全文获取类型
收费全文 | 88537篇 |
免费 | 16919篇 |
国内免费 | 11157篇 |
专业分类
电工技术 | 9129篇 |
技术理论 | 1篇 |
综合类 | 10982篇 |
化学工业 | 2635篇 |
金属工艺 | 1761篇 |
机械仪表 | 6768篇 |
建筑科学 | 1706篇 |
矿业工程 | 1237篇 |
能源动力 | 1598篇 |
轻工业 | 1141篇 |
水利工程 | 1314篇 |
石油天然气 | 1239篇 |
武器工业 | 1488篇 |
无线电 | 16015篇 |
一般工业技术 | 5821篇 |
冶金工业 | 2254篇 |
原子能技术 | 348篇 |
自动化技术 | 51176篇 |
出版年
2024年 | 258篇 |
2023年 | 1566篇 |
2022年 | 3196篇 |
2021年 | 3503篇 |
2020年 | 3733篇 |
2019年 | 3046篇 |
2018年 | 2939篇 |
2017年 | 3482篇 |
2016年 | 4032篇 |
2015年 | 4703篇 |
2014年 | 6237篇 |
2013年 | 5907篇 |
2012年 | 7385篇 |
2011年 | 7841篇 |
2010年 | 6408篇 |
2009年 | 6609篇 |
2008年 | 6926篇 |
2007年 | 7512篇 |
2006年 | 6015篇 |
2005年 | 4963篇 |
2004年 | 4000篇 |
2003年 | 3333篇 |
2002年 | 2574篇 |
2001年 | 1956篇 |
2000年 | 1651篇 |
1999年 | 1341篇 |
1998年 | 1097篇 |
1997年 | 863篇 |
1996年 | 652篇 |
1995年 | 507篇 |
1994年 | 421篇 |
1993年 | 346篇 |
1992年 | 316篇 |
1991年 | 148篇 |
1990年 | 191篇 |
1989年 | 153篇 |
1988年 | 109篇 |
1987年 | 61篇 |
1986年 | 61篇 |
1985年 | 70篇 |
1984年 | 60篇 |
1983年 | 68篇 |
1982年 | 64篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 31篇 |
1978年 | 32篇 |
1977年 | 34篇 |
1976年 | 27篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Daisuke Yamanaka Suzuka Kurita Yuka Hanayama Yoshiyuki Adachi 《International journal of molecular sciences》2021,22(4)
β-Glucan is widely distributed in various plants and microorganisms and is composed of β-1,3-linked d-glucose units. It may have a branched short or long side chain of glucose units with β-1,6- or β-1,4-linkage. Numerous studies have investigated different β-glucans and revealed their bioactivities. To understand the structure-function relationship of β-glucan, we constructed a split-luciferase complementation assay for the structural analysis of long-chain β-1,6-branched β-1,3-glucan. The N- and C-terminal fragments of luciferase from deep-sea shrimp were fused to insect-derived β-1,3-glucan recognition protein and fungal endo-β-1,6-glucanase (Neg1)-derived β-1,6-glucan recognition protein, respectively. In this approach, two β-glucan recognition proteins bound to β-glucan molecules come into close proximity, resulting in the assembly of the full-length reporter enzyme and induction of transient luciferase activity, indicative of the structure of β-glucan. To test the applicability of this assay, β-glucan and two β-glucan recognition proteins were mixed, resulting in an increase in the luminescence intensity in a β-1,3-glucan with a long polymer of β-1,6-glucan in a dose-dependent manner. This simple test also allows the monitoring of real-time changes in the side chain structure and serves as a convenient method to distinguish between β-1,3-glucan and long-chain β-1,6-branched β-1,3-glucan in various soluble and insoluble β-glucans. 相似文献
2.
3.
4.
5.
基于GA-BP的汽车风振噪声声品质预测模型 总被引:1,自引:1,他引:0
目前对于汽车风振噪声的优化研究主要以声压级(Sound pressure level,SPL)作为单一评价指标,既不能全面反映噪声的物理属性,也无法考虑人耳对噪声的主观认知过程。为准确评价风振噪声,引入声品质,运用大涡模拟(Large eddy simulation,LES)对风振噪声进行数值仿真,根据实车道路试验判断仿真的准确性;对仿真结果进行声品质客观评价与主观评价,综合声品质客观评价参数与声品质主观评价试验结果建立BP神经网络预测模型;利用遗传算法(Genetic algorithm,GA),进一步对BP神经网络的结构参数进行优化,建立GA-BP声品质预测模型。研究结果表明,GA-BP声品质预测模型在训练速度和预测精度上都优于BP神经网络预测模型。预测模型基于声品质主客观评价结果,其预测值可以代替传统的声压级评价指标,为风振噪声提供更为准确合理的评价。 相似文献
6.
7.
8.
高效率地使用工程车辆是工程项目管理中节约成本的有效方法,无人监管环境下工程车辆的工况识别,是实现工程车辆高效率使用的有效手段。目前以GPS等技术为核心的车辆智能管理系统未对工程车辆进行工况识别,提出一种基于GRU循环神经网络的工程车辆工况识别方法,通过对工程车辆在不同工况下产生的音频信号进行分析,从中提取Mel倒谱系数作为主要特征,构建GRU循环神经网络模型进行训练和识别。实验结果表明,该方法可以实现对工程车辆工况的有效识别。 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(7):4814-4826
This paper develops a novel approach to the parameterisation of high temperature exchange membrane fuel cells (HTPEMFC) with limited and non-invasive measurements. The proposed method allows an effective identification of electrochemical parameters for three-dimensional fuel cell models by combining computational simulation tools and genetic algorithms. To avoid each evaluation undertaken by the optimisation method involving a complete computational simulation of the 3D model, a strategy has been designed that, thanks to an iterative process, makes it possible to decouple the fluid dynamic resolution from the electrochemistry one.Two electrochemical models have been incorporated into these tools to describe the behaviour of the catalyst layer, Butler-Volmer and spherical aggregate. For each one, a case study has been carried out to validate the results by comparing them with empirical data in the first model and with data generated by numerical simulation in the second. Results show that, from a set of measured operating conditions, it is possible to identify a unique set of electrochemical parameters that fits the 3D model to the target polarisation curve. The extension of this framework can be used to systematically estimate any model parameter in order to reduce the uncertainty in 3D simulation predictions. 相似文献
10.
Under the circumstance of perceptual consumption, it is still challenging to grasp consumer's emotions and demands due to the large search space, diversified preferences, and easy fatigue of consumers. To reduce user fatigue and enlarge search space, a novel method was presented to design and optimize the pattern of yarn-dyed plaid fabric using the isolation niche genetic algorithm and rough set theory. Each pattern was encoded as a chromosome based on the real number code. The population was initialized and evolved using INGA to maintain the diversity. The rough set theory was adopted as the fitness function of isolation niche genetic algorithm to extract the consumer's demands. After multiple evolutions, a large set of practical patterns of the yarn-dyed plaid fabric are obtained. Experiments were carried out by 24 testers of different ages and genders. The results prove that the proposed method based on the isolation niche genetic algorithm and rough set theory is feasible and effective, supplying references to the designer. 相似文献