全文获取类型
收费全文 | 6267篇 |
免费 | 304篇 |
国内免费 | 57篇 |
专业分类
化学 | 4678篇 |
晶体学 | 49篇 |
力学 | 155篇 |
综合类 | 1篇 |
数学 | 551篇 |
物理学 | 1194篇 |
出版年
2023年 | 29篇 |
2022年 | 67篇 |
2021年 | 113篇 |
2020年 | 112篇 |
2019年 | 132篇 |
2018年 | 91篇 |
2017年 | 81篇 |
2016年 | 219篇 |
2015年 | 184篇 |
2014年 | 248篇 |
2013年 | 387篇 |
2012年 | 459篇 |
2011年 | 503篇 |
2010年 | 316篇 |
2009年 | 276篇 |
2008年 | 412篇 |
2007年 | 345篇 |
2006年 | 342篇 |
2005年 | 332篇 |
2004年 | 271篇 |
2003年 | 252篇 |
2002年 | 251篇 |
2001年 | 126篇 |
2000年 | 119篇 |
1999年 | 61篇 |
1998年 | 46篇 |
1997年 | 61篇 |
1996年 | 71篇 |
1995年 | 49篇 |
1994年 | 48篇 |
1993年 | 64篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 43篇 |
1989年 | 52篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 27篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 11篇 |
1974年 | 19篇 |
1973年 | 11篇 |
排序方式: 共有6628条查询结果,搜索用时 15 毫秒
991.
S. Kar Y. K. Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):157-165
We have investigated the bound states and resonance states of
plasma-embedded tdμ and ddμ molecular ions using accurate
correlated basis functions. The plasma effect has been taken care of by
considering the Debye shielding approach of plasma modeling which admits a
variety of plasma conditions. The density of resonance states are calculated
using the stabilization method. The ground and excited states energies, and
the S-wave resonance energies of tdμ and ddμ molecular ions
immersed in plasmas are reported for various shielding parameters, along
with the 1S and 2S threshold energies of the tμ and dμ atoms. 相似文献
992.
Po‐Yu Lin Dai‐Ying Li Feng‐Hsien Ho Jian‐Hong Liao Subrat Kumar Barik C. W. Liu 《中国化学会会志》2019,66(9):988-995
A structural study of ligand exchange on chalcogen‐passivated copper nanoclusters is far less developed. Herein, we report the synthesis of polyhydrido copper nanoclusters [Cu20H11{Se2P(O iBu)2}9] ( 2 ) passivated by Se‐donor ligands via ligand replacement reaction on [Cu20H11{S2P(O iPr)2}9] ( 1 ) with NH4[Se2P(O iBu)2]. In parallel to the synthesis of 2 , cluster [Cu20H11{S2P(CH2CH2Ph)2}9] ( 4 ) was produced by the ligand exchange reaction on a new derivative of 1 , that is [Cu20H11{S2P(O nPr)2}9] ( 3 ). Solid state structures of both clusters 2 and 4 were unequivocally established by single‐crystal X‐ray diffraction studies and cluster 4 epitomizes exceptional case to preserve both the shape and size of the nanocluster during the course of ligand exchange. Structurally precise cluster 2 is the second example where the copper hydride nanocluster is stabilized by Se‐donor ligands. The anatomy of 2 can be visualized as a twisted cuboctahedral Cu13 core, two triangular faces of which are capped by a Cu6 cupola and a single Cu atom along the C3 rotational axis. 相似文献
993.
Marely E. Tejeda‐Ferrari Chelsea L. Brown Gabriela C. C. C. Coutinho Ghabriel A. Gomes de S Julio L. Palma Manuel J. Llansola‐Portoles Gerdenis Kodis Vladimiro Mujica Junming Ho Devens Gust Thomas A. Moore Ana L. Moore 《Photochemistry and photobiology》2019,95(1):211-219
Three Pd(II) phthalocyanine–carotenoid dyads featuring chromophores linked by amide bonds were prepared in order to investigate the rate of triplet–triplet (T‐T) energy transfer from the tetrapyrrole to the covalently attached carotenoid as a function of the number of conjugated double bonds in the carotenoid. Carotenoids having 9, 10 and 11 conjugated double bonds were studied. Transient absorption measurements show that intersystem crossing in the Pd(II) phthalocyanine takes place in 10 ps in each case and that T‐T energy transfer occurs in 126, 81 and 132 ps in the dyads bearing 9, 10 and 11 double bond carotenoids, respectively. To identify the origin of this variation in T‐T energy transfer rates, density functional theory (DFT) was used to calculate the T‐T electronic coupling in the three dyads. According to the calculations, the primary reason for the observed T‐T energy transfer trend is larger T‐T electronic coupling between the tetrapyrrole and the 10‐double bond carotenoid. A methyl group adjacent to the amide linker that connects the Pd(II) phthalocyanine and the carotenoid in the 9 and 11‐double bond carotenoids is absent in the 10‐double bond carotenoid, and this difference alters its electronic structure to increase the coupling. 相似文献
994.
