全文获取类型
收费全文 | 1470篇 |
免费 | 183篇 |
国内免费 | 80篇 |
专业分类
电工技术 | 150篇 |
综合类 | 135篇 |
化学工业 | 354篇 |
金属工艺 | 31篇 |
机械仪表 | 88篇 |
建筑科学 | 31篇 |
矿业工程 | 18篇 |
能源动力 | 38篇 |
轻工业 | 44篇 |
水利工程 | 8篇 |
石油天然气 | 35篇 |
武器工业 | 10篇 |
无线电 | 346篇 |
一般工业技术 | 249篇 |
冶金工业 | 22篇 |
原子能技术 | 19篇 |
自动化技术 | 155篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 9篇 |
2021年 | 26篇 |
2020年 | 34篇 |
2019年 | 37篇 |
2018年 | 41篇 |
2017年 | 65篇 |
2016年 | 46篇 |
2015年 | 56篇 |
2014年 | 89篇 |
2013年 | 80篇 |
2012年 | 91篇 |
2011年 | 93篇 |
2010年 | 71篇 |
2009年 | 82篇 |
2008年 | 87篇 |
2007年 | 109篇 |
2006年 | 103篇 |
2005年 | 73篇 |
2004年 | 53篇 |
2003年 | 70篇 |
2002年 | 81篇 |
2001年 | 78篇 |
2000年 | 57篇 |
1999年 | 42篇 |
1998年 | 32篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1733条查询结果,搜索用时 15 毫秒
1.
《Journal of the European Ceramic Society》2021,41(13):6722-6728
Extensive researches on scintillators have been executed to satisfy the excellent radiation detection materials in broad applications. However, practical application of conventional scintillators is limited due to the limitations of high cost, time-consuming fabrication process and insufficient radioluminescence. Herein, high density precursor glass doped with Tb3+ was designed to absorb X-ray efficiently and produce green emission. Molecular dynamics simulation was used to simulate the phase separation process in melting process. Then, Tb3+-doped Ba0.84Gd0.16F2.16 glass ceramics (GCs) with excellent structural and optical properties were elaborated by melt quenching technic and further heat treating. Their structural properties, photoluminescence (PL) and X-ray excited luminescence (XEL) were explored detailedly. The internal quantum efficiency of PL is 64 % in GCs. The XEL intensity is 192 % of that of Bi4Ge3O12 (BGO) commercial scintillator. Our results suggest that Ba0.84Gd0.16F2.16:Tb3+ GCs might have potential application in X-ray detection. 相似文献
2.
光化学反应包括直接光解和间接氧化反应,其中间接氧化反应主要通过活性氧化性物种(reactive oxygen species, ROS)包括单线态氧(1O2)、过氧自由基( )和羟基自由基(·OH)等进行。近年来,有机激发三重态(3C*)作为一种特殊的氧化剂参与光化学反应引起了广泛关注。本文主要综述了有机三重态光敏剂的形成和光化学反应机制、3C*参与的环境光化学反应、3C*自由基寿命、反应速率及稳态浓度测定和激发三重态的应用5个方面,并对未来有机分子激发三重态的研究方向进行了展望,指出3C*是很多挥发性有机化合物(VOCs)或半/中等挥发性有机化合物(S/IVOCs)在大气中重要的汇,自然水体中溶解性有机质(dissolved organic matter,DOM)的激发三重态(3DOM*)是污染物降解的主要氧化剂。今后应扩大3C*与有机物反应的研究范畴,测定不同体系中3C*的稳态浓度、产生速率(量子产率)等,为污染物治理提供理论依据。 相似文献
3.
Jin Luo Jiwei Hu Xionghui Wei Lingyun Li Xianfei Huang 《International journal of molecular sciences》2015,16(1):1160-1178
This paper presents a density functional theory (DFT)/time-dependent DFT (TD-DFT) study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE) congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM). The results obtained showed that for most of the brominated diphenyl ether (BDE) congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a π–σ* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C–Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for a quantitative structure-property relationship (QSPR) study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV) and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination. 相似文献
4.
Lai-Ying Leong Teck-Soon Hew Keng-Boon Ooi Alain Yee Loong Chong Voon-Hsien Lee 《Information & Management》2021,58(2):103416
This paper examines what influences trust in mobile social commerce environment. Drawing on trust-based acceptance model (i.e. cognitive and emotional trust) and online review features (i.e. profile photo, linguistic style, and reported experience), we examine how these factors affect trust in mobile social commerce. Hypotheses were tested using survey data. The results of our model showed that there are significant influences of profile photo, reported experience, cognitive, and emotional trust towards trust in ms-commerce. This work contributes to existing literature by examining the roles of previous trust in mobile payments and online reviews on trust in mobile social commerce. 相似文献
5.
