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   3445篇
  免费   183篇
  国内免费   8篇
耳鼻咽喉   58篇
儿科学   284篇
妇产科学   51篇
基础医学   303篇
口腔科学   129篇
临床医学   278篇
内科学   739篇
皮肤病学   67篇
神经病学   138篇
特种医学   78篇
外科学   508篇
综合类   119篇
预防医学   159篇
眼科学   98篇
药学   381篇
中国医学   29篇
肿瘤学   217篇
  2023年   45篇
  2022年   118篇
  2021年   160篇
  2020年   85篇
  2019年   94篇
  2018年   160篇
  2017年   112篇
  2016年   136篇
  2015年   137篇
  2014年   182篇
  2013年   213篇
  2012年   271篇
  2011年   293篇
  2010年   153篇
  2009年   120篇
  2008年   147篇
  2007年   148篇
  2006年   139篇
  2005年   114篇
  2004年   88篇
  2003年   91篇
  2002年   68篇
  2001年   56篇
  2000年   47篇
  1999年   32篇
  1998年   24篇
  1997年   22篇
  1996年   9篇
  1995年   10篇
  1994年   8篇
  1993年   8篇
  1992年   20篇
  1991年   31篇
  1990年   27篇
  1989年   27篇
  1988年   37篇
  1987年   26篇
  1986年   21篇
  1985年   27篇
  1984年   11篇
  1983年   12篇
  1980年   6篇
  1979年   22篇
  1978年   21篇
  1977年   6篇
  1976年   6篇
  1973年   5篇
  1970年   4篇
  1969年   10篇
  1968年   5篇
排序方式: 共有3636条查询结果,搜索用时 14 毫秒
111.
112.
Rationale: Long-term survival after lung transplantation is limited by infectious complications and by bronchiolitis obliterans syndrome (BOS), a form of chronic rejection linked in part to microbial triggers. Objectives: To define microbial populations in the respiratory tract of transplant patients comprehensively using unbiased high-density sequencing. Methods: Lung was sampled by bronchoalveolar lavage (BAL) and upper respiratory tract by oropharyngeal wash (OW). Bacterial 16S rDNA and fungal internal transcribed spacer sequencing was used to profile organisms present. Outlier analysis plots defining taxa enriched in lung relative to OW were used to identify bacteria enriched in lung against a background of oropharyngeal carryover. Measurements and Main Results: Lung transplant recipients had higher bacterial burden in BAL than control subjects, frequent appearance of dominant organisms, greater distance between communities in BAL and OW indicating more distinct populations, and decreased respiratory tract microbial richness and diversity. Fungal populations were typically dominated by Candida in both sites or by Aspergillus in BAL but not OW. 16S outlier analysis identified lung-enriched taxa indicating bacteria replicating in the lower respiratory tract. In some cases this confirmed respiratory cultures but in others revealed enrichment by anaerobic organisms or mixed outgrowth of upper respiratory flora and provided quantitative data on relative abundances of bacteria found by culture. Conclusions: Respiratory tract microbial communities in lung transplant recipients differ in structure and composition from healthy subjects. Outlier analysis can identify specific bacteria replicating in lung. These findings provide novel approaches to address the relationship between microbial communities and transplant outcome and aid in assessing lung infections.  相似文献   
113.
114.
115.
116.
In the present report, an environmentally benign magnetically recoverable nickel(ii)-based nanoreactor as a heterogeneous catalyst has been developed via a template free approach. The catalytic performance of the synthesized catalyst is assessed in the confined oxidative coupling of arenethiols with arylhydrazines to form unsymmetrical diaryl sulfides under aerobic conditions. The salient features of our protocol include oxidant- and ligand-free conditions, use of water as a green solvent, room temperature and formation of nitrogen and water as the only by-products. Moreover, a broad range of functional groups are tolerated well and provide the corresponding diaryl sulfides in moderate to good yields. Moreover, the heterogeneous nature of the catalyst permits facile magnetic recovery and reusability for up to seven runs, making the present protocol highly desirable from industrial and environmental standpoints.

An environmentally benign nickel(ii)-based magnetic nanoreactor has been developed for oxidative coupling of arenethiols with arylhydrazines to form unsymmetrical diaryl sulfides in water at room temperature.  相似文献   
117.
A sensor displaying a rapid response and high sensitivity was developed by following a simple route. Ionic defects in this sensor were explored using X-ray diffraction analysis. In general, such defects arise from a mismatch of ionic radii, which actually improves the sensing performance. SEM and TEM images of the currently produced particles demonstrated negligible agglomeration, which greatly enhanced the flow of water molecules through the particles. The current sensor showed a rapid response to changes in humidity. Its sensing performance was classified into three different ranges of humidity. Of these humidity ranges, the sensor showed the highest sensitivity (8.84 MΩ per %RH) at low relative humidity (10–20% RH). Furthermore, the sensitivity fall off as the RH was increased from 20 to 99%. The sensor showed a rapid response time of 20 s. Also, the sensor showed 92.98% reproducibility and few effects of aging.

A sensor displaying a rapid response and high sensitivity was developed by following a simple route.  相似文献   
118.
A simple synthetic strategy has been developed for the synthesis of 2- and 1-alkyl/aryl/dialkylaminoquinolines and isoquinolines from the easily available quinoline and isoquinoline-N-oxides, different amines, triflic anhydride as activating agent and acetonitrile as solvent in a one-pot reaction under metal-free conditions at 0 °C to room temperature.

A synthetic strategy has been developed for synthesis of 2 and 1-aminoquinolines and isoquinolines from quinoline and isoquinoline-N-oxides, amines and triflic anhydride in acetonitrile at 0 °C to room temperature.  相似文献   
119.
Whatever is excisable, is reconstructable! “You excise, we will reconstruct” are the confident words of reconstructive surgeons today. Reconstruction with multiple flaps has become routine. Radial artery (FRAF), Antero lateral thigh (ALT) and Fibula osteo cutaneous flap (FFOCF) are three most popular free flaps which can reconstruct any defect with excellent asthetics and performance. Radial Artery provides thin, pliable innervated skin; ALT large amount of skin & bulk; and FFOCF strong 22 to 25 centimetres of bone and reliable skin paddle. Free flap survival has gone to 98% in most of the renouned institutes and is an established escalator in management of defects.KEY WORDS: Free flap, head and neck, reconstruction  相似文献   
120.
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