全文获取类型
收费全文 | 5710篇 |
免费 | 273篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 80篇 |
综合类 | 8篇 |
化学工业 | 1094篇 |
金属工艺 | 116篇 |
机械仪表 | 125篇 |
建筑科学 | 177篇 |
矿业工程 | 8篇 |
能源动力 | 177篇 |
轻工业 | 323篇 |
水利工程 | 32篇 |
石油天然气 | 22篇 |
无线电 | 947篇 |
一般工业技术 | 960篇 |
冶金工业 | 1012篇 |
原子能技术 | 29篇 |
自动化技术 | 895篇 |
出版年
2024年 | 9篇 |
2023年 | 95篇 |
2022年 | 175篇 |
2021年 | 276篇 |
2020年 | 215篇 |
2019年 | 180篇 |
2018年 | 221篇 |
2017年 | 186篇 |
2016年 | 273篇 |
2015年 | 167篇 |
2014年 | 224篇 |
2013年 | 351篇 |
2012年 | 264篇 |
2011年 | 298篇 |
2010年 | 219篇 |
2009年 | 212篇 |
2008年 | 210篇 |
2007年 | 186篇 |
2006年 | 142篇 |
2005年 | 127篇 |
2004年 | 101篇 |
2003年 | 87篇 |
2002年 | 75篇 |
2001年 | 82篇 |
2000年 | 53篇 |
1999年 | 76篇 |
1998年 | 383篇 |
1997年 | 195篇 |
1996年 | 144篇 |
1995年 | 107篇 |
1994年 | 87篇 |
1993年 | 109篇 |
1992年 | 39篇 |
1991年 | 39篇 |
1990年 | 25篇 |
1989年 | 37篇 |
1988年 | 25篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 22篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 33篇 |
1976年 | 55篇 |
1975年 | 9篇 |
排序方式: 共有6005条查询结果,搜索用时 15 毫秒
201.
Quang Vinh Nguyen 《Chemical Engineering Communications》2020,207(10):1358-1367
AbstractThermotropic liquid crystalline polymers (LCPs) have been of great interest for electronic packaging. Herein, we introduce a series of wholly aromatic, thermotropic LCPs from copoly(ester amide)s of 6-hydroxy-2-naphthalic acid, isophthalic acid, terephthalic acid, and 4-aminophenol, prepared by a convenient one-pot melt polycondensation. Almost synthesized copoly(ester amide)s exhibited good solubility in common organic solvents at room temperature. Furthermore, they possessed high thermal stability with 2% degradation temperatures (Tid) of 359–368?°C and the char yields (at 600?°C) of 50.3–55.6%. The synthesized copoly(ester amide)s had relatively low coefficient of thermal expansion (CTE) values, which were 35.85–41.21?ppm °C?1 in the temperature range of 50–200?°C. Furthermore, an annealing process could be employed to improve the thermomechanical properties of synthesized polymers. For instance, the CTE of sample LCP3 in range temperature of 275–315?°C was reduced by more than 90% after annealing at 320?°C for 1?h, implying the feasibility for electronic packaging. 相似文献
202.
Nguyen T. H. Hanh Bui T. Nhung Le T. Hop Le T. Tuyet Duong T. A. Dao Nguyen T. T. Thu Tran Quang Binh 《Lipids》2020,55(6):683-691
Apolipoprotein A-V encoded by apolipoprotein 5 (APOA5) gene plays an important role in lipid metabolism, especially in the regulation of plasma triglycerol levels. The study aimed to evaluate the association of the APOA5-rs662799 polymorphism with dyslipidemia in Vietnamese children and the potential modification of obesity-related traits (body mass index, waist circumference, hip circumference, and waist-to-hip ratio) on this association. A case–control study was conducted with a total of 154 dyslipidemia cases and 389 controls at the age of 6 to 10 recruited at 31 primary schools in Hanoi city of Vietnam. Genotype for APOA5-rs662799 polymorphism was determined by the restriction fragment length polymorphism analysis. The association of APOA5-rs662799 polymorphism with dyslipidemia adjusting for age, sex, residence, and obesity-related traits was analyzed by binary logistic regression analysis. The results showed that in comparison with T/T and T/C carriers, the C/C carriers had a higher concentration of serum TAG in cases (p =0.049). Carriers of the C allele (C/C + T/C) had higher risk for developing dyslipidemia and hypertriglyceridemia than subjects with T/T genotype (odds ratio, OR = 1.7, p =0.0062 and OR = 1.6, p = 0.026, respectively). The association remained significant after adjusting for age, gender, residence, and obesity status (OR = 1.75, p = 0.006 and OR = 1.53, p = 0.049, respectively) or other obesity-related traits. The study suggested that the APOA5-rs662799 polymorphism may be a determinant of dyslipidemia and hypertriglyceridemia in Vietnamese children, independent of obesity-related traits. 相似文献
203.