In this study, reduced graphene oxide (RGO)‐Cd(1 ? x)ZnxS nanocomposites have been synthesized with the solvothermal method in one pot. Moreover Pt, Ru, and Rh nanoparticles have been loaded on the RGO‐Cd(1 ? x)ZnxS nanocomposites as cocatalysts with the aim of increasing the photocatalytic (PC) performance for hydrogen evolution reaction. The structure of Cd(1 ? x)ZnxS blend transforms from cubic to hexagonal structure during the PC hydrogen evolution reaction (PCHER) at the room temperature. This photo‐induced phase transformation (PIPT) enhances not only the hydrogen evolution rate, but also the stability of the photocatalysts. Interestingly, RGO triggers the PIPT process only during the PCHER under solar light illumination. On the other hand, the loading of Pt, Ru, and Rh cocatalysts do not affect the PIPT process. However, they enhance the PC and photoelectrochemical (PEC) hydrogen production activity of RGO‐Cd(1 ? x)ZnxS photocatalyst. PEC performance increases about 5.5 times when Pt (5%) and RGO are added to the Cd0.60Zn0.40S catalyst. RGO‐Cd0.60Zn0.40S including 1.5% Rh photocatalyst reaches a remarkable PC hydrogen production rate of 135 μmolh?1 with QE of 23.3% at 460 nm. Therefore, Rh cocatalyst appears as a good alternative to Pt. 相似文献
6.
Mengjiao Li Feng-Shou Yang Hung-Chang Hsu Wan-Hsin Chen Chia Nung Kuo Jiann-Yeu Chen Shao-Heng Yang Ting-Hsun Yang Che-Yi Lin Yi Chou Mu-Pai Lee Yuan-Ming Chang Yung-Cheng Yang Ko-Chun Lee Yi-Chia Chou Chen-Hsin Lien Chun-Liang Lin Ya-Ping Chiu Chin Shan Lue Shu-Ping Lin Yen-Fu Lin 《Advanced functional materials》2021,31(5):2007587
Defect engineering represents a significant approach for atomically thick 2D semiconductor material development to explore the unique material properties and functions. Doping-induced conversion of conductive polarity is particularly beneficial for optimizing the integration of layered electronics. Here, controllable doping behavior in palladium diselenide (PdSe2) transistor is demonstrated by manipulating its adatom-vacancy groups. The underlying mechanisms, which originate from reversible adsorption/desorption of oxygen clusters near selenide vacancy defects, are investigated systematically via their dynamic charge transfer characteristics and scanning tunneling microscope analysis. The modulated doping effect allows the PdSe2 transistor to emulate the essential characteristics of photo nociceptor on a device level, including firing signal threshold and sensitization. Interestingly, electrostatic gating, acting as a neuromodulator, can regulate the adaptive modes in nociceptor to improve its adaptability and perceptibility to handle different danger levels. An integrated artificial nociceptor array is also designed to execute unique image processing functions, which suggests a new perspective for extension of the promise of defect engineered 2D electronics in simplified sensory systems toward use in advanced humanoid robots and artificial visual sensors. 相似文献
7.
Y. Nagasawa Y. Tachikawa E. Yamaguchi N. Tada T. Miura A. Itoh 《Advanced Synthesis \u0026amp; Catalysis》2016,358(2):178-182
A new catalytic method was developed for photo‐oxidizing the methyl group on aromatic heterocycles such as benzothiazole, benzoxazole, and quinoline to produce the corresponding aldehyde. This is the first report of the metal‐free catalytic synthesis of benzothiazole‐2‐carboxaldehydes using molecular oxygen as the terminal oxidant.
8.
垂直绿化在增加城市绿量的同时,也具有极高的审美效益。相关研究仅从使用评价角度对现状进行总结,未形成系统的垂直绿化设计方法。以景观偏好理论为基础,利用照片模拟不同密度、色彩、质感、视觉比例、图案造型等要素的商业建筑外立面垂直绿化,以此为基础进行问卷调研,对影响城市垂直绿化景观公众审美偏好的主要因素进行归纳,并提出设计建议。研究发现植物色彩丰富度、叶片质感及面域比等都在很大程度上影响垂直绿化的审美偏好。植物配置的选择应多植物组合,优先选取可观花、叶片质感光滑的植物,叶片大小以3∶5∶2的面域比为宜;图案造型的设计须充分考虑场地特征,以规则的种植形式为主,实现最佳的景观美感。 相似文献
9.
10.
通过微电子机械技术(MEMS)在抛光的熔融石英基材表面制作了平面精度达到0.4μm的超大单片面积的全息透镜。采用了分辨率达到0.2μm的步进投影式拼接光刻,适合石英基材的专用等离子耦合刻蚀(ICP)干法刻蚀技术,特殊的物理清洗方法,以及相关的多项辅助工艺。透镜理想面形横截面曲线为分段抛物线,每一片由23个柱状结构单元周期横向排列构成,采用等深度不等宽度的4台阶结构拟合,单元宽度约为2.966mm。在4in(10.16cm)圆片上,获得了单片尺寸为68mm×68mm的方形透镜。采用接触式台阶仪,扫描电子显微镜(SEM),高倍光学显微镜等方法进行不同阶段检测。结果显示:台阶平面精度为0.4μm,垂直精度为30nm,有非常好的立墙陡直度和刻蚀均匀性。此工艺方案可实现小规模批量生产,成本适中,可以直接用于制作6in(15.24cm)以上同等级要求的石英透镜,经适当改进也可用于蓝宝石等基底材料的制作。 相似文献