全文获取类型
收费全文 | 150074篇 |
免费 | 15217篇 |
国内免费 | 6501篇 |
专业分类
电工技术 | 7688篇 |
综合类 | 9236篇 |
化学工业 | 34803篇 |
金属工艺 | 16951篇 |
机械仪表 | 9725篇 |
建筑科学 | 11014篇 |
矿业工程 | 4096篇 |
能源动力 | 6739篇 |
轻工业 | 13591篇 |
水利工程 | 2786篇 |
石油天然气 | 6680篇 |
武器工业 | 1074篇 |
无线电 | 10799篇 |
一般工业技术 | 16768篇 |
冶金工业 | 8955篇 |
原子能技术 | 2009篇 |
自动化技术 | 8878篇 |
出版年
2024年 | 329篇 |
2023年 | 2558篇 |
2022年 | 4526篇 |
2021年 | 6797篇 |
2020年 | 5002篇 |
2019年 | 4596篇 |
2018年 | 4615篇 |
2017年 | 5891篇 |
2016年 | 7097篇 |
2015年 | 7494篇 |
2014年 | 9555篇 |
2013年 | 9850篇 |
2012年 | 9686篇 |
2011年 | 9780篇 |
2010年 | 7281篇 |
2009年 | 7750篇 |
2008年 | 6901篇 |
2007年 | 9494篇 |
2006年 | 9226篇 |
2005年 | 7580篇 |
2004年 | 6073篇 |
2003年 | 5369篇 |
2002年 | 4339篇 |
2001年 | 3579篇 |
2000年 | 3042篇 |
1999年 | 2199篇 |
1998年 | 1660篇 |
1997年 | 1439篇 |
1996年 | 1390篇 |
1995年 | 1065篇 |
1994年 | 944篇 |
1993年 | 703篇 |
1992年 | 657篇 |
1991年 | 580篇 |
1990年 | 499篇 |
1989年 | 341篇 |
1988年 | 253篇 |
1987年 | 188篇 |
1986年 | 179篇 |
1985年 | 178篇 |
1984年 | 179篇 |
1983年 | 109篇 |
1982年 | 118篇 |
1981年 | 84篇 |
1980年 | 99篇 |
1979年 | 48篇 |
1977年 | 35篇 |
1964年 | 34篇 |
1962年 | 64篇 |
1959年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
针对南方客户在使用我司客车一段时间后,车身涂层不同程度出现了起泡的质量问题,进行了现场查看,发现起泡位置在车身左右侧蒙皮,且发生在涂层最底层。初步分析原因是热镀锌板+阴极电泳漆 +原子灰三者之间配套存在问题,通过热镀锌板 +阴极电泳漆 +原子灰三者之间的耐高温 80 ℃配套试验,以及室外曝晒试验,得出镀锌板表面是否钝化、电泳漆膜致密程度和原子灰苯乙烯含量是造成涂层底层起泡的主要原因。为了控制涂层起泡问题,重新修订了我司原子灰、镀锌板、电泳漆的技术标准以及部分工艺文件。 相似文献
52.
AbstractDifferent drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of chicken powders. The hygroscopicity curves and glass transition temperature were used to evaluate the influence of ambient humidity and temperature on moisture absorption of powders. The results showed that the chicken powder dried by MVD had the lowest moisture absorption, followed by IFVD, VD, and SD. The hygroscopicity of SD chicken powders was different from other three kinds of chicken powders due to the physical properties of particles and the changes of protein secondary structure as detected by the Fourier transform-infrared spectrometer. For the three vacuum drying methods, the difference of protein secondary structure was the main reason of differences in hygroscopicity. Although MVD chicken powders were slightly inferior to SD chicken powders in taste, MVD chicken powders were the best in terms of smell and color as suggested by instrumental sensory parameter evaluations. It was found that MVD had a positive effect on reducing moisture absorption and maintaining sensory quality of chicken powders. 相似文献
53.
通过对紫金山东南矿段铜钼(金)矿床地质矿化特征分析,指出铜钼矿化带主要赋存于花岗闪长斑岩的内外接触带,处于似斑状花岗闪长斑岩的上部,金矿化带赋存在表生氧化带的英安玢岩、隐爆角砾岩中。经过对矿石的组构特征、矿物生成顺序等特征分析,将矿床的成矿演化过程分为斑岩热液期、高硫化浅成低温热液期、表生氧化期三个主要矿化期次,进一步将斑岩热液期分为黑云母-钾长石化阶段、石英-绢云母化阶段、碳酸盐化阶段三个阶段;高硫化浅成低温热液期分为地开石化阶段、明矾石化阶段、硅化阶段三个阶段。研究结果为进一步研究矿床成因提供了依据。 相似文献
54.
