全文获取类型
收费全文 | 262篇 |
免费 | 6篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 75篇 |
金属工艺 | 8篇 |
机械仪表 | 1篇 |
建筑科学 | 5篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 23篇 |
石油天然气 | 1篇 |
无线电 | 19篇 |
一般工业技术 | 29篇 |
冶金工业 | 51篇 |
自动化技术 | 42篇 |
出版年
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 16篇 |
1997年 | 14篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1940年 | 2篇 |
1903年 | 4篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
11.
Nadine Müller Sabine Ellinger Birgit Alteheld Gudrun Ulrich‐Merzenich Heiner K. Berthold Hans Vetter Peter Stehle 《Molecular nutrition & food research》2010,54(11):1636-1645
White tea (WT) is rich in flavan‐3‐ols as green tea (GT) and might provide health protective effects due to the strong antioxidant properties of flavan‐3‐ols. Since intervention studies with WT are lacking, we evaluated the effects of WT consumption on antioxidant status, antioxidant capacity and biomarkers of oxidative stress compared to water and GT. After an overnight fast, 70 healthy non‐smokers were randomized to consume 600 mL of WT, GT or water (control). Plasma (epi‐)catechin and epi(gallo)catechingallate, antioxidant capacity (Folin assay, trolox equivalent antioxidant capacity test), 8‐iso‐prostaglandin F2α, ascorbic acid and uric acid were determined before and several times within 8 h after consumption. DNA strand breaks were measured in vivo and ex vivo (H2O2 stimulation) in leukocytes. Plasma flavan‐3‐ols significantly increased after WT and GT ingestion. Trolox equivalent antioxidant capacity was lower after 5 h in controls versus WT (p=0.031) and GT (p=0.005). Folin‐Ciocalteu reducing capacity, ascorbic and uric acid as well as markers of oxidative stress (8‐iso‐prostaglandin‐F2α, DNA strand breaks) were not affected by the beverages. A short‐term increase of catechins does not change plasma antioxidant capacity in healthy subjects. Conclusions with respect to health protective effects of WT and GT on the basis of these biomarkers can, thus, not be drawn. 相似文献
12.
Systematic temporal relations between single neuronal activities or population activities are ubiquitous in the brain. No experimental evidence, however, exists for a direct modification of neuronal delays during Hebbian-type stimulation protocols. We show that in fact an explicit delay adaptation is not needed if one assumes that the synaptic strengths are modified according to the recently observed temporally asymmetric learning rule with the downregulating branch dominating the upregulating branch. During development, slow, unbiased fluctuations in the transmission time, together with temporally correlated network activity, may control neural growth and implicitly induce drifts in the axonal delays and dendritic latencies. These delays and latencies become optimally tuned in the sense that the synaptic response tends to peak in the soma of the postsynaptic cell if this is most likely to fire. The nature of the selection process requires unreliable synapses in order to give successful synapses an evolutionary advantage over the others. The width of the learning function also determines the preferred dendritic delay and the preferred width of the postsynaptic response. Hence, it may implicitly determine whether a synaptic connection provides a precisely timed or a broadly tuned "contextual" signal. 相似文献
13.
14.
Directional reflectance properties of natural surfaces are very important in the interpretation of remotely sensed data. The analysis of multispectral scanner data shows a distinct dependence on scan angle, wavelength (0.4–1.1 μm), and classes (e.g., bare soil, vegetation). This relationship can be described by polynomials determined by regression methods. Atmospheric effects are computed with a simple model by parametrization of the multiple scattered skylight. The model permits a quick and sufficient estimation of the airlight, depending on the data collection conditions. Comparisons of the scanner data with the corresponding model yield the following results: The differences between airborne and ground measurements are due to atmospheric effects. The directional variation in brightness is mainly caused by the object itself with the exception of short wavelengths and/or a very low albedo. The hue shift of vegetation is essentially produced by the object and modified by the atmosphere. Taking into account the directional reflectance properties in a direction-dependent classification procedure results in an improvement of up to 20% in comparison with algorithms used so far. Quantitative relationships between ground measurements and radiation measurements by airborne sensors including atmospheric effects can be determined with the proposed methods. 相似文献
15.
Heverhagen JT Ishaque N Zielke A Bohrer T Sitter H Berthold LD Klose KJ 《Magma (New York, N.Y.)》2001,12(1):4-9
Purpose: The purpose of this study was to evaluate MRI as a diagnostic tool in patients with suspected acute sigmoid diverticulitis.
