全文获取类型
收费全文 | 217394篇 |
免费 | 4174篇 |
国内免费 | 1908篇 |
专业分类
化学 | 121235篇 |
晶体学 | 3798篇 |
力学 | 8996篇 |
综合类 | 106篇 |
数学 | 21083篇 |
物理学 | 68258篇 |
出版年
2021年 | 1833篇 |
2020年 | 2191篇 |
2019年 | 2346篇 |
2018年 | 2622篇 |
2017年 | 2718篇 |
2016年 | 4096篇 |
2015年 | 2744篇 |
2014年 | 4262篇 |
2013年 | 10052篇 |
2012年 | 7675篇 |
2011年 | 9280篇 |
2010年 | 6483篇 |
2009年 | 6505篇 |
2008年 | 8153篇 |
2007年 | 7994篇 |
2006年 | 7575篇 |
2005年 | 6883篇 |
2004年 | 6190篇 |
2003年 | 5592篇 |
2002年 | 5332篇 |
2001年 | 6487篇 |
2000年 | 4923篇 |
1999年 | 3856篇 |
1998年 | 3080篇 |
1997年 | 2987篇 |
1996年 | 2881篇 |
1995年 | 2678篇 |
1994年 | 2595篇 |
1993年 | 2347篇 |
1992年 | 2997篇 |
1991年 | 2868篇 |
1990年 | 2825篇 |
1989年 | 2786篇 |
1988年 | 2803篇 |
1987年 | 2815篇 |
1986年 | 2683篇 |
1985年 | 3393篇 |
1984年 | 3378篇 |
1983年 | 2646篇 |
1982年 | 2759篇 |
1981年 | 2809篇 |
1980年 | 2565篇 |
1979年 | 2904篇 |
1978年 | 2889篇 |
1977年 | 3005篇 |
1976年 | 2836篇 |
1975年 | 2576篇 |
1974年 | 2526篇 |
1973年 | 2482篇 |
1972年 | 1712篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
31.
Lijuan Shen Li Li Sheng Lu Xiaohan Zhang Jie Liu Junlin An Guojun Zhang Bo Wu Fei Wang 《中国颗粒学报》2015,(3):10-15
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion. 相似文献
32.
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
33.
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
34.
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
35.
Journal of Computer-Aided Molecular Design - Accurate predictions of acid dissociation constants are essential to rational molecular design in the pharmaceutical industry and elsewhere. There has... 相似文献
36.
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
37.
38.
39.
Rajkumar P. Diwakar K. Subadevi R. Gnanamuthu R. M. Wang Fu-Ming Liu Wei-Ren Sivakumar M. 《Journal of Solid State Electrochemistry》2021,25(3):939-948
Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To... 相似文献
40.
Journal of Thermal Analysis and Calorimetry - Low productivity of single-slope solar still is the main barrier for its worldwide usability. An attempt has been conducted to enhance the distillate... 相似文献