全文获取类型
收费全文 | 145391篇 |
免费 | 13997篇 |
国内免费 | 9204篇 |
专业分类
电工技术 | 6064篇 |
技术理论 | 2篇 |
综合类 | 12812篇 |
化学工业 | 25914篇 |
金属工艺 | 11885篇 |
机械仪表 | 12293篇 |
建筑科学 | 11354篇 |
矿业工程 | 4093篇 |
能源动力 | 3905篇 |
轻工业 | 6661篇 |
水利工程 | 3392篇 |
石油天然气 | 4780篇 |
武器工业 | 1482篇 |
无线电 | 13848篇 |
一般工业技术 | 26172篇 |
冶金工业 | 5428篇 |
原子能技术 | 1736篇 |
自动化技术 | 16771篇 |
出版年
2024年 | 422篇 |
2023年 | 2250篇 |
2022年 | 3525篇 |
2021年 | 4715篇 |
2020年 | 4395篇 |
2019年 | 4064篇 |
2018年 | 3731篇 |
2017年 | 4604篇 |
2016年 | 5166篇 |
2015年 | 5572篇 |
2014年 | 7884篇 |
2013年 | 8381篇 |
2012年 | 9831篇 |
2011年 | 12055篇 |
2010年 | 9008篇 |
2009年 | 9967篇 |
2008年 | 8779篇 |
2007年 | 10153篇 |
2006年 | 8933篇 |
2005年 | 7691篇 |
2004年 | 6351篇 |
2003年 | 5609篇 |
2002年 | 4702篇 |
2001年 | 3371篇 |
2000年 | 3172篇 |
1999年 | 2604篇 |
1998年 | 2063篇 |
1997年 | 1750篇 |
1996年 | 1610篇 |
1995年 | 1272篇 |
1994年 | 1105篇 |
1993年 | 823篇 |
1992年 | 668篇 |
1991年 | 504篇 |
1990年 | 411篇 |
1989年 | 336篇 |
1988年 | 235篇 |
1987年 | 172篇 |
1986年 | 159篇 |
1985年 | 92篇 |
1984年 | 69篇 |
1983年 | 55篇 |
1982年 | 71篇 |
1981年 | 48篇 |
1980年 | 58篇 |
1979年 | 45篇 |
1978年 | 15篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
981.
三维立体成像及其应用 总被引:3,自引:0,他引:3
本文首先介绍了三种传统的主要三维立体成像方法,即透镜板三维成像方法,投影式三维显示和全息照相术,其次,重点对于采用计算机产生的三维立体景象的方法进行了综述,其中包括人们近年来研究较多的自动立体成像技术等,最后给出了三维立体成像技术在航空航天,工业,教育,医学,军事等领域的应用实例,并预测了三维立体成像技术今后的主要发展方向。 相似文献
982.
P. C. McIntyre B. P. Chang N. Sonnenberg M. J. Cima 《Journal of Electronic Materials》1995,24(6):735-745
Defects were characterized in epitaxial (001) CeO2 films deposited and planarizedin situ on patterned (001) LaAlO3 substrates by ion beam assisted deposition (IBAD). A hill and valley structure with steps running parallel to the [100] LaAlO3 axis was produced on the surface of the substrate by photolithography and ion beam etching prior to film deposition. A conformai
epitaxial CeO2 layer of ∼ 100 nm thickness was deposited on the heated substrate by e-beam evaporation. Lattice-matching between the e-beam
film and the substrate was of the type: (001) CeO2∥(001) LaAlO3 and [110] CeO2∥[100] LaAlO3. Evaporative deposition of additional film onto the conformai layer was accompanied by bombardment with a 500 eV argon/oxygen
ion beam to promotein situ planarization. Extreme lattice misfit for the orientation (001) CeO2∥(001)LaAlO3 and [001] CeO2∥[001] LaAlO3 caused formation of dislocations in the e-beam CeO2 film in the vicinity of individual ledges in the substrate surface. Coherence of the CeO2 film was locally lost in the step regions of the hill and valley structure. The large patterned steps, which are composed
of numerous adjacent ledges in the LaAlO3 surface, caused nucleation of CeO2 with a tilt misalignment of up to ∼5‡ about the substrate [100]. Nucleation and growth of nonepitaxial CeO2 crystallites was observed along the step regions of the film during the IBAD portion of deposition. Defect formation in the
e-beam ceria layer due to substrate surface relief indicates that “lattice engineering≓ of multilayer epitaxial structures
may not be possible when nonplanar surfaces are created during device fabrication. The IBAD CeO2 layer was more defective than the conformai layer deposited without the impinging ion beam, even in the portions of the film
where epitaxy was maintained throughout both layers. 相似文献
983.
