全文获取类型
收费全文 | 27535篇 |
免费 | 1916篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 166篇 |
综合类 | 10篇 |
化学工业 | 5993篇 |
金属工艺 | 446篇 |
机械仪表 | 573篇 |
建筑科学 | 838篇 |
矿业工程 | 52篇 |
能源动力 | 631篇 |
轻工业 | 5668篇 |
水利工程 | 312篇 |
石油天然气 | 130篇 |
武器工业 | 1篇 |
无线电 | 1094篇 |
一般工业技术 | 4428篇 |
冶金工业 | 5384篇 |
原子能技术 | 84篇 |
自动化技术 | 3667篇 |
出版年
2024年 | 69篇 |
2023年 | 282篇 |
2022年 | 319篇 |
2021年 | 771篇 |
2020年 | 686篇 |
2019年 | 712篇 |
2018年 | 1235篇 |
2017年 | 1207篇 |
2016年 | 1264篇 |
2015年 | 976篇 |
2014年 | 1147篇 |
2013年 | 2331篇 |
2012年 | 1824篇 |
2011年 | 1659篇 |
2010年 | 1324篇 |
2009年 | 1191篇 |
2008年 | 1206篇 |
2007年 | 1101篇 |
2006年 | 728篇 |
2005年 | 612篇 |
2004年 | 574篇 |
2003年 | 547篇 |
2002年 | 474篇 |
2001年 | 361篇 |
2000年 | 295篇 |
1999年 | 332篇 |
1998年 | 1910篇 |
1997年 | 1203篇 |
1996年 | 745篇 |
1995年 | 397篇 |
1994年 | 307篇 |
1993年 | 323篇 |
1992年 | 91篇 |
1991年 | 75篇 |
1990年 | 63篇 |
1989年 | 59篇 |
1988年 | 87篇 |
1987年 | 75篇 |
1986年 | 62篇 |
1985年 | 71篇 |
1984年 | 61篇 |
1983年 | 34篇 |
1982年 | 37篇 |
1981年 | 60篇 |
1980年 | 59篇 |
1978年 | 30篇 |
1977年 | 104篇 |
1976年 | 207篇 |
1975年 | 33篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Hot embossing is an emerging technology, which enables cost‐effective and high‐productivity nanofabrication. It is important to optimize the processing parameters to achieve high replication accuracy nanostructure fabrication. In this article, to reveal the interrelationship between the hot embossing conditions and replication accuracy of two‐dimensional (2D) polyethylene terephthalate (PET) nanochannels, the numerical simulations were conducted by using the generalized Maxwell model. The constants of the generalized Maxwell model were calculated by a newly established fitting formula based on experimental compressive creep curves rather than tensile stress relaxation curves. Replication accuracy of 2D PET nanochannels was evaluated by a method based on weighted averages. Orthogonal method was employed during numerical simulations to optimize the hot embossing process. Under optimized hot embossing parameters, 2D PET nanochannels, ~80 nm wide, 250 nm deep and 4 mm long, were precision‐imprinted into a PET sheet. POLYM. ENG. SCI., 54:2398–2406, 2014. © 2013 Society of Plastics Engineers 相似文献
992.
Víctor M. Ovando‐Medina Josu Vizcaíno‐Mercado Omar Gonzlez‐Ortega Jos A. Rodríguez de la Garza Hugo Martínez‐Gutirrez 《Polymer Composites》2015,36(2):312-321
In this work, a composite from α‐cellulose coated with conducting polypyrrole by in situ polymerization using potassium persulfate as oxidant was obtained. The composite was characterized by fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry, UV/Vis spectroscopy, and scanning electron microscopy (SEM) analysis showed homogeneous coating of α‐cellulose with polypyrrole (PPy) to produce a composite with a conductivity of 3.5 × 10−5 S/m. Batch aqueous adsorption experiments of the reactive red 120 (RR120) dye onto the synthesized material were conducted. The results showed that this composite is an efficient adsorbent for RR120 dye removal. For the adsorption experiments set to an initial pH of 3.9, the adsorption capacity was 15.6 mg of dye/g of composite for an equilibrium concentration (in the liquid) of RR120 dye equal to 1,000 mg/L, whereas a value of 96.1 mg of dye/g of composite was obtained when the solution pH was set to 2.0 for the same equilibrium concentration. When performing adsorption experiments using pure α‐cellulose, dye adsorption was insignificant at any pH value. Adsorption isotherm for RR120 was described by a typical Freundlich model. The transient adsorption of RR120 on the synthesized composite was described by a general three‐resistance model that includes the transport on the film that surrounds the composite particles, diffusion inside the particles, and adsorption on the surface of the particles. A fitting of the uptake curves was performed allowing the estimation of values for the effective diffusivity, D0, and the adsorption rate coefficient, k1. For the adsorption experiments with an initial pH value set to 3.9, D0 was estimated as 1.05 × 10−10 m2/s, whereas k1 was 1.65 × 10−4 Ln/g mgn − 1 s; the corresponding values of k1 at pH = 2 and 9.0 were 3.18 × 10−4 and 5.16 × 10−5, respectively. POLYM. COMPOS., 36:312–321, 2015. © 2014 Society of Plastics Engineers 相似文献
993.
