全文获取类型
收费全文 | 3404篇 |
免费 | 153篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 3558篇 |
出版年
2023年 | 23篇 |
2022年 | 25篇 |
2021年 | 59篇 |
2020年 | 52篇 |
2019年 | 65篇 |
2018年 | 80篇 |
2017年 | 48篇 |
2016年 | 62篇 |
2015年 | 65篇 |
2014年 | 107篇 |
2013年 | 172篇 |
2012年 | 151篇 |
2011年 | 178篇 |
2010年 | 133篇 |
2009年 | 131篇 |
2008年 | 159篇 |
2007年 | 129篇 |
2006年 | 125篇 |
2005年 | 106篇 |
2004年 | 68篇 |
2003年 | 84篇 |
2002年 | 78篇 |
2001年 | 70篇 |
2000年 | 59篇 |
1999年 | 54篇 |
1998年 | 200篇 |
1997年 | 154篇 |
1996年 | 106篇 |
1995年 | 68篇 |
1994年 | 75篇 |
1993年 | 53篇 |
1992年 | 32篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 34篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 30篇 |
1982年 | 17篇 |
1981年 | 31篇 |
1980年 | 18篇 |
1979年 | 29篇 |
1978年 | 24篇 |
1977年 | 34篇 |
1976年 | 58篇 |
1975年 | 26篇 |
1973年 | 16篇 |
排序方式: 共有3558条查询结果,搜索用时 15 毫秒
991.
Atomic Interface Engineering and Electric‐Field Effect in Ultrathin Bi2MoO6 Nanosheets for Superior Lithium Ion Storage 下载免费PDF全文
Yang Zheng Tengfei Zhou Xudong Zhao Wei Kong Pang Hong Gao Sean Li Zhen Zhou Huakun Liu Zaiping Guo 《Advanced materials (Deerfield Beach, Fla.)》2017,29(26)
Ultrathin 2D materials can offer promising opportunities for exploring advanced energy storage systems, with satisfactory electrochemical performance. Engineering atomic interfaces by stacking 2D crystals holds huge potential for tuning material properties at the atomic level, owing to the strong layer–layer interactions, enabling unprecedented physical properties. In this work, atomically thin Bi2MoO6 sheets are acquired that exhibit remarkable high‐rate cycling performance in Li‐ion batteries, which can be ascribed to the interlayer coupling effect, as well as the 2D configuration and intrinsic structural stability. The unbalanced charge distribution occurs within the crystal and induces built‐in electric fields, significantly boosting lithium ion transfer dynamics, while the extra charge transport channels generated on the open surfaces further promote charge transport. The in situ synchrotron X‐ray powder diffraction results confirm the material's excellent structural stability. This work provides some insights for designing high‐performance electrode materials for energy storage by manipulating the interface interaction and electronic structure. 相似文献
992.
Sean E. Doris Adrien Pierre Robert A. Street 《Advanced materials (Deerfield Beach, Fla.)》2018,30(15)
In recent years, organic electrochemical transistors (OECTs) have found applications in chemical and biological sensing and interfacing, neuromorphic computing, digital logic, and printed electronics. However, the incorporation of OECTs in practical electronic circuits is limited by the relative lack of control over their threshold voltage, which is important for controlling the power consumption and noise margin in complementary and unipolar circuits. Here, the threshold voltage of OECTs is precisely tuned over a range of more than 1 V by chemically controlling the electrochemical potential at the gate electrode. This threshold voltage tunability is exploited to prepare inverters and amplifiers with improved noise margin and gain, respectively. By coupling the gate electrode with an electrochemical oscillator, single‐transistor oscillators based on OECTs with dynamic time‐varying threshold voltages are prepared. This work highlights the importance of electrochemistry at the gate electrode in determining the electrical properties of OECTs, and opens a path toward the system‐level design of low‐power OECT‐based electronics. 相似文献
993.