Since proteose-peptone is a mixture of heterogeneous proteins and peptides, its functional properties have not yet been fully understood. The present study was undertaken to elucidate the emulsifying properties of proteose-peptones and a parallel evaluation was performed of the emulsifying activity of the total fraction prepared from bulk skimmed milk by precipitation with ammonium sulphate and of the most hydrophobic fraction purified by hydrophobic interaction fast protein liquid chromatography. A turbidimetric technique was used and the absorbance value at 500 nm was then directly used as the emulsifying activity index. The results obtained confirmed the good emulsifying activity of this protein fraction of the whey and demonstrated the considerable influence of the concentration on the capacity of the proteose-peptones to stabilize a model oil-in-water emulsion. Moreover, at all the concentrations examined, the purified component 3 showed a higher emulsifying activity than the total unpurified fraction. 相似文献
984.
985.
Oliver W. W. Yang 《Performance Evaluation》1995,23(3):261-284
This paper analyzes and compares the slotted time operation and the non-slotted time operation of a singleserver system with deterministic service time. These two operations are commonly used to model discrete service time systems in computer or digital communications. But due to the similarity in their operations and performance, the two models may be mixed up with each other. This paper examines by means of queueing analysis the performance of a few classes of systems that differ in the service order of their customers. The means and variances of the queue lengths, waiting times and interdeparture times of FCFS systems using the slotted time operations are first obtained from their respective LST and generating function equations. These are then used for comparison with those in non-slotted time systems. The results show that although the slotted time operation in the FCFS systems can be approximated by the non-slotted time operations under heavy traffic condition, the performances under other regions and service disciplines (e.g., the LCFS and the priority systems) may deviate significantly. They must be properly adjusted if one wishes to use the simpler equations of the non-slotted time operations to approximate the slotted time operations. The comparison graphs provided in this paper supply adjustments guidelines for the careful designers. 相似文献
986.
复合材料四结点四边形多层退化壳单元 总被引:1,自引:0,他引:1
本文提出了一个复合材料四结点四边形多层退化壳单元。单元从修正的Hu-Washizu变分原理导出,独立假设位移场、每层内部应变场和应力场。文中给出了几个复合材料板和壳静力线性问题实例。计算结果表明本文的单元是准确和有效的。 相似文献
987.
用Nardini-Brebbia边界元法计算了动载荷下的应力强度因子,与解析解及有限元解相比较,效果较好。最后对计算结果进行了分析讨论。 相似文献
988.
对连铸机浇铸之有前钢水的炉外处理技术,尤其是对炉渣的控制进行了研究,从而使钢的纯净度和连铸可浇性大大提高。 相似文献
989.
StudyofBi_2O_3-basedRareEarthSolidElectrolyteUsedinFuelCell¥HeLanying;ChenGuangyu;LiuJiang;SuWenhui(DepartmentofPhysics,JilinU... 相似文献
990.
采用高精度,高分辨率的二阶TVD有限体积方法,对二维无粘射流冲击斜板的复杂流动场进行了数值模拟,得到了和实验规律相一致的计算结果。 相似文献