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   102354篇
  免费   9712篇
  国内免费   6300篇
电工技术   7438篇
技术理论   7篇
综合类   8287篇
化学工业   15241篇
金属工艺   6256篇
机械仪表   6408篇
建筑科学   8324篇
矿业工程   3435篇
能源动力   2861篇
轻工业   8483篇
水利工程   2500篇
石油天然气   5897篇
武器工业   1027篇
无线电   10876篇
一般工业技术   11127篇
冶金工业   4770篇
原子能技术   1661篇
自动化技术   13768篇
  2024年   494篇
  2023年   1710篇
  2022年   3222篇
  2021年   4414篇
  2020年   3324篇
  2019年   2639篇
  2018年   2954篇
  2017年   3316篇
  2016年   2963篇
  2015年   4085篇
  2014年   5267篇
  2013年   6290篇
  2012年   7302篇
  2011年   7694篇
  2010年   7001篇
  2009年   6756篇
  2008年   6689篇
  2007年   6630篇
  2006年   6249篇
  2005年   5317篇
  2004年   3766篇
  2003年   2886篇
  2002年   2518篇
  2001年   2419篇
  2000年   2303篇
  1999年   2000篇
  1998年   1438篇
  1997年   1207篇
  1996年   1084篇
  1995年   977篇
  1994年   802篇
  1993年   576篇
  1992年   456篇
  1991年   357篇
  1990年   329篇
  1989年   241篇
  1988年   177篇
  1987年   126篇
  1986年   121篇
  1985年   65篇
  1984年   49篇
  1983年   36篇
  1982年   35篇
  1981年   25篇
  1980年   26篇
  1979年   9篇
  1976年   1篇
  1975年   1篇
  1959年   9篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 47 毫秒
101.
102.
103.
104.
TiO_2 nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation(PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO_2 seeding layer for the nucleation of Na_2Ti_3O_7 and H_2Ti_3O_7 mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H_2Ti_3O_7 nanostructures with diverse morphologies and the calcination process can turn the H_2Ti_3O_7 nanostructures into TiO_2 nanostructures with enhanced crystallinity. The morphology of the TiO_2 nanostructures including nanoparticles(NP), nanowhiskers(NWK), nanowires(NW) and nanosheets(NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO_2 photocatalysts were analyzed using scanning electron microscope(SEM), X-ray diffraction(XRD), photoluminescence(PL) spectroscopy and UV–vis absorption spectrum. Photocatalytic tests indicate that the TiO_2 nanosheets calcined at 500?C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO_2 nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO_2 nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application.  相似文献   
105.
Meng  Fanbin  Wang  Ying  Wang  Qiang  Xu  Xiaoling  Jiang  Man  Zhou  Xuesong  He  Ping  Zhou  Zuowan 《Nano Research》2018,11(7):3958-3958
Nano Research - The first author, Fanbin Meng, and the second author, Ying Wang, contributed equally to this work was unfortunately forgotten to write on the first pages of the main text and the...  相似文献   
106.
Jiang  Lei  Ding  Yang  Xue  Xialin  Zhou  Sensen  Li  Cheng  Zhang  Xiaoke  Jiang  Xiqun 《Nano Research》2018,11(11):6062-6073
Nano Research - Developing multifunctional nanoparticles to support new therapy models is a promising and challenging task to address the current dilemma on antitumor treatment. Herein, we...  相似文献   
107.
108.
BACKGROUND AND PURPOSE: Mood disorders are common after stroke and may impede physical, functional, and cognitive recovery, making early identification and treatment of potential importance. We aimed to compare the accuracy of the General Health Questionnaire (GHQ-30) and the Hospital Anxiety and Depression (HAD) Scale in detecting psychiatric morbidity after stroke and to determine the most suitable cutoff points for different purposes. METHODS: One hundred five hospital-referred stroke patients completed both the GHQ-30 and HAD Scale 6 months after onset before a blinded psychiatric assessment in which the Schedule for Affective Disorders and Schizophrenia with some supplementary questions was used to determine a DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) diagnosis. Measures were compared in terms of sensitivity, specificity, and receiver operating characteristic curves. RESULTS: No significant differences were found between the GHQ-30 and the HAD Scale in identifying those patients with any DSM-IV diagnosis (P=0.95), grouped depression (P=0.56), or anxiety (P=0.25) disorders. The previously recommended cutoff points for identifying "cases" for the GHQ (4/5) and for the HAD Scale (8/9 and 11/12) were found to be suboptimal in this population. CONCLUSIONS: The GHQ-30 and HAD scale exhibited similar levels of sensitivity and specificity. Data are presented, taking into account the "cost" of false-positives and negatives, to allow a choice of cutoff points suitable for differing situations.  相似文献   
109.
利用小波的带通性质 ,给出了一种新的小波预处理方法 .实验表明 ,经过小波预处理后提取的特征 ,提高了语音的识别率  相似文献   
110.
研究了二溴对甲基偶氮甲磺与锶生成2:1兰色络合物进行钢中微量锶的测定.该法λ_(max)=638nm,摩尔吸光系数E_(638)=5.01×10~4,锶量在0.02~0.34μg/L范围内服从比尔定律.方法已用于钢中微量锶的测定,结果满意.  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