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   143894篇
  免费   12642篇
  国内免费   6699篇
电工技术   9093篇
技术理论   10篇
综合类   9318篇
化学工业   22960篇
金属工艺   7823篇
机械仪表   8431篇
建筑科学   10607篇
矿业工程   3329篇
能源动力   4327篇
轻工业   10457篇
水利工程   2884篇
石油天然气   6635篇
武器工业   1307篇
无线电   18585篇
一般工业技术   18025篇
冶金工业   7436篇
原子能技术   1690篇
自动化技术   20318篇
  2024年   609篇
  2023年   2224篇
  2022年   4303篇
  2021年   5929篇
  2020年   4234篇
  2019年   3535篇
  2018年   3960篇
  2017年   4497篇
  2016年   3991篇
  2015年   5577篇
  2014年   7037篇
  2013年   8932篇
  2012年   9430篇
  2011年   10401篇
  2010年   9049篇
  2009年   8769篇
  2008年   8582篇
  2007年   8205篇
  2006年   8004篇
  2005年   6573篇
  2004年   4638篇
  2003年   3933篇
  2002年   3994篇
  2001年   3524篇
  2000年   3188篇
  1999年   3232篇
  1998年   2947篇
  1997年   2530篇
  1996年   2182篇
  1995年   1842篇
  1994年   1415篇
  1993年   1186篇
  1992年   924篇
  1991年   726篇
  1990年   568篇
  1989年   484篇
  1988年   399篇
  1987年   268篇
  1986年   237篇
  1985年   216篇
  1984年   134篇
  1983年   111篇
  1982年   104篇
  1981年   96篇
  1980年   76篇
  1979年   56篇
  1978年   42篇
  1977年   48篇
  1976年   76篇
  1973年   35篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Yang  Xi  Gao  Ling  Guo  Qing  Li  Yongjiang  Ma  Yue  Yang  Ju  Gong  Changyang  Yi  Cheng 《Nano Research》2020,13(10):2579-2594

Over the past decade, numerous studies have attempted to enhance the effectiveness of radiotherapy (external beam radiotherapy and internal radioisotope therapy) for cancer treatment. However, the low radiation absorption coefficient and radiation resistance of tumors remain major critical challenges for radiotherapy in the clinic. With the development of nanomedicine, nanomaterials in combination with radiotherapy offer the possibility to improve the efficiency of radiotherapy in tumors. Nanomaterials act not only as radiosensitizers to enhance radiation energy, but also as nanocarriers to deliver therapeutic units in combating radiation resistance. In this review, we discuss opportunities for a synergistic cancer therapy by combining radiotherapy based on nanomaterials designed for chemotherapy, photodynamic therapy, photothermal therapy, gas therapy, genetic therapy, and immunotherapy. We highlight how nanomaterials can be utilized to amplify antitumor radiation responses and describe cooperative enhancement interactions among these synergistic therapies. Moreover, the potential challenges and future prospects of radio-based nanomedicine to maximize their synergistic efficiency for cancer treatment are identified.

  相似文献   
4.
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions.  相似文献   
5.
Rapid synthesis of silver nanowires(Ag NWs) with high quality and a broad processing window is challenging because of the low selectivity of the formation of multiply twinned particles at the nucleation stage for subsequent Ag NWs growth.Herein we report a systematic study of the water-involved heterogeneous nucleation of Ag NWs with high rate(less than 20 min) in a simple and scalable preparation method.Using glycerol as a reducing agent and a solvent with a high boiling point,the reaction is rapidly heated to 210 ℃ in air to synthesize Ag NWs with a very high yield in gram level.It is noted that the addition of a small dose of water plays a key role for obtaining highly pure Ag NWs in high yield,and the optimal water/glycerol ratio is0.25%.After investigating a series of forming factors including reaction temperature and dose of catalysts,the formation kinetics and mechanism of the Ag NWs are proposed.Compared to other preparation methods,our strategy is simple and reproducible.These Ag NWs show a strong Raman enhancement effect for organic molecules on their surface.  相似文献   
6.
7.
文章首先对暑期学校的发展历史和现状进行了分析,指出了现阶段国内高校暑期学校发展中的问题和瓶颈。针对提出的问题,文章剖析了开设暑期学校的理论支撑和实践基础,并结合山东大学九年办学实践经验说明暑期学校在深化教学改革、创新人才培养模式、提高教学质量和办学水平、扩大学校影响力,全面提升学校国际化的积极作用。  相似文献   
8.
9.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
10.
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