全文获取类型
收费全文 | 1895篇 |
免费 | 87篇 |
国内免费 | 8篇 |
专业分类
化学 | 1400篇 |
晶体学 | 6篇 |
力学 | 10篇 |
数学 | 219篇 |
物理学 | 355篇 |
出版年
2023年 | 24篇 |
2022年 | 16篇 |
2021年 | 39篇 |
2020年 | 50篇 |
2019年 | 33篇 |
2018年 | 32篇 |
2017年 | 22篇 |
2016年 | 82篇 |
2015年 | 42篇 |
2014年 | 62篇 |
2013年 | 93篇 |
2012年 | 135篇 |
2011年 | 172篇 |
2010年 | 70篇 |
2009年 | 64篇 |
2008年 | 131篇 |
2007年 | 102篇 |
2006年 | 92篇 |
2005年 | 96篇 |
2004年 | 79篇 |
2003年 | 61篇 |
2002年 | 51篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1990年 | 12篇 |
1988年 | 11篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1968年 | 7篇 |
排序方式: 共有1990条查询结果,搜索用时 31 毫秒
71.
Dr. Mohd Nazish Dr. Mujahuddin M. Siddiqui Dr. Samir Kumar Sarkar Dr. Annika Münch Christina M. Legendre Dr. Regine Herbst-Irmer Prof. Dietmar Stalke Prof. Dr. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1744-1752
This work describes the synthesis and coordination behavior of a new mixed-donor ligand PhC(NtBu)2SiC6H4PPh2 ( 1 ) containing both silylene and phosphine donor sites. Ligand 1 was synthesized from a reaction of ortho-lithiated diphenylphosphinobenzene (LiC6H4PPh2) with chlorosilylene (PhC(NtBu)2SiCl). Treatment of 1 with Se and GeCl2 resulted in SiIV compounds 2 and 3 by selective oxidation of the silylene donor. This strong σ-donor ligand induces dissociation of CuCl and PhBCl2 leading to formation of ionic complexes 4 and 5 respectively. The reaction of 1 with ZnCl2 and AlCl3 resulted in the formation of chelate complexes 5 and 7 , respectively, while treatment with EtAlCl2 and GaCl3 forms monodentate complexes 8 and 9 . X-ray analysis of 4 showed that the copper is in the spiro center of the two five-membered rings. Moreover, the copper(I)chloride has not been oxidized but dissociates to Cu+ and [CuCl2]−. All the compounds are well characterized by mass spectrometry, elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies. 相似文献
72.
Prof. Dr. Christian Brückner Dr. Nivedita Chaudhri Dustin E. Nevonen Dr. Sayantan Bhattacharya Arthur Graf Elizabeth Kaesmann Dr. Ruoshi Li Dr. Matthew J. Guberman-Pfeffer Prof. Dr. Tomoyasu Mani Dr. Arunpatcha Nimthong-Roldán Dr. Matthias Zeller Dr. Adrien A. P. Chauvet Prof. Dr. Victor Nemykin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16189-16203
73.
Excitation source of a side-branch shear layer 总被引:1,自引:0,他引:1
Hans R. Graf 《Journal of sound and vibration》2010,329(14):2825-6354
74.
75.
Christina Haberhauer-Troyer Marizela Delic Brigitte Gasser Diethard Mattanovich Stephan Hann Gunda Koellensperger 《Analytical and bioanalytical chemistry》2013,405(6):2031-2039
A novel method for the simultaneous quantification of both glutathione (GSH) and its oxidized form glutathione disulfide (GSSG) by hydrophilic interaction chromatography–MS/MS has been developed and is critically discussed. Internal standardization based on isotopically labeled standards for both analytes is an absolute prerequisite for accurate quantification of this redox pair. Hence, a highly efficient and selective miniaturized procedure for the synthesis of isotopically labeled GSSG from commercially available glutathione-(glycine-13C2,15N) was established using H2O2 as oxidant and NaI as catalyst. Moreover, a tool is presented to monitor and hence uncover artifactual GSSG formation due to oxidation of GSH during sample preparation, which is the main source of systematic error in GSSG analysis. For this purpose, we propose to monitor the oxidation product formed by reaction of naturally occurring GSH with the isotopically labeled GSH used as internal standard. For the determination of GSH/GSSG ratios in yeast, different extraction methods based on (1) hot extraction with aqueous, acidic, or organic solvents, (2) mechanical cell lysis, and (3) extraction at subambient temperature were investigated in terms of recovery, extraction efficiency, and artifactual formation of GSSG. Total combined uncertainties of as low as 25–30 % (coverage factor?=?2) for the determination of GSH/GSSG ratios without derivatization were made possible by the addition of the internal standards early in the analytical procedure (before extraction) and immediate analysis of the analytes. 相似文献
76.
77.
78.
79.
80.
Evangelos I. Tolis Dikaia E. Saraga George Z. Ammari Evangelos I. Gkanas Theofilos Gougoulas Christina C. Papaioannou Anastasios K. Sarioglou Eleftherios Kougioumtzidis Athina Skemperi John G. Bartzis 《Central European Journal of Chemistry》2014,12(6):643-651
Eordaia basin located in northwest of Greece, comprises an area which is characterized by intense energy related activities, including coal burning at four power plants and the associated mining operations. Air samples of inhalable (PM10) and respirable particles (PM2.5) were collected in cold and warm periods in 2010 at an urban background site of Kozani, the major city and capital of the region which is located close to the power plants. Particulate matter concentration, particle-bound polycyclic aromatic hydrocarbons and anionic species concentrations were determined using gravimetric, GC-MS in SIM mode and Ion Chromatography analysis, respectively. For the cold period, the mean PM10 and PM2.5 mass concentration was found to be 19.62 and 14.68 µg m?3, respectively. Correspondingly, for the warm period, the mean PM10 and PM2.5 values were 35.29 and 25.75 µg m?3, respectively. In general, the results indicated that the major sources of air pollution in Kozani are traffic, combustion from agricultural activities and lignite power plants emissions, contributing by different percentages to each particle fraction. 相似文献