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   62015篇
  免费   4876篇
  国内免费   157篇
耳鼻咽喉   503篇
儿科学   1598篇
妇产科学   1351篇
基础医学   8482篇
口腔科学   845篇
临床医学   6563篇
内科学   12155篇
皮肤病学   1188篇
神经病学   5447篇
特种医学   2082篇
外国民族医学   4篇
外科学   8812篇
综合类   1074篇
一般理论   108篇
预防医学   5588篇
眼科学   1842篇
药学   4565篇
中国医学   61篇
肿瘤学   4780篇
  2023年   304篇
  2022年   483篇
  2021年   1070篇
  2020年   683篇
  2019年   1098篇
  2018年   1180篇
  2017年   957篇
  2016年   1084篇
  2015年   1247篇
  2014年   1830篇
  2013年   2699篇
  2012年   3875篇
  2011年   4059篇
  2010年   2299篇
  2009年   2071篇
  2008年   3609篇
  2007年   3798篇
  2006年   3823篇
  2005年   3891篇
  2004年   3792篇
  2003年   3435篇
  2002年   3256篇
  2001年   895篇
  2000年   785篇
  1999年   858篇
  1998年   774篇
  1997年   705篇
  1996年   643篇
  1995年   604篇
  1994年   520篇
  1993年   518篇
  1992年   643篇
  1991年   597篇
  1990年   512篇
  1989年   493篇
  1988年   478篇
  1987年   424篇
  1986年   427篇
  1985年   453篇
  1984年   425篇
  1983年   407篇
  1982年   441篇
  1981年   450篇
  1980年   353篇
  1979年   302篇
  1978年   324篇
  1977年   310篇
  1976年   251篇
  1975年   250篇
  1974年   290篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
The etiology of cardiac allograft vasculopathy is not known, but may be preceded by both endothelial cell and smooth muscle dysfunction of the epicardial coronary arteries. We here report a case of acute, reversible coronary artery vasospasm which caused a myocardial infarction in a cardiac transplant recipient. The patient had a complex post-transplant course, including an episode of severe vascular rejection several months before this presentation. Interestingly, the event was captured in its early stages because the patient presented with chest pain: a rare event because of the denervation of the transplanted heart. Our ability to document the etiology of this patient's myocardial infarction supports the concept that cardiac allograft vasculopathy is a progressive disease that, in its early stages, may include a reversible component of abnormal vasoreactivity.  相似文献   
54.
55.
Magnetic resonance imaging (MRI) of the oropharyngeal region from 20 adult volunteers using four model inhalation devices (varying mouthpiece diameters, airflow resistances) and tidal breathing was carried out. Statistical analysis (convex hull method) selected 12 scans from 80 data sets representing the extremes of all dimensions in the population. Twelve physical mouth-throat models were made by stereolithography using the exact scan data. The aim was to produce models with varying dimensions to span the adult population, and to investigate if oropharyngeal dimensions affected throat retention for different delivery systems. In an in vitro analysis, the models were used to determine the retention effect of the oropharyngeal airspaces when drug aerosols were administered from four inhalation delivery systems: a pressurised metered dose inhaler (pMDI), two different dry powder inhalers (DPIs A and B), and a nebulizer. The aims of this work were to determine the key parameters governing mouth-throat retention and whether retention was dependent on the delivery system used. Characterizing the throat models by measuring 51 different dimensional variables enabled determination of the most influential variables for dose retention for each inhalation delivery system. Throat model retention was found to be dependent on the delivery system (pMDI approximately DPI(A) > DPI(B) > Neb.). The most influential variable was the total throat model volume. Throat models representing high, median, and low oropharyngeal filtration in healthy adults have been identified.  相似文献   
56.
The calculation of the extent of the ring scotoma around positive lenses, as conventionally taught to students of clinical optics, indicates that the scotoma is of a significant size. Using knife-edge lenses this study shows that the calculations are invalid due to the finite size of the eye's entrance pupil and in many instances the scotoma is shown not to exist. The effect noticed in clinical practice is probably largely due to the frame and the edging techniques used which add to the refractive scotoma which is present with high powered lenses, large apertures and/or small pupil sizes.  相似文献   
57.
The anticancer agent temozolomide labeled with 13C (8-Carbamoyl-3-13C-methylimidazo-[5,1-d]-1,2,3,5-tetrazin-4-(3H)-one), was noninvasively detected in subcutaneous RIF-1 tumors by a selective cross polarization 13C NMR method, at a field strength of 9.4T. Pharmacokinetics of the drug, at a dose of 150 mg/kg, were determined for intravenous and intraperitoneal modes of administration (three animals per mode). The half-life of the drug in the tumors was approximately 60 min. The uptake and clearance of the drug, however, varied significantly between individual hosts, for both modes of administration. These results demonstrate the feasibility of obtaining pharmacokinetics of anticancer agents for individual tumors without the need for a label that might modify drug activity (e.g., fluorine). The variability of the in vivo measurements, even within the same tumor model, demonstrates the necessity of directly monitoring the tumor to evaluate drug pharmacokinetics.  相似文献   
58.
59.
60.
A pharmacist consult service was developed to evaluate the appropriateness of enteral feeding through a permanent ostomy in 24 nonambulatory patients with severe developmental disabilities. Several problems with enteral nutrition were identified. Policies to improve them were instituted, and several educational presentations were made. Pharmacists' actions were implemented, including assessment of energy needs by indirect calorimetry and rearrangement of enteral feeding schedules to achieve optimal nutrition support and pharmacotherapy administration. By the fourth month of the consult service, body weight in these patients increased from 101 ± 6% of baseline to 109 ± 7% (p<0.05). Weight continued to increase through the seventh month of the consult service to 116 ± 12% of baseline (p<0.0001). Measured resting energy expenditure for the group was 889 ± 170 kcal/day compared with the predicted 1055 ± 163 kcal/day.  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