全文获取类型
收费全文 | 4558篇 |
免费 | 293篇 |
国内免费 | 189篇 |
专业分类
电工技术 | 27篇 |
综合类 | 165篇 |
化学工业 | 1670篇 |
金属工艺 | 176篇 |
机械仪表 | 146篇 |
建筑科学 | 281篇 |
矿业工程 | 216篇 |
能源动力 | 504篇 |
轻工业 | 395篇 |
水利工程 | 75篇 |
石油天然气 | 247篇 |
武器工业 | 5篇 |
无线电 | 82篇 |
一般工业技术 | 539篇 |
冶金工业 | 242篇 |
原子能技术 | 110篇 |
自动化技术 | 160篇 |
出版年
2024年 | 10篇 |
2023年 | 62篇 |
2022年 | 93篇 |
2021年 | 142篇 |
2020年 | 142篇 |
2019年 | 132篇 |
2018年 | 140篇 |
2017年 | 117篇 |
2016年 | 116篇 |
2015年 | 109篇 |
2014年 | 225篇 |
2013年 | 278篇 |
2012年 | 280篇 |
2011年 | 370篇 |
2010年 | 256篇 |
2009年 | 277篇 |
2008年 | 254篇 |
2007年 | 287篇 |
2006年 | 273篇 |
2005年 | 216篇 |
2004年 | 178篇 |
2003年 | 164篇 |
2002年 | 126篇 |
2001年 | 96篇 |
2000年 | 105篇 |
1999年 | 97篇 |
1998年 | 79篇 |
1997年 | 74篇 |
1996年 | 54篇 |
1995年 | 54篇 |
1994年 | 46篇 |
1993年 | 28篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有5040条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(14):20062-20069
Photocatalytic N2 fixation is a promising and sustainable manufacturing process of ammonia (NH3); however, the NH3 production rate by this method is very low, thus severely restricting further application of this sustainable technology. Therefore, developing an efficient photocatalyst for N2 fixation under mild conditions is urgently required. Herein, ferroelectric Bi2WO6 materials with different surface oxygen defects were prepared, and the concentration of corresponding defects was controlled by adjusting the thermal reduction time. The abundant oxygen defects in Bi2WO6 can provide more reactive sites to promote the effective adsorption of N2, and the photogenerated charge carrier can be efficiently separated benefiting from the internal electric field. These would weaken the N2 triple bond and reduce the activation energy barrier for the conversion of N2 to NH3 under mild conditions. In the absence of sacrificial agents and cocatalysts, the optimized Bi2WO6 with oxygen defects shows an indigenous NH3 yield of 132.175 μmol·g-1·L-1·h-1, which is more than two times higher than that of the original Bi2WO6. Surprisingly, the Bi2WO6 with oxygen defects produced more than eight times NH3 (471.13 μmol·g-1·L-1·h-1) than that of the original Bi2WO6 when assisted by an external magnetic field, thus providing a new perspective for further enhancing the N2 fixation performance. 相似文献
2.
With the increase of industrialization and urbanization, humankind faces massive oil-based pollution due to tanker accidents, human error, and natural disasters. For this, hydrophobic sorbents are fabricated and their applications for the removal of oil from polluted water sources are investigated. These hydrophobic sorbents are prepared by the condensation reaction of poly(dimethylsiloxane) and tris[3-(trimethoxysilyl)propyl]isocyanurate cross-linker via bulk polymerization. The obtained sorbents exhibit high oil sorption capacity, fast absorption–desorption kinetics, and great reusability. Moreover, they can selectively absorb oil from the water surface, thus making them practical for water clean-up applications. 相似文献
3.
《International Journal of Hydrogen Energy》2019,44(11):5189-5202
Independent hydrogen production from petrochemical wastewater containing mono-ethylene glycol (MEG) via anaerobic sequencing batch reactor (ASBR) was extensively assessed under psychrophilic conditions (15–25 °C). A lab-scale ASBR was operated at pH of 5.50, and different organic loading rates (OLR) of 1.00, 1.67, 2.67, and 4.00 gCOD/L/d. The hydrogen yield (HY) progressed from 134.32 ± 10.79 to 189.09 ± 22.35 mL/gMEGinitial at increasing OLR from 1.00 to 4.00 gCOD/L/d. The maximum hydrogen content of 47.44 ± 3.60% was achieved at OLR of 4.0 gCOD/L/d, while methane content remained low (17.76 ± 1.27% at OLR of 1.0 gCOD/L/d). Kinetic studies using four different mathematical models were conducted to describe the ASBR performance. Furthermore, two batch-mode experiments were performed to optimize the nitrogen supplementation as a nutrient (C/N ratio), and assess the impact of salinity (as gNaCl/L) on hydrogen production. HY substantially dropped from 62.77 ± 4.09 to 6.02 ± 0.39 mL/gMEGinitial when C/N ratio was increased from 28.5 to 114.0. Besides, the results revealed that salinity up to 10.0 gNaCl/L has a relatively low inhibitory impact on hydrogen production. Eventually, the cost/benefit analysis showed that environmental and energy recovery revenues from ASBR were optimized at OLR of 4.0 gCOD/L/d (payback period of 7.13 yrs). 相似文献
4.
