全文获取类型
收费全文 | 909篇 |
免费 | 123篇 |
国内免费 | 79篇 |
专业分类
电工技术 | 27篇 |
综合类 | 46篇 |
化学工业 | 160篇 |
金属工艺 | 24篇 |
机械仪表 | 31篇 |
建筑科学 | 15篇 |
矿业工程 | 6篇 |
能源动力 | 55篇 |
轻工业 | 142篇 |
水利工程 | 1篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 283篇 |
一般工业技术 | 162篇 |
冶金工业 | 20篇 |
原子能技术 | 33篇 |
自动化技术 | 85篇 |
出版年
2024年 | 5篇 |
2023年 | 24篇 |
2022年 | 36篇 |
2021年 | 57篇 |
2020年 | 51篇 |
2019年 | 47篇 |
2018年 | 24篇 |
2017年 | 38篇 |
2016年 | 46篇 |
2015年 | 50篇 |
2014年 | 58篇 |
2013年 | 52篇 |
2012年 | 59篇 |
2011年 | 67篇 |
2010年 | 52篇 |
2009年 | 32篇 |
2008年 | 43篇 |
2007年 | 40篇 |
2006年 | 39篇 |
2005年 | 23篇 |
2004年 | 36篇 |
2003年 | 28篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 22篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 4篇 |
排序方式: 共有1111条查询结果,搜索用时 15 毫秒
1.
《Advanced Powder Technology》2020,31(12):4585-4597
Focussing on visible light active ferrites for high performance removal of noxious pollutants, we report the synthesis of Mg0.5NixZn0.5-xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, & 0.5) ferrite nanoparticle for degradation of reactive blue-19 (RB-19). Lattice parameters calculated using intense X-ray diffraction (XRD) peaks and Nelson-Riley plots (N-R plot) are in well agreement with each other. The sample Mg0.5Ni0.4Zn0.1Fe2O4 (M5N4) exhibits best performance with 99.5% RB-19 degradation in 90 min under visible light. Photoluminescence (PL) results confirm that recombination of charge carriers is highly reduced in the photocatalyst. Scavenging experiments suggest that O2− radicals were the dominant species responsible for photocatalytic performance. The photocatalytic mechanism was explained in terms of dopant driven shifting of conduction bands and valence bands (calculated by Mott-Schottky plots). The thermodynamic probability of radical generation along with role of redox cycles of metal ions has been discussed in the mechanism. The dye degradation was ascertained by detection of intermediates via mass spectrometry analysis and a possible degradation route was also predicted. The findings in this work provide intriguing opportunities to modify the electronic band structure of spinel ferrites for visible and solar light photocatalytic activity for environmental detoxification. 相似文献
2.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
3.
实验采用复合酶制剂处理美国红鱼,红鱼肉中的蛋白质及各种营养成分的价值都得到了提高,通过优化实验工艺条件,确定了红鱼重组香肠加工生产的最佳加工工艺条件。 相似文献
4.
M. R. Islam R. V. Chelakaea J. G. Neff K. G. Fertitta P. A. Grudowski A. L. Holmes F. J. Ciuba R. D. Dupuis J. E. Fouquet 《Journal of Electronic Materials》1995,24(6):787-792
AlGaAs double heterostructures are grown by low-pressure metalorganic chemical vapor deposition to evaluate the level of oxygen
contamination in different trimethylaluminum sources. Effects of arsine purifiers, misoriented substrates, atmospheric exposure
of the growth chamber, and possible phosphorus contamination are also studied. Extensive characterization is performed on
these films by a variety of methods, including high-resolution x-ray diffraction, photoluminescence (PL), time-resolved photoluminescence,
and secondary-ion mass spectrometry. The PL intensities for structures grown with the low-alkoxide grade are reproducibly
much greater than those grown with the regular-grade TMA1. The use of AsH3 purification improves the PL intensity. 相似文献
5.
