全文获取类型
收费全文 | 1551篇 |
免费 | 76篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 22篇 |
综合类 | 13篇 |
化学工业 | 482篇 |
金属工艺 | 22篇 |
机械仪表 | 21篇 |
建筑科学 | 119篇 |
矿业工程 | 4篇 |
能源动力 | 41篇 |
轻工业 | 107篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 90篇 |
一般工业技术 | 311篇 |
冶金工业 | 70篇 |
原子能技术 | 9篇 |
自动化技术 | 312篇 |
出版年
2023年 | 18篇 |
2022年 | 15篇 |
2021年 | 35篇 |
2020年 | 37篇 |
2019年 | 33篇 |
2018年 | 42篇 |
2017年 | 18篇 |
2016年 | 42篇 |
2015年 | 31篇 |
2014年 | 72篇 |
2013年 | 91篇 |
2012年 | 85篇 |
2011年 | 143篇 |
2010年 | 89篇 |
2009年 | 73篇 |
2008年 | 81篇 |
2007年 | 79篇 |
2006年 | 69篇 |
2005年 | 43篇 |
2004年 | 49篇 |
2003年 | 39篇 |
2002年 | 52篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 32篇 |
1998年 | 39篇 |
1997年 | 36篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1970年 | 4篇 |
1960年 | 4篇 |
排序方式: 共有1628条查询结果,搜索用时 46 毫秒
161.
Ulf Stalmach Heiner Detert Herbert Meier Volker Gebhardt Dietrich Haarer Andreas Bacher Hans-Werner Schmidt 《Optical Materials》1998,9(1-4):77-81
The preparation of LEDs with poly( p-phenylenevinylene) (PPV) as emitting material is well established. However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-1,4-phenylenevinylene)s with up to 11 repeating units. This series covers the spectrum from monomer to polymer. The influence on the EL can be investigated by preparing single layer LEDs using vapor deposition or spincoating of the oligomers in a polystyrene (PS) matrix. The comparison of photoluminescence (PL)- and EL-spectra shows that the photophysical properties of the oligomers are strongly altered by aggregation phenomena. 相似文献
162.
The basis of mapped finite element methods are reference elements where the components of a local finite element are defined. The local finite element on an arbitrary mesh cell will be given by a map from the reference mesh cell. This paper describes some concepts of the implementation of mapped finite element methods. From the definition of mapped finite elements, only local degrees of freedom are available. These local degrees of freedom have to be assigned to the global degrees of freedom which define the finite element space. We will present an algorithm which computes this assignment. The second part of the paper shows examples of algorithms which are implemented with the help of mapped finite elements. In particular, we explain how the evaluation of integrals and the transfer between arbitrary finite element spaces can be implemented easily and computed efficiently. 相似文献
163.
164.
165.
166.
167.
Zusammenfassung Personenbezogene Daten müssen gel?scht werden, wenn sie für die weiteren Gesch?ftprozesse der Unternehmen nicht mehr erforderlich
sind und auch gesetzliche Aufbewahrungsfristen der L?schung nicht im Wege stehen. In der Praxis wird dieser L?schpflicht allerdings
nur zurückhaltend Rechnung getragen. Der Beitrag begründet das Erfordernis konsequenten L?schens und will dazu motivieren,
den gesetzlich vorgegebenen L?schpflichten durch ein L?schkonzept Rechnung zu tragen.
Reinhard Fraenkel ist nach verschiedenen T?tigkeiten in der Industrie seit 1994 als Rechtsanwalt in Gütersloh t?tig. Zu seinen
Arbeitsschwerpunkten z?hlt das Datenschutzrecht. Seit August 2004 ist er externer Datenschutzbeauftragter der Toll Collect
GmbH.
Dr. Volker Hammer ist Consultant der Secorvo GmbH. Seit Mitte 2003 unterstützt er die Toll Collect GmbH in verschiedenen Datenschutz-Projekten.
Weitere Arbeitsschwerpunkte sind Public Key Infrastrukturen und kritische IT-Infrastrukturen 相似文献
168.
David Rafaja Milan Dopita Magsud Masimov Volker Klemm Nina Wendt Walter Lengauer 《International Journal of Refractory Metals and Hard Materials》2008,26(3):263-275
Combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used for investigation of local composition gradients in the hard-phases of cermets. XRD revealed distribution of lattice parameters in hard-phase grains, from which the composition gradients in the hard-phases were estimated using an appropriate microstructure model. This microstructure model was build with the aid of SEM micrographs, which were taken with back-scattered electrons (BSE) and completed by the registration of the electron back-scatter diffraction (EBSD) patterns and characteristic X-ray spectra. SEM/BSE yielded the first information about the spatial distribution of elements in individual hard-phase grains, SEM/EBSD about the morphology, the size and the size distribution of these grains. The final interpretation of the distribution of lattice parameters, which was obtained from the X-ray line profile analysis, was done with the aid of the local elemental analysis that was performed using SEM with the energy dispersive analysis of the characteristic X-ray spectra (EDX) and the known dependence of the lattice parameters on concentration. 相似文献
169.
Kerstin Hannemann Volker Puchta Ernst Simon Herta Ziegler Gunter Ziegler Gerhard Spiteller 《Lipids》1989,24(4):296-298
The observation that F-acids (1) occur in rat chow initiated a search for F-acids in human diet. We observed that the amount
of F-acids with a pentyl side chain in α-position taken up with a one-day diet correlates well with the amount of excreted
degradation products, the pentyl urofuran acids (2), (3) and (4). Therefore it can be concluded that F-acids with a pentyl
side chain are not produced in the human body but are introduced through the diet. The origin of F-acids carrying an α-propyl
side chain is less clear. The amount of propyl-urofuran acids (2) and (3) excreted in urine was found in one case out of three
to be five times higher than the amount of F-acids carrying a propyl group in α-position taken up by the diet. Therefore,
it can presently not be excluded that a portion of the propyl F-acids is produced by the body.
F-acids found in human food are mainly introduced into the body by vegetables and fruits. F-acids were found also in birch
leaves in considerable amounts, as well as in grasses, dandelion and clover leaves. Thus, we can conclude that F-acids are
common constituents of plants. 相似文献
170.
Ralph Schöpke Roland Koch Sylke Mangold Volker Preuß Ralf Regel Angelika Striemann 《Grundwasser》2006,11(4):270-275
Sulfate-reducing processes were initiated in an aquifer with AMD-laden groundwater orthogonally to the located main groundwater flow direction. Groundwater was intermittently circulated between two wells. Substrate (methanol) and nutrients were added to this flow. After one year a sulphate-reducing reactor was formed in the aquifer, that precipitated FeS and decreased the acidity. These effects could still be observed one year after cessation of substrate amendment. 相似文献