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991.
Missing data is a serious issue in software engineering because it can lead to information loss and bias in data analysis. Several imputation techniques have been proposed to deal with both numerical and categorical missing data. However, most of those techniques used is simple reuse techniques originally designed for numerical data, which is a problem when the missing data are related to categorical attributes. This paper aims (a) to propose a new fuzzy case‐based reasoning (CBR) imputation technique designed for both numerical and categorical data and (b) to evaluate and compare the performance of the proposed technique with the k‐nearest neighbor (KNN) imputation technique in terms of error and accuracy under different missing data percentages and missingness mechanisms in four software engineering data sets. The results suggest that the proposed fuzzy CBR technique outperformed KNN in terms of imputation error and accuracy regardless of the missing data percentage, missingness mechanism, and data set used. Moreover, we found that the missingness mechanism has an important impact on the performance of both techniques. The results are encouraging in the sense that using an imputation technique designed for both categorical and numerical data is better than reusing methods originally designed for numerical data. 相似文献
992.
Alexandra Brintrup Johnson Pak David Ratiney Tim Pearce Pascal Wichmann Philip Woodall 《国际生产研究杂志》2020,58(11):3330-3341
Although predictive machine learning for supply chain data analytics has recently been reported as a significant area of investigation due to the rising popularity of the AI paradigm in industry, there is a distinct lack of case studies that showcase its application from a practical point of view. In this paper, we discuss the application of data analytics in predicting first tier supply chain disruptions using historical data available to an Original Equipment Manufacturer (OEM). Our methodology includes three phases: First, an exploratory phase is conducted to select and engineer potential features that can act as useful predictors of disruptions. This is followed by the development of a performance metric in alignment with the specific goals of the case study to rate successful methods. Third, an experimental design is created to systematically analyse the success rate of different algorithms, algorithmic parameters, on the selected feature space. Our results indicate that adding engineered features in the data, namely agility, outperforms other experiments leading to the final algorithm that can predict late orders with 80% accuracy. An additional contribution is the novel application of machine learning in predicting supply disruptions. Through the discussion and the development of the case study we hope to shed light on the development and application of data analytics techniques in the analysis of supply chain data. We conclude by highlighting the importance of domain knowledge for successfully engineering features. 相似文献
993.
Vítor M. Gaspar Pedro Lavrador João Borges Mariana B. Oliveira João F. Mano 《Advanced materials (Deerfield Beach, Fla.)》2020,32(6):1903975
Bottom-up tissue engineering is a promising approach for designing modular biomimetic structures that aim to recapitulate the intricate hierarchy and biofunctionality of native human tissues. In recent years, this field has seen exciting progress driven by an increasing knowledge of biological systems and their rational deconstruction into key core components. Relevant advances in the bottom-up assembly of unitary living blocks toward the creation of higher order bioarchitectures based on multicellular-rich structures or multicomponent cell–biomaterial synergies are described. An up-to-date critical overview of long-term existing and rapidly emerging technologies for integrative bottom-up tissue engineering is provided, including discussion of their practical challenges and required advances. It is envisioned that a combination of cell–biomaterial constructs with bioadaptable features and biospecific 3D designs will contribute to the development of more robust and functional humanized tissues for therapies and disease models, as well as tools for fundamental biological studies. 相似文献
994.
Yingjie Zhao Yuchen Qiu Hanfei Gao Jiangang Feng Gaosong Chen Lei Jiang Yuchen Wu 《Advanced materials (Deerfield Beach, Fla.)》2020,32(9):1905298
2D layered metal-halide perovskites combine efficient exciton radiative recombination in crystal interior with long-distance free-carrier conduction at layer edges, which are promising candidates for realizing high-performance photovoltaic, light-emission and photodetection devices. The anisotropic electrical conductivity in layered perovskites imposes an additional requirement of orientational control for enabling favorable charge transport. However, rational fabrication of single-crystalline nanostructures with pure crystallographic orientation is still elusive. Herein, large-scale pure (101)-orientated 2D-perovskite single-crystalline nanowire arrays are realized by combining solvent engineering with the capillary-bridge lithography technique. Ordered nucleation at liquid–air interface and unidirectional growth along the dewetting direction are demonstrated by fluorescence microscopy and grazing-incidence X-ray scattering in discrete capillary bridges. In consideration of crystal interior exhibiting high resistance arising from the serial insulating organic barriers and ultrafast dissociation of excitons to generate long-lived free carriers at layer edges, ultrasensitive photodetectors are demonstrated with average responsivity exceeding 1.1 × 104 A W−1 and detectivity exceeding 9.1 × 1015 Jones. 相似文献
995.
