全文获取类型
收费全文 | 1815篇 |
免费 | 80篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 13篇 |
化学工业 | 517篇 |
金属工艺 | 27篇 |
机械仪表 | 26篇 |
建筑科学 | 124篇 |
矿业工程 | 4篇 |
能源动力 | 41篇 |
轻工业 | 173篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 97篇 |
一般工业技术 | 327篇 |
冶金工业 | 144篇 |
原子能技术 | 10篇 |
自动化技术 | 366篇 |
出版年
2023年 | 17篇 |
2022年 | 21篇 |
2021年 | 34篇 |
2020年 | 40篇 |
2019年 | 34篇 |
2018年 | 45篇 |
2017年 | 18篇 |
2016年 | 45篇 |
2015年 | 31篇 |
2014年 | 77篇 |
2013年 | 96篇 |
2012年 | 89篇 |
2011年 | 157篇 |
2010年 | 92篇 |
2009年 | 77篇 |
2008年 | 91篇 |
2007年 | 87篇 |
2006年 | 74篇 |
2005年 | 47篇 |
2004年 | 59篇 |
2003年 | 42篇 |
2002年 | 52篇 |
2001年 | 31篇 |
2000年 | 32篇 |
1999年 | 39篇 |
1998年 | 60篇 |
1997年 | 51篇 |
1996年 | 24篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1992年 | 23篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1959年 | 15篇 |
1958年 | 7篇 |
1957年 | 10篇 |
1948年 | 7篇 |
排序方式: 共有1896条查询结果,搜索用时 0 毫秒
1.
2.
Dynamic complexity investigates the required effort to maintain knowledge about a property of a structure under changing operations.
This article introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the
basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFL-complete problem D2LREACH(acyclic) can be maintained with first-order updates. 相似文献
3.
Das Autobahnmautgesetz zeichnet sich durch eine strenge Zweckbindung für die Mautdaten aus. Diese dürfen ausschlie?lich für
die Zwecke des Mautgesetzes erhoben und verarbeitet werden. Diese Vorgabe hat das LG Magdeburg in einem Beschluss richtungsweisend
auch für die Verbindungsdaten der GSM-Kommunikation best?tigt. 相似文献
4.
Volker Mayer 《Dynamical Systems: An International Journal》2007,22(2):169-178
We prove several essential fractal properties, such as positivity, finiteness or local infinity, of Hausdorff and packing measures of radial Julia sets for large subclasses of entire and meromorphic functions considered in our previous work: çGeometric thermodynamical formalism and real analyticity for meromorphic functions of finite order'. Most of the results proven are shown to be optimal. 相似文献
5.
6.
The application of municipal solid waste (MSW) compost increases both the trace metal loading and the organic matter in the soil. To characterize the quality and metal-binding capacity of the compost OM, we extracted humic acid (HA) and fulvic acid (FA) from mature MSW compost and analyzed them for elemental composition, acid-titratable functional groups, total metal content, and structural components (by 13C NMR). HA constituted 67% of all extracted humic substances and differed significantly from HAs of cultivated lands: The compost HA exhibited smaller molecular size, a higher N content, and lower aromaticity due to large amounts of saturated aliphatic components. Metal complexation studies of the extracted HA and FA were performed by equilibrium dialysis titration. The complexing capacity (CC) was highest for Cu: CCHA = 3357 and CCFA = 5221 μmol Cu g−1 of dissolved organic carbon (DOC) at pH 5. Zn and Cd were bound (at pH 7) in smaller concentrations: CCHA(Zn) = 2167, CCFA(Zn) = 2809, CCHA(Cd) = 2386, and CCFA(Cd) = 2468 μmol metal g−1 of DOC. Stability constants for binding on the strongest sites (pKint) were determined as pKintHA = 6.6 and pKintFA = 7.3 for Cu at pH 5; and pKintHA = 8.0 and pKintFA = 6.4 for Cd at pH 7. Since these measured parameters fall within the ranges of values obtained for soil humic substances, we conclude that in soils with little organic matter, compost addition will significantly increase the amount of highly reactive organic complexing agents for trace metals in the soil. 相似文献
7.
The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, 1H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt. 相似文献
8.
9.
Reliability aspects of microsensors and micromechatronic actuators for automotive applications 总被引:1,自引:0,他引:1
In modern cars microsensors and micromechatronic actuators play an essential and still increasingly important role as the interface between the vehicle with its complex functions of motor management, chassis systems, safety as well as comfort and convenience on the one hand and the respective electronic control units on the other hand. They have to fulfill their task in a harsh environment over the entire lifetime of an automobile. Therefore reliability aspects have moved more and more into the focus of engineering and research activities in microsystem technology. A methodical procedure is described that allows reliability issues to be approached efficiently. The implementation of the methodology is illustrated with real-life examples of reliability aspects of hot film mass air flow sensors, inertial sensors as well as piezoelectric actuators. 相似文献
10.
Hahlweg Kurt; Markman Howard J.; Thurmaier Franz; Engl Jochen; Eckert Volker 《Canadian Metallurgical Quarterly》1998,12(4):543
This article reports on the development and long-term evaluation of a marital distress prevention program for German couples, the Ein Partnerschaftliches Lernprogramm (EPL, A Couple's Learning Program). The EPL is a 6-session program designed to teach couples effective communication and problem-solving skills. In the current article, the EPL is evaluated in a prospective, quasi-experimental, controlled trial. The results of the 3-year follow-up are reported, contrasting 55 EPL couples with a control group of 17 couples. Significant differences emerged with regard to the couples' dissolution rates, relationship satisfaction, and positive and negative communication behavior favoring the EPL couples. These results demonstrate the utility of the EPL program in assisting happy couples who are preparing for marriage. The implications of the findings for prevention research and for the dissemination of prevention programs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献