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   41186篇
  免费   2592篇
  国内免费   1327篇
耳鼻咽喉   647篇
儿科学   1004篇
妇产科学   633篇
基础医学   4060篇
口腔科学   712篇
临床医学   4137篇
内科学   6008篇
皮肤病学   1848篇
神经病学   2575篇
特种医学   996篇
外国民族医学   1篇
外科学   1771篇
综合类   6015篇
现状与发展   3篇
预防医学   4429篇
眼科学   517篇
药学   6552篇
  28篇
中国医学   2158篇
肿瘤学   1011篇
  2024年   38篇
  2023年   428篇
  2022年   650篇
  2021年   1432篇
  2020年   1212篇
  2019年   1092篇
  2018年   1155篇
  2017年   1186篇
  2016年   1200篇
  2015年   1285篇
  2014年   2449篇
  2013年   2842篇
  2012年   2539篇
  2011年   2687篇
  2010年   2189篇
  2009年   2023篇
  2008年   2068篇
  2007年   2136篇
  2006年   1792篇
  2005年   1680篇
  2004年   1346篇
  2003年   1191篇
  2002年   974篇
  2001年   906篇
  2000年   784篇
  1999年   742篇
  1998年   582篇
  1997年   597篇
  1996年   538篇
  1995年   530篇
  1994年   480篇
  1993年   379篇
  1992年   429篇
  1991年   391篇
  1990年   312篇
  1989年   326篇
  1988年   315篇
  1987年   285篇
  1986年   242篇
  1985年   269篇
  1984年   214篇
  1983年   174篇
  1982年   191篇
  1981年   149篇
  1980年   131篇
  1979年   98篇
  1978年   88篇
  1977年   74篇
  1976年   67篇
  1975年   51篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
目的:观察稀土化合物硝酸钇[Y(NO33]亚慢性(90 d)暴露对大鼠学习记忆能力的影响,并探究其可能的机制,为全面评估稀土元素钇的健康风险提供科学依据。方法:选用刚离乳(PND21)SD雌性大鼠,根据质量随机分为4组,分别为对照组(ddH2O),Y(NO33低剂量组[10 mg/(kg·d)]、中剂量组[40 mg/(kg·d)]和高剂量组[160 mg/(kg·d)],每组15只。连续灌胃受试物90 d后进行旷场实验、高架十字迷宫实验、转棒实验、Morris水迷宫实验。水迷宫检测后,每组取5只雌鼠心脏原位灌注,进行脑组织病理学检查。每组剩余10只雌鼠摘取脑组织,紫外分光光度计检测雌鼠大脑皮质和海马中谷氨酸(Glu)的含量;Western blot检测海马组织中N-甲基-D-天冬氨酸(NMDA)受体蛋白表达情况。结果:与对照组相比,硝酸钇90 d暴露后,转棒实验中160 mg/(kg·d)剂量组大鼠在棒时间、在棒圈数、掉落速度明显升高(P<0.05)。在Morris水迷宫定位航向实验第4天时,40、160 mg/(kg·d)剂量组大鼠逃避潜伏期明显降低(P<0.05);Morris水迷宫空间探索实验中,40 mg/(kg·d)剂量组大鼠穿越平台次数、目标象限游泳时间明显增加(P<0.05);160 mg/(kg·d)剂量组穿越平台次数、进入目标象限次数、目标象限游泳时间明显增加(P<0.05);160 mg/(kg·d)剂量组大鼠东北、东南、西南象限的逃避潜伏期明显低于西北象限的逃避潜伏期(P<0.05)。160 mg/(kg·d)剂量组大鼠海马中Glu含量和NMDA受体NR1含量均明显低于对照组(P<0.05)。40和160 mg/(kg·d)剂量组大鼠海马中NMDA受体NR2A含量明显低于对照组(P<0.05)。结论:硝酸钇亚慢性(90 d)暴露可以引起雌性大鼠空间学习记忆能力增强;硝酸钇可能通过降低海马组织神经元细胞外Glu含量,抑制NMDA受体激活,增强雌性大鼠的空间学习记忆能力。  相似文献   
22.
