全文获取类型
收费全文 | 4865篇 |
免费 | 232篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 77篇 |
综合类 | 40篇 |
化学工业 | 1059篇 |
金属工艺 | 107篇 |
机械仪表 | 133篇 |
建筑科学 | 76篇 |
矿业工程 | 3篇 |
能源动力 | 264篇 |
轻工业 | 480篇 |
水利工程 | 42篇 |
石油天然气 | 34篇 |
无线电 | 523篇 |
一般工业技术 | 1008篇 |
冶金工业 | 589篇 |
原子能技术 | 59篇 |
自动化技术 | 636篇 |
出版年
2023年 | 83篇 |
2022年 | 170篇 |
2021年 | 263篇 |
2020年 | 172篇 |
2019年 | 179篇 |
2018年 | 229篇 |
2017年 | 195篇 |
2016年 | 196篇 |
2015年 | 124篇 |
2014年 | 198篇 |
2013年 | 321篇 |
2012年 | 221篇 |
2011年 | 257篇 |
2010年 | 182篇 |
2009年 | 157篇 |
2008年 | 154篇 |
2007年 | 146篇 |
2006年 | 125篇 |
2005年 | 104篇 |
2004年 | 89篇 |
2003年 | 72篇 |
2002年 | 71篇 |
2001年 | 45篇 |
2000年 | 50篇 |
1999年 | 54篇 |
1998年 | 199篇 |
1997年 | 134篇 |
1996年 | 110篇 |
1995年 | 72篇 |
1994年 | 79篇 |
1993年 | 71篇 |
1992年 | 51篇 |
1991年 | 46篇 |
1990年 | 27篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 24篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 34篇 |
1983年 | 16篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 33篇 |
1975年 | 17篇 |
1974年 | 24篇 |
1972年 | 14篇 |
排序方式: 共有5130条查询结果,搜索用时 15 毫秒
121.
Muhammad Idrees Saima Batool Qaiser Hussain Hidayat Ullah Mohammad Ibrahim Al-Wabel Mahtab Ahmad 《分离科学与技术》2016,51(14):2307-2317
Farmyard manure (FYM-BC) and poultry manure (PM-BC) derived biochars were applied as adsorbents to remove Cd2+ from water. Results indicated that PM-BC was a more efficient adsorbent than FYM-BC at all experimental conditions. Maximum Cd2+ adsorption was observed at pH 4, temperature 318 K and contact time 1 h, regardless of biochar type. The Langmuir model predicted maximum adsorption capacity of 90.09 mg g?1 for PM-BC. The data fitting to pseudo-second-order model proposed chemisorption of Cd2+ onto biochars. Thermodynamics indicated that adsorption was spontaneous and endothermic. Post-adsorption analysis provided evidences of strong chemical interactions between biochars’ functional groups and Cd2+ ions. 相似文献
122.
Aspects of varying crosslinker and catalyst concentrations on tear strength of silicone polymer networks: Comparison of tear strengths using samples of different geometries 下载免费PDF全文
Gul Bali Shah 《应用聚合物科学杂志》2016,133(15)
Crosslinker and catalyst concentrations have been varied to prepare different hydroxyfunctional poly(dimethylsiloxane) (HOPDMS) polymer network compositions. The tear strengths of these silicone polymer networks have been measured using different geometries, as trouser, crescent, and Graves (angled) specimens. It has been observed that the results of tear strength of Graves and crescent‐shaped specimens do not show a constant ratio with the concentration of crosslinker used for curing of HOPDMS networks. Instead, it has been observed and reported for the first time that the tear strengths of Graves and crescent‐shaped samples show a crossover at about 1.2% crosslinker. The observation of this crossover pattern for different compositions of silicone networks show that it is difficult to compare the results of the tear test of the same polymer performed on samples of different geometries with one another. The crossover pattern of the tear energy results for the test specimens of two different geometries has been explained in the light of essential work facture theory based on the geometry of the testing sample, crosslinking, and testing that alters the distribution of force over the width of the specimen. It was shown that the change in composition of the HOPDMS networks changes the order of ranking of Graves and crescent tear tests. With varying catalyst concentration in the silicone network composition, the tear property differences between the Graves and crescent‐shaped specimens are not significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43115. 相似文献
123.
