全文获取类型
收费全文 | 355281篇 |
免费 | 4037篇 |
国内免费 | 1234篇 |
专业分类
电工技术 | 6991篇 |
综合类 | 217篇 |
化学工业 | 51708篇 |
金属工艺 | 14462篇 |
机械仪表 | 9935篇 |
建筑科学 | 8036篇 |
矿业工程 | 1578篇 |
能源动力 | 8875篇 |
轻工业 | 28985篇 |
水利工程 | 3222篇 |
石油天然气 | 5586篇 |
武器工业 | 9篇 |
无线电 | 44349篇 |
一般工业技术 | 66758篇 |
冶金工业 | 75124篇 |
原子能技术 | 7331篇 |
自动化技术 | 27386篇 |
出版年
2021年 | 2413篇 |
2019年 | 2377篇 |
2018年 | 3942篇 |
2017年 | 3968篇 |
2016年 | 4122篇 |
2015年 | 2912篇 |
2014年 | 5001篇 |
2013年 | 14929篇 |
2012年 | 8493篇 |
2011年 | 11699篇 |
2010年 | 9420篇 |
2009年 | 10997篇 |
2008年 | 11310篇 |
2007年 | 11335篇 |
2006年 | 10008篇 |
2005年 | 9417篇 |
2004年 | 9150篇 |
2003年 | 8741篇 |
2002年 | 8521篇 |
2001年 | 8905篇 |
2000年 | 8357篇 |
1999年 | 8994篇 |
1998年 | 24722篇 |
1997年 | 16859篇 |
1996年 | 12964篇 |
1995年 | 9578篇 |
1994年 | 8206篇 |
1993年 | 8185篇 |
1992年 | 5661篇 |
1991年 | 5484篇 |
1990年 | 5354篇 |
1989年 | 5205篇 |
1988年 | 4889篇 |
1987年 | 4143篇 |
1986年 | 4161篇 |
1985年 | 4741篇 |
1984年 | 4281篇 |
1983年 | 3882篇 |
1982年 | 3622篇 |
1981年 | 3796篇 |
1980年 | 3393篇 |
1979年 | 3339篇 |
1978年 | 3282篇 |
1977年 | 3946篇 |
1976年 | 5182篇 |
1975年 | 2854篇 |
1974年 | 2780篇 |
1973年 | 2789篇 |
1972年 | 2355篇 |
1971年 | 2126篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
S H Yoon J H Collins D Musale S Sundararajan S P Tsai G A Hallsby J F Kong J Koppes P Cachia 《Water science and technology》2005,51(6-7):151-157
A newly developed membrane performance enhancer (MPE) was used to prevent membrane fouling in a membrane bioreactor (MBR) process. It transpired that 1,000 mg/l of MPE reduced polysaccharide levels from 41 mg/I to 21 mg/I on average under the experimental condition. Repeated experiments also confirmed that 50-1,000 mg/l of MPE could reduce membrane fouling significantly and increase the intervals between membrane cleanings. Depending on MPE dosages and experimental conditions, trans-membrane pressure (TMP) increase was suppressed for 20-30 days, while baseline TMP surged within a few days. In addition, MPE allowed MBR operation even at 50,000 mg/l of total solid and reduced permeate COD. However, no evidence of toxicity for sludge was found from respiratory works. 相似文献
104.
This work investigates the impact of nine new product development (NPD) acceleration approaches (supplier involvement, lead user involvement, speeding up activities and tasks, reduction of parts and components, training and rewarding of employees, implementation of support systems and techniques, stimulating interfunctional cooperation, emphasis on the customer, and simplification of organizational structure) on development speed and new product profitability. Our findings from 233 manufacturing firms show that lead user involvement and training/rewarding of employees increase both development speed and profitability. Supplier involvement, speeding up activities and tasks, and a simplification of the organizational structure also enhance development speed, while an emphasis on the customer has an additional positive impact on new product profitability. Both new product speed and profitability increase firm financial performance. Our results further show that pioneers and fast followers should not select the same NPD acceleration approaches as the speed and profitability impact of the majority of the acceleration approaches depends on the new product strategy of the firm. These results are important as they provide guidance for pioneers and fast followers regarding which NPD acceleration approaches to select in order to enhance speed and profitability and, hence, firm financial performance. 相似文献
105.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献
106.
107.
The electrochemical faceting of polycrystalline (pc) platinum yielding a (100)-preferred oriented electrode surface was accomplished in HF solutions by applying to the pc platinum electrode a square wave potential perturbation at 1 kHz in the 0.2 to 1.3 V range (vs rhe). SEM patterns of the resulting surfaces were also obtained. For HF concentrations up to 2 M no appreciable influence of the electrolyte concentration on the electrochemical faceting was noticed. Otherwise, the voltammetric response of the (100)-type preferred oriented platinum surface in the H-adatom potential range when compared to previously reported data resulted remarkably sensitive to the electrolyte composition. The discussion of results was based on the non-equilibrium adsorption conditions for anions under the periodic perturbation. 相似文献
108.
109.
Svetlana A. Yashnik Zinfer R. Ismagilov Vladimir F. Anufrienko 《Catalysis Today》2005,110(3-4):310-322
The effect of ion exchange conditions, such as Si/Al ratio, precursor copper salt, pH and concentration of the solution, on the catalytic activity in SCR of NO by propane and on the electronic state of copper ions in Cu-ZSM-5 has been studied. The NO conversion in NO SCR by C3H8 has been found to reach a maximum value at Cu/Al ratio about 0.37–0.4 and remain constant at higher Cu/Al.
ESR and UV–vis DR spectroscopy have been used to elucidate stabilization conditions of copper ions in Cu-ZSM-5 zeolites as isolated Cu2+ ions, chain copper oxide structures and square-plain oxide clusters. The ability of copper ions for reduction and reoxidation in the chain structures may be responsible for the catalytic activity of Cu-ZSM-5. These transformations of copper ions are accompanied by the observation of intervalence transitions Cu2+–Cu+ and CTLM of the chain structures in the UV–vis spectra. 相似文献
110.
Amanda Alliband Daniel W. Lenz Laura E. Stevenson Travis Whitmer Rex Cash Dennis Burns Sarah Hall William T.K. Stevenson 《Progress in Organic Coatings》2008
A model has been proposed to explain the failure of the original BMS10-39 epoxy paint on upper vertical surfaces in B-52 fuel tanks. The model involves interaction of the paint with DIEGME, a fuel system ice inhibitor (FSII) in jet fuel, that is distilled from the liquid fuel. In this communication, distillation experiments used to support the model are refined to better match the mass transfer of vapor from fuel in a B-52 fuel tank at close to room temperature. The interaction of these lower temperature distillates with the paint affirms the earlier model. On the basis of these experiments it is proposed that paint failure may be controlled or eliminated by reducing the level of DIEGME in the fuel. Proposed changes in military jet fuel composition are detailed. 相似文献