全文获取类型
收费全文 | 1736篇 |
免费 | 88篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 5篇 |
综合类 | 105篇 |
化学工业 | 633篇 |
金属工艺 | 45篇 |
机械仪表 | 19篇 |
建筑科学 | 21篇 |
矿业工程 | 23篇 |
能源动力 | 17篇 |
轻工业 | 695篇 |
水利工程 | 11篇 |
石油天然气 | 26篇 |
无线电 | 35篇 |
一般工业技术 | 171篇 |
冶金工业 | 50篇 |
原子能技术 | 7篇 |
自动化技术 | 6篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 28篇 |
2021年 | 58篇 |
2020年 | 40篇 |
2019年 | 43篇 |
2018年 | 48篇 |
2017年 | 48篇 |
2016年 | 73篇 |
2015年 | 78篇 |
2014年 | 97篇 |
2013年 | 96篇 |
2012年 | 187篇 |
2011年 | 163篇 |
2010年 | 107篇 |
2009年 | 127篇 |
2008年 | 85篇 |
2007年 | 120篇 |
2006年 | 107篇 |
2005年 | 61篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 37篇 |
2001年 | 28篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有1869条查询结果,搜索用时 0 毫秒
1.
Injun Lee Taeseong Jung Junggi Kim Suho Ro Chulsu Kim Yeji Lee Youngmi Kim Juhyun Lee Misook Kang 《Journal of Industrial and Engineering Chemistry》2008,14(6):869-873
This study focuses on the relationship between photo-catalytic performance and optical property over Si-incorporated TiO2. The Si-incorporated TiO2 particles exhibited a pure structure of anatase having a particle size of less than 20 nm and surface area of more than 190 m2/g. The absorbance did not shift to a higher wavelength in spite of the incorporation of the Si ions, but the intensity of the photoluminescence (PL) curve was the smallest in the case of the 2.0 mol% Si-TiO2, which was related to the recombination between the excited electrons and holes. Based on these results, the photodecomposition of methyl orange in the liquid reaction was enhanced over the 2.0 mol% Si-incorporated TiO2 compared with that over pure TiO2: Methyl orange at 10.0 ppm was completely decomposed after 100 min when 1.0 g of the 2.0 mol% Si-incorporated TiO2 was used. 相似文献
2.
Photocatalytic degradation of methyl orange using heteropolytungstic acid-encapsulated TiSBA-15 总被引:1,自引:0,他引:1
Heteropolyphosphotungstic acid (H3PW12O40) (HPA)-encapsulated titanium-supported SBA15 nanoporous materials (HPA-TiSBA-15) were synthesized as a new photocatalyst, and they were characterized by FT-IR and 31P NMR MAS spectroscopic methods. Their photocatalytic effects on degradation of methyl orange in water were investigated under natural conditions, and it was found that a 4-fold increase in the photodegradation rate is observed in the presence of HPA-TiSBA-15 as compared to the rate observed in the presence of titanium-supported SBA15 nanoporous materials (TiSBA-15) without HPA. 相似文献
3.
Nanocrystalline thin films of important surface roughness and complexity were prepared by screen-printing of commercial TiO2 powder. The screen-printed titania films were tested in the photocatalytic decomposition reaction of methyl orange under UV light (350 nm). The photocatalytic activity strongly depends on the titania paste components and especially on the presence of a surface modifier (acetyl acetone) combined with a rheology controlling agent (ethyl cellulose). This results in improvement of the paste viscosity and optimization of the films morphology. Experiments under direct full sunlight illumination prove the importance of the screen-printed films for practical applications. 相似文献
4.
Thermodynamic parameters have been determined for the interaction of methyl orange and poly(vinylpyrrolidone) in aqueous solutions containing tris, tris and hydrochloric acid, or water only. Enthalpy changes were determined by use of a flow microcalorimeter. Free energy changes were calculated from the results of equilbrium dialysis studies. The results are interpreted in terms of the behaviour of poly(vinylpyrrolidone) in these systems. Analysis of data shows that the hydrophobic interactions in the systems are in the order: tris > wateronly > tris-HC1. 相似文献
5.
6.
