全文获取类型
收费全文 | 63496篇 |
免费 | 4326篇 |
国内免费 | 2826篇 |
专业分类
电工技术 | 2397篇 |
技术理论 | 2篇 |
综合类 | 4635篇 |
化学工业 | 15679篇 |
金属工艺 | 3676篇 |
机械仪表 | 2906篇 |
建筑科学 | 6522篇 |
矿业工程 | 2620篇 |
能源动力 | 1898篇 |
轻工业 | 5461篇 |
水利工程 | 1020篇 |
石油天然气 | 3755篇 |
武器工业 | 884篇 |
无线电 | 2871篇 |
一般工业技术 | 8387篇 |
冶金工业 | 3448篇 |
原子能技术 | 625篇 |
自动化技术 | 3862篇 |
出版年
2024年 | 223篇 |
2023年 | 594篇 |
2022年 | 1395篇 |
2021年 | 1648篇 |
2020年 | 1647篇 |
2019年 | 1256篇 |
2018年 | 1262篇 |
2017年 | 1770篇 |
2016年 | 1802篇 |
2015年 | 1788篇 |
2014年 | 3066篇 |
2013年 | 3024篇 |
2012年 | 3899篇 |
2011年 | 4281篇 |
2010年 | 3296篇 |
2009年 | 3651篇 |
2008年 | 3134篇 |
2007年 | 4687篇 |
2006年 | 4323篇 |
2005年 | 4038篇 |
2004年 | 3346篇 |
2003年 | 3122篇 |
2002年 | 2623篇 |
2001年 | 2222篇 |
2000年 | 1859篇 |
1999年 | 1519篇 |
1998年 | 1153篇 |
1997年 | 872篇 |
1996年 | 742篇 |
1995年 | 634篇 |
1994年 | 524篇 |
1993年 | 364篇 |
1992年 | 235篇 |
1991年 | 166篇 |
1990年 | 132篇 |
1989年 | 122篇 |
1988年 | 70篇 |
1987年 | 39篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1959年 | 4篇 |
1956年 | 3篇 |
1955年 | 4篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Timothy Thomasma Kurt Hilbrecht 《International Journal of Flexible Manufacturing Systems》1991,3(3-4):231-250
Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models. 相似文献
2.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献
3.
4.
Qingzhao Yao Yuming Zhou Yanqing Sun Xiaoyun Ye 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(4):477-484
TiO2 hybrid molecular imprinted polymer (MIP) for ethofumesate using methacrylic acid (MAA) as the functional monomer and silane
coupling agent 3-(trimethoxysilyl) propylmethacrylate (KH570) as organic–inorganic connective bridge was synthesized via photo-excitation
method. Hydrogen bond was proved to act between MAA and ethofumesate for pre- and post-polymerization binding properties as
testified by UV spectrometric method. KH570 modified TiO2 nanoparticles were prepared via sonochemical reaction, which can accelerate hydrolysis, increase collision chance for the
reactive system and improve the dispersion of the nanoparticles. Scanning electron microscope (SEM), transmission electron
microscope (TEM), binding and the adsorption kinetics experiments as well as thermogravimetric analysis (TGA) were employed
for characterization. The results indicated that the hybrid MIP revealed a larger surface area and more ordered imprinting
cavities with improved thermal stability compared to organic-only MIP. Furthermore, faster adsorption kinetics and enhancive
adsorption capacity were achieved, which made it promising in chemical sensor applications. 相似文献
5.
钛容器的特点 总被引:2,自引:1,他引:1
黄嘉琥 《石油化工设备技术》1996,17(5):19-24
根据钛材的化学、物理、力学和工艺性能介绍了钛容器在设计、制造、检验和应用方面的特点。 相似文献
6.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献
7.
岩心PI值试验研究及应用 总被引:5,自引:0,他引:5
主要论述了在多功能采油化学用剂评价仪上进行的岩心PI值试验的步骤,现象及结论。重点考察了岩心PI值与渗透率、流量及注入截面面积的关系;平行管岩心复合PI值和其中单管岩心PI值的关系。 相似文献
8.
本文涉及玻璃钢猎扫雷艇艇体材料的优选、铺层设计和工艺等内容。试验确定了以1629间苯聚酯树脂为基体、以900g/m2无碱无捻粗纱短切毡(M)和810g/m2无碱无捻粗纱方格布(R)为增强体以及(M+R)为基本铺层设计单元的方案。试验表明,按上述材料和铺层制作的层板,性能达到Lerici和MHC-51艇壳层板的指标要求。 相似文献
9.
本文简要介绍了国外在开发超酸性气体过程中遇到的材料选择、腐蚀监测、水化物堵塞、超酸性气的处理和加工等问题所采取的措施和办法。 相似文献
10.
A novel approach to the derivation of Bažant’s size effect law is presented. Contrarily to the original Lagrangian derivation
which hinged on energetic consideration, a Newtonian approach based on local stress intensity factors is presented. Through
this approach, it is shown that Bažant’s size effect law is the first (and dominant) term in a series expansion for the nominal
stress. Furthermore, analytical expressions forB are derived for selected specimen geometries. 相似文献