Ho Kim Dan Nguyen Minh Ty Dacheng Zhou Jianbei Qiu Anh-Luan Phan 《Journal of the American Ceramic Society》2020,103(11):6356-6368
In this paper, we study the influence of Cr3+ on yellowish-green upconversion (UC) emission and the energy transfer (ET) of Er3+/Cr3+/Yb3+ tri-doped in SiO2–ZnO–Na2O–La2O3 (SZNL) zinc silicate glasses under excitation of the 980 nm laser diode (LD). The influence of Cr3+ on enhancing the red UC emission of Er3+/Cr3+/Yb3+ tri-doped in SiO2–ZnO–Na2O–La2O3 zinc silicate glasses under the excitation of 980nm LD was also investigated. The ET processes between Yb3+, Cr3+, and Er3+, together with the combination of Yb3+-Cr3+-Er3+, which led to the green UC emission intensity of Er3+/Cr3+/Yb3+ tri-doped in SiO2–ZnO–Na2O–La2O3 zinc silicate glasses bands centered at ~546 nm have been significantly enhanced. By increasing the concentration of Cr3+ from 0 up to 5 mol.%, we can locate the Commission Internationale de l'éclairage (CIE) 1931 (x; y) chromaticity coordinates for UC emissions of Er3+/Cr3+/Yb3+ tri-doped in the central position of the yellowish-green color region of CIE 1931 chromaticity diagram. Besides, the ET processes between the Yb3+, Cr3+, and Er3+ are also proposed and discussed. 相似文献
204.
Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming
Thanh Khoa Phung Thong Le Minh Pham Anh-Nga T. Nguyen Khanh B. Vu Ha Ngoc Giang Tuan-Anh Nguyen Thanh Cong Huynh Hong Duc Pham 《化学工程与技术》2020,43(4):672-688
Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process. 相似文献
205.
Nguyen Chi Trung Ngo Hironari Sugiyama Buddhika Amila Kumara Sodige Juan Paulo Wiff Satoru Yamanaka Yoonho Kim Tsuneo Suzuki Masaaki Baba Masatoshi Takeda Noboru Yamada Koichi Niihara Tadachika Nakayama 《Journal of the American Ceramic Society》2023,106(1):201-212
The energy-harvesting ability of the lead-free ferroelectric Ba(Zr,Ti)O3 was investigated and greatly enhanced using the Kim novel electrothermodynamic cycle for low-temperature application. Ba(Zr,Ti)O3 was synthesized with a Zr:Ti ratio of 10:90 (BZT10) by hot-press sintering, which exhibited a mix relaxor-ferroelectric behavior. For power generation using the Kim cycle with low and high temperatures of TL = 25°C, TH = 120°C, the most optimized temperature pattern occurred for a heating time of 12.5 s and a cooling time of 22.5 s. Under these conditions, the electric field increased during the novel isodisplacement process, and the displacement variation in the isoelectric step reached the highest value and maximized the BZT10 cycle loop area. Applying these conditions while lowering TL to 20°C, an energy density ND = 504 mJ/cm3 was achieved. This value is the highest obtained energy density in a practical test for lead-free ferroelectric bulk material in the BaTiO3 family. 相似文献
206.
