全文获取类型
收费全文 | 329582篇 |
免费 | 26619篇 |
国内免费 | 17011篇 |
专业分类
电工技术 | 20853篇 |
技术理论 | 60篇 |
综合类 | 45348篇 |
化学工业 | 36278篇 |
金属工艺 | 13569篇 |
机械仪表 | 17768篇 |
建筑科学 | 45576篇 |
矿业工程 | 18239篇 |
能源动力 | 10132篇 |
轻工业 | 19063篇 |
水利工程 | 17153篇 |
石油天然气 | 14564篇 |
武器工业 | 3229篇 |
无线电 | 23239篇 |
一般工业技术 | 24074篇 |
冶金工业 | 19223篇 |
原子能技术 | 3704篇 |
自动化技术 | 41140篇 |
出版年
2024年 | 1040篇 |
2023年 | 3182篇 |
2022年 | 6236篇 |
2021年 | 7450篇 |
2020年 | 7994篇 |
2019年 | 6620篇 |
2018年 | 6350篇 |
2017年 | 7902篇 |
2016年 | 9307篇 |
2015年 | 10478篇 |
2014年 | 19671篇 |
2013年 | 17508篇 |
2012年 | 22300篇 |
2011年 | 23749篇 |
2010年 | 18710篇 |
2009年 | 19583篇 |
2008年 | 18219篇 |
2007年 | 23679篇 |
2006年 | 22189篇 |
2005年 | 19245篇 |
2004年 | 16230篇 |
2003年 | 14544篇 |
2002年 | 11955篇 |
2001年 | 10146篇 |
2000年 | 8512篇 |
1999年 | 6925篇 |
1998年 | 5196篇 |
1997年 | 4515篇 |
1996年 | 4185篇 |
1995年 | 3520篇 |
1994年 | 3093篇 |
1993年 | 2319篇 |
1992年 | 2068篇 |
1991年 | 1528篇 |
1990年 | 1346篇 |
1989年 | 1161篇 |
1988年 | 915篇 |
1987年 | 626篇 |
1986年 | 476篇 |
1985年 | 397篇 |
1984年 | 368篇 |
1983年 | 267篇 |
1982年 | 234篇 |
1981年 | 192篇 |
1980年 | 159篇 |
1979年 | 120篇 |
1978年 | 74篇 |
1977年 | 78篇 |
1976年 | 58篇 |
1975年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In recent years biodegradable polymers, particularly polyesters such as the poly(lactic acid) (PLA) and polycaprolactone (PCL), have gained high interests for their applicability in the biomedical and pharmaceutical fields where they're used for manufacturing various different resorbable devices, from tissue engineering scaffolds to controlled drug release systems. Despite many positive characteristics, processability of these materials still remains a critical issue as they easily tend to degrade during manufacturing. In this article we aimed to assess microextrusion as a nondegradative process for manufacturing PLA and PCL. The results we experimentally obtained, that are hereby presented, set a new point in the on‐going debate on degradation during processing of resorbable polymers as they allow to affirm that microextrusion leaves unmodified molecular weight distributions without producing any evident reductions in mean molecular weight. Microextrusion thus represents a risk‐free high molecular weight polymer processing solution for obtaining nondegraded products within pharmaceutical and biomedical production lines, such as for scaffolds for tissue engineering applications or drug delivery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
992.
S. E. Shalaby N. G. Al-Balakocy M. K. Beliakova O. M. Abdel-Fatah A. M. Elshafei 《应用聚合物科学杂志》2008,109(2):942-950
An effective two-stage method has been developed for imparting antimicrobial properties to regular polyethylene terephthalate (R-PET), polyethylene glycol modified polyethylene terephthalate (PEG-M-PET), R-PET/Cotton blend (R-PET/C) and PEG-M-PET/Cotton blend (PEG-M-PET/C) fabrics. The method consists of partial hydrolysis of the fabrics to create carboxylic groups in PET macromolecules followed by subsequent reaction with dimethylalkylbenzyl ammonium chloride (DMABAC) under alkaline conditions. The reaction conditions such as pH, reaction temperature and time, carboxylic content, and DMABAC concentration were studied. Characterization of the finished fabrics was carried out through scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). All the modified PET fabrics showed excellent antibacterial activity towards Gram-positive (Bacillus mycoides), Gram-negative (Escherichia coli), and nonfilamentous fungus (Candida albicans). The achieved antimicrobial functions on the PET fabrics are durable in repeated laundering processes. Even after laundering 10 times the fabrics could still provide more than 85% of its antimicrobial activity against B. mycoides, E. coli, and C. albicans. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
993.
