全文获取类型
收费全文 | 5260篇 |
免费 | 616篇 |
国内免费 | 284篇 |
专业分类
电工技术 | 261篇 |
综合类 | 413篇 |
化学工业 | 964篇 |
金属工艺 | 263篇 |
机械仪表 | 247篇 |
建筑科学 | 429篇 |
矿业工程 | 161篇 |
能源动力 | 149篇 |
轻工业 | 490篇 |
水利工程 | 139篇 |
石油天然气 | 286篇 |
武器工业 | 43篇 |
无线电 | 641篇 |
一般工业技术 | 670篇 |
冶金工业 | 230篇 |
原子能技术 | 41篇 |
自动化技术 | 733篇 |
出版年
2024年 | 24篇 |
2023年 | 97篇 |
2022年 | 180篇 |
2021年 | 279篇 |
2020年 | 218篇 |
2019年 | 209篇 |
2018年 | 216篇 |
2017年 | 250篇 |
2016年 | 202篇 |
2015年 | 237篇 |
2014年 | 264篇 |
2013年 | 377篇 |
2012年 | 373篇 |
2011年 | 341篇 |
2010年 | 293篇 |
2009年 | 273篇 |
2008年 | 306篇 |
2007年 | 232篇 |
2006年 | 214篇 |
2005年 | 183篇 |
2004年 | 152篇 |
2003年 | 191篇 |
2002年 | 243篇 |
2001年 | 223篇 |
2000年 | 124篇 |
1999年 | 84篇 |
1998年 | 57篇 |
1997年 | 55篇 |
1996年 | 48篇 |
1995年 | 45篇 |
1994年 | 30篇 |
1993年 | 30篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有6160条查询结果,搜索用时 15 毫秒
41.
42.
直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程 总被引:10,自引:3,他引:10
直接凝固注模成型(directcoagulationcasting,DCC)是一种崭新的(准)净尺寸陶瓷成型方法。本文报道了采用此法成型Si_3N_4及SiC陶瓷的基本原理和工艺过程。DCC成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中,事先加入到浆料中的生物酶及化学物质通过改变浆料的pH或电解质浓度来改变浆料的胶体化学行为,从而使浆料原位凝固,得到有足够脱模强度的陶瓷坯体。DCC成型的特点为坯体密度高(理论密度的55%~70%),坯体均匀,不用或只需少量的有机添加剂(少于1%),可成型大尺寸、复杂形状、高可靠性的陶瓷部件。 相似文献
43.
44.
45.
Large volume of online review data can reveal consumers’ major interests on domain product, which attracts great research interests from the academic community. Most of the existing works focus on the problems of review summarization, aspect identification or opinion mining from an item’s point of view such as the quality or popularity of products. Considering the fact that users who generate those review texts draw different attentions to product aspects with respect to their own interests, in this article, we aim to learn K users’ interest groups indicated by their review writings. Such K interest groups’ identification can facilitate better understanding of major and potential consumers’ concerns which are crucial for applications like product improvement on customer-oriented design or diverse marketing strategies. Instead of using a traditional text clustering approach, we treat the groupId/clusterId as a hidden variable and use a permutation-based structural topic model called KMM. Through this model, we infer K interest groups’ distribution by discovering not only the frequency of product aspects (Topic Frequency), but also the occurrence priority of respective aspects (Topic Order). They jointly present an informative summarization on the raw review corpus. Our experiment on several real-world review datasets demonstrates a competitive solution. 相似文献
46.
47.
5-烷基-2-氨基-1,3,4-噻二唑的合成及应用 总被引:16,自引:1,他引:16
用硫代氨基脲与甲酸、乙酸、丙酸、丁酸、异丁酸、异戊酸等在盐酸、磷酸、多聚磷酸、硫酸催化下 ,分别合成了 2 -氨基 -1 ,3 ,4-噻二唑 (a)、5 -甲基 -2 -氨基 -1 ,3 ,4-噻二唑 (b)、5 -乙基 -2 -氨基 -1 ,3 ,4-噻二唑 (c)、5 -丙基 -2 -氨基 -1 ,3 ,4-噻二唑 (d)、5 -异丙基 -2 -氨基 -1 ,3 ,4-噻二唑 (e)、5 -异丁基 -2 -氨基 -1 ,3 ,4-噻二唑 (f)。并对工艺条件进行了试验 ,结果表明 :最佳工艺条件为硫代氨基脲与酸的摩尔比为 1∶ 1 .4,合成 2 -氨基 -1 ,3 ,4-噻二唑为多聚磷酸催化 ,合成其它的为浓盐酸催化 ,回流 3 h,产率分别为 96.78%、74.3 4%、73 .67%、71 .68%、68.44%、67.5 4%。同时以 a~f为原料合成了具有抗菌作用的 5 -烷基 -1 ,3 ,4-噻二唑硫脲乙酸和 5 -烷基 -2 -苯基 -硫脲 -1 ,3 ,4-噻二唑的衍生物 相似文献
48.
A three‐dimensional oil‐water turbulent flow and oil separation process in a double‐cone liquid‐liquid hydrocyclone (LLHC) is numerically simulated using FLUENT software. The Euler‐Euler approach and Reynolds‐stress model are combined and adopted in this simulation to handle the challenging situation of anisotropic turbulent two‐phase flow with a higher volumetric ratio (over 10%) in the dispersed phase. It is visualized well in the simulation how separation, aggregation and shift of oil and water proceed in the LLHC. The oil separation efficiency is determined based on flow field and phase concentration distribution. The simulation is verified by comparing predicted and measured separation efficiency in the LLHC. 相似文献
49.
50.
Michael Gelfer Carlos Avila‐orta Lizhi Liu Ling Yang Benjamin Chu Benjamin S. Hsiao Hyun H. Song Mayu Si Miriam Rafailovich Andy H. Tsou 《Polymer Engineering and Science》2002,42(9):1841-1851
A series of nanocomposites prepared by melt‐blending of cloisite‐based organoclays with poly(ethylene‐vinylacetate) (EVA) and neutralized poly (ethylene‐methacrylic acid) (EMA) copolymers were investigated via DSC, small‐angle X‐ray scattering (SAXS), and rheological techniques. SAXS results indicated partial clay exfoliation in all samples. In both EMA and EVA systems, the nominal melting temperature Tm and bulk crystallinity are not significantly affected by the presence of organoclays, suggesting that clay particles are predominantly confined in the amorphous phase. In rheological measurements (above Tm), the EVA‐clay system demonstrated a solid‐like rheological behavior under the small‐strain oscillatory shear, yet it was able to yield and flow under a steady shear, which is the characteristic of physical crosslinking. In contrast, the EMA‐clay system exhibited a melt‐like rheological behavior, where the influence of organoclay on the thermorheological behavior of the EMA composite was quite minimal. We propose that the carbonyl groups of vinylacetate in EVA interact with the clay surface, resulting in a strong physically crosslinking like interaction in the melt. On the other hand, the interaction between EMA and clay is weak because of repulsion between carboxyl anions and negatively charged clay surface. 相似文献