全文获取类型
收费全文 | 26567篇 |
免费 | 2121篇 |
国内免费 | 638篇 |
专业分类
电工技术 | 404篇 |
综合类 | 2409篇 |
化学工业 | 12873篇 |
金属工艺 | 575篇 |
机械仪表 | 286篇 |
建筑科学 | 2755篇 |
矿业工程 | 783篇 |
能源动力 | 720篇 |
轻工业 | 2760篇 |
水利工程 | 894篇 |
石油天然气 | 1348篇 |
武器工业 | 77篇 |
无线电 | 334篇 |
一般工业技术 | 1437篇 |
冶金工业 | 1227篇 |
原子能技术 | 169篇 |
自动化技术 | 275篇 |
出版年
2024年 | 61篇 |
2023年 | 267篇 |
2022年 | 539篇 |
2021年 | 714篇 |
2020年 | 831篇 |
2019年 | 599篇 |
2018年 | 520篇 |
2017年 | 751篇 |
2016年 | 842篇 |
2015年 | 808篇 |
2014年 | 1490篇 |
2013年 | 1490篇 |
2012年 | 2106篇 |
2011年 | 2002篇 |
2010年 | 1560篇 |
2009年 | 1617篇 |
2008年 | 1318篇 |
2007年 | 1835篇 |
2006年 | 1736篇 |
2005年 | 1441篇 |
2004年 | 1180篇 |
2003年 | 1072篇 |
2002年 | 852篇 |
2001年 | 654篇 |
2000年 | 519篇 |
1999年 | 481篇 |
1998年 | 323篇 |
1997年 | 273篇 |
1996年 | 239篇 |
1995年 | 189篇 |
1994年 | 182篇 |
1993年 | 105篇 |
1992年 | 106篇 |
1991年 | 103篇 |
1990年 | 80篇 |
1989年 | 67篇 |
1988年 | 56篇 |
1987年 | 57篇 |
1986年 | 51篇 |
1985年 | 58篇 |
1984年 | 56篇 |
1983年 | 31篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1962年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(6):3550-3555
Electrocatalytic nitrogen reduction reaction (ENRR) offers a carbon-neutral process to fix nitrogen into ammonia, but its feasibility depends on the development of highly efficient electrocatalysts. Herein, we report that Fe ion grafted on MoO3 nanorods synthesized by an impregnation technique can efficiently enhance the electron harvesting ability and the selectivity of H+ during the NRR process in neutral electrolyte. In 0.1 M Na2SO4 solution, the electrocatalyst exhibited a remarkable NRR activity with an NH3 yield of 9.66 μg h?1 mg?1cat and a Faradaic efficiency (FE) of 13.1%, far outperforming the ungrafted MnO3. Density functional theory calculations revealed that the Fe sites are major activation centers along the alternating pathway. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(81):34387-34396
This work develops a novel magnetic photocatalysts ZnO/SrFe12O19 (ZS) synthesized with hydrothermal process. The introduction of SrFe12O19 not only enhances the photocatalytic behavior of ZnO towards Rhodamine B (RhB) decomposition, but also reinforces the recycling stability. Especially, ZS-5 composite exhibits the optimal photocatalytic performance, and the RhB decomposition reaches 99.5% after being exposed to simulative sunlight for 70 min, which is obviously superior to that of bare ZnO. Furthermore, the ZS-5 can be recovered from RhB solution by an extra magnet space and reused. After five recycles, the RhB removal efficiency can still be maintained over 90%. Such prominent photocatalytic property and stability of ZS-5 are associated with the greatly improved detachment efficiency of photoexcited carriers in a magnetic field. This study could provide a new-type recyclable photocatalyst that can effectively purify dye wastewater for convenient recovery. 相似文献
3.
Water contamination is a global challenge impacting both the environment and human health with significant economic and social costs. The growing scarcity of usable water resources requires effective treatment of wastewater. In this context, developing cheaper, safer and more efficient wastewater treatment technologies are the need of the hour. One promising approach that several studies have reported success has been the usage of nanomaterials in water and waste water management. The rapid progress of research in nanomaterial sciences has shown their growing potential; however, there has not been a great amount of information available on their implementation. This review focuses on developments in nanotechnology that hold strong potential for wastewater treatment. The review covers key techniques in nanomaterial‐based water treatments including adsorption, filtration and photocatalysis with recent examples showing how to improve their properties and efficiencies according to the need. 相似文献
4.
