全文获取类型
收费全文 | 728篇 |
免费 | 9篇 |
专业分类
电工技术 | 8篇 |
综合类 | 4篇 |
化学工业 | 147篇 |
金属工艺 | 11篇 |
机械仪表 | 14篇 |
建筑科学 | 53篇 |
矿业工程 | 29篇 |
能源动力 | 16篇 |
轻工业 | 146篇 |
水利工程 | 8篇 |
无线电 | 38篇 |
一般工业技术 | 71篇 |
冶金工业 | 128篇 |
原子能技术 | 5篇 |
自动化技术 | 59篇 |
出版年
2021年 | 9篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 46篇 |
2012年 | 16篇 |
2011年 | 43篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 21篇 |
2007年 | 32篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 21篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1977年 | 20篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1971年 | 10篇 |
1970年 | 9篇 |
1966年 | 4篇 |
1962年 | 8篇 |
1959年 | 4篇 |
1958年 | 5篇 |
排序方式: 共有737条查询结果,搜索用时 15 毫秒
121.
Magnetic polystyrene–palygorskite nanocomposite obtained by heterogeneous phase polymerization to apply in the treatment of oily waters 下载免费PDF全文
Antonieta Middea Luciana Spinelli Fernando Gomes de Souza Junior Reiner Neumann Thais Fernandes Fabiano Richard Leite Faulstich Otavio Gomes 《应用聚合物科学杂志》2018,135(15)
Water contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe3O4‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46162. 相似文献
122.
Struckmeier J Wahl R Leuschner M Nunes J Janovjak H Geisler U Hofmann G Jähnke T Müller DJ 《Nanotechnology》2008,19(38):384020
With the introduction of single-molecule force spectroscopy (SMFS) it has become possible to directly access the interactions of various molecular systems. A bottleneck in conventional SMFS is collecting the large amount of data required for statistically meaningful analysis. Currently, atomic force microscopy (AFM)-based SMFS requires the user to tediously 'fish' for single molecules. In addition, most experimental and environmental conditions must be manually adjusted. Here, we developed a fully automated single-molecule force spectroscope. The instrument is able to perform SMFS while monitoring and regulating experimental conditions such as buffer composition and temperature. Cantilever alignment and calibration can also be automatically performed during experiments. This, combined with in-line data analysis, enables the instrument, once set up, to perform complete SMFS experiments autonomously. 相似文献
123.
Heikkinen V Lenz R Jetsu T Parkkinen J Hauta-Kasari M Jääskeläinen T 《Journal of the Optical Society of America. A, Optics, image science, and vision》2008,25(10):2444-2458
The problem of estimating spectral reflectances from the responses of a digital camera has received considerable attention recently. This problem can be cast as a regularized regression problem or as a statistical inversion problem. We discuss some previously suggested estimation methods based on critically undersampled RGB measurements and describe some relations between them. We concentrate mainly on those models that are using a priori information in the form of high-resolution measurements. We use the "kernel machine" framework in our evaluations and concentrate on the use of multiple illuminations and on the investigation of the performance of global and locally adapted estimation methods. We also introduce a nonlinear transformation of reflectance values to ensure that the estimated reflection spectra fulfill physically motivated boundary conditions. The reported experimental results are derived from measured and simulated camera responses from the Munsell Matte, NCS, and Pantone data sets. 相似文献
124.
Improving knowledge on the film forming behavior of greases is essential to be able to develop efficient greases. This article examines how operating conditions (e.g., temperature, lubrication condition [fully flooded/starved]) and base oil viscosity influence the film forming properties of greases by comparing the behavior of two lithium-based greases and their respective base oils in rolling point contact. It is found that the onset and degree of starvation is controlled by speed (u) × viscosity (ν)/load (W) factor (uν/W) and temperature and that low uν/W values promote entrainment of thickener into contact. Thus, grease with low base oil viscosity shows significant thickener entrainment in the low speed region compared to the one with high base oil viscosity, which leads to the formation of thickener-rich viscous material during extended running with the low base oil viscosity grease. The results suggest that the shape of the film thickness versus speed curve is viscosity and uν/W range dependent. Furthermore, for the test conditions used in this study, grease-lubricated contacts appear to shift from the initial fully flooded condition to starved condition over a prolonged running of 2 h. The results from this study concur with those reported in the literature that fully flooded oil elastohydrodynamic lubrication (EHL) theory or film thickness cannot be directly applied or taken as a guideline in grease-lubricated contacts. 相似文献
125.
