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   3159706篇
  免费   260935篇
  国内免费   13781篇
耳鼻咽喉   43667篇
儿科学   99822篇
妇产科学   81391篇
基础医学   507266篇
口腔科学   84207篇
临床医学   278276篇
内科学   555887篇
皮肤病学   85712篇
神经病学   272367篇
特种医学   125328篇
外国民族医学   361篇
外科学   496714篇
综合类   96708篇
现状与发展   23篇
一般理论   2167篇
预防医学   263746篇
眼科学   71110篇
药学   214237篇
  22篇
中国医学   9194篇
肿瘤学   146217篇
  2021年   54594篇
  2020年   34833篇
  2019年   57777篇
  2018年   70178篇
  2017年   53525篇
  2016年   59050篇
  2015年   73397篇
  2014年   107384篇
  2013年   172416篇
  2012年   83914篇
  2011年   82906篇
  2010年   114134篇
  2009年   119437篇
  2008年   70809篇
  2007年   72805篇
  2006年   83881篇
  2005年   79890篇
  2004年   81831篇
  2003年   73235篇
  2002年   63322篇
  2001年   89196篇
  2000年   81787篇
  1999年   84925篇
  1998年   63413篇
  1997年   61769篇
  1996年   59480篇
  1995年   54925篇
  1994年   49122篇
  1993年   45914篇
  1992年   58539篇
  1991年   55222篇
  1990年   52398篇
  1989年   51795篇
  1988年   48340篇
  1987年   47254篇
  1986年   45303篇
  1985年   45492篇
  1984年   43088篇
  1983年   39914篇
  1982年   39839篇
  1981年   37588篇
  1980年   35551篇
  1979年   35087篇
  1978年   32154篇
  1977年   29700篇
  1976年   27280篇
  1975年   25791篇
  1974年   26281篇
  1973年   25128篇
  1972年   23658篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
991.
992.
In obstetrics and gynaecology, as well as in many other fields of medicine, ultrasound has become an indispensable diagnostic tool. Ultrasound training, however, still lacks proper quality assessment and control. In fact, in prenatal diagnostics most fetal anomalies requiring diagnosis during pregnancy are extremely rare. Therefore, effective training opportunities are limited to the very few medical centres which treat many such cases. Ultrasound simulator-based training, as performed with the Sonofit Sonotrainer, has been demonstrated to partly overcome this dilemma. In this article, the authors summarize their experience in using and evaluating various teaching concepts after the implementation of the ultrasound simulator under different conditions. Furthermore, an overview of the advantages of the Sonotrainer-based ultrasound training and its acceptance among trainees is provided. The authors also focus on aspects of quality assessment in gynaecological and prenatal ultrasound.  相似文献   
993.
994.
A series of 1-alkyl-3,4-dihydroisoquinolines and the related 4-alkyl-1,2-dihydro-benzo[f]isoquinolines was synthesized using reactions of dialkylbenzylcarbinols and their naphthyl analogs with alkylcyanides. Experiments showed that 1-alkyl-6,7-dimethoxy-3,4-dihydroisoquinolines typically produce a hypotensive action, while the benzo-annelated structures usually exhibit a hypertensive effects. The most active compound decreases the arterial pressure in cats by 52 Torr and the effect lasts for about 4 hours. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 3, pp. 15–17, March, 2006.  相似文献   
995.
Extracts of the above-ground part of meadowsweet (Filipendula ulmaria L. Maxim.) demonstrate a pronounced antioxidant activity. It is established that 70% and 95% ethanol extracts contain the most active substances. Investigation of the chemical composition of the above-ground part of the plant and its 70% ethanol extract by means of qualitative reactions, thin-layer chromatography, and paper chromatography showed the presence of various phenolic compounds, including quercetin and its glycosides, dihydroquercetin, apigenin, rododendrol, esculetin, and m-hydroxybenzoic, salicylic, anisic, gallic, gentisic, ferulic, chlorogenic, and caffeic acids. __________ Translated From Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 12, Pp. 22–24, December, 2006.  相似文献   
996.
997.
998.
999.
BACKGROUND: To evaluate potential differences in light absorbing properties and stability of indocyanine green (ICG) adsorbed to the retinal surface and of ICG dissolved in water and balanced salt solution. METHODS: The retina of four human donor eyes was prepared by removing the vitreous from the retinal surface. The inner surface of the specimen was covered with two to three drops of a 0.05% or 0.15% ICG solution respectively. After 1 min, the dye was removed by careful irrigation using BSS plus. The retinal specimens were then investigated by diffuse reflection spectroscopy (UV/VIS/NIR Spectrometer Lambda 900/Perkin Elmer equipped with a PELA-1020 integrating sphere accessory) and their absorption evaluated by the Kubelka-Munk function. To control the sensitivity of the setting, diffuse reflectance spectra of ICG adsorbed to a cellulose membrane and Al(2)O(3) were measured. For comparison, absorption spectra of ICG dissolved in water and BSS plus solution were measured in relation to ICG concentration and time using an UV/VIS/NIR Spectrometer Lambda 900/Perkin Elmer. RESULTS: On the retinal surface, absorption spectra exhibited a steep increase of absorption beginning at 620 nm, with a maximum at 736 nm (0.05%) and a shoulder at 745 (0.15%) and a second maximum at approximately 800 nm for both concentrations. Repeated measurement of the retinal surface 13 days after the ICG exposure revealed no changes in the position of the maxima as compared to the initial measurements. Light absorbing properties of ICG on cellulose or Al(2)O(3) are similar to those seen on the retinal surface with respect to the pattern and location of absorption maxima. In contrast, ICG dissolved in water or BSS plus disclosed variations in absorption characteristics depending on dye concentration, solute and time of measurement. CONCLUSIONS: Absorption characteristics and stability of ICG bound to the retinal surface could be of relevance when investigating potential pathomechanisms of ICG related toxicity, which might be related not only to intraoperative but also to postoperative light exposure of patients after intravitreal use of ICG.  相似文献   
1000.
Consecutive patients (n = 215) who were referred to optometric (55%) or multidisciplinary (45%) low-vision services and above 50 years of age were recruited from four hospitals in the Netherlands. They completed two vision-related quality of life questionnaires, the Vision Quality of Life Core Measure (VCM1) and the Low Vision Quality of Life Questionnaire (LVQOL), before their first visit with low-vision services and 1 year later. At follow-up, patients referred to multidisciplinary low-vision services had lower scores on the mobility subscale of the LVQOL than patients referred to optometric low-vision services [5.3 points; 95% confidence interval (CI): 0.2-10.5]. Paired sample t-tests for the two groups of patients taken together show improvement for the VCM1 (3.1 points; 95% CI: 0.6-5.6) and deterioration for the basic aspects of vision (3.5 points; 95% CI: 1.1-5.9) and the mobility (6.6 points; 95% CI: 3.7-9.5) subscales of the LVQOL. In conclusion, people referred to optometric services showed less deterioration in mobility than those referred to multidisciplinary services. No differences were observed for any of the other subscales of the LVQOL and the VCM1. Future research in this field should include randomized controlled designs comparing low-vision services with no treatment or placebo.  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