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991.
Some studies have discussed the potential and challenges related to the use of artificial intelligence (AI) in government. However, there are few empirical studies that have examined factors that influence the use of AI in government. By collecting policy documents and empirical data from the government, IT enterprises, and the public in China, we identified the influencing factors in the three stages of government adoption, implementation, and decision-making. The research results show that the influencing factors of government application of AI are different at different stages and with different stakeholders’ backgrounds. 相似文献
992.
《International Journal of Hydrogen Energy》2021,46(62):31523-31532
The synthesis of ammonia (NH3) from electrochemical nitrogen reduction reaction (NRR) under environmental conditions is a promising technology. Compared with the traditional artificial nitrogen fixation process by the Haber-Bosch process, electrochemical nitrogen reduction reaction (NRR) requires no harsh reaction conditions. In this work, we report that Bi-doped CeO2 nanocubes show high NRR activity as electrocatalysts. The NH3 yield of 17.83 μgh−1 mg−1cat. and the Faradaic Efficiency (FE) of 1.61% at −0.9 V are achieved in 0.1 M Na2SO4. The performance is much higher than that for the traditional CeO2 nanoparticles. The detailed analysis indicates that both the Bi doping and the cube morphology are critical for this encouraging NRR performance. The mechanism for improving NRR is further explored with first-principle calculations, demonstrating the importance of Bi-doping for performance enhancement. 相似文献
993.
Xiao-juan Li Yi-xiang Xu Xiang Li Zhi-jiang Jin Jin-yuan Qian 《International Journal of Hydrogen Energy》2021,46(7):5537-5547
Ambient condition, especially the wind condition, is an important factor to determine the behavior of hydrogen diffusion during hydrogen release. However, only few studies aim at the quantitative study of the hydrogen diffusion in a wind-exist condition. And very little researches aiming at the variable wind condition have been done. In this paper, the hydrogen diffusion in different wind condition which including the constant wind velocity and the variable wind velocity is investigated numerically. When considering the variable wind velocity, the UDF (user defined function) is compiled. Characteristics of the FGC (flammable gas cloud) and the HMF (hydrogen mass fraction) are analyzed in different wind condition and comparisons are made with the no-wind condition. Results indicate that the constant wind velocity and the variable wind velocity have totally different effect for the determination of hydrogen diffusion. Comparisons between the constant wind velocity and the variable wind velocity indicate that the variable wind velocity may cause a more dangerous situation since there has a larger FGC volume. More importantly, the wind condition has a non-negligible effect when considering the HMF along the radial direction. As the wind velocity increases, the distribution of the HMF along the radial direction is not Gaussian anymore when the distance between the release hole and the observation line exceeds to a critical value. This work can be a supplement of the research on the hydrogen release and diffusion and a valuable reference for the researchers. 相似文献
994.
Chengjing Mi Yanping Huang Fengtao Chen Kui Wu Weiyan Wang Yunquan Yang 《International Journal of Hydrogen Energy》2021,46(1):875-885
Methylcyclohexane is a very promising liquid organic hydrogen carrier, but its dehydrogenation mechanism on Pt-based bimetallic catalysts is not yet clear. In order to understand the catalytic dehydrogenation of methylcyclohexane on Ni–Pt(111), DFT calculations were performed and the calculation results were compared with the corresponding values on Pt(111). It is shown that because the electronegativity of Ni atoms is less than that of Pt atoms, electrons transfer from Ni atoms to Pt atoms. Compared with Pt(111), the binding energy (the absolute value of the adsorption energy) of related species on Ni–Pt(111) surface was smaller, indicating that the binding strength between these species and the surface metal atoms on Ni–Pt(111) is weaker. In the stable adsorption configurations on Ni–Pt(111), almost all the metal atoms forming chemical bonds with the adsorbates were Pt atoms, indicating that Pt was the main active component. Although the actual catalytic reaction is more complicated, this study provided some insights into one of the important aspects. 相似文献
995.
Yuan Shao Lucy Kavi Meleah Boyle Lydia M. Louis Walkiria Pool Stephen B. Thomas Sacoby Wilson Ana M. Rule Lesliam Quiros-Alcala 《Indoor air》2021,31(4):1144-1153
Hairdressers are exposed to particulate matter (PM), a known air pollutant linked to adverse health effects. Still, studies on occupational PM exposures in hair salons are sparse. We characterized indoor air PM concentrations in three salons primarily serving an African/African American (AA) clientele, and three Dominican salons primarily serving a Latino clientele. We also assessed the performance of low-cost sensors (uRAD, Flow, AirVisual) by comparing them to high-end sensors (DustTrak) to conduct air monitoring in each salon over 3 days to quantify work shift concentrations of PM2.5, respirable PM (RPM), and PM10. We observed high spatial and temporal variability in 30-min time-weighted average (TWA) RPM concentrations (0.18–5518 μg/m3). Readings for the uRAD and AirVisual sensors were highly correlated with the DustTrak (R2 = 0.90–0.99). RPM 8-hour TWAs ranged from 18 to 383 µg/m3 for AA salons, and 9–2115 µg/m3 for Dominican salons. Upper 95th percentiles of daily RPM exposures ranged from 439 to 2669 µg/m3. The overall range of 30-min TWA PM2.5 and PM10 concentrations was 0.13–5497 and 0.36-,541 μg/m3, respectively. Findings suggest that hairdressers could be overexposed to RPM during an 8-hour shift. Additional comprehensive monitoring studies are warranted to further characterize temporal and spatial variability of PM exposures in this understudied occupational population. 相似文献
996.
