全文获取类型
收费全文 | 3742篇 |
免费 | 250篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 56篇 |
综合类 | 3篇 |
化学工业 | 1177篇 |
金属工艺 | 53篇 |
机械仪表 | 91篇 |
建筑科学 | 133篇 |
矿业工程 | 3篇 |
能源动力 | 121篇 |
轻工业 | 418篇 |
水利工程 | 18篇 |
无线电 | 338篇 |
一般工业技术 | 668篇 |
冶金工业 | 197篇 |
原子能技术 | 49篇 |
自动化技术 | 670篇 |
出版年
2024年 | 8篇 |
2023年 | 44篇 |
2022年 | 248篇 |
2021年 | 279篇 |
2020年 | 118篇 |
2019年 | 103篇 |
2018年 | 131篇 |
2017年 | 130篇 |
2016年 | 164篇 |
2015年 | 144篇 |
2014年 | 153篇 |
2013年 | 242篇 |
2012年 | 233篇 |
2011年 | 282篇 |
2010年 | 199篇 |
2009年 | 202篇 |
2008年 | 176篇 |
2007年 | 155篇 |
2006年 | 151篇 |
2005年 | 104篇 |
2004年 | 91篇 |
2003年 | 72篇 |
2002年 | 59篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 44篇 |
1998年 | 73篇 |
1997年 | 49篇 |
1996年 | 48篇 |
1995年 | 18篇 |
1994年 | 30篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 19篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1973年 | 2篇 |
排序方式: 共有3995条查询结果,搜索用时 15 毫秒
231.
We introduce a new approach for finding overlapping clusters given pairwise similarities of objects. In particular, we relax the problem of correlation clustering by allowing an object to be assigned to more than one cluster. At the core of our approach is an optimization problem in which each data point is mapped to a small set of labels, representing membership in different clusters. The objective is to find a mapping so that the given similarities between objects agree as much as possible with similarities taken over their label sets. The number of labels can vary across objects. To define a similarity between label sets, we consider two measures: (i) a 0–1 function indicating whether the two label sets have non-zero intersection and (ii) the Jaccard coefficient between the two label sets. The algorithm we propose is an iterative local-search method. The definitions of label set similarity give rise to two non-trivial optimization problems, which, for the measures of set-intersection and Jaccard, we solve using a greedy strategy and non-negative least squares, respectively. We also develop a distributed version of our algorithm based on the BSP model and implement it using a Pregel framework. Our algorithm uses as input pairwise similarities of objects and can thus be applied when clustering structured objects for which feature vectors are not available. As a proof of concept, we apply our algorithms on three different and complex application domains: trajectories, amino-acid sequences, and textual documents. 相似文献
232.
Minh Q. Phan Francesco Vicario Richard W. Longman Raimondo Betti 《International journal of control》2013,86(8):1504-1522
This paper formulates optimal bilinear observers for bilinear state-space models. Observers in bilinear form, as opposed to other nonlinear forms, are required to develop an extension of observer/Kalman filter identification for simultaneous identification of a bilinear state-space model and an associated bilinear observer from noisy input–output measurements. The paper establishes the relationship between the bilinear observer gains and the interaction matrices which are used to convert the original bilinear state-space model to a form that simplifies the identification of such a model. Techniques to find the interaction matrices are developed. In the absence of noises, these matrices produce the gains of the fastest converging observer. In the presence of noises, they minimise the state estimation error in the same manner as a standard steady-state Kalman filter. Numerical examples illustrate both the theoretical and computational aspects of the proposed algorithms. 相似文献
233.
Francesco Bellotti Riccardo Berta Alessandro De Gloria Massimiliano Margarone 《Personal and Ubiquitous Computing》2002,6(3):155-163
Future generation cars will be characterized by a wide range of Information Technology (IT) services providing safety and
infotainment. This makes the car an information intensive environment where the visual channel is overloaded, putting the
safety of drivers and passengers in jeopardy. We propose the use of a 3D auditory display to provide information from the
Advanced Driver Assistance Systems. This reduces the eye-off-road time, exploiting the human capability to associate sounds
with positions in space. Preliminary lab tests reveal the suitability of this approach. The system still has to be carefully
tuned and personalized to achieve usability and reliability, but we think that it provides a complementary channel that is
specially useful in low visibility conditions. 相似文献
234.
Laurà R Magnoli D Zichichi R Guerrera MC De Carlos F Suárez AÁ Abbate F Ciriaco E Vega JA Germanà A 《Microscopy research and technique》2012,75(3):359-366
The zebrafish pineal gland plays a fundamental role in the regulation of the circadian rhythm through the melatonin secretion. The pinealocytes, also called photoreceptive cells, are considered the morphofunctional unit of pineal gland. In literature, the anatomical features, the cellular characteristics, and the pinealocytes morphology of zebrafish pineal gland have not been previously described in detail. Therefore, this study was undertaken to analyze the structure and ultrastructure, as well as the immunohistochemical profile of the zebrafish pineal gland with particular reference to the pinealocytes. Here, we demonstrated, using RT-PCR, immunohistochemistry and transmission electron microscopy, the expression of the mRNA for rhodopsin in the pineal gland of zebrafish, as well as its cellular localization exclusively in the pinealocytes of adult zebrafish. Moreover, the ultrastructural observations demonstrated that the pinealocytes were constituted by an outer segment with numerous lamellar membranes, an inner segment with many mitochondria, and a basal pole with the synapses. Our results taken together demonstrated a central role of zebrafish pinealocytes in the control of pineal gland functions. 相似文献
235.
