全文获取类型
收费全文 | 40346篇 |
免费 | 4511篇 |
国内免费 | 2082篇 |
专业分类
电工技术 | 5301篇 |
综合类 | 2298篇 |
化学工业 | 7481篇 |
金属工艺 | 1279篇 |
机械仪表 | 2052篇 |
建筑科学 | 909篇 |
矿业工程 | 498篇 |
能源动力 | 8327篇 |
轻工业 | 3684篇 |
水利工程 | 191篇 |
石油天然气 | 553篇 |
武器工业 | 237篇 |
无线电 | 4811篇 |
一般工业技术 | 4280篇 |
冶金工业 | 917篇 |
原子能技术 | 418篇 |
自动化技术 | 3703篇 |
出版年
2024年 | 88篇 |
2023年 | 883篇 |
2022年 | 1163篇 |
2021年 | 2313篇 |
2020年 | 1742篇 |
2019年 | 1571篇 |
2018年 | 1342篇 |
2017年 | 1630篇 |
2016年 | 1530篇 |
2015年 | 1586篇 |
2014年 | 2370篇 |
2013年 | 2522篇 |
2012年 | 2702篇 |
2011年 | 3601篇 |
2010年 | 2664篇 |
2009年 | 2405篇 |
2008年 | 2454篇 |
2007年 | 2571篇 |
2006年 | 2159篇 |
2005年 | 1740篇 |
2004年 | 1428篇 |
2003年 | 1160篇 |
2002年 | 1015篇 |
2001年 | 836篇 |
2000年 | 673篇 |
1999年 | 517篇 |
1998年 | 423篇 |
1997年 | 314篇 |
1996年 | 279篇 |
1995年 | 242篇 |
1994年 | 213篇 |
1993年 | 169篇 |
1992年 | 143篇 |
1991年 | 88篇 |
1990年 | 79篇 |
1989年 | 66篇 |
1988年 | 42篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 40篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 9篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Sabyasachi Swain 《国际聚合物材料杂志》2019,68(13):796-804
In this study, a novel micro porous honeycomb structured Crg-GG-IPN material was incepted to be applicable as scaffold and accomplished. The hydrophilicity was confirmed by FT-IR and OCA. Amorphous nature and micro-rough surface were confirmed by XRD and AFM. Void fraction was 0.61?±?0.04. Void space, hemocompatibility and platelet adhesion were captured by SEM. Degradability of the material was confirmed by in-vitro degradation study. Incision method using mice model was a clear evidence for cell attachment and non-toxicity and was confirmed from hematology and histopathology. Thus, it appears that Crg-GG scaffolds can be useful as wound healing material for clinical applications. 相似文献
72.
Jing Wang Hangyan Chen Su‐Huai Wei Wan‐Jian Yin 《Advanced materials (Deerfield Beach, Fla.)》2019,31(17)
Tetrahedral coordination structures, e.g. crystalline Si, GaAs, CdTe, and octahedral coordination structures, e.g. perovskites, represent two classes of successful crystal structures hitherto for solar cell absorbers. Here, via first‐principles calculations and crystal symmetry analysis, the two classes of semiconductors are shown exhibiting complementary properties in terms of bond covalency/ionicity, optical property, defect tolerance, and stability, which are correlated with their respective coordination number. Therefore, a spinel structure is proposed, which combines tetrahedral and octahedral coordination into a single crystal structure, as an alternative to perovskite and conventional semiconductors for potential photovoltaic applications. The case studies of a class of 105 spinel AB2X4 systems identify five spinel compounds HgAl2Se4, HgIn2S4, CdIn2Se4, HgSc2S4, and HgY2S4 as promising solar cell absorbers. In particular, HgAl2Se4 has suitable bandgap (1.36 eV by GW0 calculation), small direct–indirect bandgap difference (24 meV), appropriate carrier effective mass (me = 0.08 m0, and mh = 0.69 m0), strong optical absorption, and high dynamic stability. This study suggests that crystal systems with mixed tetrahedral and octahedral coordination may open a viable route for emerging solar cell absorbers. 相似文献
73.
