全文获取类型
收费全文 | 23245篇 |
免费 | 707篇 |
国内免费 | 61篇 |
专业分类
化学 | 14931篇 |
晶体学 | 378篇 |
力学 | 720篇 |
综合类 | 1篇 |
数学 | 1791篇 |
物理学 | 6192篇 |
出版年
2023年 | 237篇 |
2022年 | 572篇 |
2021年 | 530篇 |
2020年 | 591篇 |
2019年 | 710篇 |
2018年 | 647篇 |
2017年 | 629篇 |
2016年 | 919篇 |
2015年 | 640篇 |
2014年 | 1058篇 |
2013年 | 1908篇 |
2012年 | 1552篇 |
2011年 | 1689篇 |
2010年 | 1100篇 |
2009年 | 932篇 |
2008年 | 1118篇 |
2007年 | 1088篇 |
2006年 | 867篇 |
2005年 | 748篇 |
2004年 | 598篇 |
2003年 | 465篇 |
2002年 | 417篇 |
2001年 | 252篇 |
2000年 | 240篇 |
1999年 | 186篇 |
1998年 | 125篇 |
1997年 | 154篇 |
1996年 | 184篇 |
1995年 | 173篇 |
1994年 | 163篇 |
1993年 | 184篇 |
1992年 | 222篇 |
1991年 | 157篇 |
1990年 | 146篇 |
1989年 | 161篇 |
1988年 | 139篇 |
1987年 | 138篇 |
1986年 | 118篇 |
1985年 | 166篇 |
1984年 | 184篇 |
1983年 | 137篇 |
1982年 | 143篇 |
1981年 | 135篇 |
1980年 | 142篇 |
1979年 | 148篇 |
1978年 | 152篇 |
1977年 | 138篇 |
1976年 | 96篇 |
1975年 | 92篇 |
1974年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Duboscq JE Elliott JR Escobar CO Gibney MC Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Ong P Pinfold J Punkar G Purohit MV Santoro AF Sidhu JS Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundia AB Witherell MS 《Physical review letters》1990,64(24):2885-2888
82.
83.
84.
85.
86.
87.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Elliott JR Escobar CO Estabrooks P Gibney MC Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Nauenberg U Ong P Pinfold J Punkar G Purohit MV Raab JR Santoro AF Sidhu JS Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundia AB Witherell MS 《Physical review letters》1988,60(14):1379-1381
88.
M. E. Wrenn H. Ruth D. Burleigh N. P. Singh 《Journal of Radioanalytical and Nuclear Chemistry》1992,156(2):407-412
The literature on the normal content of uranium in urine is reviewed. The reported normal concentration has declined several orders of magnitude over the years, probably due to improvements in analytical technique rather than a real change. The lowest mean values were reported with spectrometry (mean of 23 ng/l in 12 subjects) and thermal ion mass spectrometry (3.4 ng/l in 1 subject). Even spectrometry is not sufficiently sensitive at normal levels, so that techniques such as fission track analysis or mass spectrometry must be used to obtain results above the detection limit of the technique for individual samples. 相似文献
89.
Thiosalicylic acid (TSA)-modified Amberlite XAD-2 (AXAD-2) was synthesized by coupling TSA with the support matrix AXAD-2 through an azo spacer. The resulting chelating resin was characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared spectra. The newly designed resin quantitatively sorbs CdII, CoII, CuII, FeIII, NiII and ZnII at pH 3.5-7.0 when the flow rate is maintained between 2 and 4 ml min-1. The HCl or HNO3 (2 mol l-1) instantaneously elutes all the metal ions. The sorption capacity is 197.5, 106.9, 214.0, 66.2, 309.9 and 47.4 mumol g-1 of the resin for cadmium, cobalt, copper, iron, nickel and zinc, respectively, whereas their preconcentration factor is between 180-400. The breakthrough volume of HCl or HNO3 for elution of these metal ions was found to be 4-8 ml. The limit of detection (LOD) for CdII, CoII, CuII, FeIII, NiII and ZnII was 0.48, 0.20, 4.05, 0.98, 1.28 and 3.94 micrograms l-1, respectively, and the limit of quantification (LOQ) was found to be 0.51, 0.29, 4.49, 1.43, 1.58 and 4.46 micrograms l-1, respectively. The loading half time, t1/2, for the cations was found to be less than 2.0 min, except for nickel for which the value was 13.1 min. The determination of each of these six cations is possible in the presence of other five, if their concentration is up to 4 times. All six metals were determined in river water (RSD approximately 0.7-7.7%) and tap water samples (RSD approximately 0.3-5.7%). The estimation of Co was made in the samples of multivitamin tablets (RSD < 2.3%). The results agree with those quoted by manufacturers. 相似文献
90.
Summary Complexes of nickel(II) with N-(2-carboxyphenyl)benzamide (CPBH), 2-amino-N-(2-carboxyphenyl)benzamide (ACPBH), N-isoxazolyl benzamide (IB), N-anilinobenzamide (AB), N-(2-pyridyl)-3-carboxypropanamide (PCPA) and N-(2-pyridyl)-2-carboxybenzamide (PCBA) have been isolated and characterized by elemental analyses, magnetic susceptibility measurements, thermal studies, i.r. and electronic spectral studies. The electrochemical behaviour of some complexes has also been investigated. 相似文献