全文获取类型
收费全文 | 166534篇 |
免费 | 12285篇 |
国内免费 | 6099篇 |
专业分类
电工技术 | 8692篇 |
技术理论 | 9篇 |
综合类 | 8744篇 |
化学工业 | 27274篇 |
金属工艺 | 10025篇 |
机械仪表 | 10067篇 |
建筑科学 | 9793篇 |
矿业工程 | 3943篇 |
能源动力 | 3650篇 |
轻工业 | 9361篇 |
水利工程 | 3137篇 |
石油天然气 | 9562篇 |
武器工业 | 1067篇 |
无线电 | 17538篇 |
一般工业技术 | 26789篇 |
冶金工业 | 11100篇 |
原子能技术 | 4828篇 |
自动化技术 | 19339篇 |
出版年
2024年 | 716篇 |
2023年 | 2319篇 |
2022年 | 4603篇 |
2021年 | 6202篇 |
2020年 | 4678篇 |
2019年 | 4015篇 |
2018年 | 5124篇 |
2017年 | 5584篇 |
2016年 | 5146篇 |
2015年 | 5655篇 |
2014年 | 7298篇 |
2013年 | 8898篇 |
2012年 | 9564篇 |
2011年 | 10257篇 |
2010年 | 8716篇 |
2009年 | 8546篇 |
2008年 | 8412篇 |
2007年 | 7900篇 |
2006年 | 7329篇 |
2005年 | 6260篇 |
2004年 | 4784篇 |
2003年 | 4717篇 |
2002年 | 4749篇 |
2001年 | 4335篇 |
2000年 | 3755篇 |
1999年 | 3323篇 |
1998年 | 2627篇 |
1997年 | 2220篇 |
1996年 | 1976篇 |
1995年 | 1744篇 |
1994年 | 1471篇 |
1993年 | 1245篇 |
1992年 | 1222篇 |
1991年 | 1078篇 |
1990年 | 1091篇 |
1989年 | 1010篇 |
1988年 | 896篇 |
1987年 | 843篇 |
1986年 | 763篇 |
1985年 | 715篇 |
1984年 | 701篇 |
1981年 | 668篇 |
1979年 | 736篇 |
1978年 | 777篇 |
1977年 | 739篇 |
1976年 | 755篇 |
1975年 | 713篇 |
1974年 | 719篇 |
1973年 | 723篇 |
1972年 | 705篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Vashchenko S.V. Khudyakov A.Yu. Baiul K.V. Semenov Yu.S. 《Powder Metallurgy and Metal Ceramics》2021,60(3-4):247-256
Powder Metallurgy and Metal Ceramics - The mechanisms of phase interactions in granular media were studied to elaborate the results obtained previously at the Nekrasov Iron and Steel Institute of... 相似文献
122.
以用户为中心的可见光通信协作传输是近年来出现的新架构,这导致虚拟小区之间出现重叠。为避免导频污染问题,每个虚拟小区中的光接入点(AP)或者虚拟小区中选择相同AP的用户发送的训练序列应该是正交的。针对可见光通信中以用户为中心的协作网络,研究训练资源的正交分配问题,提出了一种新的导频分配算法,联合导频分配和用户选择问题,以期最大限度地增加虚拟小区内可被接入的用户数。分析和仿真结果表明,该导频分配方案可以有效改善导频污染问题,提高训练资源利用率,并且相比已有的导频分配方案,性能有所改进。 相似文献
123.
124.
A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart 下载免费PDF全文
Yu Qi Zhihuan Weng Jinyan Wang Shouhai Zhang Lishuai Zong Cheng Liu Xigao Jian 《Polymer International》2018,67(3):322-329
The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry 相似文献
125.
Sukharev S. V. Zabolotskii A. V. Kotrovskii P. V. Turchin M. Yu. 《Refractories and Industrial Ceramics》2020,60(6):539-542
Refractories and Industrial Ceramics - We study the problem of evaluation of the influence of design of the metal receiver of a large-capacity tundish of slab continuous-casting machine on the... 相似文献
126.
Fominski V. Yu. Nevolin V. N. Fominski D. V. Romanov R. I. Gritskevich M. D. 《Technical Physics Letters》2020,46(1):83-86
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air... 相似文献
127.
Kovchavtsev A. P. Aksenov M. S. Nastov’yak A. E. Valisheva N. A. Gorshkov D. V. Sidorov G. Yu. Dmitriev D. V. 《Technical Physics Letters》2020,46(5):469-472
Technical Physics Letters - The C–V characteristics of Au/Al2O3/In0.52Al0.48As and Au/SiO2/In0.52Al0.48As metal–insulator–semiconductor structures have been studied. It has been... 相似文献
128.
129.
Debin Wang Jingsong Liu Mengshi Zeng Chunmei Zhang Huiqin Li Hongtao Yu Ying Yuan Shuren Zhang 《Journal of the American Ceramic Society》2019,102(7):4029-4037
(1-x)Sr0.7Pb0.15Bi0.1TiO3-xBi4Ti3O12 ((1-x)SPBT-xBIT, x = 0-0.125) bulk ceramics were developed and calcined via the solid-state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT-0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT-0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT-0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range. 相似文献
130.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献