全文获取类型
收费全文 | 186篇 |
免费 | 12篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 53篇 |
金属工艺 | 9篇 |
机械仪表 | 7篇 |
建筑科学 | 9篇 |
能源动力 | 3篇 |
轻工业 | 18篇 |
水利工程 | 2篇 |
无线电 | 10篇 |
一般工业技术 | 39篇 |
冶金工业 | 7篇 |
原子能技术 | 4篇 |
自动化技术 | 35篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 27篇 |
2012年 | 9篇 |
2011年 | 11篇 |
2010年 | 12篇 |
2009年 | 3篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 46 毫秒
41.
Olof Hallonsten 《Scientometrics》2013,96(2):497-513
Big Science accelerator complexes are no longer mere tools for nuclear and particle physics, but modern-day experimental resources for a wide range of natural sciences and often named instrumental to scientific and technological development for innovation and economic growth. Facilities compete on a global market to attract the best users and facilitate the best science, and advertise the achievement of their users as markers of quality and productivity. Thus a need has risen for (quantitative) quality assessment of science on the level of facilities. In this article, we examine some quantitative performance measurements frequently used by facilities to display quality: technical reliability, competition for access, and publication records. We report data from the world’s three largest synchrotron radiation facilities from the years 2004–2010, and discuss their meaning and significance by placing them in proper context. While we argue that quality is not possible to completely capture in these quantitative metrics, we acknowledge their apparent importance and, hence, we introduce and propose facilitymetrics as a new feature of the study of modern big science, and as a new empirical focus for scientometrical study, in the hope that future studies can contribute to a deeper, much-needed analysis of the topic. 相似文献
42.
New oxygen evolution anodes for metal electrowinning: MnO<Subscript>2</Subscript> composite electrodes 总被引:1,自引:0,他引:1
Sönke Schmachtel Martina Toiminen Kyösti Kontturi Olof Forsén Michael H. Barker 《Journal of Applied Electrochemistry》2009,39(10):1835-1848
Several modifications of manganese dioxide (MnO2) were investigated for use in composite electrode materials for oxygen evolution, the target application being anodes for
the industrial electrowinning of metals. It is demonstrated that the performance of this material depends strongly on the
modifications of MnO2. All modifications investigated were found to be more active than the usual anode of lead alloyed with silver (PbAg) used
in zinc electrowinning. A composite sample containing chemical manganese dioxide (CMD) was found to give an oxygen evolution
overpotential 0.25 V lower than the standard PbAg anode material. In the second part of the article, we investigate the effect
of varying several parameters of the composite electrode assembly, including the size of the catalyst particles and percentage
of the catalyst material used. A model is proposed where the performance of the material is proportional to the total length
of the boundaries between the lead matrix material and the MnO2 catalyst particles. Physicochemical processes contributing to the observed data are discussed. 相似文献
43.
Direct measurement of glyconanoparticles and lectin interactions by isothermal titration calorimetry
Glyconanomaterials have shown high potential in applications including bioanalysis and nanomedicine. Here, a quantitative analytical technique, based on isothermal titration calorimetry, was developed to characterize the interactions between glyconanoparticles and lectins. By titrating lectins into the glyconanoparticle solution, the apparent dissociation constant, thermodynamic parameters, and the number of binding sites were derived simultaneously. For the glyconanoparticles-lectin binding pairs investigated, a 3-5 order of magnitude affinity enhancement over the free ligand-lectin interactions was observed which can be attributed to the multivalent ligand presentation on the nanoparticles. The impact of ligand density was also studied, and results showed that the affinity increased with the number of glycans on the nanoparticle. 相似文献
44.
Jeffrey A. Thornton William R. Harding Mark Dent Rob C. Hart Hebin Lin Claudia L. Rast Walter Rast Sven‐Olof Ryding Thomas M. Slawski 《Lakes & Reservoirs: Research and Management》2013,18(4):298-316
Eutrophication, or the enrichment of lakes and reservoirs with plant nutrients such as nitrogen and phosphorus, is an ongoing concern facing human societies around the world. Once thought to have been resolved using engineering approaches such as municipal wastewater treatment and storm water management, the problem of nutrient enrichment not only persists, but even continues to increase, being manifested in harmful algal blooms, limitations on access to safe drinking water supplies, and related concerns associated with fresh water in lakes and reservoirs. The continuing concern surrounding eutrophication fulfils the many attributes of a ‘wicked’ or complex problem facing society. This report reviews seriatim the ten attributes of a wicked problem, and the implications of these attributes for lake and reservoir management are discussed. Recognition of eutrophication as a wicked problem requires site‐specific approaches, based on specific knowledge of individual water bodies, as well as an ongoing commitment to lake and reservoir management to respond to new manifestations of the problems of nutrient enrichment as they continue to be revealed over time. 相似文献
45.