Rheological properties of styrene-butadiene copolymer-reinforced asphalt were investigated. A percolation-like model was used to fit dynamical experimental data, and a comparison with the Kerner-Takayanagi model is presented. In addition, a frequency-composition-temperature correspondence principle is proposed. This correspondence principle allows the prediction of the rheological behavior of an asphalt-based composite within a wide range of compositions, provided a narrow composition range at different frequencies and temperatures is previously known. © 1996 John Wiley & Sons, Inc. 相似文献
994.
Concurrent measurements of transmitted polarized light intensity and recording of the phenomenon of crystallization through polarized optical microscopy have resolved some of the controversies on the bulk crystallization behavior of poly(aryl ether ether ketone) (PEEK). The process of bulk crystallization was studied through the separation of the nucleation and growth steps. Avrami plots have shown three characteristic ranges. It was observed that a first slope at low crystallization times is associated with massive heterogeneous nucleation and/or local-order-promoted primary nucleation of spherulitic crystals. A second gradual decrement in intensity follows, showing a logarithmic tendency. It represents a mixture of at least three parallel mechanisms. These are associated with the end of the process of crystallization of the primary spherulites and in large proportion the nucleation and growth, at lower rates, of sporadically nucleated spherulites. In addition, there is some contribution from secondary crystallization to the transmitted light emerging. The whole group of nucleated spherulites continue growing up to the point of impingement, which loosely marks the beginning of the third region. This last region with lower slope than the first one and an exponential tendency reflects secondary crystallization at long times. The general characteristics of the processes of nucleation and growth are discussed. 相似文献
995.
Lluvia Guerrero-Hernndez Hctor Ivn Melndez-Ortiz Gladis Y. Cortez-Mazatan Sandra Vaillant-Snchez Ren D. Peralta-Rodríguez 《International journal of molecular sciences》2022,23(3)
The use of surfactants in polymerization reactions is particularly important, mainly in emulsion polymerizations. Further, micelles from biocompatible surfactants find use in pharmaceutical dosage forms. This paper reviews recent developments in the synthesis of novel gemini and bicephalous surfactants, micelle formation, and their applications in polymer and nanoparticle synthesis, oil recovery, catalysis, corrosion, protein binding, and biomedical area, particularly in drug delivery. 相似文献
996.
Paulo Carmo Ana M. Ribeiro Alírio E. Rodrigues Alexandre Ferreira 《American Institute of Chemical Engineers》2020,66(5):e16899
This work aims at developing an efficient and feasible adsorption-based separation process for the separation of vinyl chloride and nitrogen, on activated carbon, by employing a multitubular packed bed geometry, with adsorbent material inside the tubes. Using this geometry, a 2-dimensional mathematical model of a temperature pressure swing adsorption process was used to developed a 6-step three multitubular adsorbers system capable of separating and purifying an industrial scale gas stream of a 40:60% (v/v) vinyl chloride/nitrogen mixture into a 95% (v/v) vinyl chloride stream and a nitrogen stream with a vinyl chloride limit concentration of 8 ppm (w/w). The process reported energy consumption of 4.88 × 106 J/kgVCM and recovery capacity of 24.35 kgVCM/(m3unit h). The multitubular geometry enabled the use of lower adsorbent loads, shorter cycle times, and lower regeneration temperatures. An equivalent 1-dimensional model has also shown to satisfactorily estimate the performance of the current equipment. 相似文献
997.
