全文获取类型
收费全文 | 132783篇 |
免费 | 16469篇 |
国内免费 | 8688篇 |
专业分类
电工技术 | 6461篇 |
技术理论 | 3篇 |
综合类 | 10433篇 |
化学工业 | 33089篇 |
金属工艺 | 15300篇 |
机械仪表 | 8261篇 |
建筑科学 | 9268篇 |
矿业工程 | 3637篇 |
能源动力 | 3251篇 |
轻工业 | 11635篇 |
水利工程 | 2392篇 |
石油天然气 | 3099篇 |
武器工业 | 1745篇 |
无线电 | 6943篇 |
一般工业技术 | 24301篇 |
冶金工业 | 5892篇 |
原子能技术 | 557篇 |
自动化技术 | 11673篇 |
出版年
2024年 | 914篇 |
2023年 | 2878篇 |
2022年 | 4471篇 |
2021年 | 5448篇 |
2020年 | 5414篇 |
2019年 | 4517篇 |
2018年 | 4838篇 |
2017年 | 5698篇 |
2016年 | 6086篇 |
2015年 | 6295篇 |
2014年 | 8014篇 |
2013年 | 8951篇 |
2012年 | 9585篇 |
2011年 | 10487篇 |
2010年 | 7525篇 |
2009年 | 7903篇 |
2008年 | 6918篇 |
2007年 | 8157篇 |
2006年 | 7473篇 |
2005年 | 6004篇 |
2004年 | 5272篇 |
2003年 | 4459篇 |
2002年 | 3670篇 |
2001年 | 2943篇 |
2000年 | 2623篇 |
1999年 | 2018篇 |
1998年 | 1722篇 |
1997年 | 1456篇 |
1996年 | 1149篇 |
1995年 | 1006篇 |
1994年 | 796篇 |
1993年 | 582篇 |
1992年 | 529篇 |
1991年 | 390篇 |
1990年 | 411篇 |
1989年 | 400篇 |
1988年 | 178篇 |
1987年 | 121篇 |
1986年 | 87篇 |
1985年 | 102篇 |
1984年 | 111篇 |
1983年 | 62篇 |
1982年 | 84篇 |
1981年 | 17篇 |
1980年 | 63篇 |
1979年 | 30篇 |
1978年 | 12篇 |
1974年 | 8篇 |
1959年 | 8篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
102.
Linear-viscoelastic characteristics and performance are evaluated throughout the blending process of polyethylene and polypropylene with bitumen. Results indicate that type, form and percentage of polyolefin play a significant role in the time evolution of the composite's mechanical response. Toluene extraction of modified bitumen revealed, for the first time, the formation of a sponge-like polymer network. Visual inspection and Fourier transform infrared analysis of the polyolefins recovered after extraction indicates higher affinity of the polyethylene with bitumen in agreement with the rheological test results. The use of polypropylene is discouraged if rutting performance is a concern, and polyethylene in both pellets and powder form at 4%, and after 210 min of blending produces a modified bitumen with acceptable performance. 相似文献
103.
A new strategy for the selective coating of tin sulfide (SnS) on the surface of moth‐eye patterned (MEP) conducting polymer film is studied by considering the optical properties of the antireflective moth‐eye pattern and flexibility of polymer films. The semiconductor SnS is selectively coated on the surface of MEP microdomes of poly(3,4‐ethylenedioxythiophene) poly(styrene‐sulfonate) (PEDOT:PSS) film. The SnS coated MEP film is obtained by using pore selectively SnS thin layer functionalized polystyrene honeycomb‐patterned porous (HCP) film as a template. Aqueous PEDOT:PSS solution is poured on the SnS functionalized HCP films and detached for the fabrication of SnS coated MEP films. The films show a satisfactory photo‐responsive property under solar stimulated light illumination due to the antireflective MEP structure of PEDOT film and homogenous SnS coating on the surface of the conducting polymer. 相似文献
104.
Environmental concerns continue to pose the challenge to replace petroleum-based products with renewable ones completely or at least partially while maintaining comparable properties. Herein, rigid polyurethane (PU) foams were prepared using soy-based polyol for structural and thermal insulation applications. Cell size, density, thermal resistivity, and compression force deflection (CFD) values were evaluated and compared with that of petroleum-based PU foam Baydur 683. The roles of different additives, that is, catalyst, blowing agent, surfactants, and different functionalities of polyol on the properties of fabricated foam were also investigated. For this study, dibutyltin dilaurate was employed as catalyst and water as environment friendly blowing agent. Their competitive effect on density and cell size of the PU foams were evaluated. Five different silicone-based surfactants were employed to study the effect of surface tension on cell size of foam. It was also found that 5 g of surfactant per 100 g of polyol produced a foam with minimum surface tension and highest thermal resistivity (R value: 26.11 m2·K/W). However, CFD values were compromised for higher surfactant loading. Additionally, blending of 5 g of higher functionality soy-based polyol improved the CFD values to 328.19 kPa, which was comparable to that of petroleum-based foam Baydur 683. 相似文献
105.
