全文获取类型
收费全文 | 122400篇 |
免费 | 5003篇 |
国内免费 | 2527篇 |
专业分类
电工技术 | 3562篇 |
技术理论 | 2篇 |
综合类 | 5066篇 |
化学工业 | 17610篇 |
金属工艺 | 6970篇 |
机械仪表 | 5597篇 |
建筑科学 | 5829篇 |
矿业工程 | 1623篇 |
能源动力 | 2152篇 |
轻工业 | 7220篇 |
水利工程 | 1993篇 |
石油天然气 | 2036篇 |
武器工业 | 361篇 |
无线电 | 13839篇 |
一般工业技术 | 20696篇 |
冶金工业 | 4115篇 |
原子能技术 | 745篇 |
自动化技术 | 30514篇 |
出版年
2024年 | 235篇 |
2023年 | 844篇 |
2022年 | 1611篇 |
2021年 | 2131篇 |
2020年 | 1570篇 |
2019年 | 1278篇 |
2018年 | 15641篇 |
2017年 | 14727篇 |
2016年 | 11267篇 |
2015年 | 2353篇 |
2014年 | 2500篇 |
2013年 | 2679篇 |
2012年 | 5845篇 |
2011年 | 12118篇 |
2010年 | 10824篇 |
2009年 | 7944篇 |
2008年 | 8939篇 |
2007年 | 9824篇 |
2006年 | 2035篇 |
2005年 | 2802篇 |
2004年 | 2221篇 |
2003年 | 2138篇 |
2002年 | 1535篇 |
2001年 | 986篇 |
2000年 | 956篇 |
1999年 | 818篇 |
1998年 | 581篇 |
1997年 | 533篇 |
1996年 | 546篇 |
1995年 | 408篇 |
1994年 | 344篇 |
1993年 | 229篇 |
1992年 | 182篇 |
1991年 | 143篇 |
1990年 | 87篇 |
1989年 | 90篇 |
1988年 | 77篇 |
1987年 | 45篇 |
1986年 | 37篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1962年 | 64篇 |
1961年 | 57篇 |
1960年 | 46篇 |
1959年 | 38篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
针对多角度下车辆出现一定的尺度变化和形变导致很难被准确识别的问题,提出基于多尺度双线性卷积神经网络(MS-B-CNN)的车型精细识别模型。首先,对双线性卷积神经网络(B-CNN)算法进行改进,提出MS-B-CNN算法对不同卷积层的特征进行了多尺度融合,以提高特征表达能力;此外,还采用基于中心损失函数与Softmax损失函数联合学习的策略,在Softmax损失函数基础上分别对训练集每个类别在特征空间维护一个类中心,在训练过程中新增加样本时,网络会约束样本的分类中心距离,以提高多角度情况下的车型识别的能力。实验结果显示,该车型识别模型在CompCars数据集上的正确率达到了93.63%,验证了模型在多角度情况下的准确性和鲁棒性。 相似文献
4.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
5.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
6.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
7.
8.
9.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
10.
研制了用于远程激光脉冲测距机的板条激光器。使用半导体泵浦的MOPA激光结构实现了大于250 mJ的脉冲激光输出,输出脉冲宽度为12.83 ns,最终输出激光光束束散角为0.18 mrad。该激光测照器可应用于远程激光测距。对激光测距机的测距与照射能力进行了理论计算与分析。理论分析表明,应用于机载平台时,该激光测照器能够实现50 km距离的激光测距。该型激光测距机具有测距距离远,重量轻,结构紧凑等特点,具有广泛的应用前景。 相似文献