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   105276篇
  免费   10466篇
  国内免费   3168篇
耳鼻咽喉   911篇
儿科学   1244篇
妇产科学   1001篇
基础医学   12475篇
口腔科学   3780篇
临床医学   10888篇
内科学   10995篇
皮肤病学   1323篇
神经病学   7117篇
特种医学   3262篇
外国民族医学   11篇
外科学   7345篇
综合类   15338篇
现状与发展   8篇
一般理论   3篇
预防医学   17092篇
眼科学   1281篇
药学   14205篇
  115篇
中国医学   5894篇
肿瘤学   4622篇
  2024年   363篇
  2023年   1900篇
  2022年   3744篇
  2021年   5195篇
  2020年   4897篇
  2019年   4323篇
  2018年   3918篇
  2017年   4190篇
  2016年   4198篇
  2015年   4120篇
  2014年   7261篇
  2013年   7846篇
  2012年   6939篇
  2011年   7301篇
  2010年   5474篇
  2009年   5134篇
  2008年   4891篇
  2007年   4871篇
  2006年   4155篇
  2005年   3636篇
  2004年   3020篇
  2003年   2764篇
  2002年   2163篇
  2001年   2041篇
  2000年   1602篇
  1999年   1400篇
  1998年   1327篇
  1997年   1205篇
  1996年   1059篇
  1995年   953篇
  1994年   915篇
  1993年   715篇
  1992年   689篇
  1991年   582篇
  1990年   501篇
  1989年   520篇
  1988年   441篇
  1987年   382篇
  1986年   309篇
  1985年   403篇
  1984年   313篇
  1983年   191篇
  1982年   219篇
  1981年   181篇
  1980年   166篇
  1979年   127篇
  1978年   81篇
  1977年   58篇
  1976年   78篇
  1974年   49篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
目的总结广州市白云区艾滋病流行特征,评估监测效能,为下一步防治工作的深入开展提供依据。方法运用SAS统计软件对广州市艾滋病疫情数据库中白云区属的病例进行相关描述性统计分析。结果截至2007年底,白云区共发现病例1136例,男女比为3.5:1;年龄以15-49岁为主(94.01%)。传播途径以静脉吸毒为主(61.10%),流动人口占疫情的大部分(71.48%)。性传播(x^2=12.009,P=0.001)和职业人群(x^2=44.935,P=0.001)随年份比例增加;常规监测发现病例日趋增加(x^2=5.533,P=0.019)。结论白云区已进入疫情的快速增长期,疫情主要侵袭青壮年男性,吸毒人群和无业人士所占比例较大。由于白云区在经济和生活上的一些特点,流动人口的疫情负担较重,且传播途径向多元化发展。加大监测力度包括高危人群干预专项和监测效能,将有助于迅速准确的掌握疫情。  相似文献   
992.
Summary Principal components analysis (PCA) was performed on the 1536 spectral and 2944 evoked potential (EP) variables generated by neurophysiologic paradigms including flash VER, click AER, and eyes open and closed spectral EEG from 202 healthy subjects aged 30 to 80. In each case data dimensionality of 1500 to 3000 was substantially reduced using PCA by magnitudes of 20 to over 200. Just 20 PCA factors accounted for 70% to 85% of the variance. Visual inspection of the topographic distribution of factor loading scores revealed complex loadings across multiple data dimensions (time-space and frequency-space). Forty-two non-artifactual factors were successful in classifying age, gender, and a separate group of 60 demented patients by linear discriminant analysis. Discrimination of age and gender primarily involved EP derived factors, whereas dementia primarily involved EEG derived factors. Thirty-eight artifactual factors were identified which, alone, could not discriminate age but were relatively successful in discriminating gender and dementia. The need to parsimoniously develop real neurophysiologic measures and to objectively exclude artifact are discussed. Unrestricted PCA is suggested as a step in this direction.Acknowledgements: This work was supported in part by NIA program project PO1AG049853 to M. Albert and the Mental Retardation Program Project P30HD18655 to J.J. Volpe. We thank our qEEG technologists Adele Mirabella, Susan Katz, Ellen Belles, and Marianne McGaffigan as well as our research secretaries for their unflagging support.  相似文献   
993.
994.
In order to determine whether the coselection observed between the selection trait (active avoidance behavior) of the Roman High Avoidance (RHA) and Roman Low Avoidance (RLA) rat lines and their neuroendocrine characteristics were genetically determined, we analyzed, in nonsegregating (RHA, RLA, and F1) and segregating (F2 and the two backcrosses) crosses, the inheritance pattern and the phenotypic correlations among behavioral (shuttle-box behavior), physiological (body, adrenal, and thymus weights), and neuroendocrine (corticosterone and prolactin reactivity, catecholamine enzyme activities) variables. Physiological characteristics and enzyme activities have acrucial role in sex dissociation. Avoidance behavior and prolactin reactivity to novel environment remained associated in segregating crosses despite gene rearrangement. They represented the most important variables to differentiate the Roman lines, perhaps sharing a common regulatory mechanism under genetic control.  相似文献   
995.
The lymphocyte proliferative response to recall antigens is lost following HIV infection. We sought to devise a means by which the functional immune status of persons in the early stages of HIV infection could be monitored quantitatively. The response to tetanus toxoid was examined in 45 HIV-infected individuals and 11 controls using conventional lymphocyte proliferative assays concurrently with limiting dilution analysis utilizing the secretion of interleukin-2 as the measure of a response. Our data show that the limiting dilution analysis detects tetanus toxoid-reactive T cells in 80% of those tested, as compared to only 44% by proliferation. However, the frequency of tetanus-reactive T cells in HIV-infected individuals (median frequency = 1/59,156) is decrease five-fold as compared to seronegative controls (median frequency = 1/11,599). Longitudinal studies demonstrated a time-dependent decrease in the frequency of tetanus-specific T cell responses in the HIV-infected individuals. Thus, the limiting dilution analysis is a quantitative approach for detecting antigen-specific T cells in HIV-infected individuals, and may be used to monitor changes in T cell function in HIV infection.  相似文献   
996.