55.
56.
针对EDEM自动划分网格较稀疏问题,采用Hypermesh划分仿真模型网格,利用Herz-Mindlin接触理论的Archard磨损模型对转载溜槽磨损问题进行仿真,在网格单元上提取出漏斗和溜管衬板的接触能量和磨损量,分析了磨损量与接触能量的关系。假设转载溜槽衬板磨损深度为物料与溜槽衬板的使用时间为线性函数,根据现场衬板磨损量的测量值,将衬板的磨损系数关系的看作隐式的单变量方程,应用EDEM软件的仿真结果求解出磨损系数的标定值。分析了漏斗和溜管的磨损机理。该方法可用于转载溜槽的磨损预测。 相似文献
57.
Malondialdehyde (MDA) was selected to represent a secondary by-product of lipid peroxidation during rice ageing. This study aimed to investigate the effects of MDA modification on the structural characteristics of rice protein. The results showed that as MDA concentration increased, rice protein carbonyl and disulphide groups increased, but sulphydryl content decreased. The blue shift of maximum fluorescence peak, the decrease of rice protein intrinsic fluorescence intensity and the reduction of surface hydrophobicity indicated the formation of protein aggregates caused by MDA oxidative modification. The results of molecular weight distribution and particle size distribution showed that MDA modification resulted in the formation of soluble protein aggregates, and the decrease of rice protein solubility indicated that insoluble protein aggregates were formed. Results of protein electrophoresis showed that MDA modification contributed to rice protein aggregation via non-disulphide covalent bonds. The results showed that rice protein gradually aggregated with increasing MDA concentration. 相似文献
58.
《Ceramics International》2020,46(2):1362-1373
Cerium oxide and silicon oxycarbide (Ce/SiOC) porous nanocomposites have been synthesized through the polymer derived ceramic route. In the synthesis of the preceramic precursors, the addition of urea facilitates the deposition of Cerium atoms on the surface of SiO2 nanoparticles since it prevents the SiO2 from agglomeration. Both Ce and urea affects the structural and textural parameters of the obtained ceramics. Less crosslinked structures are formed when the urea concentration increases and it also provokes a reduction of the carbon crystallite size. Cerium, on the other hand, induces an increase of the carbon size as well as the number of SiOC units. Pore anisotropy and smoothness of the surface are also dependent on the composition of the material. As expected, the better thermocatalytic behavior against CO2 decomposition is found at the largest Ce amounts but also, smooth surfaces and low pore anisotropies favor the accessibility of the gases to the thermocatalytic centers. 相似文献
59.
Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a
negative effect on the global environment owing to its high global warming potential (GWP) value.
An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional
perfluorocarbon etching gases such as CHF3 with C6F12O, which has a low GWP and is in a liquid
state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using
inductively coupled CF4 +C6F12O+O2 mixed plasmas. Subsequently, the etching characteristics
of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated.
A double Langmuir probe was used and optical emission spectroscopy was performed for plasma
diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used
to confirm the change in the surface properties of the etched SiON film surface. Consequently, the
etching characteristics of the C6F12O mixed plasma exhibited a lower etching rate, higher SiON/Si
selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF3 mixed plasma. In addition, the C6F12O gas can be recovered in the liquid state, thereby decreasing
global warming. These results confirmed that the C6F12O precursor can sufficiently replace the
conventional etching gas. 相似文献
60.
本文设计了在泳池式轻水反应堆(简称泳池堆)内在线测量电磁线圈电性能的可控温辐照装置。采用MCNP程序进行中子物理计算,对泳池堆、线圈骨架的结构尺寸与物质组分进行了精细全尺寸模拟,得出辐照装置的发热功率和中子注量率。通过初步估算,使用ANSYS CFX进行了数值模拟,得出辐照装置内线圈在堆运行时的温度,并提出温度控制的方法。辐照装置采用铝材加工制造,并进行了垂直度测试、气压测试、检漏测试。增加了绝缘设计,将辐照装置与泳池堆之间进行绝缘。在线圈处预埋铠装热电偶,对线圈温度进行实时监测。在泳池堆内对电磁线圈进行辐照试验,结果表明,本文设计的辐照装置能满足电磁线圈在泳池堆孔道内进行辐照试验的要求,并可对电磁线圈进行实时温度控制。 相似文献