全文获取类型
收费全文 | 459703篇 |
免费 | 37915篇 |
国内免费 | 20126篇 |
专业分类
电工技术 | 28074篇 |
技术理论 | 42篇 |
综合类 | 31631篇 |
化学工业 | 75307篇 |
金属工艺 | 25626篇 |
机械仪表 | 29310篇 |
建筑科学 | 37452篇 |
矿业工程 | 14311篇 |
能源动力 | 12999篇 |
轻工业 | 31649篇 |
水利工程 | 8435篇 |
石油天然气 | 28921篇 |
武器工业 | 3878篇 |
无线电 | 51013篇 |
一般工业技术 | 51446篇 |
冶金工业 | 22874篇 |
原子能技术 | 5133篇 |
自动化技术 | 59643篇 |
出版年
2024年 | 2065篇 |
2023年 | 7387篇 |
2022年 | 13580篇 |
2021年 | 18804篇 |
2020年 | 14362篇 |
2019年 | 11764篇 |
2018年 | 13211篇 |
2017年 | 14890篇 |
2016年 | 13225篇 |
2015年 | 18170篇 |
2014年 | 22929篇 |
2013年 | 26853篇 |
2012年 | 29433篇 |
2011年 | 31738篇 |
2010年 | 28164篇 |
2009年 | 26778篇 |
2008年 | 26304篇 |
2007年 | 24853篇 |
2006年 | 25316篇 |
2005年 | 21833篇 |
2004年 | 14844篇 |
2003年 | 12722篇 |
2002年 | 11992篇 |
2001年 | 10734篇 |
2000年 | 10914篇 |
1999年 | 11908篇 |
1998年 | 9780篇 |
1997年 | 8115篇 |
1996年 | 7602篇 |
1995年 | 6351篇 |
1994年 | 5155篇 |
1993年 | 3629篇 |
1992年 | 2958篇 |
1991年 | 2294篇 |
1990年 | 1695篇 |
1989年 | 1430篇 |
1988年 | 1076篇 |
1987年 | 704篇 |
1986年 | 543篇 |
1985年 | 355篇 |
1984年 | 257篇 |
1983年 | 200篇 |
1982年 | 221篇 |
1981年 | 170篇 |
1980年 | 154篇 |
1979年 | 63篇 |
1978年 | 31篇 |
1977年 | 22篇 |
1976年 | 44篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Ibuprofen is a well-known nonsteroidal anti-inflammatory drug, which can interact with lipid membranes. In this paper, the interaction of ibuprofen with bilayer lipid membrane was studied by UV-vis spectroscopy, cyclic voltammetry and AC impedance spectroscopy. UV-vis spectroscopy data indicated directly that ibuprofen could interact with lipid vesicles. In electrochemical experiments, ibuprofen displayed a biphasic behavior on bilayer lipid membrane supported on a glassy carbon electrode. It could stabilize the lipid membrane in low concentration, while it induced defects formation, even removed off bilayer lipid membrane from the surface of the electrode with increasing concentration. The mechanism about the interaction between ibuprofen and supported bilayer lipid membrane was discussed. 相似文献
992.
Huang L. Chew K. A. Thilakawardana S. Liu Y. Moessner K. Tafazolli R. 《Broadcasting, IEEE Transactions on》2006,52(4):492-504
Recently, an upsurge of interest has been observed in providing multimedia on-demand (MoD) services to mobile users over wireless networks. Nevertheless, due to the rapidly varying nature of mobile networks and the scarcity of radio resources, the commercial implementation is still limited. This paper presents an efficient group-based multimedia-on-demand (GMoD) service model over multicast-enabled wireless infrastructures, where users requesting the same content are grouped and served simultaneously with a single multicast stream. The grouping is fulfilled through a process named "batching". An analytical model is derived to analyse a timeout-based batching scheme with respect to the tradeoff between user blocking probability and reneging probability. Based on the deduced analytical model, an optimal timeout-based batching scheme is proposed to dynamically identify the optimal tradeoff point that maximizes the system satisfaction ratio given a particular system status. The proposed scheme is evaluated by means of simulation and compared with two basic batching schemes (timeout-based, size-based), and two hybrid ones (combined-for-profit, combined-for-loss). The simulation results demonstrate the proposed approach can ensure significant gains in terms of user satisfaction ratio, with low reneging and blocking probabilities 相似文献
993.
