全文获取类型
收费全文 | 2306篇 |
免费 | 136篇 |
国内免费 | 90篇 |
专业分类
电工技术 | 99篇 |
综合类 | 138篇 |
化学工业 | 534篇 |
金属工艺 | 311篇 |
机械仪表 | 113篇 |
建筑科学 | 142篇 |
矿业工程 | 23篇 |
能源动力 | 128篇 |
轻工业 | 38篇 |
水利工程 | 37篇 |
石油天然气 | 68篇 |
武器工业 | 12篇 |
无线电 | 141篇 |
一般工业技术 | 394篇 |
冶金工业 | 76篇 |
原子能技术 | 30篇 |
自动化技术 | 248篇 |
出版年
2024年 | 2篇 |
2023年 | 58篇 |
2022年 | 37篇 |
2021年 | 62篇 |
2020年 | 83篇 |
2019年 | 68篇 |
2018年 | 80篇 |
2017年 | 76篇 |
2016年 | 81篇 |
2015年 | 57篇 |
2014年 | 97篇 |
2013年 | 144篇 |
2012年 | 94篇 |
2011年 | 153篇 |
2010年 | 109篇 |
2009年 | 114篇 |
2008年 | 123篇 |
2007年 | 141篇 |
2006年 | 115篇 |
2005年 | 109篇 |
2004年 | 88篇 |
2003年 | 86篇 |
2002年 | 87篇 |
2001年 | 67篇 |
2000年 | 54篇 |
1999年 | 48篇 |
1998年 | 41篇 |
1997年 | 32篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 26篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有2532条查询结果,搜索用时 31 毫秒
1.
Jinming Wang Meng Yang Guodong Zou Di Liu Qiuming Peng 《Advanced functional materials》2021,31(21):2101180
Lithium (Li) metal, as an appealing candidate for the next-generation of high-energy-density batteries, is plagued by its safety issue mainly caused by uncontrolled dendrite growth and infinite volume expansion. Developing new materials that can improve the performance of Li-metal anode is one of the urgent tasks. Herein, a new MXene derivative containing pure rutile TiO2 and N-doped carbon prepared by heat-treating MXene under a mixing gas, exhibiting high chemical activity in molten Li, is reported. The lithiation MXene derivative with a hybrid of LiTiO2-Li3N-C and Li offers outstanding electrochemical properties. The symmetrical cell assembling lithiation MXene derivative hybrid anode exhibits an ultra-long cycle lifespan of 2000 h with an overpotential of ≈30 mV at 1 mA cm−2, which overwhelms Li-based anodes reported so far. Additionally, long-term operations of 34, 350, and 500 h at 10 mA cm−2 can be achieved in symmetrical cells at temperatures of −10, 25, and 50 °C, respectively. Both experimental tests and density functional theory calculations confirm that the LiTiO2-Li3N-C skeleton serves as a promising host for Li infusion by alleviating volume variation. Simultaneously, the superlithiophilic interphase of Li3N guides Li deposition along the LiTiO2-Li3N-C skeleton to avoid dendrite growth. 相似文献
2.
3.
Ohjin Kwon Xiaoqian Cai Wentao Qu Feng Liu Jadwiga Szydłowska Ewa Gorecka Moon Jong Han Dong Ki Yoon Silvio Poppe Carsten Tschierske 《Advanced functional materials》2021,31(28):2102271
First examples of multichain (polycatenar) compounds, based on the π-conjugated [1]benzothieno[3,2-b]benzothiophene unit are designed, synthesized, and their soft self-assembly and charge carrier mobility are investigated. These compounds, terminated by the new fan-shaped 2-brominated 3,4,5-trialkoxybenzoate moiety, form bicontinuous cubic liquid crystalline (LC) phases with helical network structure over extremely wide temperature ranges (>200 K), including ambient temperature. Compounds with short chains show an achiral cubic phase with the double network, which upon increasing the chain length, is at first replaced by a tetragonal 3D phase and then by a mirror symmetry is broken triple network cubic phase. In the networks, the capability of bypassing defects provides enhanced charge carrier mobility compared to imperfectly aligned columnar phases, and the charge transportation is non-dispersive, as only rarely observed for LC materials. At the transition to a semicrystalline helical network phase, the conductivity is further enhanced by almost one order of magnitude. In addition, a mirror symmetry broken isotropic liquid phase is formed beside the 3D phases, which upon chain elongation is removed and replaced by a hexagonal columnar LC phase. 相似文献
4.
A. Robina P. Bechthold A. Juan C. Pistonesi M.E. Pronsato 《International Journal of Hydrogen Energy》2018,43(33):16085-16091
Density functional calculations were performed on Zr0.9Ti0.1(Ni0.5Cr0.5-xVx)2 Laves Phase, with x = 0, 0.125, 0.25, 0.375 and 0.5, in order to study its H absorption capacity. Binding energy, electronic structure and bonding were analyzed for the intermetallic compound with different V content and increasing amounts of hydrogen.The optimized geometry was found in good agreement with experimental data of the C14 Laves phase. Hydrogen locates preferentially in A2B2 tetrahedral sites in the AB2 matrix (A = Zr, Ti; B = Ni, Cr, V) but AB3 and B4sites are also stable. The volume of the intermetallic and the H binding energy increases with vanadium content. Theoretically H absorption is possible up to 4.5 H/F.U. but the strongest binding energy is achieved with 3 H/F. U.The main contribution to density of states is due to d states of all components of the structure and an H-metal bonding is observed in the range ?10 to ?4 eV. 相似文献
5.
