全文获取类型
收费全文 | 181295篇 |
免费 | 2526篇 |
国内免费 | 741篇 |
专业分类
电工技术 | 3379篇 |
综合类 | 105篇 |
化学工业 | 28647篇 |
金属工艺 | 7890篇 |
机械仪表 | 5308篇 |
建筑科学 | 4502篇 |
矿业工程 | 873篇 |
能源动力 | 4865篇 |
轻工业 | 16589篇 |
水利工程 | 1724篇 |
石油天然气 | 3130篇 |
武器工业 | 2篇 |
无线电 | 20690篇 |
一般工业技术 | 34162篇 |
冶金工业 | 33641篇 |
原子能技术 | 4315篇 |
自动化技术 | 14740篇 |
出版年
2021年 | 1414篇 |
2019年 | 1301篇 |
2018年 | 2157篇 |
2017年 | 2150篇 |
2016年 | 2284篇 |
2015年 | 1665篇 |
2014年 | 2890篇 |
2013年 | 8144篇 |
2012年 | 4812篇 |
2011年 | 6676篇 |
2010年 | 5259篇 |
2009年 | 6142篇 |
2008年 | 6123篇 |
2007年 | 6067篇 |
2006年 | 5227篇 |
2005年 | 4863篇 |
2004年 | 4624篇 |
2003年 | 4290篇 |
2002年 | 4220篇 |
2001年 | 4228篇 |
2000年 | 4000篇 |
1999年 | 4146篇 |
1998年 | 10620篇 |
1997年 | 7531篇 |
1996年 | 5759篇 |
1995年 | 4342篇 |
1994年 | 3707篇 |
1993年 | 3622篇 |
1992年 | 2644篇 |
1991年 | 2587篇 |
1990年 | 2450篇 |
1989年 | 2475篇 |
1988年 | 2423篇 |
1987年 | 2163篇 |
1986年 | 2096篇 |
1985年 | 2390篇 |
1984年 | 2211篇 |
1983年 | 2033篇 |
1982年 | 1891篇 |
1981年 | 1960篇 |
1980年 | 1811篇 |
1979年 | 1825篇 |
1978年 | 1787篇 |
1977年 | 2124篇 |
1976年 | 2719篇 |
1975年 | 1563篇 |
1974年 | 1555篇 |
1973年 | 1611篇 |
1972年 | 1353篇 |
1971年 | 1265篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Chen Wen-Kuo Chang Jing-Rong Chen Long-Sheng Hsu Rui-Yang 《Multimedia Tools and Applications》2022,81(6):8317-8347
Multimedia Tools and Applications - With the advancement of technology and the spread of the COVID19 epidemic, learning can no longer only be done through face-to-face teaching. Numerous digital... 相似文献
2.
3.
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
4.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
5.
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
6.
Ping-Chi Hsu Jia-Ying Jhong Li-Ping Huang Kuo-Hsin Lee Hsin-Pao Chen Yue-Leon Guo 《International journal of molecular sciences》2021,22(8)
Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system. 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.
10.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献