全文获取类型
收费全文 | 9187篇 |
免费 | 908篇 |
国内免费 | 569篇 |
专业分类
电工技术 | 447篇 |
综合类 | 979篇 |
化学工业 | 707篇 |
金属工艺 | 296篇 |
机械仪表 | 641篇 |
建筑科学 | 814篇 |
矿业工程 | 620篇 |
能源动力 | 499篇 |
轻工业 | 1166篇 |
水利工程 | 349篇 |
石油天然气 | 234篇 |
武器工业 | 88篇 |
无线电 | 877篇 |
一般工业技术 | 1793篇 |
冶金工业 | 404篇 |
原子能技术 | 223篇 |
自动化技术 | 527篇 |
出版年
2024年 | 19篇 |
2023年 | 92篇 |
2022年 | 187篇 |
2021年 | 242篇 |
2020年 | 276篇 |
2019年 | 222篇 |
2018年 | 228篇 |
2017年 | 240篇 |
2016年 | 338篇 |
2015年 | 324篇 |
2014年 | 459篇 |
2013年 | 561篇 |
2012年 | 648篇 |
2011年 | 739篇 |
2010年 | 556篇 |
2009年 | 588篇 |
2008年 | 525篇 |
2007年 | 655篇 |
2006年 | 625篇 |
2005年 | 521篇 |
2004年 | 402篇 |
2003年 | 369篇 |
2002年 | 288篇 |
2001年 | 277篇 |
2000年 | 216篇 |
1999年 | 181篇 |
1998年 | 177篇 |
1997年 | 132篇 |
1996年 | 107篇 |
1995年 | 91篇 |
1994年 | 76篇 |
1993年 | 54篇 |
1992年 | 56篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 25篇 |
1988年 | 20篇 |
1987年 | 25篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1959年 | 6篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
对Inconel 690传热管材进行钨极气体保护焊(GTAW)对接焊,采用拉伸试验机、压扁试验机和光学显微镜测试和分析传热管焊接接头,同时利用ANSYS软件开展焊接接头在设计工况失压时的一次应力强度校核。研究结果表明:焊缝中心为树枝胞状晶,熔合线附近为粗大柱状晶。室温时接头的平均抗拉强度为619 MPa,平均屈服强度为292 MPa,350℃时接头平均抗拉强度为475 MPa,平均屈服强度为206 MPa,拉伸接头断裂从熔合区开始贯穿整个焊缝组织,呈塑性断裂。压扁试验和反向压扁试验结果表明管接头完好。通过ANSYS分析可知,设计工况下传热管接头350℃许用应力强度150 MPa限值可满足其一次应力强度要求,且裕量较大。 相似文献
2.
某微细粒嵌布磁铁矿选矿工艺研究 总被引:1,自引:0,他引:1
针对某微细粒磁铁矿进行了全磁选流程和磁选-反浮选流程对比试验研究。结果表明,在最终磨矿细度相当的情况下,2种工艺流程都获得了产率48%左右、TFe品位66%左右、回收率80%左右的铁精矿指标,而采用磁选-反浮选流程的第三段磨矿量比全磁选流程减少了2/3。磁选-反浮选流程具有显著的节能降耗优势。 相似文献
3.
《Ceramics International》2022,48(3):3051-3058
Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba3-xSrxLu4O9 (B3-xSxLO):Er3+/Yb3+ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb3+ to Er3+ and regulating the local lattice environment, up-conversion luminescence of Er3+ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of 2H11/2/4S3/2, FIR based on non-thermally coupled system of 2H11/2/4F9/2 and fluorescence lifetime of 4S3/2 state of Er3+, was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B3-xSxLO:Er3+/Yb3+ for thermometry. 相似文献
4.
