全文获取类型
收费全文 | 1128篇 |
免费 | 30篇 |
国内免费 | 3篇 |
学科分类
工业技术 | 1161篇 |
出版年
2023年 | 11篇 |
2022年 | 5篇 |
2021年 | 31篇 |
2020年 | 21篇 |
2019年 | 15篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 36篇 |
2015年 | 21篇 |
2014年 | 40篇 |
2013年 | 80篇 |
2012年 | 56篇 |
2011年 | 73篇 |
2010年 | 50篇 |
2009年 | 47篇 |
2008年 | 54篇 |
2007年 | 52篇 |
2006年 | 55篇 |
2005年 | 35篇 |
2004年 | 39篇 |
2003年 | 31篇 |
2002年 | 23篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 24篇 |
1998年 | 48篇 |
1997年 | 35篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1966年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有1161条查询结果,搜索用时 609 毫秒
101.
A coalescence-fragmentation model has been developed to predict the behaviors of coal mineral particles during the combustion of pulverized bituminous coals or coal blends. Based on the computer-controlled scanning electron microscope (CCSEM) characterization of coal minerals, the particle size distributions (PSDs) and mineral species of ash particles can be simulated. In particular, the interactions among excluded minerals (mainly referring to the excluded Ca-bearing-species and Fe-bearing-species) and included minerals are accounted for in this model. The PSDs and the mineral species of ash particles are derived from the coalescence and fragmentation of coal mineral particles. Based on this proposed model, both of the predicted PSDs and the mineral species of ash particles are in good agreement with their corresponding experimentally measured values. And the comparisons further demonstrate that the combined effects of coalescence of included minerals and fragmentation of excluded minerals have direct impacts on the ash-forming process. In addition, for the coals rich in excluded Ca- and/or Fe-bearing-species, the interactions among included minerals and excluded minerals are another important mechanism governing ash formation for high-rank coals. 相似文献
102.
Different expressions are used in the literature for the stress intensity factors of interface cracks between anisotropic
material. In particular, two of these approaches will be discussed and compared for orthotropic and monoclinic materials.
Relations between the stress intensity factors will be found. Expressions for the interface energy release rate Gi{\mathcal{G}_i} are presented. Although the expressions appear different, they are shown to be the same by using the relations between the
stress intensity factors. Phase angles are defined which may be used in a fracture criterion. 相似文献
103.
Toru Ohira 《Artificial Life and Robotics》2010,15(4):436-438
A rather peculiar phenomenon has been observed while a human was balancing a stick on a fingertip. The balancing time improved
when the subject moved another object with the other hand. This was particularly so for many subjects with medium stick balancing
skills. On the basis of this example, I consider how this seemingly simple task is composed of intricate mixtures of feedback
delay, fluctuations, and predictions. I present some simple models of dynamics in which these factors lead to complex behaviors.
From these examples, I infer that the concept of “nonlocality” could play an important role in characterizing biological and
physiological systems. 相似文献
104.
Toru Nagaoka Yoshiaki Morisada Masao Fukusumi Tadashi Takemoto 《Metallurgical and Materials Transactions B》2010,41(4):864-871
To obtain sound butt-joints of 5056 aluminum alloy rods, ultrasonic-assisted soldering was conducted using Zn-18Sn and Zn-60Sn
alloys. Each solder foil was inserted between rods of 5056 aluminum alloy. Ultrasonic vibration was propagated to faying surfaces
at soldering temperatures below the liquidus temperature of the solder alloys, and then the samples were air cooled to room
temperature. The optimum vibration time at the soldering temperature must be more than 2 seconds to have complete wetting
and less than 4 seconds to avoid excessive dissolution of the 5056 alloy. The 5056 alloy joints soldered using quasi-melting.
Zn-Sn alloys showed greater strength than the joints soldered at the temperatures over its respective liquidus temperature.
As the soldering temperature was increased, the increased formation of the intermetallic compound Mg2Sn or phases containing Mg generated by dissolution of 5056 into the solder layer decreased the joint strength. Ultrasonic-assisted
soldering at an optimum temperature between solidus and liquidus of the Zn-Sn alloys is an important consideration for producing
sound joints with sufficient strength. 相似文献
105.
106.
Russell G. Keanini Jack L. Ferracane Toru Okabe 《Metallurgical and Materials Transactions B》2001,32(3):409-416
This article reports an experimental and theoretical investigation of mercury dissolution from dental amalgams immersed in
neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate
that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury
release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam’s material composition,
particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial
mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn8Hg (γ
2) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu6Sn5 (η′) and consequent exposure of Ag2Hg3 (γ
1) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical
models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper amalgams
in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide
film persists on the amalgam’s surface and lumps diffusive in-film transport into an effective convective boundary condition.
Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam’s external oxide film dissolves on a short
time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model
III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion
of copper in η′ grains and that corrosion proceeds via an oxidation-reduction reaction involving bound copper and diffusing hydrogen ions. The models appear to capture the correct
time dependence of each dissolution mechanism and to provide reasonable fits to the experimental data. 相似文献
107.
M. K. Mazumder A. Teramoto M. Katsumata M. Sekine S. Kawazu H. Koyama 《Microelectronics Reliability》1997,37(10-11)
Wet oxide thicknesses dependence of nitridation effects on electrical characteristics, charge trapping properties and TDDB (Time Dependent Dielectric Breakdown) characteristics have been investigated. It is found that the difference of conduction current between the wet and nitrided wet oxide increases with increasing oxide thickness both for negative and positive bias to the gate until constant current stress is applied. After the stress, with decreasing oxide thickness both in wet and nitrided wet oxide leakage current increases. Up to 60 Å no difference was observed between the wet and nitrided wet oxide but at 50 Å nitrided wet oxide has less increase of current comparing to the wet oxide for the same stress. In wet oxide with increasing stress current density initial hole trap decreases but electron trap increases whereas in nitrided wet oxide has less initial hole trap and also electron trap is less comparing to the wet oxide. Both in wet and nitrided wet oxide for negative bias stress, time to 50 % breakdown decreases with decreasing thickness but at 50 Å a turn-around effect was observed due to nitridation i.e., the 50 % breakdown time is greater for nitrided wet oxide comparing to the wet oxide. On the contrary, for positive bias stress 50 % breakdown time increases with decreasing oxide thickness both in wet and nitrided wet oxide. For positive bias also a turn-around effect is observed at 50 Å i.e., 50% breakdown time is less in nitrided wet oxide comparing to the wet oxide. The improved reliability of nitrided wet oxide at the thin region of 50 Å seems to be due to the increase of more Si---N bond to the interface of oxide and Si comparing to the thick oxide of above 60 Å for the same nitridation conditions. 相似文献
108.
109.
Gennadiy A. Medvedkin Takao Nishi Yuji Katsumata Hideto Miyake Katsuaki Sato 《Solar Energy Materials & Solar Cells》2003,75(1-2):135-143
Point defects in CuGaSe2 single crystals as vacancies VSe, VCu and defect pair (2VCu−+GaCu2+) have been studied by means of electron paramagnetic resonance (EPR) and low-temperature photoluminescence (PL). EPR hyperfine structure has been found at temperatures as low as 1.45–45 K and the temperature dependence of EPR line is discussed. Photo-EPR spectrum reveals optically active behavior of intrinsic point defects in CuGaSe2 crystals. Three bands of PL emission show different origins and two low-energy bands at 1.55 and 1.58 eV have been found to be steady despite H2-, O2- and Se2-annealings. The experimental data added with electric characterization in accordance with the used annealings and together with a defect physics model allow consideration of the point defect ensemble in CuGaSe2 in more detail. 相似文献
110.
Osamu Nakagawa Haruo Shimamoto Tetsuya Ueda Kou Shimomura Tsutomu Hata Toru Tachikawa Jiro Fukushima Toshinobu Banjo Isamu Yamamoto 《Journal of Electronic Materials》1989,18(5):633-643
As electronic devices become more highly integrated, the demand for small, high pin count packages has been increasing. We
have developed two new types of IC packages in response to this demand. One is an ultra thin small outline package (TSOP)
which has been reduced in size from the standard SOP and the other, which uses Tape Automated Bonding (TAB) technology, is
a super thin, high pin count TAB in cap (T.I.C.) package. In this paper, we present these packages and their features along
with the technologies used to improve package reliability and TAB. Thin packages are vulnerable to high humidity exposure,
especially after heat shock.1 The following items were therefore investigated in order to improve humidity resistance: (1)
The molding compound thermal stress, (2) Water absorption into the molding compound and its effect on package cracking during
solder dipping, (3) Chip attach pad area and its affect on package cracking, (4) Adhesion between molding resin and chip attach
pad and its affect on humidity resistance. With the improvements made as a result of these investigations, the reliability
of the new thin packages is similar to that of the standard thicker plastic packages. 相似文献