全文获取类型
收费全文 | 356691篇 |
免费 | 29924篇 |
国内免费 | 15927篇 |
专业分类
电工技术 | 21690篇 |
技术理论 | 33篇 |
综合类 | 23962篇 |
化学工业 | 58757篇 |
金属工艺 | 20998篇 |
机械仪表 | 23407篇 |
建筑科学 | 29091篇 |
矿业工程 | 11707篇 |
能源动力 | 10037篇 |
轻工业 | 22655篇 |
水利工程 | 6675篇 |
石油天然气 | 23004篇 |
武器工业 | 3127篇 |
无线电 | 39443篇 |
一般工业技术 | 40346篇 |
冶金工业 | 17726篇 |
原子能技术 | 3751篇 |
自动化技术 | 46133篇 |
出版年
2024年 | 1543篇 |
2023年 | 5618篇 |
2022年 | 9958篇 |
2021年 | 14022篇 |
2020年 | 10603篇 |
2019年 | 8804篇 |
2018年 | 9961篇 |
2017年 | 11241篇 |
2016年 | 9899篇 |
2015年 | 13942篇 |
2014年 | 17477篇 |
2013年 | 20525篇 |
2012年 | 22723篇 |
2011年 | 24569篇 |
2010年 | 21704篇 |
2009年 | 20756篇 |
2008年 | 20430篇 |
2007年 | 19622篇 |
2006年 | 20280篇 |
2005年 | 17634篇 |
2004年 | 11902篇 |
2003年 | 10686篇 |
2002年 | 10788篇 |
2001年 | 9404篇 |
2000年 | 8794篇 |
1999年 | 9550篇 |
1998年 | 7393篇 |
1997年 | 6258篇 |
1996年 | 5821篇 |
1995年 | 4824篇 |
1994年 | 4011篇 |
1993年 | 2796篇 |
1992年 | 2282篇 |
1991年 | 1715篇 |
1990年 | 1247篇 |
1989年 | 999篇 |
1988年 | 797篇 |
1987年 | 557篇 |
1986年 | 418篇 |
1985年 | 272篇 |
1984年 | 192篇 |
1983年 | 124篇 |
1982年 | 142篇 |
1981年 | 102篇 |
1980年 | 80篇 |
1979年 | 37篇 |
1978年 | 4篇 |
1965年 | 2篇 |
1959年 | 17篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
油液监测是判断设备健康状况和提供设备故障隐患预警的有效方法。综述了用于监测润滑油中磨损颗粒的最新各类在线传感器的基本原理,包括批量磁吸附式传感器、微流体电容传感器、金属扫描传感器、双层平面线圈传感器、超声波传感器和光学传感器等,并讨论各种传感方法的优缺点以及未来发展面临的挑战;指出了高通量、高灵敏度、能区别金属与非金属磨粒、可采集磨粒图像信息的集成式传感器是未来研究的重点,集成式、智能化、无线传输的传感器是未来研发方向。 相似文献
2.
3.
4.
Shanshan Zhuang Wenxiong Zheng Yunong Na Naiyi Chen Fan Gong Bingxuan Huang Stephen Brennan Charles Congyi Liu Jian Cheng Lukai Ma Huifan Liu 《International Journal of Food Science & Technology》2022,57(2):1093-1103
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results. 相似文献
5.
Peng Wang Yan Li Yujiao Qu Baowei Wang Jingxin Sun Chunwei Miao Ming Huang He Huang Congxiang Zhang 《International Journal of Food Science & Technology》2022,57(6):3428-3439
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP. 相似文献
6.
Sinan Zhang Yadonga Zhao Xueshuang Yao Zhenhong Zheng Chuyao Zheng Zhuo Jiang 《International Journal of Food Science & Technology》2022,57(7):4245-4253
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing. 相似文献
7.
Mengru Liu Weihai Zhang Limin Ma 《International Journal of Adaptive Control and Signal Processing》2022,36(1):69-87
The article investigates the finite-time adaptive fuzzy control for a class of nonlinear systems with output constraint and input dead-zone. First, by skillfully combining the barrier Lyapunov function, backstepping design method, and finite-time control theory, a novel adaptive state-feedback tracking controller is constructed, and the output constraint of the nonlinear system is not violated. Second, the fuzzy logic system is used to approximate unknown function in the nonlinear system. Third, the finite-time command filter is introduced to avoid the problem of “complexity explosion” caused by repeated differentiations of the virtual control signal in conventional backstepping control schemes. Meanwhile, a new saturation function is added in the compensating signal for filter error to improve control accuracy. Finally, based on Lyapunov stability analysis, all the signals of the closed-loop are proved to be semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood region of the origin in a finite time. A simulation example is presented to demonstrate the effectiveness for the proposed control scheme. 相似文献
8.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
9.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献
10.
Neural Processing Letters - The boundedness and the global Mittag-Leffler synchronization (GMLS) of fractional-order inertial Cohen–Grossberg neural networks (CGNNS) with time delays are... 相似文献