Property owners are facing increasing threats from flooding and in response are likely to turn to products designed to waterproof or ‘seal’ the outside of the building in an effort to prevent the ingress of flood water. However, very limited research has been conducted on the effect of this sealing action and the consequent hydraulic load acting upon the structure of the building. The theoretical safe application of waterproofing products has been suggested to be between 0.6 and 1 m (published guidance suggests 0.9 m), although the experimental evidence supporting these suggestions is either absent or limited in nature. This paper presents the findings of an experimental programme that has examined the effect of out-of-plane hydrostatic loading on masonry walls typical of domestic or commercial buildings. The study, conducted at 1/6th scale using a geotechnical centrifuge considers wall panels constructed from a variety of masonry units (autoclaved aerated concrete block, brick and brick-block) bound together with two different types of mortar. The wall panels were subject to an axial load representative of 1 storey of loading and were simply supported on all 4 sides. The load—out-of-plane deflection response of the panels was captured by a 3D digital image correlation system, and the water level at failure was compared to that predicted from previous research and the established yield line analysis method with encouraging results. When partial material and load factors were taken into consideration the results illustrated that a safe sealing height of 0.9 m, as quoted in the literature, would generally be inappropriate, whilst the safe sealing height of 0.6 m was not suitable for every case investigated. This supports the need for a suitable approach for the calculation of water levels at failure rather than the use of fixed values given in published literature. 相似文献
994.
Robin A. James Andrew J. Stapleton Adam Hughes Eric Charrault Kamil Zuber Eliza Switalska Drew Evans Peter Murphy Marta Llusca 《Advanced Engineering Materials》2018,20(7)
995.
JM Menter TD Hollins RM Sayre AA Etemadi I Willis SN Hughes 《Canadian Metallurgical Quarterly》1998,14(5-6):154-159
"Special" highly protective fabrics are now available that offer broad-spectrum protection in preventing sunburn, and possibly other types of photodamage. It is important to know to what extent these fabrics are capable of protecting the wearer against skin cancer, photosensitivity disorders, and inadvertent phototoxic reactions from photodynamic therapy (PDT). We assess the ability of one such special (Solumbra) fabric and one "typical" summer fabric to provide protection against PDT phototoxicity produced in tape-stripped Sk-1 hairless mice by topical 5-aminolevulinic acid (ALA) and (primarily) visible light (360-800 nm). Since ALA-derived photosensitizers absorb most of the visible spectrum, results from these studies give a good indication of the photoprotective capability of these fabrics throughout this region. Mice were irradiated dorsally with a Kodak slide projector equipped with a 300 W tungsten-halogen lamp (I0 = 48.3 mW/cm2). After determining the minimal phototoxic dose (MPD) to be 1.40 +/- 0.4 J/cm2, we irradiated the tape-stripped ALA-sensitized mice through the stretched test fabrics with appropriate multiples of the MPD. The special fabric provided protection against 25-30 MPD visible light between 360-800 nm in 14/14 mice. The typical fabric failed to provide protection against 2.5 MPD of the same spectrum. No phototoxic or other adverse responses were seen with either the ALA or light control. In conclusion, the Solumbra fabric is much more protective against ALA photosensitization than the typical fabric. Both appear better at blocking UV than visible light. 相似文献
996.
Rotation distance between trees measures the number of simple operations it takes to transform one tree into another. There are no known polynomial-time algorithms for computing rotation distance. In the case of ordered rooted trees, we show that the rotation distance between two ordered trees is fixed-parameter tractable, in the parameter, k, the rotation distance. The proof relies on the kernelization of the initial trees to trees with size bounded by 5k. 相似文献
997.
Modeling and characterization of an industrial inkjet head for micro-patterning on printed circuit boards 总被引:1,自引:0,他引:1
Changsung Sean Kim Sung-Jun Park Wonchul Sim Young-Jae Kim Youngseuck Yoo 《Computers & Fluids》2009,38(3):602-612
A conceptual design using computational fluid dynamics (CFD) and micro-electro-mechanical systems (MEMS) fabrication has been performed to develop an industrial inkjet head for micro-patterning on printed circuit boards. The printhead has been fabricated with silicon and silicon on insulator (SOI) wafers by MEMS process and silicon to silicon bonding method. The measured displacement waveform from a piezoelectric actuator by laser doppler vibrometer (LDV) was used as input data for the three-dimensional flow solver to simulate the droplet formation. The mechanism of droplet ejection from piezoelectric-type inkjet heads was investigated by simulating two-phase flows of the air and metal inks. As a preliminary approach, liquid metal jetting phenomena are identified by simulating droplet ejection and droplet formation in a consequent manner. Parametric studies are followed by the design optimization process to deduce key factors to inkjet head performance: nozzle geometry, droplet size, ejecting speed, pulse amplitude, and ink viscosity. The present design tool, based on a two-phase flow solver and experimental measurements, has shown its promising applicability to various concept designs of industrial inkjet system for micro-patterning on electronic chips and boards. 相似文献
998.
