全文获取类型
收费全文 | 244359篇 |
免费 | 4807篇 |
国内免费 | 2025篇 |
专业分类
化学 | 134233篇 |
晶体学 | 4095篇 |
力学 | 10253篇 |
综合类 | 101篇 |
数学 | 24162篇 |
物理学 | 78347篇 |
出版年
2021年 | 2182篇 |
2020年 | 2506篇 |
2019年 | 2638篇 |
2018年 | 3113篇 |
2017年 | 3100篇 |
2016年 | 4648篇 |
2015年 | 3118篇 |
2014年 | 4830篇 |
2013年 | 11362篇 |
2012年 | 8796篇 |
2011年 | 10649篇 |
2010年 | 7619篇 |
2009年 | 7495篇 |
2008年 | 9191篇 |
2007年 | 9075篇 |
2006年 | 8500篇 |
2005年 | 7578篇 |
2004年 | 6854篇 |
2003年 | 6241篇 |
2002年 | 5938篇 |
2001年 | 7458篇 |
2000年 | 5634篇 |
1999年 | 4456篇 |
1998年 | 3526篇 |
1997年 | 3392篇 |
1996年 | 3235篇 |
1995年 | 3040篇 |
1994年 | 2893篇 |
1993年 | 2662篇 |
1992年 | 3346篇 |
1991年 | 3268篇 |
1990年 | 3197篇 |
1989年 | 3138篇 |
1988年 | 3172篇 |
1987年 | 3151篇 |
1986年 | 2955篇 |
1985年 | 3740篇 |
1984年 | 3744篇 |
1983年 | 2916篇 |
1982年 | 3057篇 |
1981年 | 3103篇 |
1980年 | 2826篇 |
1979年 | 3184篇 |
1978年 | 3149篇 |
1977年 | 3281篇 |
1976年 | 3133篇 |
1975年 | 2831篇 |
1974年 | 2763篇 |
1973年 | 2726篇 |
1968年 | 1941篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Nonlinear Dynamics - With an increasing number of people sharing feelings and opinions online, the online platforms have become one of the most important channels for public opinion dissemination.... 相似文献
34.
35.
K.V. Stepurska О.О. Soldatkin I.S. Kucherenko V.M. Arkhypova S.V. Dzyadevych A.P. Soldatkin 《Analytica chimica acta》2015
This study was aimed at the development of a conductometric biosensor based on acetylcholinesterase considering the feasibility of its application for the inhibitory analysis of various toxicants. In this paper, the optimum conditions for enzyme immobilization on the transducer surface are selected as well as the optimum concentration of substrate for inhibitory analysis. Sensitivity of the developed biosensor to different classes of toxic compounds (organophosphorus pesticides, heavy metal ions, surfactants, aflatoxin, glycoalkaloids) was tested. It is shown that the developed biosensor can be successfully used for the analysis of pesticides and mycotoxins, as well as for determination of total toxicity of the samples. A new method of biosensor analysis of toxic substances of different classes in complex multicomponent aqueous samples is proposed. 相似文献
36.
Su X. F. Zhang Y. L. Maximov A. L. Zhang K. Xin Q. Feng C. Q. Bai X. F. Wu W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,... 相似文献
37.
Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon(WIRC) component of total suspended particulates(TSP),collected weekly during 2003,as well as from October 2005 to May 2006 at the WMO-GAW Mt.Waliguan(WLG) site.The overall average WIRC mass concentration was(1183±120)ng/m3(n = 79),while seasonal averages were 2081 ±1707(spring),454±205(summer),650±411(autumn),and 1019±703(winter) ng/m3.Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer,although WIRC concentrations were typically higher,especially in winter and spring.The δ13C PDB value(-25.3 ± 0.8)%.determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion.No seasonal change in δ13C PDB was evident.The average percent Modern Carbon(pMC) for 14C in WIRC for winter and spring was(67.2 ± 7.7)%(n = 29).Lower pMC values were associated with air masses transported from the area east of WLG,while higher pMC values were associated with air masses from the Tibetan Plateau,southwest of WLG.Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event. 相似文献
38.
Journal of Sol-Gel Science and Technology - Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties... 相似文献
39.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented. 相似文献
40.
Farsi R. Mohammadi M. K. Saghanezhad S. J. 《Russian Journal of Organic Chemistry》2021,57(12):2002-2009
Russian Journal of Organic Chemistry - Herein, we report the sulfonamide-functionalized covalent organic framework (COF-SO3H), prepared by condensation of melamine and terephthalaldehyde and... 相似文献