全文获取类型
收费全文 | 1632篇 |
免费 | 92篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 6篇 |
化学工业 | 279篇 |
金属工艺 | 25篇 |
机械仪表 | 23篇 |
建筑科学 | 43篇 |
矿业工程 | 2篇 |
能源动力 | 60篇 |
轻工业 | 115篇 |
水利工程 | 30篇 |
石油天然气 | 1篇 |
无线电 | 210篇 |
一般工业技术 | 334篇 |
冶金工业 | 345篇 |
原子能技术 | 5篇 |
自动化技术 | 240篇 |
出版年
2023年 | 24篇 |
2022年 | 17篇 |
2021年 | 36篇 |
2020年 | 35篇 |
2019年 | 57篇 |
2018年 | 52篇 |
2017年 | 52篇 |
2016年 | 55篇 |
2015年 | 45篇 |
2014年 | 64篇 |
2013年 | 96篇 |
2012年 | 94篇 |
2011年 | 127篇 |
2010年 | 88篇 |
2009年 | 88篇 |
2008年 | 82篇 |
2007年 | 73篇 |
2006年 | 58篇 |
2005年 | 57篇 |
2004年 | 54篇 |
2003年 | 22篇 |
2002年 | 28篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 34篇 |
1997年 | 33篇 |
1996年 | 24篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1969年 | 5篇 |
1964年 | 9篇 |
排序方式: 共有1726条查询结果,搜索用时 15 毫秒
61.
Bryan Harder Nathan Jacobson Dwight Myers 《Journal of the American Ceramic Society》2013,96(2):606-612
Oxidation of SiC can occur in a passive mode, where a protective film is generated, or in an active mode, where a volatile suboxide is generated. The transitions from active‐to‐passive and passive‐to‐active are particularly important to understand as they occur via different mechanisms. In Part II of this article, the passive‐to‐active transition is explored. Three different types of SiC are examined—Si‐rich SiC, stoichiometric SiC, and C‐rich SiC. In addition to an in situ transition from passive‐to‐active, the effect of a preformed film on all three types of SiC is explored. It appears that the passive‐to‐active transition occurs when the SiO2 scale begins to react with the SiC substrate. This reaction generates SiO(g) and CO(g), which build pressure beneath the SiO2 scale, eventually causing the oxide to rupture. In addition, the SiO(g) can oxidize a distance away from the surface leading to the formation of SiO2 needles and further promoting this SiO2/SiC reaction. Thermodynamic and kinetic data are used to predict transition pressures of oxygen, which show reasonable agreement with those measured. 相似文献
62.
Susanne V. Hering Nathan M. Kreisberg Mark R. Stolzenburg Gregory S. Lewis 《Aerosol science and technology》2013,47(1):86-96
As part of the California Regional PM 2.5 and PM 10 Air Quality Study (CRPAQS) particle size distributions were measured simultaneously at two sites; the city of Fresno and the agricultural site of Angiola. Reported here are data obtained by scanning mobility analysis over the size range from 10 nm to 400 nm for the intensive study period from December 1, 2000 through February 6, 2001. These high time resolution data show variability in the character of the distributions, as well as the in the total number concentrations. The most pronounced feature of the data set is a consistent, nighttime maxima in particle number concentrations with a modal diameter near 80 nm during the evening hours at the urban Fresno site. Although these maxima are correlated with CO, NO, and black carbon, the particle size is larger than the 30–40 nm modal diameters observed for traffic aerosols during the commute hours, and is attributed to a non-vehicle source. At the agricultural site, the morning maxima particle number concentration coincides with the maxima in NO concentration, but often precedes the morning maxima in black carbon. Values for the geometric mean particle diameter varied from day to day, but are correlated between the two sites, with somewhat larger particle sizes at Angiola during periods of stagnation. 相似文献
63.
