全文获取类型
收费全文 | 6385篇 |
免费 | 569篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 77篇 |
综合类 | 11篇 |
化学工业 | 1877篇 |
金属工艺 | 231篇 |
机械仪表 | 336篇 |
建筑科学 | 102篇 |
矿业工程 | 2篇 |
能源动力 | 351篇 |
轻工业 | 455篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 1117篇 |
一般工业技术 | 1447篇 |
冶金工业 | 253篇 |
原子能技术 | 41篇 |
自动化技术 | 656篇 |
出版年
2024年 | 4篇 |
2023年 | 68篇 |
2022年 | 102篇 |
2021年 | 175篇 |
2020年 | 135篇 |
2019年 | 184篇 |
2018年 | 226篇 |
2017年 | 215篇 |
2016年 | 251篇 |
2015年 | 228篇 |
2014年 | 317篇 |
2013年 | 409篇 |
2012年 | 478篇 |
2011年 | 521篇 |
2010年 | 428篇 |
2009年 | 422篇 |
2008年 | 367篇 |
2007年 | 284篇 |
2006年 | 263篇 |
2005年 | 216篇 |
2004年 | 202篇 |
2003年 | 228篇 |
2002年 | 183篇 |
2001年 | 127篇 |
2000年 | 135篇 |
1999年 | 130篇 |
1998年 | 142篇 |
1997年 | 84篇 |
1996年 | 74篇 |
1995年 | 53篇 |
1994年 | 45篇 |
1993年 | 30篇 |
1992年 | 43篇 |
1991年 | 24篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 12篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有6971条查询结果,搜索用时 15 毫秒
191.
Microwave Sol–Gel Synthesis of CaGd2(MoO4)4:Er3+/Yb3+ Phosphors and Their Upconversion Photoluminescence Properties 下载免费PDF全文
Chang Sung Lim Victor Atuchin Aleksandr Aleksandrovsky Maxim Molokeev Aleksandr Oreshonkov 《Journal of the American Ceramic Society》2015,98(10):3223-3230
CaGd2(MoO4)4:Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) have been successfully synthesized by the microwave sol–gel method, and the crystal structure refinement and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after heat‐treatment at 900°C for 16 h, showed a well‐crystallized morphology. Under the excitation at 980 nm, CaGd2(MoO4)4:Er3+/Yb3+ particles exhibited strong 525 and 550‐nm emission bands in the green region and a weak 655‐nm emission band in the red region. The Raman spectrum of undoped CaGd2(MoO4)4 revealed about 15 narrow lines. The strongest band observed at 903 cm?1 was assigned to the ν1 symmetric stretching vibration of MoO4 tetrahedrons. The spectra of the samples doped with Er and Yb obtained under 514.5 nm excitation were dominated by Er3+ luminescence preventing the recording Raman spectra of these samples. Concentration quenching of the erbium luminescence at 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions in the CaGd2(MoO4)4:Er3+/Yb3+ crystal structure was established to be approximately at the 10 at.% doping level. 相似文献
192.
Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure‐driven processes 下载免费PDF全文
Polyamide thin film composite hollow fiber membranes have advantages in their unique structure compared to flat sheet membranes. This study examined interfacial polymerization methods for fabricating pilot scale hollow fiber membranes (membrane area: 1.2 m2, number of hollow fiber strands: 1200). For use in osmotic pressure‐driven processes, a one‐pot hydrophilic interfacial polymerization procedure was developed simultaneously to modify the surface property and synthesize polyamide thin film. With the procedure, a pilot scale module has a water flux of 13 LMH using a draw solution of 0.6M NaCl and a feed solution of distilled water through the design of the module configuration. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46110. 相似文献
193.
Ik Sang Shin Sung Mo Son Dae Ho Lim Yong Kang Heon Jung Ho Tae Lee 《Korean Journal of Chemical Engineering》2010,27(3):1015-1020
Characteristics of heat transfer were investigated in pressurized slurry bubble column reactors whose diameter was either
0.051, 0.076, 0.102 or 0.152 m (ID) and 1.5 m in height, respectively. Effects of gas velocity (U
G
), solid contents (S
C
), pressure (P), liquid viscosity (μ
L
) and column diameter (D) on the heat transfer coefficient (h) between the immersed vertical heater and the column were determined.
