全文获取类型
收费全文 | 27655篇 |
免费 | 2210篇 |
国内免费 | 1283篇 |
专业分类
电工技术 | 853篇 |
综合类 | 869篇 |
化学工业 | 10105篇 |
金属工艺 | 2018篇 |
机械仪表 | 318篇 |
建筑科学 | 328篇 |
矿业工程 | 741篇 |
能源动力 | 3691篇 |
轻工业 | 696篇 |
水利工程 | 34篇 |
石油天然气 | 716篇 |
武器工业 | 36篇 |
无线电 | 2248篇 |
一般工业技术 | 5801篇 |
冶金工业 | 1960篇 |
原子能技术 | 326篇 |
自动化技术 | 408篇 |
出版年
2024年 | 98篇 |
2023年 | 632篇 |
2022年 | 930篇 |
2021年 | 1209篇 |
2020年 | 1088篇 |
2019年 | 1088篇 |
2018年 | 1015篇 |
2017年 | 1048篇 |
2016年 | 934篇 |
2015年 | 918篇 |
2014年 | 1404篇 |
2013年 | 1570篇 |
2012年 | 1721篇 |
2011年 | 2310篇 |
2010年 | 1747篇 |
2009年 | 1662篇 |
2008年 | 1438篇 |
2007年 | 1572篇 |
2006年 | 1340篇 |
2005年 | 1083篇 |
2004年 | 935篇 |
2003年 | 863篇 |
2002年 | 729篇 |
2001年 | 592篇 |
2000年 | 605篇 |
1999年 | 434篇 |
1998年 | 370篇 |
1997年 | 288篇 |
1996年 | 269篇 |
1995年 | 193篇 |
1994年 | 186篇 |
1993年 | 138篇 |
1992年 | 156篇 |
1991年 | 119篇 |
1990年 | 111篇 |
1989年 | 87篇 |
1988年 | 55篇 |
1987年 | 32篇 |
1986年 | 17篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1959年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
理论分析了MOSFET关态泄漏电流产生的物理机制,深入研究了栅氧化层厚度为1.4nm MOSFET传统关态下边缘直接隧穿栅泄漏现象.结果表明:边缘直接隧穿电流服从指数变化规律;传统关态下边缘直接隧穿对长沟道器件的影响大于短沟道器件;衬底反偏在一定程度上减小边缘直接隧穿泄漏电流. 相似文献
82.
分析了萍钢将烧结矿中MgO含量提高至3.0%左右后对烧结矿产量和质量的影响,介绍了所采取的相应措施及效果. 相似文献
83.
Ambient flash sintering of reduced graphene oxide/zirconia composites:Role of reduced graphene oxide
Fabrication of graphene/ceramic composites commonly requires a high-temperature sintering step with long times as well as a vacuum or inert atmosphere,which not only results in property degradation but also significant equipment complexity and manufacturing costs.In this work,the ambient flash sintering behavior of reduced graphene oxide/3 mol% yttria-stabilized ZrO2(rGO/3 YSZ) composites utilizing rGO as both a composite component and a conductive additive is reported.When the sintering condition is carefully optimized,a dense and conductive composite can be achieved at room temperature and in the air within 20 s.The role of the rGO in the FS of the rGO/3 YSZ composites is elucidated,especially with the assistance of a separate investigation on the thermal runaway behavior of the rGO.The work suggests a promising fabrication route for rGO/ceramic composites where the vacuum and furnace are not needed,which is of interest in terms of simplifying the fabrication equipment for energy and cost savings. 相似文献
84.
用双参数模型估算复合氧化物的标准熵 总被引:8,自引:3,他引:8
提出了估算二元复合氧化物标准熵的双参数模型。用此模型可估算由CaO、SiO2、TiO2等38个简单氧化物之间形成的二元复合氧化物的标准熵,其涉及到硅酸盐、铝酸盐、钛酸盐、硼酸盐、磷酸盐、碳酸盐、硝酸盐、硫酸盐、亚硫酸盐、铁酸盐、铬酸盐、钒酸盐、钨酸盐、钼酸盐、锆酸盐、亚硒酸盐、铪酸盐、铀酸盐等多个体系。在估算已知的251个二元复合氧化物标准熵时,平均误差为435 J·mol-1·K-1,标准差为555 J·mol-1·K-1。用此双参数模型还可估算三元复合氧化物的标准熵,在估算已知的19个三元复合氧化物标准熵时,其平均误差为713 J·mol-1·K-1,标准差为1012 J·mol-1·K-1。 相似文献
85.