Robert J. Osborn Nathan F. Taylor Chance W. Spencer Don R. Collins 《Aerosol science and technology》2013,47(9):759-772
A field-deployable instrument has been developed that isolates from an ambient aerosol those particles that have critical supersaturations, Sc, within a narrow, user-specified, range. This Differential Activation Separator (DAS) consists of two continuous flow diffusion chambers housed within a single enclosure. Particles are introduced into the upstream chamber referred to as the CCN remover (CCNR) near the centerline between a warm, water-soaked, plate and a cool, continuously circulated, water bath. Those particles that activate at the resulting peak supersaturation, Sp, grow quickly and fall into the water bath. The remaining aerosol enters the second chamber referred to as the CCN separator (CCNS), which differs from the CCNR primarily in the use of a salt solution in the lower bath. The imposed temperature differential establishes an Sp slightly higher than that maintained in the upstream chamber, while the presence of a salt solution at the lower boundary results in a subsaturated region in roughly the lower half of the chamber. Those particles having (Sp)CCNR < S c < (Sp)CCNS activate in this chamber and begin to fall due to gravitational settling. Before reaching the lower bath, the droplets evaporate in the subsaturated environment and continue to travel towards the chamber exit. The previously activated particles in the lower half of the chamber and the unactivated particles in the upper half are extracted in separate flows that are subsequently dried. Calibration of the DAS was achieved by measuring the size distribution of separated particles when a polydisperse ammonium sulfate aerosol was introduced. 相似文献
64.
Nathan D. Marsh Mary J. Wornat Lawrence T. Scott Atena Necula Arthur L. Lafleur Elaine F. Plummer 《Polycyclic Aromatic Compounds》2013,33(4):379-402
In order to investigate new aspects of polycyclic aromatic hydrocarbon (PAH) growth and soot formation, we have synthesized special reference standards of cyclopenta-fused PAH (CP-PAH) and ethynyl-substituted PAH. We have identified several of these CP-PAH and ethynyl-PAH in benzene droplet combustion products, using high pressure liquid chromatography (HPLC) and ultraviolet-visible (UV) absorption spectroscopy. Although one CP-PAH identified in these products - acenaphthylene - has previously been identified as a product of a variety of combustion systems, we have identified six additional CP-PAH and two ethynyl-PAH which have never before been unequivocally identified as the products of benzene pyrolysis or combustion: acephenanthrylene, aceanthrylene, cyclopent[hi]acephenanthrylene, cyclopenta[cd]fluoranthene, cyclopenta[cd] pyrene, dicyclopenta[cd, jk]pyrene, 2-ethynylnaphthalene, and 1-ethynylacenaphthylene. We present the corresponding UV absorption spectra obtained from the HPLC analysis of benzene droplet combustion products, and compare them to the UV absorption 相似文献
65.
Nathan M. Korlesky Lucas J. Stolp Dharma R. Kodali Robert Goldschmidt William C. Byrdwell 《Journal of the American Oil Chemists' Society》2016,93(7):995-1005
Montmorency sour cherry (Prunus cerasus L.) pit oil (CPO) was extracted and characterized by various methods including: GC, LC–MS, NMR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X‐ray powder diffraction (XRD). The oil gave an acid value of 1.45 mg KOH/g, saponification value of 193 mg KOH/g and unsaponifiable matter content of 0.72 %. The oil contained oleic (O) and linoleic (l ) acids as the major components with small concentrations of α‐eleostearic acid (El, 9Z,11E,13E‐octadecatrienoic acid) and saturated fatty acid palmitic (P) acid. The CPO contained six major triacyglycerols (TAG), OOO (16.83 %), OLO (16.64 %), LLO (13.20 %), OLP (7.25 %), OOP (6.49 %) and LElL (6.16 %) plus a number of other minor TAG. The TAG containing at least one saturated fatty acid constitute 33 % of the total. The polymorphic behavior of CPO as studied by DSC and XRD confirmed the presence of α, β′ and β crystal forms. The oxidative induction time of CPO was 30.3 min at 130 °C and the thermal decomposition temperature was 352 °C. 相似文献
66.