2006年,一场百年不遇的特大干旱袭击了四川省21个市、州的139个县(市、区)。据统计,干旱造成全省作物受旱188.52万hm^2,成灾116.55万hm^2,绝收27.73万hm^2,造成农业直接经济损失87.7亿元,有443.6万人出现临时饮水困难。为抗御干旱,四川水利经受了一次严峻的考验,作为四川水利的重要组成部分,已有2260多年历史的都江堰水利也同样经历了一个酷热的夏天。 相似文献
994.
引入空分设备“有效产品成本”概念,以气体成本算法和液体成本算法对空分设备正常产品单位成本和有效产品单位成本进行了比较,举例计算了液化装置的产品成本,提出利用“有效产品成本”概念来组织空分设备生产。 相似文献
995.
Ten-user truly asynchronous gigabit OCDMA transmission experiment with a 511-chip SSFBG en/decoder 总被引:8,自引:0,他引:8
Hamanaka T. Xu Wang Naoya Wada Nishiki A. Kitayama K. 《Lightwave Technology, Journal of》2006,24(1):95-102
A ten-user truly asynchronous gigabit coherent-optical-code-division-multiple-access (OCDMA) transmission was experimentally demonstrated without using any timing coordination. The enabling technologies are a record-length 511-chip superstructured-fiber-Bragg-grating (SSFBG) en/decoder and a supercontinuum (SC)-based optical-thresholding technique to significantly suppress the signal interference beat noise as well as the multiple-access-interference (MAI) noise. 相似文献
996.
997.
Shin S.-C. Ming-Da Tsai Ren-Chieh Liu Lin K.-Y. Huei Wang 《Microwave and Wireless Components Letters, IEEE》2005,15(7):448-450
A 24-GHz low-noise amplifier (LNA) was designed and fabricated in a standard 0.18-/spl mu/m CMOS technology. The LNA chip achieves a peak gain of 13.1 dB at 24 GHz and a minimum noise figure of 3.9 dB at 24.3 GHz. The supply voltage and supply current are 1 V and 14 mA, respectively. To the author's knowledge, this LNA demonstrates the lowest noise figure among the reported LNAs in standard CMOS processes above 20 GHz. 相似文献
998.
A shortcut model is developed for predicting the HETP of a structured packed distillation column operating at elevated pressure. The proposed model incorporates the geometrical parameters of the packing, physical properties of the vapor and liquid phases, and the hydrodynamics of the two‐phase flow. The proposed model is tested and validated by comparing the predicted results with the present experimental data and some published HETP data. The results show that the proposed model can predict the experimental data with a deviation smaller than 20 %. 相似文献
999.
1000.
介绍用原子吸收分光光度法测定PE、PP氯含量。该方法采用氧气燃烧法处理样品,用Ag~+沉淀Cl~-,经分离后用原子吸收光谱测溶液中剩余Ag~+浓度,从而得到样品中氯含量。讨论了仪器参数、操作条件对测定结果的影响,结果表明,在分离前存放4~30分钟对测试结果无影响。火焰法的测定条件为波长328.1nm、灯电流7.5mA、狭缝宽度0.4nm、C_2H_2压力0.025MPa、空气压0.16MPa、燃烧器高度7.5mm。实验采用的离心转速2000r/min、时间5分钟、HNO_3浓度1%。该法灵敏度可达0.1μg/ml、相对标准误差<2%。 相似文献