全文获取类型
收费全文 | 4537篇 |
免费 | 426篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 118篇 |
综合类 | 85篇 |
化学工业 | 959篇 |
金属工艺 | 138篇 |
机械仪表 | 123篇 |
建筑科学 | 165篇 |
矿业工程 | 40篇 |
能源动力 | 254篇 |
轻工业 | 541篇 |
水利工程 | 57篇 |
石油天然气 | 34篇 |
武器工业 | 15篇 |
无线电 | 481篇 |
一般工业技术 | 853篇 |
冶金工业 | 430篇 |
原子能技术 | 39篇 |
自动化技术 | 701篇 |
出版年
2024年 | 13篇 |
2023年 | 87篇 |
2022年 | 158篇 |
2021年 | 268篇 |
2020年 | 180篇 |
2019年 | 168篇 |
2018年 | 235篇 |
2017年 | 244篇 |
2016年 | 205篇 |
2015年 | 178篇 |
2014年 | 236篇 |
2013年 | 364篇 |
2012年 | 285篇 |
2011年 | 336篇 |
2010年 | 205篇 |
2009年 | 195篇 |
2008年 | 166篇 |
2007年 | 154篇 |
2006年 | 147篇 |
2005年 | 98篇 |
2004年 | 106篇 |
2003年 | 89篇 |
2002年 | 61篇 |
2001年 | 50篇 |
2000年 | 49篇 |
1999年 | 61篇 |
1998年 | 103篇 |
1997年 | 79篇 |
1996年 | 61篇 |
1995年 | 54篇 |
1994年 | 39篇 |
1993年 | 38篇 |
1992年 | 34篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 13篇 |
1988年 | 19篇 |
1987年 | 23篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1973年 | 8篇 |
1970年 | 7篇 |
排序方式: 共有5033条查询结果,搜索用时 140 毫秒
1.
Kalli Sai Bhavani Tummala Anusha Pradeep Kumar Brahman 《International Journal of Hydrogen Energy》2021,46(13):9199-9214
In the present study, we report an eco-friendly and simple route to design and synthesize novel nanocomposite catalyst based on platinum nanoparticles anchored on binary support of graphitic carbon nitride (g-C3N4) and cobalt-metal-organic framework (ZIF-67). For this purpose, ZIF-67 was prepared by precipitation method and g-C3N4 was prepared through thermal polymerization method. Later, ZIF-67 and g-C3N4 were hybridized through sonication to get homogeneous g–C3N4–ZIF-67 nanocomposite support material. Platinum nanoparticles (PtNPs) were uniformly deposited on g–C3N4–ZIF-67 by an electrochemical method. The as-developed nanocatalyst was characterized by morphological, structural and electrochemical techniques. The electrocatalytic activity of PtNPs@g–C3N4–ZIF-67 nanocatalyst towards butanol oxidation was evaluated via CV, CA, LSV and EIS in an alkaline medium. Results revealed that the proposed catalyst showed greatly enhanced electrooxidation of butanol in terms of high magnificent current density, lower oxidation potential, excellent long-term stability, large surface area, low charge transfer resistance and less toxic ability. Enhanced catalytic performance of the proposed catalyst could be ascribed to the synergistic effect of g–C3N4–ZIF-67 nanocomposite and PtNPs. The PtNPs@g–C3N4–ZIF-67 catalyst holds promising potential applications to be used as an anodic electrocatalyst for the development of high-performance alkaline fuel cells. 相似文献
2.
3.
4.
5.
Tek Bahadur Gurung Ram Prasad Dhakal Jay Dev Bista 《Lakes & Reservoirs: Research and Management》2006,11(3):141-148
The seasonal patterns of phytoplankton primary production, chlorophyll‐a concentration, cell number and several other limnological variables in Lake Phewa, located in the active monsoon zone in Central Himalaya, Nepal, were studied for a year beginning in April 2001. During the study period, the gross primary production and chlorophyll‐a concentrations were relatively low during the monsoon season. The phytoplankton cell number, represented by 24 genera, also fluctuated seasonally, but tended to increase in the pre‐ and post‐monsoon period. These results suggest that the monsoon plays a crucial role in the primary production and phytoplankton dynamics for Lake Phewa. Among the phytoplankton species, Microcystis aeruginosa, a representative species for eutrophic lakes, was the dominant phytoplankton. At the same time, however, it is clear that the lake is not yet heavily eutrophic. The present study suggests that the exchange of lake water during the monsoon season contributes to maintaining the health of the lake against further degradation. Nevertheless, the silt carried in the monsoon rain run‐off from the lake's catchment area suggests increasingly serious degradation problems for this small mountainous lake. 相似文献
6.
K.P. Pipe R.J. Ram 《Photonics Technology Letters, IEEE》2003,15(4):504-506
By measuring the total energy flow from an optical device, we can develop new design strategies for thermal stabilization. Here we present a comprehensive model for heat exchange between a semiconductor laser diode and its environment that includes the mechanisms of conduction, convection, and radiation. We perform quantitative measurements of these processes for several devices, deriving parameters such as a laser's heat transfer coefficient, and then demonstrate the feasibility of thermal probing for the nondestructive wafer-scale characterization of optical devices. 相似文献
7.
A comprehensive study of hazelnut oil composition with comparisons to other vegetable oils,particularly olive oil. 总被引:4,自引:0,他引:4
Benitez-Sánchez Pedro Luis León-Camacho Manuel Aparicio Ramón 《European Food Research and Technology》2003,218(1):13-19
Crude and refined hazelnut oils from different countries were characterised by major and minor compounds. Fatty acids, triacylglycerides, waxes, sterols, methyl-sterols, terpenic and aliphatic alcohols, tocopherols, tocotrienols and hydrocarbons were identified and quantified by gas chromatography and high-performance liquid chromatography. The levels of these chemical compounds in hazelnut oils together with the equivalent carbon numbers and triacylglyceride carbon numbers, were compared with the results of analyses of samples of other vegetable oils. The statistical procedure of cluster analysis was used to characterise hazelnut oils versus other edible oils. 相似文献
8.
9.
10.
The thermal decomposition products of pyridinium sulfate differ from those of pyridinium sulfate supported on zirconia which in turn differs from that of pyridine adsorbed on a sulfated zirconia. Unsupported pyridinium sulfate decomposes to produce pyridine and sulfuric acid, and these subsequently react to produce oxides of carbon and sulfur. Zirconia that is sulfated and then exposed to pyridine does not release detectable amount of pyridine during heating in an inert gas; rather the pyridine undergoes oxidation reduction reactions simultaneously to release CO2 and sulfur compounds. Pyridinium sulfate supported on zirconia decomposes upon heating to release pyridine and sulfuric acid, which reacts with the zirconia. The desorption of pyridine in one case and only CO2/SOx in the other case suggests that sulfated zirconia does not contain Brønsted acidity that can form pyridinium sulfate. 相似文献