Nicolas Larché Benoit Emo Audrey Allion Elisabeth Johansson Dominique Thierry 《工业材料与腐蚀》2021,72(8):1338-1349
With lower alloying cost and higher mechanical properties, lean duplex stainless steels can be an alternative to the more commonly used austenitic stainless steels. However, these alloys are still not the preferred choice, probably due to a lack of field experience. A study was thus initiated in view of defining the limits of use of selected (lean) duplexes for urban wastewater treatment units. The present paper shows the localized corrosion performance of selected lean duplexes in chloride contaminated solutions. The results are compared with austenitic S30403 and S31603 and with the more standard duplexes S82441 and S32205. The effect of welding was also investigated. Exposures in field municipal wastewater plants were conducted for 1 year in low and high chloride content units. The results show that lean duplexes S32101 and S32202 can be used as alternatives to S30403 and S31603 in low chloride electrolytes. At 500 ppm of chloride content, duplex stainless steel S32304 showed better corrosion resistance than S30403 and S31603. For higher chloride contents (1000 ppm and above) the standard duplexes S82441 and S32205 shall be preferred. 相似文献
6.
7.
尕斯库勒油田E13油藏已经进入高含水时期,储采失衡加剧,综合含水率达到了80%以上,原油产量下降,经济效益变差。为了提高油藏原油采出程度、改善油藏开发效果,调研了国内外减氧空气驱的机理研究以及现场试验的资料,建立了以油藏真实孔渗饱数据为基础的一维条形地层机理模型,并选取该油藏Y12-27井组进行了减氧空气驱可行性验证。研究表明:纵向顶部减氧空气驱驱油效果优于水驱和氮气驱;驱替压力对原油采出程度影响不大;注水转注气可以提高原油采出程度;对于减氧空气驱,由于低温氧化反应的作用,氧气浓度对原油采出程度有一定影响,但比较微弱,其中,氧气浓度为10%时,驱替结束采出程度最高;尕斯库勒油田E13油藏属于注水开发“双高”油藏,适用于减氧空气驱;对于该油藏Y12-27井组,顶部减氧空气驱驱油效果好于水驱和氮气驱,建议氧气浓度超过10%时采取关井等措施。 相似文献
8.
Dushyant Kumar 《分离科学与技术》2020,55(15):2844-2854
ABSTRACT In this study, electrocoagulation (EC) was used to determine the optimum conditions on the basis of maximum chemical oxygen demand (COD) and color removal. At the optimum conditions chlorophenols (CPs), biological oxygen demand and total organic carbon (TOC) were determined. The biodegradability of wastewater was increased significantly with 63% COD, 98% color, 61% TOC and overall 65.51% reductions in CPs. Further, the electro-coagulated sludge was characterized by using different analytical techniques to assist the physicochemical and elemental phases, to find-out better management option, reusability for plant growth and safe disposal. Additionally, aluminum content (70.62%) was successfully recovered from sludge. 相似文献
9.
C. Doga Demirhan William W. Tso Joseph B. Powell Efstratios N. Pistikopoulos 《American Institute of Chemical Engineers》2019,65(7):e16498
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019 相似文献
10.
Chitosan (CHT) is a non-toxic and inexpensive compound obtained by deacetylation of chitin, the main component of the exoskeleton of arthropods as well as of the cell walls of many fungi. In agriculture CHT is used to control numerous diseases on various horticultural commodities but, although different mechanisms have been proposed, the exact mode of action of CHT is still unknown. In sycamore (Acer pseudoplatanus L.) cultured cells, CHT induces a set of defense/stress responses that includes production of H2O2 and nitric oxide (NO). We investigated the possible signaling role of these reactive molecules in some CHT-induced responses by means of inhibitors of production and/or scavengers. The results show that both reactive nitrogen and oxygen species are not only a mere symptom of stress conditions but are involved in the responses induced by CHT in sycamore cells. In particular, NO appears to be involved in a cell death form induced by CHT that shows apoptotic features like DNA fragmentation, increase in caspase-3-like activity and release of cytochrome c from the mitochondrion. On the contrary, reactive oxygen species (ROS) appear involved in a cell death form induced by CHT that does not show these apoptotic features but presents increase in lipid peroxidation. 相似文献