全文获取类型
收费全文 | 2465篇 |
免费 | 182篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 21篇 |
综合类 | 2篇 |
化学工业 | 625篇 |
金属工艺 | 125篇 |
机械仪表 | 171篇 |
建筑科学 | 40篇 |
能源动力 | 141篇 |
轻工业 | 208篇 |
水利工程 | 21篇 |
石油天然气 | 5篇 |
武器工业 | 2篇 |
无线电 | 351篇 |
一般工业技术 | 489篇 |
冶金工业 | 113篇 |
原子能技术 | 55篇 |
自动化技术 | 283篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 62篇 |
2021年 | 99篇 |
2020年 | 61篇 |
2019年 | 63篇 |
2018年 | 83篇 |
2017年 | 82篇 |
2016年 | 84篇 |
2015年 | 78篇 |
2014年 | 119篇 |
2013年 | 166篇 |
2012年 | 221篇 |
2011年 | 254篇 |
2010年 | 162篇 |
2009年 | 182篇 |
2008年 | 128篇 |
2007年 | 87篇 |
2006年 | 96篇 |
2005年 | 87篇 |
2004年 | 72篇 |
2003年 | 58篇 |
2002年 | 49篇 |
2001年 | 54篇 |
2000年 | 53篇 |
1999年 | 42篇 |
1998年 | 67篇 |
1997年 | 26篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2652条查询结果,搜索用时 15 毫秒
981.
We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoO
x
). The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential
for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive
cobalt oxide. Compared to bare CoO
x
thin-film (CoO
x
TF) electrodes, the CuNFs@CoO
x
electrodes exhibited a significant enhancement of rate performance by at least six-fold at an input current density of 3C-rate.
Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge
transfer, and facile stress relaxation from the embedded CuNF network. Consequently, the CuNFs@CoO
x
composite structure demonstrated here can be used as a promising high-performance electrode for Li-ion batteries. 相似文献
982.
Lee WH Rhee CK Koo J Lee J Jang SP Choi SU Lee KW Bae HY Lee GJ Kim CK Hong SW Kwon Y Kim D Kim SH Hwang KS Kim HJ Ha HJ Lee SH Choi CJ Lee JH 《Nanoscale research letters》2011,6(1):258-11
Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method. Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device. The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems. This study convincingly demonstrates that the large enhancements in the thermal conductivities of EG-based ZnO nanofluids tested are beyond the lower and upper bounds calculated using the models of the Maxwell and Nan et al. with and without the interfacial thermal resistance. 相似文献
983.
Sang?Chul?Oh Byeong?Ju?Bae Ki?Yeon?Yang Moo?Hyun?Kwon Heon?LeeEmail author 《Metals and Materials International》2011,17(5):771-775
Al plate was patterned by a direct embossing process. An electroformed Ni plate with a nano-sized surface protrusion pattern
was used as an embossing mold. The Ni stamp with a nano-sized surface protrusion pattern was pressed onto an electro-polished
Al plate; thus, a reversed Al nano-pattern was formed on the Al surface by the localized plastic deformation of Al. The Al
plate was softened by annealing at 400 °C for 5 min; thus, high-fidelity pattern transfer was achieved at a low embossing
pressure. 相似文献
984.
Jun-Ho Bae Sung-Jin Kim Moon-Saeng Kim Chul Kim 《Journal of Mechanical Science and Technology》2011,25(9):2277-2284
The safety valves used in liquefied natural gas — floating production storage and offloading (LNG-FPSO) ships play an important
role in maintaining a fixed pressure by controlling the release of liquefied natural gas (LNG) from pipes in an LNG piping
system. Therefore, the discharge coefficient is regarded as the most important parameter influencing the valve performance.
In order to satisfy the ship’s classification criteria, the discharge coefficient of the safety valve must usually be over
0.8. Despite the importance of a good understanding of the flow phenomena inside the safety valve for the improvement of the
discharge coefficient, the successful design of valves depends on experience and experiments in an industrial field. In this
study, a computational fluid dynamics (CFD) investigation was carried out with ANSYS-CFX software to observe the flow phenomena
inside the valve and to determine the discharge coefficients from changes in the valve lift, which is the distance between
the exit of the nozzle and the lower part of the disc plate. The discharge coefficients obtained were also verified through
comparison with available experimental data. 相似文献
985.
