全文获取类型
收费全文 | 14507篇 |
免费 | 1717篇 |
国内免费 | 1026篇 |
专业分类
电工技术 | 1391篇 |
综合类 | 1300篇 |
化学工业 | 1708篇 |
金属工艺 | 1046篇 |
机械仪表 | 933篇 |
建筑科学 | 1042篇 |
矿业工程 | 552篇 |
能源动力 | 362篇 |
轻工业 | 1630篇 |
水利工程 | 414篇 |
石油天然气 | 589篇 |
武器工业 | 259篇 |
无线电 | 1675篇 |
一般工业技术 | 1332篇 |
冶金工业 | 786篇 |
原子能技术 | 226篇 |
自动化技术 | 2005篇 |
出版年
2024年 | 68篇 |
2023年 | 238篇 |
2022年 | 573篇 |
2021年 | 686篇 |
2020年 | 528篇 |
2019年 | 320篇 |
2018年 | 374篇 |
2017年 | 408篇 |
2016年 | 355篇 |
2015年 | 565篇 |
2014年 | 732篇 |
2013年 | 902篇 |
2012年 | 1101篇 |
2011年 | 1223篇 |
2010年 | 1179篇 |
2009年 | 1112篇 |
2008年 | 1207篇 |
2007年 | 1217篇 |
2006年 | 1022篇 |
2005年 | 849篇 |
2004年 | 573篇 |
2003年 | 400篇 |
2002年 | 410篇 |
2001年 | 367篇 |
2000年 | 293篇 |
1999年 | 132篇 |
1998年 | 79篇 |
1997年 | 72篇 |
1996年 | 47篇 |
1995年 | 34篇 |
1994年 | 31篇 |
1993年 | 30篇 |
1992年 | 14篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1959年 | 4篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
YV Panchin YI Arshavsky TG Deliagina GN Orlovsky LB Popova AI Selverston 《Canadian Metallurgical Quarterly》1996,109(2):361-365
The locomotor activity in the marine mollusc Clione limacina has been found to be strongly excited by serotonergic mechanisms. In the present study putative serotonergic cerebropedal neurons were recorded simultaneously with pedal locomotor motoneurons and interneurons. Stimulation of serotonergic neurons produced acceleration of the locomotor rhythm and strengthening of motoneuron discharges. These effects were accompanied by depolarization of motoneurons, while depolarization of the generator interneurons was considerably lower (if it occurred at all). Effects of serotonin application on isolated locomotor and non-locomotor pedal neurons were studied. Serotonin (5 x 10(-7) to 1 x 10(-6) M) affected most pedal neurons. All locomotor neurons were excited by serotonin. This suggests that serotonergic command neurons exert direct influence on locomotor neurons. Effects of serotonin on nonlocomotor neurons were diverse, most neurons being inhibited by serotonin. Some effects of serotonin on locomotor neurons could not be reproduced by neuron depolarization. This suggests that, along with depolarization, serotonin modulates voltage-sensitive membrane properties of the neurons. As a result, serotonin promotes the endogenous rhythmical activity in neurons of the C. limacina locomotor central pattern generator. 相似文献
33.
Hitoshi Furuta Jianhong He Eiichi Watanabe 《Computer-Aided Civil and Infrastructure Engineering》1996,11(1):37-45
Abstract: An efficient knowledge-acquisition support method is required for improvement and maintenance of the knowledge base in durability evaluation of an RC bridge deck. Such a method is proposed in this paper to automatically acquire fuzzy production rules. This method makes joint use of genetic algorithms and a neural network. Using a neural network as a subsystem, the evaluation function of genetic algorithms can be provided with the weights of the neural network. Introducing a neural network into genetic algorithms, it is possible to acquire new knowledge so that the method is useful when it is difficult to acquire knowledge in the field. 相似文献
34.
以L-脯氨酸/吡啶为催化剂,茴香醛和丙二酸为原料,经Knoevenagel 缩合反应合成了对甲氧基肉桂酸.考察了带水剂种类、原料摩尔比、催化剂L-脯氨酸和吡啶用量、反应时间等对对甲氧基肉桂酸收率的影响.结果表明,在以正己烷为带水剂(用量50 mL),茴香醛用量5 mL(0.041 5 mol),丙二酸与茴香醛摩尔比1.2∶1,L-脯氨酸用量(以丙二酸质量计)4.0%,吡啶用量5 mL,反应时间3 h的条件下,对甲氧基肉桂酸重结晶收率达90.0%. 相似文献
35.
36.
本文从6个方面对选钼2个作业段的取样方式进行了校验,通过对检测数据的比对分析,找出了选钼2个作业段数据存在矛盾的原因,并针对原因采取了有效的措施,保证了检测数据的准确性,促进了选钼生产的稳定高效。 相似文献
37.
In this study, nanocrystalline Ni powders and thermally sprayed coatings, containing ultrafine AlN particles, were synthesized
and characterized. The results indicated that the presence of AlN particles in the powders drastically decreased the dimension
of agglomerates formed by cryomilling and increased the surface roughness of the agglomerates. The AlN phase was broken down
into ultrafine particles of approximately 30 nm in size. These particles were dispersed in the Ni matrix and enhanced the
development of a nanocrystalline structure in the Ni matrix during cryomilling. Selected-area diffraction patterns, obtained
from transmission electron microscopy (TEM) and X-ray mapping with scanning electron microscopy (SEM), confirmed the presence
of AlN particles in the coatings. The presence of AlN particles also led to an increase in the amount of NiO phase that was
distributed in the coating, in the form of ultrafine, round particles. AlN particles increased the microhardness of the Ni
coating by approximately 60 pct. Indentation-fracture results also indicated that the fine, dispersed AlN particles raised
the apparent toughness of the Ni coating. The synthesized Ni coatings containing ultrafine AlN particles were characterized
as equiaxed nanocrystalline grains with an average size of 24 nm, in which twins were observed. The increase in microhardness
resulted from both grain refinement and the presence of ultrafine particles. The latter played the primary role in strengthening. 相似文献
38.
为区分不同档次的玫瑰油,利用GC/MS法对高、中档玫瑰油进行了化学成分的定性和定量分析,分别鉴定出63和72种化合物。并对这2种玫瑰油和1种待测样品进行了电子香味扫描,确定电子鼻在玫瑰油档次辨别中的作用。 相似文献
39.
40.