Maliazurina Saad Ik Hyun Lee Tae-Sun Choi 《International journal of imaging systems and technology》2019,29(4):561-576
Quantitative reasoning in medical decision science relies on the delineation of pathological objects. For example, evidence-based clinical decisions regarding lung diseases require the segmentation of nodules, tumors, or cancers. Non-small cell lung cancer (NSCLC) tends to be large sized, irregularly shaped, and grows against surrounding structures imposing challenges in the segmentation, even for expert clinicians. An automated delineation tool based on spatial analysis was developed and studied on 25 sets of computed tomography scans of NSCLC. Manual and automated delineations were compared, and the proposed method exhibited robustness in terms of the tumor size (5.32–18.24 mm), shape (spherical or irregular), contouring (lobulated, spiculated, or cavitated), localization (solitary, pleural, mediastinal, endobronchial, or tagging), and laterality (left or right lobe) with accuracy between 80% and 99%. Small discrepancies observed between the manual and automated delineations may arise from the variability in the practitioners' definitions of region of interest or imaging artifacts that reduced the tissue resolution. 相似文献
74.
《International Journal of Hydrogen Energy》2021,46(67):33523-33540
The metal-supported solid oxide fuel cell (MS-SOFC) is of current research interest in the clean energy field due to its high performance, quick start-up, thermal cycle stability, and lower raw material cost compared to the conventional cermet-based SOFC. To efficiently operate a MS-SOFC using complex hydrocarbon and logistic fuels, it is required to introduce an internal reforming catalyst within the anode metal scaffold. This review article discusses some examples of the performance of MS-SOFCs under hydrocarbon and logistic fuels with and without an additional reforming catalyst. We also discuss the performance improvement of conventional cermet-based SOFCs by adding reforming catalysts via the infiltration method. This information can be directly applied to future MS-SOFC applications. Furthermore, this review article proposes possible novel methods such as direct precursor infiltration, catalyst-anode premixing, and atomic layer deposition methods to introduce the reforming catalyst into a MS-SOFC for improving its initial electrochemical performance and long-term stability under hydrocarbon and logistics fuel. 相似文献
75.
《International Journal of Hydrogen Energy》2021,46(73):36569-36580
Hydrogen energy utilization is expected due to its environmental and energy efficiencies. However, many issues remain to be solved in the social implementation of hydrogen energy through water electrolysis. This analyzes and compares the energy consumption and GHG emissions of fossil fuel-derived hydrogen and gasoline energy systems over their entire life cycle. The results demonstrate that for similar vehicle weights, the hydrogen energy system consumes 1.8 MJ/km less energy and emits 0.15 kg-CO 2 eq./km fewer GHG emissions than those of the gasoline energy system. Hydrogen derived from fossil fuels may contribute to future energy systems due to its stable energy supply and economic efficiency. Lowering the power source carbon content also improved the environmental and energy efficiencies of hydrogen energy derived from fossil fuels. 相似文献
76.
Zhen Wu Jing Yao Pengfei Zhu Fusheng Yang Xiangyu Meng Sandra Kurko Zaoxiao Zhang 《International Journal of Hydrogen Energy》2021,46(19):11183-11198
Advanced biogas power generation technology has been attracting attentions, which contributes to the waste disposal and the mitigation of greenhouse gas emissions. This work proposes and models a novel biogas-fed hybrid power generation system consisting of solid oxide fuel cell, water gas shift reaction, thermal swing adsorption and proton exchange membrane fuel cell (SOFC-WGS-TSA-PEMFC). The thermodynamic, exergetic, and thermo-economic analyses of this hybrid system for power generation were conducted to comprehensively evaluate its performance. It was found that the novel biogas-fed hybrid system has a gross energy conversion efficiency of 68.63% and exergy efficiency of 65.36%, indicating high efficiency for this kind of hybrid power technology. The market sensitivity analysis showed that the hybrid system also has a low sensitivity to market price fluctuation. Under the current subsidy level for the distributed biogas power plant, the levelized cost of energy can be lowered to 0.02942 $/kWh for a 1 MW scale system. Accordingly, the payback period and annual return on investment can reach 1.4 year and about 20%, respectively. These results reveal that the proposed hybrid system is promising and economically feasible as a distributed power plant, especially for the small power scale (no more than 2 MW). 相似文献
77.
