全文获取类型
收费全文 | 2330篇 |
免费 | 205篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 38篇 |
综合类 | 8篇 |
化学工业 | 738篇 |
金属工艺 | 35篇 |
机械仪表 | 43篇 |
建筑科学 | 130篇 |
矿业工程 | 35篇 |
能源动力 | 55篇 |
轻工业 | 254篇 |
水利工程 | 13篇 |
无线电 | 171篇 |
一般工业技术 | 473篇 |
冶金工业 | 135篇 |
原子能技术 | 10篇 |
自动化技术 | 399篇 |
出版年
2023年 | 45篇 |
2022年 | 71篇 |
2021年 | 113篇 |
2020年 | 79篇 |
2019年 | 68篇 |
2018年 | 94篇 |
2017年 | 92篇 |
2016年 | 114篇 |
2015年 | 112篇 |
2014年 | 144篇 |
2013年 | 155篇 |
2012年 | 148篇 |
2011年 | 170篇 |
2010年 | 97篇 |
2009年 | 117篇 |
2008年 | 114篇 |
2007年 | 96篇 |
2006年 | 74篇 |
2005年 | 74篇 |
2004年 | 56篇 |
2003年 | 50篇 |
2002年 | 39篇 |
2001年 | 22篇 |
2000年 | 25篇 |
1999年 | 23篇 |
1998年 | 31篇 |
1997年 | 27篇 |
1996年 | 26篇 |
1995年 | 27篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有2537条查询结果,搜索用时 15 毫秒
71.
Jan Penckwitt Robert van Geldern Burkard Hagspiel Birgit Packebusch Alexander Mahr Klaus Burkhardt Johannes A. C. Barth 《Grundwasser》2016,21(3):217-225
Infiltration of groundwater into sewer systems increases the costs for wastewater treatment plant operators. This study explores groundwater infiltration to urban sewer systems in the city of Nuremberg (Germany). Measurements of stable isotopes at the water works, storage tanks, groundwater, and the sewage network were carried out to define input end members for mass balance calculations. Only minor differences in oxygen stable isotopes (δ18OH2O) were found between most sewer and drinking water samples which ranged around (??9.5?±?0.1) ‰. One exception was water from a water works at Genderkingen that is situated about 80 km south of Nuremberg. Here, drinking water from bank filtrate of the Lech River had more negative δ18OH2O values of ??11.4?‰. This difference of 1.5?‰ revealed maximum possible groundwater contributions of 41?% by mass balance calculations. To obtain more accurate results, we suggest testing the use of deuterium-enriched water (D2O) added to the sewer system. 相似文献
72.
73.
Felix Schubert Steffen Wirth Friederike Zimmermann Johannes Heitmann Thomas Mikolajick 《Science and Technology of Advanced Materials》2016,17(1):239-243
Growth conditions have a tremendous impact on the unintentional background impurity concentration in gallium nitride (GaN) synthesized by molecular beam epitaxy and its resulting chemical and physical properties. In particular for oxygen identified as the dominant background impurity we demonstrate that under optimized growth stoichiometry the growth temperature is the key parameter to control its incorporation and that an increase by 55?°C leads to an oxygen reduction by one order of magnitude. Quantitatively this reduction and the resulting optical and electrical properties are analyzed by secondary ion mass spectroscopy, photoluminescence, capacitance versus voltage measurements, low temperature magneto-transport and parasitic current paths in lateral transistor test structures based on two-dimensional electron gases. At a growth temperature of 665?°C the residual charge carrier concentration is decreased to below 1015 cm?3, resulting in insulating behavior and thus making the material suitable for beyond state-of-the-art device applications. 相似文献
74.
