全文获取类型
收费全文 | 21613篇 |
免费 | 2946篇 |
国内免费 | 1913篇 |
专业分类
电工技术 | 1872篇 |
综合类 | 2628篇 |
化学工业 | 1947篇 |
金属工艺 | 1164篇 |
机械仪表 | 1954篇 |
建筑科学 | 1818篇 |
矿业工程 | 1113篇 |
能源动力 | 770篇 |
轻工业 | 584篇 |
水利工程 | 642篇 |
石油天然气 | 717篇 |
武器工业 | 750篇 |
无线电 | 3052篇 |
一般工业技术 | 1974篇 |
冶金工业 | 559篇 |
原子能技术 | 192篇 |
自动化技术 | 4736篇 |
出版年
2024年 | 130篇 |
2023年 | 376篇 |
2022年 | 635篇 |
2021年 | 760篇 |
2020年 | 827篇 |
2019年 | 711篇 |
2018年 | 732篇 |
2017年 | 936篇 |
2016年 | 934篇 |
2015年 | 998篇 |
2014年 | 1516篇 |
2013年 | 1533篇 |
2012年 | 1782篇 |
2011年 | 1782篇 |
2010年 | 1423篇 |
2009年 | 1413篇 |
2008年 | 1345篇 |
2007年 | 1499篇 |
2006年 | 1270篇 |
2005年 | 1025篇 |
2004年 | 788篇 |
2003年 | 676篇 |
2002年 | 507篇 |
2001年 | 499篇 |
2000年 | 407篇 |
1999年 | 340篇 |
1998年 | 250篇 |
1997年 | 281篇 |
1996年 | 221篇 |
1995年 | 182篇 |
1994年 | 153篇 |
1993年 | 112篇 |
1992年 | 94篇 |
1991年 | 73篇 |
1990年 | 56篇 |
1989年 | 51篇 |
1988年 | 39篇 |
1987年 | 28篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
R. Talero 《Cement and Concrete Research》2002,32(5):707-717
In this research, former XRD experiments have been verified by Le Chatelier-Ansttet (L-A) test. For this purpose, 28 cements consisting of 7 Portland cements and 21 blended cements containing 20%, 30% and 40% metakaolin have been submitted to the Le Chatelier-Anstett (L-A) test for 2 years. With all these cements, L-A specimens were manufactured and a direct parameter was measured for these specimens: increase in diameter, Δ∅, or diameter growth. Other complementary determinations were chemical analysis, XDA patterns and SEM of ettringites and specific properties of some cements tested. The experimental results have borne out that the formation rate of the ettringite formed from the reactive alumina, Al2O3r−, present in pozzolans must be considerably higher than the formation rate of the ettringite from C3A and much higher than the ettringite from C4AF, both present in OPC. Owing to this, these ettringites were proposed being named “rapid formation” (ett-rf), “slow formation” (ett-lf) and “very slow formation” (ett-vlf) ettringites, respectively. On the other hand, these experimental results have also shown that the ett-rf has a much smaller size than the ett-lf (this is a direct consequence of the aforementioned conclusion); that almost all the alumina, Al2O3, present in M pozzolan must be regarded as being “reactive,” Al2O3r−, or at least, the greatest part; that the detrimental effects derived from gypsum attack are shown much earlier in these POZC than in their plain OPC and, to such an extent, that this aggressive action can be described as rapid gypsum attack; and that none of the 21 POZC tested can be described as high nor moderate sulphate resistant cements according to L-A test. 相似文献
42.
43.
44.
45.
Relative grain boundary energies can be simply related to true dihedral angles, which are the angles between grain boundary planes meeting at triple edges in polycrystals. Some limited efforts in the measurement of true dihedral angles have used the technique of serial sectioning, which is usually cumbersome and time consuming. In this study the three‐dimensional probe called the ‘disector’ has been employed to evaluate true dihedral angles. This probe, combined with automated image processing, introduces precision as well as efficiency, overcomes the disadvantages of the two‐dimensional probe and is far less tedious and less complicated than serial sectioning. It is shown that the technique is relatively simple and therefore can be applied to obtain a significantly large and accurate statistical sample of true dihedral angles. The application of this method is demonstrated by evaluating the triple junction geometry and the associated relative grain boundary energies in polycrystalline 316L austenitic stainless steel. 相似文献
46.
The grafting of acrylic acid onto electron beam‐irradiated polypropylene was carried out using preirradiation method. The stability of peroxy radicals was investigated by electron spin resonance. It was found that the decay of peroxy radicals is much faster at 70°C than at 40°C and ambient temperature. The grafting has been observed to be strongly dependent on the monomer dilution in the reaction medium. The grafting was ascertained by attenuated total reflectance (ATR). The distribution of grafts across the samples was monitored by infrared microscopy. It was found that the graft management is considerably influenced by composition of the grafting medium. The grafting involving pure monomer leads to the surface enrichment with the polyacrylic acid chains. The samples grafted in pure monomer led to much lower contact angles as compared to the diluted monomer solution. The swelling of the grafted samples also showed a trend that was governed by the graft management. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 546–553, 2006 相似文献
47.
为解决鱼雷捷联系统的初始对准,提出了失准角及陀螺随机常值漂移快速估计方法,经数字仿真,对缩短初始对准时间,提高初始对准精度有较好的效果。 相似文献
48.
提出了基于AutoCAD2 0 0 0的图解法求解机械加工过程中工艺转角的问题 ,并针对具体的应用实例给出了圆满的解答 ,并验证了其精度。 相似文献
49.
介绍了一种新型悬臂棒条筛分机械,论述了其结构、工作原理和技术特性。从理论和实践两方面论证了它的结构、处理能力、筛分效率、返矿率都明显优于普通悬臂棒条筛分机械,可广泛应用于高炉槽下烧结矿的筛分作业。 相似文献
50.
保证跌落试件姿态的方法 总被引:1,自引:1,他引:0
进行包装件的自由跌落试验时,必须保证试件姿态符合标准规定。笔者在实践中总结出一种保证试件姿态和检验试件姿态误差的具体方法。 相似文献