全文获取类型
收费全文 | 619篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 30篇 |
综合类 | 2篇 |
化学工业 | 118篇 |
金属工艺 | 17篇 |
机械仪表 | 10篇 |
建筑科学 | 14篇 |
能源动力 | 8篇 |
轻工业 | 44篇 |
石油天然气 | 1篇 |
无线电 | 62篇 |
一般工业技术 | 142篇 |
冶金工业 | 157篇 |
原子能技术 | 4篇 |
自动化技术 | 24篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 23篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 18篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 25篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 67篇 |
1997年 | 46篇 |
1996年 | 25篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1967年 | 4篇 |
排序方式: 共有633条查询结果,搜索用时 0 毫秒
121.
Effect of essential oil compounds and plant extracts on decay and termite resistance of wood 总被引:2,自引:0,他引:2
S. Nami Kartal Won-Joung Hwang Yuji Imamura Yasuo Sekine 《Holz als Roh- und Werkstoff》2006,64(6):455-461
Essential oils and their derivatives have a long history of safe usage as antimicrobial agents in food industry. In this study various essential oils and extracts from plants were screened for their ability to inhibit wood decay and termite attack in laboratory decay and termite resistance tests using treated wood specimens. In the laboratory decay resistance tests, wood specimens treated with essential oil compounds were subjected to brown-rot fungus, Tyromyces palustris, and white-rot fungus, Trametes versicolor for three months. The specimens were also subjected to termite attack by subterranean termites, Coptotermes formosanus for three weeks in laboratory conditions. The formulation with cinnamaldehyde (DF3) was found to be effective against both the brown-rot and white-rot fungi used in the study. However, the formulation with cinnamic acid (DF8) was able to protect wood specimens against only the white rot fungus and about 50% mass loss occurred in the specimens subjected to the brown-rot fungus. The mass losses in the wood specimens treated with cassia oil containing formulation (DF4) showed that cassia oil was effective against both fungi. The wood tar oil and dodecanal compounds also inhibited fungal decay in the specimens. The wood specimens treated with the formulations used in termite resistance tests were more resistant against the termites when compared to specimens treated with the formulations in decay resistance tests. Even after severe weathering process, treated wood specimens showed resistance against the subterranean termites. Results suggest that essential oils and plant extracts might be important to develop new wood preservatives that are less harmful to the environment and humans than recently available ones. 相似文献
122.
Carol A Clausen S Nami Kartal Rachel A Arango Frederick Green III 《Nanoscale research letters》2011,6(1):427
Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites (Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%, respectively) in the group of wood blocks treated with 2.5 and 5.0% ZnSO4. We conclude that termites were repelled from consuming wood treated with nano-ZnO, but when consumed it was more toxic to eastern subterranean termites than wood treated with the soluble metal oxide formulation. There were no differences in leaching or termite mortality between the two particle sizes of nano-ZnO. 相似文献
123.
Dihydroxy fatty acid-based (DF) dendron-stabilized gold nanoparticles (AuNps) were synthesized without adding any external reducing or stabilizing agent. Each DHA base dendron (G1, G2, or G3) possesses a single thiol at the focal point and free -OH groups at the other terminal and as a result can be used to reduce AuCl4− to Au0 and stabilize the nascent AuNps by the thiol group. The size and distribution of the AuNp produced can also be correlated with the rate of Au (III) reduction. TEM images vividly demonstrate the specific morphology of gold nanoparticles with different sizes and shapes obtained by using different generations of DF dendrons. 相似文献
124.
The experimental results for moisture measurement of green tea usingmicrowave free-space technique are presented. The method is based on a ratioof phase shifts at two microwave frequencies after propagating through asample of green tea. It is shown that the method provides the moisturecontent of tea leaves from 6% to 32% on a dry basis without any knowledge onthe thickness and the density of sample. The mean and the maximum errors inthe moisture determination for tea leaves were 1.2% and 3.7%, respectively. 相似文献
125.
