全文获取类型
收费全文 | 7677篇 |
免费 | 236篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 83篇 |
综合类 | 6篇 |
化学工业 | 1407篇 |
金属工艺 | 88篇 |
机械仪表 | 181篇 |
建筑科学 | 292篇 |
矿业工程 | 49篇 |
能源动力 | 170篇 |
轻工业 | 590篇 |
水利工程 | 98篇 |
石油天然气 | 28篇 |
无线电 | 484篇 |
一般工业技术 | 1244篇 |
冶金工业 | 1927篇 |
原子能技术 | 55篇 |
自动化技术 | 1227篇 |
出版年
2023年 | 47篇 |
2022年 | 78篇 |
2021年 | 112篇 |
2020年 | 86篇 |
2019年 | 101篇 |
2018年 | 149篇 |
2017年 | 128篇 |
2016年 | 128篇 |
2015年 | 133篇 |
2014年 | 192篇 |
2013年 | 440篇 |
2012年 | 354篇 |
2011年 | 446篇 |
2010年 | 303篇 |
2009年 | 280篇 |
2008年 | 396篇 |
2007年 | 397篇 |
2006年 | 331篇 |
2005年 | 310篇 |
2004年 | 271篇 |
2003年 | 230篇 |
2002年 | 234篇 |
2001年 | 162篇 |
2000年 | 137篇 |
1999年 | 158篇 |
1998年 | 189篇 |
1997年 | 173篇 |
1996年 | 157篇 |
1995年 | 146篇 |
1994年 | 148篇 |
1993年 | 122篇 |
1992年 | 126篇 |
1991年 | 64篇 |
1990年 | 111篇 |
1989年 | 86篇 |
1988年 | 79篇 |
1987年 | 98篇 |
1986年 | 62篇 |
1985年 | 78篇 |
1984年 | 69篇 |
1983年 | 78篇 |
1982年 | 70篇 |
1981年 | 56篇 |
1980年 | 54篇 |
1979年 | 54篇 |
1978年 | 42篇 |
1977年 | 53篇 |
1976年 | 44篇 |
1975年 | 42篇 |
1973年 | 27篇 |
排序方式: 共有7929条查询结果,搜索用时 0 毫秒
91.
Prutha Joshi Steven Breaux Joseph Naro Yuyang Wang Md Shakir Uddin Ahmed Komal Vig Maria L. Auad 《应用聚合物科学杂志》2021,138(21):50489
Hydrogels are polymeric materials widely used in medicine due to their similarity with the biological components of the body. Hydrogels are biocompatible materials that have the potential to promote cell proliferation and tissue support because of their hydrophilic nature, porous structure, and elastic mechanical properties. In this work, we demonstrate the microwave-assisted synthesis of three molecular weight varieties of poly(ethylene glycol) dimethacrylate (PEGDMA) with different mechanical and thermal properties and the rapid photo of them using 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) as UV photoinitiator. The effects of the poly(ethylene glycol) molecular weight and degree of acrylation on swelling, mechanical, and rheological properties of hydrogels were investigated. The biodegradability of the PEGDMA hydrogels, as well as the ability to grow and proliferate cells, was examined for its viability as a scaffold in tissue engineering. Altogether, the biomaterial hydrogel properties open the way for applications in the field of regenerative medicine for functional scaffolds and tissues. 相似文献
92.
Fatoumata Ide Seyni Lawrence Barrett Steven Crossley Brian P. Grady 《Polymer Engineering and Science》2021,61(4):1186-1194
An asymmetric double cantilever beam test was used to determine the ability of carbon nanotubes with varying chemistry along their lengths, that is, diblock nanotubes, to compatibilize the polystyrene/poly(methyl methacrylate) (PS/PMMA) interface. PS molecules were grafted primarily to one of the blocks to cause that block to migrate to the PS phase since otherwise both blocks would prefer to reside in PMMA. Fracture toughnesses increased monotonically with increasing diblock carbon nanotube concentration and maximum values were like those for block copolymer-reinforced interfaces while single-chemistry nanotubes showed no reinforcing effect. However, the abrupt increase in fracture toughness with added compatibilizer indicative of a transition to crazing was not found consistent with nanotubes suppressing crazing in homopolymers. Scanning electron microscopy images of the fractured surfaces show agglomerates of carbon nanotubes present which are likely limiting the efficacy of carbon nanotubes at toughening the interface. 相似文献
93.