摘 要:目的 了解六六六(hexachlorocyclohexanes,HCHs)与滴滴涕(dichloro diphenyl trichloroethanes,DDTs)在杭州湾南岸滩涂沉积物中的污染现状。方法 于2018年4月,采集杭州湾南岸地区4个采样点不同深度(0~80 cm)滩涂沉积物,利用气相色谱-串联质谱法(gas chromatography tandem mass spectrometry, GC-MS/MS)测定了该区域中HCHs与DDTs的含量,对其分布规律进行分析,使用共识沉积物质量基准法对其生态学风险进行了评估。结果 所有样品中均检出,HCHs与DDTs含量分别为4.20~6.24 μg/kg与3.37~4.73 μg/kg,主要以β-HCH、δ-HCH以及DDE为主,其污染主要来源于历史性工业品,整体污染处于较低水平;20.3%的沉积物样品中DDEs含量以及28.1%的样品DDTs总量介于阈值效应浓度(threshold concentration, TECs) 和可能效应浓度(probable effect concentration, PECs)之间。结论 杭州湾南岸沉积物中HCHs与DDTs的污染处于较低水平,具有较小的生态学风险。 相似文献
997.
Xingwang Zhao Jingnan Sun Sumei Liu Zhengwei Long Yonggao Yin Qingyan Chen 《Indoor air》2021,31(5):1614-1624
Currently, the thermal environment in airplane cockpits is unsatisfactory and pilots often complain about a strong draft sensation in the cockpit. It is caused by the unreasonable air supply diffusers design. One of the best approaches to design a better cockpit environment is the adjoint method. The method can simultaneously and efficiently identify the number, size, location, and shape of air supply inlets, and the air supply parameters. However, the real air diffuser needed to design often have grilles, especially in the airplane cockpit, and the current method can only design the inlet as an opening. This study combined the adjoint method with the momentum method to directly identify the optimal air supply diffusers with grilles to create optimal thermal environment in an airplane cockpit (1) under ideal conditions and (2) with realistic constraints. Under the ideal conditions, the resulting design provides an optimal thermal environment for the cockpit, but it might not be feasible in practice. The design with realistic constraints provides acceptable thermal comfort in the cockpit, but it is not optimal. Thus, there is an engineering trade-off between design feasibility and optimization. All in all, the adjoint method with the momentum method can be effectively used to identify real air supply diffusers. 相似文献
998.
格点量子色动力学(格点QCD)是研究夸克、胶子等微观粒子间相互作用的重要理论和方法. 通过将时空离散化为四维结构网格, 并将量子色动力学的基本场量定义在网格上, 让研究人员可以使用数值模拟方法, 从第一性原理出发研究强子间相互作用和性质, 但这个过程中的计算量极大, 需要进行大规模并行计算. 格点QCD计算的核心基础为格点QCD求解器, 是程序运行主要的计算热点模块. 本文研究在国产异构计算平台下格点QCD求解器的实现与优化, 提出一套格点QCD求解器的设计实现, 实现了BiCGSTAB求解器, 显著降低了迭代次数; 通过对奇偶预处理技术, 降低了所求问题的计算规模; 针对国产异构加速卡的特点, 优化了Dslash模块的访存操作. 实验测试表明, 相比优化前的求解器获得了约30倍的加速比, 为国产异构超算下格点QCD软件性能优化提供了有益的参考价值. 相似文献
999.
《International Journal of Hydrogen Energy》2022,47(48):20803-20815
The incomplete polymerization of graphite carbon nitride (g-C3N4) due to the kinetic problems resulted in its high recombination rate of photo-generated electron-hole pairs. Hence, cyano-containing carbon nitride with coral-like morphology (CCCN) was prepared by the molten salt method with heptazine-based melem as precursor, which presented excellent separation rate of photo-generated electron-hole pairs. SEM exhibited that CCCN owned coral-like morphology which exposed ample active sites and enhanced the capture ability of visible light while FT-IR and XPS demonstrated that cyano groups appearing in coral-like carbon nitride enhanced the separation rate of photo-induced charge carriers. The synergistic effect of coral-like morphology and cyano groups endowed CCCN-15% with superior performance of both the photocatalytic H2 evolution (4207 μmol h?1 g?1) and Cr (Ⅵ) reduction (k = 0.059 min?1), approximately 16.8 and 6.0 times that of g-C3N4, which was comparable among the similar materials. Density functional theory calculation (DFT) revealed that cyano groups decreased the bandgap and strengthened the activation degree of reaction substrate, which enhanced the thermodynamic driving force and the interaction between catalyst and substrate. This work provided a potential strategy for both the renewable energy generation and environmental restoration. 相似文献
1000.
《International Journal of Hydrogen Energy》2022,47(68):29467-29480
The effects of surface and interior degradation of the gas diffusion layer (GDL) on the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs) have been investigated using three freeze-thaw accelerated stress tests (ASTs). Three ASTs (ex-situ, in-situ, and new methods) are designed from freezing ?30 °C to thawing 80 °C by immersing, supplying, and bubbling, respectively. The ex-situ method is designed for surface degradation of the GDL. Change of surface morphology from hydrophobic to hydrophilic by surface degradation of GDL causes low capillary pressure which decreased PEMFC performance. The in-situ method is designed for the interior degradation of the GDL. A decrease in the ratio of the porosity to tortuosity by interior degradation of the GDL deteriorates PEMFC performance. Moreover, the new method showed combined effects for both surface and interior degradation of the GDL. It was identified that the main factor that deteriorated the fuel cell performance was the increase in mass transport resistance by interior degradation of GDL. In conclusion, this study aims to investigate the causes of degraded GDL on the PEMFC performance into the surface and interior degradation and provide the design guideline of high-durability GDL for the PEMFC. 相似文献