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   88380篇
  免费   9129篇
  国内免费   5769篇
耳鼻咽喉   983篇
儿科学   1239篇
妇产科学   806篇
基础医学   7053篇
口腔科学   1790篇
临床医学   11238篇
内科学   9389篇
皮肤病学   852篇
神经病学   2680篇
特种医学   3087篇
外国民族医学   20篇
外科学   8713篇
综合类   21059篇
现状与发展   20篇
一般理论   2篇
预防医学   9086篇
眼科学   1665篇
药学   10669篇
  122篇
中国医学   7760篇
肿瘤学   5045篇
  2024年   1188篇
  2023年   1512篇
  2022年   3680篇
  2021年   4436篇
  2020年   3739篇
  2019年   2432篇
  2018年   2499篇
  2017年   2744篇
  2016年   2426篇
  2015年   3975篇
  2014年   5004篇
  2013年   5472篇
  2012年   7775篇
  2011年   8015篇
  2010年   6743篇
  2009年   5863篇
  2008年   6111篇
  2007年   5915篇
  2006年   5244篇
  2005年   4283篇
  2004年   3230篇
  2003年   2816篇
  2002年   2311篇
  2001年   1869篇
  2000年   1380篇
  1999年   688篇
  1998年   339篇
  1997年   328篇
  1996年   249篇
  1995年   201篇
  1994年   203篇
  1993年   113篇
  1992年   101篇
  1991年   80篇
  1990年   88篇
  1989年   52篇
  1988年   45篇
  1987年   38篇
  1986年   30篇
  1985年   13篇
  1984年   15篇
  1983年   12篇
  1982年   4篇
  1981年   3篇
  1980年   2篇
  1976年   3篇
  1963年   1篇
  1957年   1篇
  1956年   2篇
  1953年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
目的 观察营养素食预防化疗患者便秘的效果。方法 选择128例化疗患者,随机分为观察组和对照组各61例,对照组常规正常饮食,观察组于化疗开始当天实施营养素食.连续7~10d,比较两组患者便秘发生率及体重、血红蛋白、白蛋白等指标。结果 对照组便秘发生率显著高于观察组(P〈0.01);两组化疗后营养指标比较,差异无显著性意义(均P〉0.05)。结论 营养素食对化疗患者便秘有较好的预防作用。  相似文献   
22.
目的研究大肠癌的发病情况、病理类型及临床表现并探讨其临床意义。方法回顾该院1987~2006年经大肠镜及病理检查确珍的大肠癌病例,对比性分析老年组(≥60岁)和非老年组(〈60岁)前10年(1987~1996年)及后10年(1997~2006年)大肠癌发病特点。结果后10年大肠癌发病率显著上升,主要以老年组增高为主,非老年组增加不明显。老年组与非老年组大肠癌的发病部位相同,依次为直肠、左半结肠、右半结肠,最好发的部位为直肠、乙状结肠。病理类型仍然为肿块型、溃疡型和浸润型。血便、黏液脓血便仍然是大肠癌最常见的临床表现。结论20年间大肠癌发病率迅速上升,前10年仅占26.2%,后10年占73.8%,老年组发病率明显增高。老年组与非老年组其发病部位、病理类型、临床表现差异均无显著性。  相似文献   
23.
To explore the electrophysiological proper-ties of differentiation of rat bone marrow-derived stromal stem cells (rBMSCs) to neuron-like cells in vitro by edaravone, a new type of free radical scavenger. Methods: Stromal stem cells were separated from rat bone marrow with Ficoll-Paque reagent and expanded in different culture medium in vitro, rBMSCs were induced by edaravone containing serum-free L-DMEM. Morphologic observation and Western blot analysis including the ex-pression of Nav1.6, Kv1.2, Kv1.3, Cav1.2 were performed, and whole patch-clamp technique was used. Results: Cyton contraction and long processes were shown in differentiated stromal stem cells. Nav1.6, Kv1.2, Kv1.3 and Cav1.2 were expressed in both differentiated and undifferentiated cells. However, the expression of channel proteins in differentiated cells was up-regulated. Consistently, their resting potential and outward currents were also enhanced in the differentiated cells, which was especially significant in the outward rectifier potassium current. Conclusion: In vitro, neuron-like cells derived from rBMSCs, induced by edaravone, possess electrophysiologi-cal properties of neurons.  相似文献   
24.
This work studies formic acid as an anode fuel for polymer electrolyte fuel cells and investigates the electro-oxidation of formic acid on Pt/C. Fuel crossovers through the Nafion® 115 membrane at different temperatures and concentrations are reported. A linear dependence of the crossover current on the temperature and concentration is obtained. It is found that the crossover can be reduced by five times and a higher performance can be rendered by formic acid when compared to methanol under the same conditions. Electrochemical impedance measurements are conducted to interpret the reaction mechanism of formic acid oxidation. The effect of the electrode potential on the impedance pattern is revealed and an impedance model incorporating the reaction kinetics information is developed to simulate the experimental impedance response.  相似文献   
25.
