全文获取类型
收费全文 | 28346篇 |
免费 | 3100篇 |
国内免费 | 1688篇 |
专业分类
电工技术 | 3908篇 |
综合类 | 3256篇 |
化学工业 | 511篇 |
金属工艺 | 468篇 |
机械仪表 | 1860篇 |
建筑科学 | 1286篇 |
矿业工程 | 1418篇 |
能源动力 | 249篇 |
轻工业 | 631篇 |
水利工程 | 455篇 |
石油天然气 | 886篇 |
武器工业 | 324篇 |
无线电 | 8433篇 |
一般工业技术 | 1727篇 |
冶金工业 | 335篇 |
原子能技术 | 236篇 |
自动化技术 | 7151篇 |
出版年
2024年 | 126篇 |
2023年 | 366篇 |
2022年 | 587篇 |
2021年 | 697篇 |
2020年 | 729篇 |
2019年 | 479篇 |
2018年 | 411篇 |
2017年 | 642篇 |
2016年 | 771篇 |
2015年 | 1008篇 |
2014年 | 1714篇 |
2013年 | 1557篇 |
2012年 | 2142篇 |
2011年 | 2356篇 |
2010年 | 1850篇 |
2009年 | 1970篇 |
2008年 | 2045篇 |
2007年 | 2382篇 |
2006年 | 2211篇 |
2005年 | 1928篇 |
2004年 | 1442篇 |
2003年 | 1261篇 |
2002年 | 901篇 |
2001年 | 726篇 |
2000年 | 573篇 |
1999年 | 434篇 |
1998年 | 281篇 |
1997年 | 241篇 |
1996年 | 231篇 |
1995年 | 231篇 |
1994年 | 175篇 |
1993年 | 141篇 |
1992年 | 97篇 |
1991年 | 86篇 |
1990年 | 63篇 |
1989年 | 64篇 |
1988年 | 46篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1959年 | 5篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
针对煤矿井下高瓦斯软煤顺层长钻孔排渣困难、成孔率低、施工困难等问题,通过数值模拟实验研究了井下深部软煤体变形破坏特征,分析了顺层长钻孔孔周松软煤体变形特征及应力变化,以揭示顺层长钻孔孔周松软煤体变形产渣规律。研究表明:深部高瓦斯软煤顺层钻孔孔周煤体的应力平衡临界条件破坏后将发生大体积突然垮落;钻孔水平最大变形位移为1.22mm,垂直方向最大变形位移为10.7mm;径向孔周煤体垂向变形呈现逐渐减小趋势,且垂向变形明显大于钻孔水平变形。在水平方向上,钻孔孔周煤体应力分布呈现先增大再逐渐减小的变化规律,径向距离对水平应力分布的影响逐渐减小;随着径向距离的增加,钻孔孔周煤体应力分布逐渐降低,钻孔孔壁处煤体的应力出现最大值,且垂直方向处应力值最大。 相似文献
2.
In this paper, a new inverse identification method of constitutive parameters is developed from full kinematic and thermal field measurements. It consists in reconstructing the heat source field from two different approaches by using the heat diffusion equation. The first one requires the temperature field measurement and the value of the thermophysical parameters. The second one is based on the kinematic field measurement and the choice of a thermo-hyperelastic model that contains the parameters to be identified. The identification is carried out at the local scale, ie, at any point of the heat source field, without using the boundary conditions. In the present work, the method is applied to the challenging case of hyperelasticity from a heterogeneous test. Due to large deformations undergone by the rubber specimen tested, a motion compensation technique is developed to plot the kinematic and the thermal fields at the same points before reconstructing the heterogeneous heat source field. In the present case, the constitutive parameter of the Neo-Hookean model has been identified, and its distribution has been characterized with respect to the strain state at the surface of a cross-shaped specimen. 相似文献
3.
现今国内的数字集群网络发展存在局限性、差异性,还远没有达到“网”状分布的程度,因此,共网数字集群发展空间巨大、前景广阔。通过列举共网数字集群系统在龙嘉国际机场和长春雷锋车队的成功应用案例,探讨了我国共网数字集群系统应用的可行性和必要性。 相似文献
4.
Stefanie Vanbecelaere Katrien Van den Berghe Frederik Cornillie Delphine Sasanguie Bert Reynvoet Fien Depaepe 《Journal of Computer Assisted Learning》2020,36(4):502-513
For the training of academic skills, digital educational games with integrated adaptivity are promising. Adaptive games are considered superior to non-adaptive games, because they constantly assess children's performance, and accordingly adapt the difficulty of the tasks corresponding to the children's individual level. However, empirical evidence with regard to the effectivity of adaptive compared to non-adaptive games is limited. A study was conducted with 191 children from the third year of Kinder garten who were enrolled in one of three conditions, that is, playing an adaptive version of the reading game (RG), a non-adaptive version of the RG or training with pen-and-paper exercises. In all three conditions, children trained emergent reading (phonological awareness and letter knowledge) once a week for 30 min over a period of 5 weeks. Children's performance on cognitive (phonological awareness, letter knowledge, reading fluency) and non-cognitive (motivation, self-concept) factors was assessed. Results revealed a significant improvement in phonological awareness and letter knowledge in all conditions. However, no differences between the conditions were observed with respect to children's improvement on phonological awareness and letter knowledge or on their post-test scores for reading fluency. With regard to motivation and self-concept, again, no differences in these non-cognitive factors were observed across conditions. 相似文献
5.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献
6.
7.
自2002年起,我国开始出现电视民生新闻,并得到观众的广泛喜爱,但在整个发展过程当中电视新闻存在一些问题有待解决,探讨电视民生新闻的现状及发展趋势,对其中存在的问题提出解决方案。 相似文献
8.
Maria Grazia Basanisi Gianfranco La Bella Gaia Nobili Rosa Coppola Annita Maria Damato Maria Assunta Cafiero Giovanna La Salandra 《International Journal of Food Science & Technology》2020,55(3):1145-1150
The authenticity and traceability of meat products are issues of primary importance to ensure food safety. Unfortunately, food adulteration (e.g. the addition of inexpensive cuts to minced meat products) and mislabelling (e.g. the inclusion of meat from species other than those declared) happens frequently worldwide. The aim of this study was to apply a droplet digital PCR assay for the detection and quantification (copies μL−1) of the beef, pork, horse, sheep, chicken and turkey in meat products. The analysis conducted on commercial meat showed the presence of traces of DNA from other animal species than those declared. We show that the method is highly sensitive, specific and accurate (accuracy = 100%). This method could be adopted by competent food safety authorities to verify compliance with the labelling of meat products and to ensure quality and safety throughout the meat supply chain, from primary production to consumption. 相似文献
9.
10.
论文提出利用用户提供的个性化信息来随机产生关联大素数,保证了素数选取的随机化、个性化,提高了RSA算法的安全性。 相似文献