The making of a tensegrity tower. This contribution describes the making of a tensegrity tower, which is based on a triangular pattern that is rotated by 30° at each segment (twist element). The realization is based on the highest possible production accuracy, especially for the cables, and a consistent concept for tolerance compensation. A major subject is the pre‐stressing of the cables that turned out to be possible by moving the three base points of each segment inwards simultaneously by means of a horizontal frame with three jacks, each with a capacity of 100 tons. The tower was pre‐assembled from the twist elements in two parts. The upper part was finally lifted on top of the lower part by means of a 170 t mobile crane. 相似文献
126.
Electron beam curing of the system cycloaliphatic diepoxide‐epoxidized natural rubber‐glycidyl methacrylate containing a cationic initiator was carried out. Storage modulus, glass transition temperature and pendulum hardness were measured as function of EB dose, photoinitiator concentration, content of epoxidized natural rubber, post cure temperature and post cure time. At electron beam doses larger than 100 kGy a highly cross‐linked polymer network is generated which shows a two phase morphology. Microscale elastomeric domains are incorporated into a continuous epoxy resin phase. Dynamical mechanical analysis and pendulum hardness measurement show that an increase of the ENR ratio leads to a more elastic polymer network. Post curing results in increased glass transition temperatures. This EB cured polymer system is believed to provide both toughness and favorable viscoelastic properties to be used as component of EB curable composites. 相似文献
127.
128.
Tanja Smolka Reiner Sustmann Roland Boese 《Advanced Synthesis \u0026amp; Catalysis》1999,341(4):378-383
A hydrogen-bonded network in a 1:1 cocrystal of phenazine and meso-1,2-diphenyl-1,2-ethandiol places phenazine and diol in such a way that a thermally reversible photochromism is produced. The structure of the cocrystal is determined by X-ray crystallography. Thermally reversible changes in the UV/Vis and IR spectrum on irradiation, in combination with the generation of paramagnetism (ESR) lead to the interpretation that a light induced electron transfer between two phenazine molecules is followed by a double proton transfer to the nitrogen atoms of the radical anion of phenazine. 相似文献
129.
Frank Swiaczny Reiner Schulz 《Journal für Verbraucherschutz und Lebensmittelsicherheit》2009,33(2):136-144
Das globale Wachstum der Weltbev?lkerung und die Folgen der zunehmenden Verst?dterung lassen angesichts der weltweiten Verbreitung
von Armut und Unterern?hrung die Frage nach den künftigen Grenzen der agraren Tragf?higkeit der Erde aufkommen. Das von den
UN-Modellrechnungen, die in der vorliegenden Ver?ffentlichung im überblick vorgestellt werden, vorausberechnete weitere Bev?lkerungswachstum
und der Fl?chenverbrauch durch die zunehmende Verst?dterung und Industrialisierung lassen die pro Kopf der Weltbev?lkerung
für die Nahrungsmittelproduktion verfügbare Anbaufl?che bis zur Jahrhundertmitte deutlich schrumpfen. Hinzu kommen die gegenw?rtig
nur schwer absehbaren Auswirkungen von Bodendegradation und Klimawandel auf die Produktion von Nahrungsmitteln. Ob es hinsichtlich
der Tragf?higkeit eine mehr als theoretische Grenze für die Zahl an Menschen gibt, die auf der Erde unter optimalen Bedingungen
ern?hrt werden k?nnen, ist umstritten. Trotz eines Rückgangs an agrarer Nutzfl?che pro Kopf geht die FAO in ihrer Prognose
aktuell davon aus, dass das globale Angebot an Kalorien pro Kopf der Weltbev?lkerung bis 2030 gesteigert und die Anzahl von
Unterern?hrung betroffener Menschen deutlich reduziert werden kann. Unter dem Aspekt der Nachhaltigkeit ist die Produktion
von Nahrungsmitteln aber vor allem im Kontext der aktuellen Produktionsbedingungen und der Konkurrenz zu anderen Konsumbereichen
zu betrachten und diesbezüglich ist nach Berechnungen des Global Footprint Networks, die hier herangezogen werden, bereits
in den 1980er Jahren die Biokapazit?t der Erde für eine nachhaltige Entwicklung überschritten worden. Setzt sich die derzeitige
Entwicklung fort, wird unter Einbeziehung des von der UN angenommenen globalen Bev?lkerungswachstums die Biokapazit?t der
Erde bis 2050 um mehr als das Doppelte überschritten werden.
Eingegangen: 9. Januar 2009; angenommen: 16. Januar 2009
http://www.bib-demographie.de 相似文献
130.