5G蜂窝网络发展迅猛,其覆盖面积将逐渐增大,因此使用5G蜂窝网络进行定位是有研究潜力的研究方向。本文提出一种新的深度学习技术来实现高效、高精度和低占用的定位,以代替传统指纹定位过程中繁重的指纹库生成以及距离计算。该方法建立了一个特殊的卷积神经网络,并根据5G天线信号的接收信号强度指示、相位和到达角等特征量,选择合适的输入数据格式构造样本组建训练集,对该卷积神经网络进行训练。训练得到的卷积神经网络可以替代指纹定位中的庞大指纹库,非常有利于直接在5G移动设备端实现定位。虽然卷积神经网络在训练过程中需要大量时间,但在训练完毕后直接进行分类定位的速度非常快,可以保障定位实现的实时性。本文所实现的卷积神经网络权重与偏置所占内存不到0.5 MB,且能够在实际应用环境中以95%的定位准确率以及0.1 m的平均定位精度实现高精度定位。 相似文献
5.
《岩石力学与岩土工程学报(英文版)》2022,14(5):1421-1432
Prediction of mode I fracture toughness (KIC) of rock is of significant importance in rock engineering analyses. In this study, linear multiple regression (LMR) and gene expression programming (GEP) methods were used to provide a reliable relationship to determine mode I fracture toughness of rock. The presented model was developed based on 60 datasets taken from the previous literature. To predict fracture parameters, three mechanical parameters of rock mass including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and elastic modulus (E) have been selected as the input parameters. A cluster of data was collected and divided into two random groups of training and testing datasets. Then, different statistical linear and artificial intelligence based nonlinear analyses were conducted on the training data to provide a reliable prediction model of KIC. These two predictive methods were then evaluated based on the testing data. To evaluate the efficiency of the proposed models for predicting the mode I fracture toughness of rock, various statistical indices including coefficient of determination (R2), root mean square error (RMSE), and mean absolute error (MAE) were utilized herein. In the case of testing datasets, the values of R2, RMSE, and MAE for the GEP model were 0.87, 0.188, and 0.156, respectively, while they were 0.74, 0.473, and 0.223, respectively, for the LMR model. The results indicated that the selected GEP model delivered superior performance with a higher R2 value and lower errors. 相似文献
6.
7.
8.
《Advanced Powder Technology》2021,32(10):3540-3549
A colorimetric assay based on the oriented TA-AuNPs-PEG-FITC for rapid and sensitive PABA detection was proposed. Initially, the negatively charged TA modified on the surface of AuNPs enabled rapid binding to PABA due to the electrostatic interaction and hydrogen bond, resulting in a visible color change. However, particles were aggregated in a non-oriented way, leading to an unstable testing system which failed to realize the accurate quantification. Thus, the asymmetrically functionalized TA-AuNPs-PEG-FITC were prepared, in which the stabilizer agent of HS-PEG-FITC was attached to the specific sites on the surface of TA-AuNPs. Such a way of modification resulted in an oriented aggregation manner, the addition of PABA induced the formation of oligomers. Moreover, the introduction of FITC group acted as fluorescent marker, providing a simple, fast and quantitative method for characterization of PEG chain. The molar ratio between TA-AuNPs and modified PEG-FITC was further determined. A linear regression was established in a wide range from 10 μM to 1 mM with the LOD of 6.9 μM. Finally, the sensor was successfully applied in the health food. This was the first example in which TA-AuNPs-PEG-FITC were fabricated for colorimetric detection of PABA, and an indirect method based on fluorescence marker was well used to quantify the content of PEG chain. 相似文献
9.
由于低温鸡肉制品具有较好的感官品质,能够保留鸡肉原有的营养,成为我国肉制品发展的一个趋势。低温鸡肉制品水分含量和pH值较高,在加工和贮藏过程中极易受到食源性致病菌的污染,影响产品的质量安全,甚至引发食源性疾病,因此采用合适的杀菌技术来解决致病菌的污染是低温鸡肉制品贮藏保鲜需要解决的关键问题。由于热杀菌技术不适合用于低温鸡肉制品的灭菌,非热杀菌技术的应用就显得尤其重要。目前,应用在低温鸡肉制品加工中的非热杀菌技术主要包括超高压、辐照、超声、低温等离子体、脉冲紫外线、脉冲电场和脉冲微波。本文主要综述以上7 种非热杀菌技术的杀菌机制以及在不同低温鸡肉制品加工应用时对致病菌的控制效果,为未来非热杀菌技术在低温肉制品加工中的应用提供参考。 相似文献
10.