全文获取类型
收费全文 | 3717篇 |
免费 | 19篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 90篇 |
金属工艺 | 8篇 |
机械仪表 | 13篇 |
建筑科学 | 25篇 |
矿业工程 | 3篇 |
能源动力 | 14篇 |
轻工业 | 103篇 |
水利工程 | 3篇 |
无线电 | 56篇 |
一般工业技术 | 90篇 |
冶金工业 | 3273篇 |
原子能技术 | 6篇 |
自动化技术 | 44篇 |
出版年
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 35篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 25篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 20篇 |
2002年 | 10篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 118篇 |
1998年 | 1014篇 |
1997年 | 580篇 |
1996年 | 355篇 |
1995年 | 229篇 |
1994年 | 175篇 |
1993年 | 191篇 |
1992年 | 25篇 |
1991年 | 52篇 |
1990年 | 45篇 |
1989年 | 52篇 |
1988年 | 60篇 |
1987年 | 57篇 |
1986年 | 41篇 |
1985年 | 29篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 21篇 |
1980年 | 33篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 79篇 |
1976年 | 163篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1968年 | 4篇 |
1967年 | 5篇 |
排序方式: 共有3737条查询结果,搜索用时 15 毫秒
1.
2.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
3.
Cardenas LM Cuttle SP Crabtree B Hopkins A Shepherd A Scholefield D del Prado A 《The Science of the total environment》2011,409(6):1104-1115
As much as 60% of the nitrate in water in England is thought to derive from agriculture. Legislation aims to improve water quality by limiting nitrate concentration in surface and groundwaters to 50 mg l−1. The UK Government responded to the requirements of the EC Nitrate Directive by delineating Nitrate Vulnerable Zones (NVZs) to cover 55% of England in 2002 and increased it to 70% in 2009. In this study we assessed the cost-effectiveness of measures for implementation in livestock systems to mitigate nitrate leaching in the UK. These estimates were prepared for a range of hypothetical farms representative of typical dairy, beef and sheep farms at different locations in England and Wales and for a list of mitigation measures identified to reduce leaching. The NGAUGE and NFixCycle models were used to estimate leaching from these systems. The costs of implementation of the mitigation measures were also assessed in order to evaluate the cost-effectiveness of these measures. In general, the most effective measures to reduce leaching for all systems were the ones that involved a reduction in stocking rates and grazing time, followed by those involving improvements in fertiliser and crop management. Only in the case of the dairy system was effectiveness affected by location of the farm. The costs for implementation in the sheep system were relatively low compared with beef and dairy systems. Implementation of some of the measures with high cost-effectiveness would need to be incentivised financially or with legislation due to the high costs involved. 相似文献
4.
Faecal indicator organism concentrations and catchment export coefficients in the UK 总被引:2,自引:0,他引:2
Kay D Crowther J Stapleton CM Wyer MD Fewtrell L Anthony S Bradford M Edwards A Francis CA Hopkins M Kay C McDonald AT Watkins J Wilkinson J 《Water research》2008,42(10-11):2649-2661
Characterisation of faecal indicator organism (FIO) concentrations and export coefficients for catchments with particular combinations of land use and under specific climatic regimes is critical in developing models to predict daily loads and apportion sources of the microbial parameters used to regulate water quality. Accordingly, this paper presents a synthesis of FIO concentration and export coefficient data for the summer bathing season, with some comparative winter data, for 205 river/stream sampling points widely distributed across mainland UK. In terms of both geometric mean (GM) FIO concentrations and export coefficients (expressed as cfu km(-2) h(-1)), the results reveal (1) statistically significant elevations at high flow compared with base flow, with concentrations typically increasing by more than an order of magnitude and export coefficients by about two orders; (2) significantly higher values in summer than in winter under high-flow conditions; and (3) extremely wide variability between the catchments (e.g. four orders of magnitude range for GM faecal coliform concentrations), which closely reflects land use-with urban areas and improved pastures identified as key FIO sources. Generally, these two most polluting land uses are concentrated in lowland areas where runoff (m3 km(-2) h(-1)) is low compared with upland areas, which in the UK are dominated by rough grazing and forestry. Consequently, contrasts in export coefficients between land use types are less than for FIO concentrations. The GMs reported for most land use categories are based on 13 sites and exhibit quite narrow confidence intervals. They may therefore be applied with some confidence to other catchments in the UK and similar geographical regions elsewhere. Examples are presented to illustrate how the results can be used to estimate daily summer base- and high-flow FIO loads for catchments with different land use types, and to assess the likely effectiveness of certain strategies for reducing FIO pollutant loadings in areas with extensive areas of lowland improved pasture. 相似文献
5.
