全文获取类型
收费全文 | 7009篇 |
免费 | 877篇 |
国内免费 | 308篇 |
专业分类
电工技术 | 653篇 |
综合类 | 434篇 |
化学工业 | 578篇 |
金属工艺 | 164篇 |
机械仪表 | 318篇 |
建筑科学 | 397篇 |
矿业工程 | 158篇 |
能源动力 | 215篇 |
轻工业 | 203篇 |
水利工程 | 68篇 |
石油天然气 | 84篇 |
武器工业 | 43篇 |
无线电 | 2088篇 |
一般工业技术 | 1470篇 |
冶金工业 | 216篇 |
原子能技术 | 83篇 |
自动化技术 | 1022篇 |
出版年
2024年 | 32篇 |
2023年 | 178篇 |
2022年 | 107篇 |
2021年 | 213篇 |
2020年 | 275篇 |
2019年 | 222篇 |
2018年 | 209篇 |
2017年 | 279篇 |
2016年 | 281篇 |
2015年 | 274篇 |
2014年 | 438篇 |
2013年 | 450篇 |
2012年 | 461篇 |
2011年 | 486篇 |
2010年 | 381篇 |
2009年 | 400篇 |
2008年 | 397篇 |
2007年 | 416篇 |
2006年 | 361篇 |
2005年 | 287篇 |
2004年 | 263篇 |
2003年 | 248篇 |
2002年 | 212篇 |
2001年 | 207篇 |
2000年 | 171篇 |
1999年 | 139篇 |
1998年 | 118篇 |
1997年 | 61篇 |
1996年 | 81篇 |
1995年 | 65篇 |
1994年 | 75篇 |
1993年 | 48篇 |
1992年 | 51篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 37篇 |
1983年 | 37篇 |
1982年 | 26篇 |
1981年 | 6篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1964年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有8194条查询结果,搜索用时 8 毫秒
51.
52.
采用系统分析、数学及物理计算的方法,对火电厂仪用压缩空气带水带油的原因进行论证,找出最主要原因,并有针对性地采取了预防和改造措施,对改造效果进行了分析与总结。 相似文献
53.
朱少红 《南京工业职业技术学院学报》2010,10(1):62-64
在汉语词汇学界,同义词一直是汉语词汇学研究争论的焦点,对同义词的研究也极为详尽和全面,但在对外汉语教学领域中的同义词教学还需要探索,本文从对外汉语教学角度出发,提出了对外汉语同义语汇的概念,它比汉语学界的同义词要宽泛,并探讨了它的收词范围和辨析方法。 相似文献
54.
龙凌 《湖南工业职业技术学院学报》2010,10(6):33-36
文章以长株潭城市群"两型社会"为目标引领,以城乡统筹理论为实践指导,系统分析了长株潭城市群郊野山区发展旅游休闲的可行性与必要性。在此基础上,以金龙天池民族生态乐园旅游开发为实际案例,详细探讨了长株潭城市群郊野山区旅游休闲开发应遵循的原则与应注意的问题。 相似文献
55.
56.
Richard H. Harris Vicki J. Boyd Graham J. Hutchings Stuart H. Taylor 《Catalysis Letters》2002,78(1-4):369-372
The effect of water addition on the complete oxidation of benzene and propane VOCs by uranium oxide catalysts has been investigated. Benzene oxidation was studied using a silica supported U3O8 catalyst. Complete oxidation is promoted by the addition of 2.6% water compared with the reactivity when no water is added to the reactant feed. Increasing the water concentration to 12.1% resulted in a suppression of oxidation activity. Investigation of propane oxidation using U3O8 shows a dramatic promotion of activity. Propane conversion was ca. 50% at 600 °C without added water, whilst it increased to 100% at 400 °C with the addition of 2.6% water. A comparison of oxidation activity has been made with Mn2O3, an oxide recognised for complete oxidation. In contrast to the U3O8 catalysts the addition of 2.6% water suppresses the activity of Mn2O3. In situ powder X-ray diffraction studies showed that the bulk U3O8 structure was stable under all the reaction conditions. The origin of the increased activity is not clear but may be due to modification of the catalyst surface and the contribution from new reaction pathways such as steam reforming. 相似文献
57.