Kartavya Jain Carl Wu Sundar V. Atre Goran Jovanovic Vinod Narayanan Shoichi Kimura Vincent Sprenkle Nathan Canfield Sukumar Roy 《International Journal of Applied Ceramic Technology》2009,6(3):410-419
Microreactors as a novel concept in chemical technology enable the introduction of new reaction procedures in chemistry, pharmaceutical industry, and molecular biology. These miniaturized reaction systems offer many exceptional technical advantages for a large number of applications. One major application is in the bulk synthesis of nanoparticles. Despite the availability of a plethora of nanoparticle synthesis processes, there exist many difficulties in controlling the shape, size, and purity of nanoparticles in large quantities in a safe and cost-effective manner. These difficulties have been the principal factors adversely limiting the applications of ceramic nanoparticles. Recent experiments have shown that to study the process of growth and formation of nanoparticles, a reactor having much smaller dimensions, namely a microreactor is more appropriate. These studies have also shown that a microchannel reactor provides control over the mean residence time and hence over the nanoparticle size and shape. This paper deals with the design, fabrication, and testing issues related to a high temperature, ceramic microreactor by investigating the use of reactive gas streams in arrays of microchannel reactors. These innovations offer the potential to overcome the barriers associated with synthesis of ceramic nanoparticles in large quantities. 相似文献
67.
Ockwig NW Delgado-Friedrichs O O'Keeffe M Yaghi OM 《Accounts of chemical research》2005,38(3):176-182
The structures of all 1127 three-periodic extended metal-organic frameworks (MOFs) reported in the Cambridge Structure Database have been analyzed, and their underlying topology has been determined. It is remarkable that among the almost infinite number of net topologies that are available for MOFs to adopt, only a handful of nets are actually observed. The discovery of this inversion between expected and observed nets led us to deduce a system of classification "taxonomy" for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis has been approached. Specifically, three levels of complexity are defined that embody rules "grammar" for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that "codes" for a specific structure and, indeed, only that structure. 相似文献
68.
The weak-link approach (WLA) to supramolecular assemblies allows for the design of multimetallic two- and three-dimensional arrays, host-guest architectures, sensors, catalysts, switches, and signal amplification devices. This Account describes the course of our investigations in this area beginning with the development of a chemical tool kit of building blocks consisting of multiple metals and ligands. These building blocks can be rationally mixed and matched to provide structures with a wide range of properties that have been used to develop functional supramolecular architectures, including chemical sensors and allosteric catalysts. 相似文献
69.
Taranjot Kaur Justin Nussbaum Sanboh Lee Kevin Rodriguez Nathan B. Crane Julie Harmon 《Polymer Engineering and Science》2021,61(1):221-233
Large area projection sintering (LAPS) promises to be a new method in the field of additive manufacturing. Developed in the Mechanical Engineering Department, University of South Florida, LAPS uses long exposure times over a broad area of powder to fuse into dense, reproducible materials. In contrast, LS, a common powder-based additive manufacturing, uses a focused beam of light scanned quickly over the material. Local regions of concentrated high-energy bursts of light lead to higher peak temperatures and differing cooling dynamics and overall crystallinity. The mechanical properties of laser sintered specimens suffer because of uneven particle fusion. LAPS offers the capacity to fine-tune fusion properties through enhanced thermodynamic control of the heating and cooling profiles for sintering. Further research is required to identify the relationship between LAPS build settings and part properties to enable the fabrication of custom parts with desired properties. This study examines the influence of LAPS sintering parameters on chemical structures, crystallinity, mechanical, and thermal properties of polyamide-12 specimens using powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering, scanning electron microscopy, and microhardness testing. It was observed that higher crystallinity was imparted to specimens that were sintered for a shorter time and vice versa. 相似文献
70.
Jianlin Li Zhijia Du Rose E. Ruther Seong Jin AN Lamuel Abraham David Kevin Hays Marissa Wood Nathan D. Phillip Yangping Sheng Chengyu Mao Sergiy Kalnaus Claus Daniel David L. WoodIII 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(9):1484-1496
Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by ~70% from 2008 to 2015, the current battery pack cost ($268/kWh in 2015) is still >2 times what the USABC targets ($125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. This article discusses three major aspects for cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed. 相似文献