全文获取类型
收费全文 | 2819篇 |
免费 | 51篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 213篇 |
综合类 | 2篇 |
化学工业 | 656篇 |
金属工艺 | 55篇 |
机械仪表 | 58篇 |
建筑科学 | 56篇 |
能源动力 | 110篇 |
轻工业 | 177篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 268篇 |
一般工业技术 | 517篇 |
冶金工业 | 502篇 |
原子能技术 | 76篇 |
自动化技术 | 188篇 |
出版年
2023年 | 11篇 |
2022年 | 15篇 |
2021年 | 35篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 37篇 |
2017年 | 29篇 |
2016年 | 43篇 |
2015年 | 24篇 |
2014年 | 44篇 |
2013年 | 114篇 |
2012年 | 85篇 |
2011年 | 132篇 |
2010年 | 96篇 |
2009年 | 124篇 |
2008年 | 120篇 |
2007年 | 115篇 |
2006年 | 104篇 |
2005年 | 93篇 |
2004年 | 102篇 |
2003年 | 83篇 |
2002年 | 77篇 |
2001年 | 67篇 |
2000年 | 73篇 |
1999年 | 71篇 |
1998年 | 192篇 |
1997年 | 134篇 |
1996年 | 92篇 |
1995年 | 85篇 |
1994年 | 59篇 |
1993年 | 67篇 |
1992年 | 42篇 |
1991年 | 34篇 |
1990年 | 32篇 |
1989年 | 33篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 38篇 |
1985年 | 51篇 |
1984年 | 26篇 |
1983年 | 30篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 26篇 |
1975年 | 12篇 |
1974年 | 11篇 |
排序方式: 共有2883条查询结果,搜索用时 0 毫秒
31.
The electron spin susceptibility of (BEDT-TTF)(ClMeTCNQ) was measured by ESR under pressure. Analysis of the susceptibility
leads to the temperature dependence of the ionic fraction through the neutral-ionic phase transition, revealing that the transition
is broad and continuous. It is demonstrated that this transition is crossover-like between the two phases, which can be understood
by the unique double-well potential. 相似文献
32.
Y. Takano K. Hiraki T. Takahashi R. Kondo S. Kagoshima T. Hasegawa T. Mocihda Y. Iwasa 《Journal of Low Temperature Physics》2006,142(3-4):647-650
We carried out77Se NMR measurements on BETS2(Cl2TCNQ) under pressure in order to investigate the magnetic properties of the insulating state which appears above 0.6 GPa.
The relaxation rate 1/T1 at 0.7 GPa shows small peak-like anomaly at 20 K, indicating a spin density wave transition as observed in BETS2(Br2TCNQ). 相似文献
33.
Yuichi Miyahara Kiyoshi Matsubara Zenji Horita Terence G. Langdon 《Metallurgical and Materials Transactions A》2005,36(7):1705-1711
The extrusion/equal channel angular pressing (EX-ECAP) processing procedure, in which magnesium-based alloys are subjected
to extrusion followed by ECAP, was applied to a Mg-7.5 pct Al-0.2 pct Zr alloy prepared by casting. Microstructural inspection
showed the EX-ECAP process was effective in reducing the grain size from ∼21 μm after extrusion to an as-pressed grain size of ∼0.8 μm. It is shown through static annealing that these ultrafine grains are reasonably stable up to 473 K, but grain growth occurs
at higher temperatures. Tensile specimens were cut from the billets prepared by EX-ECAP and testing showed these specimens
exhibited superplasticity at relatively low temperatures with maximum elongations up to >700 pct. By processing through EX-ECAP
to a higher imposed strain and thereby increasing the area fraction of high-angle boundaries, it is demonstrated that there
is a potential for achieving high-strain-rate superplasticity.
This article is based on a presentation made at the Symposium entitled “Phase Transformations and Deformation in Magnesium
Alloys,” which occurred during the Spring TMS meeting, March 14–18, 2004, in Charlotte, NC, under the auspices of the ASM-MSCTS
Phase Transformations Committee. 相似文献
34.
