全文获取类型
收费全文 | 27355篇 |
免费 | 1018篇 |
国内免费 | 168篇 |
专业分类
化学 | 18183篇 |
晶体学 | 279篇 |
力学 | 795篇 |
数学 | 2714篇 |
物理学 | 6570篇 |
出版年
2023年 | 150篇 |
2022年 | 294篇 |
2021年 | 612篇 |
2020年 | 475篇 |
2019年 | 486篇 |
2018年 | 432篇 |
2017年 | 416篇 |
2016年 | 781篇 |
2015年 | 691篇 |
2014年 | 924篇 |
2013年 | 1639篇 |
2012年 | 1938篇 |
2011年 | 2208篇 |
2010年 | 1393篇 |
2009年 | 1194篇 |
2008年 | 1842篇 |
2007年 | 1611篇 |
2006年 | 1652篇 |
2005年 | 1387篇 |
2004年 | 1247篇 |
2003年 | 1062篇 |
2002年 | 988篇 |
2001年 | 614篇 |
2000年 | 553篇 |
1999年 | 390篇 |
1998年 | 252篇 |
1997年 | 251篇 |
1996年 | 320篇 |
1995年 | 227篇 |
1994年 | 236篇 |
1993年 | 233篇 |
1992年 | 184篇 |
1991年 | 143篇 |
1990年 | 161篇 |
1989年 | 132篇 |
1988年 | 94篇 |
1987年 | 96篇 |
1986年 | 70篇 |
1985年 | 118篇 |
1984年 | 78篇 |
1983年 | 63篇 |
1982年 | 91篇 |
1981年 | 88篇 |
1980年 | 55篇 |
1979年 | 80篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 63篇 |
1975年 | 56篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
951.
952.
953.
954.
955.
Straub PB Jaffe DE Glass HD Adams MR Brown CN Charpak G Cooper WE Crittenden JA Finley DA Gray R Hemmi Y Hsiung YB Hubbard JR Jonckheere AM Jöstlein H Kaplan DM Lederman LM Luk KB Maki A Mangeot P McCarthy RL Miyake K Plaag RE Rutherfoord JP Sakai Y Santiard JC Sauli F Smith SR Yoshida T Young KK 《Physical review letters》1992,68(4):452-455
956.
957.
958.
Li4Ti5O12 thin films for rechargeable lithium batteries were prepared by a sol-gel method with poly(vinylpyrrolidone). Interfacial properties of lithium insertion into Li4Ti5O12 thin film were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiostatic intermittent titration technique (PITT). Redox peaks in CV were very sharp even at a fast scan rate of 50 mV s−1, indicating that Li4Ti5O12 thin film had a fast electrochemical response, and that an apparent chemical diffusion coefficient of Li+ ion was estimated to be 6.8×10−11 cm2 s−1 from a dependence of peak current on sweep rates. From EIS, it can be seen that Li+ ions become more mobile at 1.55 V vs. Li/Li+, corresponding to a two-phase region, and the chemical diffusion coefficients of Li+ ion ranged from 10−10 to 10−12 cm2 s−1 at various potentials. The chemical diffusion coefficients of Li+ ion in Li4Ti5O12 were also estimated from PITT. They were in a range of 10−11-10−12 cm2 s−1. 相似文献
959.
A polyacrylonitrile (PAN) fiber was adopted for the backbone of a chelate polymer and poly(acrylo‐amidino ethylene amine) (PAEA) was prepared through a one‐step reaction between the PAN fiber and ethylenediamine (EDA). The maximum removal capacity and degree of substitution were 7.8 meq per gram of dried PAEA and 98%, respectively. The PAEA was tested as an adsorbent in single and two‐component metal aqueous solutions under changing pH. The Cu2+ ion accomplished maximum adsorption amount at pH 3 and the order of maximum adsorbed amounts on PAEA is Cu2+ > Ag+ > Zn2+ > Ni2+ > Pb2+ in molar basis. FT‐IR spectroscopy was employed to characterize the chemical bonding in metal aqueous solutions and surface morphology was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
960.
A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME). 相似文献