Junyu Chen Yuze Li Yuming Jiang Liucheng Mao Mi Lai Lixia Jiang Huihui Liu Zongxiu Nie 《Advanced functional materials》2021,31(52):2106743
Cancer remains an intractable medical problem. Rapid diagnosis and identification of cancer are critical to differentiate it from nonmalignant diseases. High-throughput biofluid metabolic analysis has potential for cancer diagnosis. Nevertheless, the present metabolite analysis method does not meet the demand for high-throughput screening of diseases. Herein, a high-throughput, cost-effective, and noninvasive urine metabolic profiling method based on TiO2/MXene-assisted laser desorption/ionization mass spectrometry (LDI-MS) is presented for the efficient screening of bladder cancer (BC) and nonmalignant urinary disease. Combined with machine learning, TiO2/MXene-assisted LDI-MS enables high diagnostic accuracy (96.8%) for the classification of patient groups (including 47 BC and 46 ureteral calculus (UC) patients) from healthy controls (113 cases). In addition, BC patients can also be identified from noncancerous UC individuals with an accuracy of 88.3% in the independent test cohort. Furthermore, metabolite variations between BC and UC individuals are investigated based on relative quantification, and related pathways are also discussed. These results suggest that this method, based on urine metabolic patterns, provides a potential tool for rapidly distinguishing urinary diseases and it may pave the way for precision medicine. 相似文献
5.
《International Journal of Hydrogen Energy》2020,45(1):1151-1157
The paper presents a calculated analysis of the equilibrium emission of nitrogen oxides on the exhaust of carburetor and diesel internal combustion engines. The temperature of fuel oxidation is assumed to be 1,400 °C while the pressure for carburetor and diesel engines is assumed to be 60 atm and 80 atm respectively. The studies have been carried out for natural and synthetic fuels such as hydrogen, ethanol, methanol, petroleum, diesel fuel and methane at the excess air coefficient corresponding to the fuel oxidation temperature of 1,400 °C. In the paper, the method for calculating the equilibrium composition based on the equilibrium constant and mass conservation equations has been applied. It is shown that with an increase in pressure from 1 atm to 60 atm for carburetor engines and up to 80 atm for diesel engines, the reaction of nitrogen dioxide formation may shift towards an increase in NO2. The formation of NO may be not affected by the increase in pressure by virtue of the fact that the reaction proceeds without changes in the amount. It has been determined that NO is the major atmospheric pollutant. However, it would be advisable to use more extensively the fuels characterized by the lowest output of nitrogen dioxide (methane and methanol), since nitrogen dioxide (NO2) related to the 2nd hazard class is appeared to be the most dangerous to humans. It has been revealed that the reduction in oxidation temperature using hydrogen as a fuel for electrochemical current generators may allow reducing nitrogen oxide emissions by more than an order of magnitude as compared to the best results for ICE. 相似文献
6.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
7.
结合芳烃联合装置的发展形势,通过对国内某4套典型芳烃联合装置运行能耗的构成进行分析,确定该类装置的主要能耗在于燃料、电和蒸汽的消耗。总结了目前国内外常用的芳烃联合装置节能降耗方法,利用实际经验和调研结果,从采用新型吸附剂、采用单台吸附塔新工艺、采用轻质解吸剂替代对二乙苯(PDEB)、优化吸附塔运行参数、加热炉节能优化和选用高效节能设备等角度探讨芳烃联合装置的节能降耗方法。芳烃联合装置节能降耗应该由设计单位和生产单位紧密结合,在设计阶段就应充分考虑生产过程面临的问题,充分优化工艺路线、方案和设备设计,尽可能降低装置的能耗。同样,装置运行过程中,生产部门应标准化、精细化管理,优化日常操作,从而进一步降低装置的操作能耗。 相似文献
8.
9.
The effects of NOx on the performance of proton exchange membrane (PEM) fuel cell were investigated through the introduction of a mixture containing NO and NO2, in a ratio of 9:1, into the cathode stream of a single PEM fuel cell. The NOx concentrations used in the experiments were 1480 ppm, 140 ppm and 10 ppm, which cover a range of three orders. The experimental results obtained from the tests of durability, polarization, reversibility and electrochemical impedance spectroscopy (EIS) showed a detrimental effect of NOx on the cell performance. The electrochemical measurements results suggested that the impacts of NOx are mainly resulted from the superposition of the oxygen reduction reaction (ORR), NO and HNO2 oxidation reactions, and the increased cathodic impedance. Complete recovery of the cell performance was reached after operating the cell with clean air and then purging with N2 for hours. 相似文献
10.
SVK8 3S型氮气压缩机是由沈阳鼓风机厂制造、为义马煤气配套的低压氮气压缩机 ,共两套 ,于 2 0 0 0年 1 2月开始调试。为节约工程基建资金 ,取消原设计两台中压氮气压缩机 ,由杭氧产两台3TYS89+2TYS60型氧气透平压缩机临时压送氮气 ,向外供中压氮 ,来取代中压氮气压缩机 ,流程示意图如图 1所示。图 1 氧、氮压机工艺流程配置图1 事故情况2 0 0 0年 1 2月 2 7日中午 1 1∶3 5 ,接总调度室通知 ,要求中午 1 2∶0 0向长输管线供中压氮气。当时 ,一台氮压机试车完毕正在运行 ,一台氧压机试车完毕压氧正在运行 ,将由氧压机临时压送氮气外供… 相似文献