全文获取类型
收费全文 | 16642篇 |
免费 | 1327篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 249篇 |
综合类 | 31篇 |
化学工业 | 3819篇 |
金属工艺 | 515篇 |
机械仪表 | 905篇 |
建筑科学 | 384篇 |
矿业工程 | 7篇 |
能源动力 | 746篇 |
轻工业 | 1450篇 |
水利工程 | 51篇 |
石油天然气 | 13篇 |
无线电 | 3160篇 |
一般工业技术 | 3601篇 |
冶金工业 | 1044篇 |
原子能技术 | 238篇 |
自动化技术 | 1819篇 |
出版年
2024年 | 30篇 |
2023年 | 216篇 |
2022年 | 341篇 |
2021年 | 546篇 |
2020年 | 408篇 |
2019年 | 451篇 |
2018年 | 620篇 |
2017年 | 537篇 |
2016年 | 701篇 |
2015年 | 573篇 |
2014年 | 770篇 |
2013年 | 1196篇 |
2012年 | 1037篇 |
2011年 | 1289篇 |
2010年 | 1001篇 |
2009年 | 1036篇 |
2008年 | 913篇 |
2007年 | 688篇 |
2006年 | 644篇 |
2005年 | 527篇 |
2004年 | 514篇 |
2003年 | 458篇 |
2002年 | 409篇 |
2001年 | 332篇 |
2000年 | 309篇 |
1999年 | 311篇 |
1998年 | 437篇 |
1997年 | 322篇 |
1996年 | 252篇 |
1995年 | 196篇 |
1994年 | 144篇 |
1993年 | 98篇 |
1992年 | 89篇 |
1991年 | 73篇 |
1990年 | 80篇 |
1989年 | 68篇 |
1988年 | 46篇 |
1987年 | 57篇 |
1986年 | 53篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 29篇 |
1982年 | 8篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 19篇 |
1976年 | 26篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Qinyun Chen Huang Shi Chi-Tang Ho 《Journal of the American Oil Chemists' Society》1992,69(10):999-1002
Rosemary (Rosemarinus officinalis L.) leaves were extracted with three different solvents, namely hexane, acetone and methanol. A reverse-phase high-performance
liquid chromatography system in combination with a mass detector was used to quantitate the content of carnosol, carnosic
acid and ursolic acid in the rosemary extracts. All rosemary extracts showed strong inhibitory effects on lipid oxidation
and soybean lipoxygenase activity. 相似文献
32.
33.
Xiao Teng-Fei Li Xiao-Dong Ho John K. L. 《International Journal of Control, Automation and Systems》2015,13(1):222-230
In this article, a novel fuzzy systems based on adaptive Iterative Learning Control (ILC) strategy is presented to deal with a class of non-parametric nonlinear discrete-time systems which perform iteration-varying reference trajectory tracking. Using the technique of fuzzy systems to compensate for the non-parametric uncertainty of the discrete-time system dynamics, the proposed adaptive ILC scheme can well track the iteration-varying reference trajectory beyond the initial time points. The convergence of the fuzzy systems based adaptive ILC algorithm is guaranteed by theoretical analysis, and a numerical example is given to illustrate the effectiveness of the adaptive ILC scheme.
相似文献34.
Color segmentation takes a great attention because color is an effective and robust visual cue for characterizing an object from the others. However, color segmentation suffers from color variations incurred by irregular illumination changes. We propose a reliable color modeling approach in hue–saturation–intensity (HSI) color space while considering intensity information by adopting the B-spline curve fitting to make a mathematical model for statistical characteristics of a color with respect to intensity. It is based on the fact that color distribution of a single-colored object is not invariant with respect to brightness variations even in the HS (hue–saturation) plane. The statistical characteristics contain the mean and standard deviation of hue and saturation with respect to intensity. They are mathematically expressed as four bar graphs. In order to fit the bar graphs to continuous curves, we use B-spline curve fitting procedure. From several experimental results, we verify that the proposed algorithm is successfully applied to color segmentation under various illumination conditions. 相似文献
35.
36.
Translucent scattering phantoms hidden inside a 5.5-cm-thick Intralipid solution were imaged as a function of phantom scattering coefficients by the use of a picosecond time- and space-gated Kerr-Fourier imaging system. A 2-mm-thick translucent phantom with a 0.1% concentration (scattering coefficient) difference from the 55-mm-thick surrounding scattering host can be distinguished at a signal level of ~10(-10) of the incidence illumination intensity. 相似文献
37.
38.
Jiabin Liu Jiawei Deng Yangyang Zhu Xiaokang Geng Lifu Zhang Sang Young Jeong Dan Zhou Han Young Woo Dong Chen Feiyan Wu Lie Chen 《Advanced materials (Deerfield Beach, Fla.)》2023,35(1):2208008
With the great potential of the all-polymer solar cells for large-area wearable devices, both large-area device efficiency and mechanical flexibility are very critical but attract limited attention. In this work, from the perspective of the polymer configurations, two types of terpolymer acceptors PYTX-A and PYTX-B (X = Cl or H) are developed. The configuration difference caused by the replacement of non-conjugated units results in distinct photovoltaic performance and mechanical flexibility. Benefiting from a good match between the intrinsically slow film-forming of the active materials and the technically slow film-forming of the blade-coating process, the toluene-processed large-area (1.21 cm2) binary device achieves a record efficiency of 14.70%. More importantly, a new parameter of efficiency stretchability factor (ESF) is proposed for the first time to comprehensively evaluate the overall device performance. PM6:PYTCl-A and PM6:PYTCl-B yield significantly higher ESF than PM6:PY-IT. Further blending with non-conjugated polymer donor PM6-A, the best ESF of 3.12% is achieved for PM6-A:PYTCl-A, which is among the highest comprehensive performances. 相似文献
39.
The effect of light absorption by sample in the analysis of Makerfringe data for estimating a second-order nonlinear coefficient hasbeen studied experimentally. Two theories, one by Jerphagnon andKurtz that neglects the absorption effect and one by Herman and Haydenthat takes into account the absorption effect, were compared with theexperimental results. It was found that Jerphagnon and Kurtz'sformula was unable to predict correctly not only the magnitude but alsothe incident angle dependence or the sample thickness dependence of thesecond harmonic signal generated by the sample with strong absorption, whereas the theory by Herman and Hayden was able to make thosepredictions fairly well. It was also found that the error in theestimated nonlinear coefficient when one uses Jerphagnon and Kurtz'sformula could be as large as 2-4 times the true value, depending onsample thickness. 相似文献
40.
Tissue dynamics spectroscopy combines dynamic light scattering with short-coherence digital holography to capture intracellular motion inside multicellular tumor spheroid tissue models. The cellular mechanical activity becomes an endogenous imaging contrast agent for motility contrast imaging. Fluctuation spectroscopy is performed on dynamic speckle from the proliferating shell and hypoxic core to generate drug-response spectrograms that are frequency versus time representations of the changes in spectral content induced by an applied compound or an environmental perturbation. A combination of 28 reference compounds and conditions applied to rat osteogenic UMR-106 spheroids generated spectrograms that were crosscorrelated in a similarity matrix used for unsupervised hierarchical clustering of similar compound responses. This work establishes the feasibility of tissue dynamics spectroscopy for three-dimensional tissue-based phenotypic profiling of drug response as a fully endogenous probe of the response of tissue to reference compounds. 相似文献