近20年来,有限元分析法在脊柱生物力学研究领域中已得到日益广泛的应用.本文就近10年来国外学者用有限元法研究脊柱生物力学的新进展作以综述.详细介绍了椎体、后部结构、间盘、韧带、肌肉组织在生理及病理情况下的生物力学特性,及不同术式、内固定器械对脊柱生物力学的影响;介绍了用有限元法研究某些疾病发病的力学机制的新成果;展望了有限元法应用于脊柱生物力学研究的前景.  相似文献   
997.
Su YN  Lee CN  Hung CC  Chen CA  Cheng WF  Tsao PN  Yu CL  Hsieh FJ 《Human mutation》2003,22(4):326-336
Beta-thalassemia is a common inherited disease, resulting from one or more of a total of more than 200 different mutations in the beta-globin gene (HBB). Efficient and reliable mutation-screening methods are essential in order to establish appropriate prevention programs for at-risk populations based upon a molecular diagnosis. We have developed a rapid and highly-specific mutation screening test for the diagnosis of beta-thalassemia by coupling heteroduplex and primer-extension analysis based on the denaturing high performance liquid chromatography (DHPLC) system. A total of 161 healthy heterozygous Taiwanese carriers featuring 10 different HBB mutations and 30 patients exhibiting 12 different compound heterozygous or homozygous HBB mutations were subjected to DHPLC. The elution profile for the heteroduplex analysis of DHPLC could be successfully used to identify the common disease-causing mutations of HBB. To further confirm the sequence variants, we developed a technique combining multiplex primer-extension analysis coupled with DHPLC for the genotyping of eight common disease-causing mutations in the HBB gene. Overall, by coupling heteroduplex and primer-extension analysis based upon DHPLC, we were able to unambiguously identify the most-common beta-thalassemia mutations corresponding to more than 99% of HBB alleles among the Taiwanese population. In conclusion, compared to classic approaches to mutation screening for this malady, we suggest that DHPLC is an excellent technique to be applied to the genetic screening of prenatal and postnatal individuals as a part of a diagnosis program for beta-thalassemia and provides a more-efficient, economic, and sensitive means to undertake such a screening program.  相似文献   
998.
皮肤穿支血管的解剖学研究   总被引:18,自引:6,他引:18  
目的:对全身皮肤血管区域进行定性和定量分析,确定全身皮肤穿支血管的位置、数量、口径、穿支蒂的长度、类型、来源血管以及穿支所供应皮肤的面积,为穿支皮瓣提供血管解剖基础。方法:选用10具新鲜尸体,采用改良氧化铅一明胶灌注技术进行动脉灌注。将每个口径大于0.5mm的穿支血管进行解剖并记录。拍摄X线片以显示皮肤内血管的形态和分布。定量数据分析包括全身各部位的穿支血管的数量、口径、类型及其供应区域的面积。结果:发现全身128支起源血管发出440支穿支供应皮肤。其中肌皮穿支与肌间隔穿支之比为3:2。穿支平均直径为0.7mm。穿支血管的分布规律如下:①躯干皮肤的血供主要来自肌皮穿支,这些穿支在皮肤内的走行距离和分布范围大于肢体皮肤的穿支。②肢体皮肤的血供主要来自肌间隙穿支血管,主要分布在深筋膜表面,皮神经和浅静脉周围穿支之间形成链式血管吻合。③单位面积的穿支数量与皮肤的移动程度成反比,穿支的口径大小和穿支在皮肤内走行距离与皮肤移动度成正比,与穿支的供应面积成正比。结论:本研究提供详细的皮肤穿支血管解剖数据,为临床设计应用穿支皮瓣提供解剖学依据。  相似文献   
999.
心电信号预处理与心电信号分析   总被引:2,自引:0,他引:2  
本文介绍了在一种便携式心电监护仪器中是如何对心电数据进行预处理和智能分析的.为了适应便携式仪器的特征,我们在心电信号预处理中采用了FFT滤波和滑动平均滤波的方法去除各种干扰并使图像得以平滑,同时采用了差分阈值法提取特征点,考虑到监护仪器的实用性,在心电信号分析阶段,我们采用了分析特征间期异常情况的方法来替代对病症的智能诊断功能。  相似文献   
1000.
Data are presented on the effects of generalized tonic-clonic seizures on the structure of the one-day sleep-waking cycle in Krushinskii-Molodkina (KM) rats, which have a genetic predisposition to audiogenic convulsions. Spectral and correlation analysis of EEG activity in the hippocampus, caudate nucleus, medial central nucleus of the thalamus, and in the somatosensory, visual, and auditory regions of the cortex of these animals was carried out for time intervals before and after convulsions. After seizures, rats showed a prolonged (up to 3.5 h) reduction in fast-wave sleep (FWS) with no subsequent compensatory increase in this shase in the sleep-waking cycle, while a disturbance in slow-wave sleep (SWS) was minor and short-lived (not more than 2 h). It is suggested that generalized paroxysmal attacks predominantly involve disorganization of the function of the systems regulating FWS, while the synchronizing mechanisms of the brain, responsible for SWS, are affected to a lesser extent. Laboratory of the Evolution of Sleep and Waking (Director G. A. Oganesyan), I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 81, No. 10, pp. 1–8, October, 1995.  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