全文获取类型
收费全文 | 7121篇 |
免费 | 436篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 167篇 |
综合类 | 65篇 |
化学工业 | 1844篇 |
金属工艺 | 211篇 |
机械仪表 | 198篇 |
建筑科学 | 208篇 |
矿业工程 | 31篇 |
能源动力 | 302篇 |
轻工业 | 1173篇 |
水利工程 | 78篇 |
石油天然气 | 49篇 |
无线电 | 520篇 |
一般工业技术 | 1082篇 |
冶金工业 | 792篇 |
原子能技术 | 55篇 |
自动化技术 | 819篇 |
出版年
2024年 | 27篇 |
2023年 | 83篇 |
2022年 | 211篇 |
2021年 | 357篇 |
2020年 | 269篇 |
2019年 | 273篇 |
2018年 | 302篇 |
2017年 | 305篇 |
2016年 | 303篇 |
2015年 | 207篇 |
2014年 | 280篇 |
2013年 | 514篇 |
2012年 | 403篇 |
2011年 | 456篇 |
2010年 | 344篇 |
2009年 | 338篇 |
2008年 | 312篇 |
2007年 | 220篇 |
2006年 | 211篇 |
2005年 | 152篇 |
2004年 | 148篇 |
2003年 | 215篇 |
2002年 | 212篇 |
2001年 | 169篇 |
2000年 | 109篇 |
1999年 | 90篇 |
1998年 | 218篇 |
1997年 | 171篇 |
1996年 | 119篇 |
1995年 | 85篇 |
1994年 | 62篇 |
1993年 | 70篇 |
1992年 | 35篇 |
1991年 | 33篇 |
1990年 | 32篇 |
1989年 | 31篇 |
1988年 | 29篇 |
1987年 | 18篇 |
1986年 | 23篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 14篇 |
1976年 | 24篇 |
1973年 | 5篇 |
排序方式: 共有7594条查询结果,搜索用时 31 毫秒
1.
2.
3.
讨论了在VMI管理思想下对具有随机需求特性的多客户库存分配问题 ,重点论述了有效近似算法的设计过程 ,最后基于一组模拟数据给出了一个算例。 相似文献
4.
Piedade M. Sousa L. A. de Almeida T. M. Germano J. da Costa B. A. Lemos J. M. Freitas P. P. Ferreira H. A. Cardoso F. A. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(11):2384-2395
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays 相似文献
5.
6.
Marcia Cristina Kaezer Fran a Rosane Aguiar da Silva San Gil Jean-Guillaume Eon 《Catalysis Today》2003,78(1-4):105-115
γ-Al2O3 supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW5O195−, V2W4O194−, VMo5O195− and V2Mo4O194−) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and 51V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state 51V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VOx/γ-Al2O3 was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al2O3 surface. 相似文献
7.
The Woodman Point Wastewater Treatment Plant (WWTP) in Western Australia has experienced two separate problems causing avoidable maintenance costs: the build-up of massive struvite (MgNH4PO4. 6H2O) scaling downstream of the anaerobic digester and the formation of hydrogen sulfide (H2S) levels in the digester gas to levels that compromised gas engine operation and caused high operating costs on the gas scrubber. As both problems hang together with a chemical imbalance in the anaerobic digester, we decided to investigate whether both problems could be (feasibly and economically) addressed by a common solution (such as dosing of iron solutions to precipitate both sulfide and phosphate), or by using separate approaches. Laboratory results showed that, the hydrogen sulfide emission in digesters could be effectively and economically controlled by the addition of iron dosing. Slightly higher than the theoretical value of 1.5 mol of FeCl3 was required to precipitate 1 mol of dissolved sulfide inside the digester. Due to the high concentration of PO4(3-) in the digested sludge liquor, significantly higher iron is required for struvite precipitation. Iron dosing did not appear an economic solution for struvite control via iron phosphate formation. By taking advantage of the natural tendency of struvite formation in the digester liquid, it is possible to reduce the risk of struvite precipitation in and around the sludge-dewatering centrifuge by increasing the pH to precipitate struvite out before passing through the centrifuge. However, as the Mg2+/PO4(3-) molar ratio in digested sludge was low, by increasing the pH alone (using NaOH) the precipitation of PO4(3-) was limited by the amount of cations (Ca2+ and Mg2+) available in the sludge. Although this would reduce struvite precipitation in the centrifuge, it could not significantly reduce PO4(3-) recycling back to the plant. For long-term operation, maximum PO4(3-) reduction should be the ultimate aim to minimise PO4(3-) accumulation in the plant. Magnesium hydroxide liquid (MHL) was found to be the most cost-effective chemical to achieve this goal. It enhanced struvite precipitation from both, digested sludge and centrate to the point where more than 95% PO4(3-) reduction in the digested sludge was achieved. 相似文献
8.
9.
10.
Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献