Multiple effects such as UG and D, P and D, μ
L
and D, and S
C
and D on the value of heat transfer coefficient were discussed. Temperature fluctuations were also measured and analyzed
by adapting chaos theory, which was used to explain the effects of operating variables on the heat transfer in the column.
The heat transfer coefficient increased with increasing gas velocity, pressure or solid content in the slurry phase, but decreased
with increasing liquid viscosity or column diameter. The decrease trend of h with increasing column diameter was somewhat
sensitive when the gas velocity was relatively high (U
G
⩾12 cm/s). The effects of column diameter on the h value became almost linear when the operating pressure (P=4−10 kg
f
/cm2), liquid viscosity (μ
L
=20−38 mPa·s) or solid content in the slurry phase (S
C
=10−20 wt%) was relatively high and gas velocity was relatively low, within these experimental conditions. The heat transfer
coefficient was well correlated in terms of dimensionless groups as well as operating variables. 相似文献
194.
An innovative α‐calcium sulfate hemihydrate bioceramic as a potential bone graft substitute 下载免费PDF全文
Heng‐Jui Hsu Rahmat Abd Waris Muhammad Ruslin Yun‐Ho Lin Chin‐Sung Chen Keng‐Liang Ou 《Journal of the American Ceramic Society》2018,101(1):419-427
The microstructural, in vitro and in vivo properties of the microwave‐synthesized samples were investigated using the optical microscope, scanning electron microscope, X‐ray diffraction, differential scanning calorimeter, contact angle goniometer, cell cytotoxicity assay, and chick chorioallantoic membrane (CAM) model in the study. When the calcium sulfate dihydrate (CSD) precursor underwent microwave irradiation treatment at temperatures between 100°C and 160°C, the crystal morphologies and crystalline structures were transformed from (tablet‐like CSD (monoclinic)) → (tablet‐like CSD (monoclinic) + long column α‐calcium sulfate hemihydrate (α‐CSH, hexagonal)) → (long column CSD (monoclinic) + short column α‐CSH (hexagonal)) → (uniform short column α‐CSH (hexagonal)). The high‐purity α‐CSH with uniform short column crystals around 10 μm in length can be synthesized at 160°C for 10 minutes and exhibits a higher hydrophilic feature in blood. Moreover, the cell cytotoxicity assay indicated that the microwave‐synthesized samples possessed well biocompatibility. In vivo results also demonstrated that the microwave‐synthesized α‐CSH not only induces angiogenesis formation but also facilitates osteogenesis. Therefore, the microwave‐synthesized α‐CSH is a promising bone graft substitute that can be applied in dental and orthopedic fields. 相似文献
195.
Supported molybdenum clusters were prepared by sublimation of Mo(CO)6 onto dehy-droxylated alumina followed by decomposition in flowing dihydrogen at 970 K. These alumina-supported molybdenum clusters were found by XAFS to transform into Mo2C if heated in a 20% methane/H2 mixture at 950 K. For the hydrogenolysis ofn-butane at 510 K and CO-H2 reactions at 570 K, both at atmospheric pressure, molybdenum and carburized molybdenum showed similar, but different for each reaction, turnover rates. The product distribution was the same for each reaction on Mo and Mo2C. In both reactions, in situ XAFS data for fresh and used catalysts indicated that Mo clusters progressively transformed into Mo2C under the reaction conditions 相似文献
196.
