全文获取类型
收费全文 | 1085篇 |
免费 | 34篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 182篇 |
金属工艺 | 39篇 |
机械仪表 | 63篇 |
建筑科学 | 20篇 |
能源动力 | 58篇 |
轻工业 | 29篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 146篇 |
一般工业技术 | 257篇 |
冶金工业 | 108篇 |
原子能技术 | 8篇 |
自动化技术 | 196篇 |
出版年
2024年 | 7篇 |
2023年 | 15篇 |
2022年 | 41篇 |
2021年 | 63篇 |
2020年 | 44篇 |
2019年 | 36篇 |
2018年 | 47篇 |
2017年 | 31篇 |
2016年 | 50篇 |
2015年 | 26篇 |
2014年 | 41篇 |
2013年 | 66篇 |
2012年 | 42篇 |
2011年 | 58篇 |
2010年 | 36篇 |
2009年 | 50篇 |
2008年 | 49篇 |
2007年 | 32篇 |
2006年 | 43篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有1127条查询结果,搜索用时 468 毫秒
101.
102.
Sumanth Shankar Diran Apelian 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):47-54
This work provides a comprehensive understanding of the reactions at the ferrous die/molten metal interface in a metal mold
casting operation. The literature has shown that several important factors influence reactions at the ferrous die/molten aluminum
interface, including temperature of the melt, temperature of the die, alloy chemistry of the melt and die, die surface engineering,
topographical features, and coatings. This article discusses the effect of the more critical factors on soldering, based on
the authors’ investigations. Inaddition, based on a mechanistic understanding of the interface reactions between ferrous die
and molten aluminum, recommendations are given for specific processing issues to alleviate soldering during die casting of
aluminum alloys. 相似文献
103.
104.
105.
Time-dependent Maxwell's equations in differential and conservation form are solved numerically, and field components are computed for scattering and penetration involving arbitrary 2-D objects using upwind computational fluid dynamics (CFD) based techniques. The Lax-Wendroff explicit scheme, which is second-order accurate in time and space, is used. The object and surrounding space are divided into a number of zones, and the Cartesian coordinate system is converted to local body-fitted coordinate systems in those zones, to handle more conveniently arbitrary geometry cross sections as well as to facilitate implementation of the boundary conditions. The method of characteristic subpath integration, better known as the Riemann solver in CFD, is then applied to the transformed Maxwell's equations, yielding the solution for the field components in the time domain. Both steady-state and transient fields can be computed. A fast Fourier transform is used to obtain frequency-domain information. Both radar cross sections and near field distributions are presented for some canonical geometries 相似文献
106.
Nisha Shankhwar Rajendra Kumar Singh Ananthakrishnan Srinivasan 《International Journal of Applied Glass Science》2017,8(1):105-115
Melt-quenched 15(ZnO,Fe2O3) 50SiO2·20(CaO,P2O5) 15Na2O bioactive glass was heat treated at temperatures (TA) ranging from 550°C to 850°C for different time periods (tA=1, 2 and 3 hours) to understand its devitrification characteristics. Crystallization of calcium sodium phosphate, zinc ferrite, magnetite, and hematite phases depended on heat treatment conditions. Decrease in saturation magnetizations (Ms) with increase in tA of glass heat treated at TA≥750°C is attributed to the formation of hematite which is a weak magnetic material. Magnetic properties as functions of TA and tA are interpreted on the basis of clustering of Fe ions, super-exchange interaction between Fe2+ and Fe3+ ions and formation of ferrimagnetic and weakly magnetic iron oxide phases with different heat treatment conditions. Electron paramagnetic resonance parameters reveal the variations in site distortions and randomness in Fe ion environment in the matrix upon heat treatment. In vitro mineralization ability of the glass-ceramics was evaluated by immersion in simulated body fluid (SBF) and monitoring both the pH variation of SBF and formation of hydroxyapatite surface layer as a function of immersion time. These studies help in assessing these glass-ceramics for hyperthermia treatment and in optimizing the processing conditions for this application. 相似文献
107.