Oxidation kinetics of low-oxygen silicon carbide fiber 总被引:2,自引:0,他引:2
The effect of partial pressure and temperature on the oxidation rate of low-oxygen silicon carbide fiber (Hi-Nicalon) has been investigated. The initial oxidation rate was described by a two-dimensional disc contracting formula for reaction control, and the activation energy was 155 kJ/mol. The rate at the later stage of oxidation obeyed the equation for diffusion control, and the activation energy was 109 kJ/mol. Both the rate constants were proportional to oxygen partial pressure. The diffusion species through the SiO2 film are considered to be oxygen molecules. 相似文献
126.
Williams M Haywood AM Harper EM Johnson AL Knowles T Leng MJ Lunt DJ Okamura B Taylor PD Zalasiewicz J 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2009,367(1886):85-108
This paper reviews North Atlantic shelf seas palaeoclimate during the interval 4-3Ma, prior to and incorporating the 'Mid-Pliocene warm period' (ca 3.29-2.97Ma). Fossil assemblages and stable isotope data demonstrate northwards extension of subtropical faunas along the coast of the Carolinas-Virginia (Yorktown and Duplin Formations) relative to the present day, suggesting a more vigorous Florida Current, with reduced seasonality and warm water extending north of Cape Hatteras (reconstructed annual range for Virginia 12-30 degrees C). This interpretation supports conceptual models of increased meridional heat transport for the Pliocene. Sea temperatures for Florida (Lower Pinecrest Beds) were similar to or slightly cooler than (summers 25-27 degrees C) today, and were probably influenced by seasonal upwelling of cold deep water. Reduced seasonality is also apparent in the Coralline Crag Formation of the southern North Sea, with ostracods suggesting winter sea temperatures of 10 degrees C (modern 4 degrees C). However, estimates from Pliocene bivalves (3.6-16.6 degrees C) are similar to or cooler than the present day. This 'mixed' signal is problematic given warmer seas in the Carolinas-Virginia, and climate model and oceanographic data that show warmer seas in the 'Mid-Pliocene' eastern North Atlantic. This may be because the Coralline Crag Formation was deposited prior to peak Mid-Pliocene warmth. 相似文献
127.
Toshio Shimoo Takehiro Morita Kiyohito Okamura 《Journal of the American Ceramic Society》2001,84(12):2975-2980
Polycarbosilane-derived low-oxygen SiC fibers, Hi-Nicalon, were heat-treated for 36 ks at temperatures from 1273 to 1773 K in CO2 gas. The oxidation of the fibers was investigated through the examination of mass change, crystal phase, resistivity, morphology, and tensile strength. The mass gain, growth of β-SiC crystallites, reduction of resistivity of the fiber core, and formation of protective SiO2 film were observed for the fibers after heat treatment in CO2 gas. SiO2 film crystallized into cristobalite above 1573 K. Despite the low oxygen potential of CO2 gas ( p O2 = 1.22 Pa at 1273 K − 1.78 × 102 Pa at 1773 K), Hi-Nicalon fibers were passively oxidized at a high rate. There was a large loss of tensile strength in the as-oxidized state at higher temperatures because of imperfections in the SiO2 film. On the other hand, the fiber cores showed better strength retention even after oxidation at 1773 K. 相似文献
128.
129.
130.
Y Okamura Y Sugita Y Mochizuki H Iida H Mori K Shimada 《Canadian Metallurgical Quarterly》1996,44(11):2104-2108
Coronary artery bypass grafting in a 64-year-old male with a severe calcified ascending aorta was performed under the beating heart, because of insufficient cardiopulmonary bypass. The patient suffered inferior and anterolateral myocardial infarction with moderate mitral regurgitation. Computerized tomography showed a severely calcified ascending aorta. During the operation, cardiopulmonary bypass was conducted with femoral arterial cannulation and bicaval cannulation. Adequate perfusion flow, however, could not be achieved. Anastomoses of left internal thoracic artery-left anterior descending artery and right gastroepiploic artery-right coronary artery were performed under a beating heart supported by cardiopulmonary bypass. The patient made an uneventful recovery and postoperative angiography revealed patent grafts. Mitral regurgitation remained unchanged, but the postoperative lifestyle has been stable for the last 15 months. 相似文献