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   4476796篇
  免费   354539篇
  国内免费   15212篇
耳鼻咽喉   62080篇
儿科学   142087篇
妇产科学   116620篇
基础医学   678190篇
口腔科学   122232篇
临床医学   418080篇
内科学   813435篇
皮肤病学   111448篇
神经病学   380313篇
特种医学   173742篇
外国民族医学   762篇
外科学   675112篇
综合类   122485篇
现状与发展   59篇
一般理论   2687篇
预防医学   371229篇
眼科学   104287篇
药学   313823篇
  26篇
中国医学   12113篇
肿瘤学   225737篇
  2021年   58058篇
  2020年   38511篇
  2019年   60382篇
  2018年   78468篇
  2017年   61167篇
  2016年   67619篇
  2015年   80378篇
  2014年   115790篇
  2013年   182040篇
  2012年   131966篇
  2011年   137699篇
  2010年   131153篇
  2009年   133259篇
  2008年   122990篇
  2007年   130502篇
  2006年   139329篇
  2005年   132939篇
  2004年   133470篇
  2003年   123309篇
  2002年   112405篇
  2001年   168476篇
  2000年   163186篇
  1999年   149975篇
  1998年   72985篇
  1997年   68623篇
  1996年   66495篇
  1995年   61789篇
  1994年   55501篇
  1993年   51510篇
  1992年   107345篇
  1991年   102045篇
  1990年   97852篇
  1989年   95346篇
  1988年   87645篇
  1987年   85789篇
  1986年   80662篇
  1985年   78768篇
  1984年   65718篇
  1983年   58473篇
  1982年   47378篇
  1981年   44038篇
  1980年   41232篇
  1979年   55405篇
  1978年   44981篇
  1977年   40161篇
  1976年   37038篇
  1975年   36982篇
  1974年   39837篇
  1973年   37941篇
  1972年   35552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Spray coated pellets as carrier system for mucoadhesive drug nanocrystals.   总被引:1,自引:0,他引:1  
High pressure homogenization can be employed to produce drug nanocrystals with a number of advantages, like improved solubility behaviors, better drug targeting or even increased mucoadhesiveness. To obtain a controlled drug delivery system it is necessary to transform the resulting nanosuspension into a solid dosage form. The present study shows the feasibility to use a mucoadhesive nanosuspension of poorly soluble hydrocortisone acetate produced by high pressure homogenization as layering dispersion in a fluidized bed process, followed by the application of an enteric coating to achieve a controlled drug release. To point out the advantages of drug nanocrystals the new fomulation was compared with a formulation containing micronized drug. Both formulations were characterized with regard to their particle size and crystallinity by using laser diffractometry, photon correlation spectroscopy and X-ray diffraction. The pellet morphology was characterized by using the environmental scanning electron microscopy (ESEM). In the in vitro dissolution tests an accelerated dissolution velocity and an increased drug release could be shown for the pellets containing drug nanocrystals.  相似文献   
992.
Research coordinators in intensive care are a growing specialty about which little is known. This cross-sectional study surveyed the Australia and New Zealand Intensive Care Research Coordinators' Group (n = 49) regarding demographics, education, employment history, job structure, and role content. Most research coordinators were highly qualified and experienced nurses who undertake pharmaceutical trials, multicenter projects, departmental medical and nursing research, audits and data registries, and their own projects.  相似文献   
993.
994.
995.
Surfactant     
Surfactant, a complex substance containing specific proteins and phospholipids, is essential for gas exchange in the lungs. Research shows that surfactant not only lowers surface tension, but also plays a role in host defense. Surfactant replacement therapy is a cornerstone in the treatment of respiratory distress syndrome in premature infants. New information on endogenous surfactant composition including surfactant apoproteins has led to advances in the surfactant replacement products currently available. Because of the success of surfactant deficiency treatment in neonates, surfactant replacement therapy has been studied in both the pediatric and adult population for the treatment of other respiratory disorders. This article describes the composition, metabolism, and function of endogenous surfactant and other uses of surfactant replacement therapies in neonates.  相似文献   
996.
OBJECTIVE: Respiratory muscle endurance of able-bodied persons, assessed by normocapnic hyperpnoea at 70% of their maximal voluntary ventilation, usually ranges from 10 to 20 minutes. The aim of this study was to determine the level of ventilation that patients with paraplegia and tetraplegia can sustain for 10-20 minutes to later be used as the guideline for respiratory muscle endurance training. DESIGN: Pilot study; cross-over setting. SUBJECTS: Two groups, 8 patients with paraplegia and 6 with tetraplegia. METHODS: Respiratory muscle endurance tests were performed at 3 different intensities of normocapnic hyperpnoea, i.e. 20%, 40% and 60% maximal voluntary ventilation. Subjects performed partial re-breathing from a bag to assure normocapnia. Respiratory endurance was separately analysed for patients with paraplegia and tetraplegia. RESULTS: Mean respiratory endurance times were 46.0, 18.9 and 4.2 minutes at 20%, 40% and 60% maximal voluntary ventilation in patients with tetraplegia and 51.8, 38.8 and 12.2 minutes in patients with paraplegia. The duration differed significantly at 60% maximal voluntary ventilation between the groups. CONCLUSION: Minute ventilation to perform respiratory muscle endurance training can be set at around 40% of maximal voluntary ventilation for patients with tetraplegia and around 60% of maximal voluntary ventilation for patients with paraplegia, as these levels can be sustained for 10-20 minutes.  相似文献   
997.
998.
999.
1000.
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