全文获取类型
收费全文 | 325649篇 |
免费 | 4640篇 |
国内免费 | 1838篇 |
专业分类
电工技术 | 6395篇 |
综合类 | 3706篇 |
化学工业 | 47172篇 |
金属工艺 | 18130篇 |
机械仪表 | 14059篇 |
建筑科学 | 8536篇 |
矿业工程 | 2489篇 |
能源动力 | 6641篇 |
轻工业 | 21013篇 |
水利工程 | 3982篇 |
石油天然气 | 5517篇 |
武器工业 | 105篇 |
无线电 | 35330篇 |
一般工业技术 | 65254篇 |
冶金工业 | 40998篇 |
原子能技术 | 5574篇 |
自动化技术 | 47226篇 |
出版年
2021年 | 1810篇 |
2020年 | 1289篇 |
2019年 | 1589篇 |
2018年 | 22226篇 |
2017年 | 21923篇 |
2016年 | 15068篇 |
2015年 | 3049篇 |
2014年 | 3628篇 |
2013年 | 8671篇 |
2012年 | 10172篇 |
2011年 | 22374篇 |
2010年 | 19735篇 |
2009年 | 17399篇 |
2008年 | 18069篇 |
2007年 | 20505篇 |
2006年 | 5876篇 |
2005年 | 9617篇 |
2004年 | 7694篇 |
2003年 | 7337篇 |
2002年 | 6229篇 |
2001年 | 5210篇 |
2000年 | 4692篇 |
1999年 | 4472篇 |
1998年 | 10641篇 |
1997年 | 7606篇 |
1996年 | 5840篇 |
1995年 | 4449篇 |
1994年 | 3792篇 |
1993年 | 3684篇 |
1992年 | 2705篇 |
1991年 | 2634篇 |
1990年 | 2443篇 |
1989年 | 2459篇 |
1988年 | 2420篇 |
1987年 | 2139篇 |
1986年 | 2082篇 |
1985年 | 2380篇 |
1984年 | 2193篇 |
1983年 | 2019篇 |
1982年 | 1884篇 |
1981年 | 1948篇 |
1980年 | 1805篇 |
1979年 | 1823篇 |
1978年 | 1776篇 |
1977年 | 2109篇 |
1976年 | 2688篇 |
1975年 | 1557篇 |
1974年 | 1550篇 |
1973年 | 1607篇 |
1972年 | 1352篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
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
6.
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
7.
Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We... 相似文献
8.
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
9.
Abidur Rahman Makoto Kobayashi Kotaro Sugimoto Yuta Endo Manabu Kojima Shigenori Furukawa Takafumi Watanabe Shu Soeda Yuko Hashimoto Keiya Fujimori Hideki Chiba 《International journal of molecular sciences》2021,22(7)
Background: Within the claudin (CLDN) family, CLDN12 mRNA expression is altered in various types of cancer, but its clinicopathological relevance has yet to be established due to the absence of specific antibodies (Abs) with broad applications. Methods: We generated a monoclonal Ab (mAb) against human/mouse CLDN12 and verified its specificity. By performing immunohistochemical staining and semiquantification, we evaluated the relationship between CLDN12 expression and clinicopathological parameters in tissues from 138 cases of cervical cancer. Results: Western blot and immunohistochemical analyses revealed that the established mAb selectively recognized the CLDN12 protein. Twenty six of the 138 cases (18.8%) showed low CLDN12 expression, and the disease-specific survival (DSS) and recurrence-free survival rates were significantly decreased compared with those in the high CLDN12 expression group. We also demonstrated, via univariable and multivariable analyses, that the low CLDN12 expression represents a significant prognostic factor for the DSS of cervical cancer patients (HR 3.412, p = 0.002 and HR 2.615, p = 0.029, respectively). Conclusions: It can be concluded that a reduced CLDN12 expression predicts a poor outcome for cervical cancer. The novel anti-CLDN12 mAb could be a valuable tool to evaluate the biological relevance of the CLDN12 expression in diverse cancer types and other diseases. 相似文献
10.
Khammatova V. V. Gainutdinov R. F. Khammatova E. A. Titova L. V. 《Fibre Chemistry》2021,53(3):204-207
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,... 相似文献