全文获取类型
收费全文 | 7408篇 |
免费 | 538篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 109篇 |
综合类 | 9篇 |
化学工业 | 2131篇 |
金属工艺 | 83篇 |
机械仪表 | 169篇 |
建筑科学 | 262篇 |
矿业工程 | 10篇 |
能源动力 | 324篇 |
轻工业 | 1326篇 |
水利工程 | 38篇 |
石油天然气 | 42篇 |
无线电 | 523篇 |
一般工业技术 | 1144篇 |
冶金工业 | 207篇 |
原子能技术 | 61篇 |
自动化技术 | 1518篇 |
出版年
2024年 | 8篇 |
2023年 | 79篇 |
2022年 | 318篇 |
2021年 | 333篇 |
2020年 | 218篇 |
2019年 | 225篇 |
2018年 | 261篇 |
2017年 | 290篇 |
2016年 | 330篇 |
2015年 | 230篇 |
2014年 | 383篇 |
2013年 | 607篇 |
2012年 | 499篇 |
2011年 | 598篇 |
2010年 | 466篇 |
2009年 | 466篇 |
2008年 | 437篇 |
2007年 | 369篇 |
2006年 | 284篇 |
2005年 | 219篇 |
2004年 | 190篇 |
2003年 | 168篇 |
2002年 | 184篇 |
2001年 | 100篇 |
2000年 | 74篇 |
1999年 | 77篇 |
1998年 | 79篇 |
1997年 | 50篇 |
1996年 | 45篇 |
1995年 | 51篇 |
1994年 | 35篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1975年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有7956条查询结果,搜索用时 15 毫秒
891.
In der vorliegenden Arbeit wird über Wärmebehandlungen zur Lösung von Chromcarbiden als Vorbeugungsmaßnahme zur Verhinderung der interkristallinen Korrosion berichtet. Vor dem Hintergrund einer möglichen Energieeinsparung wurde ein Temperaturbereich gewählt, der knapp unter dem der industriellen Praxis von 1050°C liegt. Gleichzeitig werden die elektrochemischen Untersuchungsmethoden der Anfälligkeit für interkristalline Korrosion den genormten Methoden gegenübergestellt, um die Anwendungsmöglichkeiten und ihre Verläßlichkeit zu bewerten und einzustufen. Die Ergebnisse zeigen, daß dem Kornzerfall durch Wärmebehandlungen bei 950°C entgegengewirkt werden kann. In vielen Fällen wird diese Temperatur, die rund 100°C unter der in der Industrie angewandten liegt, eine bedeutende Energieeinsparung beinhalten. Allerdings ist diese niedrige Lösungsglühtemperatur nur für molybdänfreie Stähle anzuwenden; für molybdänhaltige, nichtrostende Stähle ist bei Gehalten über rd. 2,5 % Mo eine höhere Lösungsglühtemperatur nach wie vor erforderlich. Das elektrochemische E.P.R.-Verfahren ist eng mit den Versuchen A, C und E der Norm ASTM-A-262 verknüpft. Diese Tatsache wie auch die Einfachheit, Schnelligkeit und der zerstörungsfreie Charakter führen die Autoren zu der Überzeugung, daß die elektrochemische Methode ein idealer Test zur Ermittlung der Anfälligkeit für interkristalline Korrosion ist. 相似文献
892.
Claudio de A. Loural Romulo A. Zanco Filho Antonio Carlos G. Bordeaux Rego Rogrio C. de Oliveira 《Telematics and Informatics》2006,23(4):294-315
Brazilian telecommunications sector has undergone important modifications in the last 40 years. From a badly structured system of municipal level operators in 1960, with barely one million fixed lines to a large, nation-wide system with about 50 million fixed plus another 75 million mobile lines in 2005. This work paper reviews the institutional framework of telecommunications industrial and technological policy in Brazil in the last four decades, its results and present situation. Infrastructure and services modernisation and expansion process that happened in early 1970s were carried out at the expense of massive import of products and technology. A government strategy was, then, devised to stimulate local industrial and technological development in telecommunications, under the general guidelines of import substitution policy. Essential to this strategy was the creation of an innovation system around TELEBRÁS Research and Development Centre. This technological development model was successful while a protectionist economic policy existed. When economic and political circumstances could not anymore sustain an import substitution approach, in the 1990-decade, the model fell apart and has not been replaced by any other sectorial policy. A critical assessment is carried out, analysing the adopted actions in face of the digital technology maturing process that occurred in meantime. 相似文献
893.
