全文获取类型
收费全文 | 129625篇 |
免费 | 7793篇 |
国内免费 | 6629篇 |
专业分类
电工技术 | 4853篇 |
技术理论 | 5篇 |
综合类 | 11523篇 |
化学工业 | 24288篇 |
金属工艺 | 11239篇 |
机械仪表 | 4458篇 |
建筑科学 | 6912篇 |
矿业工程 | 2190篇 |
能源动力 | 3273篇 |
轻工业 | 11235篇 |
水利工程 | 2308篇 |
石油天然气 | 6479篇 |
武器工业 | 1200篇 |
无线电 | 8358篇 |
一般工业技术 | 19798篇 |
冶金工业 | 5376篇 |
原子能技术 | 2360篇 |
自动化技术 | 18192篇 |
出版年
2024年 | 309篇 |
2023年 | 820篇 |
2022年 | 1662篇 |
2021年 | 1890篇 |
2020年 | 2241篇 |
2019年 | 2055篇 |
2018年 | 2238篇 |
2017年 | 2538篇 |
2016年 | 3103篇 |
2015年 | 3878篇 |
2014年 | 6004篇 |
2013年 | 6810篇 |
2012年 | 6680篇 |
2011年 | 7609篇 |
2010年 | 6152篇 |
2009年 | 7617篇 |
2008年 | 7131篇 |
2007年 | 8350篇 |
2006年 | 7669篇 |
2005年 | 6533篇 |
2004年 | 5558篇 |
2003年 | 5263篇 |
2002年 | 5116篇 |
2001年 | 3915篇 |
2000年 | 4120篇 |
1999年 | 3825篇 |
1998年 | 3205篇 |
1997年 | 2904篇 |
1996年 | 3045篇 |
1995年 | 3004篇 |
1994年 | 2717篇 |
1993年 | 1660篇 |
1992年 | 1684篇 |
1991年 | 1143篇 |
1990年 | 804篇 |
1989年 | 712篇 |
1988年 | 666篇 |
1987年 | 391篇 |
1986年 | 234篇 |
1985年 | 378篇 |
1984年 | 421篇 |
1983年 | 435篇 |
1982年 | 333篇 |
1981年 | 415篇 |
1980年 | 278篇 |
1979年 | 118篇 |
1978年 | 114篇 |
1977年 | 71篇 |
1976年 | 44篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
3.
An efficient algorithm is presented for numerically evaluating a self-consistent field theoretic (SCFT) model of block copolymer structure. This algorithm is implemented on a distributed memory parallel cluster in order to solve the SCFT equations on large computational grids. Simulation results are presented for a two-component molten mixture of a symmetric ABA triblock copolymer with an A homopolymer. These results illustrate a case in which simulating a large system is required to resolve features with a wide range of length scales. 相似文献
4.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS). 相似文献
5.
6.
在阐述客户服务意义的基础上,提出对中国石化成品油销售企业客户服务体系建设的建议,即建立以客户为尊的服务理念;建设特色企业文化;完善员工服务体系;注重细节,提高服务质量;整合现有客户体系资源,拓展服务功能。 相似文献
7.
8.
Six genotypes of sweet potato commercially available in Taiwan, including TNG57, TNG66, TNG68, TYY1, RP and WP, were used as samples in this study of the effects of steaming and kneading with pre-steaming treatments on the antioxidant components and antioxidant properties of methanolic extracts. Steam treatment increased the total phenols contents of all genotypes (2–13 times), flavonoids content of RP (1.3 times) and anthocyanins contents of RP and WP (5–6 times). Steam treatment also increased the reducing power and scavenging DPPH radical effect of sweet potato flours. For the methanolic extracts of steamed and kneaded flours, reducing powers were 0.02–1.70 at 5.0 mg ml−1 and the scavenging effects on DPPH radicals were 19–92% at 2.5 mg ml−1. Both showed the order of RP > WP > TYY1 and TNG66 > TNG57 and TNG68. However, the chelating effect of the six genotypes at 1.0 mg ml−1 ranged from 50% to 73%. Contents of total phenols, flavonoids, and anthocyanins of sweet potato flours were significantly positively correlated with the reducing power and scavenging DPPH radical effects. After steaming and kneading treatments, RP showed the highest increase in the contents of total phenols, flavonoids and anthocyanins among the six genotypes studied. 相似文献
9.
This paper describes the methodology for simulating a reprographic ink with a ceramic ink based on a commercially available zirconia powder for direct ceramic ink-jet printing. Of over-riding importance was matching viscosity and this was tested systematically by using a mineral oil–hexane binary system. Of secondary importance was adjustment of the pressure defect behind the nozzle to compensate for small differences in surface tension. The inks tested in the wide array print-head were based on low electrical conductivity liquids to avoid damage to the electroding system. The organic binder for the zirconia ink was paraffin wax and the dispersant was a hydroxystearic acid based polyester. 相似文献
10.