全文获取类型
收费全文 | 3043篇 |
免费 | 197篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 88篇 |
综合类 | 4篇 |
化学工业 | 737篇 |
金属工艺 | 65篇 |
机械仪表 | 100篇 |
建筑科学 | 104篇 |
矿业工程 | 8篇 |
能源动力 | 124篇 |
轻工业 | 503篇 |
水利工程 | 14篇 |
石油天然气 | 13篇 |
无线电 | 190篇 |
一般工业技术 | 774篇 |
冶金工业 | 50篇 |
原子能技术 | 10篇 |
自动化技术 | 457篇 |
出版年
2023年 | 21篇 |
2022年 | 14篇 |
2021年 | 68篇 |
2020年 | 56篇 |
2019年 | 69篇 |
2018年 | 118篇 |
2017年 | 112篇 |
2016年 | 139篇 |
2015年 | 103篇 |
2014年 | 150篇 |
2013年 | 336篇 |
2012年 | 212篇 |
2011年 | 223篇 |
2010年 | 185篇 |
2009年 | 133篇 |
2008年 | 141篇 |
2007年 | 125篇 |
2006年 | 95篇 |
2005年 | 55篇 |
2004年 | 31篇 |
2003年 | 49篇 |
2002年 | 40篇 |
2001年 | 31篇 |
2000年 | 38篇 |
1999年 | 34篇 |
1998年 | 30篇 |
1997年 | 22篇 |
1996年 | 31篇 |
1995年 | 24篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1985年 | 33篇 |
1984年 | 35篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 39篇 |
1980年 | 34篇 |
1979年 | 25篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 22篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1972年 | 14篇 |
排序方式: 共有3241条查询结果,搜索用时 0 毫秒
111.
Milena Premović Milica Tomović Duško Minić Dragan Manasijević Dragana Živković Vladan Ćosović Vladan Grković Aleksandar Đorđević 《Journal of Materials Engineering and Performance》2017,26(6):2491-2501
Ternary Al-Ag-Ga system at 200 °C was experimentally and thermodynamically assessed. Isothermal section was extrapolated using optimized thermodynamic parameters for constitutive binary systems. Microstructure and phase composition of the selected alloy samples were analyzed using light microscopy, scanning electron microscopy combined with energy-dispersive spectrometry and x-ray powder diffraction technique. The obtained experimental results were found to be in a close agreement with the predicted phase equilibria. Hardness and electrical conductivity of the alloy samples from four vertical sections Al-Ag80Ga20, Al-Ag60Ga40, Ag-Al80Ga20 and Ag-Al60Ga40 of the ternary Al-Ag-Ga system at 200 °C were experimentally determined using Brinell method and eddy current measurements. Additionally, hardness of the individual phases present in the microstructure of the studied alloy samples was determined using Vickers microhardness test. Based on experimentally obtained results, isolines of Brinell hardness and electrical conductivity were calculated for the alloys from isothermal section of the ternary Al-Ag-Ga system at 200 °C. 相似文献
112.
Sla?ana Žilić Dejan Dodig Vesna Hadži‐Tašković Šukalović Milan Maksimović Goran Saratlić Biljana Škrbić 《International Journal of Food Science & Technology》2010,45(7):1360-1367
Potential beneficial components, including proteins, total phenolics, total flavonoids, carotenoids, tocopherols, and DPPH radical scavenging activity, were investigated in wholemeal of ten bread (T. aestivum L.) and ten durum (T. durum Desf.) novel wheat genotypes. In addition, the activity rate of lipoxygenase (LOX) and peroxidase (POD) enzymes implicated in the antioxidant metabolism was determined. The protein contnet and the antioxidant properties varied according to the two different wheat species, as well as, between the different bread and durum wheat genotypes themselves. The results indicated significant differences in proteins and antioxidant compounds between bread and durum wheat. Higher total proteins, wet gluten and antioxidants contents, combined with lower LOX and POD activities, point to a higher nutritive value of durum wheat than bread wheat. 相似文献
113.
The kinetics of a batch solid–liquid extraction of total phenolic compounds (PC) from milled grape seed (Vitis vinifera L. cv. “Frankovka”) using 50% ethanol at different extraction temperatures (25–80 °C) was studied. The maximum yield of PC was 0.13 kgGAE/kgdb after 200 min of extraction in agitated vessel at 80 °C. A new model based on the assumptions of a first order kinetics mechanism for the solid–liquid extraction and a linear equilibrium at the solid–liquid interface was developed. The model involves the concept of broken and intact cells in order to describe two successive extraction periods: a very fast surface washing process followed by slow diffusion of phenolic compounds from grape seeds to the solvent.The proposed model is suited to fit experimental data and to simulate the extraction of phenolic compounds, which was confirmed by the correlation coefficient (r ? 0.965), the root mean square error (RMSE ? 0.003 kgGAE/kgdb) and the mean relative deviation modulus (E ? 2.149%). The temperature influenced both equilibrium partition coefficients of phenolic compounds and transport properties, which is manifested by a relatively high value of activation energy (23–24) kJ/mol and by values of effective diffusivity in seed particles. 相似文献
114.
Jelena Svorcan Slobodan Stupar Dragan Komarov Ognjen Peković Ivan Kostić 《Journal of Mechanical Science and Technology》2013,27(8):2367-2373
Small-scale vertical axis wind turbines are regarded today as an attractive source of green energy, still insufficiently implemented and tested. This paper presents a fast design methodology of such a VAWT, in terms of choosing its main parameters: airfoil, rotor diameter and solidity. For obtaining generated power of each considered geometrical model at different undisturbed wind velocities and rotor angular velocities two models were used — momentum and vortex-wake model, combined with experimentally measured airfoil data (airfoil lift and drag coefficients). Even though the former model is simpler, it is the most utilized model, known to provide good results in stationary working regimes. Both models still present fairly accurate and fast tools for computation and optimization, particularly useful in the phase of conceptual design. In this research, the use of the momentum model resulted in determination of the maximal power coefficient, optimal- and minimal freestream velocity for every considered VAWT model. From these output parameters, a selection of the optimal geometric model was done, and a more detailed transient analysis and flow representation around the selected solution was obtained by the vortex-wake model. The results obtained by the two used computational models coincide satisfactorily. 相似文献
115.
