全文获取类型
收费全文 | 11035篇 |
免费 | 1377篇 |
国内免费 | 901篇 |
专业分类
电工技术 | 468篇 |
综合类 | 720篇 |
化学工业 | 681篇 |
金属工艺 | 1038篇 |
机械仪表 | 432篇 |
建筑科学 | 266篇 |
矿业工程 | 90篇 |
能源动力 | 72篇 |
轻工业 | 209篇 |
水利工程 | 31篇 |
石油天然气 | 107篇 |
武器工业 | 85篇 |
无线电 | 1767篇 |
一般工业技术 | 1524篇 |
冶金工业 | 2335篇 |
原子能技术 | 58篇 |
自动化技术 | 3430篇 |
出版年
2024年 | 39篇 |
2023年 | 255篇 |
2022年 | 371篇 |
2021年 | 465篇 |
2020年 | 391篇 |
2019年 | 277篇 |
2018年 | 232篇 |
2017年 | 303篇 |
2016年 | 305篇 |
2015年 | 344篇 |
2014年 | 497篇 |
2013年 | 549篇 |
2012年 | 622篇 |
2011年 | 956篇 |
2010年 | 692篇 |
2009年 | 736篇 |
2008年 | 749篇 |
2007年 | 758篇 |
2006年 | 685篇 |
2005年 | 689篇 |
2004年 | 621篇 |
2003年 | 494篇 |
2002年 | 435篇 |
2001年 | 357篇 |
2000年 | 212篇 |
1999年 | 168篇 |
1998年 | 149篇 |
1997年 | 141篇 |
1996年 | 127篇 |
1995年 | 124篇 |
1994年 | 102篇 |
1993年 | 88篇 |
1992年 | 66篇 |
1991年 | 38篇 |
1990年 | 50篇 |
1989年 | 41篇 |
1988年 | 38篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1963年 | 5篇 |
1961年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Niken Indrati Punnanee Sumpavapol Rajnibhas Sukeaw Samakradhamrongthai Natthaporn Phonsatta Patcha Poungsombat Sakda Khoomrung Atikorn Panya 《International Journal of Food Science & Technology》2022,57(6):3760-3770
Sweet pickled mango named Ma-Muang Bao Chae-Im is a traditional preserved mango from Hat Yai, Thailand. This study investigated (I) volatile and non-volatile compound profiles of commercial Ma-Muang Bao Chae-Im and (II) their relationship to consumer preference. Untargeted metabolomics profiling was performed by gas chromatography-mass quadrupole-time of flight analysis. There were 117 volatile and 44 non-volatile compounds annotated in six commercial brands of Ma-Muang Bao Chae-Im. Furthermore, 46 volatile and 19 non-volatile compounds’ discriminant markers were found by Partial least square discriminant analysis. Among those markers, sorbic and benzoic acid were observed in several brands; moreover, the combination of both compounds altered the volatile profile, especially the ester group. Partial least square regression revealed that overall consumer liking is correlated to 1-heptanol; 1-octanol; acetoin; acetic acid, 2-phenylethyl ester; D-manitol; terpenes and terpenoids, while firmness to sucrose and L-(-)-sorbofuranose. On the other hand, most ester compounds were not related to consumer preference. 相似文献
2.
At present, the synthesis of body temperature triggering shape memory polymers usually requires elaborate structural design, which limits their wide application. Herein, starting from bio-based Eucommia ulmoides gum (EUG), a series of EUG/silica hybrids (ESHs) are prepared through a facile one-pot process, in which EUG is epoxied and then self-crosslinked with SiO2 by epoxy ring-open reaction. Varying the amount of H2O2, the shape memory transition temperature (Ttrans) of ESHs is adjusted to 47.4–36.6 ℃, which is close to human body temperature (37 ℃). Among them, ESH-17 exhibited the best body temperature triggering shape memory ability (Ttrans = 36.6 ℃), which can restore the permanent shape within 60 s at 37 ℃ with a shape fixity ratio of 99% and shape recovery ratio near 100%. In addition, the shape memory mechanism is discussed and shows some application scenarios of ESHs. The as-produced materials can be used as smart biomaterials such as self-tightening sutures, self-sealing root canal filling materials, and so on. 相似文献
3.
Yu-Ting Liu Xian-Bin Li Hui Zheng Nian-Ke Chen Xue-Peng Wang Xu-Lin Zhang Hong-Bo Sun Shengbai Zhang 《Advanced functional materials》2021,31(21):2009803
Phase change memory (PCM) is an emerging non-volatile data storage technology concerned by the semiconductor industry. To improve the performances, previous efforts have mainly focused on partially replacing or doping elements in the flagship Ge-Sb-Te (GST) alloy based on experimental “trial-and-error” methods. Here, the current largest scale PCM materials searching is reported, starting with 124 515 candidate materials, using a rational high-throughput screening strategy consisting of criteria related to PCM characteristics. In the results, there are 158 candidates screened for PCM materials, of which ≈68% are not employed. By further analyses, including cohesive energy, bond angle analyses, and Born effective charge, there are 52 materials with properties similar to the GST system, including Ge2Bi2Te5, GeAs4Te7, GeAs2Te4, so on and other candidates that have not been reported, such as TlBiTe2, TlSbTe2, CdPb3Se4, etc. Compared with GST, materials with close cohesive energy include AgBiTe2, TlSbTe2, As2Te3, TlBiTe2, etc., indicating possible low power consumption. Through further melt-quenching molecular dynamic calculation and structural/electronic analyses, Ge2Bi2Te5, CdPb3Se4, MnBi2Te4, and TlBiTe2 are found suitable for optical/electrical PCM applications, which further verifies the effectiveness of this strategy. The present study will accelerate the exploration and development of advanced PCM materials for current and future big-data applications. 相似文献
4.
