全文获取类型
收费全文 | 4767篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 4篇 |
化学工业 | 245篇 |
金属工艺 | 51篇 |
机械仪表 | 25篇 |
建筑科学 | 38篇 |
矿业工程 | 5篇 |
能源动力 | 18篇 |
轻工业 | 140篇 |
水利工程 | 11篇 |
石油天然气 | 4篇 |
无线电 | 190篇 |
一般工业技术 | 322篇 |
冶金工业 | 3557篇 |
原子能技术 | 23篇 |
自动化技术 | 141篇 |
出版年
2022年 | 12篇 |
2021年 | 18篇 |
2019年 | 14篇 |
2018年 | 23篇 |
2017年 | 27篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 28篇 |
2013年 | 34篇 |
2012年 | 51篇 |
2011年 | 60篇 |
2010年 | 51篇 |
2009年 | 43篇 |
2008年 | 61篇 |
2007年 | 68篇 |
2006年 | 34篇 |
2005年 | 39篇 |
2004年 | 33篇 |
2003年 | 46篇 |
2002年 | 34篇 |
2001年 | 43篇 |
2000年 | 37篇 |
1999年 | 141篇 |
1998年 | 1069篇 |
1997年 | 612篇 |
1996年 | 404篇 |
1995年 | 221篇 |
1994年 | 190篇 |
1993年 | 218篇 |
1992年 | 47篇 |
1991年 | 52篇 |
1990年 | 60篇 |
1989年 | 65篇 |
1988年 | 73篇 |
1987年 | 80篇 |
1986年 | 56篇 |
1985年 | 55篇 |
1984年 | 16篇 |
1983年 | 29篇 |
1982年 | 22篇 |
1981年 | 35篇 |
1980年 | 49篇 |
1979年 | 24篇 |
1978年 | 27篇 |
1977年 | 110篇 |
1976年 | 250篇 |
1975年 | 17篇 |
1974年 | 8篇 |
1973年 | 13篇 |
1970年 | 7篇 |
排序方式: 共有4795条查询结果,搜索用时 484 毫秒
1.
Luca Pietrobon Lorenzo Fallarino Andreas Berger Andrey Chuvilin Flix Casanova Luis E. Hueso 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(47):6295-6301
Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials. 相似文献
2.
3.
Behavior of Magnesium‐Alloys for Automotive Applications under Mechanical and Environmental Loading: Influence of Passivating Films and Mechanisms of Local Breakdown To assure an efficient design of components under cyclic loading, all available data concerning fatigue have to be observed. Therefore the influences of manufacturing on the material condition, the mechanical loads and environmental effects have to be analysed. Magnesium‐alloys are of special interest for lightweight applications because of their excellent strength‐density ratio. The corrosion resistance of magnesium‐alloys depends on the same factors that are critical to other metals. The alloys have a good stability to atmospheric exposure and a good resistance to attack by alkali, chromic and hydrofluoric acids. However, because of the electrochemical activity of magnesium, the relative importance of some factors is greatly amplified. The nature and composition of passive films formed on magnesium‐alloys depend on the prevailing conditions, viz. alloy‐composition, passivation potential, pH, electrolyte composition and temperature. Passive films may be damaged by local breakdown. Because of this, magnesium‐alloys suffer a degradation of their properties when exposed to an aqueous environment. The main topic of the present investigations is the verification of mechanisms of the local breakdown of the protecting film. At least two mechanisms are possible for this localization: mechanical breakdown by slip steps and electrochemical breakdown (for e.g. by the effects of chloride ions). Corrosion and passivation of different high purity alloys have been studied in different solutions (neutral, alkaline with specific anions and cations) using electrochemical techniques. The diecasted alloys were tested as produced and machined. The results clarified that depending on alloy/material and surface condition/corrosion environment different mechanisms for electrochemical breakdown of the protecting films are possible. Hence fatigue life under environmental loading is influenced by surface and testing conditions. 相似文献
4.
Math1 is essential for genesis of cerebellar granule neurons 总被引:1,自引:0,他引:1
N Ben-Arie HJ Bellen DL Armstrong AE McCall PR Gordadze Q Guo MM Matzuk HY Zoghbi 《Canadian Metallurgical Quarterly》1997,390(6656):169-172
5.
6.
7.
Jun Chen Berger T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(8):3385-3398
We consider a distributed source coding system in which several observations must be encoded separately and communicated to the decoder by using limited transmission rate. We introduce a robust distributed coding scheme which flexibly trades off between system robustness and compression efficiency. The optimality of this coding scheme is proved for various special cases. 相似文献
8.
A. Alt Dr.‐Ing. H. Mertens U. Arz L. Blessing C. Berger 《Materialwissenschaft und Werkstofftechnik》2007,38(5):402-409
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence. 相似文献
9.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
10.
HJ Voeller M Augustus V Madike GS Bova KC Carter EP Gelmann 《Canadian Metallurgical Quarterly》1997,57(20):4455-4459
Loss of heterozygosity at chromosome 8p21-22 is common in human prostate cancer, suggesting the presence of one or more tumor suppressor genes at this locus. A homeobox gene that is expressed specifically in adult human prostate, NKX3.1, the expression of which is regulated by androgen, maps to chromosome 8p21. Fine structure in situ mapping showed that NKX3.1 is proximal to MSR32 (macrophage scavenger receptor type II) and LPL (human lipoprotein lipase) and very close to NEFL (human neurofilament light chain) on 8p21. Single-strand conformational polymorphism analysis of 48 radical prostatectomy cancer specimens and 3 metastases for the entire coding region of NKX3.1 showed no tumor-specific sequence alterations in 50 specimens and total absence of the gene in 1 specimen known to have a biallelic deletion of 8p21. NKX3.1 was found to have a polymorphism at nucleotide 154 in codon 52 that resulted in a CGC-->TGC sequence change and an Arg-->Cys amino acid alteration (R52C). This polymorphism was present in 20% of DNA samples. If NKX3.1 is a target of the 8p21 LOH, it is not via disruption of the coding region of the gene. 相似文献