全文获取类型
收费全文 | 270064篇 |
免费 | 31016篇 |
国内免费 | 9495篇 |
专业分类
电工技术 | 13501篇 |
技术理论 | 24篇 |
综合类 | 15270篇 |
化学工业 | 55351篇 |
金属工艺 | 13958篇 |
机械仪表 | 15614篇 |
建筑科学 | 19695篇 |
矿业工程 | 7751篇 |
能源动力 | 7666篇 |
轻工业 | 20445篇 |
水利工程 | 4058篇 |
石油天然气 | 16863篇 |
武器工业 | 1682篇 |
无线电 | 31898篇 |
一般工业技术 | 37969篇 |
冶金工业 | 13702篇 |
原子能技术 | 2312篇 |
自动化技术 | 32816篇 |
出版年
2024年 | 995篇 |
2023年 | 3803篇 |
2022年 | 6492篇 |
2021年 | 9291篇 |
2020年 | 8352篇 |
2019年 | 8825篇 |
2018年 | 9523篇 |
2017年 | 10641篇 |
2016年 | 10349篇 |
2015年 | 12578篇 |
2014年 | 14916篇 |
2013年 | 17972篇 |
2012年 | 16777篇 |
2011年 | 17647篇 |
2010年 | 15940篇 |
2009年 | 15102篇 |
2008年 | 14402篇 |
2007年 | 13742篇 |
2006年 | 14070篇 |
2005年 | 12141篇 |
2004年 | 9037篇 |
2003年 | 8664篇 |
2002年 | 8549篇 |
2001年 | 7478篇 |
2000年 | 7017篇 |
1999年 | 7118篇 |
1998年 | 5489篇 |
1997年 | 4498篇 |
1996年 | 4211篇 |
1995年 | 3519篇 |
1994年 | 2839篇 |
1993年 | 1981篇 |
1992年 | 1551篇 |
1991年 | 1244篇 |
1990年 | 945篇 |
1989年 | 745篇 |
1988年 | 545篇 |
1987年 | 344篇 |
1986年 | 285篇 |
1985年 | 201篇 |
1984年 | 142篇 |
1983年 | 117篇 |
1982年 | 124篇 |
1981年 | 101篇 |
1980年 | 72篇 |
1979年 | 39篇 |
1978年 | 28篇 |
1977年 | 22篇 |
1976年 | 36篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
32.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
33.
Cerebral microbleeds and cognitive decline in a hemodialysis patient: Case report and review of literature 下载免费PDF全文
Lin Li Mark Fisher Wei‐Ling Lau Hamid Moradi Alexander Cheung Gaby Thai Jason Handwerker Kamyar Kalantar‐Zadeh 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(3):E1-E7
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients. 相似文献
34.
35.
36.
37.
38.
Joon‐Young Jun Sosuke Nakajima Koji Yamazaki Yuji Kawai Hajime Yasui Yasuyuki Konishi 《International Journal of Food Science & Technology》2015,50(4):871-877
Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria. 相似文献
39.
40.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献