Sean R. Tachibana Longteng Tang Liangdong Zhu Yuka Takeda Keiji Fushimi Yoshibumi Ueda Takahiro Nakajima Yuto Kuwasaki Moritoshi Sato Rei Narikawa Chong Fang 《International journal of molecular sciences》2021,22(10)
Cyanobacteriochromes (CBCRs) are promising optogenetic tools for their diverse absorption properties with a single compact cofactor-binding domain. We previously uncovered the ultrafast reversible photoswitching dynamics of a red/green photoreceptor AnPixJg2, which binds phycocyanobilin (PCB) that is unavailable in mammalian cells. Biliverdin (BV) is a mammalian cofactor with a similar structure to PCB but exhibits redder absorption. To improve the AnPixJg2 feasibility in mammalian applications, AnPixJg2_BV4 with only four mutations has been engineered to incorporate BV. Herein, we implemented femtosecond transient absorption (fs-TA) and ground state femtosecond stimulated Raman spectroscopy (GS-FSRS) to uncover transient electronic dynamics on molecular time scales and key structural motions responsible for the photoconversion of AnPixJg2_BV4 with PCB (Bpcb) and BV (Bbv) cofactors in comparison with the parent AnPixJg2 (Apcb). Bpcb adopts the same photoconversion scheme as Apcb, while BV4 mutations create a less bulky environment around the cofactor D ring that promotes a faster twist. The engineered Bbv employs a reversible clockwise/counterclockwise photoswitching that requires a two-step twist on ~5 and 35 picosecond (ps) time scales. The primary forward Pfr → Po transition displays equal amplitude weights between the two processes before reaching a conical intersection. In contrast, the primary reverse Po → Pfr transition shows a 2:1 weight ratio of the ~35 ps over 5 ps component, implying notable changes to the D-ring-twisting pathway. Moreover, we performed pre-resonance GS-FSRS and quantum calculations to identify the Bbv vibrational marker bands at ~659,797, and 1225 cm−1. These modes reveal a stronger H-bonding network around the BV cofactor A ring with BV4 mutations, corroborating the D-ring-dominant reversible photoswitching pathway in the excited state. Implementation of BV4 mutations in other PCB-binding GAF domains like AnPixJg4, AM1_1870g3, and NpF2164g5 could promote similar efficient reversible photoswitching for more directional bioimaging and optogenetic applications, and inspire other bioengineering advances. 相似文献
7.
三相流化床中光催化降解反应特性的研究 总被引:11,自引:0,他引:11
在设计并建立的流态化光催化反应器中,采用负载型光催化剂对甲基橙水溶液进行了光催化降解实验研究。优化了三相流化状态下光催化反应器的操作条件, 其结果为:气体流量200-250Lh-1,液体流量30 Lh-1,催化剂用量为1.5gkg-1处理液;考察了该反应器中催化剂的使用寿命,为光催化降解技术的工业应用研究提供了参考。 相似文献
8.
合成了SiW10Fe2的季胺盐(Fe2POM),并对其结构进行了表征.以Fe2POM为催化剂,研究了甲基橙的起始浓度、催化剂添加量、不同pH值等因素对光脱色速率的影响.利用异丙醇作为·OH捕获剂,探讨了甲基橙在Fe2POM-H2O2体系中的光化学脱色规律和机制.结果表明:体系在较宽的pH范围内具有高的光脱色活性,40—160mg/L初始质量浓度范围内,甲基橙的脱色速率随初始浓度降低而升高,脱色过程符合表观一级反应动力学规律.各体系的光脱色活性依次为:Fe2POM-H2O2单纯的Fe2POM>单纯的光照. 相似文献
9.
[目的]建立了甜橙全果、果肉、果皮、果渣、橙汁和精油等6项基质中哒螨灵和螺螨酯的QuEChERS-高效液相色谱-串联质谱分析检测方法(HPLC-MS/MS)。[方法]甜橙样品经乙腈提取,PSA、GCB、MgSO4净化,高效液相色谱-串联质谱仪配备电喷雾正离子多反应监测(MRM),外标法定量。[结果]甜橙6种基质通过此分析检测方法,哒螨灵和螺螨酯在0.001~1.25 mg/L质量浓度范围线性相关系数不小于0.9965,3个加标水平(0.01、0.5、5 mg/kg)下哒螨灵回收率为81%~93%,RSD为0.5%~6.5%,螺螨酯回收率为81%~99%,RSD为0.5%~7.9%。[结论]该方法简单、方便、灵敏度、准确度高,覆盖甜橙全项样品基质,可适用于大批量样品快速分析。 相似文献
10.
用沸腾回流直接水解法制备了粒径为25~35 nm纯锐钛矿型纳米二氧化钛(TiO2).用X射线衍射和透射电镜表征材料的结构与形貌.用该催化剂催化降解甲基橙,研究了催化剂用量、甲基橙的起始浓度、溶液pH值、光强度、溶液中添加金属离子的影响.结果表明:在较强紫外光照射下,当甲基橙的起始浓度为0.02 g/L,TiO2用量为1.0g/L,光催化效率最高.酸性条件有利于光催化降解甲基橙.掺加Fe3 或Zn2 的光催化效率显著增加.掺加Mn2 或Ca2对光催化活性没有影响.在紫外光区域(366 nm),样品对催化降解水溶液中甲基橙的活性较高. 相似文献