Yeast mutants with increased bacterial transposon Tn5 excision 总被引:7,自引:0,他引:7
D A Gordenin Y Y Proscyavichus A L Malkova M V Trofimova A Peterzen 《Yeast (Chichester, England)》1991,7(1):37-50
Five complementing recessive mutations that exhibit increased bacterial transposon Tn5 precise excision in yeast Saccharomyces cerevisiae were obtained by ethylmethanesulfonate treatment. One of these mutations (tex1) was submitted to extensive genetic analysis. tex1 is a recessive temperature-sensitive mutation resulting in a 20-100-fold increase in Tn5 excision. It also has increased frequencies of ochre mutation reversion, of forward mutation to canavanine resistance, and loss of chromosome III or its right arm. The possible mechanism of tex1 effects is discussed. 相似文献
6.
The decomposition of NO and of N2O over a CuZSM-5 zeolite and a Fe-mordenite, respectively, has been studied using tracer techniques. The results demonstrate the high mobility of the lattice oxygen ions in self-diffusion. They afford a possible explanation for the problem of how two extralattice oxygens located at positions remote from each other may combine to form the O2 molecules which are spontaneously desorbed in these redox reactions. They show that a portion of the lattice oxygen mixes into the O2 released on decomposition. The data also show that N18O and N2
18O undergo exchange with the catalyst oxygen under reaction conditions.On leave from Central Research Institute for Chemistry, Hungarian Academy of Sciences, H-1525 Budapest, Hungary. 相似文献
7.
Nadezhda A. Evtushenko Arkadii K. Beilin Erdem B. Dashinimaev Rustam H. Ziganshin Anastasiya V. Kosykh Maxim M. Perfilov Alexandra L. Rippa Elena V. Alpeeva Andrey V. Vasiliev Ekaterina A. Vorotelyak Nadya G. Gurskaya 《International journal of molecular sciences》2021,22(8)
The recessive form of dystrophic epidermolysis bullosa (RDEB) is a crippling disease caused by impairments in the junctions of the dermis and the basement membrane of the epidermis. Using ectopic expression of hTERT/hTERT + BMI-1 in primary cells, we developed expansible cultures of RDEB fibroblasts and keratinocytes. We showed that they display the properties of their founders, including morphology, contraction ability and expression of the respective specific markers including reduced secretion of type VII collagen (C7). The immortalized keratinocytes retained normal stratification in 3D skin equivalents. The comparison of secreted protein patterns from immortalized RDEB and healthy keratinocytes revealed the differences in the contents of the extracellular matrix that were earlier observed specifically for RDEB. We demonstrated the possibility to reverse the genotype of immortalized cells to the state closer to the progenitors by the Cre-dependent hTERT switch off. Increased β-galactosidase activity and reduced proliferation of fibroblasts were shown after splitting out of transgenes. We anticipate our cell lines to be tractable models for studying RDEB from the level of single-cell changes to the evaluation of 3D skin equivalents. Our approach permits the creation of standardized and expandable models of RDEB that can be compared with the models based on primary cell cultures. 相似文献
8.
改进的模糊交叉算子及其在CGA中的应用 总被引:2,自引:0,他引:2
基于标准化适应值信息,提出改进的模糊交叉算子,并应用到细胞状遗传算法(CGA)中。在具有局部搜索倾向的交叉操作中,该算子能使后代更偏向于适应值高的父体。在具有全局搜索倾向的交叉操作中,能使较差个体在更大范围内进行搜索,有效地引导CGA算法向全局最优解的方向收敛。仿真实验结果表明,基于改进模糊交叉算子的CGA算法性能更好。 相似文献
9.
10.
本文通过牛视紫质蛋白质晶体结构使用Composer模建程序进行了人类μ阿片受体的同源模建,预测了μ阿片受体的二级结构,用Ramachandran图和ProTable验证模型的可靠性.得到的模型91%的氨基酸残基位丁最佳区域,7个疏水区域表明有7个跨膜区与模型一致.并使用Surflex-Dock程序进行一系列芬太尼类似物分子与μ阿片受体的对接研究进而研究了其作用机制.活性位点主要包括ILE109,ASP112,TYR113,MET116,HIS262,TYR291.这些氨基酸残基都是芬太尼类似物与μ阿片受体的相互作用的主要残基.对接打分较高的分了均为与活性位点结合较好的分子,由此可对μ阿片受体有更深入的了解从而为设计出活性更高的芬太尼类化合物提供依据. 相似文献