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   4969250篇
  免费   389466篇
  国内免费   22176篇
耳鼻咽喉   70249篇
儿科学   155342篇
妇产科学   130920篇
基础医学   743924篇
口腔科学   139238篇
临床医学   461632篇
内科学   897201篇
皮肤病学   115134篇
神经病学   416721篇
特种医学   195731篇
外国民族医学   1175篇
外科学   737065篇
综合类   154536篇
现状与发展   51篇
一般理论   2818篇
预防医学   426165篇
眼科学   117821篇
药学   355172篇
  96篇
中国医学   17009篇
肿瘤学   242892篇
  2021年   59871篇
  2019年   61374篇
  2018年   77845篇
  2017年   60002篇
  2016年   66569篇
  2015年   80461篇
  2014年   116172篇
  2013年   182046篇
  2012年   145794篇
  2011年   153326篇
  2010年   134565篇
  2009年   134284篇
  2008年   136963篇
  2007年   145905篇
  2006年   153593篇
  2005年   147772篇
  2004年   146528篇
  2003年   136395篇
  2002年   125954篇
  2001年   183944篇
  2000年   181132篇
  1999年   164317篇
  1998年   75691篇
  1997年   70965篇
  1996年   68652篇
  1995年   64542篇
  1994年   58617篇
  1993年   54221篇
  1992年   123388篇
  1991年   118914篇
  1990年   113978篇
  1989年   110394篇
  1988年   102524篇
  1987年   100760篇
  1986年   95878篇
  1985年   93515篇
  1984年   76908篇
  1983年   67927篇
  1982年   51863篇
  1981年   48093篇
  1980年   45219篇
  1979年   68772篇
  1978年   54059篇
  1977年   47138篇
  1976年   44360篇
  1975年   44245篇
  1974年   50692篇
  1973年   48884篇
  1972年   45805篇
  1971年   42325篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
PurposeUnderstanding the value of genetic screening and testing for monogenic disorders requires high-quality, methodologically robust economic evaluations. This systematic review sought to assess the methodological quality among such studies and examined opportunities for improvement.MethodsWe searched PubMed, Cochrane, Embase, and Web of Science for economic evaluations of genetic screening/testing (2013-2019). Methodological rigor and adherence to best practices were systematically assessed using the British Medical Journal checklist.ResultsAcross the 47 identified studies, there were substantial variations in modeling approaches, reporting detail, and sophistication. Models ranged from simple decision trees to individual-level microsimulations that compared between 2 and >20 alternative interventions. Many studies failed to report sufficient detail to enable replication or did not justify modeling assumptions, especially for costing methods and utility values. Meta-analyses, systematic reviews, or calibration were rarely used to derive parameter estimates. Nearly all studies conducted some sensitivity analysis, and more sophisticated studies implemented probabilistic sensitivity/uncertainty analysis, threshold analysis, and value of information analysis.ConclusionWe describe a heterogeneous body of work and present recommendations and exemplar studies across the methodological domains of (1) perspective, scope, and parameter selection; (2) use of uncertainty/sensitivity analyses; and (3) reporting transparency for improvement in the economic evaluation of genetic screening/testing.  相似文献   
22.

The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.

  相似文献   
23.
目的探讨脊髓小脑共济失调2型(SCA2)致病基因ATXN2异常等位基因中间重复个体的表型和分子遗传学特点。方法针对2005—2018年中日友好医院神经科运动障碍与神经遗传病研究中心收集的1383个常染色体显性遗传共济失调家系的先证者和部分家系成员,采用荧光标记毛细管电泳片段分析方法进行动态突变检测,对携带ATXN2基因中间重复的个体进行临床表型和遗传特征分析。结果共检出163个家系(包含先证者和家系成员共203人)携带异常扩展的ATXN2基因CAG重复序列,其中93个家系中有107例的异常扩展等位基因重复次数在29~34次之间。在其中的20个亲子对中,父系遗传16个,异常等位基因的代间扩展增加0~28次,母系遗传4个,异常等位基因的代间扩展增加0~4次。结论对于临床拟诊SCA2家系患者,需对其亲代或成年子代个体进行ATXN2基因检测,以免漏诊。动态突变基因检测有助于识别中间重复的个体,对明确家系致病基因和遗传咨询至关重要。  相似文献   
24.
25.
Journal of Behavioral Medicine - Evidence supports the use of graphic warnings to educate the public about the health harms of smoking and suggests warnings eliciting negative emotional responses...  相似文献   
26.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T2-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T2-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis.  相似文献   
27.
28.
Collagens are the most abundant proteins in the extracellular matrix. They provide a framework to build organs and tissues and give structural support to make them resistant to mechanical load and forces. Several intra‐ and extracellular modifications are needed to make functional collagen molecules, intracellular post‐translational modifications of proline and lysine residues having key roles in this. In this article, we provide a review on the enzymes responsible for the proline and lysine modifications, that is collagen prolyl 4‐hydroxylases, 3‐hydroxylases and lysyl hydroxylases, and discuss their biological functions and involvement in diseases.  相似文献   
29.
30.
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