Dr. Alexander A. Aksenov Christian E. Sandrock Dr. Weixiang Zhao Shankar Sankaran Michael Schivo Richart Harper Dr. Carol J. Cardona Dr. Zheng Xing Dr. Cristina E. Davis 《Chembiochem : a European journal of chemical biology》2014,15(7):1040-1048
Volatile organic compounds (VOCs) emanating from humans have the potential to revolutionize non‐invasive diagnostics. Yet, little is known about how these compounds are generated by complex biological systems, and even less is known about how these compounds are reflective of a particular physiological state. In this proof‐of‐concept study, we examined VOCs produced directly at the cellular level from B lymphoblastoid cells upon infection with three live influenza virus subtypes: H9N2 (avian), H6N2 (avian), and H1N1 (human). Using a single cell line helped to alleviate some of the complexity and variability when studying VOC production by an entire organism, and it allowed us to discern marked differences in VOC production upon infection of the cells. The patterns of VOCs produced in response to infection were unique for each virus subtype, while several other non‐specific VOCs were produced after infections with all three strains. Also, there was a specific time course of VOC release post infection. Among emitted VOCs, production of esters and other oxygenated compounds was particularly notable, and these may be attributed to increased oxidative stress resulting from infection. Elucidating VOC signatures that result from the host cells response to infection may yield an avenue for non‐invasive diagnostics and therapy of influenza and other viral infections. 相似文献
108.
Hemant Ramaswami Raj Shankar Shaw Sam Anand 《The International Journal of Advanced Manufacturing Technology》2011,53(9-12):963-977
Selection of the optimal set of cutting tools is one of the most important steps in process planning for 2.5-D pocket machining. Conventional CAM software requires considerable input from the user in terms of selection of tool sizes and machining strategy. This trial-and-error procedure to determine the optimal process sequence tends to generate conservative and suboptimal results. This paper presents a methodology for optimal selection of a sequence of tools to minimize the total time required to end mill a non-convex polygonal pocket with or without islands using the staircase milling strategy. The algorithm decomposes the pocket geometry into convex regions and mills each region independently by selecting a sequence of tools based on the accessibility of various tools to the region. Strategies have been developed for machining the main pass and the subsequent leftover areas in order to obtain the final pocket geometry. Subsequently, the machining times for each decomposed area are aggregated while accounting for the need to use multiple passes, non-cutting time, and the tool change time. A dynamic programming approach is used to determine the optimal set of tools which minimizes the total processing time. The effect of varying the non-cutting speed and tool change time on the tool path length and number of tool selection is studied. 相似文献
109.
Ruptures in wet-steam and single-phase water lines at fossil and nuclear plants due to erosion/corrosion of of the inside surface have resulted in comprehensive measurement of wall thickness of components prone to failure. The large number of components to be inspected as well as the required resolution to make that inspection require effective management of the large amounts of ultrasonic testing data. Recognizing this need, Northern States Power (NSP) Company initiated compilation and organization of a database which contained inspection history, component type and history, flow conditions in the component along with detailed wall thickness measurements. The database was organized using a commercially available personal computer (PC)-based database management software package.This paper discusses the background of erosion/corrosion (E/C) damage at U.S. utilities; the industry response; NDE approaches to wall thinning examination; and practical techniques used to analyze wall thickness data from components and compare data between inspection intervals. The data were compiled from nuclear and fossil units. 相似文献
110.
D Daphna-Iken DB Shankar A Lawshé DM Ornitz GM Shackleford CA MacArthur 《Canadian Metallurgical Quarterly》1998,17(21):2711-2717
Prior studies have identified Fibroblast Growth Factor-8 (Fgf8) as a possible proto-oncogene in mouse mammary tumorigenesis. We now report on the generation of two types of Fgf8 transgenic mice that each utilize the mouse mammary tumor virus (MMTV) promoter. The first transgene (MMTV-Fgf8b) results in the overexpression of the FGF8b isoform exclusively. Male and female MMTV-Fgf8b transgenic mice are viable and fertile. RNA for FGF8b is detected in mammary gland and salivary gland tissues of transgenic mice by Northern blot analysis. Nearly 85% of breeding transgenic female mice developed mammary lobular adenocarcinomas by 12 months of age, while no tumors developed in non-transgenic littermates. Salivary gland tumors occurred in some animals, always in association with mammary tumors. Several MMTV-Fgf8b transgenic mice had lung metastases at necropsy. The second transgene (MMTV-Fgf8) uses the entire Fgf8 gene and potentially encodes all FGF8 isoforms. Fgf8 is expressed by this transgene in several tissues in addition to those described above, notably the ovaries. The two MMTV-Fgf8 founders developed mammary ductal adenocarcinomas at five and eight months of age, and both displayed ovarian stromal hyperplasia. The founders expressing either transgene did not successfully nurse their pups. These results demonstrate that production of FGF8b, and possibly other FGF8 isoforms, in the mammary and salivary glands contributes to oncogenesis, and that ovarian expression results in stromal hyperplasia. 相似文献