全文获取类型
收费全文 | 5083篇 |
免费 | 871篇 |
国内免费 | 738篇 |
专业分类
化学 | 3326篇 |
晶体学 | 160篇 |
力学 | 249篇 |
综合类 | 94篇 |
数学 | 826篇 |
物理学 | 2037篇 |
出版年
2024年 | 7篇 |
2023年 | 81篇 |
2022年 | 108篇 |
2021年 | 160篇 |
2020年 | 208篇 |
2019年 | 192篇 |
2018年 | 196篇 |
2017年 | 206篇 |
2016年 | 251篇 |
2015年 | 238篇 |
2014年 | 264篇 |
2013年 | 386篇 |
2012年 | 490篇 |
2011年 | 460篇 |
2010年 | 389篇 |
2009年 | 383篇 |
2008年 | 404篇 |
2007年 | 372篇 |
2006年 | 316篇 |
2005年 | 253篇 |
2004年 | 180篇 |
2003年 | 158篇 |
2002年 | 197篇 |
2001年 | 168篇 |
2000年 | 118篇 |
1999年 | 87篇 |
1998年 | 51篇 |
1997年 | 35篇 |
1996年 | 44篇 |
1995年 | 31篇 |
1994年 | 37篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1980年 | 2篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有6692条查询结果,搜索用时 15 毫秒
991.
SUN Xiao-yan LI Jian-wei LI Ying-xia YAN Shi-cheng CHEN Biao-hua . State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing P. R. China . Jilin Vocational College of Industry Technology Jilin 《高等学校化学研究》2009,25(3)
The adsorption behavior of benzene and propylene in zeolite ZSM-5 was studied by Grand Canonical Monte Carlo(GCMC) simulations. It could be found that benzene and propylene molecules showed different adsorption behavior in the zeolite cavities. The loadings of propylene were significantly larger than those of benzene at 100 kPa. From the figures of potential energy distribution,the potential energy of benzene/zeolite was more negative than that of propylene/zeolite,so benzene could be adsorbed more stably t... 相似文献
992.
993.
LingShu Wan BeiBei Ke XiaoKai Li XiangLin Meng LuYao Zhang ZhiKang Xu 《中国科学B辑(英文版)》2009,52(7):969-974
Highly ordered honeycomb-patterned polystyrene (PS)/poly(ethylene glycol) (PEG) films were prepared by a water-assisted method
using an improved setup, which facilitated the formation of films with higher regularity, better reproducibility, and larger
area of honeycomb structures. Surface aggregation of hydrophilic PEG and adsorption of bovine serum albumin (BSA) on the honeycomb-patterned
films were investigated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to
observe the surface morphologies of the films before and after being rinsed with water. As confirmed by the FESEM images and
the AFM phase images, PEG was enriched in the pores and could be gradually removed by water. The adsorption of fluorescence-labeled
BSA on the films was studied in visual form using laser scanning confocal microscopy. Results clearly demonstrated that the
protein-resistant PEG was selectively enriched in the pores. This water-assisted method may be a latent tool to prepare honeycomb-patterned
biofunctional surfaces.
Supported by the National Natural Science Foundation of China (Grant No. 50803053), the National Natural Science Foundation
of China for Distinguished Young Scholars (Grant No. 50625309), the National Postdoctoral Science Foundation of China (Grant
Nos. 20070421172 & 20081466) and the National Undergraduate Innovative Test Program 相似文献
994.
Yan-Hua Cui Ming-Zhe Xue Xiao-Lin Wang Ke Hu Zheng-Wen Fu 《Electrochemistry communications》2009,11(5):1045-1047
InP thin film has been successfully fabricated by pulsed laser deposition (PLD) and was investigated for its electrochemistry with lithium for the first time. InP thin film presented a large reversible discharge capacity around 620 mAh g?1. The reversibility of the crystalline structure and electrochemical reaction of InP with lithium were revealed by using ex situ XRD and XPS measurements. The high reversible capacity and stable cycle of InP thin film electrode with low overpotential made it one of the promise energy storage materials for future rechargeable lithium batteries. 相似文献
995.
Yong Yan Ke Deng Prof. Zai Yu Zhixiang Wei Prof. 《Angewandte Chemie (International ed. in English)》2009,48(11):2003-2006
A game of Twister : The induced helicity of polyaniline and its supramolecular structures could be tuned by the methyl substitution of one of the monomers. By copolymerization of aniline with m‐toluidine, the helicity of copolymer (PMANI) nanofibers was totally inverted compared to that of polyaniline (PANI), while copolymer nanofibers with o‐toluidine (POANI) had the same helicity as that of polyaniline (see picture).
996.
