全文获取类型
收费全文 | 56910篇 |
免费 | 4994篇 |
国内免费 | 2851篇 |
专业分类
电工技术 | 3416篇 |
技术理论 | 5篇 |
综合类 | 4693篇 |
化学工业 | 9543篇 |
金属工艺 | 2854篇 |
机械仪表 | 3294篇 |
建筑科学 | 4592篇 |
矿业工程 | 1395篇 |
能源动力 | 1492篇 |
轻工业 | 6277篇 |
水利工程 | 1180篇 |
石油天然气 | 2642篇 |
武器工业 | 490篇 |
无线电 | 6162篇 |
一般工业技术 | 5996篇 |
冶金工业 | 2276篇 |
原子能技术 | 774篇 |
自动化技术 | 7674篇 |
出版年
2024年 | 266篇 |
2023年 | 933篇 |
2022年 | 1695篇 |
2021年 | 2258篇 |
2020年 | 1733篇 |
2019年 | 1381篇 |
2018年 | 1594篇 |
2017年 | 1777篇 |
2016年 | 1588篇 |
2015年 | 2281篇 |
2014年 | 2919篇 |
2013年 | 3492篇 |
2012年 | 3948篇 |
2011年 | 4345篇 |
2010年 | 3859篇 |
2009年 | 3783篇 |
2008年 | 3775篇 |
2007年 | 3451篇 |
2006年 | 3347篇 |
2005年 | 2923篇 |
2004年 | 2013篇 |
2003年 | 1499篇 |
2002年 | 1534篇 |
2001年 | 1277篇 |
2000年 | 1182篇 |
1999年 | 1132篇 |
1998年 | 895篇 |
1997年 | 749篇 |
1996年 | 653篇 |
1995年 | 563篇 |
1994年 | 425篇 |
1993年 | 311篇 |
1992年 | 265篇 |
1991年 | 203篇 |
1990年 | 142篇 |
1989年 | 131篇 |
1988年 | 111篇 |
1987年 | 57篇 |
1986年 | 74篇 |
1985年 | 29篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 22篇 |
1980年 | 27篇 |
1979年 | 12篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
This correspondence presents several parallel algorithms for image template matching on an SIMD array processor with a hypercube interconnection network. For an N by N image and an M by M window, the time complexity is reduced from O(N2M2) for the serial algorithm to O(M2/K2 + M * log2 N/K + log2 N * log2 K) for the N2K2-PE system (1 ? K ? M), or to O(N2M2/L2) for the L2-PE system (L ? N). With efficient use of the inter-PE communication network, each PE requires only a small local memory, many unnecessary data transmissions are eliminated, and the time complexity is greatly reduced. 相似文献
22.
A multifunctional thiophene-based covalent triazine framework (TTPATTh) with triphenylamine as core is synthesized by Friedel–Crafts reaction of cyanuric chloride with thienyl derivative for the first time. The yield of TTPATTh (99.59%) is far higher than that of the carbazole-based CTF (TTPATCz, 47.03%). TTPATTh and TTPATCz possess high BET surface areas with 1235 and 2501 m2 g–1 as well as high pore volumes with 1.60 and 2.23 cm3 g–1, respectively. TTPATTh and TTPATCz have high thermal stability with high thermal decomposition temperatures of 514 and 598 °C in nitrogen atmosphere. With the introduction of triazine rings, the fluorescence sensing sensitivities of TTPATTh and TTPATCz to picric acid and iodine are improved significantly. Especially for TTPATTh, the Ksv values reach 5.95 × 105 and 1.61 × 104 L mol–1, and LODs reach 1.02 × 10–12 and 1.86 × 10–12 mol L–1. To the best of the knowledge, this is the most sensitive value among thiophene-based porous organic polymers to PA and I2. Furthermore, TTPATTh and TTPATCz can also adsorb iodine in vapor phase, cyclohexane solution and aqueous solution, and release iodine by heating or in ethanol solution. The efficiency of controlling the release of iodine is higher than that in ethanol. 相似文献
23.
24.
25.
Summary Three PEO-PSt-PEO triblock polymers and their parent ho-nopolystyrene have been studied by means of light scattering technique
in chloroform, toluene and ethyl acetate. It has been found that the weight average molecular weights calculated by using
the equation Mapp-
were unbelievable negative values; and the largest deviation appeared for the sample with PEO mole content of about 50%.
Data of PSt-PEO-PSt triblock polymers in literature have been quoted and discussed. 相似文献
26.
27.
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
28.
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
29.
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
30.
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