全文获取类型
收费全文 | 11909篇 |
免费 | 1357篇 |
国内免费 | 921篇 |
专业分类
电工技术 | 1060篇 |
综合类 | 1034篇 |
化学工业 | 1366篇 |
金属工艺 | 630篇 |
机械仪表 | 890篇 |
建筑科学 | 765篇 |
矿业工程 | 341篇 |
能源动力 | 473篇 |
轻工业 | 1234篇 |
水利工程 | 454篇 |
石油天然气 | 279篇 |
武器工业 | 153篇 |
无线电 | 1243篇 |
一般工业技术 | 1181篇 |
冶金工业 | 1188篇 |
原子能技术 | 267篇 |
自动化技术 | 1629篇 |
出版年
2024年 | 63篇 |
2023年 | 171篇 |
2022年 | 393篇 |
2021年 | 525篇 |
2020年 | 352篇 |
2019年 | 300篇 |
2018年 | 263篇 |
2017年 | 344篇 |
2016年 | 318篇 |
2015年 | 454篇 |
2014年 | 590篇 |
2013年 | 717篇 |
2012年 | 829篇 |
2011年 | 944篇 |
2010年 | 879篇 |
2009年 | 943篇 |
2008年 | 894篇 |
2007年 | 864篇 |
2006年 | 749篇 |
2005年 | 692篇 |
2004年 | 485篇 |
2003年 | 326篇 |
2002年 | 281篇 |
2001年 | 281篇 |
2000年 | 210篇 |
1999年 | 108篇 |
1998年 | 215篇 |
1997年 | 145篇 |
1996年 | 100篇 |
1995年 | 66篇 |
1994年 | 76篇 |
1993年 | 54篇 |
1992年 | 34篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 27篇 |
1981年 | 28篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 53篇 |
1976年 | 102篇 |
1975年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
倪方 《南京工业职业技术学院学报》2010,10(1):25-26,29
长篇小说《第二十二条军规》是美国当代著名作家约瑟夫.海勒的最重要的作品之一。本文通过对该小说要旨和主要人物形象的分析,探讨了作者借助《第二十二条军规》描写人物周围世界的荒谬和社会对个人的压迫所导致的悲剧内涵。 相似文献
102.
基于自组织理论的居民出行方式结构模型 总被引:1,自引:0,他引:1
分析了自组织原理对居民出行方式选择系统的适用性。从协同学角度分析并提出了控制变量和序参量。对该系统相变过程进行了数学描述。以长春市为例构建了序参量模型,描述了长春市居民出行结构系统,建立了其序参量方程,为制定交通管理措施奠定了基础。 相似文献
103.
在我院体育教学实践中利用乒乓球多媒体课件的开发与应用研究,不单纯是一种技术的引进,更是一种全方位的教学改革,作为我院体育课程体系建设的组成部分,它将引发我院体育教学观念、教学设计、教学方法、教学互动、教学艺术等方面一系列的探索与思考。 相似文献
104.
针对传统的遗传规划方法收敛效率低、模型精度不高等缺点,将进化策略应用于模型参数的全局最优搜索,在遗传规划建模的基础上使用进化策略修正模型参数,以实现对模型结构和参数的同时优化,通过2种演化算法的结合提高建模精度,同时采用最优保持策略加速优化过程,改善算法的收敛效率.将该方法应用于某型船用汽轮机组的仿真建模中,通过和传统演化建模的对比,证明采用混合演化策略的建模方法具有更快的求解速度和更好的全局搜索能力. 相似文献
105.
Male, female and castrated rats, three wk of age, were fed a low-fat diet for 14 wk followed by high-fat diets (20% by weight)
for one wk containing graded levels of erucic acid from 1 to 50%, to evaluate the effect of short-term feeding and interaction
of male sex hormones on formation of heart lesions. Some rats within each group were returned to the low-fat diet for one
wk after the test period. For comparison, one group of three-wk-old male rats was fed the high fat 50% erucic acid diet for
15 wk. Erucic acid depressed growth rate and food consumption and increased cardiac lipidosis and triglycerides proportional
to the erucic acid content of the diet. There were no sex differences, and the effects disappeared once rats were returned
to the low-fat diet for one week. There was a significance (P<0.05) in the incidence of myocardial necrosis among male rats
fed increased levels of erucic acid for one week, but the response was not linear to the increase in dietary erucic acid.