Furthermore, we sought to develop an optimal imaging protocol in these patients.Patients and methods: Eleven patients with suspected acute diverticulitis were included in the study. All patients were imaged in a 1.0 T clinical
scanner using a body-array coil. Imaging sequences were single-shot TSE, HASTE-, STIR- and TrueFisp-sequence. All were obtained
in the frontal plane. The diagnosis was verified by a single experienced investigator, using ultrasound, and overall clinicopathological
outcome.Results: MRI enabled visualization of signs of an acute diverticulitis in all patients. However, the diagnosis of acute diverticulitis
was obtained in 10 patients only. The mean imaging time was 17.5 ± 5.5 min. STIR- and TrueFisp-sequences alone displayed all
findings, e.g pericolonic exsudation, edema and segmental narrowing, whereas SSTSE and HASTE-sequences showed no additional
information. Therefore, it appeared that the imaging protocol could be restricted to STIR- and TrueFisp-sequences.Conclusion: MRI is feasible as a fast, accurate and investigator-independent diagnostic tool in patients with suspected acute diverticulitis.
To prove its value in comparison to computed tomography or ultrasound, further studies are needed. 相似文献
16.
Lueftner T. Berthold J. Pacha C. Georgakos G. Sauzon G. Hoemke O. Beshenar J. Mahrla P. Just K. Hober P. Henzler S. Schmitt-Landsiedel D. Yakovleff A. Klein A. Knight R. J. Acharya P. Bonnardot A. Buch S. Sauer M. 《Solid-State Circuits, IEEE Journal of》2007,42(1):134-144
To meet the widely varying speed and power requirements of multifunctional mobile devices, an appropriate combination of technology features, circuit-level low-power techniques, and system architecture is implemented in a GSM/Edge baseband processor with multimedia and mixed-signal extensions. Power reduction techniques and performance requirements are derived from an analysis of relevant use cases and applications. The 44 mm2 baseband processor is fabricated in a 90-nm low-power CMOS technology with triple-well option and dual-gate oxide core devices. The ARM926 core achieves a maximum clock frequency of 380 MHz at 1.4-V supply due to the usage of thin oxide (1.6 nm) devices. Power dissipation can be adapted to the performance requirements by means of combined voltage and frequency scaling to reduce active power consumption in medium-performance mode by 68%. To reduce leakage currents during standby mode, large SRAM blocks, nFET sleep transistors, and circuit components with relaxed performance requirements are implemented using devices with 2.2-nm gate oxide thickness 相似文献
17.
18.
Otto T. Iancu Dietrich Munz Bernd Eigenmann Berthold Scholtes Eckard Macherauch 《Journal of the American Ceramic Society》1990,73(5):1144-1149
The residual stress state of brazed ceramic/metal compounds is described by means of X-ray residual stress determinations and analytical calculations using a model of three elastic infinite plates. It is shown that the residual stress state of the soldered compound depends on the materials combination and on the geometrical conditions. The combination of X-ray residual stress measurements and analytical calculations allows decisions on whether the assumption of a linear elastic model, based on elementary bending theory, is valid for the particular compounds. 相似文献
19.
We review the influence of rare-gas layers on image-potential states at metal surfaces. Experiments on Xe, Kr, and Ar on Cu(100) and on Xe/Ru(0001) that use the technique of time-resolved two-photon photoemission are discussed. The energetic position of the electron affinity, the geometry of the adsorbate layer, and dielectric screening are the factors that influence the dynamical and energetic properties of the states. Theories on various levels are compared, including 1- and 3-dimensional models and the GW approximation of many-body theory. We also present new results on buried interface states that exist in the band gaps of both the Cu(100) substrate and a thick adsorbed Ar layer. 相似文献
20.
Berthold Gänger VDE 《Electrical Engineering (Archiv fur Elektrotechnik)》1938,32(6):401-404
Zusammenfassung Um den Durchschlagsmechanismus einiger Isoliertsoffe zu untersuchen, werden diese an Spannungen verzerrter Kurvenformen gelegt. Für Kabelpapier ergab sich ein fast rein feldstärkebedingter Zusammenbruch, die bei den anderen Werkstoffen auftretenden Erscheinungen erlauben eine Erklärung auf Grund der wärmeelektrischen Theorie. 相似文献