全文获取类型
收费全文 | 1386篇 |
免费 | 11篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 255篇 |
金属工艺 | 21篇 |
机械仪表 | 7篇 |
建筑科学 | 7篇 |
能源动力 | 36篇 |
轻工业 | 17篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 64篇 |
一般工业技术 | 211篇 |
冶金工业 | 719篇 |
原子能技术 | 1篇 |
自动化技术 | 41篇 |
出版年
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 6篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 24篇 |
2011年 | 28篇 |
2010年 | 27篇 |
2009年 | 26篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 37篇 |
1998年 | 227篇 |
1997年 | 126篇 |
1996年 | 93篇 |
1995年 | 63篇 |
1994年 | 51篇 |
1993年 | 57篇 |
1992年 | 19篇 |
1991年 | 25篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 18篇 |
1976年 | 47篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 13篇 |
排序方式: 共有1397条查询结果,搜索用时 54 毫秒
1.
Wireless Personal Communications - Internet of Things (IoT) offers complex networks of connected devices, which are used to serve in the real-time environment. Interestingly, Wireless Sensor... 相似文献
2.
Composites comprising Poly(Methyl Methacrylate) (PMMA) and CaCu3Ti4O12 (CCTO) via melt mixing followed by hot pressing were fabricated. These were characterized using X‐ray diffraction, thermo gravimetric, scanning electron microscopy, and Impedance analyzer for their structural, morphology, and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. Theoretical models were employed to rationalize the dielectric behavior of these composites. At higher temperatures, the relaxation peak shifts to higher frequencies, due to the merging of both β and α relaxations into a single dielectric dispersion peak. The AC conductivity in the high frequency region was attributed to the electronic polarization. POLYM. ENG. SCI., 54:551–558, 2014. © 2013 Society of Plastics Engineers 相似文献
3.
Sreeraj Gopi Augustine Amalraj Karthik Varma Shintu Jude Prakash B. Reddy Chandradhara Divya 《国际聚合物材料杂志》2018,67(9):581-588
A phytogenic feed additive (PFA) formulation was prepared with bioactive molecules—curcuminoids, gingerol, and carvacrol by encapsulating in nanofiber isolated from turmeric spent (turmeric nanofiber, TNF). This formulation was completely characterized by scanning electron microscope, ultra performance liquid chromatography, and gas chromatography and evaluated for its efficacy. PFA-encapsulated TNF (PFA@TNF) considerably increased mean body weight, decreased cholesterol level, mortality rate, and reduced Escherichia coli content of broilers than antibiotic growth promoter (AGP). The depth of crypts in the ileum of broilers was considerably reduced by the inclusion of PFA@TNF in diets compared with the AGP. 相似文献
4.
5.
Gopalakrishnanchettiar Sivakamiammal Sailaja Parameswar Ramesh Harikrishna Varma 《应用聚合物科学杂志》2011,121(6):3509-3515
The physicomechanical properties of functionally active poly(hydroxyethyl methacrylate‐co‐methyl methacrylate) [poly(HEMA‐co‐MMA)] are evaluated. It has been reported that the surface phosphorylated poly(HEMA‐co‐MMA) is capable of eliciting direct bone bonding when implanted in vivo. Hence, it is important to examine the physicomechanical property of the copolymer as a function of surface modification. The properties assessed are differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), equilibrium swelling, compressive strength, and dynamic mechanical analysis. According to the DSC data, the glass transition temperature, Tg of poly(HEMA‐co‐MMA) is not significantly altered by surface phosphorylation. The TGA results demonstrated that unmodified and surface phosphorylated copolymers have similar degradation profile. The differential thermal analysis further supports the data. The equilibrium swelling of functionalized poly(HEMA‐co‐MMA) in phosphate buffer saline ascertained that surface phosphorylation significantly increased the hydrophilicity of the copolymer. The study further illustrated that the percentage of equilibrium swelling appreciably increases with increase in HEMA content in the copolymer and reached a plateau after 100 h. Both compressive strength and compressive modulus of poly (HEMA‐co‐MMA) decreased due to surface phosphorylation while dynamic storage modulus value was not altered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
6.
