全文获取类型
收费全文 | 629篇 |
免费 | 116篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 19篇 |
综合类 | 56篇 |
化学工业 | 133篇 |
金属工艺 | 61篇 |
机械仪表 | 21篇 |
建筑科学 | 20篇 |
矿业工程 | 70篇 |
能源动力 | 17篇 |
轻工业 | 6篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
武器工业 | 6篇 |
无线电 | 99篇 |
一般工业技术 | 176篇 |
冶金工业 | 37篇 |
原子能技术 | 19篇 |
自动化技术 | 37篇 |
出版年
2024年 | 6篇 |
2023年 | 18篇 |
2022年 | 20篇 |
2021年 | 35篇 |
2020年 | 34篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 45篇 |
2016年 | 34篇 |
2015年 | 33篇 |
2014年 | 39篇 |
2013年 | 45篇 |
2012年 | 43篇 |
2011年 | 51篇 |
2010年 | 21篇 |
2009年 | 27篇 |
2008年 | 21篇 |
2007年 | 28篇 |
2006年 | 38篇 |
2005年 | 23篇 |
2004年 | 21篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有786条查询结果,搜索用时 15 毫秒
81.
Marindia Decol Wagner M. Pachekoski Elisa H. Segundo Luís Antônio Pinheiro Daniela Becker 《应用聚合物科学杂志》2020,137(20):48711
In this study, the effects of processing conditions through different mixing sequences were used to analyze the factors, which could influence the hybrid filler selective localization in an immiscible polymer blend and how localization can influence the rheological and thermal properties. Different selective localizations were observed depending on the mixing sequence used when the hybrid filler was added. Notably, nanoparticles can interact with each other, which favor a synergy between them and alters, besides the localization, the dispersion state, or can interact with one polymer phase, and also alter the nanoparticles' selective localization. An improvement in rheological properties was observed in the hybrid nanocomposite in which there was interaction between the nanoparticles, favoring the hexagonal boron nitride exfoliation. On the other hand, for the storage modulus and degree of crystallinity, the sharpest increase occurred in the hybrid nanocomposite in which the nanoparticles could interact preferably with one polymer phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48711. 相似文献
82.
Mei Ying Liu Tu Lai Sun Xiao Li Zhu Xiao Qiang Liu He Tian Xiang Ming Chen 《Journal of the American Ceramic Society》2021,104(12):6393-6403
Hexagonal rare-earth ferrites (h-RFeO3) have attracted much scientific attention due to their room-temperature multiferroicity. However, it is still a hard job to obtain h-RFeO3 bulk materials because of the meta-stability of such hexagonal phase, and the evaluation of room-temperature ferroelectric and magnetoelectric characteristics in such materials is also a challengeable issue. In the present work, Yb1−xInxFeO3 ceramics with the stable hexagonal structure were obtained by introducing chemical pressure, where the unique ferroelectric domain structures of sixfold vortex combined with tenfold vortex with a typical size of ~400 nm were determined. Symmetry of the present system evolved from centrosymmetric orthorhombic Pbnm (x = 0–0.4) to non-centrosymmetric hexagonal P63cm (x = 0.5 and 0.6) with a ferroelectric polarization up to 3.2 μC/cm2, and finally to centrosymmetric hexagonal P63/mmc (x = 0.7 and 0.8). The Curie point decreased monotonically from 723 K to a temperature below room temperature with increasing x, and the antiferromagnetic phase transition above room temperature was determined for all compositions. Meanwhile, a large linear magnetoelectric coefficient (αME) up to 0.96 mV/cm Oe was obtained at room temperature, and this indicated the great application potential for magnetoelectric devices. 相似文献
83.
孔内基础平台设置在现有模数空心砖孔洞的上部,在孔洞内形成小平台,其能阻止砂浆掉落孔洞内,使空心砖的保温功能得以实现。孔内基础平台的设置将砖缝层平面摩擦改变为曲面摩擦,每一个孔洞的孔内基础砂浆与砖缝层面砂浆合为一体,砖缝层面摩擦力提升,墙体抗震能力提升。 相似文献
84.
85.
The effects on water of two cooling methods, immersion in a liquid cryogen and high-pressure freezing, were studied by X-ray cryodiffraction on different sucrose solutions. The nature of the ice formed by each method depends on both the sucrose concentration and the specimen thickness. In order to compare the two methods, we mainly studied specimens having a thickness of 0.2 mm. Under these conditions, freezing by immersion gives rise to hexagonal (IH), cubic (IC) and amorphous (IV) ices when the sucrose concentration (weight/weight) has a value within the range 0–30%, 30–60%, 60% and higher, respectively. The temperature of the phase transitions IV–IC, IC–IH depends on the sucrose concentration. High-pressure freezing gives rise to two specific forms of ice: an amorphous and a crystalline ice (ice III). Ice III is observed when pure water samples are high-pressure frozen provided that the sample temperature does not rise above −150 °C. Above this temperature, ice III transforms into hexagonal ice. Amorphous ice is formed when the sucrose concentration is higher than 20%. The amorphous ice formed under high pressure has a similar, but not identical, X-ray diffraction pattern to that of amorphous ice formed at atmospheric pressure. While the X-ray diffraction pattern of amorphous ice formed at atmospheric pressure (IV) shows a broad ring at a position corresponding to 0.37 nm, that of high-pressure amorphous ice (IVHP) shows a broader ring, located at 0.35 nm. IVHP presents a phase transition (IVHP–IV) at temperatures that depend on the sucrose concentration. We also observed that some precautions have to be taken in order to minimize the alcohol contamination of high-pressure frozen samples. The ice-phase diagram presented in this paper should be taken into account in all methods dedicated to the structural study of frozen biological specimens. 相似文献
86.
Viney Ghai Harpreet Singh Bedi Jasdeep Bhinder Ankit Chauhan 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(11):907-912
AbstractThe present study introduces a process to grow micro-honeycomb (µ-HC) vertically aligned carbon nanotubes (VACNTs) using thermal chemical vapor deposition technique. Methane is used as a source of carbon and hydrogen gas as a reducing agent. Where, the fabricated µ-HC structure reported in literature involves complex synthesis process and requires a catalyst layer, the novelty of the process used here lies in the fact that no catalyst layer is used for the growth of CNT network, rather copper foil is used as a substrate. The in-situ cracking of CNTs due to water treatment leads to the formation of µ-HC CNT network, which is confirmed by Raman spectroscopy. Further scanning electron microscopy analysis shows that the length of developed µ-HC CNT is ~5?µm. Hexagonal µ-HC network shows more than 94% absorption in UV-Vis-NIR wavelength region. The designed process provides high-yield with a low-cost synthesis of vertically aligned CNTs having 3?D microarchitecture. The fabricated CNT network can be used as an electrode for supercapacitor, as an active layer in a photovoltaic cell and most of the energy harvesting devices. 相似文献
87.
88.
以钨酸钠和盐酸为原料,柠檬酸、酒石酸、对硝基苯甲酸、对氨基苯甲酸和尿素为辅助试剂,在一定温度下通过水热法制备出不同形貌的纳米三氧化钨。对所得产物进行X射线衍射(XRD)、透射电镜(TEM)和扫描电镜(SEM)的分析。结果表明:使用不同的助剂将制备不同形貌的纳米三氧化钨,推测可溶性有机酸在水热反应中起到"软模板剂"的作用,尿素在高压下产生的气体有助于增强产物的分散性,得到尺寸均匀的纳米粉体。 相似文献
89.
90.