Morena Petrini Tania Vanessa Pierfelice Emira DAmico Natalia Di Pietro Assunta Pandolfi Camillo DArcangelo Francesco De Angelis Domitilla Mandatori Valeria Schiavone Adriano Piattelli Giovanna Iezzi 《International journal of molecular sciences》2021,22(18)
Current research on dental implants has mainly focused on the influence of surface roughness on the rate of osseointegration, while studies on the development of surfaces to also improve the interaction of peri-implant soft tissues are lacking. To this end, the first purpose of this study was to evaluate the response of human gingival fibroblasts (hGDFs) to titanium implant discs (Implacil De Bortoli, Brazil) having different micro and nano-topography: machined (Ti-M) versus sandblasted/double-etched (Ti-S). The secondary aim was to investigate the effect of the macrogeometry of the discs on cells: linear-like (Ti-L) versus wave-like (Ti-W) surfaces. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis showed that the Ti-S surfaces were characterized by a significantly higher micro and nano roughness and showed the 3D macrotopography of Ti-L and Ti-W surfaces. For in vitro analyses, the hGDFs were seeded into titanium discs and analyzed at 1, 3, and 5 days for adhesion and morphology (SEM) viability and proliferation (Cck-8 and MTT assays). The results showed that all tested surfaces were not cytotoxic for the hGDFs, rather the nano-micro and macro topography favored their proliferation in a time-dependent manner. Especially, at 3 and 5 days, the number of cells on Ti-L was higher than on other surfaces, including Ti-W surfaces. In conclusion, although further studies are needed, our in vitro data proved that the use of implant discs with Ti-S surfaces promotes the adhesion and proliferation of gingival fibroblasts, suggesting their use for in vivo applications. 相似文献
236.
Johanna Lieb Valeria Demontis Domenic Prete Daniele Ercolani Valentina Zannier Lucia Sorba Shimpei Ono Fabio Beltram Benjamin Sacp Francesco Rossella 《Advanced functional materials》2019,29(3)
Here, the operation of a field‐effect transistor based on a single InAs nanowire gated by an ionic liquid is reported. Liquid gating yields very efficient carrier modulation with a transconductance value 30 times larger than standard back gating with the SiO2/Si++ substrate. Thanks to this wide modulation, the controlled evolution from semiconductor to metallic‐like behavior in the nanowire is shown. This work provides the first systematic study of ionic‐liquid gating in electronic devices based on individual III–V semiconductor nanowires: this architecture opens the way to a wide range of fundamental and applied studies from the phase transitions to bioelectronics. 相似文献
237.
We investigate the use of mixed self-assembled monolayers (SAMs) for creating nanoscale striped patterns on nanowires and nanorods. Our simulations predict that SAMs comprised of an equal composition of length-mismatched, thermodynamically incompatible surfactants adsorbed on nanowire surfaces self-organize into equilibrium stripes of alternating composition always perpendicular, rather than parallel, to the nanowire axis. We support the simulation results with preliminary experimental investigations of gold nanorods coated with binary mixtures of ligand molecules, which show stripes roughly perpendicular to the rod axis in all cases. 相似文献
238.
239.
Wonsuk Chung Francesco Lemmi Patrick M. Smith Teruo Sasagawa 《Journal of the Society for Information Display》2005,13(7):555-561
Abstract— A complete poly‐Si thin‐film transistor (TFT) on plastic process has been optimized to produce TFT arrays for active‐matrix displays. We present a detailed study of the poly‐Si crystallization process, a mechanism for protecting the plastic substrate from the pulsed laser used to crystallize the silicon, and a high‐performance low‐temperature gate dielectric film. Poly‐Si grain sizes and the corresponding TFT performance have been measured for a range of excimer‐laser crystallization fluences near the full‐melt threshold, allowing optimization of the laser‐crystallization process. A Bragg reflector stack has been embedded in the plastic coating layers; its effectiveness in protecting the plastic from the excimer‐laser pulse is described. Finally, we describe a plasma pre‐oxidation step, which has been added to a low‐temperature (<100°C) gate dielectric film deposition process to dramatically improve the electrical properties of the gate dielectric. These processes have been integrated into a complete poly‐Si TFT on plastic fabrication process, which produces PMOS TFTs with mobilities of 66 cm2 /V‐sec, threshold voltages of ?3.5 V, and off currents of approximately 1 pA per micron of gate width. 相似文献
240.
Carlo Bertucci Piero Salvadori Francesco Ciardelli Graziella Fatti 《Polymer Bulletin》1985,13(5):469-472
Summary Circular dichroism of isotactic samples of poly-(S)-4-methyl-1-hexene and poly-(R)-3,7-dimethyl-1-octene, have been measured in the vacuum ultraviolet spectral region (200-140 nm). The c.d. band at about 160. nm accounts for the optical activity in the visible region and reflects the presence of one screw sense helical conformation of the sample examined.The authors thank Prof. W.C. Johnson, Jr., Department of Biochemistry and Biophysics, Oregon State University, for allowing them to use the vacuum u.v. spectrometer. This work has been partially supported by a N.A.T.O. grant, and by Ministero Pubblica Istruzione (MPI), Roma — Italy. 相似文献