全文获取类型
收费全文 | 1322篇 |
免费 | 24篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 59篇 |
综合类 | 1篇 |
化学工业 | 335篇 |
金属工艺 | 56篇 |
机械仪表 | 26篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 32篇 |
轻工业 | 177篇 |
水利工程 | 6篇 |
无线电 | 85篇 |
一般工业技术 | 188篇 |
冶金工业 | 228篇 |
原子能技术 | 5篇 |
自动化技术 | 91篇 |
出版年
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 32篇 |
2014年 | 22篇 |
2013年 | 46篇 |
2012年 | 40篇 |
2011年 | 62篇 |
2010年 | 35篇 |
2009年 | 44篇 |
2008年 | 43篇 |
2007年 | 43篇 |
2006年 | 37篇 |
2005年 | 41篇 |
2004年 | 48篇 |
2003年 | 20篇 |
2002年 | 30篇 |
2001年 | 20篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 49篇 |
1997年 | 39篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 26篇 |
1993年 | 27篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 24篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 20篇 |
1976年 | 24篇 |
1974年 | 13篇 |
1972年 | 9篇 |
1970年 | 8篇 |
1968年 | 11篇 |
1926年 | 7篇 |
排序方式: 共有1349条查询结果,搜索用时 15 毫秒
81.
Impact of the Nanoscale Gap Morphology on the Plasmon Coupling in Asymmetric Nanoparticle Dimer Antennas 下载免费PDF全文
Paul S. Popp Janning F. Herrmann Eva‐Corinna Fritz Bart Jan Ravoo Christiane Höppener 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(12):1667-1675
Coupling of plasmon resonances in metallic gap antennas is of interest for a wide range of applications due to the highly localized strong electric fields supported by these structures, and their high sensitivity to alterations of their structure, geometry, and environment. Morphological alterations of asymmetric nanoparticle dimer antennas with (sub)‐nanometer size gaps are assigned to changes of their optical response in correlative dark‐field spectroscopy and high‐resolution transmission electron microscopy (HR‐TEM) investigations. This multimodal approach to investigate individual dimer structures clearly demonstrates that the coupling of the plasmon modes, in addition to well‐known parameters such as the particle geometry and the gap size, is also affected by the relative alignment of both nanoparticles. The investigations corroborate that the alignment of the gap forming facets, and with that the gap area, is crucial for their scattering properties. The impact of a flat versus a rounded gap structure on the optical properties of equivalent dimers becomes stronger with decreasing gap size. These results hint at a higher confinement of the electric field in the gap and possibly a different onset of quantum transport effects for flat and rounded gap antennas in corresponding structures for very narrow gaps. 相似文献
82.
Surgical instruments have to meet strict requirements on functionality and stable performance. The functional properties of
scalpels, for example, are mainly dependent on a precise cutting edge geometry and high blade sharpness. To achieve a reliable
production of scalpels, it is necessary to establish a holistic understanding of the process chain as well as the interactions
of all machining processes. An innovative zirconium oxide offers high toughness and high wear resistance, leading to its use
in ophthalmic scalpels. A cooperative project has been conducted by two universities and two industrial partners, funded by
the German Federal Ministry of Economics and Technology (BMWi).The project focuses particularly on the grinding process as
a controlling factor for the scalpel’s functionality and sharpness. The complex process chain with various interactions of
kinematics, vibrations and tool micro-topography was developed for high reliability and efficiency. The performance of in-machine
dressing of diamond wheels with diamond form rollers was decisive for scalpel quality. 相似文献
83.