124.
125.
Ultra-high strength Mg-9Gd-4Y-0.5Zr alloy with bi-modal structure processed by traditional extrusion
M. Hong S. S. A. Shah D. Wu R.S. Chen X. H. Du N. T. Hu Y. F. Zhang 《Metals and Materials International》2016,22(6):1091-1097
It is usual to observe that multi-scale structures can lead to combined strength and ductility both in aluminum alloys and steels, but related research has been seldom reported yet in magnesium alloys. In this study, applying traditional one step extrusion, we have successfully obtained a bimodal (Mg-9Gd-4Y-0.5Zr) alloy capable of ultra-high strength. The characterized sample reveal a bi-modal microstructure with two constitutions, i.e. stretched coarse-grain region with strong basal fiber texture and recrystallization fine-grain region. The bi-modal structured sample exhibit excellent mechanical properties with an ultimate strength 508 MPa and elongation 8% via 400 °C extrusion and subsequently 200 °C-60 h peak aging process. Ultra-high strength can be attributed to its strong extrusion texture in stretched coarse grains and dispersed nano-scale precipitates. This unique bimodal structure could be produced easily by one step extrusion, which is quite reliable and low costs in industrial applications of magnesium alloys with ultra-high strength as well as ideal ductility. 相似文献
126.
Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail 下载免费PDF全文
S. M. Shakil Hussain Mustapha Alao Animashaun Muhammad Shahzad Kamal Nisar Ullah Ibnelwaleed A. Hussein Abdullah S. Sultan 《Journal of surfactants and detergents》2016,19(2):413-420
Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10?4 and 1.04 × 10?4 mol/L, and the corresponding surface tension (γCMC) values were 33.14 and 34.89 mN m?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation. 相似文献
127.
Farman Muhammad Nawaz Fahim Majeed Sadia Javeed Hafiz Muhammad Rashad Ahsan Muhammad Ahmad Khawaja Shafique Aurangzaib Muhammad Bukhari Muhammad Adnan Shehzad Muhammad Asif Hussain Muhammad Baqir 《SILICON》2022,14(13):7901-7917
Silicon - The present study evaluated the effect of silicon (Si) seed priming and sulfur (S) foliar spray on drought tolerance of two contrasting maize hybrids viz. drought tolerant Hi-Corn 11 and... 相似文献
128.
Shah Naishalkumar Rahul M. R. Phanikumar Gandham 《Metallurgical and Materials Transactions A》2021,52(5):1574-1580
Eutectic high entropy alloy with seven components is designed based on the integrated computational materials engineering (ICME) framework. The framework includes thermodynamic prediction using calculation of phase diagrams (CALPHAD), microstructure simulation using phase-field method, and experimental validation. The designed alloy shows the eutectic structure consisting of FCC and laves phase in the composition range from 8.25 to 10 at. pct Ta. The simulation and experimental results are co-related and a framework is proposed that can be used for high entropy alloy design subjected to various manufacturing processes.
相似文献129.
Mamta Latwal Prakash Chandra Shah Raj Ali 《Journal of Applied Electrochemistry》2014,44(10):1127-1134
Nanostructured copper hexacyanidoferrate has been synthesized and characterized using elemental analysis, atomic absorption spectroscopy, thermal and infrared spectral studies. The transmission electron microscopic studies of the synthesized material showed that it consisted of irregular oval and rod shaped particles with a size range 70–100 nm. Nanostructured copper hexacyanidoferrate modified glassy carbon electrode was characterized by cyclic voltammetery and nanostructured copper hexacyanidoferrate–carbon nanotube composite material modified glassy carbon electrode has been used for electrocatalytic oxidation of salbutamol. The electrode modified with composite material was found to reduce the peak potential of oxidation of salbutamol by nearly 90 mV. 相似文献
130.
Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior 下载免费PDF全文
In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO3 was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO3 mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO3 maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237. 相似文献