全文获取类型
收费全文 | 183133篇 |
免费 | 16613篇 |
国内免费 | 10659篇 |
专业分类
电工技术 | 8607篇 |
技术理论 | 6篇 |
综合类 | 11747篇 |
化学工业 | 56756篇 |
金属工艺 | 13603篇 |
机械仪表 | 5003篇 |
建筑科学 | 7044篇 |
矿业工程 | 4073篇 |
能源动力 | 6368篇 |
轻工业 | 16949篇 |
水利工程 | 2222篇 |
石油天然气 | 10065篇 |
武器工业 | 1040篇 |
无线电 | 16377篇 |
一般工业技术 | 22958篇 |
冶金工业 | 9195篇 |
原子能技术 | 2163篇 |
自动化技术 | 16229篇 |
出版年
2024年 | 733篇 |
2023年 | 2881篇 |
2022年 | 5490篇 |
2021年 | 6228篇 |
2020年 | 5567篇 |
2019年 | 5168篇 |
2018年 | 4849篇 |
2017年 | 5785篇 |
2016年 | 6334篇 |
2015年 | 6581篇 |
2014年 | 9503篇 |
2013年 | 10914篇 |
2012年 | 12682篇 |
2011年 | 14503篇 |
2010年 | 10972篇 |
2009年 | 11804篇 |
2008年 | 10340篇 |
2007年 | 12475篇 |
2006年 | 11536篇 |
2005年 | 9221篇 |
2004年 | 7829篇 |
2003年 | 6900篇 |
2002年 | 5710篇 |
2001年 | 4710篇 |
2000年 | 4120篇 |
1999年 | 3331篇 |
1998年 | 2564篇 |
1997年 | 1975篇 |
1996年 | 1811篇 |
1995年 | 1493篇 |
1994年 | 1351篇 |
1993年 | 1046篇 |
1992年 | 858篇 |
1991年 | 635篇 |
1990年 | 535篇 |
1989年 | 412篇 |
1988年 | 279篇 |
1987年 | 193篇 |
1986年 | 173篇 |
1985年 | 179篇 |
1984年 | 145篇 |
1983年 | 97篇 |
1982年 | 102篇 |
1981年 | 76篇 |
1980年 | 68篇 |
1979年 | 38篇 |
1978年 | 23篇 |
1977年 | 21篇 |
1975年 | 24篇 |
1951年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
4.
Effect of gums on viability and β‐galactosidase activity of Lactobacillus spp. in milk drink during refrigerated storage 下载免费PDF全文
Bernice D. Karlton‐Senaye Reza Tahergorabi Valerie L. Giddings Salam A. Ibrahim 《International Journal of Food Science & Technology》2015,50(1):32-40
The viability and β‐galactosidase activity of four Lactobacillus strains in milk drink containing gums during 28 days of refrigerated storage at 4 °C were assessed. The population of Lactobacillus rhamnosus GGB101 and Lactobacillus rhamnosus GGB103 were maintained, whereas the population of Lactobacillus reuteri DSM20016 and Lactobacillus reuteri SD2112 significantly decreased. The recommended level of 6 log CFU g?1 was exceeded for all tested trains throughout storage. The highest viable number of Lactobacillus rhamnosus GGB103 (8.76 ± 0.03 log CFU mL?1) was obtained in the product containing carrageenan–maltodextrin. The addition of guar–locust bean–carrageenan led to 20‐fold increase in the level of β‐galactosidase activity for L. rhamnosus GGB101 (1208 ± 2.12 Miller units mL?1) compared to the control (61 ± 2.83 Miller units mL?1). Our results suggested that gums could be added to milk to improve viability and enhance β‐galactosidase activity of Lactobacillus. 相似文献
5.
MC nylon-6-b-polyether amine copolymers were prepared with macro-initiator based on amino-terminated polyether amine functionalized with isocyanate via in-situ polymerization. It was found that the introduction of polyether amine delayed the polymerization process of caprolactam by increasing apparent activation energy and pre-exponential factor, resulting in the decrease of molecular weight of nylon-6. The motion of molecular chain of the copolymers was easy because of the decreased hydrogen bonds and weakened inter-molecular forces. The physical entanglement of molecular chains of the copolymers was significant and strong which increased the entanglement density. Only the nylon-6 phase crystallized in the copolymers and the crystal grain size, spherulite size and crystallinity of the copolymers decreased. A small amount of γ crystal formed at high polyether amine content. The copolymers presented obvious strain hardening behavior in stress-strain curves and the loss factor dramatically increased while the glass transition temperature and storage module decreased. The fracture surface of the copolymers became rough and presented hairy structure, indicating that the toughening mechanism of the copolymers corresponded to the multi-layer crack extension mechanism. 相似文献
6.
This paper presents an effective approach to achieve efficient electrical actuation and monitoring of shape recovery based on patterned Au electrodes on shape memory polymer (SMP). The electrically responsive shape recovery behavior was characterized and monitored by the evolution change in electrical resistance of patterned Au electrode. Both electrical actuation and temperature distribution in the SMP have been improved by optimizing the Au electrode patterns. The electrically actuated shape recovery behavior and temperature evolution during the actuation were monitored and characterized. The resistance changes could be used to detect beginning/finishing points of the shape recovery. Therefore, the Au electrode not only significantly enhances the electrical actuation performance to achieve a fast electrical actuation, but also enables the resistance signal to detect the free recovery process. 相似文献
7.
8.
9.
Through improved synthesis process, resistance reduction effect of (K0.5Bi0.5)TiO3 (KBT) doping in Y–Mn co-doped BaTiO3 (BT) lead free ceramics was investigated. By different doping methods (doping K2O, Bi2O3 and TiO2 or synthesized KBT), medium Curie temperature (around 130 °C) lead free BT ceramics were obtained with ultra-low resistivity (13.84 Ωcm) with a temperature maintaining process at 700 °C. In this contribution, effect of sintering process and doping methods is discussed in detail. 相似文献
10.
Akira Yamamoto Kentaro Teramura Saburo Hosokawa Tsunehiro Tanaka 《Science and Technology of Advanced Materials》2015,16(2)
The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. 相似文献