全文获取类型
收费全文 | 3072篇 |
免费 | 184篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 68篇 |
综合类 | 14篇 |
化学工业 | 784篇 |
金属工艺 | 72篇 |
机械仪表 | 87篇 |
建筑科学 | 100篇 |
矿业工程 | 5篇 |
能源动力 | 172篇 |
轻工业 | 369篇 |
水利工程 | 38篇 |
石油天然气 | 78篇 |
武器工业 | 2篇 |
无线电 | 306篇 |
一般工业技术 | 517篇 |
冶金工业 | 196篇 |
原子能技术 | 12篇 |
自动化技术 | 470篇 |
出版年
2023年 | 44篇 |
2022年 | 95篇 |
2021年 | 163篇 |
2020年 | 145篇 |
2019年 | 154篇 |
2018年 | 182篇 |
2017年 | 137篇 |
2016年 | 169篇 |
2015年 | 102篇 |
2014年 | 139篇 |
2013年 | 283篇 |
2012年 | 185篇 |
2011年 | 171篇 |
2010年 | 143篇 |
2009年 | 109篇 |
2008年 | 74篇 |
2007年 | 91篇 |
2006年 | 69篇 |
2005年 | 57篇 |
2004年 | 35篇 |
2003年 | 28篇 |
2002年 | 35篇 |
2001年 | 38篇 |
2000年 | 29篇 |
1999年 | 34篇 |
1998年 | 78篇 |
1997年 | 39篇 |
1996年 | 37篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 25篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 29篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1973年 | 12篇 |
排序方式: 共有3290条查询结果,搜索用时 15 毫秒
1.
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
2.
Mohammed Amin Salih Venkatachalam K. Hubálovský S. Trojovský P. Prabu P. 《Mobile Networks and Applications》2022,27(3):1050-1059
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via... 相似文献
3.
Wireless Personal Communications - Current mobile communications technology relies heavily on efficient design of antennas, where the operational characteristics of the wireless communication... 相似文献
4.
5.
Rauf Tavakoli Bakhshi Puyan Mirarab Meysam Shahbazi Khalil 《Theoretical Foundations of Chemical Engineering》2020,54(5):995-1004
Theoretical Foundations of Chemical Engineering - In this work, with the aim of accurate prediction of water content, H2S and CO2 absorption capacity of diethanolamine (DEA) solvent in Khangiran... 相似文献
6.
7.
8.
Khalil Ghanbari Ali Akbar Golneshan Mohsen Yazdani Hesam Moghadasi Navid Malekian 《亚洲传热研究》2021,50(6):5697-5713
Nanofluids have been known as practical materials to ameliorate heat transfer within diverse industrial systems. The current work presents an empirical study on forced convection effects of Al2O3–water nanofluid within an annulus tube. A laminar flow regime has been considered to perform the experiment in high Reynolds number range using several concentrations of nanofluid. Also, the boundary conditions include a constant uniform heat flux applied on the outer shell and an adiabatic condition to the inner tube. Nanofluid particle is visualized with transmission electron microscopy to figure out the nanofluid particles. Additionally, the pressure drop is obtained by measuring the inlet and outlet pressure with respect to the ambient condition. The experimental results showed that adding nanoparticles to the base fluid will increase the heat transfer coefficient (HTC) and average Nusselt number. In addition, by increasing viscosity effects at maximum Reynolds number of 1140 and increasing nanofluid concentration from 1% to 4% (maximum performance at 4%), HTC increases by 18%. 相似文献
9.
OBJECTIVE: To study the effects of an aldose reductase inhibitor (ARI-509, Wyeth-Ayerst, Princeton, NJ) and aminoguanidine (AMG), agents that have been reported to prevent or delay diabetic retinopathy, on retinal vascular abnormalities and the immunocytochemical expression in the retina of vascular endothelial growth factor (VEGF) in rats maintained for up to 2 years on a 50% galactose diet. METHODS: Albino rats were placed on a control diet, a diet containing 50% galactose, or the 50% galactose diet containing either ARI-509 or AMG. Treatment with ARI-509 or AMG was initiated at the beginning of the experiment or after 12 months of galactose feeding. After 22 to 24 months, the rats were killed and the retinal vasculature from half of one eye was isolated by trypsin-elastase digestion for semiquantitative evaluation of retinal vascular lesions. The other half of the retina was prepared for immunocytochemistry and stained for the presence of VEGF, factor VIII, vimentin, and glial fibrillary acidic protein. Red blood cells, sciatic nerves, and a portion of the retina from the second eye were assayed for glucose, galactose, fructose, sorbitol, galactitol, and myo-inositol. Red blood cells were also assayed for galactosylated hemoglobin. RESULTS: Galactose-fed animals developed a vascular retinopathy characterized by severe cellular loss in the retinal capillaries and intensification of periodic acid-Schiff staining of the vascular basement membranes. Some animals also displayed dilation and hypercellularity of vessels in the posterior retina. These changes were substantially reduced in animals receiving ARI-509 from the beginning of the galactose diet, but were unaffected in all of the other treatment groups. None of the rats receiving ARI-509 or AMG treatment, whether initiated from the onset or after 12 months of galactosemia, demonstrated VEGF immunoreactivity. With the exception of the animals receiving ARI-509 from the beginning of the experiment, all of the galactose-fed animals developed dense cataracts within 6 weeks of the beginning of the galactose diet. Galactitol levels in animals receiving ARI-509 were 86% to 93% lower in red blood cells, retina, and sciatic nerve than those in the other galactose-fed groups. CONCLUSIONS: Although ARI-509 and AMG have different abilities to delay or prevent the diabetic-like retinopathy in galactosemic rats, even when substantial retinal microvascular acellularity occurs, both drugs prevent the immunocytochemical expression of VEGF. These results suggest that factors other than hypoxia may be responsible for VEGF expression in the retina, and that aldose reductase inhibitors and AMG have potential roles in preventing such expression and, thus, perhaps preventing retinal neovascularization. 相似文献
10.
This note presents a high-gain feedback stabilizing control algorithm in which the high-gain parameter is adapted on-line. The algorithm is developed for a class of nonlinear systems which can be viewed as the nonlinear counterpart of uniform rank systems. The system can be unknown except for a number of vital pieces of information. For single-input single-output linear systems such information is usually required in the traditional adaptive control literature. 相似文献