全文获取类型
收费全文 | 6145篇 |
免费 | 399篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 128篇 |
综合类 | 4篇 |
化学工业 | 1421篇 |
金属工艺 | 240篇 |
机械仪表 | 400篇 |
建筑科学 | 114篇 |
矿业工程 | 2篇 |
能源动力 | 348篇 |
轻工业 | 518篇 |
水利工程 | 23篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 968篇 |
一般工业技术 | 1480篇 |
冶金工业 | 302篇 |
原子能技术 | 66篇 |
自动化技术 | 543篇 |
出版年
2024年 | 6篇 |
2023年 | 77篇 |
2022年 | 104篇 |
2021年 | 172篇 |
2020年 | 154篇 |
2019年 | 144篇 |
2018年 | 198篇 |
2017年 | 194篇 |
2016年 | 219篇 |
2015年 | 162篇 |
2014年 | 272篇 |
2013年 | 368篇 |
2012年 | 449篇 |
2011年 | 526篇 |
2010年 | 368篇 |
2009年 | 419篇 |
2008年 | 371篇 |
2007年 | 305篇 |
2006年 | 234篇 |
2005年 | 225篇 |
2004年 | 188篇 |
2003年 | 166篇 |
2002年 | 169篇 |
2001年 | 140篇 |
2000年 | 133篇 |
1999年 | 108篇 |
1998年 | 143篇 |
1997年 | 120篇 |
1996年 | 86篇 |
1995年 | 72篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有6565条查询结果,搜索用时 31 毫秒
951.
Orthorhombic‐pseudocubic phase transition and piezoelectric properties of (Na0.5K0.5)(Nb1−xSbx)‐SrZrO3 ceramics
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ku‐Tak Lee Dae‐Hyeon Kim Jong‐Seong Park Tae‐Gon Lee Sung‐Hoon Cho Su‐Jin Park Jong‐Yoon Kang Sahn Nahm 《Journal of the American Ceramic Society》2017,100(10):4827-4835
0.96(Na0.5K0.5)(Nb1?xSbx)‐0.04SrZrO3 ceramics with 0.0≤x≤0.06 were well sintered at 1060°C for 6 hours without a secondary phase. Orthorhombic‐tetragonal transition temperature (TO‐T) and Curie temperature (TC) decreased with the addition of Sb2O5. The decrease in TC was considerable compared to that in TO‐T, and thus the tetragonal phase zone disappeared when x exceeded 0.03. Therefore, a broad peak for orthorhombic‐pseudocubic transition as opposed to that for orthorhombic‐tetragonal transition appeared at 115°C‐78.2°C for specimens with 0.04≤x≤0.06. An orthorhombic structure was observed for specimens with x≤0.03. However, the polymorphic phase boundary structure containing orthorhombic and pseudocubic structures was formed for the specimens 0.04≤x≤0.06. Furthermore, a specimen with x=0.055 exhibited a large piezoelectric strain constant of 325 pC/N, indicating that the coexistence of orthorhombic and pseudocubic structures could improve the piezoelectric properties of (Na0.5K0.5)NbO3‐based lead‐free piezoelectric ceramics. 相似文献
952.
The vibro-acoustic characteristics of an automotive brake drum is studied by applying a hybrid approach, which combines a numerical vibration analysis with an analytical acoustic solution. Specifically, structural vibration of a drum is investigated with the numerical finite element analysis, and vibratory displacements of the outer surface of the drum is approximated by simple mathematical expressions. Then, radiation of sound from the drum vibration is calculated using well-known theoretical solutions based on the simplified modal displacements. Finally, the calculation results are compared with those obtained by full numerical analyses. The results show that the numerical-analytical hybrid method allows relatively accurate calculation of vibro-acoustic properties of a brake drum under realistic boundary conditions. 相似文献
953.
Sung Kim Ung-Been Jeong Kyoung-Yong Lee Jin-Hyuk Kim Joon-Yong Yoon Young-Seok Choi 《Journal of Mechanical Science and Technology》2017,31(11):5099-5106
During design optimization, the impeller and diffuser of a mixed-flow pump are generally optimized separately. In such cases, the total head can be overdesigned. In this study, the designs of the impeller and diffuser were optimized simultaneously by using computational fluid dynamics and the Response surface method (RSM). Design variables were defined according to the vane plane development of the impeller and diffuser. Three-dimensional Reynolds-averaged Navier–Stokes equations for the shear stress transport turbulence model were discretized by finite volume approximations and solved on hexahedral grids to analyze the flow in the pump. The total head and total efficiency were selected as objective functions, with four design variables related to the impeller outlet angles and diffuser inlet angles used for optimization. The RSM was constructed based on the objective functions with design points generated from the central composite method. The hydraulic performance of the optimum model was analyzed. 相似文献
954.
