全文获取类型
收费全文 | 26870篇 |
免费 | 2164篇 |
国内免费 | 905篇 |
学科分类
工业技术 | 29939篇 |
出版年
2024年 | 130篇 |
2023年 | 359篇 |
2022年 | 628篇 |
2021年 | 726篇 |
2020年 | 758篇 |
2019年 | 684篇 |
2018年 | 703篇 |
2017年 | 802篇 |
2016年 | 901篇 |
2015年 | 875篇 |
2014年 | 1440篇 |
2013年 | 1538篇 |
2012年 | 1873篇 |
2011年 | 1913篇 |
2010年 | 1403篇 |
2009年 | 1559篇 |
2008年 | 1338篇 |
2007年 | 1738篇 |
2006年 | 1641篇 |
2005年 | 1428篇 |
2004年 | 1190篇 |
2003年 | 1169篇 |
2002年 | 1025篇 |
2001年 | 835篇 |
2000年 | 672篇 |
1999年 | 545篇 |
1998年 | 407篇 |
1997年 | 320篇 |
1996年 | 243篇 |
1995年 | 204篇 |
1994年 | 161篇 |
1993年 | 123篇 |
1992年 | 126篇 |
1991年 | 102篇 |
1990年 | 73篇 |
1989年 | 72篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 5篇 |
1980年 | 12篇 |
1975年 | 2篇 |
1965年 | 2篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
由于干态聚合物电解质目前还不能满足聚合物锂离子电池的应用要求,人们致力于开发含液体增塑剂的聚合物电解质,包括凝胶型和微孔型两类体系。本文综述了含液聚合物电解质的最新进展,重点论述了各种新体系和新方法。 相似文献
3.
H. Yamamoto N. Heyamoto T. Matsui N. Murayama J. Shibata 《International Journal of Thermophysics》2003,24(5):1385-1394
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel. 相似文献
4.
文章简要分析了我国目前在中硬岩石爆破中工业炸药的使用情况,介绍了山西兴安化学材料厂新研制的一种适用于硬岩爆破的高爆速、高威力水胶炸药新品种,对其性能、爆破效果、经济实用性和安全性等进行了阐述。 相似文献
5.
Daniela M. Nevskaia Maria Luisa Rojas Cervantes Antonio Guerrero Ruíz Juan de Dios Lpez Gonzlez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):249-256
Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m2 g?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed. 相似文献
6.
7.
Poly(vinyl alcohol) is crosslinked in dilute solution (c=0.1 wt%) with glutaraldehyde. The reaction product is characterized by viscometry and gel permeation chromatography (g.p.c.). The intrinsic viscosity decreases with increasing degree of crosslinking and does not depend on temperature. G.p.c. reveals that the reaction product is not homogeneous, but consists of a mixture of particles with different sizes, possibly both intra- and intermolecularly crosslinked molecules. The intramolecularly crosslinked molecules are smaller in size than the initial polymer molecules and their size depends on the degree of crosslinking. They possess a narrow particle size distribution even if the initial polymer sample had a broad molecular weight distribution. 相似文献
8.
直接氯化法合成对硝基氯化苄 总被引:1,自引:0,他引:1
介绍了以对硝基甲苯和氯气为原料 ,在催化剂存在下合成对硝基氯化苄的方法 ,考察了催化剂种类、反应温度、溶剂配比等因素对反应的影响 ,优化的反应条件为 :对硝基甲苯用量 1 3 7g,对硝基甲苯 /邻二氯苯 (摩尔比 ) =1∶ 0 .6,w (偶氮二异丁腈 ) =0 .6% ,反应时间 3 h,反应温度 1 60℃ ,产物单程收率大于 65 % ;将反应混合物中未反应的原料分离后 ,以无水乙醇为溶剂结晶纯化 ,物料 /溶剂 (摩尔比 ) =1∶ 1 .5时晶体含量在 99.0 %以上 ,结晶收率达 67 相似文献
9.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability. 相似文献
10.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献