Seonae Lee Dr. Ka Young Kim Prof. Sung Ho Jung Dr. Ji Ha Lee Dr. Mihoko Yamada Dr. Ramarani Sethy Prof. Tsuyoshi Kawai Prof. Jong Hwa Jung 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19054-19058
Finely controlled circularly polarized luminescence (CPL) supramolecular polymerization based on a tetraphenylethene core with four l ‐ or d ‐alanine branch side chains (l ‐ 1 and d ‐ 1 ) in the solution state is presented, resulting from the tuning of mechanical stimulus. Weak, green emissions of l ‐ 1 and d ‐ 1 in tetrahydrofuran (THF) were converted into strong blue emissions by tuning the mechanical stimulus. The strong blue emissions were caused by an aggregation‐induced emission (AIE) effect during the formation of a supramolecular polymer. Lag time in the supramolecular polymerization was drastically reduced by the mechanical stimulus, which was indicative of the acceleration of the supramolecular polymerization. A significant enhancement of circular dichroism (CD) and CPL signals of l ‐ 1 and d ‐ 1 was observed by tuning the rotational speed of the mechanical stimulus, implying that the chiral supramolecular polymerization was accelerated by the mechanical stimulus. 相似文献
995.
Sekimoto Shun Homura Yuta Ho Van Doanh Inagaki Makoto Shirai Naoki Ohtsuki Tsutomu 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1579-1583
Journal of Radioanalytical and Nuclear Chemistry - Two kinds of carbonate reference materials, coral (JCp-1) and giant clam (JCt-1), were subjected to neutron activation analysis (NAA) using the... 相似文献
996.
Ra You Wongi Park Eric Carlson Seong Ho Ryu Min Jeong Shin Edward Guzman 《Liquid crystals》2019,46(2):316-325
We produced controlled heliconical structures of a twist-bend nematic (NTB) liquid-crystal (LC) phase in nanoconfinement in a porous anodic aluminium oxide (AAO) film. The structural parameters of the NTB phase such as conical angle and helical pitch can be modulated by varying the surface energy of the inner surface of the porous AAO film, done by using different self-assembled monolayers (SAMs). The LC molecules tend to be more freely packed, thus forming a larger conical angle, when placed on the tri-deca-fluoro-1,1,2,2-tetrahydrooctyl-trichlorosilane (FOTS)-treated substrate, which has a relatively low surface energy. In contrast, the molecules form a more tightly packed structure, and thus a smaller conical angle, when placed on the 2-(methoxy(polyethyleneoxy)-propyl)trimethoxysilane (PEG 6/9)-treated substrate, which has higher surface energy. This work improves our collective understanding of self-assembled heliconical structures in the NTB phase. 相似文献
997.
998.
Ae Kim S Min Byun K Lee J Hoon Kim J Albert Kim DG Baac H Shuler ML June Kim S 《Optics letters》2008,33(9):914-916
We demonstrate that surface plasmon resonance (SPR) is applicable to the optical detection of neural signals. A low-noise SPR sensor was developed as a label- and artifact-free method for the extracellular recording of neural activity. The optical responses obtained from a rat sciatic nerve were highly correlated with simultaneously recorded electrical responses. Additional studies with stimulation intensity and lidocaine further confirmed that the optically measured signals originated from neural activities. 相似文献
999.
Sensitive and automated detection of iron-oxide-labeled cells using phase image cross-correlation analysis 总被引:2,自引:1,他引:1
Superparamagnetic iron oxide (SPIO) nanoparticles are increasingly being used to noninvasively track cells, target specific molecules and monitor gene expression in vivo. Contrast changes that are subtle relative to intrinsic sources of contrast present a significant detection challenge. Here, we describe a postprocessing algorithm, called Phase map cross-correlation Detection and Quantification (PDQ), with the purpose of automating identification and quantification of localized accumulations of SPIO agents. The method is designed to sacrifice little flexibility - it works on previously acquired data and allows the use of conventional high-SNR pulse sequences with no extra scan time. We first investigated the theoretical detection limits of PDQ using a simulated dipole field. This method was then applied to three-dimensional (3D) MRI data sets of agarose gel containing isolated dipoles and ex vivo transplanted allogenic rat hearts infiltrated by numerous iron-oxide-labeled macrophages as a result of organ rejection. A simulated dipole field showed this method to be robust in very low signal-to-noise ratio images. Analysis of agarose gel and allogenic rat heart shows that this method can automatically identify and count dipoles while visualizing their biodistribution in 3D renderings. In the heart, this information was used to calculate a quantitative index that may indicate its degree of cellular infiltration. 相似文献
1000.
Hans M. Christen Dae Ho Kim Christopher M. Rouleau 《Applied Physics A: Materials Science & Processing》2008,93(3):807-811
Recent advances in film synthesis have made it possible to investigate the properties of well-controlled interfaces in perovskite
metal-oxides. A review of published experimental data and computational results indicate that so far most interfaces that
have been analyzed in ferroelectric materials—while necessary to impose large lattice strain on the polar material—contribute
little to the ferroelectricity and may instead be detrimental to the desired properties. In contrast, a very different situation
arises at interfaces that show changes in the electronic configuration as a consequence of a compositional discontinuity.
Data is shown for LaMnO3/SrTiO3 superlattices as an example of electronic effects that produce enhanced properties, further illustrating the richness of
interfacial properties that can be obtained at interfaces (as shown in numerous published results for different but related
interfaces). 相似文献