全文获取类型
收费全文 | 26434篇 |
免费 | 3448篇 |
国内免费 | 1259篇 |
专业分类
电工技术 | 823篇 |
综合类 | 1484篇 |
化学工业 | 5786篇 |
金属工艺 | 4741篇 |
机械仪表 | 1758篇 |
建筑科学 | 873篇 |
矿业工程 | 1002篇 |
能源动力 | 1642篇 |
轻工业 | 1180篇 |
水利工程 | 279篇 |
石油天然气 | 759篇 |
武器工业 | 189篇 |
无线电 | 2250篇 |
一般工业技术 | 4925篇 |
冶金工业 | 2654篇 |
原子能技术 | 352篇 |
自动化技术 | 444篇 |
出版年
2024年 | 103篇 |
2023年 | 824篇 |
2022年 | 784篇 |
2021年 | 1109篇 |
2020年 | 1205篇 |
2019年 | 1180篇 |
2018年 | 923篇 |
2017年 | 1070篇 |
2016年 | 937篇 |
2015年 | 943篇 |
2014年 | 1431篇 |
2013年 | 1639篇 |
2012年 | 1689篇 |
2011年 | 1706篇 |
2010年 | 1237篇 |
2009年 | 1334篇 |
2008年 | 1176篇 |
2007年 | 1529篇 |
2006年 | 1489篇 |
2005年 | 1394篇 |
2004年 | 1079篇 |
2003年 | 1146篇 |
2002年 | 920篇 |
2001年 | 749篇 |
2000年 | 699篇 |
1999年 | 546篇 |
1998年 | 475篇 |
1997年 | 336篇 |
1996年 | 310篇 |
1995年 | 240篇 |
1994年 | 206篇 |
1993年 | 167篇 |
1992年 | 128篇 |
1991年 | 98篇 |
1990年 | 85篇 |
1989年 | 75篇 |
1988年 | 39篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
The metal contact method of rapid freezing is greatly improved by irradiating the specimen with microwaves at 2.45 GHz for a short period of time (50 ms), while pushing the specimen onto the surface of the copper block cooled by liquid N2. The microwave irradiation, together with two technical improvements (a light-mass plunger and a recently developed β-gel shock absorber) for preventing bounce, produces a good freezing zone for squid retina, with high reproducibility for each experimental trial, extending from the contact surface to a depth of about 15 μm, which is comparable to the depth obtained by the metal contact method using liquid He in the absence of microwave irradiation. A good freezing zone was also experimentally demonstrated in specimens of rat liver and heart muscle. Microwave irradiation does not have appreciable effects on the ultrastructure of squid retina. The mechanism underlying the improvement in the rapid freezing under the microwave irradiation is discussed. 相似文献
143.
144.
145.
146.
Mohammad Hossein Keshavarz 《含能材料》2006,14(6):449-452
A new method for prediction of Gurney velocity of explosives is introduced in which energy output is correlated with the heat of detonation, the number of moles of gaseous products of detonation per gram of explosive and the average molecular weight of gaseous products. It is assumed that the CHNO explosive reacts to form products composed of N2 , CO, H2O, CO2, H2,O2 and C(s) as determined by the oxygen balance of the unreacted compound. Good agreement is obtained between measured and calculated values of Gurney velocity as compared to previous correlations which assumed the reaction products to consist of N2 , H2O, CO2 and either C(s) or O2. 相似文献
147.
148.
针对显色剂-过渡金属元素-过氧化氢体系,用分光光度法间接测定羟自由基。通过大量试验,确定了三苯甲烷类酸性酚醌吡喃类为有效显色剂,并确定了溴邻苯三酚红-亚铁离子-过氧化氢体系测定羟自由基的最佳条件,首次推测出其最可能的反应机理为:亚铁离子催化过氧化氢产生羟自由基,羟自由基氧化溴邻苯三酚红上的羰基碳氧双键,破坏其显色的共轭结构,使其褪色,此法可作为筛选羟自由基清除剂的有效方法。 相似文献
149.
H. Fan A. Wright J. Gabaldon A. Rodriguez C.J. Brinker Y.‐B. Jiang 《Advanced functional materials》2006,16(7)
The synthesis of three‐dimensionally ordered, transparent gold‐nanocrystal (NC)/silica superlattice thin films using the self‐assembly (by spin‐coating) of water‐soluble gold nanocrystal micelles and soluble silica is reported by Fan and co‐workers on p. 891. The robust, 3D NC/silica superlattice films are of interest for the development of collective optical and electronic phenomena, and, importantly, for the integration of NC arrays into device architectures. Nanocrystals and their ordered arrays hold many important applications in fields such as catalysis, surface‐enhanced Raman spectroscopy based sensors, memory storage, and electronic and optical nanodevices. Herein, a simple and general method to synthesize ordered, three‐dimensional, transparent gold nanocrystal/silica superlattice thin films by self‐assembly of gold nanocrystal micelles with silica or organosilsesquioxane by spin‐coating is reported. The self‐assembly process is conducted under acidic sol–gel conditions (ca. pH 2), ensuring spin‐solution homogeneity and stability and facilitating the formation of ordered and transparent gold nanocrystal/silica films. The monodisperse nanocrystals are organized within inorganic host matrices as a face‐centered cubic mesostructure, and characterized by transmission electron spectroscopy and X‐ray diffraction. 相似文献
150.
Bilayered palladium (30 nm thick)–magnesium (350 nm thick) thin films were prepared using the pulsed laser deposition technique in the presence of various background gases (Ar, He and a mixture He + H2) under different partial pressures (47 and 27 Pa). According to the deposition atmosphere, the Pd/Mg interface shows either a sharp or an extended transition. The electrochemical hydriding properties and the mechanical stability upon cycling of the Pd/Mg film are greatly improved when an extended «intermixing» zone between the Pd and Mg layers is present. The Pd–Mg films prepared under pure helium fulfill these conditions. 相似文献