全文获取类型
收费全文 | 395234篇 |
免费 | 5367篇 |
国内免费 | 1711篇 |
专业分类
电工技术 | 7709篇 |
综合类 | 353篇 |
化学工业 | 59467篇 |
金属工艺 | 17173篇 |
机械仪表 | 11395篇 |
建筑科学 | 10099篇 |
矿业工程 | 1328篇 |
能源动力 | 10316篇 |
轻工业 | 37640篇 |
水利工程 | 3340篇 |
石油天然气 | 4296篇 |
武器工业 | 5篇 |
无线电 | 47652篇 |
一般工业技术 | 72937篇 |
冶金工业 | 79597篇 |
原子能技术 | 7634篇 |
自动化技术 | 31371篇 |
出版年
2021年 | 2662篇 |
2019年 | 2491篇 |
2018年 | 4117篇 |
2017年 | 4045篇 |
2016年 | 4334篇 |
2015年 | 3280篇 |
2014年 | 5471篇 |
2013年 | 17430篇 |
2012年 | 9342篇 |
2011年 | 13161篇 |
2010年 | 10581篇 |
2009年 | 12022篇 |
2008年 | 12514篇 |
2007年 | 12552篇 |
2006年 | 11249篇 |
2005年 | 10450篇 |
2004年 | 10005篇 |
2003年 | 9726篇 |
2002年 | 9702篇 |
2001年 | 9875篇 |
2000年 | 9108篇 |
1999年 | 9836篇 |
1998年 | 25506篇 |
1997年 | 17980篇 |
1996年 | 13827篇 |
1995年 | 10364篇 |
1994年 | 8994篇 |
1993年 | 8810篇 |
1992年 | 6309篇 |
1991年 | 6161篇 |
1990年 | 5671篇 |
1989年 | 5593篇 |
1988年 | 5513篇 |
1987年 | 4751篇 |
1986年 | 4664篇 |
1985年 | 5485篇 |
1984年 | 4946篇 |
1983年 | 4547篇 |
1982年 | 4229篇 |
1981年 | 4275篇 |
1980年 | 4007篇 |
1979年 | 3887篇 |
1978年 | 3814篇 |
1977年 | 4663篇 |
1976年 | 6580篇 |
1975年 | 3287篇 |
1974年 | 3207篇 |
1973年 | 3222篇 |
1972年 | 2675篇 |
1971年 | 2468篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
F.T. Munna Vidhya Selvanathan K. Sobayel Ghulam Muhammad Nilofar Asim Nowshad Amin Kamaruzzaman Sopian Md. Akhtaruzzaman 《Ceramics International》2021,47(8):11003-11009
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell. 相似文献
3.
4.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
5.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
6.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread... 相似文献
7.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
8.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
9.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
10.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献