全文获取类型
收费全文 | 9921篇 |
免费 | 1717篇 |
国内免费 | 439篇 |
专业分类
电工技术 | 327篇 |
综合类 | 552篇 |
化学工业 | 2379篇 |
金属工艺 | 856篇 |
机械仪表 | 197篇 |
建筑科学 | 150篇 |
矿业工程 | 2074篇 |
能源动力 | 215篇 |
轻工业 | 295篇 |
水利工程 | 72篇 |
石油天然气 | 513篇 |
武器工业 | 21篇 |
无线电 | 668篇 |
一般工业技术 | 707篇 |
冶金工业 | 2605篇 |
原子能技术 | 109篇 |
自动化技术 | 337篇 |
出版年
2024年 | 39篇 |
2023年 | 253篇 |
2022年 | 390篇 |
2021年 | 499篇 |
2020年 | 443篇 |
2019年 | 416篇 |
2018年 | 340篇 |
2017年 | 420篇 |
2016年 | 472篇 |
2015年 | 444篇 |
2014年 | 585篇 |
2013年 | 635篇 |
2012年 | 719篇 |
2011年 | 720篇 |
2010年 | 477篇 |
2009年 | 524篇 |
2008年 | 446篇 |
2007年 | 506篇 |
2006年 | 531篇 |
2005年 | 434篇 |
2004年 | 370篇 |
2003年 | 376篇 |
2002年 | 300篇 |
2001年 | 279篇 |
2000年 | 251篇 |
1999年 | 213篇 |
1998年 | 178篇 |
1997年 | 128篇 |
1996年 | 132篇 |
1995年 | 107篇 |
1994年 | 84篇 |
1993年 | 85篇 |
1992年 | 57篇 |
1991年 | 61篇 |
1990年 | 40篇 |
1989年 | 31篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1964年 | 2篇 |
1957年 | 3篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
With the increase of industrialization and urbanization, humankind faces massive oil-based pollution due to tanker accidents, human error, and natural disasters. For this, hydrophobic sorbents are fabricated and their applications for the removal of oil from polluted water sources are investigated. These hydrophobic sorbents are prepared by the condensation reaction of poly(dimethylsiloxane) and tris[3-(trimethoxysilyl)propyl]isocyanurate cross-linker via bulk polymerization. The obtained sorbents exhibit high oil sorption capacity, fast absorption–desorption kinetics, and great reusability. Moreover, they can selectively absorb oil from the water surface, thus making them practical for water clean-up applications. 相似文献
2.
3.
4.
《Ceramics International》2022,48(12):16877-16884
Oxygen selective membrane on the base of cermet δ-Bi2O3/Ag with an interpenetrating structure has the maximum potential efficiency of air separation. However, the degradation processes, including the phase degradation of fluorite δ-Bi2O3, do not make it possible to create a membrane with the required perfection and durability. In this work, the ordering of oxygen vacancies with the transformation of fluorite into the rhombohedral phase (S.G. R-3) was studied by powder HT XRD in situ at 600 °C on dense Bi0.78Er0.2Hf0.02O1.51 ceramics. Fast regeneration of disordered fluorite occurs at T = 640–700 °C. The phase degradation of fluorite due to the segregation of dopants at the second stage leads into stable phases - sillenite, tetragonal or rhombohedral phase (S.G. R-3m), depending on the composition of δ-Bi2O3. Fast regeneration of fluorite occurs when heated to 820 °C, which is unacceptable for membranes. Analysis of all available data allows us to propose approaches to optimize the composition of δ-Bi2O3 and technical solutions for creating durable oxygen selective membranes with promising use in distributed multigeneration. As a result of the analysis, a new solid electrolyte with better parameters was obtained. 相似文献
5.
花生是一种重要的植物油脂和蛋白资源,水酶法处理花生能够同时得到油脂和具有特定功能的水解蛋白。为提高花生水解蛋白的纯度,在酶解前设计了酸浸过程,以除去花生体系中的可溶性糖和盐类等杂质。在单因素试验的基础上,通过正交试验优化酸浸工艺条件。结果表明,料液比和温度对蛋白质损失率及可溶性糖脱除率都有极显著或显著影响。酸浸工艺的最佳条件为料液比1∶6,处理时间30 min,pH 5,温度50℃。在最佳条件下,可溶性糖脱除率为(83. 11±0. 33)%,蛋白质损失率为(6. 19±0. 13)%。酸浸处理花生后可显著减少花生蛋白中糖的含量,但同时也伴有少量蛋白质损失。 相似文献
6.
The selective reduction of low-grade manganese ore followed by magnetic separation was proposed to produce rich-manganese ore. The optimized parameters include a roasting temperature of 1050°C, a roasting time of 6 h, a manganese ore size of 8–13 mm, and an FC/O ratio of 2.5. The reduction roasting products of low-grade manganese ore, mainly comprising of MnO, metallic iron, and residual gangue, could be separated effectively to obtain rich-manganese ore and magnetic product. The RMn, RFe, and TMn can reach the peak values of 71.00%, 93.60%, and 56.20wt%, respectively, at a rational magnetic field strength of 100 mT. In particular, the Mn/Fe ratio is up to 10.85, which meets the requirements of ferromanganese alloy smelting. 相似文献
7.
The pH-responsive microgels (MGs) consisting of methacrylic acid-ethyl acrylate (MAA-EA), methacrylic acid-butyl methacrylate (MAA-BMA) or methacrylic acid-methyl methacrylate (MAA-MMA) crosslinked with di-allyl phthalate (DAP) were synthesized via emulsion polymerization. It was found that the energy required to extract a proton from MGs with higher glass-transition temperature (Tg) was greater than at a lower Tg. Procaine hydrochloride (PrHy) was used to study the release of a model hydrophobic drug from MGs with different Tgs. A drug selective electrode (DSE) was used to monitor the release as a function of pHs and Tgs. With increasing pH or decreasing Tg, the swelling of MGs was enhanced, leading to greater release of the drug. From the Berens and Hopfenberg model, the contributions of chain relaxation and diffusion processes during a release process were determined. The drug release from lower Tg MGs and at high pH is dominated by diffusion rather than chain relaxation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47284. 相似文献
8.
Yusong Tu Pei Li Jiajia Sun Jie Jiang Fangfang Dai Chengzhang Li Yuanyan Wu Liang Chen Guosheng Shi Yanwen Tan Haiping Fang 《Advanced functional materials》2021,31(13):2008018
Despite long-term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two-orders-of-magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm ). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu2+ into Cu+, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells. 相似文献
9.
10.
An active band‐notched frequency selective absorber (BNFSA) with switchable notch band is proposed in this article. The BNFSA is a two‐layer structure composed of a lossy layer at the top and a ground plane at the bottom, separated by an air spacer. The element of the lossy layer is a lumped‐resistor‐loaded metallic dipole with a parallel LC resonance structure, which is realized by complementary n‐shaped resonator (CnR) inserted in the center, and PIN diode is welded at two arms of CnR. The bias circuit printed on the back of the substrate of the lossy layer connects to anode and cathode of the diode by via hole and isolates by the inductor. Simulation results show that the notch bands are located at 4.50 and 6.81 GHz when the diode sets to ON and OFF, respectively. To validate the performance of switchable BNFSA, the prototypes are fabricated and measured, reasonable agreement between simulated and measured results is obtained. 相似文献