Abd Essalam Badoud Farid Merahi Belkacem Ould Bouamama Saad Mekhilef 《International Journal of Hydrogen Energy》2021,46(47):24011-24027
This work presents a complete bond graph modeling of a hybrid photovoltaic-fuel cell-electrolyzer-battery system. These are multi-physics models that will take into account the influence of temperature on the electrochemical parameters. A bond graph modeling of the electrical dynamics of each source will be introduced. The bond graph models were developed to highlight the multi-physics aspect describing the interaction between hydraulic, thermal, electrochemical, thermodynamic, and electrical fields. This will involve using the most generic modeling approach possible for managing the energy flows of the system while taking into account the viability of the system. Another point treated in this work is to propose. In this work, a new strategy for the power flow management of the studied system has been proposed. This strategy aims to improve the overall efficiency of the studied system by optimizing the decisions made when starting and stopping the fuel cell and the electrolyzer. It was verified that the simulation results of the proposed system, when compared to simulation results presented in the literature, that the hydrogen demand is increased by an average of 8%. The developed management algorithm allows reducing the fuel cell degradation by 87% and the electrolyzer degradation by 65%. As for the operating time of the electrolyzer, an increment of 65% was achieved, thus improving the quality of the produced hydrogen. The Fuel Cell's running time has been decreased by 59%. With the ambition to validate the models proposed and the associated commands, the development of this study gave rise to the creation of an experimental platform. Using this high-performance experimental platform, experimental tests were carried out and the results obtained are compared with those obtained by simulation under the same metrological conditions. 相似文献
78.
《Planning》2019,(2)
皮肤T细胞淋巴瘤(cutaneous T cell lymphoma,CTCL)大多属于惰性淋巴瘤,病情进展缓慢,患者确诊时多处于疾病早期。局部用药和物理治疗在CTCL治疗中占重要地位,包括局部外用皮质类固醇激素、免疫抑制剂、维A酸,放疗及光疗等。近年来,有研究对CTCL传统局部用药和物理治疗方法的有效性和安全性进行了重新评估。同时,新型CTCL局部用药和物理治疗策略也不断涌现,如局部外用他扎罗汀、瑞喹莫特,紫外线A联合新型光敏剂的光化学疗法和光动力治疗等。本文对CTCL局部用药和物理治疗的研究进展作一综述。 相似文献
79.
《International Journal of Hydrogen Energy》2019,44(58):30524-30531
The recent interest in microbial electrolysis cell (MEC) technology has led the research platform to develop full biological MECs (bioanode-biocathode, FB-MEC). This study focused on biohydrogen production from a biologically catalyzed MEC. A bioanode and a biocathode were initially enriched in a half biological MFC (bioanode-abiocathode, HB-MFC) and a half biological MEC (abioanode-biocathode, HB-MEC), respectively. The FB-MEC was established by transferring the biocathode of the HB-MEC and the bioanode of the HB-MFC to a two-chamber MEC. The FB-MEC was operated under batch (FB-MEC-B) and recirculation batch (FB-MEC-RB) modes of operation in the anodic chamber. The FB-MEC-B reached a maximum current density of 1.5 A/m2 and the FB-MEC-RB reached a maximum current density of 2.5 A/m2 at a similar applied voltage while the abiotic control system showed the maximum of 0.2 A/m2. Hydrogen production rate decreased in the FB-MEC compared to that of the HB-MEC. However, the cathodic hydrogen recovery increased from 42% obtained in the HB-MEC to 56% in the FB-MEC-B and 65% in the FB-MEC-RB, suggesting the efficient oxidation and reduction rates in the FB-MEC compared to the HB-MEC. The onset potential for hydrogen evolution reaction detected by linear sweep voltammetry analysis were −0.780 and −0.860 V vs Ag/AgCl for the FB-MEC-RB and the FB-MEC-B (−1.26 for the abiotic control MEC), respectively. Moreover, the results suggested that the FB-MEC worked more efficiently when the biocathode and the bioanode were enriched initially in half biological systems before transferring to the FB-MEC compared to that of the simultaneously enriched in one system. 相似文献
80.
《International Journal of Hydrogen Energy》2019,44(2):1166-1173
Oxygen can only be reduced at the quadruple phase boundary (catalyst, carbon support, ionomer and oxygen) of the cathode catalyst layer with non-conducting electrocatalyst. To maximize the quadruple phase boundary sites is crucial to increase the peak power density of each membrane electrode assembly. The quadruple phase boundary is depending on the ratio of catalyst, carbon support and ionomer. The loading of catalyst layer is also crucial to the fuel cell performance. In this study, non-stoichiometric α-MnO2 manganese dioxide nanorod material has been synthesized and the ratios of carbon, ionomer and catalyst loadings were optimized in alkaline membrane fuel cell. In total, ten membrane electrode assemblies have been manufactured and tested. Taguchi design method has been applied in order to understand the effect of each parameter. The conclusion finds out the ionomer has more influence on the alkaline membrane fuel cell peak power performance than carbon and loading. 相似文献