Phuong Pham Thi Thuy Phuong Nguyen Nguyen Kumar P. Senthil Duy Nguyen Phuc Hoang Van Le Quyet Ngoc Le Thi Bao Jalil A. A. Rajendran Saravanan Cheng Chin Kui Nguyen Thanh-Huong Dinh Minh Tuan Nguyen Vo Dai-Viet N. 《Topics in Catalysis》2023,66(1-4):41-52
Topics in Catalysis - CO2 reforming of methanol for producing hydrogen was experimentally carried out in a fixed-bed reactor on 10%Ni/SiO2. The 10%Ni/SiO2 was completely reduced during H2... 相似文献
207.
Experimental results at 25°C are reported for infinite‐dilution distribution coefficients for 19 nonvolatile solutes between aqueous solution and three kinds of polymer films, and for their diffusion coefficients in the polymer matrix. The experiments were performed by coupling UV spectroscopy and gravimetric measurements with mass balances. The solutes are aromatic nonvolatile compounds that are of interest in environmental technology and may serve as model compounds for drug‐delivery systems. The polymers are ethylene‐vinyl acetate copolymers with 33 (EVAc33) and 45 (EVAc45) weight percentage vinyl acetate, and poly(vinyl acetate) (PVAc) widely used in drug‐delivery devices. For PVAc, a long time is required to reach equilibrium. Because the required time is too long for reasonable experimental studies, equilibrium distribution coefficients were calculated from finite‐time data by using a diffusion model. The contribution of surface adsorption is shown to be negligible. Infinite‐dilution distribution coefficients Ks, defined as the volume fraction of solute in the polymer divided by that in water, tend to increase with vinyl acetate content; they range from near unity to several hundred. Diffusion coefficients, determined from time‐dependent sorption data, are significantly larger in EVAc copolymers (10?10 to 10?8 cm2/s) than in PVAc (10?12 cm2/s). These data may be useful for design of membrane processes, for controlled delivery of drugs, and for application in packaging and storage of food, chemicals, and pharmaceuticals. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2041–2052, 2002 相似文献
208.
The curing kinetics of styrene (30 wt %) and cardanyl acrylate (70 wt %), which was synthesized from cardanol and acryloyl chloride, was investigated by differential scanning calorimetry under isothermal condition. The method allows determination of the most suitable kinetic model and corresponding parameters. All kinetic parameters including the reaction order, activation energy Ea and kinetic rate constant were evaluated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2034–2039, 2002 相似文献
209.
Vinh Q. Nguyen Jas S. Sanghera Brian Cole Pablo Pureza Frederic H. Kung Ishwar D. Aggarwal 《Journal of the American Ceramic Society》2002,85(8):2056-2058
Arsenic sulfide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of tellurium tetrachloride (TeCl4 ) to the glass. During melting, the chlorine from TeCl4 reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to produce optical fibers with significantly reduced loss due to hydrogen sulfide impurity content (1.5 dB/m). 相似文献
210.
The effect of relative humidity (RH) from ≪1% to 90% on the photodegradation and quantum efficiency for a partially-methylated
melamine acrylic coating exposed to UV/50°C condition has been investigated. The UV source is supplied by two 1000 W Xenon
arc solar simulators and the relative humidities are provided by specially designed humidity generators, which control relative
humidity in the 0 to 90% range to within <3% of the measured values. Radiation absorbed in the coating and degradation of
the films are measured by UV-visible and Fourier transform infrared spectroscopies, respectively. The degradation at a particular
RH/UV condition consists of four different modes: reactions taken place during post curing, hydrolysis due to water in the
film at a particular RH, photodegradation, and moisture-enhanced photodegradation. Total degradation, hydrolysis, and moisture-enhanced
photodegradation increase with increasing RH. At low relative humidities, photodegradation is an important degradation mode
but hydrolysis dominates the degradation at high RH levels. Moisture in the film is found to increase the quantum efficiency
of acrylic melamine coating photodegradation.
100 Bureau Dr., Stop 8621, Gaithersburg, MD 20899. 相似文献