全文获取类型
收费全文 | 30434篇 |
免费 | 2894篇 |
国内免费 | 1090篇 |
专业分类
电工技术 | 3167篇 |
综合类 | 3332篇 |
化学工业 | 3317篇 |
金属工艺 | 873篇 |
机械仪表 | 887篇 |
建筑科学 | 7274篇 |
矿业工程 | 1144篇 |
能源动力 | 1066篇 |
轻工业 | 4005篇 |
水利工程 | 1880篇 |
石油天然气 | 1552篇 |
武器工业 | 139篇 |
无线电 | 1495篇 |
一般工业技术 | 1984篇 |
冶金工业 | 993篇 |
原子能技术 | 112篇 |
自动化技术 | 1198篇 |
出版年
2024年 | 68篇 |
2023年 | 368篇 |
2022年 | 703篇 |
2021年 | 862篇 |
2020年 | 938篇 |
2019年 | 858篇 |
2018年 | 811篇 |
2017年 | 941篇 |
2016年 | 1009篇 |
2015年 | 1063篇 |
2014年 | 1838篇 |
2013年 | 1701篇 |
2012年 | 2196篇 |
2011年 | 2391篇 |
2010年 | 1738篇 |
2009年 | 1907篇 |
2008年 | 1735篇 |
2007年 | 2238篇 |
2006年 | 2008篇 |
2005年 | 1636篇 |
2004年 | 1320篇 |
2003年 | 1078篇 |
2002年 | 959篇 |
2001年 | 827篇 |
2000年 | 637篇 |
1999年 | 504篇 |
1998年 | 431篇 |
1997年 | 342篇 |
1996年 | 275篇 |
1995年 | 226篇 |
1994年 | 201篇 |
1993年 | 129篇 |
1992年 | 111篇 |
1991年 | 73篇 |
1990年 | 53篇 |
1989年 | 55篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 30篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 23篇 |
1979年 | 6篇 |
1959年 | 2篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
91.
92.
By leveraging the secret data coding using the remainder storage based exploiting modification direction (RSBEMD), and the pixel change operation recording based on multi-segment left and right histogram shifting, a novel reversible data hiding (RHD) scheme is proposed in this paper. The secret data are first encoded by some specific pixel change operations to the pixels in groups. After that, multi-segment left and right histogram shifting based on threshold manipulation is implemented for recording the pixel change operations. Furthermore, a multiple embedding policy based on chess board prediction (CBP) and threshold manipulation is put forward, and the threshold can be adjusted to achieve adaptive data hiding. Experimental results and analysis show that it is reversible and can achieve good performance in capacity and imperceptibility compared with the existing methods. 相似文献
93.
分析了乙炔发生器发气能力低的原因,对发生器温度、发生器压力及发生器耙齿等方面进行了改进,提高了发气量。 相似文献
94.
Liezhou Zhong Hayder Ali Zhongxiang Fang Mark L. Wahlqvist Jonathan M. Hodgson Stuart K. Johnson 《International Journal of Food Science & Technology》2020,55(4):1816-1824
The high proportion of seed coat of legume lupins results in big milling lose during kernel flour production, though the seed coat could be value-added as human food. The physicochemical and nutritional properties and antioxidant capacities of seed coats of six Australian sweet lupin cultivars grown at two locations were evaluated. Results showed that genotype, environment and their interaction were significant for seed coat percentage, proximate composition, dietary fibre content, polyphenols and antioxidant capacities. Strong correlations between seed coat lightness and polyphenol content were found. A comparison using multivariate analysis of the seed coat properties showed clear separation based on growing sites. This study indicates the enormous potential of Australian sweet lupin seed coat as an ‘antioxidant dietary fibre’ food source. The results could also benefit to breed varieties with desirable levels of nutrients and phytochemicals. 相似文献
95.
V.A. Dekhtyarenko T.V. Pryadko D.G. Savvakin V.I. Bondarchuk G.S. Mogylnyy 《International Journal of Hydrogen Energy》2021,46(11):8040-8047
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature. 相似文献
96.
Mohammed Alomair Stelios Georgiou Stella Stylianou 《Quality and Reliability Engineering International》2021,37(1):90-107
Since their introduction by Box and Hunter, resolution criteria have been widely used when comparing regular fractional factorials designs. In this article, we investigate how a generalized resolution criterion can be used to assess some recently developed three-level screening designs, such as definitive screening designs (DSDs) and screening designs from weighing matrices. The aim of this paper is to capture the projection properties of those three-level screening designs, complementing the work of Deng and Tang, who used generalized resolution and minimum aberration criteria for ranking different two-level designs, particularly Plackett-Burman and other nonregular factorial designs. An advantage of generalized resolution, extended here to work on three-level designs, is that it offers a useful criterion for ranking three-level screening designs, whereas the Deng and Tang resolution is used mainly for the assessment of two-level designs. In addition, we applied a projection estimation capacity (PEC) criterion to select three-level screening designs with desirable properties. Practical examples and the best projections of the designs are presented in tables. 相似文献
97.
98.
探究分别含有A1、A2两种β-酪蛋白牛乳制成的搅拌型和凝固型酸奶产品特性的区别。持水力结果表明,A1 β-酪蛋白酸奶(凝固型和搅拌型)的持水力大于69%,A2 β-酪蛋白酸奶(凝固型和搅拌型)的持水力大于65%。质构特性的结果显示,凝固型酸奶差距更为明显,A1 β-酪蛋白酸奶的硬度和稠度分别比A2 β-酪蛋白酸奶高41.4%和59.8%。此外,A1 β-酪蛋白酸奶黏性优于A2 β-酪蛋白酸奶。流变学特性与微观结构结果显示,A1 β-酪蛋白酸奶的滞后回路面积较A2 β-酪蛋白酸奶小14.6%,说明A2 β-酪蛋白制成的酸奶结构更易于被破坏,网状结构更为稀疏。本实验为A2 β-酪蛋白牛乳在酸奶制品的应用及实际生产提供一定理论支持。 相似文献
99.
Yuhang Xing Ruyi Li Lu Xue Mianhong Chen Xuli Lu Zhihao Duan Wei Zhou Jihua Li 《International Journal of Food Science & Technology》2022,57(8):5268-5279
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin. 相似文献
100.
随着人口及经济的快速增长,人类对矿产资源的需求量也迅猛增长,矿产资源需求量的急剧增加与矿产资源不可再生之间的矛盾日益突出。地球上有限的矿产资源还能供人类享用多久?现有的矿产资源最大限度能供地球上多少人享用?章提出了矿产资源环境溶量的概念,以期对今后矿产资源合理开发提供阈限值。 相似文献