全文获取类型
收费全文 | 260篇 |
免费 | 9篇 |
专业分类
综合类 | 2篇 |
化学工业 | 39篇 |
机械仪表 | 2篇 |
建筑科学 | 7篇 |
能源动力 | 4篇 |
轻工业 | 29篇 |
无线电 | 19篇 |
一般工业技术 | 23篇 |
冶金工业 | 127篇 |
原子能技术 | 1篇 |
自动化技术 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2014年 | 9篇 |
2013年 | 4篇 |
2012年 | 2篇 |
2011年 | 10篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1962年 | 2篇 |
1959年 | 1篇 |
1956年 | 4篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有269条查询结果,搜索用时 15 毫秒
21.
The optimum procedure for locating a sync word periodically inserted in uncoded binary data received over a binary symmetric channel is based on the Hamming or bit distance metric. This concise paper addresses the corresponding frame-sync problem for biorthogonally coded data transmitted over the additive white Gaussian noise (AWGN) channel. For conceptual convenience, thek -bit words from the decoder output are treated as "super symbols" from an alphabet of dimension 2k. It is argued that the optimum sync-word search over the decoded data stream is based on a supersymbol distance rule matched to the properties of the biorthogonally coded transmissions over the noisy channel. An optimum frame-sync acquisition algorithm based on this distance rule is formulated, and its performance is investigated. As an example, the performance of this optimum frame-sync algorithm is contrasted analytically with that of a Hamming distance algorithm operating on decoded (32, 6) biorthogonal data, a case of interest to some recent unmanned American space missions. 相似文献
22.
Laboratory experiments have been conducted to elucidate the degradation of alpha-methylnaphthalene in lake sediments using an advanced oxidation process (AOP) employing peroxy-acids as oxidizing agents. Abiotic degradation of alpha-methylnaphthalene was observed in sediment samples exposed to a 1:1:1 v/v/v mixture of water/organic acid/hydrogen peroxide solution. Sediment samples were collected from Lake Macatawa (Holland, MI) and ranged in total organic carbon content from 2.1% (sandy sediment sample III) to 12.8% (silty-clay sediment sample I) and surface area, which ranged from 3.2m(2)/g (sandy sediment sample III) to 22.0m(2)/g (silty-clay sediment sample I). Analytical measurements performed by gas chromatography revealed varied rates of degradation, depending on the type of acid and the characteristics of the sediment sample. Within 24h, alpha-methylnaphthalene was reduced to 70% and 100% of its original concentration when propionic acid and acetic acid were used as the organic acids, respectively. The formation of products was explored using a gas chromatograph equipped with a mass spectrometer and indicated mainly the formation of lower molecular weight compounds, such as alkyl chains. This AOP method of PAH degradation in sediment/liquid slurry was fast acting and products were most likely biodegradable. 相似文献
23.
Confocal microscopy is used in the study of colloidal gels, glasses, and binary fluids. We measure the three-dimensional positions of colloidal particles with a precision of approximately 50 nm (a small fraction of each particle's radius) and with a time resolution sufficient for tracking the thermal motions of several thousand particles at once. This information allows us to characterize the structure and the dynamics of these materials in qualitatively new ways, for example, by quantifying the topology of chains and clusters of particles as well as by measuring the spatial correlations between particles with high mobilities. We describe our experimental technique and describe measurements that complement the results of light scattering. 相似文献
24.
25.
Ample empirical research on values has demonstrated that clients' values tend to become increasingly like those of their therapist during therapy. There is little research, however, on how therapists negotiate value conflicts and the role of values in therapy. In order to better understand this process, 14 expert psychotherapists from four major psychotherapy orientations were interviewed about their use of values in the psychotherapeutic change process. A grounded theory analysis was conducted leading to an integrative understanding of how expert therapists from different orientations conceptualize the relationship of values and change in therapy and how they work with values in sessions. Based on this analysis, four transtheoretical principles were generated that can be applied to training and practice and used to inform research on psychotherapy process and integration. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
26.
A combination of step potential electrochemical spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS) has been used to examine the electrochemical cycling behaviour of a well-characterized birnessite-phase manganese dioxide sample for use in electrochemical capacitors. The resistance and interfacial properties of the macroscopic electrode were found to be irreversible with cycling. However, the corresponding properties for the individual particles were more reversible, although they did show substantial hysteresis in their behaviour during cycling. This behaviour was discussed in terms of the structural, conductivity and morphological characteristics of the birnessite at different depths of discharge. 相似文献
27.