Han Gyeol Lee Lingfei Wang Liang Si Xiaoyue He Daniel G. Porter Jeong Rae Kim Eun Kyo Ko Jinkwon Kim Sung Min Park Bongju Kim Andrew Thye Shen Wee Alessandro Bombardi Zhicheng Zhong Tae Won Noh 《Advanced materials (Deerfield Beach, Fla.)》2020,32(8):1905815
The metal–insulator transition (MIT) in transition-metal-oxide is fertile ground for exploring intriguing physics and potential device applications. Here, an atomic-scale MIT triggered by surface termination conversion in SrRuO3 ultrathin films is reported. Uniform and effective termination engineering at the SrRuO3(001) surface can be realized via a self-limiting water-leaching process. As the surface termination converts from SrO to RuO2, a highly insulating and nonferromagnetic phase emerges within the topmost SrRuO3 monolayer. Such a spatially confined MIT is corroborated by systematic characterizations on electrical transport, magnetism, and scanning tunneling spectroscopy. Density functional theory calculations and X-ray linear dichroism further suggest that the surface termination conversion breaks the local octahedral symmetry of the crystal field. The resultant modulation in 4d orbital occupancy stabilizes a nonferromagnetic insulating surface state. This work introduces a new paradigm to stimulate and tune exotic functionalities of oxide heterostructures with atomic precision. 相似文献
996.
Pengyang Wang Renjie Li Bingbing Chen Fuhua Hou Jie Zhang Ying Zhao Xiaodan Zhang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(6):1905766
An electron-transport layer (ETL) with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). However, interfacial energy level mismatch limits the electrical performance of PSCs, particularly the open-circuit voltage (VOC). Herein, a simple low-temperature-processed In2O3/SnO2 bilayer ETL is developed and used for fabricating a new PSC device. The presence of In2O3 results in uniform, compact, and low-trap-density perovskite films. Moreover, the conduction band of In2O3 is shallower than that of Sn-doped In2O3 (ITO), enhancing the charge transfer from perovskite to ETL, thus minimizing VOC loss at the perovskite and ETL interface. A planar PSC with a power conversion efficiency of 23.24% (certified efficiency of 22.54%) is obtained. A high VOC of 1.17 V is achieved with the potential loss at only 0.36 V. In contrast, devices based on single SnO2 layers achieve 21.42% efficiency with a VOC of 1.13 V. In addition, the new device maintains 97.5% initial efficiency after 80 d in N2 without encapsulation and retains 91% of its initial efficiency after 180 h under 1 sun continuous illumination. The results demonstrate and pave the way for the development of efficient photovoltaic devices. 相似文献
997.
Ana Rita Sousa Cláudia Martins-Cruz Mariana B. Oliveira João F. Mano 《Advanced materials (Deerfield Beach, Fla.)》2020,32(2):1906305
Cellular aggregates are used as relevant regenerative building blocks, tissue models, and cell delivery platforms. Biomaterial-free structures are often assembled either as 2D cell sheets or spherical microaggregates, both incompatible with free-form deposition, and dependent on challenging processes for macroscale 3D upscaling. The continuous and elongated nature of fiber-shaped materials enables their deposition in unrestricted multiple directions. Cellular fiber fabrication has often required exogenously provided support proteins and/or the use of biomaterial-based sacrificial templates. Here, the rapid (<24 h) assembly of fiberoids is reported: living centimeter-long scaffold-free fibers of cells produced in the absence of exogenous materials or supplements. Adipose-derived mesenchymal stem cell fiberoids can be easily modulated into complex multidimensional geometries and show tissue-invasive properties while keeping the secretion of trophic factors. Proangiogenic properties studied on a chick chorioallantoic membrane in an ovo model are observed for heterotypic fiberoids containing endothelial cells. These micro-to-macrotissues may find application as morphogenic therapeutic and tissue-mimetic building blocks, with the ability to integrate 3D and 4D full biological materials. 相似文献
998.
999.
Functionalized carbon nanomaterials, as significant options for renewable energy systems, are widely utilized in diversified electrochemical reactions in virtue of property advantages. The inevitable defect sites in architectures greatly affect physicochemical properties of carbon nanomaterials, thus defect engineering has recently become a vital research orientation of carbon‐based electrocatalysts. The intentionally introduced intrinsic carbon defect sites in the frameworks can directly serve as the potential active sites owing to the altered surface charge state, modulated adsorption free energy of key intermediates, as well as diminished bandgap. Furthermore, the synergistic sites between intrinsic defects and heteroatom dopants/captured atomic metal species can further optimize the electronic structure and adsorption/desorption behavior, making carbon‐based catalysts comparable to commercial precious metal catalysts in electrocatalysis. With pressing research demands, the common configurations, construction strategies, structure–activity relationships, and characterization methods for intrinsic carbon defect‐involved catalytic centers are systematically summarized. Such theoretical and experimental evidences of intrinsic defect‐induced activity can reveal the active centers and relevant catalytic mechanism, thereby providing necessary guidance for the design and construction of highly efficient carbon‐based electrocatalysts and promoting their commercial applications. 相似文献
1000.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献