A new strategy for the selective coating of tin sulfide (SnS) on the surface of moth‐eye patterned (MEP) conducting polymer film is studied by considering the optical properties of the antireflective moth‐eye pattern and flexibility of polymer films. The semiconductor SnS is selectively coated on the surface of MEP microdomes of poly(3,4‐ethylenedioxythiophene) poly(styrene‐sulfonate) (PEDOT:PSS) film. The SnS coated MEP film is obtained by using pore selectively SnS thin layer functionalized polystyrene honeycomb‐patterned porous (HCP) film as a template. Aqueous PEDOT:PSS solution is poured on the SnS functionalized HCP films and detached for the fabrication of SnS coated MEP films. The films show a satisfactory photo‐responsive property under solar stimulated light illumination due to the antireflective MEP structure of PEDOT film and homogenous SnS coating on the surface of the conducting polymer. 相似文献
197.
Thomas Schneider Benjamin L. Oyler Sung Hwan Yoon Tao Liang Gloria S. Yen David P. A. Kilgour Erik Nilsson David R. Goodlett 《Food Analytical Methods》2018,11(9):2447-2454
Rapid food product analysis is of great interest for quality control and assurance during the production process. Conventional quality control protocols require time and labor-intensive sample preparation for analysis by state-of-the-art analytical methods. To reduce overall cost and facilitate rapid qualitative assessments, food products need to be tested with minimal sample preparation. We present a novel and simple method for assessing food product compositions by mass spectrometry using a novel surface acoustic wave nebulization method. This method provides significant advantages over conventional methods requiring no pumps, capillaries, or additional chemicals to enhance ionization for mass spectrometric analysis. In addition, the surface acoustic wave nebulization–mass spectrometry method is ideal for rapid analysis and to investigate certain compounds by using the mass spectra as a type of species-specific fingerprint analysis. We present for the first time surface acoustic wave nebulization-generated mass spectra of a variety of fermented food products from a small selection of vinegars, wines, and beers. 相似文献
198.
To improve the electrical conductivity of polyacrylonitrile (PAN) film, metallic sulfides and PAN composite film were prepared by the chelating method. Dense PAN film and porous PAN film were prepared by dry process and wet process, respectively. These PAN films were treated to NH2OH solution to introduce the amidoxime group coordinated with metallic ion. Cu+2 and Cd+2 ions were adsorbed to amidoximated PAN films, the sulfur ion was treated with metal-adsorbed PAN films, and thus CuS—and CdS–PAN composite films were prepared. The adsorptive capacity of amidoximated PAN film for the Cu+2 ion was independent of the morphology of the PAN film, but the adsorptive capacity of the Cd+2 ion on amidoximated PAN film was dependent on porosity of the polymer. Adsorptive capacity of amidoximated porous PAN film for Cd+2 was improved about four times than that of amidoximated dense PAN film. The electrical conductivities of CuS–dense and porous PAN composite film were both 10?1 S/cm in optimum condition, but because of the difference in adsorptive capacity, the electrical conductivities of CdS–dense and CdS–porous PAN composite films were 10?9 S/cm and 10?4 S/cm, respectively. Additionally, because CdS was known as a photoconductive material, the photoconductive properties of CdS–porous PAN composite film were investigated. 相似文献
199.
Daeyeon?Kim Jin-Hong?Kim Sung?Hun?Kwon Sok?On?Lee Bongkuk?SeoEmail author Choong-Sun?LimEmail author 《Polymer Bulletin》2017,74(11):4595-4605
A thermally stable thiodiphenyl epoxy resin was modified with a dimeric fatty acid at an epoxy resin:fatty acid molar ratio of 4:1. The thermal and mechanical properties of the modified epoxy resin were studied by preparing an epoxy composition with an amine curing agent and a catalyst, followed by curing at 170 °C to produce a neat plastic epoxy resin. The tensile and impact strengths of the resin indicated improved flexibility and toughness compared to other epoxy resins. Enhanced toughness was confirmed by the increased lap shear strength in single lap joints prepared with steel substrates attached by the resin. 相似文献
200.
Platinum has been supported on NaY zeolite by ion exchange of Pt(NH3)4
2+. Clustering of Pt atoms into a 1 nm cluster, and three-dimensional quantum-size wire (3 nm thick) network (greater than 100 nm) from reduction of the Pt species has been investigated by extended X-ray absorption fine structure transmission electron microscopy and xenon adsorption measurements. 相似文献