全文获取类型
收费全文 | 13073篇 |
免费 | 1520篇 |
国内免费 | 637篇 |
专业分类
电工技术 | 821篇 |
综合类 | 952篇 |
化学工业 | 2202篇 |
金属工艺 | 795篇 |
机械仪表 | 834篇 |
建筑科学 | 957篇 |
矿业工程 | 322篇 |
能源动力 | 350篇 |
轻工业 | 1367篇 |
水利工程 | 316篇 |
石油天然气 | 603篇 |
武器工业 | 93篇 |
无线电 | 1486篇 |
一般工业技术 | 1513篇 |
冶金工业 | 512篇 |
原子能技术 | 116篇 |
自动化技术 | 1991篇 |
出版年
2024年 | 136篇 |
2023年 | 345篇 |
2022年 | 613篇 |
2021年 | 832篇 |
2020年 | 588篇 |
2019年 | 462篇 |
2018年 | 493篇 |
2017年 | 524篇 |
2016年 | 497篇 |
2015年 | 596篇 |
2014年 | 707篇 |
2013年 | 872篇 |
2012年 | 932篇 |
2011年 | 970篇 |
2010年 | 806篇 |
2009年 | 733篇 |
2008年 | 704篇 |
2007年 | 579篇 |
2006年 | 598篇 |
2005年 | 474篇 |
2004年 | 364篇 |
2003年 | 407篇 |
2002年 | 399篇 |
2001年 | 326篇 |
2000年 | 208篇 |
1999年 | 245篇 |
1998年 | 155篇 |
1997年 | 138篇 |
1996年 | 117篇 |
1995年 | 92篇 |
1994年 | 79篇 |
1993年 | 53篇 |
1992年 | 53篇 |
1991年 | 33篇 |
1990年 | 25篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
An alkali‐soluble, photocrosslinkable polymer was synthesized by esterification of OH groups of acrylic phenolic resin with maleic anhydride. The OH groups were formed by the ring‐opening reaction of epoxy groups of epoxy phenolic resin with acrylic acid. The esterification conditions were studied. The results showed that it is better to use tetramethyl ammonium bromide as catalyst than N,N‐dimethylbenzylamine. The conversion of maleic anhydride in acetone can reach about 80% at 56°C for 4 h. The purified product was characterized by IR, DSC, and TGA. The product containing acrylate and maleic acid monoester groups, above a certain content, can be dissolved in 1% Na2CO3 solution. The photocrosslinkable properties of the product were investigated through selection of photoinitiator, accelarator, crosslinkable diluent monomer, etc. The acrylate and maleic acid monoester group‐containing phenolic resin exhibited very good photocrosslinking behavior, since it contains double bonds from both acrylate groups and maleic acid monoester groups. The activity of photoinitiator decreases in the order: isopropylthioanthraquinone > benzoin ethyl ether (BE) > anthraquinone (AQ) > benzophenone > Michel ketone (MK) > 2,2‐diethoxyacetophenone. The combination of some photoinitiators showed synergistic effects. The order of increasing activity for the accelerator is as follows: MK > ethyl p‐(dimethylamino)benzoate > N,N‐dimethylaniline > triethanolamine. The optimum diluent monomer is trimethylolpropane trimethacrylate. The gel content of the mixture of the resin and trimethylolpropane trimethacrylate could reach 85% using the combined photoinitiators of BE and AQ under UV exposure for 120 s. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1607–1614, 2005 相似文献
62.
63.
Luis F. Hakim Jarod A. McCormick Guo-Dong Zhan Alan W. Weimer Peng Li Steven M. George 《Journal of the American Ceramic Society》2006,89(10):3070-3075
Surface modification of titania nanoparticles was achieved by coating them with ultrathin alumina films using atomic layer deposition. The coating process was performed in a fluidized bed reactor at low pressure and under mechanical vibration. Films were deposited using self-limiting, sequential surface reactions of trimethylaluminum and water. The composition of alumina-coated particles was verified using infrared spectroscopy. The deposited films had an average growth rate of 0.2 nm/coating cycle and were highly uniform and conformal as demonstrated by transmission electron microscopy and X-ray spectroscopy. Deposited alumina films were amorphous as verified through X-ray diffraction and high-resolution electron microscopy. The coating process did not promote particle sintering as validated via particle size and surface area analysis. 相似文献
64.
In this study, a series of T300 carbon fiber‐reinforced polyimide (CFRPI) composites were prepared by laminating premolding polyimide (PI) films with unidirectional carbon fiber (CF) layers. On the basis of PI systems design, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites was studied in detail. In addition, two kinds of nano‐particles, including carbon nano‐tube (CNT) and SiO2 were filled into the premolding PI films with different concentrations. And the effect of nano‐particles on the properties of CFRPI composites was also investigated. The surface characteristic of T300 CF was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The properties of premolding PI film and CFRPI composites were measured by dynamic mechanical analysis (DMTA), SANS testing machine, scanning electron microscopy (SEM), and so forth. These experimental results showed that the properties of CFRPI composites were mainly affected by the premolding PI film and molding condition. The change of CF volume fraction from 55% to 65% took little effect on the mechanical properties of CFRPI composites. In addition, the incorporation of nano‐particle SiO2 could further improve the properties of CFRPI composites, but CNT hardly improved the properties of CFRPI composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 646–654, 2006 相似文献
65.
从主题、内容、形式结构、语言特色、视点、表现手法、诗歌风格等方面比较<关雎>与<天皇御制歌>的异同,探寻产生其异同的原因以及由此给日本文学发展带来的影响. 相似文献
66.
OCDMA系统中变重光正交码的构造及误码率分析 总被引:1,自引:0,他引:1
变重光正交码是基于不同用户带有不同的QoS(Quality of Service)需求而提出的,由于它的码重不是固定值,使得其码字的容量较之常重光正交码有所增加.给出了变重光正交码的定义及其码字容量界,介绍了构造变重光正交码的一种方法,给出一些码字的构造结果,并对码重数不同的码字进行多址干扰误码率的仿真比较和理论分析.结果表明:在相同的码重数下,码重越大的误码率越小;而当码重数不同时,在相同的码重下,码重数大的误码率小. 相似文献
67.
68.
69.
To overcome the limitations of traditional monitoring methods, based on vibration parameter image of rotating machinery, this paper presents an abnormality online monitoring method suitable for rotating machinery using the negative selection mechanism of biology immune system. This method uses techniques of biology clone and learning mechanism to improve the negative selection algorithm to generate detectors possessing different monitoring radius, covers the abnormality space effectively, and avoids such problems as the low efficiency of generating detectors, etc. The result of an example applying the presented monitoring method shows that this method can solve the difficulty of obtaining fault samples preferably and extract the turbine state character effectively, it also can detect abnormality by causing various fault of the turbine and obtain the degree of abnormality accurately. The exact monitoring precision of abnormality indicates that this method is feasible and has better on-line quality, accuracy and robustness. 相似文献
70.
高媛媛 《武汉冶金管理干部学院学报》2010,20(2):68-70
本文分析了2004年以来国内有关于纠错对英语学习者写作准确性影响的相关研究,并对研究结果进行定性分析。分析发现,在纠正学生的写作错误时,采取教师直接纠错和标识错误处的纠错策略对学生英文写作的准确性有益,写作教师可以根据不同的错误类型灵活地选择不同的纠错方式以达到最好的效果。 相似文献