全文获取类型
收费全文 | 9436篇 |
免费 | 580篇 |
国内免费 | 627篇 |
专业分类
化学 | 9334篇 |
晶体学 | 14篇 |
力学 | 71篇 |
综合类 | 90篇 |
数学 | 123篇 |
物理学 | 1011篇 |
出版年
2024年 | 5篇 |
2023年 | 118篇 |
2022年 | 196篇 |
2021年 | 308篇 |
2020年 | 268篇 |
2019年 | 286篇 |
2018年 | 284篇 |
2017年 | 418篇 |
2016年 | 489篇 |
2015年 | 442篇 |
2014年 | 415篇 |
2013年 | 632篇 |
2012年 | 717篇 |
2011年 | 648篇 |
2010年 | 524篇 |
2009年 | 623篇 |
2008年 | 471篇 |
2007年 | 597篇 |
2006年 | 439篇 |
2005年 | 437篇 |
2004年 | 371篇 |
2003年 | 235篇 |
2002年 | 205篇 |
2001年 | 175篇 |
2000年 | 133篇 |
1999年 | 138篇 |
1998年 | 106篇 |
1997年 | 113篇 |
1996年 | 96篇 |
1995年 | 110篇 |
1994年 | 89篇 |
1993年 | 84篇 |
1992年 | 74篇 |
1991年 | 72篇 |
1990年 | 72篇 |
1989年 | 48篇 |
1988年 | 51篇 |
1987年 | 46篇 |
1986年 | 34篇 |
1985年 | 17篇 |
1984年 | 19篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1976年 | 1篇 |
1966年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
Summary A method for determining histamine in wine by precolumn derivatization with PITC (phenylisothiocyanate) with reversed-phase HPLC and UV detection is reported. Histamine can be determined together with the 24 amino acids within 40 min, or separately in a shorter time (less than 4 min) if a prior solid phase extraction clean-up is used. 相似文献
73.
Anna Rizzolo Patrizia Lombardi Maristella Vanoli Stefano Polesello 《Journal of separation science》1995,18(5):309-314
Capillary GC/sensory analysis was used to judge if dynamic headspace on sliced pulp and on intact fruit, and solvent extraction could collect the “character impact” and the “contributory” aroma compounds in peaches. Capillary GC/sensory data showed that the headspace techniques selectively recovered the “contributory” volatile compounds, which are strictly related to the characteristic odor of the various peach cultivars, whereas solvent extraction better quantified the “character impact” compounds (lactones). 相似文献
74.
俞是聃 《分析测试技术与仪器》2006,12(3):161-165
通过圆盘膜萃取提取河水中多环芳烃、多氯联苯,肽酸酯等半挥发有机物,并用气质联用仪及选择离子(SIM)进行样品定量分析,加标回收率在70%~130%之间,测定检出限达到pg/mL级(10-12)水平. 相似文献
75.
76.
Summary The application of capillary SFC for SIMDIST investigations of paraffins and waxes is reported. Pressure, density and temperature of the mobile phase are optimized to obtain high chromatographic resolution of complex mixtures of industrial products. Isothermal linear pressure programming and asymptotic pressure and density programming are used in the range from 15 to 35 MPa in the isothermic mode above 100°C. SFC chromatograms of natural and synthetic paraffins, microcrystalline wax and candle wax are compared. The retention behaviour of paraffin mixtures and waxes has been investigated on methyl/phenyl and biphenyl capillary columns. The polarity of the stationary phases influences the absolute retention time more than it influences the chromatographic resolution. 相似文献
77.
78.
将萃取与回流相结合, 建立了一种处理航空润滑油中磨损金属的新方法, 并用MPT全谱仪对磨损金属含量进行了同时检测. 该方法基本上实现了样品处理的全自动化,克服了常用方法的部分缺点, 对Zn, Cd, Cu, Fe和Pb的检出限(3σ)分别为0.084, 0.043, 0.022, 0.052和0.064 μg/g; 相对标准偏差均小于5%(n=5); 回收率为94.5%~107.4%. 对3个润滑油样品的检测结果令人满意. 相似文献
79.
80.
Ning Li Chunhui Deng Ning Yao Xizhong Shen Xiangmin Zhang 《Analytica chimica acta》2005,540(2):317-323
In the study, we developed a simple, rapid, sensitive, and inexpensive method for determination of the disease biomarkers of acetone, hexanal and heptanal in human blood. For the first time, derivatization of carbonyls with O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine (PFBHA) was combined with headspace single-drop microextractin (HS-SDME) and gas chromatography-mass spectrometry (GC–MS) and applied to the analysis of acetone, hexanal, and heptanal in human blood. At first, acetone, hexanal and heptanal in blood were derivatized with PFBHA and formed oximes in several seconds. Sequentially, the oximes were headspace extracted and concentrated by a microdrop solvent. Finally, the extracted oximes were analyzed by GC–MS. HS-SDME conditions and method validations were studied. Due to needing of only 2 μl organic solvent, short extraction time of 8 min, and simple operation, derivatization-HS-SDME was shown to be a rapid, simple, and inexpensive technique for analysis of acetone, hexanal, and heptanal in human blood. Moreover, it had low detection limit values from 0.24 to 0.62 nM, and good reproducibility (R.S.D. less than 12%). 相似文献