全文获取类型
收费全文 | 25849篇 |
免费 | 3104篇 |
国内免费 | 1035篇 |
专业分类
电工技术 | 708篇 |
综合类 | 1571篇 |
化学工业 | 11477篇 |
金属工艺 | 724篇 |
机械仪表 | 537篇 |
建筑科学 | 1705篇 |
矿业工程 | 299篇 |
能源动力 | 3357篇 |
轻工业 | 1773篇 |
水利工程 | 323篇 |
石油天然气 | 926篇 |
武器工业 | 63篇 |
无线电 | 920篇 |
一般工业技术 | 4519篇 |
冶金工业 | 504篇 |
原子能技术 | 175篇 |
自动化技术 | 407篇 |
出版年
2024年 | 66篇 |
2023年 | 650篇 |
2022年 | 816篇 |
2021年 | 1216篇 |
2020年 | 1079篇 |
2019年 | 1036篇 |
2018年 | 784篇 |
2017年 | 959篇 |
2016年 | 889篇 |
2015年 | 885篇 |
2014年 | 1414篇 |
2013年 | 1503篇 |
2012年 | 1990篇 |
2011年 | 1953篇 |
2010年 | 1487篇 |
2009年 | 1532篇 |
2008年 | 1270篇 |
2007年 | 1652篇 |
2006年 | 1405篇 |
2005年 | 1270篇 |
2004年 | 1114篇 |
2003年 | 984篇 |
2002年 | 720篇 |
2001年 | 616篇 |
2000年 | 571篇 |
1999年 | 399篇 |
1998年 | 331篇 |
1997年 | 245篇 |
1996年 | 219篇 |
1995年 | 179篇 |
1994年 | 178篇 |
1993年 | 148篇 |
1992年 | 124篇 |
1991年 | 73篇 |
1990年 | 53篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
羟基磷灰石(HAP)由于具有无毒性、生物相容性、热稳定性、吸附性、离子交换性、结构稳定性等,因而被广泛应用到催化剂的制备中。作为一种新型催化材料,HAP的特殊晶体结构对一些反应表现出催化活性,并且经过改性、负载等方法处理过后的HAP催化剂显示出独特的催化优势。基于近年来HAP在催化邻域的发展,综述了HAP作为催化材料在降解污染物、制氢、药物合成、还原氮氧化物等反应中的不同应用,并对未来的研究方向进行了展望。 相似文献
22.
Yu-Xuan Li Ping Li Yu-Zhe Wu Zhen-Liang Xu Ming-Ling Huang 《Ceramics International》2021,47(2):2180-2186
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property. 相似文献
23.
通过对AAOA-MBR工艺在实际工程中的应用,分析该工艺处理城市污水的节能减排效能。实践表明AAOA-MBR工艺具有很强的抗冲击负荷能力,在进水质水量大幅度波动、且碳源匮乏的情况下,仍能取得良好的处理效果。实际工程运行四年来,厂区出水各项指标均稳定优于城镇污水处理厂污染物排放标准(GB 18918-2002)中的一级A标准,其中COD、BOD5、SS、NH3-N去除率分别达到可分别达到90.14%、98.25%、95.58%和98.2%;通过对运行期间污水处理量与耗电量相关关系进行回归分析可知,当处理水量达到设计规模时,其吨水耗电量预测为0.31kWh/m3。同时,基于对污水处理系统的沿程水质检测,优化进水水量分配和内循环回流比并进行产水泵联动改造,可进一步提高系统节能减排效果。 相似文献
24.
《Ceramics International》2022,48(2):2058-2067
Graphene fiber-based supercapacitor has aroused great interest as a flexible power source in future wearable electronics. However, the low electrochemical performance of graphene fibers (GFs) usually causes the serious limitation of use in practical applications due to the material stacking, hydrophobicity and fabrication process complexity. In this work, a facile and effective plasma-assisted strategy is put forward to increase specific surface area, tune hierarchically porous structure and promote wettability of nitrogen-doped graphene fibers (NGFs), resulting in the improvement of electrochemical performance. The supercapacitor assembled from plasma-treated NGFs shows superior capacitance (878 mF/cm2 at 0.1 mA/cm2 current density) and high energy density (19.5 μW h/cm2 at 40 mW/cm2 power density), which is 23.7% and 131.4% higher than that of NGFs and GFs, respectively. Additionally, the fiber-based supercapacitor based on plasma-treated NGFs exhibits high rate capability of 59.8% and excellent cyclic performance (95.8% retention over 10,000 cycles). These plasma-treated NGFs can be promising candidates for high-performance and flexible power sources in future wearable electronics. 相似文献
25.
In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. 1H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 107 Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry 相似文献
26.
Antimicrobial effects of pulsed electromagnetic fields from commercially available water treatment devices – controlled studies under static and flow conditions 下载免费PDF全文
27.
Zhao-Hua Mo Rui Yang Song Hong Yi-Xian Wu 《International Journal of Hydrogen Energy》2018,43(3):1790-1804
Introducing graphene into polymer matrix is an effective way to enhance performances of anion exchange membrane (AEM). However, utilizing the advantages of graphene by physical approach is limited due to the weak interface interaction between graphene and polymer matrix. Herein, we report an effective strategy to covalently bond graphene with polymer matrix to improve the interface interaction and further to improve the properties of AEM. A series of cross-linked quaternized graphene-based hybrid AEM were fabricated by covalently bonding poly (vinylbenzyl chloride) grafted graphene (GN-g-PVBC) copolymer with chloromethyl functionalized poly (styrene-b-isobutylene-b-styrene) (SIBS) through the cross-linker (N,N,N′,N′-tetramethyl-1,6-hexanediamine) by in-situ synthetic approach. The interface interaction between graphene and QSIBS is greatly enhanced according to micromorphology characterization of the hybrid membrane. The cross-linked quaternized hybrid AEM containing 0.55 wt% of GN-g-PVBC exhibits obviously improved dynamical mechanical properties (storage modulus: 418 MPa), ion conductivity (1.81 × 102 S cm?1), methanol barrier property (5.19 × 10?7 cm2 s?1), selectivity (3.49 × 104 S s cm?3) at 60 °C and especially a comparably excellent chemical stability to that of Nafion 115 due to the enhanced interface interaction between graphene and the polymer matrix. 相似文献
28.
29.
Ying Lang Chuan-Jin Tian Xin Dai Chang-An Wang 《International Journal of Applied Ceramic Technology》2020,17(3):974-979
Conventional preparation of porous ceramics often hard to accurately control the porosity of the samples. In this paper, by improving the foaming method, the foaming process is placed in the limited space of the ball mill tank, and YSZ porous ceramics with different porosity are obtained by changing the amount of slurry. Initial results showed that the porosity of the sample varies linearly with the increasing of addition of slurry. From the microscopic morphology, it can be seen that the increase in slurry content will reduce the number of pore with little changed size, which lead to the decrease in porosity. Therefore, with simple calculation YSZ porous ceramics with 85%, 80%, 75%, 70%, and 65% porosity can be obtained using the method of foaming in limited space by ball milling. 相似文献
30.