全文获取类型
收费全文 | 3347篇 |
免费 | 247篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 21篇 |
综合类 | 4篇 |
化学工业 | 822篇 |
金属工艺 | 135篇 |
机械仪表 | 227篇 |
建筑科学 | 53篇 |
能源动力 | 123篇 |
轻工业 | 377篇 |
水利工程 | 27篇 |
石油天然气 | 2篇 |
无线电 | 564篇 |
一般工业技术 | 674篇 |
冶金工业 | 176篇 |
原子能技术 | 38篇 |
自动化技术 | 364篇 |
出版年
2024年 | 3篇 |
2023年 | 57篇 |
2022年 | 72篇 |
2021年 | 118篇 |
2020年 | 95篇 |
2019年 | 107篇 |
2018年 | 110篇 |
2017年 | 131篇 |
2016年 | 175篇 |
2015年 | 116篇 |
2014年 | 193篇 |
2013年 | 244篇 |
2012年 | 251篇 |
2011年 | 301篇 |
2010年 | 223篇 |
2009年 | 179篇 |
2008年 | 192篇 |
2007年 | 154篇 |
2006年 | 125篇 |
2005年 | 106篇 |
2004年 | 74篇 |
2003年 | 74篇 |
2002年 | 79篇 |
2001年 | 76篇 |
2000年 | 47篇 |
1999年 | 50篇 |
1998年 | 83篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有3607条查询结果,搜索用时 0 毫秒
91.
Jong-Ho Ryu Jong Hyun Seo Jae-Han Jeong Sung-Kap Kim Dong Nyung Lee 《Journal of Applied Electrochemistry》2004,34(9):879-884
A study has been made of the electrochemical etching of 99.99% aluminum foils at a current density of 50 mA cm–2in AlCl3–HCl solutions (1 m Cl–) at 80 °C. The solutions were made by dissolving metallic aluminum into 1m HCl solution, to give a Cl– concentration of 1 m. The number density of etch tunnels and the homogeneity of tunnel length decreased, and the mean pit size and its standard deviation increased with increasing Al3+ concentration. The results were discussed based on potential transients at a current density of 50 mA cm–2, current–potential curves at a scan rate of 10 m Vs–1 and electrochemical impedance spectra. 相似文献
92.
Chu Van Chiem Hyung-Kee Seo Shafeeque G. Ansari Gil-Sung Kim Jae Myung Seo Hyung-Shik Shin 《Korean Journal of Chemical Engineering》2003,20(6):1154-1157
In this paper, the growth of Lonsdaleite diamond using hot-filament chemical vapor deposition (HFCVD) on flashed and reconstructed
Si (100) is reported. Surface morphology studies using scanning electron microscopy (SEM) show that the film is composed of
decahedron and icosahedron diamond particles. The X-ray diffraction (XRD) pattern has a strongest peak at 47° and a peak at
41°, which is indicative of Lonsdaleite nature of the grown diamond film. The Raman spectrum of the film shows a broadened
diamond peak at wave number of 1,329 cm−1, which has shifted towards the peak position corresponding to Lonsdaleite nature of the diamond (1,326 cm−1). 相似文献
93.
Different fluorination methods were applied to modify the surface properties of carbon fibers. The relationship between the degree of fluorination and the physicochemical properties of carbon fibers was studied using a combination of mechanical tests, elemental analysis (EA), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD). EA and XPS analyses of fluorinated carbon fibers showed that treatment with mixtures of F2/O2 introduced a much higher fluorine concentration than that with F2 only. However, XRD analysis showed that there was no increase in the interlayer distance, due to the mild fluorination condition applied. Consequently, the oxyfluorination was one of the more effective methods to increase surface polarity of carbon fibers, which probably played an important role in improving the tensile properties of the fibers in the epoxy resin system. 相似文献
94.
We prepared poly(p‐phenylene pyromellitimide) (PMDA–PDA), poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10?10 to 11.3 × 10?10 cm2/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in‐plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003 相似文献
95.
Seungnyeong Heo Jonghwi Baek Juhyun Bae Prof. Dr. Bo Am Seo Seongjun Kim Subin Jeong Suhyun Kim Dr. Yiseul Ryu Prof. Dr. Joong-jae Lee 《Chembiochem : a European journal of chemical biology》2023,24(11):e202200700
Horseradish peroxidase (HRP) is a pivotal biocatalyst for biosensor development and fine chemical synthesis. HRP proteins are mostly extracted and purified from the roots of horseradish because the solubility and productivity of recombinant HRP in bacteria are significantly low. In this study, we investigate the reconstitution system of split HRP fragments to improve its soluble expression levels in E. coli allowing the cost-effective production of bioactive HRPs. To promote the effective association between two HRP fragments (HRPn and HRPc), we exploit SpyTag-SpyCatcher chemistry, a versatile protein coupling method with high affinity and selectivity. Each HRP fragment was genetically fused with SpyTag and SpyCatcher, respectively, exhibiting soluble expression in the E. coli cytoplasm. The engineered split HRPs were effectively and irreversibly reconstituted into a biologically active and stable assembly that can catalyze intrinsic enzymatic reactions. Compared to the chaperone co-expression system, our approach shows that the production yield of soluble HRP is comparable, but the purity of the final product is relatively high. Therefore, our results can be applied to the high-yield production of recombinant HRP variants and other difficult-to-express proteins in bacteria without complex downstream processes. 相似文献
96.
