全文获取类型
收费全文 | 410596篇 |
免费 | 42474篇 |
国内免费 | 15589篇 |
专业分类
电工技术 | 21583篇 |
技术理论 | 57篇 |
综合类 | 23645篇 |
化学工业 | 78428篇 |
金属工艺 | 21469篇 |
机械仪表 | 24828篇 |
建筑科学 | 30729篇 |
矿业工程 | 12251篇 |
能源动力 | 11599篇 |
轻工业 | 30190篇 |
水利工程 | 6648篇 |
石油天然气 | 24759篇 |
武器工业 | 3053篇 |
无线电 | 47626篇 |
一般工业技术 | 54082篇 |
冶金工业 | 20705篇 |
原子能技术 | 3763篇 |
自动化技术 | 53244篇 |
出版年
2024年 | 1538篇 |
2023年 | 5932篇 |
2022年 | 10333篇 |
2021年 | 14513篇 |
2020年 | 12338篇 |
2019年 | 11714篇 |
2018年 | 13072篇 |
2017年 | 14705篇 |
2016年 | 13916篇 |
2015年 | 17585篇 |
2014年 | 21669篇 |
2013年 | 26538篇 |
2012年 | 26018篇 |
2011年 | 28428篇 |
2010年 | 25067篇 |
2009年 | 24089篇 |
2008年 | 23188篇 |
2007年 | 22319篇 |
2006年 | 22632篇 |
2005年 | 19741篇 |
2004年 | 13339篇 |
2003年 | 11791篇 |
2002年 | 10771篇 |
2001年 | 9807篇 |
2000年 | 9890篇 |
1999年 | 10670篇 |
1998年 | 8538篇 |
1997年 | 7097篇 |
1996年 | 6622篇 |
1995年 | 5517篇 |
1994年 | 4546篇 |
1993年 | 3236篇 |
1992年 | 2585篇 |
1991年 | 2050篇 |
1990年 | 1565篇 |
1989年 | 1277篇 |
1988年 | 1056篇 |
1987年 | 715篇 |
1986年 | 563篇 |
1985年 | 356篇 |
1984年 | 257篇 |
1983年 | 218篇 |
1982年 | 214篇 |
1981年 | 137篇 |
1980年 | 139篇 |
1979年 | 80篇 |
1978年 | 43篇 |
1977年 | 49篇 |
1976年 | 69篇 |
1975年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Efficacy of Crude and Purified Chitinases (SsChi50) Extracted from Offal Red Scorpion Fish in Biological Control of Chickpea Weevil (Callosobruchus maculatus L.)
下载免费PDF全文
![点击此处可从《Journal of Food Processing and Preservation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
103.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
104.
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth. 相似文献
105.
Qingna Gong Songtao Cao Yu Zhou Ruixin Wang Weizhou Jiao 《International Journal of Hydrogen Energy》2021,46(41):21442-21453
Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g?1 h?1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles. 相似文献
106.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
107.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
108.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
109.
红外偏振光治疗仪是一种将红外技术与电子技术应用到医学领域的康复理疗设备,主要用于软组织损伤和慢性疼痛的康复治疗,已在医院得到了推广使用。然而,现有医院使用的台式治疗仪由于体积大、售价高等特点,不方便居家使用。为了开发体积小、售价低、家庭可用的红外偏振光治疗仪,满足家用市场的潜在需求,本文提出了一种新的便携手持式红外偏振光治疗仪,并开发了该智能控制系统。本文首先介绍了一种新的家用手持式治疗仪应具备的特点和关键技术指标,在此基础上设计了手持式治疗仪的硬件总体方案和软件架构,简要介绍了该治疗仪的一些关键技术,最终实现了治疗仪样机的研制。为了验证该样机的性能,本文通过大量的测试,结果表明,研制的手持式红外偏振光治疗仪在关键参数指标上达到了医院同类产品的水平,能够很好地满足家用的需求,具有良好的市场前景。 相似文献
110.
Wang Yunfei Zheng Wang Zhang Xiaofei Shen Jinqing 《Multidimensional Systems and Signal Processing》2020,31(3):907-926
Multidimensional Systems and Signal Processing - Generalized coprime structure decomposes the interleaved subarrays in the conventional coprime array by introducing a displacement and the resulting... 相似文献