全文获取类型
收费全文 | 4756篇 |
免费 | 91篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 25篇 |
综合类 | 15篇 |
化学工业 | 261篇 |
金属工艺 | 35篇 |
机械仪表 | 51篇 |
建筑科学 | 47篇 |
矿业工程 | 13篇 |
能源动力 | 23篇 |
轻工业 | 226篇 |
水利工程 | 7篇 |
石油天然气 | 16篇 |
武器工业 | 1篇 |
无线电 | 62篇 |
一般工业技术 | 121篇 |
冶金工业 | 3812篇 |
原子能技术 | 14篇 |
自动化技术 | 130篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 16篇 |
2021年 | 61篇 |
2020年 | 38篇 |
2019年 | 51篇 |
2018年 | 56篇 |
2017年 | 41篇 |
2016年 | 47篇 |
2015年 | 45篇 |
2014年 | 45篇 |
2013年 | 82篇 |
2012年 | 63篇 |
2011年 | 79篇 |
2010年 | 58篇 |
2009年 | 53篇 |
2008年 | 46篇 |
2007年 | 45篇 |
2006年 | 30篇 |
2005年 | 49篇 |
2004年 | 29篇 |
2003年 | 16篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 4篇 |
1999年 | 122篇 |
1998年 | 1247篇 |
1997年 | 729篇 |
1996年 | 429篇 |
1995年 | 258篇 |
1994年 | 201篇 |
1993年 | 220篇 |
1992年 | 42篇 |
1991年 | 25篇 |
1990年 | 45篇 |
1989年 | 38篇 |
1988年 | 50篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 25篇 |
1979年 | 3篇 |
1978年 | 13篇 |
1977年 | 82篇 |
1976年 | 153篇 |
1975年 | 11篇 |
1955年 | 3篇 |
排序方式: 共有4859条查询结果,搜索用时 15 毫秒
1.
de Souza Junior Jonas Pereira Frazão Joaquim José de Morais Thais Chagas Barros Espoti Clara Degli dos Santos Sarah Marcilene Machado de Mello Prado Renato 《SILICON》2021,13(4):1269-1275
Silicon - Silicon (Si) combined with foliar spraying of salicylic acid (SA) can affect the absorption of this beneficial element. A study with Si non-accumulators plants (soybean and bean) observed... 相似文献
2.
本实验采用4D-非标记蛋白质组学技术研究秦川牛肉贮藏过程中(0~8 d)肌红蛋白含量及其衍生物的转化情况,阐释冷却秦川牛肉中肌红蛋白含量及其衍生物转化的分子机制。结果表明:贮藏过程中,肌红蛋白表达量在宰后0~4 d上升、4~8 d下降,利用非标记蛋白质组学技术鉴定出与肌红蛋白及其衍生物相关的差异蛋白14 种,具体包括代谢酶、氧化还原酶、过氧化物酶、伴侣蛋白4 类,这4 类蛋白的表达共同调控贮藏过程中肌红蛋白含量的变化及其3 种衍生物之间的转化,具体表现为贮藏过程中肌红蛋白表达量整体呈下降趋势,氧合肌红蛋白相对含量持续下降,脱氧肌红蛋白、高铁肌红蛋白相对含量逐渐增加,导致肉色发生褐变。本研究结果有利于理解秦川牛肉贮藏过程肉类变色的复杂生化变化机制。 相似文献
3.
Caio Machado Fernandes Marcos Vinícius Palmeira de Mello Nazir Escarpini dos Santos Alessandra Mendonça Teles de Souza Mauricio Lanznaster Eduardo Ariel Ponzio 《工业材料与腐蚀》2020,71(2):280-291
4-Chloro-N-(pyridin-2-ylmethyl)aniline (CPYA) was synthesized by a simple and inexpensive method and tested as a corrosion inhibitor in acid medium for mild steel by using gravimetric studies and electrochemical measurements. An average maximum efficiency of 96.0% was achieved at 4.59 mmol/L. Corrosion kinetic and thermodynamic parameters were also analyzed. Surface analyses (atomic force microscopy and scanning electron microscopy) show that protection is enabled by adsorption on the metal, forming a film. Quantum chemical calculations were performed to access information regarding the molecular structure in the corrosive medium and to support interpretation of the results obtained by experimental methods. 相似文献
4.