Kim KH Shon ZH Nguyen HT Jung K Park CG Bae GN 《The Science of the total environment》2011,409(19):3801-3811
Concentrations of total gaseous mercury (TGM) were measured continuously at four urban residential locations (G (Guro-gu); N (Nowon-gu); S (Songpa-gu); and Y (Yongsan-gu)) in Seoul, Korea from 2004 to 2009. The mean concentrations of Hg at these sites were found on the order of N (3.98 ± 1.68 ng m− 3), S (3.87 ± 1.56 ng m− 3), G (3.80 ± 1.60 ng m− 3), and Y (3.36 ± 1.55 ng m− 3). Evidence indicates that the spatial distribution of Hg should be affected by the combined effects of both local anthropogenic (incineration facilities and thermal power plants) and natural (soil) emission sources in association with the meteorological parameters. Inspection of the Hg temporal patterns indicates the co-existence of contrasting seasonal patterns between the central site Y (winter dominance) and all other outbound sites near city borders (summer dominance). The long-term trend of Hg, if examined by combining our previous studies and the present one, shows that Hg levels in this urban area declined gradually across decadal periods despite slight variabilities in spatial scale: (1) above 10 ng m− 3 in the late 1980s, (2) ~ 5 ng m− 3 in the late 1990s, and (3) ~ 3 ng m− 3 toward the late 2000s. The results of the principal component analysis along with observed differences in seasonal patterns (between study sites) suggest that Hg distributions between different urban sites are greatly distinguishable with strong source signatures at each individual site. 相似文献
986.
Bae Jinhyun Jo Hyeontaek Yoon Youngbin 《Journal of Mechanical Science and Technology》2022,36(11):5755-5764
Journal of Mechanical Science and Technology - This study analyzes the effect of changes in input parameters on the prediction results in combustion instability. First, applying the centroid... 相似文献
987.
Jozeph Park Chang Sun Kim Yang Soo Kim Yun Chang Park Hyung Jin Park Byeong-Soo Bae Jin-Seong Park Hyun-Suk Kim 《Journal of Electroceramics》2016,36(1-4):129-134
The effect of ITO and Mo electrodes on the electrical properties and stability of In-Ga-Zn-O (IGZO) thin film transistors (TFTs) are investigated. While the field effect mobility values of the devices employing ITO and Mo electrodes are similar, the former exhibit smaller threshold voltage (Vth) and subthreshold swing (SS). It is suggested that the relatively large workfunction of Mo (4.7 eV) compared to that of ITO (4.4?~?4.5 eV) induces a large Schottky barrier at the Mo/IGZO junction, which prohibits the effective injection of electrons from the metal into the IGZO semiconductor. The workfunction of IGZO is usually reported to be approximately 4.5 eV. The device stability of the two types of TFTs under negative bias stress (NBS) and positive bias stress (PBS) is similar, which implies that the degradation of the devices under bias stress is mainly affected by the trapping of carriers at the IGZO/gate insulator interface. In the presence of illumination, the devices using optically transparent ITO electrodes allow the penetration of a more abundant concentration of photons into the IGZO active layer, and thus undergo larger Vth shifts under negative bias illumination stress (NBIS). However, under positive bias illumination stress (PBIS), the TFTs using ITO exhibit smaller positive Vth shifts. The latter phenomenon is suggested to result from the excess photo-induced electrons in the bulk that counter the effect of electron trapping near the IGZO/gate insulator boundary. 相似文献
988.
