全文获取类型
收费全文 | 1307篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 45篇 |
综合类 | 3篇 |
化学工业 | 203篇 |
金属工艺 | 58篇 |
机械仪表 | 21篇 |
建筑科学 | 77篇 |
矿业工程 | 9篇 |
能源动力 | 66篇 |
轻工业 | 97篇 |
水利工程 | 23篇 |
石油天然气 | 4篇 |
无线电 | 105篇 |
一般工业技术 | 212篇 |
冶金工业 | 174篇 |
原子能技术 | 17篇 |
自动化技术 | 208篇 |
出版年
2024年 | 11篇 |
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 17篇 |
2020年 | 12篇 |
2019年 | 25篇 |
2018年 | 22篇 |
2017年 | 26篇 |
2016年 | 29篇 |
2015年 | 26篇 |
2014年 | 26篇 |
2013年 | 72篇 |
2012年 | 58篇 |
2011年 | 80篇 |
2010年 | 72篇 |
2009年 | 63篇 |
2008年 | 116篇 |
2007年 | 95篇 |
2006年 | 71篇 |
2005年 | 87篇 |
2004年 | 53篇 |
2003年 | 38篇 |
2002年 | 44篇 |
2001年 | 26篇 |
2000年 | 11篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 15篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1910年 | 2篇 |
1909年 | 1篇 |
排序方式: 共有1322条查询结果,搜索用时 0 毫秒
81.
Jairam Vanamala Greg CobbJulio Loaiza Kilsun YooLeonard M. Pike Bhimanagouda S. Patil 《Food chemistry》2007,105(4):1404-1411
Bioactive compounds in citrus fruits have been shown to be protective against chronic diseases such as cancer and heart disease, but their levels may be affected by postharvest treatments such as storage and irradiation. In this study, grapefruits were exposed to gamma irradiation at 0, 150 and 300 Gy and then stored at 10 °C for 36 d, followed by an additional 20 d at 20 °C. Flavonoid content, terpenoid content, quality (acidity and total soluble solids) and phenylalanine ammonia-lyase (PAL) activity were evaluated at regular intervals during storage. Irradiation and storage affected (P ? 0.05) the levels of bioactive compounds in grapefruit; however, the effect of storage was prominent. Irradiation differentially affected the flavonoid content of pulp and peel. Fruits exposed to 300 Gy had higher (P ? 0.01) narirutin content in peel compared to control fruits at 12 and 56 d after storage. While storage increased the d-limonene and myrcene content in all treatments, control fruit had higher terpenoid content at the end of the storage. PAL activity was found to be in traces in the peel. In general, irradiation or storage had no considerable effect on total soluble solids; however, acidity decreased (P ? 0.05) with storage. 相似文献
82.
83.
In this paper we consider a unified framework for parameter estimation problems. Under this framework, the unknown parameters appear in a linear fractional transformation (LFT). A key advantage of the LFT problem formulation is that it allows us to efficiently compute gradients, Hessians, and Gauss–Newton directions for general parameter estimation problems without resorting to inefficient finite-difference approximations. The generality of this approach also allows us to consider issues such as identifiability, persistence of excitation, and convergence for a large class of model structures under a single unified framework. 相似文献
84.
85.
10月初,在CEATEC上,松下公司展示了“世界上第一个三维全高清等离子影院系统”以及世界上最大的150英寸108019的等离子显示器。 相似文献
86.
87.
JVC美国公司的母公司为日本Victor Co.,后者近日宣布,它将会关闭位于日本和苏格兰的电视机工厂,将制造部分转移到别的领域,以此提高公司利润率。和之前报道情况不一样的是,该公司称它将会削减电视机在日本的销售数量,而且不再销售消费市场的液晶电视机型,因为它 相似文献
88.
Greg Andraso James Cowles Rose Colt Jay Patel Michael Campbell 《Journal of Great Lakes research》2011,37(4):738-743
The potential of predators to regulate populations of dreissenid mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) has been addressed since early in the dreissenid invasion of North America. Round gobies (Neogobius melanostomus) larger than approximately 60 mm have been shown to prey extensively on dreissenids, whereas smaller round gobies feed mainly on aquatic insects and crustaceans. We propose that ontogenetic changes in pharyngeal morphology may contribute to this diet shift in round gobies. Pharyngeals of 69 round gobies ranging from 31 to 164 mm total length were investigated using light microscopy and scanning electron microscopy. Areas of lower pharyngeals and pharyngobranchial 2 increased allometrically with fish length. Pharyngeals of round gobies smaller than 50 mm contained narrow (< 0.1 mm diameter) papilliform teeth that are consistent with eating soft-bodied prey. By the time round gobies reached approximately 80 mm in length, pharyngeals contained larger diameter (0.3-0.5 mm) molariform teeth typical of those found in molluscivorous fish. Pharyngeal teeth of the largest round gobies also showed considerable wear. Although changes in pharyngeal morphology may contribute to the previously described diet shift in round gobies as they age, genetic and environmental factors both likely influence pharyngeal remodeling and therefore merit further investigation. 相似文献
89.
90.
Electrochemically deposited sol-gel-derived silicate films as a viable alternative in thin-film design 总被引:1,自引:0,他引:1
Sol-gel-derived silicate films were electrochemically deposited on conducting surfaces from a sol consisting of tetramethoxysilane (TMOS). In this method, a sufficiently negative potential is applied to the electrode surface to reduce oxygen to hydroxyl ions, which serves as the catalyst for the hydrolysis and condensation of TMOS. The electrodeposition process was followed by the electrochemical quartz crystal microbalance and cyclic voltammetry. The electrodeposited films were characterized for their surface morphology, porosity, and film thickness using atomic force microscopy, electrochemical probe techniques, surface area and pore size analysis, and profilometry. The electrodeposited films were found to have a completely different surface structure and to be significantly rougher relative to spin-coated films. This is likely due in part to the separation of the gelation and evaporation stages of film formation. The electrodeposited films were found to be permeable to simple redox molecules, such as ruthenium(III) hexaammine and ferrocene methanol. Film thickness can be easily varied from < 75 nm to > 15 microm by varying the electrode potential from -600 mV to more than -1000 mV, respectively. The electrodeposition process was further applied for the electroencapsulation of redox molecules and organic dyes within the silicate network. Cyclic voltammograms for the gel-entrapped ferrocene methanol (FcCH2OH) and ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) exhibited the characteristic redox behavior of the molecules. The electroencapsulation of organic dyes in their "native" form proved to be more difficult because these species typically contain reducible functionalities that change the structure of the dye. 相似文献