全文获取类型
收费全文 | 118324篇 |
免费 | 30503篇 |
国内免费 | 29513篇 |
专业分类
化学 | 78782篇 |
晶体学 | 2677篇 |
力学 | 7713篇 |
综合类 | 1836篇 |
数学 | 16322篇 |
物理学 | 71010篇 |
出版年
2024年 | 471篇 |
2023年 | 1018篇 |
2022年 | 1909篇 |
2021年 | 1885篇 |
2020年 | 2183篇 |
2019年 | 2725篇 |
2018年 | 2579篇 |
2017年 | 3581篇 |
2016年 | 3546篇 |
2015年 | 4348篇 |
2014年 | 4567篇 |
2013年 | 6970篇 |
2012年 | 7626篇 |
2011年 | 9444篇 |
2010年 | 12617篇 |
2009年 | 13121篇 |
2008年 | 7640篇 |
2007年 | 6647篇 |
2006年 | 6166篇 |
2005年 | 6026篇 |
2004年 | 6247篇 |
2003年 | 4956篇 |
2002年 | 4830篇 |
2001年 | 4994篇 |
2000年 | 4317篇 |
1999年 | 3737篇 |
1998年 | 2780篇 |
1997年 | 2501篇 |
1996年 | 2775篇 |
1995年 | 3210篇 |
1994年 | 3167篇 |
1993年 | 3232篇 |
1992年 | 2780篇 |
1991年 | 2374篇 |
1990年 | 2024篇 |
1989年 | 2092篇 |
1988年 | 2033篇 |
1987年 | 1320篇 |
1986年 | 1330篇 |
1985年 | 946篇 |
1984年 | 1087篇 |
1983年 | 473篇 |
1982年 | 959篇 |
1981年 | 792篇 |
1980年 | 818篇 |
1979年 | 568篇 |
1978年 | 556篇 |
1977年 | 649篇 |
1976年 | 1052篇 |
1972年 | 534篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Close‐Packed Two‐Dimensional Silver Nanoparticle Arrays: Quadrupolar and Dipolar Surface Plasmon Resonance Coupling
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
12.
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
13.
14.
15.
就标准厚度卡片在霍尔传感器的定标方面的应用作了有益的探讨。在纵向测量微小长度时,霍尔片处于磁场边缘位置,其对磁场的梯度更大,即灵敏度更高,且靠中心位置的线性更好。 相似文献
16.
This study is concerned with a new,explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode.As a departure from usual studies,here for the first time errors may be estimated and rendered minimal for all possible deformation modes and,furthermore,failure behavior may be incorporated.Numerical examples presented are in accurate agreement with Treloar's well-known data. 相似文献
17.
18.
19.
静止轨道卫星差分吸收光谱仪采用摆扫成像方式对大气进行探测,针对其工作时CCD成像系统信噪比大于1 000、高速探测模式下探测周期小于10min、高分辨率模式下探测周期小于1h的要求,进行CCD成像系统设计.选取CCD47-20作为探测器,设计成像电路实现光谱图像信号的采集和上传.分析了帧叠加和像元合并对时间、空间分辨率的影响.结合帧转移CCD的特点设计了每个位置最后一帧读出时摆镜转动的成像方式,并合理设置了帧叠加数和像元合并数,达到优化成像周期的目的.1s曝光时间条件下,该CCD成像系统的高速、高分辨率模式探测周期分别为515s和3 315s,图像信噪比均大于1 000,污染物观测实验中未出现失帧或重复的现象.该CCD成像系统方案满足静止轨道星载差分吸收光谱仪的探测需求,为静止轨道环境监测仪器设计提供参考. 相似文献
20.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献