全文获取类型
收费全文 | 1988篇 |
免费 | 54篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 368篇 |
金属工艺 | 24篇 |
机械仪表 | 18篇 |
建筑科学 | 16篇 |
能源动力 | 70篇 |
轻工业 | 74篇 |
水利工程 | 6篇 |
无线电 | 60篇 |
一般工业技术 | 186篇 |
冶金工业 | 1096篇 |
原子能技术 | 15篇 |
自动化技术 | 93篇 |
出版年
2023年 | 14篇 |
2022年 | 31篇 |
2021年 | 43篇 |
2020年 | 30篇 |
2019年 | 37篇 |
2018年 | 41篇 |
2017年 | 45篇 |
2016年 | 56篇 |
2015年 | 23篇 |
2014年 | 34篇 |
2013年 | 64篇 |
2012年 | 53篇 |
2011年 | 61篇 |
2010年 | 39篇 |
2009年 | 32篇 |
2008年 | 25篇 |
2007年 | 25篇 |
2006年 | 27篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 42篇 |
1998年 | 284篇 |
1997年 | 175篇 |
1996年 | 134篇 |
1995年 | 74篇 |
1994年 | 66篇 |
1993年 | 73篇 |
1992年 | 17篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 27篇 |
1981年 | 29篇 |
1980年 | 25篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 30篇 |
1976年 | 69篇 |
1973年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有2044条查询结果,搜索用时 16 毫秒
31.
32.
33.
34.
Effect of Li+ ions on structure,properties, and actuation of cellulose electro‐active paper actuator
We have reported an electro‐active paper actuator from regenerated cellulose. After dissolving cellulose fibers with a solution of lithium chloride in N,N‐dimethylacetamide, cellulose was regenerated by combining distillation of cellulose solution along with washing with the mixture of deionized water, isopropyl alcohol, and running water. However, the effect of Li+ ions on structure, properties, and the actuation behavior of the actuator was not studied. This article describes the changes in these parameters when the Li+ ions are removed by subjecting it to different running water exposure time. The structure and properties of cellulose electro‐active paper and its actuation behavior were studied. As Li+ ions content reduced from 4354.17 to 10.26 ppm by increasing the exposure time of running water, crystallinity, Young's modulus, and bending displacement decreased. Details about the investigation have been explained. This elimination of ions is important to increase the piezoelectric effect in EAPap by decreasing the ion migration effect. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
35.
Instrumental characterization of clay by XRF,XRD and FTIR 总被引:2,自引:0,他引:2
Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the
chemical compositions of the clay where Al-oxide and silica oxide are present in major quantity whereas XRD confirms the presence
of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters. 相似文献
36.
37.
MN Janakiraman KD Watenpaugh PK Tomich KT Chong SR Turner RA Tommasi S Thaisrivongs JW Strohbach 《Canadian Metallurgical Quarterly》1998,8(10):1237-1242
Potent, non-peptidic, dihydropyrone sulfonamide HIV protease inhibitors have been previously described. Crystallographic analysis of dihydropyrone sulfonamide inhibitor/HIV protease complexes suggested incorporation of a second, C2 symmetry-related sulfonamide group. Selected bis-sulfonamide dihydropyrone analogues display high HIV protease inhibitory activity. 相似文献
38.
A comprehensive study of P, As, and hybrid As/P nLDD junctions is presented in terms of performance, reliability, and manufacturability for the first time. It is found that As junctions limit the performance of deep submicron devices due to unacceptable hot-carrier reliability, whereas a hybrid junction (light dose P added to medium dose As) dramatically improves hot-carrier reliability while maintaining high performance and manufacturability. For Leff of 0.19 μm, using this hybrid junction in a manufacturing process, an inverter gate delay of 32 ps, dc hot carrier life time exceeding ten years, and off-state leakage below 30 pA/μm at 2.9 V have been achieved 相似文献
39.
The lens epithelium of the human eye plays a crucial role in the pathogenesis of primary and secondary cataract. Sixty hematoxylin-eosinstained lens epithelia were examined using a light microscope. Cell parameters were compared to one another in the various age groups of patients, between patients with secondary cataract (radiation cataract, steroid cataract and traumatic cataract) and patients with senile cataract, and between male and female patients. The t-test was used for statistical comparison. The median cell density was 3116.5 cells/mm2. The median nucleus-plasma ratio was 1:2.74. Patients with secondary cataract had a larger medium cell and nucleus area as well as a higher nucleus-plasma ratio and a lower cell density than patients with senile cataract. A part from degenerative and proliferative cell changes we found various cell types. The age of patients and the cause of cataract correlate with morphometric changes of lens epithelium cells. However, there was no correlation between specific cytologic changes and causes of cataract. 相似文献
40.
Activation of auditory cortex during silent lipreading 总被引:1,自引:0,他引:1
GA Calvert ET Bullmore MJ Brammer R Campbell SC Williams PK McGuire PW Woodruff SD Iversen AS David 《Canadian Metallurgical Quarterly》1997,276(5312):593-596
Watching a speaker's lips during face-to-face conversation (lipreading) markedly improves speech perception, particularly in noisy conditions. With functional magnetic resonance imaging it was found that these linguistic visual cues are sufficient to activate auditory cortex in normal hearing individuals in the absence of auditory speech sounds. Two further experiments suggest that these auditory cortical areas are not engaged when an individual is viewing nonlinguistic facial movements but appear to be activated by silent meaningless speechlike movements (pseudospeech). This supports psycholinguistic evidence that seen speech influences the perception of heard speech at a prelexical stage. 相似文献