Development of Anionically Decorated Caged Neurotransmitters: In Vitro Comparison of 7‐Nitroindolinyl‐ and 2‐(p‐Phenyl‐o‐nitrophenyl)propyl‐Based Photochemical Probes 下载免费PDF全文
Dr. Srinivas Kantevari Dr. Stefan Passlick Dr. Hyung‐Bae Kwon Dr. Matthew T. Richers Prof. Bernardo L. Sabatini Prof. Graham C. R. Ellis‐Davies 《Chembiochem : a European journal of chemical biology》2016,17(10):953-961
Neurotransmitter uncaging, especially that of glutamate, has been used to study synaptic function for over 30 years. One limitation of caged glutamate probes is the blockade of γ‐aminobutyric acid (GABA)‐A receptor function. This problem comes to the fore when the probes are applied at the high concentrations required for effective two‐photon photolysis. To mitigate such problems one could improve the photochemical properties of caging chromophores and/or remove receptor blockade. We show that addition of a dicarboxylate unit to the widely used 4‐methoxy‐7‐nitroindolinyl‐Glu (MNI‐Glu) system reduced the off‐target effects by about 50–70 %. When the same strategy was applied to an electron‐rich 2‐(p‐Phenyl‐o‐nitrophenyl)propyl (PNPP) caging group, the pharmacological improvements were not as significant as in the MNI case. Finally, we used very extensive biological testing of the PNPP‐caged Glu (more than 250 uncaging currents at single dendritic spines) to show that nitro‐biphenyl caging chromophores have two‐photon uncaging efficacies similar to that of MNI‐Glu. 相似文献
989.
Jin-Young Kim Hoonbae Kim Shang Hyeun Park Taewon Jeong Min Jong Bae Yong Churl Kim Intaek Han Donggeun Jung SeGi Yu 《Organic Electronics》2012,13(12):2959-2966
AC driven inorganic electroluminescence (EL) of the carbon nanotube (CNT)-polymer/phosphor composite was fabricated to investigate the effect of the critical percolation threshold by CNT concentration on EL performance. In order to control the appropriate CNT condition in EL device, CNTs were shortened by cryogenic crushing and purified by thermal treatment. Among various CNT concentrations in the composite film, the critical percolation threshold can be found to be 0.0925 wt.% by fitting conductivity data of the composite film. Near the critical percolation threshold of a CNT concentration, the EL performances of the composite EL were greatly increased compared to the reference EL. The tunneling barrier thickness at the ZnS–CuxS contact could become thin to induce more charge carrier tunneling into ZnS host lattice by the local field enhancement of CNTs, resulting in increased electron–hole recombination to produce more light emission. 相似文献
990.
YC Chen RZ Lin H Qi Y Yang H Bae JM Melero-Martin A Khademhosseini 《Advanced functional materials》2012,22(10):2027-2039
The generation of functional, 3D vascular networks is a fundamental prerequisite for the development of many future tissue engineering-based therapies. Current approaches in vascular network bioengineering are largely carried out using natural hydrogels as embedding scaffolds. However, most natural hydrogels present a poor mechanical stability and a suboptimal durability, which are critical limitations that hamper their widespread applicability. The search for improved hydrogels has become a priority in tissue engineering research. Here, the suitability of a photopolymerizable gelatin methacrylate (GelMA) hydrogel to support human progenitor cell-based formation of vascular networks is demonstrated. Using GelMA as the embedding scaffold, it is shown that 3D constructs containing human blood-derived endothelial colony-forming cells (ECFCs) and bone marrow-derived mesenchymal stem cells (MSCs) generate extensive capillary-like networks in vitro. These vascular structures contain distinct lumens that are formed by the fusion of ECFC intracellular vacuoles in a process of vascular morphogenesis. The process of vascular network formation is dependent on the presence of MSCs, which differentiate into perivascular cells occupying abluminal positions within the network. Importantly, it is shown that implantation of cell-laden GelMA hydrogels into immunodeficient mice results in a rapid formation of functional anastomoses between the bioengineered human vascular network and the mouse vasculature. Furthermore, it is shown that the degree of methacrylation of the GelMA can be used to modulate the cellular behavior and the extent of vascular network formation both in vitro and in vivo. These data suggest that GelMA hydrogels can be used for biomedical applications that require the formation of microvascular networks, including the development of complex engineered tissues. 相似文献