全文获取类型
收费全文 | 127607篇 |
免费 | 13432篇 |
国内免费 | 6608篇 |
专业分类
电工技术 | 8815篇 |
技术理论 | 7篇 |
综合类 | 9964篇 |
化学工业 | 19939篇 |
金属工艺 | 7521篇 |
机械仪表 | 8709篇 |
建筑科学 | 10463篇 |
矿业工程 | 4006篇 |
能源动力 | 3433篇 |
轻工业 | 10278篇 |
水利工程 | 2724篇 |
石油天然气 | 6394篇 |
武器工业 | 1269篇 |
无线电 | 15017篇 |
一般工业技术 | 13760篇 |
冶金工业 | 5283篇 |
原子能技术 | 1591篇 |
自动化技术 | 18474篇 |
出版年
2024年 | 1296篇 |
2023年 | 1989篇 |
2022年 | 3899篇 |
2021年 | 5168篇 |
2020年 | 3977篇 |
2019年 | 3175篇 |
2018年 | 3602篇 |
2017年 | 4060篇 |
2016年 | 3786篇 |
2015年 | 5519篇 |
2014年 | 6685篇 |
2013年 | 8025篇 |
2012年 | 9108篇 |
2011年 | 9785篇 |
2010年 | 8932篇 |
2009年 | 8811篇 |
2008年 | 8584篇 |
2007年 | 8165篇 |
2006年 | 7572篇 |
2005年 | 6482篇 |
2004年 | 4381篇 |
2003年 | 3563篇 |
2002年 | 3369篇 |
2001年 | 2905篇 |
2000年 | 2534篇 |
1999年 | 2504篇 |
1998年 | 1797篇 |
1997年 | 1555篇 |
1996年 | 1361篇 |
1995年 | 1146篇 |
1994年 | 886篇 |
1993年 | 655篇 |
1992年 | 535篇 |
1991年 | 412篇 |
1990年 | 316篇 |
1989年 | 281篇 |
1988年 | 223篇 |
1987年 | 133篇 |
1986年 | 129篇 |
1985年 | 61篇 |
1984年 | 55篇 |
1983年 | 26篇 |
1982年 | 36篇 |
1981年 | 30篇 |
1980年 | 38篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1976年 | 14篇 |
1975年 | 7篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Heat‐curable silicone rubber (HCSR) was prepared by using vinyl‐containing silicone resin (VSR) as the crosslinking agent instead of polyvinylsilicone oil (C gum). Mechanical properties and crosslink density of the vulcanizates were measured. The results indicate that VSR is a good crosslinking agent for HCSR. The tensile strength, tearing strength, elongation at break, and hardness of the vulcanizate can reach 10.2 MPa, 29.1 kN/m, 720%, and 58 SHA, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3123–3127, 2002; DOI 10.1002/app.10054 相似文献
62.
Poly(ethylene terephthalate) (PET) was blended with two different poly(oxybenzoate‐p‐trimethylene terephthalate) copolymers, designated T28 and T64, with the level of copolymer varying from 1 to 15 wt %. All samples were prepared by solution blending in a 60/40 (by weight) phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of the samples was studied by DSC. The results indicate that both T28 and T64 accelerated the crystallization rate of PET in a manner similar to that of a nucleating agent. The acceleration of PET crystallization rate was most pronounced in the PET/T64 blends with a maximum level at 5 wt % of T64. The melting temperatures for the blends are comparable to that of pure PET. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolymer in the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1599–1606, 2002 相似文献
63.
