全文获取类型
收费全文 | 789篇 |
免费 | 2篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 60篇 |
金属工艺 | 4篇 |
机械仪表 | 42篇 |
建筑科学 | 41篇 |
矿业工程 | 4篇 |
能源动力 | 4篇 |
轻工业 | 185篇 |
水利工程 | 63篇 |
石油天然气 | 9篇 |
武器工业 | 1篇 |
无线电 | 18篇 |
一般工业技术 | 313篇 |
冶金工业 | 13篇 |
自动化技术 | 29篇 |
出版年
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 100篇 |
2011年 | 121篇 |
2010年 | 24篇 |
2009年 | 13篇 |
2008年 | 70篇 |
2007年 | 57篇 |
2006年 | 50篇 |
2005年 | 47篇 |
2004年 | 31篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 34篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 26篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 2篇 |
1965年 | 1篇 |
1954年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有791条查询结果,搜索用时 0 毫秒
2.
3.
4.
Praying mantids are models for a wide variety of behavioral, physiological, and ecological studies, and sex pheromones have been assumed to be important components of their biology. However, no mantid pheromone has ever been identified. We collected volatiles emitted by females of the mantid, Sphodromantis lineola, via solid phase microextraction (SPME). Mass spectral analysis revealed the collected volatiles to be a mixture of pentadecanal and tetradecanal. We prepared a synthetic mixture of these compounds, and found that males were both attracted to this mixture and stimulated to exhibit typical precopulatory behavior. We then examined male antennae with scanning electron microscopy, and confirmed the presence of porous antennal sensilla typical of insect pheromone receptors, i.e., that male mantids are equipped with the appropriate morphological apparatus to receive volatile chemical signals. Pheromones, in conjunction with visual and tactile cues, are thus an important feature of the reproductive biology of this, and undoubtedly other species of mantids. In addition to adding a crucial aspect of behavioral biology to our knowledge of this group, identification and synthesis of mantid pheromones may be a first step in attracting and aggregating these generalist predators for use in pest control. 相似文献
5.
The importance of translational control in cancer progression has been underscored by a number of recent studies. However, little is known how cancer cells maintain their high efficiency of translation. Here, we summarize studies that support the role of integrins in translational control, especially at the initiation step, and discuss the various mechanisms by which integrins regulate the recruitment of translational machinery. This review also examines the hypothesis that integrins contribute to various aspects of cancer progression such as proliferation, survival, angiogenesis, and invasion through translational control. 相似文献
6.
7.
8.
9.
10.
For fused tapered fiber couplers with weakly fused cross sections, power coupling takes place between two touching tapered cladding cylinders embedded in the air, and the cylinders then become a strongly guiding structure. We provide accurate polarization-dependent coupling coefficients for such a structure, on the basis of a rigorous vectorial numerical calculation. Our results for the corresponding weakly guiding structure are compared with previous vector perturbation methods base on scalar fields. It is found that the scalar theories are not applicable to those cases with large normalized frequencies or with small fiber separations when the polarization-splitting effect is concerned. 相似文献