全文获取类型
收费全文 | 1195篇 |
免费 | 83篇 |
国内免费 | 4篇 |
专业分类
化学 | 999篇 |
晶体学 | 9篇 |
力学 | 7篇 |
数学 | 99篇 |
物理学 | 168篇 |
出版年
2023年 | 11篇 |
2022年 | 10篇 |
2021年 | 26篇 |
2020年 | 38篇 |
2019年 | 53篇 |
2018年 | 33篇 |
2017年 | 25篇 |
2016年 | 50篇 |
2015年 | 42篇 |
2014年 | 65篇 |
2013年 | 70篇 |
2012年 | 93篇 |
2011年 | 103篇 |
2010年 | 40篇 |
2009年 | 35篇 |
2008年 | 75篇 |
2007年 | 64篇 |
2006年 | 73篇 |
2005年 | 72篇 |
2004年 | 67篇 |
2003年 | 42篇 |
2002年 | 39篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 11篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有1282条查询结果,搜索用时 15 毫秒
51.
The acceptable range of speech level as a function of background noise level was investigated on the basis of word intelligibility scores and listening difficulty ratings. In the present study, the acceptable range is defined as the range that maximizes word intelligibility scores and simultaneously does not cause a significant increase in listening difficulty ratings from the minimum ratings. Listening tests with young adult and elderly listeners demonstrated the following. (1) The acceptable range of speech level for elderly listeners overlapped that for young listeners. (2) The lower limit of the acceptable speech level for both young and elderly listeners was 65 dB (A-weighted) for noise levels of 40 and 45 dB (A-weighted), a level with a speech-to-noise ratio of +15 dB for noise levels of 50 and 55 dB, and a level with a speech-to-noise ratio of +10 dB for noise levels from 60 to 70 dB. (3) The upper limit of the acceptable speech level for both young and elderly listeners was 80 dB for noise levels from 40 to 55 dB and 85 dB or above for noise levels from 55 to 70 dB. 相似文献
52.
53.
54.
Yoshida R Sakai T Ito S Yamaguchi T 《Journal of the American Chemical Society》2002,124(27):8095-8098
Self-oscillation of polymer chains in an aqueous solution has been achieved. The ruthenium catalyst for the Belousov-Zhabotinsky reaction was polymerized by using N-isopropylacrylamide and dissolved into the solution containing the BZ substrates. Periodical soluble-insoluble changes of the polymer chain were spontaneously induced by the BZ reaction. The conformational oscillations of the polymer were measured as the optical transmittance changes of the solution. This is the first report that rhythmical and reversible soluble-insoluble changes of polymer chains are realized under constant and homogeneous conditions. The transducing system from chemical energy of the BZ reaction to optical information has been constructed. 相似文献
55.
We report the results of in situ AFM measurements examining the phase transition of bilayers formed from the zwitterionic phospholipid, DMPC, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, supported on mica. The images show that the fluid to gel phase transition process features substantial tearing of the bilayer due to the density change between the two phases. The gel to fluid transition is strongly affected by the resultant stress introduced into the gel phase, which changes the degree of cooperativity, the shape of developing fluid phase regions, and the course of the transition. 相似文献
56.
57.
58.
Terao K Ohsawa A Mori Y Narita T Ichikawa K Dobashi T 《Colloids and surfaces. B, Biointerfaces》2004,37(3-4):129-132
Microcapsules having polyethyleneglycol-grafted poly(ureaurethane) (PUU) membrane and di-2ethylhexyl phthalate core have been prepared, and the structure when they were suspended in dispersing ethanol have been studied by means of single-particle light scattering method. The PUU membrane was synthesized from monomers with aromatic functional groups (microcapsule MC110) and hexamethylene functional groups (microcapsule MC160). Because the outer and inner solvent passed through the membrane easily, the outside and inside of the membrane were the same at the equilibrium state. The thickness of the wall membrane was significantly smaller than that calculated from the overall weight ratio of the wall-forming material and the core solvents. It was attributed to low affinity of PUU membranes and ethanol. 相似文献
59.
The synthesis, crystal structures, inclusion ability, and structural robustness of novel crystalline inclusion compounds of [Ni(SCN)2(isoH)2].xG (isoH = isonicotinic acid; G = aromatic guest) are described. The inclusion compounds are constructed by stacking identical 2D host layers that consist of SCN-, isoH, and Ni2+ with van der Waals contact separation. In the layer, two types of rectangular cavities (A-type and B-type) are formed, and the guests are included in the former cavity. The inclusion compounds were categorized into four stacking modes according to the difference in the stacking mode of the layers. A systematic investigation of the crystal structures of the 21 inclusion compounds clarified the close relationship between the molecular structure of the guest and the resultant stacking mode of the layers. 相似文献
60.
[reaction: see text] A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to fumaric and maleic compounds has been developed. While phosphorus-based chiral ligands fail to induce high stereoselectivity, chiral norbornadiene ligands have proved to be uniquely effective to achieve high enantioselectivity in these 1,4-addition reactions. 相似文献