全文获取类型
收费全文 | 23238篇 |
免费 | 465篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 271篇 |
综合类 | 16篇 |
化学工业 | 3702篇 |
金属工艺 | 494篇 |
机械仪表 | 445篇 |
建筑科学 | 989篇 |
矿业工程 | 107篇 |
能源动力 | 507篇 |
轻工业 | 2004篇 |
水利工程 | 194篇 |
石油天然气 | 156篇 |
无线电 | 2007篇 |
一般工业技术 | 3490篇 |
冶金工业 | 6798篇 |
原子能技术 | 253篇 |
自动化技术 | 2302篇 |
出版年
2021年 | 213篇 |
2020年 | 165篇 |
2019年 | 198篇 |
2018年 | 236篇 |
2017年 | 208篇 |
2016年 | 217篇 |
2015年 | 214篇 |
2014年 | 385篇 |
2013年 | 996篇 |
2012年 | 580篇 |
2011年 | 752篇 |
2010年 | 602篇 |
2009年 | 637篇 |
2008年 | 811篇 |
2007年 | 783篇 |
2006年 | 736篇 |
2005年 | 643篇 |
2004年 | 552篇 |
2003年 | 598篇 |
2002年 | 517篇 |
2001年 | 466篇 |
2000年 | 455篇 |
1999年 | 525篇 |
1998年 | 1439篇 |
1997年 | 952篇 |
1996年 | 712篇 |
1995年 | 561篇 |
1994年 | 505篇 |
1993年 | 517篇 |
1992年 | 404篇 |
1991年 | 330篇 |
1990年 | 363篇 |
1989年 | 334篇 |
1988年 | 333篇 |
1987年 | 314篇 |
1986年 | 311篇 |
1985年 | 394篇 |
1984年 | 339篇 |
1983年 | 322篇 |
1982年 | 329篇 |
1981年 | 303篇 |
1980年 | 279篇 |
1979年 | 250篇 |
1978年 | 252篇 |
1977年 | 335篇 |
1976年 | 401篇 |
1975年 | 219篇 |
1974年 | 212篇 |
1973年 | 205篇 |
1972年 | 136篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
1.
Shanshan Zhuang Wenxiong Zheng Yunong Na Naiyi Chen Fan Gong Bingxuan Huang Stephen Brennan Charles Congyi Liu Jian Cheng Lukai Ma Huifan Liu 《International Journal of Food Science & Technology》2022,57(2):1093-1103
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results. 相似文献
2.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
3.
4.
Thomas R. Savage Fernando Almeida-Trasvina Ehecatl A. del-Rio Chanona Robin Smith Dondga Zhang 《American Institute of Chemical Engineers》2021,67(11):e17358
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems. 相似文献
5.
Belcher Calvin H. Zheng Baolong MacDonald Benjamin E. Langlois Eric D. Lehman Benjamin Pearce Charles Delaney Robert Apelian Diran Lavernia Enrique J. Monson Todd C. 《Journal of Materials Science》2022,57(9):5518-5532
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic... 相似文献
6.
7.
8.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献
9.
10.
Qin-yu Zhou Shan Zhao Yan-yan Huang Jin-shuang Hu Jia-hua Kuang Dong-mei Liu Charles S. Brennan 《International Journal of Food Science & Technology》2021,56(6):2992-3003
Yogurt preserves and enhances nutritional value of milk. In this study, we have compared several strains to determine the physicochemical, sensory, rheological and aroma characteristics of different yogurts. We used Lactobacillus gasseri LGZ 1029 (LG), commercial probiotic L. rhamnosus (LGG) and traditional fermentation strains Streptococcus thermophilus and L. bulgaricus (SL). Results showed that the flavour and texture characteristics of mixed-strain yogurts were obviously better than in single-strain yogurts. Addition of LG increased pseudoplastic behaviour, as shown by Herschel–Bulkley model analysis of rheological behaviour. The LG + SL group also had both the highest viscosity consistency index and thickening ability. In addition, a total of 57 volatile compounds were detected in yogurts and the fermentation with the addition of LG was mainly affected by ketones. Our study suggested that a yogurt with new attributes can be produced by using LGZ 1029. 相似文献