全文获取类型
收费全文 | 28294篇 |
免费 | 2189篇 |
国内免费 | 891篇 |
专业分类
电工技术 | 203篇 |
技术理论 | 1篇 |
综合类 | 1881篇 |
化学工业 | 3267篇 |
金属工艺 | 1603篇 |
机械仪表 | 1026篇 |
建筑科学 | 1712篇 |
矿业工程 | 357篇 |
能源动力 | 208篇 |
轻工业 | 12784篇 |
水利工程 | 415篇 |
石油天然气 | 382篇 |
武器工业 | 86篇 |
无线电 | 874篇 |
一般工业技术 | 5469篇 |
冶金工业 | 543篇 |
原子能技术 | 97篇 |
自动化技术 | 466篇 |
出版年
2024年 | 243篇 |
2023年 | 649篇 |
2022年 | 875篇 |
2021年 | 1293篇 |
2020年 | 1244篇 |
2019年 | 1169篇 |
2018年 | 1069篇 |
2017年 | 1138篇 |
2016年 | 1118篇 |
2015年 | 1008篇 |
2014年 | 1492篇 |
2013年 | 1779篇 |
2012年 | 1842篇 |
2011年 | 1860篇 |
2010年 | 1288篇 |
2009年 | 1379篇 |
2008年 | 1050篇 |
2007年 | 1527篇 |
2006年 | 1561篇 |
2005年 | 1196篇 |
2004年 | 1044篇 |
2003年 | 936篇 |
2002年 | 799篇 |
2001年 | 575篇 |
2000年 | 569篇 |
1999年 | 475篇 |
1998年 | 349篇 |
1997年 | 285篇 |
1996年 | 256篇 |
1995年 | 211篇 |
1994年 | 187篇 |
1993年 | 183篇 |
1992年 | 156篇 |
1991年 | 120篇 |
1990年 | 94篇 |
1989年 | 89篇 |
1988年 | 46篇 |
1987年 | 43篇 |
1986年 | 36篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 14篇 |
1964年 | 4篇 |
1962年 | 2篇 |
1959年 | 5篇 |
1958年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
保健食品行业GMP的实施有利HACCP的应用推广。本文应用HACCP于传统保健食品西洋参口服液生产过程中,将生产及加工过程中危害因素降最低限度,以确保产品的质量与安全。 相似文献
52.
The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural‐fiber–plastic composites (NFPC) were assessed. We conducted short‐term tests in the laboratory and long‐term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X‐ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short‐ and the long‐term tests. The X‐ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006 相似文献
53.
防腐蚀施工工艺掌握的好坏,直接影响到工程投入生产后的使用寿命,为保证工程质量,以太钢不锈冷轧改造工程冷线防腐为例,对其常发生的质量通病进行认真分析,总结出一套行之有效的施工技术。 相似文献
54.
The technique of analytical pyrolysis has been used to characterize 40 similar mid-rank western Kentucky coals of widely differing ASTM Gieseler plasticity. Certain pyrolysis/g.c. variables were shown to correlate well with both ASTM Gieseler and isothermal plasticity. Highly plastic coals were shown to exhibit certain characteristic peaks in the 450 °C pyrogram which were absent in the pyrogram of the non-plastic coals. Two coals, representing the two extremes in plasticity, were selected for further study. After extraction with solvents such as DMF the characteristic peaks were absent in the 450 °C pyrogram of the extraction residue of the highly plastic coal. These peaks were also shown to decrease with increasing severity of air oxidation of the plastic coal. This technique appears to be a useful tool for the analysis of mid-rank plastic coals and supports the view that the substances contained in the bitumen fraction of these coals are involved in the development of the plastic state. 相似文献
55.
等径弯角挤压工艺(ECAEP)研究现状 总被引:3,自引:0,他引:3
等径弯角挤压是制备块状细晶材料的一种大塑性变形工艺,目前得到国内外高度重视.本文简要介绍了等径弯角挤压工艺的基本原理和变形特点,从理论上对其变形方式和机理进行了分析,并详细介绍了该工艺的应用领域。 相似文献
56.
Like any other domain of human activity, psychology has its fads and fashions. One consequence of fads is an overconcentration of resources on specific problems or approaches, which leaves other important problems or approaches (holes) underappreciated and understudied. This article is primarily about different factors (such as negativity bias, polarization of positions, focus on internal causes of behavior, dedication to a narrow view of what science is) that result in holes and about explorations of some of these holes that have interested the author. Psychologists should look more in the holes left behind by current enthusiasms. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
大塑性变形制备纳米结构金属 总被引:5,自引:0,他引:5
细化晶粒是改善材料性能的有效手段,传统的压力加工技术(如轧制、挤压、拉拔和锻造等)可以细化晶粒(微米量级)。纳米结构金属由于具有很小的晶粒尺寸(20-500nm)和独特的缺陷结构,从而表现出优异的物理—力学性能。大塑性变形(SPD)具有将铸态粗晶金属的晶粒细化到纳米量级的巨大潜力,近年来已引起人们的极大关注。介绍了4种大塑性变形制备纳米结构金属的方法、原理、变形特点及应用,分析了纳米结构金属的强度和超塑性变形特征,以及当前研究中存在的主要问题,并对大塑性变形技术的应用前景进行了展望。 相似文献
58.
Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 104 cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 105 cfu/g in 10 of the 15 samples. Escherichia coli exceeding 105 cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable. 相似文献
59.
橡塑共混热塑性弹性体的形态结构与性能 总被引:2,自引:0,他引:2
综述了影响共混热塑性弹性体的形态结构与性能的主要因素。 相似文献
60.
用透射电镜观察了30CrMnSiNi2A钢等温的微观组织,疲劳裂纹扩展行为、裂纹尖端塑性区和位错结构,结果表明,等温状态组织由马氏体和贝氏体组成。在一个奥氏体晶粒内一般存在四个板条领域、裂纹尖端的塑性区内存在主位错带,疲劳断裂的基本组织单元为板条晶或板条束。裂纹遇到板条束界时方向发生较大偏斜。 相似文献