Drosophila may be related to autophagy and/or apoptosis.  相似文献   

42.
Daily exposure to sunlight is known to affect the structure and function of the epidermal basement membrane (BM), as well as epidermal differentiation and epidermal barrier function. The aim of this study is to clarify whether the inhibition of BM‐degrading enzymes such as heparanase and matrix metalloproteinase 9 (MMP‐9) can improve the epidermal barrier function of facial skin, which is exposed to the sun on a daily basis. 1‐(2‐hydroxyethyl)‐2‐imidazolidinone (HEI) was synthesized as an inhibitor of both heparanase and MMP‐9. HEI inhibited not only the BM damage at the DEJ but also epidermal proliferation, differentiation, water contents and transepidermal water loss abnormalities resulting from ultraviolet B (UVB). This was determined in this study by the use of UVB‐induced human cultured skins as compared with the control without HEI. Moreover, topical application of HEI improved epidermal barrier function by increasing water content and decreasing transepidermal water loss in daily sun‐exposed facial skin as compared with non‐treated skins. These results suggest that the inhibition of both heparanase and MMP‐9 is an effective way to care for regularly sun‐exposed facial skin by protecting the BM from damage.  相似文献   
43.
Marginal rate-based analyses are widely used for the analysis of recurrent events in clinical trials. In many areas of application, the events are not instantaneous but rather signal the onset of a symptomatic episode representing a recurrent infection, respiratory exacerbation, or bout of acute depression. In rate-based analyses, it is unclear how to best handle the time during which individuals are experiencing symptoms and hence are not at risk. We derive the limiting value of the Nelson-Aalen estimator and estimators of the regression coefficients under a semiparametric rate-based model in terms of an underlying two-state process. We investigate the impact of the distribution of the episode durations, heterogeneity, and dependence on the asymptotic and finite sample properties of standard estimators. We also consider the impact of these features on power in trials designed to test intervention effects on rate functions. An application to a trial of individuals with herpes simplex virus is given for illustration.  相似文献   
44.
45.
46.
Introduction: In early childhood, wheezing due to lower respiratory tract illness is often associated with infection by commonly known respiratory viruses such as respiratory syncytial virus (RSV) and human rhinovirus (RV). How respiratory viral infections lead to wheeze and/or asthma is an area of active research.

Areas covered: This review provides an updated summary of the published information on the development of post-viral induced atopy and asthma and the mechanisms involved. We focus on the contribution of animal models in identifying pathways that may contribute to atopy and asthma following respiratory virus infection, different polymorphisms that have been associated with asthma development, and current options for disease management and potential future interventions.

Expert commentary: Currently there are no prophylactic therapies that prevent infants infected with respiratory viruses from developing asthma or atopy. Neither are there curative therapies for patients with asthma. Therefore, a better understanding of genetic factors and other associated biomarkers in respiratory viral induced pathogenesis is important for developing effective personalized therapies.  相似文献   

47.
48.
49.
《Clinical neurophysiology》2019,130(5):727-738
ObjectiveFunctional processes in the brain are segregated in both the spatial and spectral domain. Motivated by findings reported at the cortical level in healthy participants we test the hypothesis in the basal ganglia of Parkinson’s disease patients that lower frequency beta band activity relates to motor circuits associated with the upper limb and higher beta frequencies with lower limb movements.MethodsWe recorded local field potentials (LFPs) from the subthalamic nucleus using segmented “directional” DBS leads, during which patients performed repetitive upper and lower limb movements. Movement-related spectral changes in the beta and gamma frequency-ranges and their spatial distributions were compared between limbs.ResultsWe found that the beta desynchronization during leg movements is characterised by a strikingly greater involvement of higher beta frequencies (24–31 Hz), regardless of whether this was contralateral or ipsilateral to the limb moved. The spatial distribution of limb-specific movement-related changes was evident at higher gamma frequencies.ConclusionLimb processing in the basal ganglia is differentially organised in the spectral and spatial domain and can be captured by directional DBS leads.SignificanceThese findings may help to refine the use of the subthalamic LFPs as a control signal for adaptive DBS and neuroprosthetic devices.  相似文献   
50.
目的 分析哮喘儿童血清中血管内皮功能相关标记物的变化情况及其与疾病预后的关系,为儿童哮喘预后的评估提供依据。方法 收集2016年10月-2017年12月在南通大学附属常州儿童医院就诊的89例5~14岁哮喘患儿在哮喘发作期的血清样本和92例健康儿童的血清样本,运用ELISA和其他商用测试盒检测其中内皮功能相关标志物血管内皮生长因子(VEGF)、精氨酸酶I(Arg I)、骨膜蛋白(POSTN)、脂联素(APN)和瘦素的浓度以及诱导型一氧化氮合酶(iNOS)活性,并用高效液相串联质谱(HPLC-MS/MS)检测L-精氨酸、甲基化精氨酸ADMA和SDMA的浓度。此后对哮喘组患儿进行为期1年的随访,记录在此期间出现喘息发作的次数。运用正交偏最小二乘法-判别分析(OPLS-DA)分析数据,筛选对哮喘疾病预后有关键影响的血管内皮功能相关标记物。结果 哮喘组儿童血清中Arg I、POSTN、VEGF和瘦素的含量显著增加,iNOS活性显著增高,L-精氨酸浓度显著下降(P<0.05)。OPLS-DA模型显示,基于内皮功能多标记物哮喘组可以和对照组显著区分,且Arg I、iNOS活性以及VEGF水平的变量重要性因子(VIP)值分别为2.11、1.23、1.09,是区分哮喘组和对照组的关键内皮标记物。随访后1年,随访成功70例,其中反复喘息组(n=27)与非反复喘息组(n=43)相比,血清ADMA和Arg I的含量显著增加,POSTN和APN含量显著减少(P<0.05)。OPLS-DA模型的S-plot图和VIP值排序都表明区分两组的关键内皮标记物是APN、POSTN和Arg I。结论 哮喘儿童血清中多种内皮功能相关的生物标记物稳态失衡,其中APN、POSTN和Arg I对儿童哮喘的疾病预后有较高的预测价值。  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