全文获取类型
收费全文 | 838篇 |
免费 | 48篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 4篇 |
综合类 | 2篇 |
化学工业 | 245篇 |
金属工艺 | 23篇 |
机械仪表 | 21篇 |
建筑科学 | 17篇 |
能源动力 | 50篇 |
轻工业 | 40篇 |
水利工程 | 14篇 |
石油天然气 | 4篇 |
无线电 | 81篇 |
一般工业技术 | 238篇 |
冶金工业 | 12篇 |
自动化技术 | 143篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 30篇 |
2021年 | 51篇 |
2020年 | 38篇 |
2019年 | 39篇 |
2018年 | 47篇 |
2017年 | 46篇 |
2016年 | 28篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 68篇 |
2012年 | 46篇 |
2011年 | 49篇 |
2010年 | 42篇 |
2009年 | 35篇 |
2008年 | 42篇 |
2007年 | 28篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 6篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有894条查询结果,搜索用时 31 毫秒
141.
142.
Saroj Kumari Aadesh P. Singh Sonal Dinesh Deva Rohit Shrivastav Sahab Dass Vibha R. Satsangi 《International Journal of Hydrogen Energy》2010
Nanoporous hematite (α-Fe2O3) thin films doped with Ti4+ deposited by spray-pyrolysis were successfully used in photoelectrochemical splitting of water for solar hydrogen production. X-ray diffraction, field emission scanning electron microscopy, UV–visible absorption and photoelectrochemical studies have been performed on the undoped and Ti4+ doped hematite thin films. Morphology of α-Fe2O3 thin films was observed to be nanoporous, with increased porosity (pore size ∼12 to 20 nm) on increasing doping concentration. A significant decrease in the bandgap energy from 1.95 to 1.27 eV was found due to doping. α-Fe2O3 film doped with 0.02 M Ti4+ ions exhibited best solar to hydrogen conversion efficiency (photoconversion efficiency) of 1.38% at 0.5 V/SCE. Highest photocurrent densities of 0.34 mA/cm2 at zero bias and 1.98 mA/cm2 at 0.5 V/SCE were obtained by incorporating 0.02 M Ti4+ in α-Fe2O3, which are significantly larger than earlier reported values. Donor density (30.8 × 1020 cm−3) and flatband potential (−1.01 V/SCE) obtained were also maximum for this sample. Hydrogen collected in 1 hr at Pt electrode with the best photoelectrode was 2.44 mL with 150 mW/cm2 visible light source. 相似文献
143.
144.
Vasanth Chakravarthy Shunmugasamy Dinesh Pinisetty Nikhil Gupta 《Journal of Materials Science》2013,48(4):1685-1701
Viscoelastic properties of hollow particle-reinforced composites called syntactic foams are studied using a dynamic mechanical analyzer. Glass hollow particles of three different wall thicknesses are incorporated in the volume fraction range of 0.3–0.6 in vinyl ester resin matrix to fabricate twelve compositions of syntactic foams. Storage modulus, loss modulus, and glass transition temperature are measured and related to the microstructural parameters of syntactic foams. In the first step, a temperature sweep from ?75 to 195 °C is applied at a fixed loading frequency of 1 Hz to obtain temperature dependent properties of syntactic foams. In the next step, selected four compositions of syntactic foams are studied for combined effect of temperature and loading frequency. A frequency sweep is applied in the range 1–100 Hz and the temperature is varied in the range 30–140 °C. Time–temperature superposition (TTS) principle is used to generate master curves for storage modulus over a wide frequency range. The room temperature loss modulus and maximum damping parameter, Tanδ, are found to have a linear relationship with the syntactic foam density. Increasing volume fraction of particles helps in improving the retention of storage modulus at high temperature in syntactic foams. Cole–Cole plot and William–Landel–Ferry equation are used to interpret the trends obtained from TTS. The correlations developed between the viscoelastic properties and material parameters help in tailoring the properties of syntactic foams as per requirements of an application. 相似文献
145.
Neeru Sehdev Rohit Medwal Dinesh Chandra Agrawal S. Annapoorni 《Journal of Materials Science》2013,48(8):3192-3197
Sandwiched structures comprising Pt/Co/Pt layers with varying cobalt deposition time was studied and its importance on the alloy composition, by correlating the effective interlayer diffusion with the atomic stoichiometry, has been presented. A structural phase transition from ordered L12 CoPt3 –? L10 CoPt –? L12 Co3Pt was observed with increasing Co deposition time after annealing at 700 °C. The cross-sectional SEM image of the as-deposited film clearly shows a cobalt layer sandwiched between platinum layers. Rutherford back scattering (RBS) analysis shows a multipeak signature for the as-deposited films. A detailed RBS investigation on the extent of interatomic diffusion reveals an equiatomic composition for 20 and 30 min deposition time after annealing. The equiatomic CoPt phase shows a magnetically hard behaviour with a maximum coercivity of 15000 Oe. The reported dependence of (BH)max on coercivity concludes that by tailoring an additional parameter of deposition time, diverse combinations of structural and magnetic properties can be achieved for appropriate practical applications. 相似文献
146.
The species concentrations of non-premixed hydrogen and syngas flames were examined using results obtained from direct numerical simulation technique with flamelet generated manifold chemistry. Flames with pure H2 and H2/CO mixtures are discussed for an impinging jet flame configuration. Single-point data analyses are presented illustrating the effects of fuel composition on species concentrations. In general, scatterplots of all species show the effects of fuel variability on the flame compositional structures. The behaviours of major combustion products and key radicals species indicate the effects of CO concentration on the 2/CO syngas combustion. In particular, high concentration of CO tends to induce local extinction in the 2/CO flames in which critical chemical reactions of the fuel mixture such as CO + OH become important. The unsteady fluctuations of species profiles in the wall jet region characterise the complexity of the distributions of compositional structures in the near-wall region with respect to the effects of CO concentration on the combustion of hydrogen-enriched fuels. 相似文献
147.
