全文获取类型
收费全文 | 668376篇 |
免费 | 9331篇 |
国内免费 | 3427篇 |
专业分类
电工技术 | 12934篇 |
技术理论 | 5篇 |
综合类 | 1804篇 |
化学工业 | 100772篇 |
金属工艺 | 30209篇 |
机械仪表 | 22297篇 |
建筑科学 | 16332篇 |
矿业工程 | 4140篇 |
能源动力 | 15513篇 |
轻工业 | 55283篇 |
水利工程 | 7363篇 |
石油天然气 | 13611篇 |
武器工业 | 288篇 |
无线电 | 73953篇 |
一般工业技术 | 132425篇 |
冶金工业 | 118527篇 |
原子能技术 | 14940篇 |
自动化技术 | 60738篇 |
出版年
2021年 | 5152篇 |
2019年 | 4644篇 |
2018年 | 14016篇 |
2017年 | 14355篇 |
2016年 | 11843篇 |
2015年 | 6379篇 |
2014年 | 9986篇 |
2013年 | 27224篇 |
2012年 | 18311篇 |
2011年 | 28518篇 |
2010年 | 23665篇 |
2009年 | 24761篇 |
2008年 | 25530篇 |
2007年 | 27156篇 |
2006年 | 18223篇 |
2005年 | 19038篇 |
2004年 | 17014篇 |
2003年 | 16066篇 |
2002年 | 15184篇 |
2001年 | 14732篇 |
2000年 | 13974篇 |
1999年 | 14292篇 |
1998年 | 33772篇 |
1997年 | 24350篇 |
1996年 | 18881篇 |
1995年 | 14421篇 |
1994年 | 12764篇 |
1993年 | 12651篇 |
1992年 | 9457篇 |
1991年 | 9093篇 |
1990年 | 8940篇 |
1989年 | 8941篇 |
1988年 | 8373篇 |
1987年 | 7427篇 |
1986年 | 7379篇 |
1985年 | 8332篇 |
1984年 | 7794篇 |
1983年 | 7253篇 |
1982年 | 6571篇 |
1981年 | 6886篇 |
1980年 | 6505篇 |
1979年 | 6446篇 |
1978年 | 6403篇 |
1977年 | 7042篇 |
1976年 | 9276篇 |
1975年 | 5567篇 |
1974年 | 5360篇 |
1973年 | 5439篇 |
1972年 | 4616篇 |
1971年 | 4164篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zienko S. I. Zhbanova V. L. 《Journal of Communications Technology and Electronics》2022,67(4):395-402
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a... 相似文献
2.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state.... 相似文献
3.
4.
Muniyandi Kasipandi Jagadeesan Gayathri George Blassan P. Manoharan Ashwini Lydia Nataraj Gayathri Abrahamse Heidi Thangaraj Parimelazhagan 《Food science and biotechnology》2022,31(13):1717-1728
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and... 相似文献
5.
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
6.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an... 相似文献
7.
Karimi Bayan Chang Yu-Cheng Pekola Jukka P. 《Journal of Low Temperature Physics》2022,207(3-4):220-225
We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.
相似文献8.
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
9.
Kathleen T. Lauser Amy L. Rueter Michelle A. Calabrese 《American Institute of Chemical Engineers》2022,68(12):e17850
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations. 相似文献
10.
Shannon Lee Scott L. Carnahan Georgiy Akopov Philip Yox Lin-Lin Wang Aaron J. Rossini Kui Wu Kirill Kovnir 《Advanced functional materials》2021,31(16):2010293
Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi4P4 and IrSi3P3 are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and 29Si and 31P magic angle spinning NMR. In agreement with previous report RuSi4P4 crystallizes in NCS space group P1, while IrSi3P3 is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi4P4 and IrSi3P3 to be wide bandgap (Eg) semiconductors, Eg = 1.9 and 1.8 eV, respectively. RuSi4P4 and IrSi3P3 outperform the current state-of-the-art infrared SHG material, AgGaS2, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi4P4 and IrSi3P3 are promising candidates for longer wavelength NLO materials. 相似文献