全文获取类型
收费全文 | 23223篇 |
免费 | 2722篇 |
国内免费 | 1780篇 |
专业分类
电工技术 | 2283篇 |
技术理论 | 3篇 |
综合类 | 1922篇 |
化学工业 | 3096篇 |
金属工艺 | 1634篇 |
机械仪表 | 1563篇 |
建筑科学 | 1981篇 |
矿业工程 | 635篇 |
能源动力 | 788篇 |
轻工业 | 1615篇 |
水利工程 | 494篇 |
石油天然气 | 1024篇 |
武器工业 | 307篇 |
无线电 | 2728篇 |
一般工业技术 | 2625篇 |
冶金工业 | 924篇 |
原子能技术 | 255篇 |
自动化技术 | 3848篇 |
出版年
2024年 | 146篇 |
2023年 | 517篇 |
2022年 | 913篇 |
2021年 | 1402篇 |
2020年 | 968篇 |
2019年 | 711篇 |
2018年 | 801篇 |
2017年 | 890篇 |
2016年 | 777篇 |
2015年 | 1061篇 |
2014年 | 1269篇 |
2013年 | 1608篇 |
2012年 | 1771篇 |
2011年 | 1841篇 |
2010年 | 1620篇 |
2009年 | 1457篇 |
2008年 | 1467篇 |
2007年 | 1451篇 |
2006年 | 1272篇 |
2005年 | 1009篇 |
2004年 | 754篇 |
2003年 | 691篇 |
2002年 | 783篇 |
2001年 | 695篇 |
2000年 | 477篇 |
1999年 | 330篇 |
1998年 | 171篇 |
1997年 | 187篇 |
1996年 | 142篇 |
1995年 | 123篇 |
1994年 | 82篇 |
1993年 | 69篇 |
1992年 | 59篇 |
1991年 | 40篇 |
1990年 | 42篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 10篇 |
1986年 | 17篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1959年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
碱尘暴是一种特殊的尘暴类型,在全球范围内有着不同程度的分布.本文利用SEM-EDX和ICP对吉林西部两个采样点的碱尘气溶胶进行分析,获得了碱尘气溶胶样品的矿物组成和常量元素组成.结果表明样品矿物成份主要是石英(54.9%)和长石(28.3%),其次为碳酸盐(4.4%)和氯盐(2.7%)碱尘的金属元素以Ca,Na为主,含量排序为Ca,Na,Al,Fe,K,Mg,Ti;吉林西部碱尘气溶胶与普通沙尘气溶胶在矿物组成和元素分布上均有明显差别.大布苏湖碱尘矿物来源于湖盆阶地碎屑沉积物、粉砂粘土碎屑沉积物、湖盆边缘季节性结晶盐.Na元素主要来源于钠长石和食盐;Ca元素来源主要是钙长石、方解石和白云石. 相似文献
102.
103.
104.
中草药在染发、乌发化妆品中的应用和评价 总被引:3,自引:1,他引:3
概述了中药染发、乌发化妆品的现状,中草药在染发、乌发化妆品中的应用和研究,中草药乌发提取物的功能评价并提出了染发、乌发功能性中草药研究方略之设想。 相似文献
105.
膜分离技术在丙烯尾气回收中的应用 总被引:2,自引:0,他引:2
分析了聚丙烯生产过程中压缩 /冷凝法丙烯尾气回收的不足 ,介绍了压缩 /冷凝 /有机蒸汽膜法在丙烯尾气回收中的应用 相似文献
106.
107.
It is well known that a so-called “three-dimensional filler network structure” will be constructed in the polymer/layered silicate nanocomposites when the content of layered clay reaches a threshold value, at which the silicate sheets are incapable of freely rotating, due to physical jamming and connecting of the nanodispersed layered silicate. In this article, the effect of such clay network on the mobility and relaxation of macromolecular chains in isotactic polypropylene(iPP)/organoclay nanocomposites was investigated in detail with a combination of DMTA, DSC, TGA, TEM, rheometry and melt flow index measurements. The main aim is to establish a relationship between the mesoscopic filler network structure and the macroscopic properties of the polymer nanocomposites, particularly to explore the role of the clay network on the mobility and relaxation of macromolecular chains. It was found that the nanodispersed clay tactoids and layers play less important or dominant roles on the mobility of iPP chains depending on the formation of percolating filler network. The turning point of macroscopic properties appeared at 1 wt% organoclay content. Before this point, the effect of organoclay can be negligible, and the increase of chain mobility was ascribed to the decrease of molecular weight of polymer chains, as commonly occurs during dynamic melt processing; after this point, however, a reduced mobility of chains and a retarded chain relaxation were observed and attributed to the formation of a mesoscopic filler network. The essential features of such a mesoscopic organoclay network were estimated and discussed on the basis of stress relaxation and structural reversion measurements. A schematic model was proposed to describe the different relaxation and motion behaviors of macromolecular chains in the unfilled polymer and the filled hybrids with partial and percolated organoclay networks, respectively. 相似文献
108.
Using a low‐melting‐point polymer, copolyamide, as raw material, adhesive meltblown webs were formed on the ordinary melt‐blowing line by using the accessory air and the accessory air chamber. The webs thus produced exhibit narrower fiber diameter distribution and a more uniform pore structure. At the same time, four main melt‐blowing parameters, the primary air pressure, the accessory air pressure, the melt throughput rate, and the die‐to‐collector distance, are discussed in terms of their influence on geometric mean diameter of fibers and fiber diameter distribution. POLYM. ENG. SCI., 46:1–7, 2006. © 2005 Society of Plastics Engineers 相似文献
109.
In order to improve the mechanical and ablation properties of 2D-carbon/carbon composites, a SiC filler was added to a 2D-preform before isothermal chemical vapor infiltration densification by using a powder infiltration technique. Backscattered electron images showed that the SiC filler was mainly concentrated between the fiber bundles and between the layers. The tensile and flexural strengths of the composites were improved by the addition of the SiC filler because of the increase of interfacial surface areas between the bundles and between the layers, the less residual open porosity, and also the strong bonding between the SiC particles and the pyrocarbon matrix. The composites with filler experienced a 15.2% lower thickness erosion rate and a 51.7% lower mass erosion rate, compared to those C/C without filler. This was attributed to the low oxygen permeability of the SiO2 shielding the exterior inter-bundle pores as well as to a thermal barrier effect. 相似文献
110.
MgO-CaO-TiO2系材料的烧结性能及抗水化性能 总被引:2,自引:0,他引:2
以白云石、工业钛白粉、轻烧镁砂为原料配制了不同组成的MgO-CaO-TiO2材料,分别于1500℃、1550℃、1600℃、1650℃保温3 h煅烧后,研究了材料的烧结性能,并采用蒸压法(0.1 MPa下蒸压2 h)研究了烧后试样的抗水化性能.研究结果表明1550~1600℃煅烧后,试样均达到了良好的烧结,相对密度达到92%以上,原始配料中的CaO全部转化成了不易水化的CaO·TiO2,因而所有试样均表现出优良的抗水化性能. 相似文献