The development of methods facilitating the detection of cyanobacterial blooms in drinking water reservoirs at an early stage is of great importance. Fluorescence spectroscopy could meet these requirements. The study contains the examination of possible correlations between the different maxima of a fluorescence excitation-emission matrix and the amount of produced and excreted toxins of a lab culture of Microcystis aeruginosa at different stages of growth. Various fluorescence signals (protein-like and humic-like substances, pigments) are suited for an estimation of cell density and actual intra- and extracellular toxin concentration. One signal at 315 nm/396 nm presumably originating from protein-like substances might be useful as a tool for the prediction of increasing cyanobacterial toxin concentrations. As the measurement of fluorescence matrices is still time consuming, synchronous scans with Δλ = 80 nm were tested as a potential alternative. They accurately depict the course of protein-like and humic-like fluorescence during the different stages of growth although especially the latter one is not captured at its maximum. However, due to insufficient separation of chlorophyll a and phycocyanin, the image of the matrix maxima by synchronous scans with Δλ = 80 nm can only be used with minor restrictions. Nevertheless, fluorescence spectroscopy seems to be a powerful tool for the evaluation of cyanobacterial blooms. 相似文献
84.
Helfried Näfe Ruhul Amin Fritz Aldinger 《Journal of the American Ceramic Society》2007,90(10):3224-3226
The literature about the thermodynamic properties of NaNbO3 and Na3 NbO4 has mainly been governed by estimations. The only exceptions are two current calorimetric investigations on the standard enthalpy of formation of NaNbO3 and, in addition, an old and inappropriately evaluated study on the carbon dioxide equilibrium gas pressure over the phase mixture NaNbO3 /Na3 NbO4 /Na2 CO3 . Upon reevaluating the latter results, first experimentally proven data on the difference of the Gibbs-free energies have been obtained (715°–822°C): 相似文献
85.
M. Pfeiffer A. Beyer B. Plnnigs A. Nollau T. Fritz K. Leo D. Schlettwein S. Hiller D. Whrle 《Solar Energy Materials & Solar Cells》2000,63(1):83
We present a systematic study on doping of vanadyl- and zinc-pathalocyanine by a fully fluorinated form of tetracyano-quinodimethane as an example of controlled doping of thin organic films by cosublimation of matrix and dopant. The films are characterized in situ by temperature dependent Seebeck and conductivity measurements. We observe a drastic increase of conductivity and a corresponding shift of the Fermi level towards the valence states with increasing dopant concentration. We thus conclude that doping has the potential of both reducing the series resistance and increasing the photovoltage of organic solar cells. As a first step to exploit this potential, we present two different ways of preparing diodes with rectification ratios in excess of 104 using doped phthalocyanines. By adding an undoped interlayer between the contact and the doped layer, we have produced diodes which work already in the strict absence of oxygen and are stable in air. To increase the efficiency of charge carrier generation in photovoltaic cells, we need to use photoactive donor–acceptor-heterojunctions. We present here first examples of pn- and pin-type heterojunctions combining p-doped and nominally undoped layers. 相似文献
86.
In psychological measurement it is important to determine when a particular examinee's test or scale score provides an invalid measure of the trait or attitude being assessed. In this article we present several quantitative indices that have been found to effectively identify some types of inappropriate scores. These measures, termed appropriateness indices, are all derived from item response theory. They are computed directly from the item responses that are combined to form the test or scale of interest; information from other scales or tests is not needed. A decision-theoretic approach to the use of appropriateness indices in selection decisions and theoretical research is introduced. An example is then presented to illustrate how researchers can use appropriateness indices. Finally, we discuss policy options that are available for dealing with individuals who are identified as having inappropriate scores. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
A.C. Zambroni de Souza Fritz W. Mohn Isabella F. Borges Tito R. Ocariz 《Electric Power Systems Research》2011,81(7):1491-1498
This paper investigates the use of the QV and PV curves in the planning scenario, when some system reinforcements and contingency screening are analyzed. The idea is to employ the continuation method to obtain the system load margin and the QV curve to calculate the reactive power reserve associated with each bus. Combining these approaches enables one to identify the system critical area, the actual operating conditions, the most severe contingencies and the most important reinforcements. The methodology proposed may provide important signals to system planners, since the planning is focused under the voltage security point of view. The ideas are tested with the help of some academic systems and two real (a Brazilians and a Paraguayan) systems with all the system limits considered. 相似文献
88.
89.
H. Kortum J. Ulsamer G. Vogelpohl Ude W. Fritz Max Jakob 《Forschung im Ingenieurwesen》1933,4(3):150-156
Ohne Zusammenfassung 相似文献
90.