首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   497766篇
  免费   34472篇
  国内免费   17934篇
电工技术   25121篇
技术理论   64篇
综合类   29888篇
化学工业   80108篇
金属工艺   27946篇
机械仪表   29650篇
建筑科学   34994篇
矿业工程   13935篇
能源动力   13164篇
轻工业   31703篇
水利工程   8420篇
石油天然气   27495篇
武器工业   3550篇
无线电   54419篇
一般工业技术   63114篇
冶金工业   24010篇
原子能技术   4452篇
自动化技术   78139篇
  2024年   1586篇
  2023年   6402篇
  2022年   11677篇
  2021年   16124篇
  2020年   12653篇
  2019年   10171篇
  2018年   24152篇
  2017年   24947篇
  2016年   20600篇
  2015年   16552篇
  2014年   20996篇
  2013年   25009篇
  2012年   29761篇
  2011年   38352篇
  2010年   33460篇
  2009年   29646篇
  2008年   30567篇
  2007年   30561篇
  2006年   24013篇
  2005年   21754篇
  2004年   14603篇
  2003年   12951篇
  2002年   11463篇
  2001年   9942篇
  2000年   10094篇
  1999年   11299篇
  1998年   9331篇
  1997年   7674篇
  1996年   7167篇
  1995年   5931篇
  1994年   4867篇
  1993年   3416篇
  1992年   2794篇
  1991年   2174篇
  1990年   1617篇
  1989年   1334篇
  1988年   1077篇
  1987年   692篇
  1986年   554篇
  1985年   344篇
  1984年   238篇
  1983年   210篇
  1982年   205篇
  1981年   144篇
  1980年   150篇
  1979年   76篇
  1976年   57篇
  1965年   51篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 294 毫秒
71.
In this study, the effect of high-intensity ultrasound (HIUS) (200 and 400 W for 0, 5, 10 and 15 min respectively) on conformational changes, physicochemical, rheological and emulsifying properties of scallop (Patinopecten yessoensis) myofibrillar protein (SMP) was investigated. HIUS-treated SMP had lower α-helix content and higher β-sheet content compared with the native SMP. HIUS treatment induced the unfolding of SMP and increased the surface hydrophobicity. The particle size of SMP decreased and the absolute zeta-potential increased after ultrasonication, which in turn increased the solubility of SMP. The conformational changes and the improvement of physicochemical properties of SMP increased the ability for SMP to lower the interfacial tension at the oil–water interface and increased the percentage of adsorbed protein. As a result, the emulsifying properties, rheological properties of SMP and storage stability of emulsions were also improved. In conclusion, HIUS treatment has future potential for improving the emulsifying properties of SMP.  相似文献   
72.
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy.  相似文献   
73.
Li  Yuru  Wang  Fei  Zheng  Zhaowen 《Neural Processing Letters》2022,54(4):3141-3156
Neural Processing Letters - This paper presents an approach to identify the unknown parameters of genetic regulatory network (GRN) in finite-time. The adaptive synchronization-based method is used...  相似文献   
74.
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs.  相似文献   
75.
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation.  相似文献   
76.
International Journal of Control, Automation and Systems - The vibration control problem of offshore jacket platforms is studied. The model of offshore platforms with nonlinear interactions of the...  相似文献   
77.
78.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs.  相似文献   
79.
Laminated Si3N4/SiCw ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si3N4/SiCw ceramics was 13.5 MPa m1/2, which was almost 1.6 times that of Si3N4/SiCw composite ceramics, namely 8.5 MPa m1/2. Moreover, the indentation strength of laminated Si3N4/SiCw ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si3N4/SiCw ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si3N4/SiCw ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work.  相似文献   
80.
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号