A novel mixed‐mode expanded bed adsorbent with anion‐exchange properties was explored with benzylamine as the functional ligand. The cellulose composite matrix, densified with stainless steel powder, was prepared with the method of water‐in‐oil suspension thermal regeneration. High activation levels of the cellulose matrix were obtained with allyl bromide because of the relative inertness of the allyl group under the conditions of the activation reaction. After the formation of the bromohydrin with N‐bromosuccinimide and coupling with benzylamine, the activated matrix was derived to function as a mixed‐mode adsorbent containing both hydrophobic and ionic groups. The protein adsorption capacity was investigated with bovine serum albumin as a model protein. The results indicated that the prepared adsorbent could bind bovine serum albumin with a high adsorption capacity, and it showed salt tolerance. Effective desorption was achieved by a pH adjustment across the isoelectric point of the protein. The interactions between the cell and adsorbent were studied, and the bioadhesion was shielded by the adjustment of the salt concentration above 0.1M. Stable fluidization in the expanded bed was obtained even in a 2% (dry weight) yeast suspension. The direct capture of target proteins from a biomass‐containing feedstock without extra dilution steps could be expected with the mixed‐mode adsorbent prepared in this work, and this would be especially appropriate for expanded bed adsorption applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
994.
Reda Karoum Antonio de Lucas-Consuegra Fernando Dorado Jose Luis Valverde Alain Billard Philippe Vernoux 《Journal of Applied Electrochemistry》2008,38(8):1083-1088
The electrochemical promotion of catalysis (EPOC) of propene combustion was investigated using Pt sputtered thin film on an
O2− conductor, 8 mol% Y2O3-stabilized-ZrO2 (YSZ). In order to separate the influence of the thermal migration of the O2− oxide ions from the electrolyte to the catalyst surface and the impact of an electrical polarization on the catalytic activity,
several light-off experiments (cool down and heat up procedures) were successively performed under different polarizations,
i.e. OCV, +2 and −2 V. These experiments have clearly shown that the presence of O2− (thermally or electrochemically induced) inhibits the catalytic activity of the platinum for the propene deep oxidation.
These results demonstrate the importance to define a normalized rate enhancement ratio, ρ
n
, from a reference value of the catalytic rate corresponding to a Pt surface state free of O2− ions. 相似文献
995.
橡胶Mooney—Rivlin模型材料系数对轴向刚度影响分析 总被引:4,自引:0,他引:4
在橡胶小变形范围内,采用理论推断的方法,得到在相同硬度下橡胶Mooney—Rivlin模型材料系数由C2/C1决定的关系式。并采用ABAQUS有限元软件分析的方法,结合橡胶轴向刚度常规解,分析了C2/C1不同值对橡胶轴向刚度的影响进行,结果显示其影响呈现一定规律性。 相似文献
996.
介绍了windows环境下串行通信的核心,并以VC 为开发工具给出了I/O函数与API通信函数实现串行通信的具体编程步骤。 相似文献
997.
田葵 《河南机电高等专科学校学报》2004,12(6):89-90
《聊斋志异》中的《青娥》一篇充满了浓郁的童话色彩,贯穿主人公爱情生活的始终是纯洁执着的赤子情怀,爱情充满了青春的芬芳和清新的童趣,而波折和迂回中始终不离主人公的至情和至孝。 相似文献
998.
999.
Liew Jeffrey; Eisenberg Nancy; Losoya Sandra H.; Fabes Richard A.; Guthrie Ivanna K.; Murphy Bridget C. 《Canadian Metallurgical Quarterly》2003,17(4):584
Relations of heart rate and skin conductance reactions to mildly evocative empathy-inducing slides with socioemotional functioning were examined for 154 children (mean age = 9 years, 5 months). In addition, maternal expressivity was tested as a moderator of these relations. Parents and teachers rated children's socioemotional functioning, and a behavioral measure of children's regulation was obtained. Boys who exhibited higher skin conductance and higher heart rate to slides depicting negative emotions were better regulated, less emotionally intense, and better adjusted than their peers. Furthermore, boys' regulation and adjustment were positively related to such physiological responding to negative slides if maternal negative expressivity was relatively low or moderate, but not high. Fewer findings were obtained for girls or for positive slides. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
根据《中华人民共和国招标投标法》实施中的有关问题,探讨了采用工程量清单方式招投标的合理性和可行性,并给出了采用工程量清单法进行招投标的过程与步骤。 相似文献