Furthermore, the response was much less than in males fed the 50% erucic acid diet continually for 15 weeks. These results
suggest that the short-term model is not a suitable substitute for the long-term feeding trial to test the cardiopathogenicity
of a vegetable oil. The significantly lower incidence in myocardial lesions in female and castrated male rats compared with
male rats suggests involvement of sex hormones. However, the process appears to be long term, since changes in cardiac lipids
and their fatty acid pattern between sexes became evident after one wk on diet but was significant only after long-term feeding.
Deceased. 相似文献
106.
The precision and accuracy of the Iatroscan method was evaluated by comparing the results obtained with established phosphorus
and gas chromatographic techniques. A complete lipid class analysis of rat heart lipids was chosen in order to evaluate the
performance of the Iatroscan method for biological samples which contained both neutral lipids and phospholipids. A partial
scan and repeat development with chloroform/methanol/water (68.5∶29∶2.5) was introduced to achieve consistently good separations
of the phospholipids on the Chromarods in the Iatroscan method. The results showed that the precision of the Iatroscan method
for some lipid classes was comparable to that of phosphorus or gas chromatographic techniques, while for other lipid classes
it was lower. Compared to the data obtained using the phosphorus method, the Iatroscan data were generally similar, while
the gas chromatographic method generally gave lower values. These findings, together with the advantages of time required
for analysis, size of sample, and universality of detection, suggest that the Iatroscan is a valuable complementary method
for complex lipid analyses. 相似文献
107.
In this paper,we use elliptic nets to implement the optimized Ate pairings and optimal pairings on the Barreto-Naehrig curves with embedding degree 12.In order to do the arithmetic of elliptic curves over finite fields with elliptic nets,we first give some basic properties of elliptic nets associated to elliptic curves over finite fields and the expression of Miller function in terms of elliptic nets.Then we give formulae to compute some optimized pairings with elliptic nets,which is a new method to implement pairings.This method with elliptic nets has time complexity comparable to Miller’s algorithm and it can be optimized. 相似文献
108.
In this paper, the uplink and downlink performance of a two-tier heterogeneous network (HetNet) with range expansion (RE) is analyzed. Different from previous works, base stations (BSs) are modeled as a spatial Poisson point process. This model can not only capture the irregularity of the BS deployment but also lead to closed form expressions. With the analytical results, the impacts of several key parameters on the coverage and throughput performance are investigated. Our results justifies the effectiveness of RE and Pico deployment. Based on our analyses, certain attention should be made on the RE design to balance the uplink and downlink performance. Our analyses are corroborated by simulations and can thus serve as a flexible and quick guidance for system design without complicated and time-consuming system-level platform construction and simulation. 相似文献
109.
SEBS是一种用途广泛的新型弹性体材料,在常温下具有高弹性,高温下可直接加工成型。由于SEBS具有优异的耐臭氧、耐氧化、耐紫外线和耐候性能等,因此,应用范围广于普通SBS材料。但是,SEBS耐溶剂性和耐油性较差,常通过与其他材料共混改性来增强其加工性能。文章重点概述了苯乙烯-乙烯-丁烯-苯乙烯(SEBS)与聚丙烯(PP)共混材料的微观结构、相容性以及结构与性能的研究进展,介绍了近年国内外SEBS/PP共混改性的研究成果,包括填充油、无机材料、PPO、PC和PA6等改性体系,并比较了这些改性技术对SEBS/PP共混体系微观结构及性能的影响,近年内,SEBS/PP共混材料的理论研究和工程应用会有长足发展。 相似文献
110.
介绍了PVC干燥工段清洁生产的具体措施。更换了螺旋输送器、鼓风机及空气过滤器;回收利用了离心机母液水和蒸汽冷凝液;对振动筛、仓泵和自动包装机的除尘系统进行了单独的设计改造。通过改造,实现了干燥工段的清洁生产。 相似文献