Static oxidation in air was performed on Nb–20Cr–20Si–5Al alloy at high temperatures ranging from 700 to 1400 °C. Pesting occurred at 700 °C while internal oxidation took place at 1300 and 1400 °C where Al2O3 initiated at the interface between NbCr2 and Nb9Cr3Si2 phases. Phases present were Nb5Si3, NbCr2, Nb solid solution and Nb9Cr3Si2 depending on the temperature. The aluminium content on each of the phases was analyzed. Al content in Nb9Si2Cr3 has been found to be as high as 5–6 atomic percent. SEM, EDS and XRD techniques were utilized in order to characterize the specimens. 相似文献
7.
The single phase hexagonal YMnO3 has been synthesized via sol-gel route by adopting two different sintering conditions. In one case, sintering has been done at ∼700 °C in Ar/H2 atmosphere and in other case it has been done at ∼1250 °C in air. Magnetic measurements of the samples, synthesized by sintering at relatively lower temperature in Ar/H2 atmosphere, show the enhanced ferromagnetic behaviour at 10 K. M-H curve shows that the value of saturation magnetization (Ms) at 10 K is 8.04 emu/g for Ar/H2 sintered sample while it is 2.93 emu/g for the air sintered sample. Moreover, a weak ferromagnetic signal at room temperature has been observed in YMnO3 compound. Magnetization versus magnetic field (M-H) curves of hydrogen treated samples, measured at room temperature, show small kink in the linear variation near origin, possibly due to presence of weak ferromagnetic interactions in the samples at room temperature. However, the polarization-electric field (P-E) curve shows weak ferroelectric characteristics for the Ar/H2 sintered samples. It is suggested that the enhanced ferromagnetism in Ar/H2 sintered sample originates from the presence of oxygen vacancies in the Ar/H2 sintered samples. Moreover, the magnetoelectric coupling coefficient at room temperature is improved to 106 mV/cm Oe for Ar/H2 sintered sample as compared to 96 mV/cm Oe for air sintered sample at 40 kHz ac magnetic field frequency. 相似文献
8.
Manitha B. Nair H. K. Varma Annie John 《Journal of materials science. Materials in medicine》2009,20(1):251
Current treatment strategies for the repair or replacement of bone use synthetic implants with stem cells and their progeny––a new approach to address unmet medical needs. This study has evaluated the effect of a silica-coated bioactive ceramic, namely HASi in comparison to hydroxyapatite (HA) on the adhesion, proliferation and osteogenic differentiation of goat bone marrow-derived mesenchymal stem cells in vitro in a prolonged culture of 28 days. The cellular activities were significantly enhanced on HASi signifying the role of silica to stimulate osteoblast cells. The fabrication of such a ‘cell-ceramic construct using autologous MSCs’ is aimed for the transplantation to a large bone defect site in the goat femur model which still remains a formidable challenge in Orthopedic surgery. 相似文献
9.
Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conventional response surface methodology (RSM). Dairy wastewater was used as source in batch fermentation was followed for this study. Response surface methodology (RSM), based on a three level, four variable Box–Behnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H2 yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H2 yield and SHPR conditions were: substrate concentration 15.3 g COD/L, pH 5.5, COD/N ratio 100.5 and COD/P ratio 120 with maximum overall desirability D of 0.94. The confirmation experiment under these optimal condition showed a HY and SHPR of 13.54 mmol H2/g COD and 29.91 mmol H2/g-VSS.d, respectively. This was only 0.22% and 0.20%, respectively, different from the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H2 yield and SHPR simultaneously. 相似文献
10.
The effect of Cr content on the microstructure and cyclic oxidation behavior of Nb–10W–XCr alloys with four different compositions has been investigated. Experiments were conducted in air at 900 °C and 1300 °C; the oxidation kinetics have been evaluated in terms of weight change per unit area with respect to exposure time. Alloy's microstructure consists of Nb solid solution phase regions surrounded by a network of NbCr2 Laves phase. A trend of improvement in oxidation resistance with increase of the intermetallic phase is observed at 1300 °C and oxidation kinetics follow a parabolic behavior. At 900 °C, alloys with higher Cr content exhibit higher oxidation rates than alloys with lower Cr content. The oxidation products are a mixture of CrNbO4, and Nb2O5 and the amount of each oxide present in the mixture is related to the intermetallic phase content. Results delineate the influence of microstructure and composition on the oxidation mechanisms of these alloys that represent a promising base for high-temperature intermetallic alloy development. 相似文献