ObjectivesGrowing evidence of the importance of motor competence for developing a healthy lifestyle has been established in the last decade. Nonetheless, no single instrument or observation tool have been able to fully measure this construct, particularly because most were built for the diagnosis of children in risk for motor impairment; are limited to a few years of the developmental span; lack objectivity in the assessment protocols; or do not include the locomotor, stability, and manipulative components. This led to the difficulty of comparing researches, and longitudinally follow children into adulthood. Recently, a novel proposal to assess motor competence was presented - the Motor Competence Assessment (MCA) - and this study aims to present the MCA normative data from 3-to-23 years.Design and methodsTwo thousand and eighty-seven participants (1102 boys) between 3 and 23 years of age were evaluated in the MCA (standing long jump, 10 m shuttle run, throwing velocity, kicking velocity, lateral jumps, shifting platforms). Results for each test were introduced in the LMS Chartmaker 2.3. The best model for test and sex was used, resulting in normative curves and percentile values.ResultsFinal norms showed a good fit to the instrument developmental expectations, allowing to differentiate and classify performances along the age interval.ConclusionsThe MCA age- and sex- normative values allow to assess motor competence from childhood to early adulthood. Future directions will include obtaining a total MCA score and the normative scores for the MCA components (stability, locomotion, object control), and to expand the norms to adulthood and old age.  相似文献   
23.
24.
25.
26.
27.
The main of this study was to evaluate the mutagenic and carcinogenic potential of (+) – usnic acid (UA), using Somatic Mutation and Recombination Test (SMART) and the test for detecting epithelial tumor clones (wts) in Drosophila melanogaster. Larvae from 72 ± 4 h from Drosophila were fed with UA (5.0, 10.0 or 20.0 mM); urethane (10.0 mM) (positive control); and solvent (Milli-Q water, 1% Tween-80 and 3% ethanol) (negative control). ST cross produced increase in total mutant spots in the individuals treated with 5.0, 10.0 or 20.0 mM of UA. HB cross produced spot frequencies in the concentration of 5.0 mM that were higher than the frequency for the same concentration in the ST cross. In the highest concentrations the result was negative, which means that the difference observed can be attributed, in part, to the high levels of P450, suggesting that increasing the metabolic capacity maximized the toxic effect of these doses. In the evaluation of carcinogenesis using the wts test, the results obtained for the same concentrations of UA show a positive result for the presence of tumors when compared to the negative control. We conclude that UA has recombinogenic, mutagenic and carcinogenic effects on somatic cells in D. melanogaster.  相似文献   
28.
29.
《Vaccine》2020,38(47):7517-7525
BackgroundUnknowing immunity status make migrants vaccine catch-up difficult. The interest of using a rapid tetanus immunotest as the Tétanos Quick Stick® (TQS®) to assess immunity status against tetanus has been evaluated in emergency rooms and it is now commonly used. The study aim was to evaluate TQS® as a tool for migrants’ vaccine catch-up.MethodsFrom December 2018 to February 2019, a prospective study was performed and included consecutively migrants who attented to the primary medicine outconsultation of a health care centre in Paris. Migrants above 18, without any records of tetanus immunization were included and a TQS® was performed during a medical consultation. Adapted vaccine catch-up was then proposed. Immunity against tetanus among migrants, factors associated with positive TQS® and costs savings were evaluated.ResultsTQS® test was positive for 32% of the 310 included patients. In the univariable analysis, factors associated to the presence of a positive TQS® test were a female gender (OR = 1.69 CI95% [1.02–2.80]) and an urban living in the country of origin (OR = 1.79 CI95% [1.07–3.02]). In the multivariable analysis, these factors were not significantly associated to a positive TQS®. Anamnesis was not correlated to the immunity status: only 26% of the migrants who reported vaccinations in childhood, adolescence and adulthood had a positive TQS® test. The use of TQS® test allowed savings of 6,522 US$ as compared to the immediate catch-up strategy for the 310 patients.ConclusionThe TQS® test is an acceptable, simple, rapid and cost saving test that could find a place in the migrants’ vaccine catch-up.  相似文献   
30.
ABSTRACT

Purpose

New instrument-based techniques for anterior chamber (AC) cell counting can offer automation and objectivity above clinician assessment. This review aims to identify such instruments and its correlation with clinician estimates.  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