Young H. Kwon Sejoon Lee Woochul Yang Chang-Soo Park Im Taek Yoon 《Journal of Electronic Materials》2017,46(7):3917-3921
The effect of Mn was investigated in a synthesized multilayer system made up of five layers of InMnGaAs/GaAs quantum well (QW) grown on semi-insulating (100)-oriented substrates prepared by low-temperature molecular beam epitaxy. Magnetic moment measurements on a superconducting quantum interference device magnetometer revealed the presence of ferromagnetism with a Curie temperature above room temperature in a five-layer InGaMnAs/GaAs QW structure in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements powerfully confirmed the second phase founding of ferromagnetic GaMn and MnAs clusters. The ferromagnetism existing in five layers of InMnGaAs/GaAs QW is not intrinsic, but extrinsic due to the presence of Mn dopant clusters such as GaMn and MnAs clusters. 相似文献
955.
Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Minji Ko Hee Chang Yoon Heeyeon Yoo Ji Hye Oh Heesun Yang Young Rag Do 《Advanced functional materials》2017,27(4)
Highly efficient bright green‐emitting Zn?Ag?In?S (ZAIS)/Zn?In?S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn?Cu?In?S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W?1 and excellent color qualities (color rendering index (CRI, Ra) = 95 and the special CRI for red (R9) = 93) at 2700 K. 相似文献
956.
In this work, a structurable gel‐polymer electrolyte (SGPE) with a controllable pore structure that is not destroyed after immersion in an electrolyte is produced via a simple nonsolvent induced phase separation (NIPS) method. This study investigates how the regulation of the nonsolvent content affects the evolving nanomorphology of the composite separators and overcomes the drawbacks of conventional separators, such as glass fiber (GF), which has been widely used in sodium ion batteries (SIBs), through the regulation of pore size and gel‐polymer position. The interfacial resistance is reduced through selective positioning of a poly(vinylidene fluoride‐co‐hexa fluoropropylene) (PVdF‐HFP) gel‐polymer with the aid of NIPS, which in turn enhances the compatibility between the electrolyte and electrode. In addition, the highly porous morphology of the GF/SGPE obtained via NIPS allows for the absorption of more liquid electrolyte. Thus, a greatly improved cell performance of the SIBs is observed when a tailored SGPE is incorporated into the GF separator through charge/discharge testing compared with the performance observed with pristine GF and conventional GF coated with PVdF‐HFP gel‐polymer. 相似文献
957.
Virus‐Templated Self‐Mineralization of Ligand‐Free Colloidal Palladium Nanostructures for High Surface Activity and Stability
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Insu Kim Kyungnam Kang Mi Hwa Oh Moon Young Yang Inkyu Park Yoon Sung Nam 《Advanced functional materials》2017,27(48)
In solution‐based synthesis of colloidal nanostructures, additions of ligands, stabilizers, and redox reagents are generally required to obtain desirable structures, though ligands and stabilizers on the surface of nanostructures can substantially affect the surface‐related activity. Accordingly, an extensive rinsing process is usually required to remove residual reagents and stabilizers. This study reports a spontaneous self‐biomineralization of palladium (Pd) ions on a filamentous virus to form ligand‐free Pd nanowires under ambient conditions. No reducing reagents or additional surface stabilizers are used; the genetically modified virus alone supports the polycrystalline Pd nanowires within the nanostructure, maintaining the clean surface even without a rinsing process. The advantage of the ligand‐free Pd nanowires is found in the Suzuki‐coupling reaction, in which the nanowire catalytic activity is maintained after repeated reactions, while conventional Pd colloids undergo surface contamination by the stabilizer and lose their catalytic activity during repeated uses. The ligand‐free surface, high electronic connectivity, and structural stability of the Pd nanowires also allow high sensitivity and selectivity in hydrogen gas sensing analysis. This work emphasizes the importance of the ligand‐free surface of biotemplated nanostructures in maintaining functionalities without surface contamination. 相似文献
958.
959.
Phototransistors: High‐Performance UV–Vis–NIR Phototransistors Based on Single‐Crystalline Organic Semiconductor–Gold Hybrid Nanomaterials (Adv. Funct. Mater. 6/2017)
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
960.
The adsorption of three estrogenic compounds (bisphenol A (BPA), 17beta-estradiol (E2), and 17alpha-ethynyl estradiol (EE2)) on several powdered activated carbons (PAC) was investigated. Without preconcentration, method detection limits (MDL) using high-performance liquid chromatography (HPLC) with fluorescence detection at an excitation wavelength of 280 nm and an emission wavelength of 310 nm were 0.88, 1.15, and 0.96 nM for BPA, E2, and EE2, respectively. Compound recoveries were >90% in raw drinking water matrices. PAC screening studies (six PAC brands) indicated all three compounds were removed by PAC, but the percentage removal ranged from 31% to >99% based upon PAC type/dosage and presence/absence of natural organic matter. The order of removal (E2>EE2>BPA) corresponded with logK(ow) values for the compounds (3.1-4.0, 3.7-3.9, 3.3, respectively). Kinetic and PAC dose-response experiments were conducted with the two best performing PACs. Increasing contact time and PAC dose improved compound removal. Freundlich isotherm parameters were fit to the experimental data. This study confirms that PAC treatment is feasible for >99% removal of three estrogenic compounds from raw drinking waters that may be at risk for containing such compounds, at least at initial concentration of 500 ng/l and higher. 相似文献