Lucía Sánchez-Rodríguez Marina Kranjac Zvonimir Marijanović Igor Jerković David Pérez-López Ángel A. Carbonell-Barrachina Francisca Hernández Esther Sendra 《Journal of the American Oil Chemists' Society》2020,97(5):449-462
Three new regulated deficit irrigation (RDI) treatments were applied to “Arbequina” olive orchards during pit hardening. Oil quality was determined by measuring analytical parameters for olive oil grading, antioxidant activity, total phenol content, fatty acid profile, volatile compounds profile, and sensory analysis. Oils from RDI were classified as “extra virgin olive oil” and their quality was improved due to their higher antioxidant potential (ABTS+ [increased ~75%] and DPPH˙ [increased ~25%] assays) and phenols (increased ~53%) than control. Concentration of total volatile compounds decreased (~27%) but RDI olive oils showed a more balanced profile (alcohols, aldehydes, and esters). Monounsaturated fatty acid content increased (~5%) and atherogenic and thrombogenic indexes decreased (~8.5%) in RDI olive oil. Regarding sensory analysis, RDI provided more balanced oils with higher fruit aroma than control. Other benefits of RDI olive oil, when compared with oil from full irrigated orchards are reduced use of water and improved functional and sensory quality. 相似文献
998.
Prabhakaran Thandapani Mangalaraja Ramalinga Viswanathan Marcus Vinícius-Araújo Andris F. Bakuzis Fanny Béron Arun Thirumurugan Juliano C. Denardin Jose A. Jiménez Ali Akbari-Fakhrabadi 《Journal of the American Ceramic Society》2020,103(9):5086-5097
The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFe2O4) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFe2O4/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFe2O4 nanoparticles were higher, the binary phase CuFe2O4/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application. 相似文献
999.
Gilbert Rodríguez Eudes Villanueva Danco Cortez Esther Sanchez Elza Aguirre Alyssa Hidalgo 《Journal of the American Oil Chemists' Society》2020,97(7):729-735
Chia and sesame oils are important sources of essential fatty acids; however, their ω-3:ω-6 proportions do not comply with nutritional recommendation. A feasible approach to improve the ratio is to blend different oils, but only after understanding physical and chemical changes of the new matrix. Objective of the investigation was to determine the physico-chemical characteristics and the oxidative stability index (OSI), using the Rancimat method, of chia-sesame oil blends. The four ω-3:ω-6 blends tested (1:4, 1:6, 1:8, and 1:10) were exposed to temperatures of 110, 120, and 130 °C. The OSI values of the mixtures varied between 6.24–8.08, 3.07–4.00, and 1.62–2.01 hours for each temperature, respectively. In addition, their mean activation energy, enthalpy, entropy, and Q10 were 88.4 kJ/mol, 85.2 kJ/mol, −41.1 J/mol K, and 2.0. Finally, a shelf life prediction performed at 25 °C indicated stability times between 80 and 123 days. Therefore, combining chia and sesame oils produced blends with a good balance of essential fatty acids. 相似文献
1000.
Miguel Olvera-Sosa Antonio Guerra-Contreras Cesar F. A. Gómez-Durán Raúl González-García Gabriela Palestino 《应用聚合物科学杂志》2020,137(8):48403
The swelling behavior of poly(acrylic acid-co-itaconic acid)/NaOH hydrogel as well as its ability for iron and copper rust removal was studied and established for the first time. Through an experimental design, the influence of the synthesis parameters on hydrogel response was determined. It was found that pH-responsiveness dependence of hydrogel determines its application. In alkaline media, the hydrogel acted as superabsorbent, while in acidic, the most outstanding property was its pickling capability that allowed to clean carbon steel and copper metallic surfaces. Infrared, thermogravimetry, and scanning electron microscopy were performed to determine copolymer formation, thermal properties, and morphology. Metallic crystallographic phases formed during the corrosion processes were determined by X-ray diffractometer. Hydrogel adhesiveness followed by diffusion and dissolution of metal oxides species was identified as the main steps in the rust removal mechanism. This method offers a new, environmentally friendly perspective to eliminate corrosion from metallic surfaces compared with traditional strategies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48403. 相似文献