全文获取类型
收费全文 | 377篇 |
免费 | 5篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 74篇 |
金属工艺 | 28篇 |
机械仪表 | 16篇 |
建筑科学 | 3篇 |
能源动力 | 4篇 |
轻工业 | 8篇 |
水利工程 | 3篇 |
无线电 | 33篇 |
一般工业技术 | 119篇 |
冶金工业 | 62篇 |
自动化技术 | 12篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 15篇 |
2011年 | 7篇 |
2010年 | 14篇 |
2009年 | 27篇 |
2008年 | 10篇 |
2007年 | 20篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 26篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 16篇 |
1999年 | 23篇 |
1998年 | 22篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有382条查询结果,搜索用时 15 毫秒
51.
Recent studies indicate that centrally released arginine vasopressin (AVP) facilitates brain water permeability in normal and pathological conditions. The effects of central administration of arginine vasopressin (AVP) receptor antagonists on vasogenic brain edema were studied in rats. V1 or V2 receptor antagonists were stereotactically injected into the lateral ventricle 10 min prior to or 1 h after cold brain injury. The injury resulted in significant increases in the mean water content of the lesion and the contralateral hemispheres by 1.15 and 0.38%, respectively. Twenty-four hours after injury, the brain water and sodium contents, the brain swelling, and plasma osmolality were measured. V1 receptor antagonist of 50 ng significantly decreased the brain water and sodium contents and the brain swelling in the adjacent cortex of the lesion without changes in serum osmolality. On the other hand, 5 ng of V1 receptor antagonist and V2 receptor antagonist had no effect on edema. The V1 receptor of AVP is thought to act predominantly on water permeability of the brain. Peptide therapy may become an additional tool for brain edema treatment. 相似文献
52.
Masazumi Tanaka 《Metallurgical and Materials Transactions A》1996,27(9):2678-2685
The influence of aqueous environments on fatigue crack propagation behavior was investigated for two types of structural steel
(SB42 and HT80) in pure and 3 pct NaCl water under freely corroding conditions. In the intermediate to high ΔK region, fatigue crack propagation rates were higher in both aqueous environments and in 1 atm hydrogen than in air for both
types of steel, and the acceleration effect increased power functionally with decreasing frequency from 5 to 0.0005 Hz. Such
a crack growth acceleration property was explained by the mechanism of cyclically induced hydrogen embrittlement, as shown
by the brittle striations formed on the fracture surfaces. On the other hand, in the lower ΔK region, both aqueous environments inversely suppressed crack growth and enhanced the threshold stress intensity factor range
ΔK
th just above the ΔK
th in air, while only in aerated 3 pct NaCl water was the crack observed to grow even under the condition below the ΔK
th in air, not showing the threshold. Probable mechanisms for such fairly complex environmental effects were also suggested. 相似文献
53.
Y Nonaka T Fujii N Kagawa MR Waterman H Takemori M Okamoto 《Canadian Metallurgical Quarterly》1998,258(2):869-878
Dahl's salt-resistant normotensive rats (DR rats) have been previously reported to express cytochrome P-450 (CYP11B1) containing five missense mutations [Matsukawa, N., Nonaka, Y., Higaki, J., Nagano, M., Mikami H., Ogihara, T. & Okamoto, M. (1993) J. Biol. Chem. 268, 9117-9121]. To investigate structure-function relationships of CYP11B, wild-type rat CYP11B1 and CYP11B2 and DR-CYP11B1 (mutant CYP11B1 in Dahl's salt-resistant rats) have been successfully expressed in Escherichia coli. Steroid 11beta-hydroxylase (11beta-OHase) activity observed with DR-CYP11B1 was similar to that of wild-type CYP11B1, while 18-hydroxylase (18-OHase) activity of DR-CYP11B1 was lower than that of wild-type CYP11B1. Mutant CYP11B1s containing a single or a double amino acid substitution associated with DR-CYP11B1 have been also expressed in E. coli to investigate effects of the substitutions on enzymatic activity. Each of the single mutant enzymes showed lower 18-OHase activity than wild-type CYP11B1, but not as low as DR-CYP11B1. A double mutant CYP11B1 with V381L and I384L showed 18-OHase activity at a similar low level to that of DR-CYP11B1. The 19-hydroxylation (19-OHase) activity of DR-CYP11B1 was about one-third of that of the wild-type enzyme and this low activity appeared due to the V443M mutation. These results suggest that three of five amino acid substitutions present in DR-CYP11B1 account for the decreased 18-OHase and 19-OHase activities. A decrease in these enzyme activities may be responsible for the normotension of the DR rats when fed a high-salt diet. 相似文献
54.
55.