Gil Costa Machado Esther García-Tuñón Robert V. Bell Mauro Alini Eduardo Saiz Marianna Peroglio 《Journal of the European Ceramic Society》2018,38(3):949-961
Calcium phosphates (CaP) have been the subject of several studies that often lack a systematic approach to understanding how their properties affect biological response. CaP particles functionalised with a pH-responsive polymer (BCS) were used to prepare microporous substrates (porosity between 70 and 75% and pore sizes of 5–20 μm) through the aggregation of oil-in-water emulsions by controlling solid loading, emulsification energy, pH, drying and sintering conditions. The combined effect of surface roughness (roughness amplitude, Ra between 0.9–1.7 μm) and chemistry (varying Hydroxyapatite/β-Tricalcium phosphate ratio) on human mesenchymal stem cells was evaluated. HA substrates stimulated higher cell adhesion and proliferation (especially with lower Ra), but cell area increased with β-TCP content. The effect of surface roughness depended of chemistry: HA promoted higher mineralising activity when Ra ~ 1.5 μm, whereas β-TCP substrates stimulated a more osteogenic profile when Ra ~ 1.7 μm. A novel templating method to fabricate microporous CaP substrates was developed, opening possibilities for bone substitutes with controlled features. 相似文献
5.
6.
7.
Liu Shuai Bai Weiling Srivastava Gautam Machado J. A. Tenreiro 《Mobile Networks and Applications》2020,25(4):1537-1547
Mobile Networks and Applications - The increment of communication technologies and the development of signal processing require efficient identification techniques for communication... 相似文献
8.
Cristina Dai Prá Martens Franklin Jean Machado Mauro Luiz Martens Filipe Quevedo Pires de Oliveira e Silva Henrique Mello Rodrigues de Freitas 《International Journal of Project Management》2018,36(2):255-266
Entrepreneurial orientation (EO) is a strategic posture of an organization, and it is related to basic policies and practices for the development of entrepreneurial actions looking for creating competitive advantages. This study develops and tests a model of the relationship between entrepreneurial orientation and project success in Brazilian context. As quantitative research, a survey was used to collect data. A sample of 100 valid answers from project practitioners was treated through the structural equation modeling method. As research implications, the main result points out the positive correlation between the entrepreneurial orientation and the project success, contributing to the development of this research subject and helping to minimize the gap in the literature that addresses the relationship between project success and EO. In practical terms, understanding that innovativeness, risk taking, proactiveness, autonomy and competitive aggressiveness (the dimensions of the EO) can contribute to project success and can also indirectly impact on organizational performance, could help organizations get competitive advantage when developing correlate factors. Finally, the results suggest that practices of project management can be aligned to the firm's entrepreneurial orientation to enable firms to attain better results in their projects and generate a competitive advantage. On other hand, given the proportion of the impact of EO on project success (20.3%) identified in this study, it is critical that project management professionals expand their horizon to recognize other factors that affect project success. 相似文献
9.
Nicolle Dal’Acqua Ana Claudia Rangel Faria Mário César Vebber Hernane da Silva Barud Marcelo Giovanela Giovanna Machado Janaina da Silva Crespo 《International Journal of Hydrogen Energy》2018,43(33):15794-15806
The issues related to renewable energy sources is a matter of great worldwide appeal due to the increasing energy demand, instability in oil prices and environmental problems. In this context, the purpose of this study was to prepare self-assembled films of polyallylamine hydrochloride and poly (acrylic acid) supported onto bacterial cellulose membranes by a layer-by-layer approach with titanium dioxide (TiO2) nanoparticles and different concentrations of gold for application in hydrogen gas (H2) production by photocatalysis. The influence of the gold concentration and the presence and size of the gold nanoparticles (Au NPs), as well as the surface and thickness of the films on H2 production was investigated. The results showed that the film, prepared with a lower concentration of gold, presented the smallest Au NPs and, therefore, greater contact with the TiO2 nanoparticle surfaces, producing more H2. By analyzing the variation in all the experimental parameters used in the preparation of the films, it can be concluded that the best H2 production achieved was 29.12 μmol h?1 cm2. 相似文献