全文获取类型
收费全文 | 265547篇 |
免费 | 23891篇 |
国内免费 | 12987篇 |
专业分类
电工技术 | 17617篇 |
技术理论 | 63篇 |
综合类 | 36849篇 |
化学工业 | 28647篇 |
金属工艺 | 9813篇 |
机械仪表 | 14489篇 |
建筑科学 | 38785篇 |
矿业工程 | 15316篇 |
能源动力 | 8170篇 |
轻工业 | 15313篇 |
水利工程 | 14277篇 |
石油天然气 | 11404篇 |
武器工业 | 2547篇 |
无线电 | 17391篇 |
一般工业技术 | 19107篇 |
冶金工业 | 15543篇 |
原子能技术 | 2710篇 |
自动化技术 | 34384篇 |
出版年
2024年 | 2695篇 |
2023年 | 3026篇 |
2022年 | 5177篇 |
2021年 | 6039篇 |
2020年 | 6414篇 |
2019年 | 5340篇 |
2018年 | 5008篇 |
2017年 | 6080篇 |
2016年 | 7258篇 |
2015年 | 8039篇 |
2014年 | 14763篇 |
2013年 | 13436篇 |
2012年 | 17751篇 |
2011年 | 18543篇 |
2010年 | 14768篇 |
2009年 | 15390篇 |
2008年 | 14386篇 |
2007年 | 18909篇 |
2006年 | 17947篇 |
2005年 | 15718篇 |
2004年 | 13399篇 |
2003年 | 12087篇 |
2002年 | 9954篇 |
2001年 | 8449篇 |
2000年 | 7109篇 |
1999年 | 5803篇 |
1998年 | 4391篇 |
1997年 | 3843篇 |
1996年 | 3556篇 |
1995年 | 3020篇 |
1994年 | 2694篇 |
1993年 | 2014篇 |
1992年 | 1801篇 |
1991年 | 1329篇 |
1990年 | 1161篇 |
1989年 | 1030篇 |
1988年 | 821篇 |
1987年 | 563篇 |
1986年 | 424篇 |
1985年 | 351篇 |
1984年 | 332篇 |
1983年 | 241篇 |
1982年 | 214篇 |
1981年 | 165篇 |
1980年 | 130篇 |
1979年 | 110篇 |
1978年 | 62篇 |
1977年 | 72篇 |
1976年 | 55篇 |
1975年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
The nanometer scale topography of self‐assembling structural protein complexes in animals is believed to induce favorable cell responses. An important example of such nanostructured biological complexes is fibrillar collagen that possesses a cross‐striation structure with a periodicity of 69 nm and a peak‐to‐valley distance of 4–6 nm. Bovine collagen type I was assembled into fibrillar structures in vitro and sedimented onto solid supports. Their structural motif was transferred into a nickel replica by physical vapor deposition of a small‐grained metal layer followed by galvanic plating. The resulting inverted nickel structure was found to faithfully present most of the micrometer and nanometer scale topography of the biological original. This nickel replica was used as a die for the injection molding of a range of different thermoplastic polymers. Total injection molding cycle times were in the range of 30–45 seconds. One of the polymer materials investigated, polyethylene, displayed poor replication of the biological nanotopographical motif. However, the majority of the polymers showed very high replication fidelity as witnessed by their ability to replicate the cross‐striation features of less than 5 nm height difference. The latter group of materials includes poly(propylene), poly(methyl methacrylate), poly(L ‐lactic acid), polycaprolactone, and a copolymer of cyclic and linear olefins (COC). This work suggests that the current limiting factor for the injection molding of nanometer scale topography in thermoplastic polymers lies with the grain size of the initial metal coating of the mold rather than the polymers themselves.
103.
The kinetics of the methanation of carbon dioxide was investigated using an alumina supported Ni-La2O2 catalyst in a differential and integral reactor. In the differential reactor the molar ratio of H2 to CO2 was varied from 0.6 to 30. In the integral reactor the rates were measured with up to 90% conversion. Both reactor tests were carried out at temperatures between 513 and 593 K. The experimental results were described by a Langmuir-Hinshelwood type equation. The kinetics can be explained by assuming equilibrium of dissociative carbon dioxide and hydrogen adsorption, and assuming hydrogenation of surface carbon as the rate determining step. 相似文献
104.
105.
106.
107.
Behavioral cues to deception are instrumental in detecting deception. As one of the primary sources of deception behavior, text has been analyzed at the level of sub-sentence or message but not the discourse of interaction. Additionally, empirical studies on cues to deception in the case of multiple receivers remain nonexistent. To fill these voids, we propose a discourse framework and six hypotheses about deception behaviors in a multi-receiver environment. The deception behaviors are operationalized by discourse features based on an analysis of real-world data. The results of statistical analysis validate the efficacy of discourse features in discriminating deceivers from truth-tellers. 相似文献
108.
柳树沟磷矿开工时技术力量十分薄弱,以自己培养为主.广泛争取设计院等单位支持.基建工程严格按设计施工,并且建立健全各项规章制度,实行科学管理,安全生产文明生产,扩大生产规模,已由年产9万t扩大到20万t,企业经济效益、社会效益十分显著,成为乡镇矿山典范,磷矿企业的标兵. 相似文献
109.
110.
M.?MelgosaEmail author R.?Huertas E.?Hita J.?M.?Roa F.?J.?Heredia J.?Alba M.?J.?Moyano 《Journal of the American Oil Chemists' Society》2004,81(4):323-330
A new color scale was developed from a broad data set of 1700 virgin olive oil samples over four crop seasons, which can be
considered highly representative of the whole color range of virgin olive oils available in Spain. This color scale provides
a new set of 60 color standards, improving the results achieved by the old 60-color standards proposed by the bromthymol blue
method. Seeking the greatest possibility of including a near match between colors of virgin olive oils and proposed standards,
we developed our new color scale using a recent uniform color space, with standards placed in a regular rhombohedral lattice
like the one employed by the Uniform Color Scales of the Optical Society of America. The average color difference between
each of the 1700 virgin olive oils and its nearest standard is reduced from 8.17 CIELAB units, using the bromthymol blue standards,
to 3.99 CIELAB units using the new standards. Within a color tolerance of 7.0 CIELAB units, 93.2% of our virgin olive oils
can be classified with the new standards, but only 59.1% with the bromthymol blue ones. In the interest of future adoption,
the performance of the new color standards should be tested by industry and researchers. 相似文献