全文获取类型
收费全文 | 169703篇 |
免费 | 23674篇 |
国内免费 | 5193篇 |
专业分类
电工技术 | 7702篇 |
技术理论 | 11篇 |
综合类 | 7810篇 |
化学工业 | 39009篇 |
金属工艺 | 7090篇 |
机械仪表 | 8510篇 |
建筑科学 | 11719篇 |
矿业工程 | 3421篇 |
能源动力 | 4600篇 |
轻工业 | 16161篇 |
水利工程 | 2386篇 |
石油天然气 | 6700篇 |
武器工业 | 830篇 |
无线电 | 23417篇 |
一般工业技术 | 27631篇 |
冶金工业 | 7735篇 |
原子能技术 | 1534篇 |
自动化技术 | 22304篇 |
出版年
2024年 | 579篇 |
2023年 | 2215篇 |
2022年 | 3758篇 |
2021年 | 5416篇 |
2020年 | 5261篇 |
2019年 | 6119篇 |
2018年 | 6566篇 |
2017年 | 7371篇 |
2016年 | 7405篇 |
2015年 | 8626篇 |
2014年 | 9858篇 |
2013年 | 12619篇 |
2012年 | 10729篇 |
2011年 | 11235篇 |
2010年 | 10253篇 |
2009年 | 9839篇 |
2008年 | 9394篇 |
2007年 | 8664篇 |
2006年 | 8591篇 |
2005年 | 7457篇 |
2004年 | 5511篇 |
2003年 | 4933篇 |
2002年 | 4504篇 |
2001年 | 4224篇 |
2000年 | 4194篇 |
1999年 | 4089篇 |
1998年 | 3291篇 |
1997年 | 2869篇 |
1996年 | 2517篇 |
1995年 | 2098篇 |
1994年 | 1713篇 |
1993年 | 1346篇 |
1992年 | 1052篇 |
1991年 | 830篇 |
1990年 | 687篇 |
1989年 | 584篇 |
1988年 | 443篇 |
1987年 | 364篇 |
1986年 | 272篇 |
1985年 | 219篇 |
1984年 | 138篇 |
1983年 | 119篇 |
1982年 | 97篇 |
1981年 | 86篇 |
1980年 | 78篇 |
1979年 | 53篇 |
1978年 | 43篇 |
1977年 | 49篇 |
1976年 | 70篇 |
1975年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
Physical Stability of Octenyl Succinate–Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems 下载免费PDF全文
The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications. 相似文献
56.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献
57.
We show that in the presence of magnetic field, two superconducting phases with the center-of-mass momentum of Cooper pair parallel to the magnetic field are induced in Dresselhaus spin–orbit-coupled superconductor. Specifically, at small magnetic field, the center-of-mass momentum is induced due to the energy-spectrum distortion and no unpairing region with vanishing singlet correlation appears. We refer to this superconducting state as the drift-BCS state. By further increasing the magnetic field, the superconducting state falls into the Fulde–Ferrell state with the emergence of the unpairing regions. The observed abrupt enhancement of the center-of-mass momenta and suppression on the order parameters during the transition indicate the occurrence of a first-order phase transition. Enhanced Pauli limit and hence enlarged magnetic-field regime of the Fulde–Ferrell state, due to the spin-flip terms of the spin–orbit coupling, are revealed. We also address the triplet correlations induced by the spin–orbit coupling, and show that the Cooper-pair spin polarizations, generated by the magnetic field and center-of-mass momentum with the triplet correlations exhibit totally different magnetic-field dependences between the drift-BCS and Fulde–Ferrell states. 相似文献
58.
59.
Based on the phase transformation theories, especially the T0 concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm. 相似文献