全文获取类型
收费全文 | 1305篇 |
免费 | 93篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 302篇 |
金属工艺 | 26篇 |
机械仪表 | 25篇 |
建筑科学 | 44篇 |
矿业工程 | 1篇 |
能源动力 | 56篇 |
轻工业 | 91篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 120篇 |
一般工业技术 | 272篇 |
冶金工业 | 144篇 |
原子能技术 | 12篇 |
自动化技术 | 279篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 39篇 |
2021年 | 51篇 |
2020年 | 27篇 |
2019年 | 51篇 |
2018年 | 45篇 |
2017年 | 36篇 |
2016年 | 53篇 |
2015年 | 50篇 |
2014年 | 61篇 |
2013年 | 95篇 |
2012年 | 90篇 |
2011年 | 139篇 |
2010年 | 78篇 |
2009年 | 72篇 |
2008年 | 89篇 |
2007年 | 55篇 |
2006年 | 61篇 |
2005年 | 42篇 |
2004年 | 25篇 |
2003年 | 26篇 |
2002年 | 19篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1958年 | 2篇 |
1954年 | 3篇 |
1948年 | 2篇 |
1947年 | 2篇 |
1946年 | 2篇 |
排序方式: 共有1399条查询结果,搜索用时 31 毫秒
1.
2.
Maria A. Ospina Monica Pizarro Thierry Tran Julien Ricci John Belalcazar Jorge L. Luna Luis F. Londoño Sandra Salazar Hernan Ceballos Dominique Dufour Luis A. Becerra Lopez-Lavalle 《International Journal of Food Science & Technology》2021,56(3):1343-1353
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes. 相似文献
3.
Various image processing applications exploit a model of the human visual system (HVS). One element of HVS-models describes the masking-effect, which is typically parameterized by psycho-visual experiments that employ superimposed sinusoidal stimuli. Those stimuli are oversimplified with respect to real images and can capture only very elementary masking-effects. To overcome these limitations a new psycho-visual test method is proposed. It is based on natural scenery stimuli and operates in the wavelet domain. The collected psycho-visual data is finally used to evaluate the performance of various masking models under conditions as found in real image processing applications like compression. 相似文献
4.
We study the effect of Josephson coupling between adjacent superconducting layers on the BCS energy spectrum. We find that the interference between the gap functions of two layers can lead to vanishing condensation energy for perpendicular momenta corresponding to the formation of standing waves. We therefore predict a conventional energy spectrum for large interlayer spacings, if the gap of the single layers has no nodes, and in all cases a gapless spectrum for small spacings. Within the experimental error, our numerical results account for the low-temperature dependence of the penetration depth reported in Nd1.85Ce0.15CuO4 and YBa2Cu3O6.9. 相似文献
5.
The reactivity of lithium with layered chalcogenides InSe and In2Se3 is studied using transmission electron microscopy (TEM), electrochemical potential spectroscopy (EPS) and Raman scattering (RS). It is found that for x(Li)≥0.1 in LixInSe, the host material decomposes with the formation of lithium selenide. The presence of Li2Se is confirmed by Raman spectroscopy. The insertion of Li into In2Se3 appears more stable with the occurrence of a superlattice formation at x(Li)≈0.25. The superstructure corresponding to the 2a×2a lattice is consistent with the EPS measurements of LixIn2Se3. 相似文献
6.
The article presents structure of toxicological information given by phone to the physicians involved in treatment of acute poisonings, private persons the services monitoring the working environment. The information comprises data on toxic effect on human organism, chemical composition, therapeutic procedure in acute poisonings as well as the data on hazards occurring in every day life. The consultations chiefly regarded poisonings with drugs, pesticides, alcohols, organic solvents and corrosive substances. The analysis has shown that poisonings of children aged below 14 years pose a significant problem. Moreover, it has been noted that there is a growing demand for toxicological consultations among the general population. They play a significant role in education of the society, making them aware of the hazards created by various chemicals used in the households and occurring in the working environment which contributes to promotion of the poisonings prevention. 相似文献
7.
8.
Breton M. Tremblay P. Julien C. Cyr N. Tetu M. Latrasse C. 《IEEE transactions on instrumentation and measurement》1995,44(2):162-165
The performance of 196.0-THz (1529-nm) DFB lasers frequency-locked to absorption lines of a rubidium vapor optically pumped at 384.2 THz (780.2 nm) is studied. The absorption profiles of the pumped vapor are measured under various conditions and compared with theoretical predictions. A bright resonance resulting from the cascade of two cycling transitions is characterized both experimentally and theoretically. The measured frequency stability of a DFB laser frequency-locked to this line reaches a level of 2×10-10 for an averaging time of 100 s when compared to a similar laser locked to an acetylene line 相似文献
9.
This paper addresses the problem of virtual pedestrian autonomous navigation for crowd simulation. It describes a method for solving interactions between pedestrians and avoiding inter-collisions. Our approach is agent-based and predictive: each agent perceives surrounding agents and extrapolates their trajectory in order to react to potential collisions. We aim at obtaining realistic results, thus the proposed model is calibrated from experimental motion capture data. Our method is shown to be valid and solves major drawbacks compared to previous approaches such as oscillations due to a lack of anticipation. We first describe the mathematical representation used in our model, we then detail its implementation, and finally, its calibration and validation from real data. 相似文献
10.
Michelle BarraganStephen Woods Howard L. Julien D.B. WilsonRegor Saulsberry 《Combustion and Flame》2002,131(3):316-328
Thermodynamic equations of state are evaluated for the aerospace fuels hydrazine and monomethylhydrazine using Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) formulations. The PR formulation is shown to be the best fit for hydrazine, and the SRK formulation to be the best fit for monomethylhydrazine, based on available critical property data and evaluations of thermodynamic consistency. The adequacy of the differing property data for these fuels in the literature is discussed, and the methodology used to validate the formulations is outlined. The importance of using appropriate real fluid equations of state in thermodynamic safety and hazards analysis of fuel systems is demonstrated by considering an adiabatic compression of gaseous fuels previously postulated in accident scenarios of aerospace propulsion systems. Calculation of isentropic compression temperatures for pure components using ideal gas constant heat capacity, ideal gas with variable heat capacity, and real fluid equations of state are compared to illustrate the need for real fluid equations of state. In addition, three separate approaches are used for estimating isentropic compression temperatures for mixtures involving these fuels, again illustrating the importance of treating these mixtures as real fluids for design and safety analysis. 相似文献