全文获取类型
收费全文 | 56187篇 |
免费 | 3146篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 452篇 |
综合类 | 62篇 |
化学工业 | 12490篇 |
金属工艺 | 1165篇 |
机械仪表 | 1100篇 |
建筑科学 | 2047篇 |
矿业工程 | 190篇 |
能源动力 | 1562篇 |
轻工业 | 8884篇 |
水利工程 | 487篇 |
石油天然气 | 235篇 |
武器工业 | 8篇 |
无线电 | 2511篇 |
一般工业技术 | 9158篇 |
冶金工业 | 10703篇 |
原子能技术 | 321篇 |
自动化技术 | 8024篇 |
出版年
2023年 | 467篇 |
2022年 | 819篇 |
2021年 | 1605篇 |
2020年 | 1112篇 |
2019年 | 1309篇 |
2018年 | 1841篇 |
2017年 | 1884篇 |
2016年 | 2063篇 |
2015年 | 1643篇 |
2014年 | 2093篇 |
2013年 | 4008篇 |
2012年 | 3207篇 |
2011年 | 3598篇 |
2010年 | 2754篇 |
2009年 | 2637篇 |
2008年 | 2475篇 |
2007年 | 2192篇 |
2006年 | 1748篇 |
2005年 | 1501篇 |
2004年 | 1362篇 |
2003年 | 1177篇 |
2002年 | 1089篇 |
2001年 | 765篇 |
2000年 | 757篇 |
1999年 | 824篇 |
1998年 | 3309篇 |
1997年 | 2254篇 |
1996年 | 1519篇 |
1995年 | 890篇 |
1994年 | 744篇 |
1993年 | 801篇 |
1992年 | 327篇 |
1991年 | 310篇 |
1990年 | 243篇 |
1989年 | 250篇 |
1988年 | 248篇 |
1987年 | 227篇 |
1986年 | 188篇 |
1985年 | 235篇 |
1984年 | 197篇 |
1983年 | 148篇 |
1982年 | 181篇 |
1981年 | 193篇 |
1980年 | 210篇 |
1979年 | 102篇 |
1978年 | 109篇 |
1977年 | 366篇 |
1976年 | 770篇 |
1975年 | 86篇 |
1973年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
71.
Abraham G. Alvarado Rosaura Hernández-Montelongo Martin Rabelero Lourdes A. Pérez-Carrillo Jorge E. Puig Francisco López-Serrano 《Polymer Engineering and Science》2020,60(2):223-232
A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0-1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers 相似文献
72.
73.
74.
Antoine Depoorter Carmen Kalalian Corinne Emmelin Chantal Lorentz Christian George 《Indoor air》2021,31(3):682-692
People spend approximately 80% of their time indoor, making the understanding of the indoor chemistry an important task for safety. The high surface-area-to-volume ratio characteristic of indoor environments leads the semi-volatile organic compounds (sVOCs) to deposit on the surfaces. Using a long path absorption photometer (LOPAP), this work investigates the formation of nitrous acid (HONO) through the photochemistry of adsorbed nitrate anions and its enhancement by the presence of furfural. Using a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS), this work also investigates the surface emissions of VOCs from irradiated films of furfural and a mix of furfural and nitrate anions. Among the emitted VOCs, 2(5H)-furanone/2-Butenedial was observed at high concentrations, leading to maleic anhydride formation after UV irradiation. Moreover, the addition of potassium nitrate to the film formed NOx and HONO concentrations up to 10 ppb, which scales to ca. 4 ppb for realistic indoor conditions. This work helps to understand the high levels of HONO and NOx measured indoors. 相似文献
75.
76.
High‐intensity sweeteners in espresso coffee: ideal and equivalent sweetness and time–intensity analysis
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bruna M. Azevedo Flávio L. Schmidt Helena M. A. Bolini 《International Journal of Food Science & Technology》2015,50(6):1374-1381
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose. 相似文献
77.
78.
Hierarchical micro-nanostructured albite-based glass-ceramic for high dielectric strength insulators
V. Fuertes M.J. Cabrera J. Seores D. Muñoz J.F. Fernández E. Enríquez 《Journal of the European Ceramic Society》2018,38(7):2759-2766
A novel glass-ceramic material based on albite type Na-rich feldspar has been synthesized by conventional ceramic process. High crystallinity, >94%?Vol.% is obtained by fast sintering which allows energy saving processing. Albite is the main crystalline phase and tetragonal SiO2 is a secondary phase. Electrical properties were examined by complex impedance, DC measurements, and dielectric breakdown test. Dielectric characterization shows a non-Debye type dielectric behavior with low dielectric constant, 4.6 at 1?MHz, low dielectric losses, (~10?3 at 1?MHz, and a large dielectric strength, ~60?kV/mm), that it is the largest value reported in ceramic insulators. Those dielectric properties are attained by the low glassy phase content in the samples and their unique micro-nanostructure. All these properties make this novel material a very promising candidate in the market of ceramic electrical insulator, highlighting for high-voltage applications. 相似文献
79.
80.
Christian Veauthier Gunnar Gaede Helena Radbruch Klaus-Dieter Wernecke Friedemann Paul 《International journal of molecular sciences》2015,16(7):16514-16528
Quality of Life (QoL) is decreased in multiple sclerosis (MS), but studies about the impact of sleep disorders (SD) on health-related quality of Life (HRQoL) are lacking. From our original cohort, a cross-sectional polysomnographic (PSG) study in consecutive MS patients, we retrospectively analysed the previously unpublished data of the Nottingham Health Profile (NHP). Those MS patients suffering from sleep disorders (n = 49) showed significantly lower HRQoL compared to MS patients without sleep disorders (n = 17). Subsequently, we classified the patients into four subgroups: insomnia (n = 17), restless-legs syndrome, periodic limb movement disorder and SD due to leg pain (n = 24), obstructive sleep apnea (n = 8) and patients without sleep disorder (n = 17). OSA and insomnia patients showed significantly higher NHP values and decreased HRQoL not only for the sleep subscale but also for the “energy” and “emotional” area of the NHP. In addition, OSA patients also showed increased NHP values in the “physical abilities” area. Interestingly, we did not find a correlation between the objective PSG parameters and the subjective sleep items of the NHP. However, this study demonstrates that sleep disorders can reduce HRQoL in MS patients and should be considered as an important confounder in all studies investigating HRQoL in MS. 相似文献