全文获取类型
收费全文 | 1598824篇 |
免费 | 38719篇 |
国内免费 | 12843篇 |
专业分类
电工技术 | 42050篇 |
技术理论 | 9篇 |
综合类 | 14945篇 |
化学工业 | 288455篇 |
金属工艺 | 70567篇 |
机械仪表 | 49594篇 |
建筑科学 | 54497篇 |
矿业工程 | 14563篇 |
能源动力 | 53314篇 |
轻工业 | 117082篇 |
水利工程 | 17428篇 |
石油天然气 | 43149篇 |
武器工业 | 1174篇 |
无线电 | 209008篇 |
一般工业技术 | 292164篇 |
冶金工业 | 162717篇 |
原子能技术 | 35492篇 |
自动化技术 | 184178篇 |
出版年
2022年 | 14259篇 |
2021年 | 20920篇 |
2020年 | 15838篇 |
2019年 | 17737篇 |
2018年 | 19054篇 |
2017年 | 18708篇 |
2016年 | 24476篇 |
2015年 | 22017篇 |
2014年 | 34402篇 |
2013年 | 94511篇 |
2012年 | 42375篇 |
2011年 | 54896篇 |
2010年 | 49140篇 |
2009年 | 57365篇 |
2008年 | 50446篇 |
2007年 | 47017篇 |
2006年 | 49779篇 |
2005年 | 43762篇 |
2004年 | 44501篇 |
2003年 | 44375篇 |
2002年 | 43608篇 |
2001年 | 40034篇 |
2000年 | 37855篇 |
1999年 | 36813篇 |
1998年 | 44315篇 |
1997年 | 39147篇 |
1996年 | 35792篇 |
1995年 | 31390篇 |
1994年 | 29358篇 |
1993年 | 28907篇 |
1992年 | 26525篇 |
1991年 | 23572篇 |
1990年 | 23732篇 |
1989年 | 22788篇 |
1988年 | 21249篇 |
1987年 | 19467篇 |
1986年 | 18748篇 |
1985年 | 22068篇 |
1984年 | 22260篇 |
1983年 | 20232篇 |
1982年 | 19270篇 |
1981年 | 19357篇 |
1980年 | 17967篇 |
1979年 | 18484篇 |
1978年 | 17752篇 |
1977年 | 17537篇 |
1976年 | 18773篇 |
1975年 | 16006篇 |
1974年 | 15517篇 |
1973年 | 15575篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Antti Voss Niko Hänninen Mohammad Pour-Ghaz Marko Vauhkonen Aku Seppänen 《Materials and Structures》2018,51(3):68
The development of visualizing tools to monitor unsaturated moisture flow in cement-based materials is of great importance, as most degradation processes in cement-based materials are connected to and take place in the presence moisture. This paper investigates the ability of electrical capacitance tomography (ECT) to image two-dimensional (2D) unsaturated moisture flow in cement-based materials. In ECT, the electrical permittivity distribution within an object is reconstructed based on measured capacitances between electrodes attached on the object’s surface. In a series of experiments, mortar specimens with and without discrete cracks were imaged with ECT during a 2D moisture ingress. The results show that ECT is able to monitor the evolution of the moisture flow, and to approximate the shape and position of the moisture front. These findings indicate that ECT is a viable method for monitoring and visualizing 2D unsaturated moisture flow in cement-based materials in the presence and absence of discrete cracks. 相似文献
932.
Xueliang Wang Huiqin Yin Wenguan Liu Guojun Yu Jian He Zhongfeng Tang Long Yan 《工业材料与腐蚀》2020,71(6):931-937
Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn5(OH)8Cl2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively. 相似文献
933.
Yejun Wu Bowen Yan Juan Zhou Huizhang Lian Xiaojun Yu Jianxin Zhao Hao Zhang Wei Chen Daming Fan 《Journal of food science》2020,85(10):3282-3292
934.
935.
Prof. Dr. Hans-René Bjørsvik Prof. Dr. Bjørn Tore Gjertsen Dr. Vijayaragavan Elumalai 《ChemMedChem》2020,15(10):862-870
A previously designed and developed 12-step total synthesis that includes [1,1′-biphenyl]-2-amine and carbazole intermediates and that ultimately produces the carbazole alkaloid carbazomycin G was exploited as a screening compound library with the goal of identifying potential lead compound(s) with cytotoxic effect. These compounds were investigated by using in-vitro tests involving the two human cell lines HL-60 and MOLM-13, which both model acute myeloid leukaemia (AML). The in-vitro biological test results were used together with the molecular structures of the various intermediates in a concise SAR analysis. Several of the intermediates revealed cytotoxicity (IC50<10−4 M), although the final natural product carbazomycin G did not reveal cytotoxicity versus the two said human cell lines. 相似文献
936.
K.M. Srinivasamurthy Jagadeesha Angadi V S.P. Kubrin Shiddaling Matteppanavar D.A. Sarychev P. Mohan Kumar Haileeyesus Workineh Azale B. Rudraswamy 《Ceramics International》2018,44(8):9194-9203
Ferrites may contain single domain particles which gets converted into super-paramagnetic state near critical size. To explore the existence of these characteristic feature of ferrites, we have performed magnetization(M-H loop) and Mössbauer spectroscopic studies of Ni2+ substitution effect in Co1-xNixFe2O4 (where x?=?0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated by solution combustion route using mixture of carbamide and glucose as fuels for the first time. As prepared samples exhibit spinel cubic structure with lattice parameters which decreases linearly with increase in Ni2+ concentration. The M-H loops reveals that saturation magnetization(Ms), coercive field(Hc) remanence magnetization(Mr) and magnetron number(ηB) decreases significantly with increasing Ni2+ substitution. The variation of saturation magnetization has been explained on the basis of Neel's molecular field theory. The coercive field(Hc) is found strongly dependent on the concentration of Ni2+ and decrease of coercivity suggests that the particles have single domain and exhibits superparamagnetic behavior. The Mössbauer spectroscopy shows two ferrimagnetically relaxed Zeeman sextets distribution at room temperature. The dependence of Mössbauer parameters such as isomer shift, quadru pole splitting, line width and hyperfine magnetic field on Ni2+ concentration have been discussed. Hence our results suggest that synthesized materials are potential candidate for power transformer application. 相似文献
937.
An agriglass composition containing different oxides acts as a slow release for macro and micro nutrients and was chosen to improve maize yield under most important abiotic stresses which affecting agriculture development; salinity and drought. A field experiment was performed in salt affected soil (EC =?7.5 dSm??1) by using different water deficit rates (I1 = 100, I2 = 85 and I3 = 70% of maize water requirements). Irrigation levels were located in main plots. Every main-plot divided into six sub-plots contained glassy fertilizer treatments [F1 = 55 kg fed?1 with 1/2 mm diameter of agriglass (fed. =?4200 m2), F2 = 55 kg fed?1 with 1 mm diameter, F3 = 80 kg fed?1 with 1/2 mm diameter, F4 = 80 kg fed?1 with 1 mm diameter, F5 = Recommendations of Ministry of Agriculture and F6 = control]. The experimental results demonstrated that, ears, straw, grains and biological yields increased with increasing both water and agriglass rates. Application of agriglass as a slow release fertilizer improved yield more than mineral fertilizer. Some growth parameters, water use efficiency (IWUE), macronutrients concentration and their relations were included. Other studies on residual effect of agriglass and the annual application rates to withstand salinity and drought stress by strategic crops are required. 相似文献
938.
939.
940.