A new blue-emitting nanophosphor of Eu2+-activated BaCa2Al8O15 was synthesized by the Pechini method. The phosphors were investigated by X-ray powder diffraction (XRD) measurement and confirmed to be a pure crystalline phase of BaCa2Al8O15. The photoluminescence excitation and emission spectra, the luminescence decay and the color coordinates were taken to investigate the luminescence characteristics. The dependence of luminescence intensities BaCa2Al8O15:Eu2+ on the doping concentrations was investigated. This nanophosphor can be efficiently excited by UV light and presents bright blue luminescence. Under the same conditions, the light yield of BaCa2Al8O15:Eu2+ is about 1.2 times higher than that of blue-emitting phosphor BaMgAl10O17:Eu2+. Eu2+-activated BaCa2Al8O15 nanophosphor exhibits the long-lasting phosphorescence, which was analyzed by measuring the afterglow decay curves. The co-doped Eu3+ ions and some defects were suggested to be the possible trap-centers. 相似文献
97.
Young‐Min Cho Hyung‐Jae Lee Yun Heo Shin‐Hye Park Si‐Yoong Seo Jae‐Hong Han Tae‐Il Son 《应用聚合物科学杂志》2013,129(4):2161-2170
Carboxymethyl starch was modified by the incorporation of an azidophenyl group to prepare photoreactive starch, and characterized by Fourier transform infrared reflectance (FT‐IR), proton nuclear magnetic resonance (1H‐NMR), and ultraviolet (UV) spectroscopy. Photo‐irradiation immobilized the Az‐starch on a polystyrene plate and it was stably retained on the surface. The protein containing immobilized Az‐starch was also immobilized on a stripe micropatterned plate. UV irradiation time and Az‐starch concentration were used to alter the physical properties of Az‐starch and consequently control the rate of epidermal growth factor (EGF) release. The Az‐starch that released growth factor was not cytotoxic to 3T3‐L1 fibroblast cells, and the immobilized EGF maintained its activity and induced cellular proliferation in vitro. These results suggest that Az‐starch could be useful as a clinical synthetic material for medical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
98.
Random or tapered solution styrene–butadiene copolymer (SSBR) is very difficult to prepare in an isothermal batch process without the use of polar modifiers because of the diverse reactivity ratios of the styrene and the butadiene in hydrocarbon solvents. In the presence of polar modifiers, the random SSBR can be synthesized by anionic living polymerization with the variety of microstructures, which results in the change of glass transition temperature (Tg). This article will discuss the use of sodium dodecylbenzene sulfonate as a polar modifier in isothermal batch process that controls the microstructure of the SSBR resulting in a random as well as tapered SSBR with low Tg (?67°C to ?80°C). The Tg of SSBR was controlled by the styrene content rather than the microstructure of polybutadiene. Physical properties of SSBR compounding were discussed for tire tread applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
99.
Sung-Chul Seo Sergey A. Grinshpun Yulia Iossifova Detlef Schmechel Carol Y. Rao Tiina Reponen 《Aerosol science and technology》2013,47(8):794-803
A field-compatible collection system was developed and tested for the collection and analysis of fungal fragments. The new collection system consists of two types of Sharp-Cut cyclone samplers (PM 2.5 and PM 1.0 ) and an after-filter. Fungal particles are collected into three size fractions: (1) spores ( > 2.5 μ m); (2) a fragment-spore mixture (1.0–2.5 μ m); and (3) submicrometer-sized fragments ( < 1.0 μ m). The system was laboratory-tested using polystyrene latex (PSL) particles and particulate matter aerosolized from sporulating Aspergillus versicolor and Stachybotrys chartarum cultures. In addition to the particle count measured with direct-reading instruments, the (1 → 3)- β -D-glucan content in each size fraction was determined with the Limulus Amebocyte Lysate (LAL) assay. Experiments conducted with PSL particles showed that the 50% cut-off values of the two cyclone samplers under the test conditions were 2.25 μ m and 1.05 μ m, respectively. No particle bounce onto the after-filter was observed when the total particle number entering the collection system was kept below 1.6 × 10 8 . The (1 → 3)- β -D-glucan assay of samples aerosolized from both fungal species suggested that surface area is an important factor for determining the (1 → 3)- β -D-glucan content in the entire size-range of particles. In conclusion, the new methodology is a promising tool for separating and analyzing fungal fragment samples. 相似文献
100.
Se Woong Lee Seong Wook Lim Soon Hee Park Kwang Ha Keun Sik Kim Se Min Oh Jin Yong Lee Gon Seo 《Korean Journal of Chemical Engineering》2013,30(12):2241-2247
The reaction of m-xylylenediamine (mXD) with carbon dioxide was examined and its feasibility as a sequestration material of carbon dioxide was discussed. The reaction was monitored by using the FT-IR and gravitational methods, while the crystalline structure of the reaction product was investigated with elemental analysis, powder Xray diffraction, single crystallography, and 13C MAS NMR spectroscopy. Even at ambient temperature, mXD reacted with carbon dioxide of low partial pressure in the atmosphere and produced a 1: 1 molar adduct which appeared as a white crystalline material. The hydrogen bonds that formed between the adduct molecules resulted in the formation of a stable crystal. The sequestration capacity of mXD was very great, ~280 mg g mXD ?1 below 50 °C. An adsorbent prepared by dispersing mXD on silica was capable of capturing carbon dioxide, but it could be regenerated by evacuating at 25 °C. 相似文献