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排序方式: 共有335条查询结果,搜索用时 875 毫秒
31.
Perica Paunović Orce Popovski Emilija Fidančevska Bogdan Ranguelov Dafinka Stoevska Gogovska Aleksandar T. Dimitrov Svetomir Hadži Jordanov 《International Journal of Hydrogen Energy》2010
The subject of this work is the use of non-stoichiometric titanium oxides – Magneli phases as support material of Co-based electrocatalysts aimed for hydrogen/oxygen evolution reaction. Commercial micro-scaled Ebonex (Altraverda, UK) was mechanically treated for 4, 8, 12, 16 and 20 h and further Co metallic phase was grafted by sol-gel method. Morphology of Co/Ebonex electrocatalysts was observed by means of TEM and SEM microscopy, while electrochemical behavior by means of cyclic voltammetry and steady-state galvanostatic method. 相似文献
32.
Kazuya Aida Yasuhiko Benino Vesselin Dimitrov Takayuki Komatsu Ryuji Sato 《Journal of the American Ceramic Society》2000,83(5):1192-1198
The kinetics of enthalpy relaxation (recovery) at the glass transition in x K2 O·(20− x )MgO·80TeO2 glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO2 -based glasses. Ternary glasses such as 10K2 O·10MgO·80TeO2 show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow E η and the glass transition temperature T g is m = 55–62, indicating a fragile character in TeO2 -based glasses. Large heat capacity changes of 43.1–48.2 J·mol−1 ·K−1 are also observed at the glass transition. The activation energy for enthalpy relaxation Δ H is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of Δ H = 897–1268 kJ·mol−1 are obtained. Negative deviation from additivity in Δ H is also observed. Values of the Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from Δ H and T g are 0.33–0.42 K−1 . It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses. 相似文献
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34.
It is widely recognized that many cost-efficient opportunities to employ end-use energy efficiency measures exist in countries in transition (CITs) and that municipal authorities have an essential role to play in capturing these opportunities. The aim of this paper is to review the factors that determine the degree of involvement of local authorities in the market for energy services and energy efficient (EE) equipment in three CITs: Bulgaria, Hungary and the Former Yugoslav Republic of Macedonia (hereafter: Macedonia). We achieve this aim by examining the current status of local governments as the most powerful determinant of municipal market involvement. Two broad groups of factors are discussed: statutory obligations and powers of local governments, especially energy-related tasks, and finance. We explain how specific features within these two areas may influence the motivation of local authorities to improve energy efficiency and their capacity to do so. We argue that greater decentralization is the first step in augmenting the role of local authorities in the market for energy services and EE equipment. Based on the analysis we give recommendations on how to encourage municipal authorities to use market mechanisms more extensively to deliver energy efficiency. 相似文献
35.
The glass forming region in the quaternary system under increased oxygen pressure and at a slow melt cooling rate (2 to 2.5° C min-1) has been determined. The stable glasses are located in the central part of the system but nearer to the SeO2-TeO2 side. The structural units of these two glass formers are of decisive importance in building up the glass lattice. Infrared spectra of selected compositions from the glass forming region are taken. From the data obtained for the binary glasses in the TeO2-V2O5, TeO2-SeO2, TeO2-MoO3, V2O5-MoO3 systems and the spectra of the four component compositions, it is shown that the basic structural units participating in the glass lattice formation are the SeO3, VO5, TeO4 and TeO3 groups. Structural models are proposed: glasses in the SeO2 direction possess laminar and chain structure, while with increase of TeO2 concentration, a three-dimensional structure is built up. 相似文献
36.
Shiva K. Madishetty Arjuna Madanayake Renato J. Cintra Vassil S. Dimitrov Dale H. Mugler 《Multidimensional Systems and Signal Processing》2014,25(4):829-845
A multiplierless architecture based on algebraic integer representation for computing the Daubechies 4-tap wavelet transform for 1-D/2-D signal processing is proposed. This architecture improves on previous designs in a sense that it minimizes the number of parallel 2-input adder circuits. The algorithm was achieved using numerical optimization based o exhaustive search over the algebraic integer representation. The proposed architecture furnishes exact computation up to the final reconstruction step, which is the operation that maps the exactly computed filtered results from algebraic integer representation to fixed-point. Compared to Madishetty et al. (IEEE Trans Circuits Syst I (Accepted, In Press), 2012a), this architecture shows a reduction of \(10\cdot n-3\) adder circuits, where \(n\) is the number of wavelet decomposition levels. Standard \(512\times 512\) images Mandrill, Lena, and Cameraman were submitted to digital realizations of both proposed algebraic integer based as well as fixed-point schemes, leading to quantifiable comparisons. The design is physically implemented for a 4-level 2-D decomposition using a Xilinx Virtex-6 vcx240t-1ff1156 FPGA device operating at up to a maximum clock frequency of 263.15 MHz. The FPGA implementation is tested using hardware co-simulation using an ML605 board with clock of 100 MHz. A 45 nm CMOS synthesis shows improved clock frequency of better than 500 MHz for a supply voltage of 1.1 V. 相似文献
37.
Dachev Ts Dimitrov P Tomov B Matviichuk Y Spurny F Ploc O Brabcova K Jadrnickova I 《Radiation protection dosimetry》2011,144(1-4):675-679
The main purpose of Liulin-type spectrometry-dosimetry instruments (LSDIs) is cosmic radiation monitoring at the workplaces. An LSDI functionally is a low mass, low power consumption or battery-operated dosemeter. LSDIs were calibrated in a wide range of radiation fields, including radiation sources, proton and heavy-ion accelerators and CERN-EC high-energy reference field. Since 2000, LSDIs have been used in the scientific programmes of four manned space flights on the American Laboratory and ESA Columbus modules and on the Russian segment of the International Space Station, one Moon spacecraft and three spacecraft around the Earth, one rocket, two balloons and many aircraft flights. In addition to relative low price, LSDIs have proved their ability to qualify the radiation field on the ground and on the above-mentioned carriers. 相似文献
38.
Andresen H Nikolov SI Jensen JA 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(5):935-943
This paper describes the application of 3-D synthetic aperture focusing (SAF) to a single-element trans-rectal ultrasound transducer. The transducer samples a 3-D volume by simultaneous rotation and translation, giving a helical motion. Two different 3-D SAF methods are investigated, a direct and a two-step approach. Both methods perform almost identically for simulated scatterers and give a significant improvement in azimuth resolution and a constant resolution in elevation. Side lobes below -60 dB are achievable for both methods. Validation of the method is achieved by scanning a simple wire phantom and a complex phantom containing wires in azimuth and elevation. The simple wire phantom shows the same results as that found through simulation. The complex phantom shows simultaneous focusing in azimuth and elevation for the wire scatterers. Consideration of the processing requirements for both 3-D SAF methods shows that the two-step approach can give equivalent performance using an order of magnitude fewer calculations. This reduction requires a temporary storage of 9.1 GB of data for the investigated setup. 相似文献
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40.
Recently, a new method for measuring telomere lengths based on telomere DNA content was developed. The method, which is based on the ratio of telomere to centromere DNA content (TC ratio), is highly sensitive, allowing the analysis of small quantities of DNA. However, the method required the isolation of DNA, which can be difficult or impossible for small numbers of cells. Here, we suggest an improvement of this method that can directly estimate telomere lengths from whole cells. We optimized the method for whole cells and purified DNA and found that accurate TC ratios can be obtained from as little as 9 ng of DNA or 800 whole cells. There was no statistically significant difference between the ratios obtained with purified DNA or with whole cells, indicating that the isolation of DNA is not necessary for small samples. 相似文献