Kiyoshi Matsubara Yuichi Miyahara Zenji Horita Terence G. Langdon 《Metallurgical and Materials Transactions A》2004,35(6):1735-1744
Experiments were conducted to evaluate the utility of a new processing procedure developed for Mg-based alloys in which samples
are subjected to a two-step processing route of extrusion followed by equal-channel angular pressing (designated as EX-ECAP).
The experiments were conducted using a Mg-0.6 wt pct Zr alloy and, for comparison purposes, samples of pure Mg. It is shown
that the potential for successfully using ECAP increases in both materials when adopting the EX-ECAP procedure. For the Mg-Zr
alloy, the use of EX-ECAP produces a grain size of ∼1.4 μm when the pressing is undertaken at 573 K. By contrast, using EX-ECAP with pure Mg at 573 K produces a grain size of ∼26
μm. Tensile testing of the Mg-Zr alloy at 523 and 573 K after processing by EX-ECAP revealed the occurrence of significantly
enhanced ductilities with maximum elongations of ∼300 to 400 pct. 相似文献
35.
In order to determine the activities of phosphorus and iron in liquid {Cu‐Fe‐P} alloys, the two coexisting phases of liquid {Cu‐Fe‐P} alloys + <Cu‐Fe‐P> solid solutions were brought into equilibrium with a mixture of Al2O3 + AlPO4 + FexAl2O4 at temperatures of 1416K and 1526K. The oxygen partial pressures were measured with the aid of a solid‐oxide galvanic cell of the type: (+)Mo / Mo + MoO2/ ZrO2(MgO) / {Cu‐Fe‐P} + <Cu‐Fe‐P> + <Al2O3> + <AlPO4> + <FeAl2O4> / Fe(‐) The equilibrium reactions underlying the experiments can be expressed by 2[P]cu + (5/2) (O2) + <Al2O3> = 2 <AlPO4> and x[Fe]Cu + (1/2) (O2) + <Al2O3> = <FexAl2O4> The Henrian activity coefficient referred to 1 wt pct solution in pure liquid copper could be well expressed by the formula log fP° = (4.46±0.40) ‐ (8.67±0.59)/(T/K). The iron activities referred to pure solid iron could be formulated as log aFe =‐ (0.37 ± 0.12) + (500 ±200) /(T/K). 相似文献
36.
S.K. Sharma H. Zushi I. Takagi Y. Hisano T. Shikama S. Morita T. Tanabe N. Yoshida M. Sakamoto Y. Higashizono K. Hanada M. Hasegawa K. Nakamura H. Idei K.N. Sato S. Kawasaki H. Nakashima A. Higashijima Y. Takase 《Journal of Nuclear Materials》2012,420(1-3):83-93
In order to investigate the overall atomic hydrogen background and the dynamic characteristics of wall pumping/fuelling phenomenon, a permeation probe system has been developed and applied in the spherical tokamak QUEST. Reliability of measurements, within ±3% accuracy and a positive correlation with the hydrogen line emission over three orders of magnitude have been demonstrated for more than 3000 various plasma discharges. By comparison of the experimental permeation (flux) curves with the numerically simulated curves, the net incident atomic hydrogen flux is evaluated in the range of 1 × 1019 H m?2 s?1 to 4 × 1020 H m?2 s?1. The atomic flux has been investigated as a function of various plasma operation parameters like RF power, gas pressure and magnetic configuration. Using the static particle balance and permeation measurements, the progress in wall conditioning has been investigated. An inverse correlation between the atomic hydrogen flux and improvement in wall pumping has been observed over the two campaigns. 相似文献
37.
