全文获取类型
收费全文 | 241282篇 |
免费 | 21747篇 |
国内免费 | 11838篇 |
学科分类
工业技术 | 274867篇 |
出版年
2024年 | 452篇 |
2023年 | 3823篇 |
2022年 | 6480篇 |
2021年 | 9835篇 |
2020年 | 7644篇 |
2019年 | 6194篇 |
2018年 | 6959篇 |
2017年 | 7759篇 |
2016年 | 7138篇 |
2015年 | 9725篇 |
2014年 | 12399篇 |
2013年 | 14908篇 |
2012年 | 16748篇 |
2011年 | 17758篇 |
2010年 | 15670篇 |
2009年 | 14965篇 |
2008年 | 14478篇 |
2007年 | 13592篇 |
2006年 | 13636篇 |
2005年 | 11620篇 |
2004年 | 8325篇 |
2003年 | 7212篇 |
2002年 | 7253篇 |
2001年 | 6421篇 |
2000年 | 5377篇 |
1999年 | 5412篇 |
1998年 | 4254篇 |
1997年 | 3585篇 |
1996年 | 3303篇 |
1995年 | 2762篇 |
1994年 | 2184篇 |
1993年 | 1582篇 |
1992年 | 1274篇 |
1991年 | 956篇 |
1990年 | 715篇 |
1989年 | 556篇 |
1988年 | 454篇 |
1987年 | 309篇 |
1986年 | 225篇 |
1985年 | 167篇 |
1984年 | 143篇 |
1983年 | 106篇 |
1982年 | 96篇 |
1981年 | 84篇 |
1980年 | 79篇 |
1979年 | 43篇 |
1978年 | 33篇 |
1977年 | 36篇 |
1976年 | 41篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns. 相似文献
32.
33.
Yang Hu Stephanie M. Sjoberg Chunpen Chen Amber L. Hauvermale Craig F. Morris Stephen R. Delwiche Ashley E. Cannon Camille M. Steber Zhiwu Zhang 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2105-2117
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging. 相似文献
34.
Engineering with Computers - To increase the efficiency and accuracy in slope stability analysis, a reliability analysis method based on machine learning and the advanced first-order second-moment... 相似文献
35.
Knowledge and Information Systems - Representation learning approaches require a massive amount of discriminative training data, which is unavailable in many scenarios, such as healthcare, smart... 相似文献
36.
Knowledge and Information Systems - Crowdsourcing systems provide an efficient way to collect labeled data by employing non-expert crowd workers. In practice, each instance obtains a multiple noisy... 相似文献
37.
大数据时代,数据规模庞大,由数据进行驱动的应用分析场景日益增多.如何快速、高效地从这些海量数据中提取出用以分析决策的信息,给数据库系统带来重大挑战.同时,现代商业分析决策对分析数据的实时性要求数据库系统能够同时快速处理ACID事务和复杂的分析查询.然而,传统的数据分区粒度太粗,且不能适应动态变化的复杂分析负载;传统的数据布局单一,不能应对现代大量增加的混合事务分析应用场景.为了解决以上问题,“智能数据分区与布局”成为当前的研究热点之一,它通过数据挖掘、机器学习等技术抽取工作负载的有效特征,设计最佳的分区策略来避免扫描大量不相关的数据,指导布局结构设计以适应不同类型的工作负载.首先介绍了智能数据分区与布局的相关背景知识,然后对智能数据分区与布局技术的研究动机、发展趋势、关键技术进行详细的阐述.最后,对智能数据分区与布局技术的研究前景做出总结与展望. 相似文献
38.
Baohua Yuan Lili Wei Lixia Yang Liangjiu Bai Huawei Yang Donglei Wei Feng Wang Wenxiang Wang Hou Chen 《Journal of the American Ceramic Society》2022,105(2):801-805
Solar steam generation has attracted considerable interest due to its easy accessibility and sustainability. However, dye molecules were gradually concentrated on bulk water or the surface of solar absorbers during the disposal of dye wastewater. Herein, LaB6/g-C3N4 composites were immobilized on porous cotton cloth, served as a solar absorber resistant to dye clogging. The optimal solar absorber possessed solar harvesting of 92.3% and showed great application potential in the field of the treatment of dye wastewater. This study presented a new approach for the treatment of dye wastewater. 相似文献
39.
40.
Yumin An Yi Yang Yongna Jia Wenbo Han Yehong Cheng 《Journal of the American Ceramic Society》2022,105(4):2385-2391
Biomimetic Bouligand architecture is constructed in the ceramic to improve its toughness. Firstly, unidirectional carbon fiber-reinforced ZrB2-SiC ceramic films are achieved through a vacuum-assisted filtration method using graphene oxide. Then, ceramic films are helically assembled at a fixed angle of 30° in the graphite die based on the fiber orientation. Finally, the spark plasma sintering method was utilized to densify helical assembly carbon fiber/ceramic films. By constructing Bouligand structure, high fracture toughness (7.4 MPa·m0.5) and work of fracture (∼1055 J/m2) are achieved in ZrB2-based ceramic. The toughening mechanisms mainly are crack deflection, twisting and branching, carbon fiber pulling out, and bridging. 相似文献