全文获取类型
收费全文 | 199910篇 |
免费 | 21575篇 |
国内免费 | 13972篇 |
学科分类
工业技术 | 235457篇 |
出版年
2024年 | 763篇 |
2023年 | 3096篇 |
2022年 | 6921篇 |
2021年 | 9230篇 |
2020年 | 6777篇 |
2019年 | 5039篇 |
2018年 | 5442篇 |
2017年 | 6215篇 |
2016年 | 5426篇 |
2015年 | 8570篇 |
2014年 | 10918篇 |
2013年 | 13015篇 |
2012年 | 15850篇 |
2011年 | 16455篇 |
2010年 | 15490篇 |
2009年 | 14791篇 |
2008年 | 15201篇 |
2007年 | 14786篇 |
2006年 | 13347篇 |
2005年 | 10899篇 |
2004年 | 7705篇 |
2003年 | 5630篇 |
2002年 | 5493篇 |
2001年 | 4745篇 |
2000年 | 3865篇 |
1999年 | 2475篇 |
1998年 | 1501篇 |
1997年 | 1174篇 |
1996年 | 1014篇 |
1995年 | 767篇 |
1994年 | 620篇 |
1993年 | 452篇 |
1992年 | 402篇 |
1991年 | 291篇 |
1990年 | 233篇 |
1989年 | 209篇 |
1988年 | 121篇 |
1987年 | 120篇 |
1986年 | 84篇 |
1985年 | 40篇 |
1984年 | 32篇 |
1983年 | 42篇 |
1982年 | 25篇 |
1981年 | 41篇 |
1980年 | 56篇 |
1979年 | 25篇 |
1965年 | 2篇 |
1960年 | 2篇 |
1959年 | 29篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
在无线传感器网络中,大量感知数据汇集到sink节点的采集方法会导致sink节点附近的节点能量耗尽,造成能量空洞。针对该问题,利用移动的sink节点进行数据收集是一种解决方法,其中移动sink的路径规划成为一个重要的问题。提出了一个移动sink路径规划算法,将无线传感器中随机分布的节点划分为不同的子区域,寻找sink节点移动的最佳转向点,最终得到最优的移动路径,以实现无线传感器网络生命周期最大化。仿真实验表明,与现有方案相比,该算法能显著延长网络的生命周期。 相似文献
52.
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process.... 相似文献
53.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
54.
55.
Dy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm-white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance. 相似文献
56.
对在线自动监测仪监测结果与人工化验数据存在误差的原因进行分析,以提高在线自动监测仪监测结果的科学性和可靠性,并提出了相对应的建议,有效提升装置出水合格率。 相似文献
57.
以聚乙烯醇(PVA)和水华蓝藻为主要原料,通过溶液铺膜法制备了蓝藻/PVA共混膜,采用万能试验机,研究了不同助剂对蓝藻/PVA共混膜力学性能的影响。结果表明,蓝藻的添加显著降低了共混膜的力学性能。当添加比例为PVA的1/2时,膜的拉伸强度和断裂伸长率分别比无藻处理下降了65.89%和79.57%。甘油、尿素显著提升了蓝藻/PVA共混膜的断裂伸长率,当添加比例为蓝藻的1/2时,分别能使共混膜的断裂伸长率提高73.20倍和62.02倍。虽然柠檬酸、硅烷偶联剂能够提升蓝藻/PVA共混膜的拉伸强度,但只能在低剂量时促进断裂伸长率的小幅提高,当柠檬酸添加比例为蓝藻的1/40时,膜的断裂伸长率能提高4.41倍,而当硅烷偶联剂添加比例为蓝藻的1/20时,膜的断裂伸长率能提高1.49倍。尿素与甘油复合增塑,更有利于提升共混膜的断裂伸长率。硅烷偶联剂与甘油复合增塑,更有利于提升共混膜的拉伸强度。 相似文献
58.
59.
60.
Xiaohui Hu Li Cheng Yan Hong Zhaofeng Li Caiming Li Zhengbiao Gu 《International Journal of Food Science & Technology》2021,56(8):4149-4158
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%. 相似文献