全文获取类型
收费全文 | 128617篇 |
免费 | 33007篇 |
国内免费 | 9370篇 |
专业分类
化学 | 114506篇 |
晶体学 | 985篇 |
力学 | 7687篇 |
综合类 | 465篇 |
数学 | 12500篇 |
物理学 | 34851篇 |
出版年
2024年 | 677篇 |
2023年 | 5659篇 |
2022年 | 4637篇 |
2021年 | 5829篇 |
2020年 | 8093篇 |
2019年 | 5771篇 |
2018年 | 5220篇 |
2017年 | 3409篇 |
2016年 | 9663篇 |
2015年 | 9678篇 |
2014年 | 9995篇 |
2013年 | 11595篇 |
2012年 | 11061篇 |
2011年 | 8932篇 |
2010年 | 8838篇 |
2009年 | 8546篇 |
2008年 | 6612篇 |
2007年 | 5615篇 |
2006年 | 4511篇 |
2005年 | 3689篇 |
2004年 | 2857篇 |
2003年 | 2238篇 |
2002年 | 2022篇 |
2001年 | 1709篇 |
2000年 | 1543篇 |
1999年 | 1725篇 |
1998年 | 1431篇 |
1997年 | 1454篇 |
1996年 | 1482篇 |
1995年 | 1286篇 |
1994年 | 1101篇 |
1993年 | 1070篇 |
1992年 | 836篇 |
1991年 | 717篇 |
1990年 | 592篇 |
1989年 | 497篇 |
1988年 | 488篇 |
1987年 | 401篇 |
1986年 | 359篇 |
1985年 | 328篇 |
1977年 | 375篇 |
1976年 | 425篇 |
1975年 | 503篇 |
1974年 | 517篇 |
1973年 | 350篇 |
1972年 | 466篇 |
1971年 | 420篇 |
1970年 | 629篇 |
1969年 | 461篇 |
1968年 | 506篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Guo Yang Zhu Rong Wang Guo Hua Liu Li Qun Xu Bei Zhang Xia Qin Wu College of Life Environment Science Shanghai Normal University Shanghai China State Key Laboratory of Chema/Biosensing Chemometrics Hunan University Changsha China 《中国化学快报》2007,18(6):633-635
Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte). 相似文献
994.
1 INTRODUCTION The infinite networks constructed from transition metal complexes have attracted considerable current interest in recent years. The motivation behind this activity has been stimulated by their potential appli- cations in selective inclusion of ions, molecular re- cognition, host-guest chemistry, ion exchange, cata- lysis, electrical conductivity, magnetism, optics and so on[1~4]. It is well known that the diversity in structures and topologies of supramolecules is attri- b… 相似文献
995.
Bao Liu Ling Huang Juntao Liu Yao Zhong Xingshu Li Albert S.C. Chan 《Tetrahedron: Asymmetry》2007,18(24):2901-2904
Chiral tridentate N-tosylated aminoimine ligands were used in the Cu(II)-catalyzed enantioselective addition of phenylacetylene to N-aryl arylimines, affording products up to 92% ee. 相似文献
996.
W 7-agarose是常用的细胞外CaM功能的拮抗剂,本实验采用荧光光谱法研究了水溶液中钙调素拮抗剂W 7-agarose与植物胞外钙调素的相互结合反应。W 7-agarose是一种将W 7-共价连接到颗粒型agarose(琼脂糖)的粒子。W 7-agarose颗粒较大且容易沉淀,静置5m in后,溶液中的荧光强度完全由游离的CaM产生。在溶液中加入W 7-agarose后,溶液中一部分CaM与其结合后沉降至荧光比色皿底部,导致溶液中CaM的荧光强度下降。由此可以确定溶液中游离CaM的浓度。根据公式lg{[Q]t(F0-F)/F0}=nlg{[Q]tF/F0} lgnK[B]t,从而计算出配位体系的结合常数和配比。研究表明:二者以摩尔比1∶1结合,其平衡常数为4.9×105。由此进一步计算了W 7-agarose对胞外钙调素的拮抗率,在拮抗剂W 7-agarose浓度达到15~20μmol/L时,拮抗率可达到90%以上,与文献报道的生物学体内实验结果一致,从分子水平上解释了W 7-agarose与CaM的结合作用。 相似文献
997.
X. Liu F. Xu Y. Zhang L. Liu H. Huang X. Cai Y. Lin W. Chan 《Russian Chemical Bulletin》2006,55(6):1091-1092
(3R*,3aR*,9aR*)-3,9a-Dimethyl-2,3,3a,9a-tetrahydro-4H-furo[2,3-b]chromene-5,7-diol (xyloketal H), a representative of a new family of xyloketals, was isolated from the marine-derived mangrove
fungus Xylaria sp. 2508. Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction analysis.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1051–1052, June, 2006. 相似文献
998.
Lei JD Tong AJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(6):1029-1033
An integrated microchip was presented for selective recognition of Z-L-Phe-OH-NBD, using molecular imprinting technique. Molecularly imprinted polymer (MIP) were prepared by copolymerization in the presence of template molecule Z-L-Phe-OH-NBD, in which methacrylic acid and 4-vinylpyridine were used as functional monomers and ethylene dimethacrylate used as crosslinker. Imprinted polymer particles were introduced into a microchannel fabricated with a new material i.e. poly(methylvinylsiloxane) by simply rapid prototyping method. Imprinted effects were evaluated by laser-induced fluorescence (LIF) detection where the results indicated that good selective recognition for Z-L-Phe-OH-NBD in the imprinted polymer was obtained; the adsorption percentage of Z-L-Phe-OH-NBD was 61%. In contrast to conventional molecular imprinting analysis, integration shortened overall analysis time from 4h to 10 min. 相似文献
999.
Zhang YL Qin WW Liu WS Tan MY Tang N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(10):2153-2157
An amide-based open-chain crown ether ligand and its complexes with europium and terbium were synthesized. The complexes were characterized by elemental analysis, infrared spectra and conductivity. The europium and terbium ions were found to coordinate to the C=O oxygen atoms and pyridine nitrogen atoms. The fluorescence properties of these complexes in DMF and CH3OH/CHCl3 were studied. Under the excitation of UV light, these complexes exhibit characteristic fluorescence of europium and terbium ions. The solvent factors influencing the fluorescent intensity are discussed. 相似文献
1000.