全文获取类型
收费全文 | 64421篇 |
免费 | 5106篇 |
国内免费 | 2838篇 |
专业分类
电工技术 | 3630篇 |
技术理论 | 7篇 |
综合类 | 4230篇 |
化学工业 | 11009篇 |
金属工艺 | 3570篇 |
机械仪表 | 3938篇 |
建筑科学 | 5459篇 |
矿业工程 | 1855篇 |
能源动力 | 1876篇 |
轻工业 | 4055篇 |
水利工程 | 1159篇 |
石油天然气 | 4511篇 |
武器工业 | 450篇 |
无线电 | 7073篇 |
一般工业技术 | 8014篇 |
冶金工业 | 3108篇 |
原子能技术 | 733篇 |
自动化技术 | 7688篇 |
出版年
2024年 | 226篇 |
2023年 | 1040篇 |
2022年 | 1731篇 |
2021年 | 2449篇 |
2020年 | 1895篇 |
2019年 | 1648篇 |
2018年 | 1863篇 |
2017年 | 2095篇 |
2016年 | 1906篇 |
2015年 | 2369篇 |
2014年 | 3215篇 |
2013年 | 3671篇 |
2012年 | 4090篇 |
2011年 | 4430篇 |
2010年 | 3879篇 |
2009年 | 3685篇 |
2008年 | 3611篇 |
2007年 | 3511篇 |
2006年 | 3566篇 |
2005年 | 3086篇 |
2004年 | 2092篇 |
2003年 | 1876篇 |
2002年 | 1645篇 |
2001年 | 1599篇 |
2000年 | 1653篇 |
1999年 | 1771篇 |
1998年 | 1382篇 |
1997年 | 1169篇 |
1996年 | 1051篇 |
1995年 | 936篇 |
1994年 | 769篇 |
1993年 | 556篇 |
1992年 | 433篇 |
1991年 | 336篇 |
1990年 | 312篇 |
1989年 | 226篇 |
1988年 | 175篇 |
1987年 | 107篇 |
1986年 | 105篇 |
1985年 | 60篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Ke Wang Baodan Liu Jing Li Xiaoyuan Liu Yang Zhou Xinglai Zhang Xiaoguo Bi Xin Jiang 《材料科学技术学报》2019,35(4):615-622
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
82.
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
83.
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
84.
85.
X Jiang M Zhang Y Ding J Yao H Chen D Zhu M Muramatu 《Canadian Metallurgical Quarterly》1998,124(5):980-985
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
86.
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
87.
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
88.
研究了香薷、鹤虱等5种药用植物挥发油对仓虫的生物活性作用。结果表明,香薷挥发油的作用最为明显,它(剂量02μL/g)及其粗分离1#~5#样品(剂量005μL/g)均有效地抑制了试虫卵、幼虫及成虫的生长发育,从而减少了试虫F1代种群的发生,其中粗分离1#样品作用尤为突出。香薷挥发油1#~5#样品的主要化学成分为4,5,6,7,8,8a-六氢-8a-甲基-2[1H]-奥酮(5264%)、百里香酚(305%)和一未定成分(2192%)。 相似文献
89.
简述了复合型导电高分子材料的研究及发展,并对其导电机理、基体树脂、导电填料的研究概况进行了述评,介绍了其在各领域中的应用. 相似文献
90.
A study of the dependence of the gain-switched laser operation of chromium forsterite on crystal parameters is presented. Results are reported for a wide range of chromium (IV) ion concentration: 0.02-0.12 at. % and 12-41 figure of merit, with emphasis on performance of the recently developed material with a dopant level of >0.10 at. %. Threshold and slope efficiency calculations are compared with measured performance for all crystals, with variation of pump polarization and output coupling. With 3% output coupling, the lowest threshold of 1.8 mJ, and highest slope efficiency of 13% were measured for a short, high-dopant-level crystal. With 33% output coupling a slope efficiency of 44% was measured for this crystal. Results demonstrate the considerable potential of short, high-dopant-level crystals for applications such as amplification, diode pumping, and narrow-bandwidth operation. 相似文献