Carla Bittencourt Dr. Gregory Van Lier Dr. Xiaoxing Ke Irene Suarez‐Martinez Dr. Alexandre Felten Dr. Jacques Ghijsen Dr. Gustaaf Van Tendeloo Prof. Christopher P. Ewels Dr. 《Chemphyschem》2009,10(6):920-925
Finely tuned: Carbon nanotubes are exposed to a CF4 radio‐frequency plasma (see picture). High‐resolution photoelectron spectroscopy shows that the treatment effectively grafts fluorine atoms onto the MWCNTs, altering the valence electronic states. Fluorine surface concentration can be tuned by varying the exposure time.
997.
Zhen-Dan Shi Omid Motabar Ehud Goldin Ke Liu Noel Southall Ellen Sidransky Christopher P. Austin Gary L. Griffiths Wei Zheng 《Analytical and bioanalytical chemistry》2009,394(7):1903-1909
Alpha-galactosidase A hydrolyzes the terminal alpha-galactosyl moieties from glycolipids and glycoproteins in lysosomes. Mutations
in α-galactosidase cause lysosomal accumulation of the glycosphingolipid, globotriaosylceramide, which leads to Fabry disease.
Small-molecule chaperones that bind to mutant enzyme proteins and correct their misfolding and mistrafficking have emerged
as a potential therapy for Fabry disease. We have synthesized a red fluorogenic substrate, resorufinyl α-d-galactopyranoside, for a new α-galactosidase enzyme assay. This assay can be measured continuously at lower pH values, without
the addition of a stop solution, due to the relatively low pK
a of resorufin (~6). In addition, the assay emits red fluorescence, which can significantly reduce interferences due to compound
fluorescence and dust/lint as compared to blue fluorescence. Therefore, this new red fluorogenic substrate and the resulting
enzyme assay can be used in high-throughput screening to identify small-molecule chaperones for Fabry disease.
Zhen-Dan Shi and Omid Motabar contributed equally to this work 相似文献
998.
Yun‐Peng Diao Kun Li Shan‐Shan Huang Xiao‐Hong Shu Ke‐Xin Liu Xu‐Ming Deng 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(2):m82-m85
In the mixed‐ligand metal–organic polymeric compound poly[[μ2‐1,4‐bis(imidazol‐1‐yl)benzene](μ2‐terephthalato)dizinc(II)], [Zn2(C8H4O4)2(C12H10N4)]n or [Zn2(bdc)2(bib)]n [H2bdc is terephthalic acid and bib is 1,4‐bis(imidazol‐1‐yl)benzene], the asymmetric unit contains one ZnII ion, with two half bdc anions and one half bib molecule lying around inversion centers. The ZnII ion is in a slightly distorted tetrahedral environment, coordinated by three carboxylate O atoms from three different bdc anions and by one bib N atom. The crystal structure is constructed from the secondary building unit (SBU) [Zn2(CO2)2N2O2], in which the two metal centers are held together by two bdc linkers with bis(syn,syn‐bridging bidentate) bonding modes. The SBU is connected by bdc bridges to form a two‐dimensional grid‐like (4,4)‐layer, which is further pillared by the bib ligand. Topologically, the dinuclear SBU can be considered to be a six‐connected node, and the extended structure exhibits an elongated primitive approximately cubic framework. The three‐dimensional framework possesses a large cavity with dimensions of approximately 10 × 13 × 17 Å in cross‐section. The potential porosity is filled with mutual interpenetration of two identical equivalent frameworks, generating a novel threefold interpenetrating network with an α‐polonium topology [Abrahams, Hoskins, Robson & Slizys (2002). CrystEngComm, 4 , 478–482]. 相似文献
999.
Three kinds of novel indium oxide (In2O3) nanostructures, namely, nanorods, nanoflowers and nanowhiskers were synthesized on silicon substrate via a simple vapor‐phase transport method under atmospheric pressure. The In2O3nanostructures were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy‐dispersive X‐ray spectrometer (EDS) spectrum. The Raman spectra of these nanostructures showed four sharp scattering peaks centered at 308, 365, 522, and 628 cm‐1, whose position and intensity were characteristic of standard Raman spectra for In2O3. The Room‐temperature photoluminescence (PL) spectra showed visible emissions centered around 576, 592, and 624 nm. Field emission measurements demonstrated that the nanoflowers possessed the best performance with a turn‐on field of 3.54 V/µm and a threshold field of 9.83 V/µm. And the field enhancement factors of these nanostructures are high enough for the application of field emission display devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
This paper discusses a discrete-time Geo/G/1 queue, in which the server operates a random threshold policy, namely 〈p, N〉 policy, at the end of each service period. After all the messages are served in the queue exhaustively, the server is immediately deactivated until N messages are accumulated in the queue. If the number of messages in the queue is accumulated to N, the server is activated for services with probability p and deactivated with probability (1 − p). Using the generating functions technique, the system state evolution is analyzed. The generating functions of the system size distributions in various states are obtained. Some system characteristics of interest are derived. The long-run average cost function per unit time is analytically developed to determine the joint optimal values of p and N at a minimum cost. 相似文献