Yuxin Yin Zhengguo Jin Feng Hou Xu Wang 《Journal of the American Ceramic Society》2007,90(8):2384-2389
Titanium dioxide (TiO2 ) nanotube arrays were prepared by electrochemical anodization of titanium sheets in the glycerol 176 mL/H2 O 44 mL/NH4 F 0.5 wt% electrolytes modified with H2 SO4 and NaAc addition. The surface morphologies, average inner diameter, and the length of the nanotube arrays changed with the solution pH in the range from 5.6 to 4.0 by adding H2 SO4 . A uniform surface morphology of the nanotubes with average inner diameter of ∼80 nm and a length of ∼1000 nm was obtained when the solution pH was 5.0. The growth rates of the nanotubes were remarkably enhanced by NaAc addition in the range of 0.04–0.14 M . With NaAc addition of 0.10 M , the length of the nanotube arrays reached 4.16 μm after an 8-h anodization, increasing 3.23 μm compared with no NaAc addition. The relationship between solution pH and growth of TiO2 nanotubes was analyzed by current–time curves, solution electrical conductivities, and scanning electron microscopy (SEM), and the role of NaAc was also discussed based on SEM and solution electrical conductivities. 相似文献
64.
A novel and simple growth mark method was developed to make marks during the growth process of carbon nanotube arrays. These marks can be read out under scanning electron microscope or optical microscope. Based on this method, the growth rates at different temperatures and under different acetylene partial pressures were measured, from which the activation energy and the order of reaction were determined. Based on our experimental results, the growth of carbon nanotube arrays in our experimental condition could not be diffusion-limited. The measured activation energy could possibly be attributed to the heterogeneous decomposition of acetylene over the catalyst particle. Furthermore the marked array with special segmental structure may be found some applications in the future. 相似文献
65.
The structure of benzoxazines is similar to that of phenolic resin through thermal self‐curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn–Wall–Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn–Wall–Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 730–737, 2005 相似文献
66.
Dissolved oxygen in the steel at the terminal of the converter smelting process is the main cause for the formation of oxide inclusions, and the high terminal oxygen content worsens the steel cleanness. However, post stirring in a combined blowing converter can promote the carbon-oxygen reaction in the liquid steel and reduce the dissolved oxygen content at the terminal of the converter smelting process. Thus, the mathematical model of deoxidization in the post stirring process was obtained, and the rationa... 相似文献
67.
本文针对地铁车厢内控制设备分散的问题,设计了基于TCNRTP的地铁列车控制网络系统。采用NS2网络模拟软件构建的虚拟网络环境,编写消息数据传输层协议,通过测试列控网络的通信效率,得出了影响通信效率的因素;通过配置列控通信设备的基本功能和设定装置运行参数达到配置网络化通信的目的。 相似文献
68.
建设鄱阳湖生态经济区是国家从战略全局和长远发展出发作出的一项重大决策。如何主动策应鄱阳湖生态经济区建设,推动吉安进位赶超、跨越发展,是摆在我们各级政府和科技部门面前一项亟待解决的问题。为此,一是要提高认识,统一思想,切实增强策应规划的使命感和责任感;二是要结合实际,突出重点,全面对接鄱阳湖生态经济区规划;三是要加强领导,落实措施,确保吉安进位赶超、绿色崛起取得明显成效。 相似文献
69.
Jianfeng Wu Jian Li Xiaohong Xu Lanfang Yang Jufang Wu Fang Zhao Chuanguo Li 《武汉理工大学学报(材料科学英文版)》2009,24(4):651-653
A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding
SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results
indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs
between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage
density and high thermal conductivity, it is suit for energy storage under high temperature.
Funded by the “863” Hi-Tech Research and Development Program of China (2008AA05Z418) 相似文献
70.
建设工程涉外设计合同风险防范 总被引:2,自引:0,他引:2
中国参加WTO后,在扩大对外开放、拉动内需保增长政策指导下,一大批重点建设工程陆续上马,有许多外国设计企业及其在华机构加入中国建设工程的设计,其中,国有独资项目占据很大的比重。笔者结合参与全国十运会场馆一南京奥体中心以及江苏省人民医院扩建、南京图书管等多个大型项目工程全程法律保障实践,就工程设计合同风险防范,一舒管见。 相似文献