Stela Jokić Sandra Svilović Zoran Zeković Senka Vidović 《International Journal of Food Science & Technology》2011,46(5):1031-1037
The solubility of soybean oil in supercritical carbon dioxide has been determined in the pressure range of 100–300 bar and in the temperature range of 313–323 K. The obtained values (from 0.0005 to 0.02055 g L?1) have been correlated using four different empirical equations proposed correspondingly by Chrastil, del Valle and Aquilera, Adachi and Lu and Sparks et al. Since the Sparks et al. equation provided the lowest average absolute relative deviation (AARD) (10.25%) than other models in the examined experimental range, a modified equation of Sparks et al. model was developed for predicting the solubility of soybean oil in supercritical carbon dioxide as a function of temperature and density. An improved equation showed the lowest deviation (2.15%) between experimental data than the other empirical equations considered in this study. The proposed equation was also applied for correlating the solubility of linoleic acid (AARD was 2.40%). 相似文献
116.
C. Kadapa W.G. Dettmer D. Perić 《International journal for numerical methods in engineering》2015,101(7):521-539
This contribution investigates the performance of a least‐squares finite element method based on non‐uniform rational B‐splines (NURBS) basis functions. The least‐squares functional is formulated directly in terms of the strong form of the governing equations and boundary conditions. Thus, the introduction of auxiliary variables is avoided, but the order of the basis functions must be higher or equal to the order of the highest spatial derivatives. The methodology is applied to the incompressible Navier–Stokes equations and to linear as well as nonlinear elastic solid mechanics. The numerical examples presented feature convective effects and incompressible or nearly incompressible material. The numerical results, which are obtained with equal‐order interpolation and without any stabilisation techniques, are smooth and accurate. It is shown that for p and h refinement, the theoretical rates of convergence are achieved. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
117.
118.
Coastal parts of Croatia are dominated by the SW‐verging Dinaric foldbelt, to the west and SW of which is the Adriatic Basin (the stable foreland). In both areas, the stratigraphic column is dominated by a thick carbonate succession ranging from Carboniferous to Miocene. Four megasequences have been identified: (i) a pre‐platform succession ranging in age from Late Carboniferous (Middle Pennsylvanian: Moscovian) to Early Jurassic (Early Toarcian; Bru?ane and Ba?ke Ostarije Formations); (ii) an Early Jurassic to Late Cretaceous platform megasequence (Mali Alan Formation); (iii) a Paleogene to Neogene post‐platform megasequence (Ra?a Formation); and (iv) a Neogene to Quaternary (Pliocene to Holocene) megasequence (Istra and Ivana Formations). A number of organic‐rich intervals with source rock potential have been identified on‐ and offshore Croatia: Middle and Upper Carboniferous, Upper Permian, Lower and Middle Triassic, Lower and Upper Jurassic, Lower and Upper Cretaceous, Eocene, and Pliocene – Pleistocene. Traps and potential plays have been identified from seismic data in the Dinaric belt and adjacent foreland. Evaporites of Permian, Triassic and Neogene (Messinian) ages form potential regional seals, and carbonates with secondary porosity form potential reservoirs. Oil and gas shows in wells in the Croatian part of the Adriatic Basin have been recorded but no oil accumulations of commercial value have yet been discovered. In the northern Adriatic offshore Croatia, Pliocene hemi‐pelagic marlstones and shales include source rocks which produce commercial volumes of biogenic gas. The gas is reservoired in unconsolidated sands of the Pleistocene Ivana Formation. 相似文献
119.
I Zorica D. Budić 《Journal of the American Planning Association. American Planning Association》2013,79(2):244-250
Geographic information systems have the potential to aid planning functions in both data processing and decision making. Because the incorporation of GIS technology into local government is at an early stage, knowledge about GIS implementation and its impact on planning activities is scarce. Using a survey of local governments in four southeastern states, this paper explores how the new technology affects planning and whether it meets the expectations of the planning agencies using it. Most of the agencies surveyed report improvements in communication of information, data accessibility, and data accuracy. They report that more current data are available, and they have confidence in analyses performed with GIS technology. Political support, staffing, length of experience with GIS technology, system sharing, data-base contents, and number and type of GIS applications all exert some influence on either planning operations or decision making. While experience with GIS emerged as the most significant factor in achieving operational benefits, using GIS technology for analytical tasks positively affected improvements in decision making. 相似文献
120.
Ivana Tomaz Luna Maslov Domagoj Stupić Darko Preiner Danijela Ašperger Jasminka Karoglan Kontić 《分离科学与技术》2016,51(2):255-268
Grape skin contains large amounts of different flavonoids so it can be used for their recovery. Optimization of enzyme-assisted extraction of flavonoids was conducted using oenological enzyme preparations with respect to enzyme dosage, temperature, extraction time, pH, and enzyme preparation. Optimal conditions were obtained using enzyme preparation Lallzyme EX-V, at the temperature of 45°C, time of 3 h, pH 2.0, and enzyme dosage of 10.52 mg/g. The new optimized extraction method is less expensive, simple, accurate, and selective for the recovery of simple flavonoids. It is based on an environmentally-friendly extraction solvent which may provide a valuable alternative to conventional methods. 相似文献