Abstract The formation of methanol during treatment of wood meal with nitrogen dioxide is favored by the presence of oxygen and suppressed by addition of sodium sulfate. With 0.5% of added nitrogen dioxide large amounts of methanol were produced at 70°C when kraft lignin was impregnated with 0.5M nitric acid. A markedly increased formation of methanol and nitro groups in the lignin occurred when sodium nitrate was added. At low acidity the effect of sodium nitrate was insignificant. In a solution which was 0.5 molal with respect to nitric acid and 0.8 molal with respect to sodium nitrate, appreciable amounts of methanol and nitro groups were produced even when no nitrogen dioxide was added. This is explained by a generation of nitrogen dioxide from nitric acid in a autocatalytic process favored by high concentrations of nitrate and hydrogen ions. 相似文献
46.
Maryam Khalilian Zhaoxia Bi Jonas Johansson Filip Lenrick Olof Hultin Jovana Colvin Rainer Timm Reine Wallenberg Jonas Ohlsson Mats‐Erik Pistol Anders Gustafsson Lars Samuelson 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(30)
III‐nitrides are considered the material of choice for light‐emitting diodes (LEDs) and lasers in the visible to ultraviolet spectral range. The development is hampered by lattice and thermal mismatch between the nitride layers and the growth substrate leading to high dislocation densities. In order to overcome the issue, efforts have gone into selected area growth of nanowires (NWs), using their small footprint in the substrate to grow virtually dislocation‐free material. Their geometry is defined by six tall side‐facets and a pointed tip which limits the design of optoelectronic devices. Growth of dislocation‐free and atomically smooth 3D hexagonal GaN micro‐prisms with a flat, micrometer‐sized top‐surface is presented. These self‐forming structures are suitable for optical devices such as low‐loss optical cavities for high‐efficiency LEDs. The structures are made by annealing GaN NWs with a thick radial shell, reforming them into hexagonal flat‐top prisms with six equivalents either m‐ or s‐facets depending on the initial heights of the top pyramid and m‐facets of the NWs. This shape is kinetically controlled and the reformation can be explained with a phenomenological model based on Wulff construction that have been developed. It is expected that the results will inspire further research into micron‐sized III‐nitride‐based devices. 相似文献
47.
In the present study, hardwood and softwood pulps were characterized by employing Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS). The pulp samples examined originated from Swedish sulfite and kraft pulp mills, which utilize different cooking processes and modern bleaching technologies. Partial least-squares (PLS) analysis was used to correlate the spectral data obtained with the kappa (K) numbers and carbohydrate compositions of the pulp samples determined by enzymatic hydrolysis and subsequent capillary zone electrophoresis. Using four principal components, the present PLS model based on photoacoustic FT-IR spectra could explain 85% of the variance in the X matrix and 81% of the variance in the Y matrix. The FT-IR-PAS technique in combination with PLS was found to accurately predict the contents of carbohydrates, i.e., xylose, glucose, mannose, arabinose, galactose, and hexenuronic acid residues, as well as the content of lignin measured in terms of K numbers and corrected K numbers of the pulps. From these predictions, the contents of xylan, glucomannan, and cellulose can also be predicted. The content of 4-O-methylglucuronic acid residues is, however, more difficult to predict accurately, using this approach. 相似文献
48.
In this paper, we develop a sliding mode model reference adaptive control (MRAC) scheme for a class of nonlinear dynamic systems with multiple time‐varying state delays, which is robust with respect to unknown plant delays, to a nonlinear perturbation, and to an external disturbance with unknown bounds. An appropriate Lyapunov–Krasovskii‐type functional is introduced to design the adaptation algorithms, and to prove stability. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
49.
In this paper, we develop two sliding mode—model reference adaptive control (MRAC) schemes for a class of delayed nonlinear dynamic systems under actuator failure that are robust with respect to actuator failures, to an unknown plant delay, to a nonlinear perturbation, and to an external disturbance with unknown bounds. Appropriate Lyapunov–Krasovskii‐type functionals with ‘virtual’ adaptation gains are introduced to design the adaptation algorithms, and to prove stability. Two different controllers are designed: one with discontinuous and another with continuous control actions, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
50.
Olof J. Staffans 《国际强度与非线性控制杂志
》1998,8(14):1189-1217
》1998,8(14):1189-1217
This is the first part in a three part study of the suboptimal full information H∞ problem for a well-posed linear system with input space U, state space H, and output space Y. We define a cost function Q(x0,u)=∫〈y(s),Jy(s)〉Yds, where y∈L2loc( R +; Y) is the output of the system with initial state x0∈H and control u∈L2loc( R +; U), and J is a self-adjoint operator on Y. The cost function Qis quadratic in x0 and u, and we suppose (in the stable case) that the second derivative of Q(x0, u) with respect to u is non-singular. This implies that, for each x0∈H, there is a unique critical control ucrit such that the derivative of Q(x0, u) with respect to u vanishes at u=ucrit. We show that ucrit can be written in feedback form whenever the input/output map of the system has a coprime factorization with a (J, S)-inner numerator; here S is a particular self-adjoint operator on U. A number of properties of this feedback representation are established, such as the equivalence of the (J, S)-losslessness of the factorization and the positivity of the Riccati operator on the reachable subspace. © 1998 John Wiley & Sons, Ltd. 相似文献