Paul Johannes Helm 《International journal of molecular sciences》2012,13(10):12367-12382
The process of radiationless energy transfer from a chromophore in an excited electronic state (the “donor”) to another chromophore (an “acceptor”), in which the energy released by the donor effects an electronic transition, is known as “Förster Resonance Energy Transfer” (FRET). The rate of energy transfer is dependent on the sixth power of the distance between donor and acceptor. Determining FRET efficiencies is tantamount to measuring distances between molecules. A new method is proposed for determining FRET efficiencies rapidly, quantitatively, and non-destructively on ensembles containing donor acceptor pairs: at wavelengths suitable for mutually exclusive excitations of donors and acceptors, two laser beams are intensity-modulated in rectangular patterns at duty cycle ½ and frequencies f1 and f2 by electro-optic modulators. In an ensemble exposed to these laser beams, the donor excitation is modulated at f1, and the acceptor excitation, and therefore the degree of saturation of the excited electronic state of the acceptors, is modulated at f2. Since the ensemble contains donor acceptor pairs engaged in FRET, the released donor fluorescence is modulated not only at f1 but also at the beat frequency Δf: = |f1 − f2|. The depth of the latter modulation, detectable via a lock-in amplifier, quantitatively indicates the FRET efficiency. 相似文献
75.
A classical constitutive modeling-based Ansatz for the impact of thermal activation on the stress–strain response of metallic materials is compared with the state parameter-based Kocks–Mecking model. The predicted functional dependencies suggest that, in the first approach, only the dislocation storage mechanism is a thermally activated process, whereas, in the second approach, only the mechanism of dynamic recovery is. In contradiction to each of these individual approaches, our analysis and comparison with experimental evidence shows that thermal activation contributes both to dislocation generation and annihilation. 相似文献
76.
Forschung im Ingenieurwesen - Eine integrierte Fahrdynamikregelung für Straßenfahrzeuge ermittelt aus allen Komponenten der Bewegungsanforderung zur Umsetzung dieser geeignete... 相似文献
77.
Jürgen Goriupp MSC Andreas Rief Johannes Schenk 《BHM Berg- und Hüttenm?nnische Monatshefte》2012,157(8-9):340-344
The induction furnace test is one of the most common used refractory wear testing methods for MgO-C products. Due to the high oxidation rates in the ITO test setup and the significant changes in slag chemistry the test method sometimes gives results which cannot be compared to the field. For a general “Yes or No” decision this test is suitable for testing MgO-C refractories, determination of small differences in performance of MgO-C products, which is especially important for the development of new grades, is hardly possible. Due to that the application of a supplementary testing method was tested at the Chair of Metallurgy (Montanuniversitaet Leoben). 相似文献
78.
Peter T. Witte Peter H. Berben Susan Boland Evert H. Boymans Dieter Vogt John W. Geus Johannes G. Donkervoort 《Topics in Catalysis》2012,55(7-10):505-511
An innovative BASF catalyst manufacturing technology (NanoSelect?) is introduced which allows production of heterogeneous catalysts with excellent control over metal crystallite sizes. NanoSelect? technology enabled the development of Pd catalysts which are lead-free Lindlar catalyst replacements in alkyne-to-cis-alkene hydrogenations. NanoSelect? Pt catalysts showed excellent chemoselectivity in substituted nitro-arene hydrogenation reactions without build-up of hydroxylamine intermediates. All NanoSelect? produced catalysts show markedly higher activity per gram of metal leading to ten-fold less use of precious metal. 相似文献
79.
80.
Manufacturing companies face rising pressure due to increased competition. Traditionally, companies have merely concentrated on offering impeccable, cost-efficient products. Today, however, flexibility and on-time delivery are additional requirements to satisfy the customers. At the same time, disruptions in production, especially in low-volume assembly, still frequently occur, leading to economic losses and delayed customer deliveries. The approach proposed in this paper strives for improving the disruption situation in low-volume assemblies. A detailed disruption management methodology has been developed, aiming at realizing an efficient reduction of disruptions, while at the same time considering the specific characteristics of low-volume assembly. The methodology is supported by a catalog of pre-emptive measures. These measures are known to reduce the disruptions’ occurrence or to diminish their consequences. In general, the approach pursues the basic idea to implement particularly those measures, which have the best cost-benefit-ratio. Based on the analysis of the cost-benefit-ratio of each measure, the developed methodology aims at improving the disruption situation in assembly and thus providing a high on-time delivery rate. The usability of the methodology for the low-volume assembly context has been confirmed by assembly experts on the basis of an application of the methodology in an exemplary case study. 相似文献