Auguste Fernandes Maria Filipa Ribeiro Cristina Borges Joo Paulo Loureno Joo Rocha Zelimir Gabelica 《Microporous and mesoporous materials》2006,90(1-3):112-128
This study is aimed at exploring the ability of very small sized N-bearing molecules to generate and stabilize microporous aluminophosphates. Two new AlPO4-n materials, called IST-1 and IST-2, have been obtained in aqueous media using, as main template, methylamine (MA), directly added, or generated in situ from methylformamide (MF) degradation. While IST-1 topology proved to be novel, IST-2 appears structurally related to AlPO4-53(A). The obtained materials were characterized by powder XRD, TG/DSC, SEM and solid-state NMR. Tetraalkylammonium (TEA) cations were used as potential co-templates but only MA and water were found incorporated in the pore volumes of both structures, which argues for their true templating role. In IST-1, 13C solid-state NMR studies showed that half of MA species, presumably protonated, is H-bonded to framework oxygens while the other half surprisingly bonds directly to framework Al atoms. 13C NMR showed that only protonated MA occurs in IST-2 channels. TEA+ cations definitely do not play any specific template role. They indirectly favor the crystallization of IST-1 or IST-2 devoid from other crystalline or amorphous side phases, by interacting with part of the Al and P in solution and forming soluble [AlPO4(OH)]–[TEA,HMA] complexes, substantially modifying the compositions of gels precursors to each phase during nucleation and/or growth steps. While both IST-1 and IST-2 crystallize from gels of similar initial compositions, it was demonstrated that the new MA/T ratio (T = Al or P) obtained after in situ complexation was the key parameter that specifically governs the crystallization of each phase. 相似文献
58.
Recently, it has been reported by our group and others1.2 that loss of curing agent is encountered during the curing of small droplets or thin films of amine cured epoxies. In our earlier study3 results were reported on loss of curing agent in small droplets used in conducting the rnicrobond, single fiber test for determination of interfacial shear strength (ISS). It was reported that use of a volatile curing agent (meta-phenylene diamine (m-PDA) with DGEBA resin) resulted in increasing amounts of curing agent being lost (as measured by T8 of the cured droplets) with decreasing droplet size during the processing procedure. Droplets smaller than 150 micrometers were seen to lose up to 40% of the curing agent leading to alteration of the mechanical properties of the droplet and, therefore, causing measured values of ISS to be exceedingly low. Use of a less volatile curing agent (Jeffamine 700, a polyether diamine, Texaco Specialty Chemicals) in combination with DGEBA resin produced results which indicated that loss of curing agent was not occuring. This study was undertaken to show the relationships between film (or droplet) size and the amount of curing agent lost (during the processing) for three different aminecured epoxy systems. 相似文献
59.
Digital transformation (DT), the combination of information, computing, communication and connectivity technologies, which has triggered an effective upgrade of different aspects of market strategy, customer experience etc. Nowadays, rehabilitation assistive devices (RADs) are evolving to be more digital, intelligent and personalized. Digitalization and servitization have fostered to an emerging business model—the smart product–service system (Smart PSS). Therefore, DT of the RADs’ industry advocates not only the design of products and functions, the more important is the management of service processes and resource integration. With the increase in the elderly and disabled population, the requirement for RADs is becoming more urgent. However, research on Smart PSS for RAD is still limited. The rehabilitation assistive smart product–service systems (RASPSS) was introduced into the development of RADs based on the “Design and Management of DT” strategy through the service design of assistive devices and user requirements analysis. Further, an integrated design of RAD and Smart PSS has been created, a development method of RASPSS proposed, the theoretical model of the Smart PSS based on RADs built. To specify the service framework, this case study discusses the development of a home rehabilitation assistive system for femoral stem fracture patients. This paper evaluates the usability of the system, the results of which prove usability and effectiveness of the RASPSS development method. The RASPSS development model is designed to meet needs of stakeholders, improve the user rehabilitation experience, promote the service innovation of Smart PSS, bring certain market benefits of rehabilitation aids and create social value. 相似文献
60.
The synthesis of homogeneous and pure silica–alumina binary glasses doped with rare-earth (RE) ions such as Er3+ is currently a key challenge for the development of integrated optics devices such as lasers, optical amplifiers or waveguides. In this study Er3+-doped SiO2–Al2O3 films were prepared by the sol–gel route. Aluminium sec-butoxide, Al(O-sec-C4H9)3 (ASB), and tetraethoxysilane, Si(OC2H5)4 (TEOS), were used as glass oxide precursors, whereas erbium was introduced as Er(NO3)3. The alumina content in the silica matrix was 10 at.%, while erbium doping ranged between 200 and 5000 ppm. The preparation of the starting sol–gel solution and the layer deposition by a dip-coating procedure were performed in dry-box under nitrogen atmosphere. The obtained films were subsequently annealed in air between 300 and 1000 °C. After treatment at 500 °C, layers 200 nm thick were obtained. The composition, microstructure and surface morphology of the films were investigated by X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Crack-free, transparent, high purity films were obtained, characterised by compositional and microstructural homogeneity. 相似文献