Sean Gallagher Susan Kotowski Kermit G. Davis Christopher Mark Craig S. Compton Ronald L. Huston John Connelly 《International Journal of Industrial Ergonomics》2009,39(5):828-834
Bolting large sheets of wire mesh screen (WMS) to the roof of underground mines prevents injuries due to rock falls. However, WMS can be heavy and awkward to lift and transport, and may result in significant spinal loading. Accordingly, six male subjects (mean age = 45.8 years + 7.5 SD) were recruited to lift WMS in a laboratory investigation of the biomechanical demands. Biomechanical modeling was used to estimate external moments about L5–S1 for sixteen lifting tasks, using two sizes of WMS. Full-size WMS involved a two-person lift, while half-size WMS involved a one-person lift. Lifts were performed under 168 cm and 213 cm vertical space. Restriction in vertical space increased the maximum L5–S1 extensor moment from 254 to 274 Nm and right lateral bending moment from 195 to 251 Nm. Lifting full sheets of screen (as opposed to half sheets) resulted in an average 33 Nm increase in L5–S1 extensor moment. The L5–S1 extensor moment was increased by an average of 44 Nm (18%) when lifting screens positioned flat on the floor compared to an upright position.
Relevance to industry
Large flexible materials are commonly lifted in industrial work environments, and may involve the efforts of two or more workers. The current study examines the low back loading associated with lifting large flexible screens and presents recommendations to reduce spine loading. 相似文献999.
Kinsinger CR Apffel J Baker M Bian X Borchers CH Bradshaw R Brusniak MY Chan DW Deutsch EW Domon B Gorman J Grimm R Hancock W Hermjakob H Horn D Hunter C Kolar P Kraus HJ Langen H Linding R Moritz RL Omenn GS Orlando R Pandey A Ping P Rahbar A Rivers R Seymour SL Simpson RJ Slotta D Smith RD Stein SE Tabb DL Tagle D Yates JR Rodriguez H 《Proteomics. Clinical applications》2011,5(11-12):580-589
Policies supporting the rapid and open sharing of proteomic data are being implemented by the leading journals in the field. The proteomics community is taking steps to ensure that data are made publicly accessible and are of high quality, a challenging task that requires the development and deployment of methods for measuring and documenting data quality metrics. On September 18, 2010, the U.S. National Cancer Institute (NCI) convened the "International Workshop on Proteomic Data Quality Metrics" in Sydney, Australia, to identify and address issues facing the development and use of such methods for open access proteomics data. The stakeholders at the workshop enumerated the key principles underlying a framework for data quality assessment in mass spectrometry data that will meet the needs of the research community, journals, funding agencies, and data repositories. Attendees discussed and agreed up on two primary needs for the wide use of quality metrics: (i) an evolving list of comprehensive quality metrics and (ii) standards accompanied by software analytics. Attendees stressed the importance of increased education and training programs to promote reliable protocols in proteomics. This workshop report explores the historic precedents, key discussions, and necessary next steps to enhance the quality of open access data. By agreement, this article is published simultaneously in Proteomics, Proteomics Clinical Applications, Journal of Proteome Research, and Molecular and Cellular Proteomics, as a public service to the research community. The peer review process was a coordinated effort conducted by a panel of referees selected by the journals. 相似文献
1000.
Yongjie Zhang Thomas J.R. Hughes Chandrajit L. Bajaj 《Computer Methods in Applied Mechanics and Engineering》2010,199(5-8):405-415
This paper describes an automatic and efficient approach to construct unstructured tetrahedral and hexahedral meshes for a composite domain made up of heterogeneous materials. The boundaries of these material regions form non-manifold surfaces. In earlier papers, we developed an octree-based isocontouring method to construct unstructured 3D meshes for a single material (homogeneous) domain with manifold boundary. In this paper, we introduce the notion of a material change edge and use it to identify the interface between two or several different materials. A novel method to calculate the minimizer point for a cell shared by more than two materials is provided, which forms a non-manifold node on the boundary. We then mesh all the material regions simultaneously and automatically while conforming to their boundaries directly from volumetric data. Both material change edges and interior edges are analyzed to construct tetrahedral meshes, and interior grid points are analyzed for proper hexahedral mesh construction. Finally, edge-contraction and smoothing methods are used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimization techniques is used for hexahedral mesh quality improvement. The shrink set of pillowing schemes is defined automatically as the boundary of each material region. Several application results of our multi-material mesh generation method are also provided. 相似文献