86.
Chia-Lung Tsai Cheng-Lung Tsai Guan-Ru He Ting-Hong Su Chang-Feng You Yow-Jon Lin 《Solid-state electronics》2011,61(1):116-120
In this study, the current-voltage characteristics of the AlCdO/unpolished p-type Si and AlCdO/polished p-type Si Schottky diodes with and without light illumination were examined. It is found that the Schottky barrier height (the series resistance) of the AlCdO/unpolished p-type Si Schottky diode is higher (lower) than that of the AlCdO/polished p-type Si Schottky diode. The power conversion efficiency of the AlCdO/p-type Si devices in the light (AM 1.5 G, 100 mW/cm2) was improved by increasing built-in potential at the AlCdO/p-type Si interfaces and reducing the device series resistance and surface reflectivity. It is shown that the device surface roughness plays an essential role in improving the device performance. 相似文献
87.
This paper presents a theoretical framework about interface states creation rate from Si-H bonds at the Si/SiO2 interface. It includes three mains ways of bond breaking. In the first case, the bond can be broken thanks to the bond ground state rising with an electrical field. In the two others cases, incident carriers will play the main role either if there are very energetic or very numerous but less energetic. This concept allows us physically modeling the reliability of MOSFET transistors, and particularly NBTI permanent part, and Channel Hot Carrier (CHC) to Cold Carrier (CCC) damage. Finally, the translation of these physical models into reliability spice models is discussed. These models pave the way to Design-in Reliability (DiR) approach which seeks to provide a quantitative assessment of reliability - CMOS device reliability in this case - at design stage thereby enabling judicious margins to be taken beforehand. 相似文献
88.
Tae Woo Kim Hana Yoo In Young Kim Hyung‐Wook Ha Ah Reum Han Jong‐San Chang Ji Sun Lee Seong‐Ju Hwang 《Advanced functional materials》2011,21(12):2301-2310
Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as‐prepared manganese oxide–aluminum oxide nanocomposite is X‐ray amorphous whereas heat‐treatment gives rise to the crystallization of an α‐MnO2 phase at 600 °C and Mn3O4/Mn2O3 and γ‐Al2O3 phases at 800 °C. Electron microscopy and N2 adsorption‐desorption‐isotherm analysis clearly demonstrate that the as‐prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ~20 nm and a surface area of >410 m2 g?1. Of particular interest is that the small particle size of the as‐prepared nanocomposite is well‐maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very‐high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals. 相似文献
89.
戴孟良 《有色冶金设计与研究》2012,33(1):21-23
介绍韶冶在氧化物料对工厂生产经营和现场环境造成不利影响的条件下,通过设备、工艺两方面的研究,提高氧化物料处理能力,从而增强烧结工艺对原料的适应性,使干精矿含硫降低,烧结机产能大幅度提升,烧结块质量保持较高水平,年创效益约2 500万元。 相似文献
90.
《Particulate Science and Technology》2012,30(8):927-931
ABSTRACTMaterials based on bismuth(III) oxide are candidate to be used in optical and electronic devices because of their properties such as a variable band gap, photoconductivity, photoluminescence, high refractive index, and dielectric permittivity. These properties are dependent of several factors, e.g., present phases and crystal morphology. The microwave-assisted hydrothermal method (MAH) is a fast and efficient approach of synthesis to obtain semiconductor powders. However, the synthesis of monoclinic bismuth oxide (α-Bi2O3) with acicular morphology by MAH was not found in literature. In this paper, microcrystals of acicular α-Bi2O3 (monophasic) were successfully obtained by MAH using a synthesis temperature of 80°C for 0.5?h. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron, and transmission electron microscopies showed the formation of a monoclinic structure (space group P21/c) with acicular morphology that grew along the [001] direction. The temperature and time necessary to synthetize acicular microcrystals were significantly lower than those found for acicular microcrystals obtained by conventional hydrothermal method. 相似文献