5.
Manik Chandra Biswas Samit Chakraborty Abhishek Bhattacharjee Zaheeruddin Mohammed 《Advanced functional materials》2021,31(19):2100257
Shape memory materials (SMMs) in 3D printing (3DP) technology garnered much attention due to their ability to respond to external stimuli, which direct this technology toward an emerging area of research, “4D printing (4DP) technology.” In contrast to classical 3D printed objects, the fourth dimension, time, allows printed objects to undergo significant changes in shape, size, or color when subjected to external stimuli. Highly precise and calibrated 4D materials, which can perform together to achieve robust 4D objects, are in great demand in various fields such as military applications, space suits, robotic systems, apparel, healthcare, sports, etc. This review, for the first time, to the best of the authors’ knowledge, focuses on recent advances in SMMs (e.g., polymers, metals, etc.) based wearable smart textiles and fashion goods. This review integrates the basic overview of 3DP technology, fabrication methods, the transition of 3DP to 4DP, the chemistry behind the fundamental working principles of 4D printed objects, materials selection for smart textiles and fashion goods. The central part summarizes the effect of major external stimuli on 4D textile materials followed by the major applications. Lastly, prospects and challenges are discussed, so that future researchers can continue the progress of this technology. 相似文献
6.
在预测轴承剩余使用寿命时,数据间的时序特性是一个可以利用的重要隐藏信息。为了更好地提取具有时序信息的特征用于预测,提出了一种基于并行多通道卷积长短时记忆网络(PMCCNN-LSTM)的剩余使用寿命预测模型。该模型主要由两部分组成:前端为并行多通道卷积网络(PMCCNN),提取信号特征,挖掘数据的时序特性,并采用逐层训练和微调的方式提升参数的收敛性;后端为长短时记忆(LSTM)网络,基于特征进行剩余使用寿命预测,并采用加权平均的方法对预测结果进行平滑处理。在一个轴承加速寿命实验的公开数据集上使用留一法验证了该模型的准确性,实验结果表明:所提模型的平均误差与最大误差分别比传统的卷积神经网络(CNN)低23.38%和15.84%,比传统的LSTM低24.14%和19.01%,比卷积长短时记忆网络(CNN-LSTM)低30.32%和23.09%。 相似文献
7.
This article develops practical methods for Bayesian inference in the autoregressive fractionally integrated moving average (ARFIMA) model using the exact likelihood function, any proper prior distribution, and time series that may have thousands of observations. These methods utilize sequentially adaptive Bayesian learning, a sequential Monte Carlo algorithm that can exploit massively parallel desktop computing with graphics processing units (GPUs). The article identifies and solves several problems in the computation of the likelihood function that apparently have not been addressed in the literature. Four applications illustrate the utility of the approach. The most ambitious is an ARFIMA(2,d,2) model for the Campito tree ring time series (length 5405), for which the methods developed in the article provide an essentially uncorrelated sample of size 16,384 from the exact posterior distribution in under four hours. Less ambitious applications take as little as 4 minutes without exploiting GPUs. 相似文献
8.
Mingqiang Cheng Erding Zhao Fangjian Jiang Xiaodong Jiang Ze Fang Feng Li Wanneng Ye Yalin Qin Yongcheng Zhang 《Ceramics International》2021,47(13):18417-18423
The materials processing history has a great influence on their properties and finally determines their application effect. In this paper, the ferroelectric, polarization-switching current, and strain properties of Mn-doped 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3 ceramics were studied in fresh state, aged state, and poled state, respectively. Compared with the symmetric polarization-electric-field (P-E) hysteresis loops, current-density-electric-field (J-E) curves, and bipolar electric-field-induced strain (S-E) curves in fresh state samples, asymmetric P-E loops, J-E curves, and bipolar S-E curves were obtained in poled state samples. Well-aged-state samples exhibit double hysteresis P-E loop, four peaks J-E curves, and symmetric S-E curves without negative strain. The symmetry-conforming short-range order (SC-SRO) principle of point defects and internal electric field Ei is employed to clarify the different phenomenon of three states. Results indicated that randomly oriented defect polarization PD in aged samples can reverse the spontaneous polarization PS back and result in the double hysteresis P-E loop and four peaks J-E curves. The oriented PD and resulting Ei in poled-state samples will lead to the asymmetric loops and strain memory effect. 相似文献
9.
A Cooper(II) (Cu2+)-nitrogen coordination-crosslinked network is designed in poly(styrene-co-butadiene-co-styrene) (SBS) to change commercial elastomers into advanced soft materials. Herein, ligand groups into SBS molecular chains by the 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (DPT) click reaction are first introduced. The results from fourier transform infrared (FT-IR), 1H-nuclear magnetic resonance, and X-ray photoelectron spectroscopy (XPS) are verified the successful modification of SBS. The DPT-grafted SBS could then coordinate with copper sulfate (CuSO4) to form a Cu2+-nitrogen bond, which is further characterized using FT-IR, XPS, atomic force microscope, scanning electron microscope, and geometric structure calculations. After modifying SBS to form an SBS-DPT/CuSO4 composite (SBS-DPT2-Cu10), the tensile stress is improved from 11.43 to 23.25 MPa, while the elongation at break is remained almost unchanged, and the corresponding toughness is increased from 33.21 to 63.26 MJ m–3. Moreover, the dynamic nature of the Cu2+-nitrogen coordination bonds enables the SBS-DPT/CuSO4 composite to exhibit sustained thermoplastic performance and excellent shape memory behavior under an external thermal stimulus. 相似文献
10.