全文获取类型
收费全文 | 2744篇 |
免费 | 55篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 35篇 |
综合类 | 1篇 |
化学工业 | 412篇 |
金属工艺 | 63篇 |
机械仪表 | 51篇 |
建筑科学 | 117篇 |
矿业工程 | 14篇 |
能源动力 | 67篇 |
轻工业 | 221篇 |
水利工程 | 33篇 |
石油天然气 | 9篇 |
无线电 | 194篇 |
一般工业技术 | 431篇 |
冶金工业 | 798篇 |
原子能技术 | 25篇 |
自动化技术 | 333篇 |
出版年
2021年 | 21篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 36篇 |
2017年 | 23篇 |
2016年 | 36篇 |
2015年 | 21篇 |
2014年 | 38篇 |
2013年 | 132篇 |
2012年 | 67篇 |
2011年 | 134篇 |
2010年 | 81篇 |
2009年 | 77篇 |
2008年 | 111篇 |
2007年 | 91篇 |
2006年 | 86篇 |
2005年 | 92篇 |
2004年 | 76篇 |
2003年 | 78篇 |
2002年 | 60篇 |
2001年 | 46篇 |
2000年 | 45篇 |
1999年 | 66篇 |
1998年 | 132篇 |
1997年 | 117篇 |
1996年 | 80篇 |
1995年 | 63篇 |
1994年 | 62篇 |
1993年 | 62篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 44篇 |
1989年 | 36篇 |
1988年 | 27篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 46篇 |
1984年 | 47篇 |
1983年 | 34篇 |
1982年 | 36篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 19篇 |
1978年 | 31篇 |
1977年 | 41篇 |
1976年 | 49篇 |
1975年 | 20篇 |
1974年 | 37篇 |
1973年 | 18篇 |
1972年 | 19篇 |
排序方式: 共有2804条查询结果,搜索用时 15 毫秒
11.
Free and bound hydrosoluble protein extracts were prepared from four anatomical areas of a multiple sclerosis (MS) cerebrum and from corresponding anatomical areas of a normal (non-MS) control. Increased levels of IgG and anti-myelin basic protein antibodies (anti-MBP) were detected in all MS samples and they were undetectable in the controls. IgG and anti-MBP from free (unbound) hydrosoluble protein extracts are defined as free IgG and free anti-MBP while IgG and anti-MBP from tissue bound protein extracts are defined as bound IgG and bound anti-MBP. IgG was purified from free protein extracts by protein G Sepharose affinity chromatography and anti-MBP was further isolated from purified IgG by antigen specific (MBP) Sepharose affinity chromatography. Free and bound anti-MBP were reacted with 20 synthetic peptides of human MBP prepared by the Fmoc method. Free anti-MBP, whether in the context of whole protein extracts, or as purified IgG or as purified antibody was completely neutralized by peptides #12, #15, #56 and #56* containing overall residues 75-106, partially neutralized by peptides #27, #16 and #21 containing overall residues 61-83 and did not react with the remaining 13 peptides. Tissue bound anti-MBP was completely neutralized only by peptides #12, #15, #56 and #56* (overall residues 75-106) and showed no reactivity towards the remaining 16 peptides including peptides #27, #16 and #21. Synthetic peptide specificity of free anti-MBP purified from MS cerebrum was identical to previously reported specificity of free anti-MBP from MS cerebrospinal fluid (CSF), while tissue bound anti-MBP, as well as bound anti-MBP from CSF had a more restricted synthetic peptide specificity than free anti-MBP. This suggests that the most likely epitope of anti-MBP is located between residues 84 and 95 of human MBP just proximal to the tri-proline sequence (99-101). 相似文献
12.
13.
14.
Scale and sludge from Bulalo geothermal field, Philippines, have been characterized by whole rock analysis, radioactivity counting, size analysis, light microscopy, scanning electron microscopy, and X-ray diffraction. Their leachability was assessed by regulatory leaching procedures and by sequential extraction. Both scale and sludge consisted mostly of oxides of Si, Al, and Fe with no radionuclides detected. The scale had 10% S content. Sulfides and silicates were important phases in both samples having size ranges from submicron to 2 mm. Geothermal soils at Bulalo have higher than normal soil levels of As, S, Cu, Cr, Zn, and Pb but regulatory leaching tests indicated that these elements are not released. However, the sequential extraction showed that As, Cu, and Zn were leachable under extreme conditions. 相似文献
15.
Cortical implants for the blind 总被引:4,自引:0,他引:4
Arrays of stimulating electrodes can be placed in the brain itself, in the visual cortex, to bring vision to the profoundly blind. However, when designing such devices one needs to take into consideration the fact that the visual pathway maps images onto cortical structures in a complex and unpredictable way 相似文献
16.
The crystallization behaviour of three amorphous alloys, Co50Ni25Si15B10, Ni50Co25Si15B10 and Ni50Co25P15B10, was studied by means of differential thermal analysis in conjunction with scanning transmission electron microscopy. Isochronal annealing showed a strong dependence of crystallization on scan rate over the range of 1.99 to 20.70 K min–1. At high Co/Ni ratios, a sequential two-stage crystallization process involving primary MS-I phase followed by MS-II phase precipitation was observed. At low Co/Ni ratios MS-I and MS-II crystallization were concurrent and inseparable. Replacement of the metalloid Si with P as the glass-former dramatically reduced the activation energy for crystallization as well as the crystallization temperature. A mechanistic understanding of these findings was pursued in light of TEM/STEM microanalysis 相似文献
17.
18.
This paper studies a system of partial differential equations modelling the behaviour of a reverse flow reactor. For the parameters appropriate for the oxidation of ammonia on a Pt/Al2O3 catalyst in a typical laboratory set-up, the reactor may be split into regions where approximate formulas that determine its behaviour are deduced. Numerical calculations are presented and can be used to compare with the analytical formulas. The physical insight gained from the asymptotic analysis suggests a new switching strategy which is the subject of numerical experiments. The switching strategy is found to be efficient at minimising the ammonia exiting the reactor after reversal. 相似文献
19.
20.
Douglas H. Taylor Kirk E. Lagory Daniel J. Zaccaro Ronald J. Pfohl R.Dana Laurie 《The Science of the total environment》1985
Trichloroethylene (TCE) is a common contaminant of underground water supplies. To examine the effect of TCE on the developing central nervous system, rats were exposed to TCE throughout gestation until 21 days postpartum via their dams' drinking water. TCE concentrations of 312 mg/l, 625 mg/l and 1250 mg/l were tested. Exploratory behavior was higher in 60- and 90-day old male rats which were exposed to any level of TCE. The effect of TCE-exposure on locomotor activity (running wheel) was also examined in 60-day old males (625 and 1250 ppm exposure groups). Locomotor activity was significantly higher in rats exposed to 1250 ppm TCE. These data suggest that TCE has long-term effects on behaviour. 相似文献