全文获取类型
收费全文 | 42362篇 |
免费 | 4266篇 |
国内免费 | 1834篇 |
专业分类
电工技术 | 4190篇 |
技术理论 | 4篇 |
综合类 | 2552篇 |
化学工业 | 4873篇 |
金属工艺 | 1668篇 |
机械仪表 | 2771篇 |
建筑科学 | 1917篇 |
矿业工程 | 654篇 |
能源动力 | 5556篇 |
轻工业 | 6855篇 |
水利工程 | 1015篇 |
石油天然气 | 1750篇 |
武器工业 | 259篇 |
无线电 | 2295篇 |
一般工业技术 | 5147篇 |
冶金工业 | 1225篇 |
原子能技术 | 322篇 |
自动化技术 | 5409篇 |
出版年
2024年 | 258篇 |
2023年 | 1152篇 |
2022年 | 1672篇 |
2021年 | 1991篇 |
2020年 | 1929篇 |
2019年 | 1805篇 |
2018年 | 1486篇 |
2017年 | 1596篇 |
2016年 | 1581篇 |
2015年 | 1565篇 |
2014年 | 2563篇 |
2013年 | 2554篇 |
2012年 | 2904篇 |
2011年 | 2971篇 |
2010年 | 2301篇 |
2009年 | 2214篇 |
2008年 | 1971篇 |
2007年 | 2407篇 |
2006年 | 2278篇 |
2005年 | 1851篇 |
2004年 | 1695篇 |
2003年 | 1445篇 |
2002年 | 1185篇 |
2001年 | 980篇 |
2000年 | 809篇 |
1999年 | 657篇 |
1998年 | 472篇 |
1997年 | 382篇 |
1996年 | 322篇 |
1995年 | 253篇 |
1994年 | 230篇 |
1993年 | 170篇 |
1992年 | 158篇 |
1991年 | 109篇 |
1990年 | 75篇 |
1989年 | 67篇 |
1988年 | 61篇 |
1987年 | 55篇 |
1986年 | 42篇 |
1985年 | 55篇 |
1984年 | 34篇 |
1983年 | 35篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
41.
Mauro D. Santos Ivonne Delgadillo Jorge A. Saraiva 《International Journal of Food Science & Technology》2020,55(3):1171-1179
Hyperbaric storage (HS) was evaluated as a new food preservation methodology at room temperature (RT) for beef and pork meat, both minced and in pieces, and compared to refrigeration (RF) storage. The meat samples were stored at 50, 75 and 100 MPa and variable RT up to 60 days. HS at 75 and 100 MPa could not only inhibit microbial growth but also inactivate microorganisms. Regarding physicochemical analyses, an overall equal to better pH maintenance in HS samples was achieved, and similar colour differences between HS and RF were observed. Generally, similarities in moisture content and drip loss between HS (mostly 75 and 100 MPa) and RF were detected (tendency for lower values in the former and higher values in the latter for the higher pressure level). Protein solubility revealed a decrease of sarcoplasmic protein values during storage with a pressure level dependency in some samples. 相似文献
42.
43.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
44.
Katarzyna Samborska Elwira Langa Sławomir Bakier 《International Journal of Food Science & Technology》2015,50(6):1359-1365
Honey powders produced by spray drying with the addition of Arabic gum and sodium caseinate were characterised in terms of the influence of storage time on the following physical properties: particle size, moisture content, water activity, bulk density, flowability and hygroscopicity. The storage affected those properties; after 12 weeks of storage, particle size decreased (except Arabic gum powder treated as a control sample), moisture content and water activity increased, hygroscopicity decreased. Changes in bulk density, particle size and moisture content caused the rise of Hausner ratio value; however, the powders were still characterised by a very good flow properties and low cohesiveness. The colour of reconstituted powders was also affected by storage; in most of samples, the darkening, reduction in redness and yellowness were observed. Colour parameters were the most stable in powders obtained with the addition of 2% w/w of sodium caseinate. 相似文献
45.
从硬件和软件两个角度出发,介绍基于DSP的多元数据同步采集与存储系统的组成、工作模式以及功能的测试。系统主要由上位机和数字采集与存储单元组成,其中数字采集与存储单元的硬件部分包括电源模块,值班电路模块,数据采集模块,数据存储模块,时钟同步模块。系统采用DSP作为中央处理芯片,利用经过同步后的秒脉冲作为触发信号,实现同步数据采集。以CF卡作为存储介质,实现数据自容式存储。软件部分实现自检、同步、数据采集存储功能。经过测试,系统工作稳定,功能正常,同步精度在100ns以内。 相似文献
46.
A novel synthetic route has been proposed to prepare hausmannite nanoparticles. The synthetic route comprises an iron mediated constant current cathodic electrodeposition of manganite and heat treatment of the latter to obtain hausmannite. The obtained nanostructures have been characterized using X-ray Diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and Fourier transform Infrared Spectrometry (FTIR). The role of iron in the formation of manganite precursor has been studied by cyclic voltammetry (CV) and differential thermal analysis (DTA). A formation mechanism based on iron mediated formation of Mn3+ and subsequent cathodic reduction of the disproportionated products has been proposed accordingly. The prepared nanoparticles exhibited specific capacitance of 143 F g−1 in 0.5 M Na2SO4 solution. The retained specific capacity was 87% after 2000 cycles. 相似文献
47.
Manal Benyoussef Moneim Zannen Jamal Belhadi Bouchaib Manoun Jean-Luc Dellis Mimoun El Marssi Abdelilah Lahmar 《Ceramics International》2018,44(16):19451-19460
In this work, Na0.5(Bi1-xDyx)0.5TiO3 (0?≤?x?≤?15%) ceramics were prepared via solid state reaction method and were characterized. A stable and pure perovskite phase was revealed by X-ray diffraction analysis for all compositions and a symmetry change from rhombohedral to orthorhombic phase was detected beyond 10% of Dy substitution. The incorporation of Dy3+ into Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) matrix allows a substantial decrease of the coercive field, an increase in the resistivity, and leads to a high stability of the dielectric permittivity (??/?(150?°C) ≤?±?15%) over a wide temperature range. Furthermore, this system was found to exhibit improved energy storage properties at high temperatures with a maximum energy density of 1.2?J/cm3 obtained for 2%Dy composition at 200?°C. The obtained results are very promising for energy storage capacitors operating at high temperatures. 相似文献
48.
49.
分析了蓄电池组在使用过程受损的原因,介绍了一种蓄电池组在线修复的新技术,即扫描共振频率技术的基本工作原理,并进一步分析、介绍了该在线修复方法所采用的主要新技术和独特的优点。 相似文献
50.