The partition of nitrogen between austenite and liquid iron was examined from the measurement of solubilities of nitrogen in these phases. On primary austenite crystallization, nitrogen was rejected into liquid iron at high temperatures and the partition behaviour was reversed at low temperatures. Silicon lowered the critical temperature where the partition behaviour of nitrogen changed. The partition of nitrogen between cementite and austenite was investigated by analysis of nitrogen in iron-carbon-silicon alloys, which were quenched in ice-water from an equilibrium state at subeutectic temperatures, and in the cementite extracted from them. Nitrogen was enriched in cementite for Fe-C-0.5 wt% Si alloy, similar to the case of pure Fe-C alloy. However, silicon reduced the degree of enrichment of nitrogen in cementite. By the use of the partition coefficients, the variations of nitrogen concentrations in the coexisting phases were evaluated during the solidification of cast irons. In the irons with lower carbon concentrations, the supersaturation of nitrogen in liquid iron attained during solidification increased with increasing silicon content, and silicon had a detrimental effect to promote the formation of nitrogen gas blowholes in low-carbon cast irons. 相似文献
56.
M Kuwahara N Fujisaki S Kagawa M Furihata Y Ohtsuki 《Canadian Metallurgical Quarterly》1998,1(4):703-707
Strains (105) of Yersinia pseudotuberculosis isolated in Brazil between 1982 and 1990 were bio-serotyped. They were also studied for plasmid profile, autoagglutination and calcium dependence at 37 degrees C, Congo red uptake, pyrazinamidase activity, esculin hydrolysis, salicin fermentation and drug sensitivity: 95.24% were biotype 2, serogroup O:3; 2.86% were biotype 1, serogroup O:1; and 1.90% were biotype 2, non-agglutinable. Plasmids were found in 77.14% of the strains (one in each strain). There was total correlation between the presence of the virulence plasmid and autoagglutination, calcium dependence at 37 degrees C and Congo red uptake. The esculin, salicin and pyrazinamidase tests were not efficient in differentiating pathogenic from non-pathogenic Y. pseudotuberculosis isolates. All strains were highly sensitive to the drugs used. These results indicate that Y. pseudotuberculosis is a potential pathogen for humans in Brazil, especially because the bio-serogroups detected among animals are those most frequently associated with human diseases. 相似文献
57.
Ultrafine oxide particles were synthesized by introducing aqueous solutions of metal salts into a high-temperature r.f. inductively
coupled plasma (the spray-ICP technique). The particles synthesized were spherical for ZrO2, Y2O3, Sm2O3, La2O3, δ-Al2O3, TiO2 (anatase), β-Bi2O3 and CuO, plate-like for Nd3O2, Cr2O3 and Pr2O3, polyhedral for PrO2, CeO2 and γ-Fe2O3, cubical for NiO, MgO, CaO, Co3O4 and Mn3O4, bar-like for SnO2 and ZnO, and foil-like for β-PbO and MoO3. The products of the alkaline earth group except for magnesium, were hydroxides and/or carbonates, spoiled by atmospheric
H2O and/or CO2. The particle morphology suggests that particle growth is controlled predominantly by the gas-solid reaction occurring on
the surface of nuclei condensed from the gas phase. Some of the oxides revealed a particle morphology characteristic of their
crystal structures. 相似文献
58.
Takashi Mizuguchi Shu-Qi Guo Yutaka Kagawa 《Journal of the American Ceramic Society》2009,92(5):1145-1148
Microstructure of the hot-pressed ZrB2 with MoSi2 additive was investigated by transmission electron microscopy (TEM). The effect of MoSi2 addition on the microstructure of the ceramic was assessed. For the pure ZrB2 , the microstructure consisted of the equiaxed ZrB2 grains and a few elongated ZrB2 grains. For the ZrB2 with MoSi2 additive, the microstructure consisted almost entirely of equiaxed ZrB2 grains. A few dislocations were present in the ZrB2 grains. In addition, high-resolution TEM observations showed that the intergranular amorphous phase was absent at two ZrB2 grain boundaries in the ZrB2 with MoSi2 additive. 相似文献
59.
60.
Co, Ni, Pt, Al, P, Cu, Zn, Ge, Ag, In, Sb or Au inclusions in Sn–Ag based lead free solders were evaluated to study if these nanoparticles can reduce the growth of intermetallic compounds after four time reflow processes and thermal aging. Also, these nanoparticles were studied if they can reduce the frequency of occurrence of intermetallic compound fractures in high impact pull tests. In addition to intermetallic compound analyses, these nanoparticle effects on solder ball hardness were studied if nanoparticles affects solder hardness and displacement in drop tests. Finally, these nanoparticle effects on drop test performance were studied. This study found that Co, Ni and Pt were very effective for the growth of intermetallic compounds and drop test performance compared to Cu, Ag, Au, Zn, Al, In, P, Ge and Sb. 相似文献