全文获取类型
收费全文 | 59307篇 |
免费 | 4848篇 |
国内免费 | 2224篇 |
专业分类
电工技术 | 1919篇 |
技术理论 | 1篇 |
综合类 | 3204篇 |
化学工业 | 14228篇 |
金属工艺 | 1618篇 |
机械仪表 | 3110篇 |
建筑科学 | 1776篇 |
矿业工程 | 990篇 |
能源动力 | 2449篇 |
轻工业 | 11232篇 |
水利工程 | 329篇 |
石油天然气 | 19642篇 |
武器工业 | 219篇 |
无线电 | 692篇 |
一般工业技术 | 2970篇 |
冶金工业 | 1060篇 |
原子能技术 | 98篇 |
自动化技术 | 842篇 |
出版年
2024年 | 269篇 |
2023年 | 742篇 |
2022年 | 1400篇 |
2021年 | 1768篇 |
2020年 | 1890篇 |
2019年 | 1884篇 |
2018年 | 1648篇 |
2017年 | 1999篇 |
2016年 | 2192篇 |
2015年 | 2025篇 |
2014年 | 3317篇 |
2013年 | 3641篇 |
2012年 | 4047篇 |
2011年 | 4191篇 |
2010年 | 3003篇 |
2009年 | 2791篇 |
2008年 | 2513篇 |
2007年 | 3226篇 |
2006年 | 3503篇 |
2005年 | 3011篇 |
2004年 | 2612篇 |
2003年 | 2474篇 |
2002年 | 2178篇 |
2001年 | 1850篇 |
2000年 | 1638篇 |
1999年 | 1349篇 |
1998年 | 1126篇 |
1997年 | 933篇 |
1996年 | 732篇 |
1995年 | 573篇 |
1994年 | 446篇 |
1993年 | 291篇 |
1992年 | 274篇 |
1991年 | 213篇 |
1990年 | 150篇 |
1989年 | 103篇 |
1988年 | 65篇 |
1987年 | 55篇 |
1986年 | 26篇 |
1985年 | 64篇 |
1984年 | 56篇 |
1983年 | 41篇 |
1982年 | 26篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1951年 | 5篇 |
1944年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Ramesh Shruthy Stephen Jancy Radhakrishnan Preetha 《International Journal of Food Science & Technology》2021,56(8):3991-3999
In this study, the cellulose nanoparticles (CNP) isolated from potato peel were used for reinforcement of polyvinyl alcohol (PVA)-based active packaging film. The above film was used to pack the raw prawns (Penaeus monodon) at −20 °C, and the colour change, protein content, TVB-N, TMA and microbial analysis were done at regular interval for prawns stored in CNP-PVA active packaging film. A significant difference was observed in the quality of prawns stored in potato CNP-PVA film compared with prawns packed and stored in polyethylene film. The newly designed active packaging with CNP and fennel seed oil enhanced the shelf life of prawns up to two months for both HOSO (head on shell on) prawn and PD (peeled and deveined) prawn. Hence, the study recommends the potato peel CNP-PVA film with fennel seed oil as better choice to extend the shelf life of the prawns during storage compared with polyethylene packaging. 相似文献
22.
23.
电器外壳制品形状结构复杂,有两处侧凸(孔)较难处理。通过对矩形孔内侧凸的结构分析,在其局部设计了分型面,避免了使用侧向抽芯机构;对侧孔部位设计了斜顶杆侧向抽芯机构,其结构简单、紧凑。模具采用一模二腔、平衡式布局,采用经扁推杆由制品内部进料的潜伏式浇口,S型流道。在NX 8.0中完成了模具结构设计。经实践证明,该模具结构合理,产品合格。 相似文献
24.
随着我国石油需求量不断增加,致密油藏的开发也愈发重要。如何高效开发致密油藏是一项重点难点,其中致密油藏注天然气提高采收率是一个极具潜力的研究方向。因此,本文着重介绍以天然气作为能量补充介质在国内外的研究现状和应用现状,并且从两相特征等方面总结了理论研究中的一些机理,对致密油藏注天然气提高采收率的发展前景进行了一定的展望。 相似文献
25.
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
26.
Adesina Fadairo Temitope Ogunkunle Oreoluwa Lana Adebowale Oladepo Lawal Babajide 《Petroleum Science and Technology》2019,37(15):1747-1754
The chemical method has proved to be the most effective mitigating method of wax deposition in petroleum system as it deals with the root cause of wax formation. Most of the commercial chemicals in the industry are very expensive and toxic. This paper aims the use of biodiesel based additives for improving the rheological behavior and pour points of waxy crude from Nigeria field. The biodiesels derived additives gave better performance than the commercial chemical and the seed oils as greatly improvement in rheology and pour point values of the waxy crude were observed 相似文献
27.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
28.
29.
30.