全文获取类型
收费全文 | 270762篇 |
免费 | 38296篇 |
国内免费 | 29420篇 |
专业分类
化学 | 139217篇 |
晶体学 | 2378篇 |
力学 | 12977篇 |
综合类 | 1485篇 |
数学 | 26205篇 |
物理学 | 78023篇 |
无线电 | 78193篇 |
出版年
2024年 | 938篇 |
2023年 | 5443篇 |
2022年 | 7491篇 |
2021年 | 9492篇 |
2020年 | 9381篇 |
2019年 | 8740篇 |
2018年 | 7972篇 |
2017年 | 7812篇 |
2016年 | 11031篇 |
2015年 | 11798篇 |
2014年 | 14550篇 |
2013年 | 18985篇 |
2012年 | 22024篇 |
2011年 | 22613篇 |
2010年 | 16664篇 |
2009年 | 16622篇 |
2008年 | 17527篇 |
2007年 | 16068篇 |
2006年 | 15238篇 |
2005年 | 13380篇 |
2004年 | 9868篇 |
2003年 | 8438篇 |
2002年 | 7895篇 |
2001年 | 6768篇 |
2000年 | 6041篇 |
1999年 | 6244篇 |
1998年 | 5279篇 |
1997年 | 4623篇 |
1996年 | 4804篇 |
1995年 | 4028篇 |
1994年 | 3645篇 |
1993年 | 3023篇 |
1992年 | 2725篇 |
1991年 | 2342篇 |
1990年 | 1856篇 |
1989年 | 1348篇 |
1988年 | 1080篇 |
1987年 | 858篇 |
1986年 | 806篇 |
1985年 | 671篇 |
1984年 | 501篇 |
1983年 | 404篇 |
1982年 | 306篇 |
1981年 | 205篇 |
1980年 | 156篇 |
1979年 | 81篇 |
1978年 | 79篇 |
1977年 | 69篇 |
1976年 | 74篇 |
1975年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
22.
23.
Lijuan Shen Li Li Sheng Lu Xiaohan Zhang Jie Liu Junlin An Guojun Zhang Bo Wu Fei Wang 《中国颗粒学报》2015,(3):10-15
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion. 相似文献
24.
研究了受外场驱动的两个二能级系统分别与两个单模量子化光场相互作用模型中纠缠演化及转移问题。该工作主要是对外场驱动的Landau-Zener模型进行了研究,采用旋转波近似的方法,通过数值计算详细分析了二能级系统初始状态、能级间的耦合常数以及驱动外场的参数对子系统间纠缠和转移特性的影响。结果表明,适当调节模型中的参数,可以使系统初始纠缠完全转移为光腔场间的纠缠,实现二能级系统与光场间的最大纠缠转移。 相似文献
25.
本文提出了将智能全站仪这种精密测量仪器广泛应用于田赛项目测量中,并结合其他科技元素用于解决田赛项目中跳远、投掷等项目的测量及数据管理问题,实现实时、自动、准确地裁定和报告比赛成绩。 相似文献
26.
Close‐Packed Two‐Dimensional Silver Nanoparticle Arrays: Quadrupolar and Dipolar Surface Plasmon Resonance Coupling 下载免费PDF全文
Sukang Yun Soonchang Hong Jesus A. I. Acapulco Jr. Ho Young Jang Songyi Ham Kyungeun Lee Prof. Seong Kyu Kim Prof. Sungho Park 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6165-6172
Silver nanoparticles (NPs) ranging in size from 40 to 100 nm were prepared in high yield by using an improved seed‐mediated method. The homogeneous Ag NPs were used as building blocks for 2D assembled Ag NP arrays by using an oil/water interface. A close‐packed 2D array of Ag NPs was fabricated by using packing molecules (3‐mercaptopropyltrimethoxysilane) to control the interparticle spacing. The homogeneous 2D Ag NP array exhibited a strong quadrupolar cooperative plasmon mode resonance and a dipolar red‐shift relative to individual Ag NPs suspended in solution. A well‐arranged 2D Ag NP array was embedded in polydimethylsiloxane film and, with biaxial stretching to control the interparticle distance, concomitant variations of the quadrupolar and dipolar couplings were observed. As the interparticle distance increased, the intensity of the quadrupolar cooperative plasmon mode resonance decreased and dipolar coupling completely disappeared. The local electric field of the 2D Ag NP array was calculated by using finite difference time domain simulation and qualitatively showed agreement with the experimental measurements. 相似文献
27.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of... 相似文献
28.
The research progress of a novel traffic solution,a submerged floating tunnel(SFT),is reviewed in terms of a study approach and loading scenario.Among existing publications,the buoyancy-weight ratio(BWR) is usually predefined.However,BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable system.In the context of a SFT prototype(SFTP) project in Qiandao Lake(Zhejiang Province,China),the importance of BWR is illustrated by finite element analysis and subsequently,an optimized BWR is proposed within a reasonable range in the present study.In the numerical model,structural damping is identified to be of importance.Rayleigh damping and the corresponding Rayleigh coefficients are attained through a sensitivity study,which shows that the adopted damping ratios are fairly suitable for SFTP.Lastly,the human sense of security is considered by quantifying the comfort index,which helps further optimize BWR in the SFTP structural parameter design. 相似文献
29.
30.