148.
K. Dinesh Kumar Sanjiv Gupta B.B. Sharma Andy H. Tsou Anil K. Bhowmick 《Polymer Engineering and Science》2008,48(12):2400-2409
The viscoelastic behavior of brominated isobutylene‐co‐p‐methylstyrene (BIMS) rubber/hydrocarbon resin blends and BIMS/phenol formaldehyde resin blends was studied with the use of a rubber process analyzer. Dynamic mechanical analysis and scanning electron microscopy were used to evaluate the compatibility between the BIMS/tackifier blends. Strain sweep tests at temperature below the softening point of the tackifiers showed the formation of resin–resin networks in the incompatible BIMS/phenolic resin blends. However, resin–resin network was not prominent in the case of the compatible BIMS/hydrocarbon resin blends. Frequency sweep tests were performed at the strain amplitude within the linear region at several temperatures and the variations of shear storage modulus, G′ and complex viscosity, η* against frequency were recorded. The tackifying resins modified the viscoelastic properties of the BIMS rubber by reducing the storage modulus at lower frequency and by increasing the storage modulus at higher frequencies. However, this action was found to be highly dependent on (a) rubber‐tackifier compatibility, (b) blend proportions, and (c) test temperature. Furthermore, stress relaxation measurements of the BIMS/tackifier blends at temperature below the softening point of the tackifiers showed longer period of relaxation for the incompatible BIMS/phenolic resin blends. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
149.
Yashbir Singh Shivay Dinesh Kumar Rajendra Prasad 《Nutrient Cycling in Agroecosystems》2008,81(3):229-243
Zinc deficiency is prevalent worldwide and is a barrier in achieving yield targets in crops. It is also now recognized as
a leading risk factor for disease in humans in developing countries. Generally, soil application of 5–17 kg Zn ha−1 y−1 (25–85 kg zinc sulphate heptahydrate ha−1 y−1) or more is recommended for rice. However, in the developing rice-growing countries of Asia, zinc sulphate of desired quality
is not readily available and is also quite expensive, and the farmers generally fail to apply Zn, resulting in crop yield
loss in rice. Availability of zinc-enriched urea (ZEU) makes possible not only the availability of quality zinc, but also
assures its application. Therefore, field experiments were conducted for two consecutive years at the research farm of Indian
Agricultural Research Institute, New Delhi, India, during rainy (rice) and winter (wheat) seasons of 2004–2006 on a sandy
clay-loam soil to study the effect of various concentrations of zinc enrichment of urea on productivity, zinc concentrations,
its uptake and use indices of aromatic rice–wheat cropping system. Eight treatments comprising prilled urea (PU) and 0.5,
1.0, 1.5, 2.0, 2.5, 3.0 and 3.5% zinc-enriched urea, replicated three times, were compared in a randomized block design. The
enrichment of PU was done through zinc oxide containing 80% zinc. The results of this study revealed that the zinc-enriched
urea (ZEU) had a significant effect on growth, yield attributes and yields of aromatic rice. Highest values for all these
attributes and yields were recorded at the highest enrichment (3.5%) of the PU with zinc. The highest zinc concentration and
uptake in rice grain and straw were also significantly higher with the highest level (3.5%) of zinc enrichment. The highest
total zinc uptake recorded was 1,168 and 1,353 g ha−1, during 2004 and 2005, respectively, with 3.5% ZEU. However, a major increase in grain yield of rice was recorded up to 1.0%
zinc enrichment. The residual effect of zinc-enriched urea on succeeding wheat yield and zinc uptake was significant only
at a higher level of zinc-enriched urea and only in the second year of study. Overall, 1.0% zinc-enriched urea recorded significantly
higher productivity and zinc uptake over PU in the rice–wheat cropping system and is recommended for Delhi and adjoining areas.
The recommendation is also made keeping in view the fact that with increased levels of zinc enrichment of urea, the partial
factor productivity, agronomic efficiency, apparent recovery and physiological efficiency of applied zinc in a rice–wheat
system decreased significantly. Considering all the economic parameters (benefit, benefit:cost ratio, IR gained IR−1 invested in zinc), 1.0% ZEU proved the most economic source for aromatic rice–wheat cropping system and therefore is recommended
for rice–wheat cropping system in Delhi and adjoining areas of north India. 相似文献
150.
Darin A. Ray Sarbjit Kaur Raymond A. Cutler Dinesh K. Shetty 《Journal of the American Ceramic Society》2008,91(4):1135-1140
The combined-stage sintering model was used to determine the activation energy, Q , of sintering for selected SiC-based materials. SiC densified with a liquid (1.65 wt% Al) had an activation energy of 842±79 kJ/mol, a value between those for a silicon carbide densified with 1 wt% C and 0.25 wt% B4 C ( Q =643±37 kJ/mol) and one densified with 2.5 wt% AlN ( Q =1022±122 kJ/mol), compositions which have no liquid phase below 1850°C. The SiC with Al additive began densification by 1500°C and the densification curve was offset by approximately 100°C compared with the other two materials below 1850°C. The choice and amount of additives not only affect densification and activation energy, but also influence microstructure and fracture mode, allowing engineering of mechanical properties. 相似文献