106.
Sonika Sahu Mohd. Zahid Ansari Dehi Pada Mondal Chongdu Cho 《Materials Science & Technology》2019,35(7):856-864
In this paper, cenosphere particles embedded in AA2014 aluminium matrix are used to fabricate syntactic foam by stir casting method. The particle size is about 100?µm and foam density is about 1990?kg?m?3. Compression tests at strain rate 0.001/s are performed on foam samples to characterise their mechanical properties which are then used in numerical analysis on commercial finite element analysis software ABAQUS/CAE with isotropic elastic-plastic material model. Experimental and numerical results show good conformity in deformation behaviour with elastic and plateau zones showing average deviations less than 5% and 20%, respectively. Foams showed high yield stress and energy absorption capabilities that can be useful in making blast and impact resistant structures. 相似文献
107.
Thandi Patricia Gumede 《乙烯基与添加剂工艺杂志》2021,27(3):469-484
This review paper deals with the overall crystallization behavior of polyethylene/wax blends as phase change materials (PCMs) for thermal energy storage with the determination of their thermal properties. The addition of molten wax to the polyethylenes decreases the crystallization and melting temperatures of the blends. However, incorporating fillers to the polyethylene/wax blends can either decrease or increase the crystallization and melting temperatures of the composites depending on the filler type. The normalized enthalpy values of linear low-density polyethylene showed no significant change when increasing the wax content. On the contrary, the normalized enthalpy values of the wax in the blends were lesser than that of pure wax and increased with increasing wax content. Since the wax in the blend had a lower crystallinity compared to pure wax, this influences its effectiveness as a PCM for thermal energy storage. The effect of different polyethylenes on the wax morphology gave rise to enhance phase separation when wax was blended to high-density polyethylene as compared to the other polyethylenes. On the contrary, the effect of various waxes on the morphology of polyethylene resulted in different morphologies due to the molecular weight of the wax used and the structure of the polyethylene chain. The addition of fillers to the polyethylene (PE)/wax samples resulted in enhanced phase separation. The overall isothermal crystallization rate and the equilibrium melting temperature of PEs in the PEs/wax blends were depressed by wax addition due to the wax dilution effect. 相似文献
108.
109.
《Ceramics International》2020,46(15):23695-23705
Solid electrolytes are the key component in designing all-solid-state batteries. The Li1.3Al0.3Ti1.7(PO4)3 (LATP) structure and its derivatives obtained by doping various elements at Ti and Al site acts as good solid electrolytes. However, there is still scope for enhancing the ionic conductivity using simple precursors and preparation methods. In this study, the Li superionic conductors Li1.3Al0.3Ti1.7-xZrx(PO4)3 (LATZP) with 0 ≤ x ≤ 0.2 have been successfully prepared by the solid-state reaction route. The structural, morphological, and ionic transport properties were analyzed using several experimental techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy (IS). The presence of two relaxation processes corresponding to grain and grain boundary was studied using various formalisms. We have observed that grain effects dominate at lower temperatures (<100 °C) while the grain boundary at higher temperatures (> 200 °C) on ionic conductivity. The relaxation mechanisms of grain and grain boundaries were investigated by the Summerfield scaling of AC conductivity. The highest total ionic conductivity of 2.48 × 10-4 S/cm at 150 °C and 5.50 × 10-3 S/cm at 250 °C was obtained for x = 0.1 in Li1.3Al0.3Ti1.6Zr0.1(PO4)3 sintered at 950 °C/6 h in the air. The ionic conductivity value was found to be higher than the ionic conductivity reported for LATP prepared via solid-state reaction mechanism using the same precursors and conditions. 相似文献
110.
Huimin Zhao Wensi Wang Yunmei Du Yu Yang Minghui Wang Shaoxiang Li Ruixin Chen Yanru Liu Lei Wang 《International Journal of Hydrogen Energy》2021,46(18):10763-10772
In this work, we synthesized Se doped MoS2@Ni3S2 with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS2@Ni3S2 (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe2 successfully formed on the edge of MoS2 nanosheets and particle Ni3S2 transformed into NiSe, in which MoSe2 and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm?2, and has a low Tafel plots of 72.77 mV dec?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy. 相似文献