全文获取类型
收费全文 | 2367篇 |
免费 | 48篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
综合类 | 24篇 |
化学工业 | 483篇 |
金属工艺 | 38篇 |
机械仪表 | 45篇 |
建筑科学 | 77篇 |
矿业工程 | 16篇 |
能源动力 | 38篇 |
轻工业 | 181篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 169篇 |
一般工业技术 | 293篇 |
冶金工业 | 611篇 |
原子能技术 | 37篇 |
自动化技术 | 336篇 |
出版年
2021年 | 27篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2017年 | 23篇 |
2016年 | 43篇 |
2015年 | 37篇 |
2014年 | 32篇 |
2013年 | 127篇 |
2012年 | 67篇 |
2011年 | 83篇 |
2010年 | 84篇 |
2009年 | 80篇 |
2008年 | 93篇 |
2007年 | 91篇 |
2006年 | 78篇 |
2005年 | 89篇 |
2004年 | 65篇 |
2003年 | 44篇 |
2002年 | 63篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 33篇 |
1998年 | 41篇 |
1997年 | 27篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 38篇 |
1992年 | 38篇 |
1991年 | 23篇 |
1990年 | 36篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 39篇 |
1985年 | 47篇 |
1984年 | 52篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 35篇 |
1979年 | 31篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1975年 | 37篇 |
1974年 | 29篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1969年 | 22篇 |
排序方式: 共有2417条查询结果,搜索用时 15 毫秒
61.
62.
Frank Schwingshandl Max Bodmer Gerald Fox 《电气制造》2010,(3):36-41
时下模块化风机齿轮箱的可靠性是一个普遍存在的问题。为此,Maag开发和试制了一种新型Maag DPPV-7-79齿轮箱,在平衡刚度和柔性的基础上能更好地实现载荷的分配均匀,具有较小的应力和最佳齿轮接触模式。 相似文献
63.
Oscar John Gerald Somsen 《Wireless Personal Communications》2013,72(4):2551-2561
Studies of wireless networks often work with a relatively high communication range so that each node typically communicates with a high number of neighbors. This is necessary, with a random placement, to avoid loss of coverage or connectivity. However, communicating through remote neighbors requires more energy, which can be a severe disadvantage since energy is often critical in this type of network. By comparing two-ranges, one to ensure coverage and one to save energy, we identify link-nodes which play an essential role to keep the network connected. Characterizing these nodes and their occurrence in communication routes will help to save energy and increase lifetime of the overall network. Without precautions, these link-nodes receive a high traffic load. Using simulations we find that slightly longer routes can avoid link-nodes and thus reduce average energy consumption. Network lifetime can be extended by identifying these nodes at startup and reducing their energy consumption wherever possible. 相似文献
64.
Zahirul I. Talukder William Underwood Christopher G. Misar Gerald J. Seiler Xiwen Cai Xuehui Li Lili Qi 《International journal of molecular sciences》2022,23(14)
Sclerotinia head rot (HR), caused by Sclerotinia sclerotiorum, is an economically important disease of sunflower with known detrimental effects on yield and quality in humid climates worldwide. The objective of this study was to gain insight into the genetic architecture of HR resistance from a sunflower line HR21 harboring HR resistance introgressed from the wild perennial Helianthus maximiliani. An F2 population derived from the cross of HA 234 (susceptible-line)/HR21 (resistant-line) was evaluated for HR resistance at two locations during 2019–2020. Highly significant genetic variations (p < 0.001) were observed for HR disease incidence (DI) and disease severity (DS) in both individual and combined analyses. Broad sense heritability (H2) estimates across environments for DI and DS were 0.51 and 0.62, respectively. A high-density genetic map of 1420.287 cM was constructed with 6315 SNP/InDel markers developed using genotype-by-sequencing technology. A total of 16 genomic regions on eight sunflower chromosomes, 1, 2, 10, 12, 13, 14, 16 and 17 were associated with HR resistance, each explaining between 3.97 to 16.67% of the phenotypic variance for HR resistance. Eleven of these QTL had resistance alleles from the HR21 parent. Molecular markers flanking the QTL will facilitate marker-assisted selection breeding for HR resistance in sunflower. 相似文献
65.
66.
67.
Hydrogenation of p‐Nitrophenol to p‐Aminophenol as a Test Reaction for the Catalytic Activity of Supported Pt Catalysts
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michael Goepel Majd Al‐Naji Patrick With Gerald Wagner Oliver Oeckler Dirk Enke Roger Gläser 《化学工程与技术》2014,37(3):551-554
Hydrogenation of p‐nitrophenol (PNP) to p‐aminophenol (PAP) using NaBH4 as a reducing agent was studied as a test reaction for determining the catalytic activity of supported Pt catalysts. The initial reaction rate, which is accessible within less than 10 min via online UV‐vis spectroscopy at room temperature, ambient pressure, and in water as solvent, was applied as measure for catalytic activity. For three Pt catalysts supported on porous SiO2, porous glass, and Al2O3, respectively, significant differences in the catalytic activity by almost one order of magnitude were observed. However, especially in the case of very active catalysts, limitations of the reaction by internal or external mass transfer have to be considered. 相似文献
68.
69.
Florian Röper Markus Wolfahrt Sandra Schlögl Georg Kucher Gerald Pinter 《应用聚合物科学杂志》2019,136(19):47506
Repair of composite structures and the impact of demanding environmental conditions is a crucial issue for the aircraft industry because of the increasing use of composites in modern aircraft. Consequently, the impact of environmental conditions common for aircraft applications on repair specimens in comparison to nonrepaired specimens is studied. All specimens are produced from a woven carbon fiber-reinforced epoxy-based prepreg. For the repair-specimens, an epoxy-based film adhesive is used for the soft patch repair approach. During the repair process, the surface of the precured prepreg is prepared by a mechanical method (sanding) and an additional chemical functionalization, respectively. Moisture absorption of the repair specimens is independent of the surface preparation method and higher for the repaired than for the nonrepaired specimens. The key influencing environmental conditions for the tensile strength and the failure mode of the repair specimens are elevated temperature testing as well as hot/wet conditioning and conditioning in deionized water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47506. 相似文献
70.
Sahas R. Rathi E. Bryan Coughlin Shaw Ling Hsu Charles S. Golub Gerald H. Ling Michael J. Tzivanis 《Polymer》2012,53(14):3008-3016
A method to overcome the brittleness of poly (l-lactic acid) (PLLA) by kinetically trapping a continuous low Tg amorphous phase is presented. This morphology is accomplished by exploiting the significant difference in the crystallization temperatures of PLLA vs its stereocomplex with the poly (d-lactic acid) (PDLA) isomer. In our studies, the D isomer is the end block of a triblock copolymer with a configuration of the form PDLAn–Soft Blockm–PDLAn. As demonstrated in this study, when blended with PLLA, the obtained morphology, and improvement in the sample toughness and flexibility, strongly depend on the miscibility of the midblock in the triblock copolymer with the matrix PLLA. The difference in the chemical nature of the midblock clearly affected the stereocomplex crystallization between the PDLA end blocks, the PLLA matrix polymer, and the morphology formed. It is found that the miscible midblock gives rise to a soft continuous amorphous phase while in the case of an immiscible midblock, a glassy phase separated amorphous phase is formed. Dramatically different physical properties can be obtained for various PLLA/triblock copolymer blends giving access to tough, yet flexible, semicrystalline PLLA blends. 相似文献