Benjamin W. B. Holman Damian Collins Ashleigh K. Kilgannon David L. Hopkins 《Journal of texture studies》2020,51(4):559-566
In this study, the relationship between sensory evaluation and several objective metrics of beef tenderness was tested. Objective metrics included shear force, sarcomere length, collagen content, myofibrillar, and sarcoplasmic protein solubility and particle size analysis. These results were compared to consumer panel scores of tenderness for the same aged beef striploin (longissimus lumborum muscle) samples. There was found to be a significant relationship between sarcomere length, shear force, and particle size with tenderness scores. Collagen content and protein solubilities were not associated to tenderness scores (p > 0.05). Sarcomere length contributions for explaining tenderness variation were overlapped by the contributions of shear force (collinearity). Independent models demonstrated that the lower 95% confidence interval of the fitted regression line exceeded 50% acceptance of tenderness when shear force values <42.6 N and when particle size values <198 μm. We can recommend these as thresholds for consumer acceptance of beef tenderness, although considerations of sample type, analytical methodology, and consumer demographics should be made prior to their adoption. This provision was based on the variation in tenderness scores evident between individual panelists and experimental striploins. 相似文献
6.
7.
Hopkins PE Baraket M Barnat EV Beechem TE Kearney SP Duda JC Robinson JT Walton SG 《Nano letters》2012,12(2):590-595
Graphene-based devices have garnered tremendous attention due to the unique physical properties arising from this purely two-dimensional carbon sheet leading to tremendous efficiency in the transport of thermal carriers (i.e., phonons). However, it is necessary for this two-dimensional material to be able to efficiently transport heat into the surrounding 3D device architecture in order to fully capitalize on its intrinsic transport capabilities. Therefore, the thermal boundary conductance at graphene interfaces is a critical parameter in the realization of graphene electronics and thermal solutions. In this work, we examine the role of chemical functionalization on the thermal boundary conductance across metal/graphene interfaces. Specifically, we metalize graphene that has been plasma functionalized and then measure the thermal boundary conductance at Al/graphene/SiO(2) contacts with time domain thermoreflectance. The addition of adsorbates to the graphene surfaces are shown to influence the cross plane thermal conductance; this behavior is attributed to changes in the bonding between the metal and the graphene, as both the phonon flux and the vibrational mismatch between the materials are each subject to the interfacial bond strength. These results demonstrate plasma-based functionalization of graphene surfaces is a viable approach to manipulate the thermal boundary conductance. 相似文献
8.
We find evidence for the universality of two relative bibliometric indicators of the quality of individual scientific publications taken from different data sets. One of these is a new index that considers both citation and reference counts. We demonstrate this universality for relatively well cited publications from a single institute, grouped by year of publication and by faculty or by department. We show similar behaviour in publications submitted to the arXiv e-print archive, grouped by year of submission and by sub-archive. We also find that for reasonably well cited papers this distribution is well fitted by a lognormal with a variance of around ??2?=?1.3 which is consistent with the results of Radicchi et al. (Proc Natl Acad Sci USA 105:17268?C17272, 2008). Our work demonstrates that comparisons can be made between publications from different disciplines and publication dates, regardless of their citation count and without expensive access to the whole world-wide citation graph. Further, it shows that averages of the logarithm of such relative bibliometric indices deal with the issue of long tails and avoid the need for statistics based on lengthy ranking procedures. 相似文献
9.
Ben Shneiderman Catherine Plaisant Rodrigo Botafogo Don Hopkins William Weiland 《New Review of Hypermedia and Multimedia》2013,19(2):101-117
Since browsing hypertext can present a formidable cognitive challenge, user interface design plays a major role in determining acceptability. In the Unix workstation version of Hyperties, a research-oriented prototype, we focussed on design features that facilitate browsing. We first give a general overview of Hyperties and its markup language. Customizable documents can be generated by the conditional text feature that enables dynamic and selective display of text and graphics. In addition we present: — an innovative solution to link identification: pop-out graphical buttons of arbitrary shape. — application of pie menus to permit low cognitive load actions that reduce the distraction of common actions, such as page turning or window selection. — multiple window selection strategies that reduce clutter and housekeeping effort. We preferred piles-of-tiles, in which standard-sized windows were arranged in a consistent pattern on the display and actions could be done rapidly, allowing users to concentrate on the contents. 相似文献
10.
K. Vandaele M. Mosiadz S.C. Hopkins A. Patel I. Van Driessche B.A. Glowacki 《Materials Research Bulletin》2012,47(8):2032-2039
An anhydrous TFA-derived YBa2Cu3O7?δ precursor solution was deposited on all chemical solution deposition fully buffered metallic tape by means of electromagnetic drop-on-demand inkjet printing and pyrolysed in a flowing wet O2 atmosphere. The influence of the annealing temperature and time, the gas flow rate and water vapour partial pressure on phase formation, and the morphology and superconducting performance of the resulting film, were investigated. It was found by scanning Hall probe magnetometry that reproducible superconducting films with a critical current density of 0.18 MA/cm2 can be produced after annealing for 2 h at 728 °C, without metal substrate oxidation, in a flowing 200 ppm O2 in Ar atmosphere with 31 mbar water vapour partial pressure. 相似文献