全文获取类型
收费全文 | 34843篇 |
免费 | 2989篇 |
国内免费 | 1048篇 |
专业分类
电工技术 | 1143篇 |
技术理论 | 1篇 |
综合类 | 2084篇 |
化学工业 | 5231篇 |
金属工艺 | 1333篇 |
机械仪表 | 2892篇 |
建筑科学 | 1103篇 |
矿业工程 | 500篇 |
能源动力 | 653篇 |
轻工业 | 15463篇 |
水利工程 | 350篇 |
石油天然气 | 786篇 |
武器工业 | 157篇 |
无线电 | 1198篇 |
一般工业技术 | 3643篇 |
冶金工业 | 1018篇 |
原子能技术 | 349篇 |
自动化技术 | 976篇 |
出版年
2024年 | 347篇 |
2023年 | 833篇 |
2022年 | 1166篇 |
2021年 | 1622篇 |
2020年 | 1696篇 |
2019年 | 1468篇 |
2018年 | 1452篇 |
2017年 | 1412篇 |
2016年 | 1488篇 |
2015年 | 1441篇 |
2014年 | 2029篇 |
2013年 | 2685篇 |
2012年 | 2233篇 |
2011年 | 2181篇 |
2010年 | 1557篇 |
2009年 | 1534篇 |
2008年 | 1338篇 |
2007年 | 1813篇 |
2006年 | 1736篇 |
2005年 | 1387篇 |
2004年 | 1145篇 |
2003年 | 1065篇 |
2002年 | 878篇 |
2001年 | 684篇 |
2000年 | 613篇 |
1999年 | 492篇 |
1998年 | 438篇 |
1997年 | 400篇 |
1996年 | 291篇 |
1995年 | 254篇 |
1994年 | 209篇 |
1993年 | 166篇 |
1992年 | 173篇 |
1991年 | 100篇 |
1990年 | 93篇 |
1989年 | 64篇 |
1988年 | 54篇 |
1987年 | 62篇 |
1986年 | 49篇 |
1985年 | 58篇 |
1984年 | 49篇 |
1983年 | 14篇 |
1982年 | 36篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1966年 | 4篇 |
1964年 | 4篇 |
1959年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Tang Yuanyan 《Frontiers of Computer Science in China》2007,1(2):123-125
This paper gives an introduction and remarks on two review papers for Chinese character recognition. One review is made by
Chinese authors, another is from American scientists. They investigate Chinese character from different language environments;
they do the research from different points of view. Thus, a more comprehensive view on Chinese character recognition, which
is an important branch of pattern recognition, can be provided to the readers. Meantime, one article pays attention to online
process, and other paper deals with offline recognition, which complement each other.
The author is the Associate Editor-in-Chief of Frontiers of Computer Science in China 相似文献
102.
I. Egli L. Davidsson M.-A. Juillerat D. Barclay R. Hurrell 《Journal of food science》2003,68(5):1855-1859
Complementary foods based on cereals and legumes often contain high amounts of phytic acid, a potent inhibitor of mineral and trace element absorption. The possibility to degrade phytic acid during the production of complementary foods by using whole grain cereals as the phytase source was investigated. Whole grain rye, wheat, or buckwheat (10%) were added to cereal‐legume‐based complementary food mixtures, and phytic acid was shown to be completely degraded in a relatively short time (1.5 to 3 h) when incubated at optimal conditions for cereal phytase. The potential usefulness of the method for industrial production was demonstrated with a complementary food based on wheat and soybean. 相似文献
103.
104.
105.
J. Gajdoš Kljusurić 《Sadhana》2003,28(6):991-998
This work is an experimental study of the differential scanning calorimetry characterisation of polymer materials used in
food packaging materials, such as polypropylene (0.03 mm), polyethylene (0.1 and 0.03 mm), poly(D-(-)-Β-hydroxybutyrate) (powder),
two-layered polypropylene (0.064 mm), and two-layered polypropylene with poly-vinylidene-chloride (0.012/0.021). The polymer
stability was checked by simulation of conditions during food preparation in microwave ovens, sterilisation or rapid freezing.
The materials were tested in the temperature range from 40 to 200‡C at different scan rates from 2 to 30°C min−1 during heating or cooling. The enthalpies show a high correlation coefficient (0.964) with scan rate. All samples undergo
phase change in the temperature range from 107 to 173°C during heating and enthalpies are in the range from 31.8 to 71.1Jg−1. Upon subsequent cooling from 200°C, the temperature range of phase changes is shifted to lower temperatures from 86 to 102°C
with enthalpies ranging from 30.4 to 57.8 J g−1.
Experiments with exposure of polymers to microwave radiation and freezing prove that the phase change considering the temperature
range is very similar in all experiments. 相似文献
106.
Almond preferences were produced by giving rats a mixture of almond and sucrose (Experiments 1-4) or saccharin (Experiment 4). A subsequent extinction procedure consisted of either repeated 2-bottle almond versus water tests (Experiment 1) or repeated exposure to almond alone (Experiments 2-4). The main independent variable was whether access to food following a session was given immediately, 30 min later, or 120 min later. No effect of extinction was found in any experiment. An important finding was that varying the delay until food access had no detectable effect. It was concluded that inadvertent flavor-food associations do not maintain preference for the flavor under extinction conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
R. A. SMITH 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(10):901-907
The importance of the wheel–rail interface to the safe operation of railways is discussed. Some aspects of the history of rails and wheels are introduced. Several recent accidents involving the wheel–rail interface are described. The great importance of operating both vehicles and track as a system is emphasized, together with the necessity of maintaining both in good condition. 相似文献
108.
贵金属及其合金铆钉型复合电触点除了应考核其冷态复合强度之外,还必须增加在热态下复合强度的考核,只有这样才能满足用户在产际运行时对复合触点复合强度的要求。 相似文献
109.
对照IS0 9001质量管理体系标推的要求,结合石化销售企业质量管理工作中存在的主要问题,提出质量管理工作创新的建议。 相似文献
110.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献