C. S. Sravanthi 《亚洲传热研究》2020,49(1):86-102
The purpose of the present paper is to explore the second order slip effects on nanofluid flow over a vertical cone. The effects of nonlinear thermal radiation and nonuniform heat source/sink are also taken into account. Water with copper nanoparticles is used as nanofluid in this investigation. The governing partial differential equations for the flow are converted into ordinary differential equations by using transformations and then are solved using homotopy analysis method. The influence of various important parameters on velocity, temperature, skin‐friction, and Nusselt number are presented through graphs. Results indicate that the velocity and magnitude of skin friction decrease with a rise in first and second order velocity slips. A raise in either first or second order temperature jump causes a fall in temperature. Nonlinear radiation increases the more rapidly when compared to the linear radiation case. 相似文献
6.
Hydrogen storage properties of Mg98.5Gd1Zn0.5 and Mg98.5Gd0.5Y0.5Zn0.5 alloys containing LPSO phases
《International Journal of Hydrogen Energy》2021,46(65):32949-32961
In this work, the as-cast Mg-rich Mg98.5Gd1Zn0.5 and Mg98.5Gd0.5Y0.5Zn0.5 alloys are prepared by the semi-continuous casting method, and their hydrogen storage performance and catalytic mechanisms are investigated by experimental and first-principles calculations approaches. The results show that the LPSO phases decompose and in-situ form the RE(Gd/Y)Hx(x = 2,3) nano-hydrides upon hydrogenation. These nano-hydrides not only serve as the in-situ catalysts to promote the hydrogen ab/desorption of Mg matrix, but also present the pinning effect to inhibit the growth of Mg/MgH2 grains during hydrogenation and dehydrogenation. Comparatively, the two alloys exhibit the similar hydrogen absorption kinetics, while the hydrogen desorption kinetics of Mg98.5Gd1Zn0.5 is superior to that of Mg98.5Gd0.5Y0.5Zn0.5. The first-principles calculations reveal that the GdH2 and YH2 hydrides exhibit different catalytic effects on weakening the bond strength of H–H within H2 and Mg–H within MgH2, which interprets well the differences in the hydrogen ab/desorption kinetics between Mg98.5Gd1Zn0.5 and Mg98.5Gd0.5Y0.5Zn0.5 alloys. 相似文献
7.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
8.
《Journal of the European Ceramic Society》2020,40(4):1496-1504
In this study, Al2O3 workpieces were vacuum brazed by using Ni-45Ti binary alloy. The interfacial microstructure evolution of the joints obtained at different brazing temperatures was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The bonding strength of the joints was measured by shear testing. The results indicated that Ni2Ti4O and AlNi2Ti were the main reaction products in the joint areas. Moreover, the Ti2Ni intermetallic compound formed in the brazing seam. The typical layer structure of the brazed joints was Al2O3/AlNi2Ti/Ni2Ti4O/Ti2Ni + NiTi/Ni2Ti4O/AlNi2Ti/Al2O3. With the brazing temperature increasing, the thickness of the Ni2Ti4O reaction layer adjacent to the Al2O3 substrate increased significantly, while the AlNi2Ti phase had a tendency to dissolve with the brazing temperature increasing. The mechanism for the microstructure evolution was also discussed. The maximum shear strength of 125.63±4.87 MPa of the joints was obtained when brazed at 1350 °C for 30min. The fracture occurred hardly in the interface between Al2O3 and Ni-45Ti filler alloy. 相似文献
9.
《Ceramics International》2020,46(3):2654-2660
Brown fused alumina is a cost-effective alumina material, and the state of Ti in alumina has a great influence on its high-temperature performance. In this paper, the Ti-containing phases in brown fused alumina particles and Al-brown fused alumina refractory were successfully transformed into Ti(C,N) at 1973 K in flowing N2. The evolution of the Ti-containing phases in brown fused alumina under high temperature and nitrogen conditions was investigated by XRD, SEM and EDS. The results show that the Ti-containing phases in brown fused alumina include Ti2O3, Ti(C,N,O), TiFeSi2, Ca0·95Mg0·9Al10·1(Ti)O17 and a low-melting point Ca3Al2Si3(Mg,Ti)O12 phase. Under high temperature and nitrogen conditions, the TiO2[liquid], MgO[liquid] and SiO2[liquid] in the low-melting point phase are transformed into Ti(C,N), Mg(g) and SiO(g), while they are supplemented from Ti2O3, Ti(C,N,O) and Ca0·95Mg0·9Al10·1(Ti)O17. After heat treatment at 1973 K for 3 h, Ti2O3 and Ti(C,N,O) disappear, Ca0·95Mg0·9Al10·1(Ti)O17 is transformed into plate-like Ca0·55Al11O17.05, and Ti(C,N) is formed on the surface of the corundum particles. The formation of Ti(C,N) reduces the porosity of the brown fused alumina particles and increases their strength. 相似文献
10.
《Journal of the European Ceramic Society》2020,40(5):1820-1828
In this work, oxidation mechanisms were studied in fine-grained (FG) and coarse-grained (CG) Ti2AlC bulk samples. Results showed that the oxidation kinetics are controlled by the grain size of Ti2AlC. Bigger are the grains, faster is the oxidation. A dense and protective Al2O3 layer forms at the surface of FG-Ti2AlC samples while for the CG-Ti2AlC samples, a thick TiO2 layer forms on top of a discontinuous Al2O3. CG-Ti2AlC was observed to simultaneously transform into Ti3AlC2 and TiC instead of being directly transformed into TiC. This transformation result in the following crystallographically sandwich-like structure: (0001) Ti2AlC // (0001) Ti3AlC2 // (111) TiC. The volume shrinkage associated to this transformation produces elongated holes that are partially filled by α-Al2O3. The stress caused by the volume shrinkage generates cracks at the surface, which makes the oxygen inwards diffusion easier and thus worsens the oxidation resistance the CG-Ti2AlC bulk. 相似文献