全文获取类型
收费全文 | 6979篇 |
免费 | 347篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 105篇 |
综合类 | 14篇 |
化学工业 | 1725篇 |
金属工艺 | 160篇 |
机械仪表 | 137篇 |
建筑科学 | 453篇 |
矿业工程 | 32篇 |
能源动力 | 157篇 |
轻工业 | 630篇 |
水利工程 | 58篇 |
石油天然气 | 8篇 |
无线电 | 528篇 |
一般工业技术 | 1349篇 |
冶金工业 | 575篇 |
原子能技术 | 46篇 |
自动化技术 | 1356篇 |
出版年
2024年 | 11篇 |
2023年 | 106篇 |
2022年 | 145篇 |
2021年 | 240篇 |
2020年 | 160篇 |
2019年 | 146篇 |
2018年 | 210篇 |
2017年 | 182篇 |
2016年 | 277篇 |
2015年 | 255篇 |
2014年 | 335篇 |
2013年 | 428篇 |
2012年 | 413篇 |
2011年 | 505篇 |
2010年 | 383篇 |
2009年 | 370篇 |
2008年 | 362篇 |
2007年 | 349篇 |
2006年 | 267篇 |
2005年 | 232篇 |
2004年 | 174篇 |
2003年 | 173篇 |
2002年 | 149篇 |
2001年 | 100篇 |
2000年 | 110篇 |
1999年 | 86篇 |
1998年 | 176篇 |
1997年 | 104篇 |
1996年 | 103篇 |
1995年 | 99篇 |
1994年 | 50篇 |
1993年 | 61篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 30篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 27篇 |
1984年 | 39篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 24篇 |
1977年 | 21篇 |
1976年 | 30篇 |
1974年 | 15篇 |
排序方式: 共有7333条查询结果,搜索用时 9 毫秒
1.
2.
3.
4.
Is there a direct relationship between oral astringency and human salivary protein binding? 总被引:1,自引:0,他引:1
For decades, it is believed that astringency is due to the polyphenol-induced complexation of proline-rich salivary proteins
in the oral cavity. In order to compare for the first time the human sensory threshold concentrations and the salivary protein
binding activity of a series of astringent stimuli, human saliva protein was incubated for 5 min at 37 °C in the presence
of astringent food-derived compounds and, after micro-centrifugation, the amount of the target molecules in the supernatant
was quantitatively determined by HPLC-UV/Vis. Significant protein binding was observed for (−)-epigallocatechin-3-gallate,
(−)-gallocatechin-3-gallate, (+)-gallocatechin, and (−)-catechin-3-gallate, all of which containing at least one galloyl moiety
in the molecule and exhibiting rather high sensory thresholds of more than 200 μmol/L. In comparison, (+)-catechin and procyanidin
B2, both lacking in any galloyl function, showed only comparatively low binding activity and, most interestingly, quercetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside and 3-carboxymethyl-indole-1-N-β-d-glucopyranoside did not show any protein binding at all, although the later N- and O-glycosides exhibited extraordinarily low sensory threshold concentrations of less than 0.001 and 0.0003 μmol/L, respectively.
The data give some first evidence that the quantity of the non-bound, “free” astringent stimulus in the saliva liquid might
be more closely related to the sensory perception of astringency than the amount complexed or precipitated by proteins. It
is therefore questionable as to whether oral perception of astringency is related to the complexation and/or precipitation
of salivary proteins. 相似文献
5.
Herzog K. Schulte E. Atmanand M. A. Schwarz W. 《Automation Science and Engineering, IEEE Transactions on》2007,4(2):282-286
Tracked vehicles capable of locomotion in the deep sea are used for manganese nodule mining. This requires specific technical solutions in various respects. Locomotion in the soft sea bed is one of them. For the Crawler to safely maneuver, an automatic drive mode with slip control of the driving tracks is essential. Based on experimental studies at IKS, University of Siegen, slip control for the NIOT-IKS mining machine has been developed and implemented. The experimental setup for the development of the slip control along with the logic of the automatic driving mode is described. The system is critically discussed and the test results and future work are briefly outlined. Note to Practitioners-The work is carried out as part of the polymetallic nodule mining program of the Government of India. The technique of slip control is a specific requirement for a tracked vehicle used in the deep sea. Slip is common in many vehicles-tracked and otherwise. Examples are steam engines in the early days and ordinary cars while negotiating slush or snow/ice and dozers working in soft soil. While these are manually controlled by drivers who have firsthand knowledge of the environmental conditions, in the case of a mining machine in deep sea, it has to be completely automatic and, hence, is challenging. The knowledge generated in this work could be effectively used by practitioners in other related areas of automobile engineering for updating their expertise. Also, similar techniques may be used for maneuvering vehicles sent to other planets 相似文献
6.
Torsten Bohlin Stefan F. Graebe 《International Journal of Adaptive Control and Signal Processing》1995,9(6):465-490
Grey box identification refers to the practice of identifying dynamical systems in model structures exploiting partial prior information. This contribution reviews a method for stochastic grey box identification and surveys experiences and lessons of applying it to a number of industrial processes. Issues to be addressed include advantages and costs of introducing stochastics into the model, the question of what contribution must be expected from the model designer as opposed to what can be formalized in computer algorithms, and an outlook on future plans to resolve present shortcomings. 相似文献
7.
U. H. Pi D. H. Kim Z. G. Khim U. Kaiser M. Liebmann A. Schwarz R. Wiesendanger 《Journal of Low Temperature Physics》2003,131(5-6):993-1002
We have studied vortex dynamics in Bi2Sr2CaCu2O8 single crystal with low density columnar defects by using a magnetic force microscope. Single crystal Bi2Sr2CaCu2O8 sample was irradiated by 1.3 GeV uranium ion to form artificial pinning centers along the crystalline c-axis. The irradiation dose corresponded to a matching field of 20 gauss. The radius of an individual vortex is approximately 140 nm, which is close to the penetration depth of this material. Magnetic force microscope (MFM) images show that intrinsic crystalline defects such as stacking fault dislocations are very effective pinning centers for vortices in addition to the pinning centers due to ion bombardment. By counting the number of vortex, we found that the flux trapped at each pinning center is a single flux quantum. At higher magnetic field, the vortex structure showed an Abrikosov lattice disturbed only by immobile vortices located at pinning centers. When increasing or decreasing the external magnetic field, the spatial distribution of vortices showed a Bean model like behavior. 相似文献
8.
9.
10.