全文获取类型
收费全文 | 6189篇 |
免费 | 189篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 59篇 |
综合类 | 9篇 |
化学工业 | 1056篇 |
金属工艺 | 117篇 |
机械仪表 | 83篇 |
建筑科学 | 220篇 |
矿业工程 | 4篇 |
能源动力 | 91篇 |
轻工业 | 547篇 |
水利工程 | 31篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 378篇 |
一般工业技术 | 909篇 |
冶金工业 | 2353篇 |
原子能技术 | 59篇 |
自动化技术 | 461篇 |
出版年
2022年 | 43篇 |
2021年 | 66篇 |
2020年 | 47篇 |
2019年 | 50篇 |
2018年 | 78篇 |
2017年 | 77篇 |
2016年 | 102篇 |
2015年 | 101篇 |
2014年 | 115篇 |
2013年 | 173篇 |
2012年 | 162篇 |
2011年 | 190篇 |
2010年 | 183篇 |
2009年 | 149篇 |
2008年 | 180篇 |
2007年 | 156篇 |
2006年 | 159篇 |
2005年 | 114篇 |
2004年 | 123篇 |
2003年 | 127篇 |
2002年 | 111篇 |
2001年 | 127篇 |
2000年 | 113篇 |
1999年 | 154篇 |
1998年 | 709篇 |
1997年 | 448篇 |
1996年 | 332篇 |
1995年 | 154篇 |
1994年 | 162篇 |
1993年 | 166篇 |
1992年 | 66篇 |
1991年 | 64篇 |
1990年 | 76篇 |
1989年 | 73篇 |
1988年 | 49篇 |
1987年 | 57篇 |
1986年 | 57篇 |
1985年 | 46篇 |
1984年 | 38篇 |
1983年 | 44篇 |
1982年 | 53篇 |
1981年 | 46篇 |
1980年 | 47篇 |
1979年 | 45篇 |
1978年 | 44篇 |
1977年 | 118篇 |
1976年 | 191篇 |
1975年 | 38篇 |
1972年 | 26篇 |
1970年 | 27篇 |
排序方式: 共有6385条查询结果,搜索用时 78 毫秒
1.
2.
3.
The current study establishes the unprecedented involvement in the evolution and production of novel core–shell nanocomposites composed of nanosized titanium dioxide and aniline‐o‐phenylenediamine copolymer. TiO2@copoly(aniline and o‐phenylenediamine) (TiO2@PANI‐o‐PDA) core–shell nanocomposites were chemically synthesized in a molar ratio of 5:1 of the particular monomers and several weights of nano‐TiO2 via oxidative copolymerization. The construction of the TiO2@PANI‐o‐PDA core–shell nanocomposites was ascertained from Fourier transform IR spectroscopy, UV–visible spectroscopy and XRD. A reasonable thermal behavior for the original copolymer and the TiO2@PANI‐o‐PDA core–shell nanocomposites was investigated. The bare PANI‐o‐PDA copolymer was thermally less stable than the TiO2@PANI‐o‐PDA nanocomposites. The core–shell feature of the nanocomposites was found to have core and shell sizes of 17 nm and 19–26 nm, respectively. In addition, it was found that the addition of a high ratio of TiO2 nanoparticles increases the electrical conductivity and consequently lowers the electrical resistivity of the TiO2@PANI‐o‐PDA core–shell nanocomposites. The hybrid photocatalysts exhibit a dramatic photocatalytic efficacy of methylene blue degradation under solar light irradiation. A plausible interpretation of the photocatalytic degradation results of methylene blue is also demonstrated. Our setup introduces a facile, inexpensive, unique and efficient technique for developing new core–shell nanomaterials with various required functionalities and colloidal stabilities. © 2018 Society of Chemical Industry 相似文献
4.
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
5.
Freddy A. Bernal Dr. Marcel Kaiser Prof. Dr. Bernhard Wünsch Prof. Dr. Thomas J. Schmidt 《ChemMedChem》2020,15(1):68-78
Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model. 相似文献
6.
7.
B. Pantchev P. Danesh K. Antonova B. Schmidt D. Grambole J. Baran 《Journal of Materials Science: Materials in Electronics》2003,14(10-12):751-752
The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness. 相似文献
8.
The expression of cytokeratins (CK), involucrin, vimentin, CD34, and alpha-smooth-muscle actin was studied in fetal and adult hair follicles. The first stage of the developing hair follicle is characterized by palisaded, elongated epithelial cells budding from the epidermal basal layer. These cells express CK5/6, CK14, CK17, CK19, and vimentin. During the following weeks of gestation, different structures in the developing hair follicle can be identified and characterized. The matrical cells display only CK19. The keratinocytes of the outer root sheath express CK5/6, CK14, CK17, CK19, and involucrin; those of the inner root sheath, CK4, CK18, and involucrin; those of the isthmus, the same profile as the ORS. In the infundibulum, the basal-layer keratinocytes express CK5/6, CK14, CK17, and CK19, whereas in the suprabasal layers CK1, CK4, CK10, CK14, and CK17 are seen. The adult hair follicle in anagen fails to express CK19 in the matrical cells and isthmus and both CK17 and CK19 in the infundibulum. These profiles of intermediate filaments and other markers appear to be potentially useful in categorizing neoplasms with apparent follicular differentiation. 相似文献
9.
10.