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111.
A law governing the change in the ductility of metals and alloys under pressure is given: $$\begin{gathered} \left( {\frac{P}{{\sigma _n }}} \right) = \tfrac{1}{2}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P)^{\tfrac{3}{2}} - \varepsilon _{local} (O)^{\tfrac{3}{2}} \} + \tfrac{1}{3}\frac{1}{{\sigma _n }}\frac{{d\sigma }}{{d\varepsilon }}\{ \varepsilon _{local} (P) - \varepsilon _{local} (O)\} + \hfill \\ {\text{ }} + \tfrac{1}{2}\{ \varepsilon _{local} (P)^{\tfrac{1}{2}} - \varepsilon _{local} (O)^{\tfrac{1}{2}} \} \hfill \\ \end{gathered}$$ where P is the hydrostatic pressure, ?local is the strain accumulated from the start of necking to fracture, σ n necking stress and (dσ/d?) the coefficient of linear work hardening. This relation is derived from a newly proposed criterion of ductile fracture, viz. “constancy of hydrostatic tensile stress”, which indicates that the change of ductility with pressure obeys a three halves power law. The observed increase in ductility of widely differing metals and alloys under pressure up to 10,000 kg/cm4 has confirmed that the proposed criterion is acceptable. It is further shown that the ductilities of some copper alloys with low stacking fault energy, such as Cu-Zn and Cu-Ge alloys, increases with pressure at the beginning but the increase stops at fairly low pressure, i.e. 3,500 ~ 4,000 kg/cm2, and their ductilities become almost insensitive to the pressure applied. It is suggested that ductile fracture of metals with low stacking fault energy is dominated by a process which occurs not by the hydrostatic stress component but by shear stress only. 相似文献
112.
Seishi Yajima Kiyohito Okamura Junichi Tanaka Tokuji Hayase 《Journal of Materials Science》1981,16(11):3033-3038
Aluminium alloys were reinforced unidirectionally with 30, 35, 40 and 50 vol %SiC fibres by a liquid-pressing method. The SiC fibres for reinforcement were produced from a polycarbosilane and were yarns consisting of 500 continuous filaments of length 300 m and diameter 13m, having a tensile strength of 2000 MPa. High-temperature tensile and bending strengths of the composites were examined in air in the temperature range from room temperature to 500° C. The strengths were not influenced by temperature up to 400° C, but were decreased at 500° C. The decrease is considered to be caused by the reduction in transfer efficiency of the stress accompanying the decrease in adhesion between fibres and matrix. 相似文献
113.
114.
History of Metrology
Important acts, laws, and decrees on weights and measures 相似文献115.
The lattice and bulk thermal expansions perpendicular to the layer plane of siliconated pyrolytic carbon, PC(Si), produced by pyrolyzing a mixture of propane gas and silicon tetrachloride vapour at the deposition temperatures of 1440 to 2025° C, have been measured over the temperature ranges 20 to 550° C and 20 to 960° C, respectively. The expansion behaviours of PC(Si) are related to the density and the degree of preferred orientation of crystallites, as is the case for pyrolytic carbon without silicon PC. At a deposition temperature of about 1700° C, the bulk thermal expansion coefficient of PC(Si) is about three times as large as that of PC. 相似文献
116.
The present study investigated the metabolic fate of dietary TAG and DAG and also their digestion products in the stomach
and small intestine. A diet containing 10% TAG or DAG oil, enriched in 1,3-DAG, was fed to Wistar rats ad libitum for 9 d. After 18 h of fasting, each diet was re-fed ad libitum for 1 h. The weights of the contents of the stomach and small intestine were measured, and the acylglycerol and FFA levels
were analyzed by GC at 0, 1, and 4 h after the 1-h re-feeding. The amounts of re-fed diet ingested and the gastric and small
intestinal content were not different between the two diet groups. In the TAG diet group, the main products were TAG and DAG,
especially 1(3),2-DAG. In addition, 1,3-DAG and 1(3)-MAG were present in the stomach, and the 1,3-DAG levels increased over
time after the re-feeding period. In the DAG diet group, the main products in the stomach were DAG, MAG, FFA, and TAG. There
were significantly greater amounts of 1,3-DAG, 1(3)-MAG, and FFA in the DAG diet group in the stomach compared with the TAG
diet group. The amount of FFA in the stomach relative to the amount of ingested TAG plus DAG in the DAG diet group was higher
than that in the TAG diet group. Acylglycerol and FFA levels were considerably lower in the small intestine than in the stomach.
These results indicate that, in the stomach, where acyl migration might occur, the digestion products were already different
between TAG and DAG oil ingestion, and that DAG might be more readily digested by lingual lipase compared with TAG. Furthermore,
almost all of the dietary lipid was absorbed, irrespective of the structure of the acylglycerol present in the small intestine. 相似文献
117.
Various kinds of iron particles and an iron species were synthesized from acetylferrocenefurfural resins in a glass-like carbon matrix by heat-treatment. These irons were investigated in terms of magnetic susceptibility, saturation magnetization, esr, and the Mössbauer effect. Body-centred cubic (b c c) iron, expanded b c c iron, hexagonal close-packed iron, and cluster iron were present as ultra-fine iron particles. The presence of Fe+ was well established as an iron species. The formation of iron particles and Fe+ is discussed on the basis of the pyrolysis of ferrocene skeletons in the resin. 相似文献
118.
A CENTRAL LIMIT THEOREM OF FOURIER TRANSFORMS OF STRONGLY DEPENDENT STATIONARY PROCESSES 总被引:1,自引:0,他引:1
Abstract. We consider a limiting distribution of the finite Fourier transforms of observations drawn from a strongly dependent stationary process. It is proved that the finite Fourier transforms at different frequencies are asymptotically independent and normally distributed. Our result can apply to a fractional autoregressive integrated moving-average process and a fractional Gaussian noise, two examples of strongly dependent stationary processes. 相似文献
119.
O Nagata K Sawada M Sato H Sekiyama C Yajima K Hanaoka 《Canadian Metallurgical Quarterly》1998,47(10):1246-1252
We developed a software to control a Graseby 3500 syringe pump for propofol infusion through the serial port of Apple Macintosh/Power-Macintosh computer. This software, "ConGrase", was developed with Metrowerks CodeWarrior Professional (CWP 1) and PowerPlant framework using C++. ConGrase communicates with the syringe pump at least every three seconds, and calculates the estimated blood concentration (EBC) of propofol based on the amount of propofol actually infused by applying either the Euler or Runge-Kutta method using the three-compartment pharmacokinetic model. The parameter sets reported by Gepts et al. are used. ConGrase was released at the 44 th Annual Meeting of the Japan Society of Anesthesiology, and is distributed freely. The mean and S.D. of the emergence EBC calculated by ConGrase were 1.22 micrograms.ml-1 and 0.16 microgram.ml-1, respectively. These values are almost the same as values already reported outside Japan. The necessary wake-up time can be calculated with this estimated concentration. With this system, anesthetists can control the EBC at the required level and avoid long delays before the patients wake up after anesthesia. 相似文献
120.
Hiroshi Yajima 《净水技术》2018,(3)
如何在现有条件下尽可能取得更好的原水?除了上游流域的环境保护、水源水库的合理选址和设计外,通过创新的取水方式,也能达到更优的原水水质。经本刊约稿,来自日本的Hiroshi Yajima教授通过介绍日本已开展研究并应用的分层取水系统,为我国的水库取水方式提供了全新的思路和途径。 相似文献