Sota H Yoshimine H Whittier RF Gotoh M Shinohara Y Hasegawa Y Okahata Y 《Analytical chemistry》2002,74(15):3592-3598
Despite high theoretical sensitivity, low-cost manufacture, and compactness potentially amenable to lab-on-a-chip use, practical hurdles have stymied the application of the quartz crystal microbalance (QCM) for aqueous applications such as detection of biomolecular interactions. The chief difficulty lies in achieving a sufficiently stable resonance signal in the presence of even minute fluctuations in hydrostatic pressure. In this work, we present a novel versatile planar sensor chip design (QCM chip) for a microliter-scale on-line biosensor. By sealing the quartz resonator along its edges to a flat, solid support, we provide uniform support for the crystal face not exposed to solvent, greatly decreasing deformation of the crystal resonator under hydrostatic pressure. Furthermore, this cassette design obviates the need for direct handling when exchanging the delicate quartz crystal in the flow cell. A prototype 27-MHz sensor signal exhibited very low noise over a range of flow rates up to 100 microL/min. In contrast, signals obtained from a conventional QCM sensor employing an O-ring-based holder were less stable and deteriorated even further with increasing flow rate. Additional control designs with intermediate amounts of unsupported undersurface yielded intermediate levels of stability, consistent with the interpretation that deformation of the crystal resonator under fluctuating hydraulic pressure is the chief source of noise. As a practical demonstration of the design's high effective sensitivity, we readily detected interaction between myoglobin and surface-bound antibody. 相似文献
38.
We report on preparation and properties of anatase Nb-doped TiO2 transparent conducting oxide films on glass and polyimide substrates. Amorphous Ti0.96Nb0.04O2 films were deposited at room temperature by using sputtering, and were then crystallized through annealing under reducing atmosphere. Use of a seed layer substantially improved the crystallinity and resistivity (ρ) of the films. We attained ρ = 9.2 × 10− 4 Ω cm and transmittance of ~ 70% in the visible region on glass by annealing at 300 °C in vacuum. The minimum ρ of 7.0 × 10− 4 Ω cm was obtained by 400 °C annealing in pure H2. 相似文献
39.
Hirono Kaneyasu Keita Kishigi Yasumasa Hasegawa 《Journal of Low Temperature Physics》2006,142(3-4):469-472
We have measured the electrical resistivities and magnetoresistances (MR) of (EDT-DSDTFVO)2X (X=FeCl4, GaCl4), where EDT-DSDTFVO stands for ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiolemethide. These materials undergo
gradual metal-insulator transitions at Tmin=52 K for FeCl4-salt and Tmin=30 K for GaCl4-salt, respectively. In spite of the similarity of the temperature dependence of the resistivity and its pressure effect,
MR of both salts exhibit a clear contrast, i.e. FeCl4-salt shows negative and GaCl4, positive. Origin of the difference in the sign of MR between these salts are discussed in terms of the existence of π-d
interaction. 相似文献
40.
Atopic dermatitis (AD) is a chronic pruritic skin disease with a complex pathogenesis underlying its heterogeneous clinical phenotypes and endotypes. The skin manifestation of AD reflects the cytokine milieu of a type-2-dominant immunity axis induced by genetic predisposition, innate immunity dysregulation, epidermal barrier defects, and allergic inflammation. However, the detailed pathomechanism of eczematous dermatitis, which is the principal characteristic of AD, remains unclear. This review examines previous studies demonstrating research progress in this area and considers the immunological pathomechanism of “spongiotic dermatitis”, which is the histopathological hallmark of eczematous dermatitis. Studies in this field have revealed the importance of IgE-mediated delayed-type hypersensitivity, the Fas/Fas-ligand system, and cell-mediated cytotoxicity in inducing the apoptosis of keratinocytes in spongiotic dermatitis. Recent studies have demonstrated that, together with infiltrating CD4 T cells, IgE-expressing dendritic cells (i.e., inflammatory dendritic epidermal cells and Langerhans cells) that capture specific allergens (i.e., house dust mites) are present in the spongiotic epidermis of lichenified eczema in patients with IgE-allergic AD. These findings suggest that IgE-mediated delayed-type hypersensitivity plays a pivotal role in the pathogenesis of spongiotic dermatitis in the skin lesions of AD. 相似文献