全文获取类型
收费全文 | 100506篇 |
免费 | 13124篇 |
国内免费 | 5603篇 |
专业分类
电工技术 | 8939篇 |
综合类 | 7087篇 |
化学工业 | 15802篇 |
金属工艺 | 3493篇 |
机械仪表 | 8082篇 |
建筑科学 | 6803篇 |
矿业工程 | 2799篇 |
能源动力 | 2157篇 |
轻工业 | 7622篇 |
水利工程 | 1918篇 |
石油天然气 | 2553篇 |
武器工业 | 1278篇 |
无线电 | 15184篇 |
一般工业技术 | 11415篇 |
冶金工业 | 4027篇 |
原子能技术 | 1447篇 |
自动化技术 | 18627篇 |
出版年
2024年 | 312篇 |
2023年 | 1602篇 |
2022年 | 3138篇 |
2021年 | 5078篇 |
2020年 | 3223篇 |
2019年 | 2991篇 |
2018年 | 3133篇 |
2017年 | 4321篇 |
2016年 | 5644篇 |
2015年 | 6282篇 |
2014年 | 7416篇 |
2013年 | 7227篇 |
2012年 | 6622篇 |
2011年 | 6274篇 |
2010年 | 4874篇 |
2009年 | 4915篇 |
2008年 | 5044篇 |
2007年 | 6615篇 |
2006年 | 6240篇 |
2005年 | 5245篇 |
2004年 | 3899篇 |
2003年 | 3541篇 |
2002年 | 2754篇 |
2001年 | 2123篇 |
2000年 | 1829篇 |
1999年 | 1385篇 |
1998年 | 1023篇 |
1997年 | 1087篇 |
1996年 | 827篇 |
1995年 | 678篇 |
1994年 | 651篇 |
1993年 | 476篇 |
1992年 | 398篇 |
1991年 | 309篇 |
1990年 | 316篇 |
1989年 | 221篇 |
1988年 | 167篇 |
1987年 | 143篇 |
1986年 | 106篇 |
1985年 | 117篇 |
1984年 | 153篇 |
1983年 | 81篇 |
1982年 | 98篇 |
1981年 | 78篇 |
1980年 | 75篇 |
1979年 | 33篇 |
1977年 | 32篇 |
1964年 | 42篇 |
1962年 | 67篇 |
1959年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Measuring nonlinear optical response of a specific material in a mixture, not only leads to investigate the behavior of a particular component in various circumstances, but also can be a way to select suitable combination and optimum concentration of additives and therefore obtaining the maximum nonlinear optical signals. In this work, by using dual-arm Z-scan technique, the nonlinear refractive index of Disperse Red1 (DR1) organic dye molecules inside the core of prepared polymeric nanocapsules was measured among various materials which prepared nanocapsules were made of them. Then the measured value was compared with nonlinear refractive index of DR1 solved in dichloromethane. 相似文献
92.
93.
基于传统AI-EBG结构,提出了一种小尺寸的增强型电磁带隙结构,实现了从0.5~9.4 GHz的宽频带-40 dB噪声抑制深度,且下截止频率减少到数百MHz,可有效抑制多层PCB板间地弹噪声。文中同时研究了EBG结构在高速电路应用时的信号完整性问题,使用差分信号方案可改善信号完整性。 相似文献
94.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
95.
高强不锈钢绞线网与ECC的黏结是二者协同工作的基础,且黏结 滑移关系模型是其黏结性能的综合反映,故通过对17组51个高强不锈钢绞网增强ECC薄板试件进行单边拉拔试验,研究横向钢绞线间距、纵向钢绞线直径和相对锚固长度等因素对钢绞线网在ECC中黏结性能的影响规律。试验结果表明,横向钢绞线的设置可使黏结破坏由脆性破坏转变为延性破坏;高强不锈钢绞线网与ECC的黏结滑移曲线可分为5个阶段,分别为上升段、微降段、延性强化段、下降段和残余段。基于试验结果,对钢绞线网在ECC中的黏结破坏特征和黏结 滑移机理进行分析,在相关黏结-滑移关系模型的基础上,提出钢绞线网与ECC的黏结 滑移关系模型,并进行模型参数分析。所提模型及模型参数计算公式与试验结果吻合良好,能较好地反映钢绞线网与ECC的界面黏结滑移特征。 相似文献
96.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
97.
在钳工锉配中,测量贯穿整个加工过程,千分尺和游标卡尺等传统测量方式往往不能满足加工要求。创新使用量块、百分表和正弦规进行测量,既提高了测量的效率和准确性,又保证工件的加工精度,缩短了加工工时,高质量地完成工件的加工。 相似文献
98.
Shanquan Chen Sicong Wei Fei Jin Shanming Ke Xierong Zeng Lang Chen Chuanwei Huang 《Ceramics International》2018,44(12):13695-13698
From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La0.7Sr0.3MnO3 films was studied. High quality La0.7Sr0.3MnO3 films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La0.7Sr0.3MnO3 films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La0.7Sr0.3MnO3 films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments. 相似文献
99.
Mohan B. Ponnuchamy G. Mohan Muralikrishna Venkateswara Rao Mannava G. Srinivas Reddy 《Ceramics International》2018,44(13):15019-15023
Nanocrystalline nickel oxide (NiO) was prepared from nickel hydroxide by Spark plasma sintering (SPS) and the mechanisms involved in the densification of NiO were studied. Reverse precipitated nickel hydroxide powders were SPS processed at 400, 600 and 700?°C with 70?MPa pressure. Pure NiO with 12?nm crystallite size formed after 400?°C sintering process. However NiO grains had grown to 18 and 38?nm after 600 and 700?°C sintering respectively. NiO pellets prepared using 600 and 700?°C SPS sintering schedules had relative densities of 83% and 94% respectively. Two displacement rate regimes were observed during densification of NiO in both 600 and 700?°C sintering processes. Decomposition of nickel hydroxide and particle sliding of NiO led to first displacement rate maximum while inverse Hall-Petch based plastic deformation facilitated densification during the constant second displacement rate regime. No densification occurred during sintering holding times indicating the limited role that diffusion played during densification. 相似文献
100.
Amer Ibrahim Al-Omari Ibrahim M. Almanjahie Amal S. Hassan Heba F. Nagy 《计算机、材料和连续体(英文)》2020,64(2):835-857
In reliability analysis, the stress-strength model is often used to describe the life of
a component which has a random strength (X) and is subjected to a random stress (Y). In this
paper, we considered the problem of estimating the reliability R=P [Y<X] when the
distributions of both stress and strength are independent and follow exponentiated Pareto
distribution. The maximum likelihood estimator of the stress strength reliability is calculated
under simple random sample, ranked set sampling and median ranked set sampling methods.
Four different reliability estimators under median ranked set sampling are derived. Two
estimators are obtained when both strength and stress have an odd or an even set size. The
two other estimators are obtained when the strength has an odd size and the stress has an
even set size and vice versa. The performances of the suggested estimators are compared
with their competitors under simple random sample via a simulation study. The simulation
study revealed that the stress strength reliability estimates based on ranked set sampling and
median ranked set sampling are more efficient than their competitors via simple random
sample. In general, the stress strength reliability estimates based on median ranked set
sampling are smaller than the corresponding estimates under ranked set sampling and simple
random sample methods. 相似文献