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   123881篇
  免费   11652篇
  国内免费   6428篇
电工技术   8940篇
技术理论   7篇
综合类   8933篇
化学工业   19072篇
金属工艺   7914篇
机械仪表   8212篇
建筑科学   9073篇
矿业工程   3897篇
能源动力   3949篇
轻工业   8388篇
水利工程   2727篇
石油天然气   7037篇
武器工业   1404篇
无线电   14195篇
一般工业技术   13485篇
冶金工业   6096篇
原子能技术   1560篇
自动化技术   17072篇
  2024年   424篇
  2023年   1640篇
  2022年   3343篇
  2021年   4856篇
  2020年   3564篇
  2019年   2913篇
  2018年   3289篇
  2017年   3821篇
  2016年   3562篇
  2015年   4943篇
  2014年   6403篇
  2013年   7399篇
  2012年   8877篇
  2011年   9432篇
  2010年   8776篇
  2009年   8221篇
  2008年   8074篇
  2007年   7700篇
  2006年   7443篇
  2005年   6221篇
  2004年   4453篇
  2003年   4043篇
  2002年   4113篇
  2001年   3494篇
  2000年   2697篇
  1999年   2546篇
  1998年   1747篇
  1997年   1511篇
  1996年   1425篇
  1995年   1195篇
  1994年   944篇
  1993年   620篇
  1992年   488篇
  1991年   386篇
  1990年   320篇
  1989年   258篇
  1988年   209篇
  1987年   141篇
  1986年   112篇
  1985年   67篇
  1984年   63篇
  1983年   47篇
  1982年   42篇
  1981年   38篇
  1980年   25篇
  1979年   12篇
  1978年   9篇
  1977年   11篇
  1976年   14篇
  1975年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry  相似文献   
33.
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   
34.
Yuan  Zhongchen  Yan  Li  Ma  Zongmin 《Requirements Engineering》2020,25(2):213-229
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process....  相似文献   
35.
黎源兴  邓勇 《机械》2015,(1):39-45
分别使用AutoCAD、StruCAD 3D及Solid Works软件在石油井架、底座校核中进行强度分析,AutoCAD软件的主要优势在工程制图领域,兼具强度分析功能,适用于单个形状比较规则的型材强度分析;StruCAD 3D是专门针对大型钢结构进行强度校核的分析软件,具有强大的计算处理功能,兼具风载处理能力,在处理大型、复杂结构的时候应优先考虑应用该软件;当遇到需要进行实体造型、模拟实际情况进行校核时,SolidWorks软件较为方便,可以直观地看到应变情况。  相似文献   
36.
37.
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeN4 species as highly active sites for the ORR.  相似文献   
38.
39.
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.  相似文献   
40.
针对不合格品的高效处置、数据的有效分析对企业质量控制具有深远的意义,其是装备制造领域质量管理研究的重点。文章以SAP接口二次开发、IQS流程建模、数据库建立、系统实用价值等方面展开详细论述,确保质量信息可追溯分析。  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