全文获取类型
收费全文 | 1668篇 |
免费 | 65篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 104篇 |
综合类 | 1篇 |
化学工业 | 548篇 |
金属工艺 | 52篇 |
机械仪表 | 32篇 |
建筑科学 | 29篇 |
能源动力 | 92篇 |
轻工业 | 95篇 |
水利工程 | 3篇 |
无线电 | 110篇 |
一般工业技术 | 333篇 |
冶金工业 | 92篇 |
原子能技术 | 75篇 |
自动化技术 | 168篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 58篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 44篇 |
2017年 | 23篇 |
2016年 | 40篇 |
2015年 | 35篇 |
2014年 | 56篇 |
2013年 | 117篇 |
2012年 | 65篇 |
2011年 | 96篇 |
2010年 | 77篇 |
2009年 | 111篇 |
2008年 | 74篇 |
2007年 | 77篇 |
2006年 | 64篇 |
2005年 | 49篇 |
2004年 | 41篇 |
2003年 | 52篇 |
2002年 | 43篇 |
2001年 | 38篇 |
2000年 | 37篇 |
1999年 | 42篇 |
1998年 | 70篇 |
1997年 | 34篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有1734条查询结果,搜索用时 296 毫秒
1.
Hiromi Eba Yuki Masuzoe Toru Sugihara Hayao Yagi Tian Liu 《International Journal of Hydrogen Energy》2021,46(18):10642-10652
Ammonia generation was studied in the reaction between water and nitrogen-containing iron at 323 K and atmospheric pressure. Similar to metallic Fe, the interstitial compound Fe3N reduced water through Fe oxidation to produce hydrogen gas, while the N combined with atomic hydrogen to produce ammonia as a byproduct. The addition of carbon dioxide to this system accelerated the reaction with concomitant consumption of carbon dioxide. The promoted ammonia production upon addition of carbon dioxide can be attributed to the generation of atomic hydrogen from the redox reaction of carbonic acid and Fe, as well as removal of used Fe from the reaction system through the formation of a soluble carbonato complex. When carbonate was added to the reaction system, the production rates of ammonia and hydrogen increased further. The results here confirmed that ammonia can be synthesized from iron nitride under mild conditions by utilizing carbon dioxide. 相似文献
2.
Vancha Harish Effi Haque Magdalena
miech Hiroaki Taniguchi Sarah Jamieson Devesh Tewari Anupam Bishayee 《International journal of molecular sciences》2021,22(9)
Xanthohumol (XH) is an important prenylated flavonoid that is found within the inflorescence of Humulus lupulus L. (Hop plant). XH is an important ingredient in beer and is considered a significant bioactive agent due to its diverse medicinal applications, which include anti-inflammatory, antimicrobial, antioxidant, immunomodulatory, antiviral, antifungal, antigenotoxic, antiangiogenic, and antimalarial effects as well as strong anticancer activity towards various types of cancer cells. XH acts as a wide ranging chemopreventive and anticancer agent, and its isomer, 8-prenylnaringenin, is a phytoestrogen with strong estrogenic activity. The present review focuses on the bioactivity of XH on various types of cancers and its pharmacokinetics. In this paper, we first highlight, in brief, the history and use of hops and then the chemistry and structure–activity relationship of XH. Lastly, we focus on its prominent effects and mechanisms of action on various cancers and its possible use in cancer prevention and treatment. Considering the limited number of available reviews on this subject, our goal is to provide a complete and detailed understanding of the anticancer effects of XH against different cancers. 相似文献
3.
4.
Circular data are those for which the natural support is the unit circle and its toroidal extensions. Numerous constructions have been proposed which can be used to generate models for such data. We propose a new, very general, one based on the normalization of the spectra of complex-valued stationary processes. As illustrations of the new construction's application, we study models for univariate circular data obtained from the spectra of autoregressive moving average models and relate them to existing models in the literature. We also propose and investigate multivariate circular models obtained from the high-order spectra of stationary stochastic processes generated using linear filtering with an autoregressive moving average response function. A new family of distributions for a Markov process on the circle is also introduced. Results for asymptotically optimal inference for dependent observations on the circle are presented which provide a new paradigm for inference with circular models. The application of one of the new families of spectra-generated models is illustrated in an analysis of wind direction data. 相似文献
5.
6.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature 下载免费PDF全文
7.
Hiromichi Ichinose Masanori Taira Sachiko Furuta Hiroaki Katsuki 《Journal of the American Ceramic Society》2003,86(9):1605-1608
Niobium- or vanadium-doped anatase sols were prepared by hydrothermal treatment of 0.1 mol/dm3 peroxotitanium complex aqueous solutions dissolving 0–10 mol% niobium or vanadium at 100°C for 8 h. Niobium-doping caused the increase of lattice constants of anatase and the shape change of anatase crystal from spindle-like to cubic-like structure, but no change of the optical absorbance. Vanadium-doping caused the decrease of lattice constant of c -axis, the miniaturization of anatase crystal and the increase of optical absorbance at the wavelength from 350–700 nm. 相似文献
8.
With the growing size and complexity of power systems, system analysis—such as transients calculation—takes much time. Hence, fast calculation methods are required. Although parallel processing is a hopeful method, there have been difficulties in the parallel solution of linear equations which appear in power-flow calculations by the Newton-Raphson method. This paper aims at the fast calculation of the power-flow problem by means of parallel processing. In order to improve the suitability to the parallel solution of the differential equation in transients calculation, we assume the use of a direct-mapping parallel processing machine to map directly the network of a power system onto a network of processors. Under this assumption, we propose a new parallel-processing-oriented method in which the linear equation is solved by linear iterations between nodes with Aitken acceleration. We simulate the method on three model power systems and compare this Parallel Iterative Method (PIN) with a Parallel Direct Method (PDM) which uses the banded matrix according to the number of operations required. As a result, we can expect that PIM may solve linear equations faster than PDM with m processors, although the PIM might be inferior to the PDM with m × m processors, where m denotes the half-band width of the banded matrix. 相似文献
9.
Donguk Kim Author Vitae Author Vitae Kokichi Sugihara Author Vitae 《Computer aided design》2006,38(1):14-21
The Apollonius Tenth Problem, as defined by Apollonius of Perga circa 200 B.C., has been useful for various applications in addition to its theoretical interest. Even though particular cases have been handled previously, a general framework for the problem has never been reported. Presented in this paper is a theory to handle the Apollonius Tenth Problem by characterizing the spatial relationship among given circles and the desired Apollonius circles. Hence, the given three circles in this paper do not make any assumption regarding on the sizes of circles and the intersection/inclusion relationship among them. The observations made provide an easy-to-code algorithm to compute any desired Apollonius circle which is computationally efficient and robust. 相似文献
10.
Satoshi Takeuchi Ryo Sugihara 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1998,410(3):104-508
The longitudinal electric field of single and double Gaussian laser beams are used to accelerate electrons. The longitudinal field of the single beam is concentrated on the axis and is favourable for acceleration. A set of two beams is considered. Beams run parallel, collinearly, overlap partially and have a phase difference iπ in between. As a result, the transverse components of fields cancel each other while the longitudinal components are double-fold. In both schemes, the electrons are accelerated in lengths of the Rayleigh range, which is common to the plasma-based accelerators. 相似文献