A gene encoding a chitin synthase with a myosin motor-like domain (csm1) was isolated from Pyricularia oryzae using a PCR fragment amplified from a fungal chitin synthase conserved region. The deduced amino acid sequence of csm1 is homologous to that of CsmA of Aspergillus nidulans (65% identity). The putative gene product of csm1 is consisted of the myosin motor-like domain and a chitin synthase domain as in A. nidulans csmA. The chitin synthase domain of its C-terminus was also homologous to Aspergillus fumigatus ChsE (61.4% identity) and Ustilago maydis Chs6 (48.6% identity) that encode class V chitin synthases. Northern analysis demonstrated that the csm1 was expressed throughout the mycelial growth of P. oryzae. This is the first report on the isolation of the gene encoding a class V chitin synthase with the myosin motor-like domain from P. oryzae. 相似文献
28.
Sergio Brovelli Francesco Meinardi Gustaf Winroth Oliver Fenwick Giuseppe Sforazzini Michael J. Frampton Leszek Zalewski James A. Levitt Francesco Marinello Piero Schiavuta Klaus Suhling Harry L. Anderson Franco Cacialli 《Advanced functional materials》2010,20(2):272-280
Here, it is demonstrated that energy transfer in a blend of semiconducting polymers can be strongly reduced by non‐covalent encapsulation of one constituent, ensured by threading of the conjugated strands into functionalized cyclodextrins. Such macrocycles control the minimum intermolecular distance of chromophores with similar alignment, at the nanoscale, and therefore the relevant energy transfer rates, thus enabling fabrication of white‐light‐emitting diodes (CIE coordinates: x = 0.282, y = 0.336). In particular, white electroluminescence in a binary blend of a blue‐emitting, organic‐soluble rotaxane based on a polyfluorene derivative and the green‐emitting poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole ( F8BT ) is achieved. Morphological and structural analyses by atomic force microscopy, fluorescence mapping, µ‐Raman, and fluorescence lifetime microscopy are used to complement optical and electroluminescence characterization, and to enable a deeper insight into the properties of the novel blend. 相似文献
29.
2‐Dimensional Transition Metal Dichalcogenides with Tunable Direct Band Gaps: MoS2(1–x)Se2x Monolayers 下载免费PDF全文
John Mann Quan Ma Patrick M. Odenthal Miguel Isarraraz Duy Le Edwin Preciado David Barroso Koichi Yamaguchi Gretel von Son Palacio Andrew Nguyen Tai Tran Michelle Wurch Ariana Nguyen Velveth Klee Sarah Bobek Dezheng Sun Tony. F. Heinz Talat S. Rahman Roland Kawakami Ludwig Bartels 《Advanced materials (Deerfield Beach, Fla.)》2014,26(9):1399-1404
30.
Vítor J.P. Vilar Lívia X. Pinho Ariana M.A. Pintor Rui A.R. Boaventura 《Solar Energy》2011,85(9):1927-1934
Heterogeneous (TiO2/UV, TiO2/H2O2/UV) and homogenous (H2O2/UV, Fe2+/H2O2/UV) solar advanced oxidation processes (AOPs) are proposed for the treatment of recalcitrant textile wastewater at pilot-plant scale with compound parabolic collectors (CPCs). The textile wastewater presents a lilac colour, with a maximum absorbance peak at 516 nm, high pH (pH = 11), moderate organic content (DOC = 382 mg C L−1, COD = 1020 mg O2 L−1) and high conductivity (13.6 mS cm−1), associated with a high concentration of chloride (4.7 g Cl− L−1). The DOC abatement is similar for the H2O2/UV and TiO2/UV processes, corresponding only to 30% and 36% mineralization after 190 kJUV L−1. The addition of H2O2 to TiO2/UV system increased the initial degradation rate more than seven times, leading to 90% mineralization after exposure to 100 kJUV L−1. All the processes using H2O2 contributed to an effective decolourisation, but the most efficient process for decolourisation and mineralization was the solar-photo-Fenton with an optimum catalyst concentration of 100 mg Fe2+ L−1, leading to 98% decolourisation and 89% mineralization after 7.2 and 49.1 kJUV L−1, respectively. According to the Zahn-Wellens test, the energy dose necessary to achieve a biodegradable effluent after the solar-photo-Fenton process with 100 mg Fe2+ L−1 is 12 kJUV L−1. 相似文献