对慢性心力衰竭病人治疗与护理的研究进展   总被引:1,自引:0,他引:1  
王新  王丽姿 《护理研究》2008,22(9):757-759
心力衰竭已日益成为心血管病中对病人危害最大的疾病,因此对心力衰竭病人的治疗与护理应引起重视,现对心力衰竭病人的治疗与护理的研究进展进行了综述.  相似文献   
26.
OxygenationofLiverTransplantsasaPredictorofSuccessYEQifa(DepartmentofSurgery,TongjiHospital,TongjiMedicalUniversity,Wuhan4300...  相似文献   
27.
胆道支撑管显影材料的制备及体外细胞毒性评价   总被引:4,自引:0,他引:4  
目的 探讨新型显影胆道支撑管材料制备的可行性,对构建出的材料进行体外细胞毒性评价和筛选。方法 选择具有X线下显影特性的基础材料A、B、C,分别与硅橡胶生胶共混炼,模压后分别得到相应的显影复合材料甲、乙、丙,经一段和二段硫化过程完成加工。采用MTT法作为体外细胞毒性评价的方法,测定参比对照材料和新材料的50%浓度的浸提液对小鼠成纤维细胞的增殖率的影响,确定细胞毒性级别。结果 新材料甲、乙、丙在x线下影像清晰。甲、乙材料的细胞毒性级别为零,丙材料细胞毒性级别为2。结论 构建出在X线下显影的弹性体材料可行。材料甲、乙是制造新型胆道支撑管的初选材料,材料丙无应用的价值。  相似文献   
28.
目的:探讨半夏泻心汤及其类方不同配伍对正常大鼠粘液含量的影响.方法:用均匀设计法对半夏泻心汤及其类方进行组方药量变化,以胃粘液含量为药理学指标,对所得的药理实验数据进行逐步回归分析.结果:与胃粘液含量关联度最大的为黄连,可以显著降低其含量,其次对半夏、大枣和甘草的交互项,可增加胃粘液含量.药物之间存在复杂的交互作用.结论:均匀设计为研究类方配伍提供了一种可供参考的试验设计方法.  相似文献   
29.
PURPOSE: To examine the relationship between ametropia and optical aberrations in a population of 200 normal human eyes with refractive errors spanning the range from +5.00 to -10.00 D. METHODS: Using a reduced-eye model of ametropia, we tested the hypothesis that the optical system of the eye is uncorrelated with the degree of ametropia. These predictions were evaluated experimentally with a Shack-Hartmann aberrometer that measured the monochromatic aberrations across the central 6 mm of the dilated pupil in well-corrected, cyclopleged eyes. RESULTS: Optical theory predicted, and control experiments on a model eye verified, that Shack-Hartmann measurements of spherical aberration will vary with axial elongation of the eye even if the dioptric components of the eye are fixed. Contrary to these predictions, spherical aberration was not significantly different from emmetropic eyes. Root mean square of third-order aberrations, fourth-order aberrations, and total higher aberrations (third to 10th) in myopic and hyperopic eyes were also uncorrelated with refractive error. Astigmatic eyes tended to have larger total higher-order aberrations than nonastigmatic eyes. CONCLUSIONS: We conclude that a reduced-eye model of myopia assuming fixed optical parameters and variable axial length is not tenable.  相似文献   
30.
Repeated measures of wavefront aberrations were taken along the line-of-sight of seven eyes using two instruments: an objective, cross-cylinder aberroscope (OA) and a Shack-Hartmann (SH) aberrometer. Both instruments were implemented on the same optical table to facilitate interleaved measurements on the same eyes under similar experimental conditions. Variability of repeated measures of individual coefficients tended to be much greater for OA data than for SH data. Although Zernike coefficients obtained from a single measurement were generally larger when measured with the OA than with the SH, the averages across five trials were often smaller for the OA. The Zernike coefficients obtained from the two instruments were not significantly correlated. Radial modulation-transfer functions and point-spread functions derived from the two sets of measurements were similar for some subjects, but not all. When average Zernike coefficients were used to determine optical quality, the OA indicated superior optics in some eyes, but the reverse trend was true if Zernike coefficients from individual trials were used. Possible reasons for discrepancies between the OA and SH measurements include difference in sampling density, quality of data images, alignment errors, and temporal fluctuations. Multivariate statistical analysis indicated that the SH aberrometer discriminated between subjects much better than did the objective aberroscope.  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