全文获取类型
收费全文 | 95934篇 |
免费 | 8185篇 |
国内免费 | 4660篇 |
专业分类
电工技术 | 5628篇 |
技术理论 | 3篇 |
综合类 | 8006篇 |
化学工业 | 15819篇 |
金属工艺 | 5192篇 |
机械仪表 | 5553篇 |
建筑科学 | 7416篇 |
矿业工程 | 2370篇 |
能源动力 | 2205篇 |
轻工业 | 9798篇 |
水利工程 | 1766篇 |
石油天然气 | 4724篇 |
武器工业 | 772篇 |
无线电 | 10817篇 |
一般工业技术 | 10547篇 |
冶金工业 | 4199篇 |
原子能技术 | 973篇 |
自动化技术 | 12991篇 |
出版年
2024年 | 437篇 |
2023年 | 1585篇 |
2022年 | 2884篇 |
2021年 | 3831篇 |
2020年 | 2956篇 |
2019年 | 2404篇 |
2018年 | 2536篇 |
2017年 | 2958篇 |
2016年 | 2720篇 |
2015年 | 3759篇 |
2014年 | 4953篇 |
2013年 | 5864篇 |
2012年 | 6382篇 |
2011年 | 7125篇 |
2010年 | 6532篇 |
2009年 | 6174篇 |
2008年 | 6237篇 |
2007年 | 5890篇 |
2006年 | 5650篇 |
2005年 | 4687篇 |
2004年 | 3311篇 |
2003年 | 2723篇 |
2002年 | 2740篇 |
2001年 | 2310篇 |
2000年 | 2028篇 |
1999年 | 1894篇 |
1998年 | 1472篇 |
1997年 | 1218篇 |
1996年 | 1184篇 |
1995年 | 940篇 |
1994年 | 747篇 |
1993年 | 531篇 |
1992年 | 454篇 |
1991年 | 356篇 |
1990年 | 258篇 |
1989年 | 227篇 |
1988年 | 194篇 |
1987年 | 137篇 |
1986年 | 98篇 |
1985年 | 78篇 |
1984年 | 69篇 |
1983年 | 41篇 |
1982年 | 46篇 |
1981年 | 26篇 |
1980年 | 35篇 |
1979年 | 21篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
12.
Ying Ding Chunqing Wang Yanhong Tian Binbin Zhang 《Metallurgical and Materials Transactions A》2006,37(12):1017-1025
in-situ transmission electron microscopy (TEM) tensile tests on as-cast and aged 63Sn37Pb solder alloys were conducted, and the fracture
behavior in nanometer scale ahead of the crack tip was inspected and discussed. Results show that the fracture was completed
by connecting the discontinuous cracks or voids. Dislocation behavior was concentrated along the grain boundaries for as-cast
samples, and displayed mainly as dislocation climb. The crack was intergranular dominated under the lower strain rate. While
remarkable mutual dislocation emission was detected in the aged solder. Transgranular cracks were dominant in the fractured
area, and they propagated by linking up with the nanometer scale cracks ahead of the crack tips under the effective promotion
of the inverse dislocation emission. At the same time, the partial interphase or intergranular cracks in the thinned area
were also found. Under this condition, a new critical stress intensity factor K
c
′ to define the mutual dislocation emission was proposed. 相似文献
13.
14.
印染废水处理工艺研究及实例 总被引:1,自引:0,他引:1
本文简要介绍了印染废水水质特征,提出了处理工艺,并利用两个工程实例说明了该工艺的可行性. 相似文献
15.
16.
稀土元素在陶瓷中的应用 总被引:1,自引:1,他引:0
从稀土元素的原子结构和化学特性出发,介绍了稀土元素的应用领域,阐述了稀土元素在陶瓷色釉料、各种氧化物陶瓷和非氧化物陶瓷中的应用. 相似文献
17.
A high‐melt‐strength polypropylene (HMSPP) was prepared using a twin‐screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride‐grafted polypropylene (PP‐g‐MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
18.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
19.
孔颖 《数字社区&智能家居》2007,(3):1429-1429,1438
针对C语言程序设计课程本身的特点,分析学习过程中存在的问题,强调实践的必要性。结合一些学校课程改革和实践的经验.提出面向应用的,科学的学习内容、方法和模式。同时提高学习者的专业动手能力。 相似文献
20.