94.
95.
Steven R. Burdette 《Journal of the Society for Information Display》2015,23(3):107-112
A method based on inverting a finite element model is presented for determining film stress from pitch changes before and after a film deposition step in liquid‐crystal display panel manufacturing. It differs from the conventional methods by making use of in‐plane deformation rather than out‐of‐plane measurements to calculate film stress. The resulting film stress is confounded with glass structural relaxation. Measurements of out‐of‐plane deformation at the edge of the sheet can be used with the pitch measurements to separate the effects of glass structural relaxation and film stress. 相似文献
96.
97.
This paper describes an approach to using evolutionary algorithms for reasoning about paths through network data. The paths investigated in the context of this research are functional paths wherein the characteristics (e.g., path length, morphology, location) of the path are integral to the objective purpose of the path. Using two datasets of combined surface and road networks, the research demonstrates how an evolutionary algorithm can be used to reason about functional paths. We present the algorithm approach, the parameters and fitness function that drive the functional aspects of the path, and an approach for using the algorithm to respond to dynamic changes in the search space. The results of the search process are presented in terms of the overall success based on the response of the search to variations in the environment and through the use of an occupancy grid characterizing the overall search process. The approach offers a great deal of flexibility over more conventional heuristic path finding approaches and offers additional perspective on dynamic network analysis. 相似文献
98.
This paper outlines the major motivating factors concerning a novel collaborative project between Edinburgh College of Art and Edinburgh Virtual Environment Centre. The Tacitus project will investigate the use of multi-modal virtual environments, specifically, the haptic (touch) modality, with regards to the creative processes employed by designers working within the field of applied arts. The salient areas of research are described, and the methods by which information regarding these areas will be obtained are considered. Initial investigations have revealed a strong need to mimic the traditional applied artists' workspaces, with co-location of visual and haptic cues a priority. 相似文献
99.
In many physical systems, when implementing quantum gate operations unavoidable global and relative phases occur as by-products due to the internal structure of the governing Hamiltonian. To correct, additional phase rotation gates are used, which increases the computational overhead. Here, we show how these phase by-products can actually be used to our advantage by using them to implement universal quantum computing between qubits not directly coupled to each other. The gate operations, CNOT, Toffoli, and swap gates, require much less computational overhead than present schemes, and are achieved with fidelity greater than 99%. We then present a linear nearest-neighbor architecture that takes full advantage of the phase by-products, and we show how to implement gates from a universal set efficiently in this layout. In this scheme gate operations are realized by only varying a single control parameter per data qubit, and the ability to tune couplings is not required. 相似文献
100.
Sirpa Thessler Steven Sesnie Zayra S. Ramos Bendaa Kalle Ruokolainen Erkki Tomppo Bryan Finegan 《Remote sensing of environment》2008,112(5):2485-2494
Conservation and land use planning in humid tropical lowland forests urgently need accurate remote sensing techniques to distinguish among floristically different forest types. We investigated the degree to which floristically and structurally defined Costa Rican lowland rain forest types can be accurately discriminated by a non-parametric k nearest neighbors (k-nn) classifier or linear discriminant analysis. Pixel values of Landsat Thematic Mapper (TM) image and Shuttle Radar Topography Mission (SRTM) elevation model extracted from segments or from 5 × 5 pixel windows were employed in the classifications. 104 field plots were classified into three floristic and one structural type of forest (regrowth forest). Three floristically defined forest types were formed through clustering the old-growth forest plots (n = 52) by their species specific importance values. An error assessment of the image classification was conducted via cross-validation and error matrices, and overall percent accuracy and Kappa scores were used as measures of accuracy. Image classification of the four forest types did not adequately distinguish two old-growth forest classes, so they were merged into a single forest class. The resulting three forest classes were most accurately classified by the k-nn classifier using segmented image data (overall accuracy 91%). The second best method, with respect to accuracy, was the k-nn with 5 × 5 pixel windows data (89% accuracy), followed by the canonical discriminant analysis using the 5 × 5 pixel window data (86%) and the segment data (82%). We conclude the k-nn classifier can accurately distinguish floristically and structurally different rain forest types. The classification accuracies were higher for the k-nn classifier than for the canonical discriminant analysis, but the differences in Kappa scores were not statistically significant. The segmentation did not increase classification accuracy in this study. 相似文献