894.
The abstract (or semantic) syntax of the Pascal language is identified, and a linear representation for the trees so formed within the framework of the concrete syntax for that language is imposed. The indentation scheme so formed, augmented with a small number of pragmatic considerations, is compared with several previously proposed formatting schemes for Pascal and an example of the use of this new method is given. 相似文献
895.
Jesús García-Cantalejo Victoriano Baladrn Pedro F. Esteban M. Angeles Santos Germn Bou Miguel A. Remacha Jos L. Revuelta Juan P. G. Ballesta Antonio Jimnez Francisco Del Rey 《Yeast (Chichester, England)》1994,10(2):231-245
We report the sequence of an 18,002 bp DNA fragment from the right arm of Saccharomyces cerevisiae chromosome XI. This segment contains nine complete open reading frames (ORFs), YKR401 to YKR409, and part of another ORF, YKR400, covering altogether 87·2% of the entire sequence. One of them, YKR400, encodes an NAD-dependent 5,10-methylene-tetrahydrofolate dehydrogenase. YKR404, YKR405 and YKR406 correspond to the previously characterized HBS1, MRP-L20 and PRP16 genes, coding for a translation elongation factor, a mitochondrial ribosomal protein and an ATP-binding protein, respectively. The putative product of YKR407 contains the zinc-binding region signature of neutral zinc metallopeptidases. The five other ORFs do not show significant homology to any known protein. The sequence data reported here have been assigned EMBL accession number Z27116. 相似文献
896.
RJ Ippolito 《Canadian Metallurgical Quarterly》1993,57(7):451-455
A variation of Mirizzi's syndrome is described in which common hepatic duct obstruction occurs due to extrinsic compression by an acutely inflamed acalculous gallbladder abutting the common hepatic duct. This case suggests that extrinsic compression and inflammation in the absence of stones can result in complete obstruction of extrahepatic biliary flow. 相似文献
897.
898.
The supermolecular structure of crystallised molecular weight fractions of poly(hexa-methylene oxide), covering the molecular weight range (M) 4.5. × 103 to 8. 5 × 104, was studied by polarised light microscopy and small angle light scattering. Different forms were observed as a function of molecular weight and crystallisation temperatures. Perfect spherulites are formed after rapid crystallisation, and these forms deteriorate as both the molecular weight and crystallisation temperature increase. The morphology in the isothermal crystallisation region corresponds to an intermediate state which represents a transition from spherulites to hedrites. 相似文献
899.
This paper describes the theoretical background and the process of obtaining maximum hop lengths and minimum fading margins (if the terminal or repeater locations are fixed) in any region of the world and gives a set of curves providing these characteristics for 1 km with availability of 99.7 % of the time (per 2 500 km), for a given frequency and polarization. Correction factors for other availabilities are also given. 相似文献
900.
Antonio Gonzalez 《国际智能系统杂志》1995,10(4):357-371
A step-by-step methodology for learning fuzzy rules is presented. This methodology tries to be general enough to give a framework within which different learning methods in an environment of uncertainty and imprecision could be developed. the final product will always be an uncertainty distribution on the different rules representing the behavior of the system. the particular uncertainty distribution depends on the concrete functions selected in each step of the process. the learning approach can also be considered as a way to construct uncertainty measures from data. © 1995 John Wiley & Sons, Inc. 相似文献