全文获取类型
收费全文 | 1679篇 |
免费 | 17篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 235篇 |
金属工艺 | 10篇 |
机械仪表 | 15篇 |
建筑科学 | 48篇 |
矿业工程 | 3篇 |
能源动力 | 6篇 |
轻工业 | 171篇 |
水利工程 | 14篇 |
石油天然气 | 3篇 |
无线电 | 97篇 |
一般工业技术 | 226篇 |
冶金工业 | 682篇 |
原子能技术 | 9篇 |
自动化技术 | 167篇 |
出版年
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 21篇 |
2015年 | 10篇 |
2014年 | 23篇 |
2013年 | 72篇 |
2012年 | 44篇 |
2011年 | 71篇 |
2010年 | 51篇 |
2009年 | 51篇 |
2008年 | 58篇 |
2007年 | 65篇 |
2006年 | 80篇 |
2005年 | 63篇 |
2004年 | 65篇 |
2003年 | 69篇 |
2002年 | 58篇 |
2001年 | 29篇 |
2000年 | 29篇 |
1999年 | 26篇 |
1998年 | 43篇 |
1997年 | 40篇 |
1996年 | 50篇 |
1995年 | 26篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 28篇 |
1991年 | 15篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 30篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1984年 | 37篇 |
1983年 | 40篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 22篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1975年 | 18篇 |
1974年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有1696条查询结果,搜索用时 15 毫秒
71.
Easy access to large information collections is of great importance in many aspects of everyday life. However, limitations in information and communication technologies have so far prevented the average person from taking much advantage of existing resources. Historical documentaries held by national archives constitute some of the most precious yet least accessible cultural information. The ECHO project has facilitated accessibility to this type of precious information by developing a digital library (DL) service for historical films belonging to large national audiovisual archives. 相似文献
72.
73.
Rholes William S.; Blackwell Janette; Jordan Carol; Walters Connie 《Canadian Metallurgical Quarterly》1980,16(6):616
Examined susceptibility to learned helplessness among 20 children from each of kindergarten, Grade 1, Grade 3, and Grade 5 classes by exposing groups of Ss to either repeated failure or repeated success on hidden figures problems. Helplessness was measured by Ss' persistence in looking for hidden figures and their capacity to find them following repeated success or failure. It was hypothesized that younger Ss would be less susceptible to helplessness than older ones, due to age-related differences in causal attributions for success and failure. Results confirm the hypothesis in that failure, relative to success, had significantly less influence on the level of helplessness in younger Ss' behavior. It is suggested that the development of attributional capabilities during the preschool and early elementary school years has important ramifications for cognitive theories of motivation. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
75.
A new experimental method is described for non-isothermal thermogravimetry (TG) involving combustion of mixtures of sieved coal with sieved calcium-containing sorbents. This rapid TG method utilizes a baseline for TG combustion of coal alone, derives an equation that gives a semi-quantitative measure (±10% repeatability) of the coal's reactive sulphur retained by the sorbent, the extent of retention of S02 generated in situ during combustion varying with different sorbents. The method permits direct variation in separate experiments of the calcium-to-sulphur ratio during combustion and relative ranking of different sorbents by retention of reactive sulphur in combustion. Relative rankings are presented for three pre-calcined natural stones (two limestones and one dolomite); these results correlate with relative rankings from another TG method reported in the literature. It is suggested that this new method is useful for pre-screening the effectiveness of S02 sorbents considered for use in fluidizedbed combustion of coal. 相似文献
76.
The behavior of macromolecular systems at different temperatures is often crucial to their biological activity and function. While heat-induced changes of individual proteins are readily monitored by a number of spectroscopic methods, changes in noncovalent complexes of biomolecules are more challenging to interpret. Nanoelectrospray mass spectrometry is becoming increasingly powerful in the study of large noncovalent complexes, and here we describe the design, characterization, and application of a novel probe that allows the thermocontrol of the solution in the electrospray capillary. The transition temperature for the unfolding of the protein lysozyme is readily obtained and correlates closely with that measured by fluorescence spectroscopy, thereby demonstrating the validity of this approach. We apply this technique to the study of the 200-kDa complex of the small heat shock protein TaHSP16.9, revealing both its dissociation into suboligomeric species and an increase in its size and polydispersity at elevated temperatures. In contrast, gas-phase activation of this complex is also carried out and yields a dissociation pathway fundamentally different from that observed for thermal activation in solution. As such, this probe allows the study of the reversible heat-induced changes of noncovalent complexes in a biologically relevant manner. 相似文献
77.
Nilsson CL 《Analytical chemistry》2003,75(15):348A-353A
78.
Keetch CA Hernánndez H Sterling A Baumert M Allen MH Robinson CV 《Analytical chemistry》2003,75(18):4937-4941
Nanoflow electrospray mass spectrometry has been applied previously to investigate noncovalent protein-protein and protein-ligand interactions. Here we evaluate a commercial microchip device for this application. We show that the microchip can be used to obtain mass spectra of the noncovalent tetramer transthyretin. The device showed a 10-fold increase in signal stability compared with a nanoflow capillary and a high level of nozzle-to-nozzle reproducibility. Binding of the natural ligand thyroxine was clearly observed, and a range of small molecules proposed as inhibitors of transthyretin amyloidosis were shown to be effective in stabilizing the tetramer. We propose that measuring the ability of small molecules to stabilize protein complexes using this automated microchip technology will enable high-throughput screening of multi-protein complexes by mass spectrometry. 相似文献
79.
80.