全文获取类型
收费全文 | 261205篇 |
免费 | 20070篇 |
国内免费 | 13232篇 |
专业分类
电工技术 | 16733篇 |
技术理论 | 51篇 |
综合类 | 36234篇 |
化学工业 | 28418篇 |
金属工艺 | 9716篇 |
机械仪表 | 14022篇 |
建筑科学 | 37470篇 |
矿业工程 | 14865篇 |
能源动力 | 7859篇 |
轻工业 | 14541篇 |
水利工程 | 14006篇 |
石油天然气 | 11124篇 |
武器工业 | 2494篇 |
无线电 | 16793篇 |
一般工业技术 | 18245篇 |
冶金工业 | 15524篇 |
原子能技术 | 2601篇 |
自动化技术 | 33811篇 |
出版年
2024年 | 810篇 |
2023年 | 2479篇 |
2022年 | 4760篇 |
2021年 | 5716篇 |
2020年 | 6070篇 |
2019年 | 5126篇 |
2018年 | 4812篇 |
2017年 | 5878篇 |
2016年 | 6959篇 |
2015年 | 7796篇 |
2014年 | 14451篇 |
2013年 | 13118篇 |
2012年 | 17192篇 |
2011年 | 18274篇 |
2010年 | 14578篇 |
2009年 | 15218篇 |
2008年 | 14224篇 |
2007年 | 18724篇 |
2006年 | 17766篇 |
2005年 | 15568篇 |
2004年 | 13263篇 |
2003年 | 11958篇 |
2002年 | 9869篇 |
2001年 | 8347篇 |
2000年 | 7043篇 |
1999年 | 5747篇 |
1998年 | 4347篇 |
1997年 | 3819篇 |
1996年 | 3546篇 |
1995年 | 2996篇 |
1994年 | 2674篇 |
1993年 | 2003篇 |
1992年 | 1779篇 |
1991年 | 1325篇 |
1990年 | 1156篇 |
1989年 | 1021篇 |
1988年 | 819篇 |
1987年 | 565篇 |
1986年 | 424篇 |
1985年 | 353篇 |
1984年 | 336篇 |
1983年 | 242篇 |
1982年 | 215篇 |
1981年 | 165篇 |
1980年 | 130篇 |
1979年 | 110篇 |
1978年 | 62篇 |
1977年 | 72篇 |
1976年 | 55篇 |
1975年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
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
222.
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
223.
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
224.
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
225.
O. L. Perevozchikova V. G. Tul'chinskii A. V. Kharchenko 《Cybernetics and Systems Analysis》2003,39(4):501-508
A statistical learning model is considered within the framework of the theory of uniform convergence of frequencies of errors in the case where the convergence is violated as a result of increasing the informativeness of training examples. Drawbacks of nonconstructive refinements of Vapnik-Chervonenkis estimates based on an assumption on the distribution law of violations are shown. A new approach to obtaining constructive estimates for mass data sets is proposed. 相似文献
226.
We say that a distribution over {0,1}n is (ε,k)-wise independent if its restriction to every k coordinates results in a distribution that is ε-close to the uniform distribution. A natural question regarding (ε,k)-wise independent distributions is how close they are to some k-wise independent distribution. We show that there exist (ε,k)-wise independent distributions whose statistical distance is at least nO(k)·ε from any k-wise independent distribution. In addition, we show that for any (ε,k)-wise independent distribution there exists some k-wise independent distribution, whose statistical distance is nO(k)·ε. 相似文献
227.
针对贵溪冶炼厂建安公司新紫杂铜打包机不良状况及存在的问题进行了改进 ,对整台机组的总配电箱、液压管网、设备的保护接地及建筑主体框架也进行接地。 相似文献
228.
229.
介绍了纳米金属氧化物的制作技术,纳米粉末团聚问题的解决以及纳米金属氧化物用于涂料中所引起的神奇功能。同时综述了国内外开发纳米涂料的现状。 相似文献
230.
Psychologists are often asked to testify in court. However, concerns have been expressed in both the legal and psychological literatures about the quality of these services. This article presents survey results comparing the practice patterns of generally licensed psychologists with those of specialist forensic diplomates in providing risk evaluations. Results suggest that general clinicians frequently perform these evaluations, but forensic diplomates use more modern risk instruments, are more aware of the scientific literature, and provide the court with more information about the scientific basis of their testimony. The implication of these results for legal professionals, psychologist training, and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献