全文获取类型
收费全文 | 2446篇 |
免费 | 177篇 |
国内免费 | 11篇 |
专业分类
化学 | 1950篇 |
晶体学 | 33篇 |
力学 | 25篇 |
数学 | 119篇 |
物理学 | 507篇 |
出版年
2023年 | 22篇 |
2022年 | 25篇 |
2021年 | 47篇 |
2020年 | 66篇 |
2019年 | 72篇 |
2018年 | 46篇 |
2017年 | 30篇 |
2016年 | 112篇 |
2015年 | 97篇 |
2014年 | 90篇 |
2013年 | 133篇 |
2012年 | 220篇 |
2011年 | 240篇 |
2010年 | 104篇 |
2009年 | 79篇 |
2008年 | 152篇 |
2007年 | 147篇 |
2006年 | 136篇 |
2005年 | 145篇 |
2004年 | 112篇 |
2003年 | 81篇 |
2002年 | 68篇 |
2001年 | 38篇 |
2000年 | 28篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 20篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1967年 | 8篇 |
排序方式: 共有2634条查询结果,搜索用时 15 毫秒
991.
Noriyuki Hara Prof. Shuichi Nakamura Masahide Sano Ryota Tamura Prof. Yasuhiro Funahashi Prof. Norio Shibata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9276-9280
The organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to ketimines derived from isatins by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. The products could be converted into optically active AG‐041R. X‐ray crystallographic analysis revealed that the hydrogen bonding between the sulfonimide proton and the 8‐quinolyl nitrogen atom plays an important role in exerting the enantioselectivity of the reaction. 相似文献
992.
Fujiwara K Sato T Sano Y Norikura T Katoono R Suzuki T Matsue H 《The Journal of organic chemistry》2012,77(11):5161-5166
The first total synthesis of natural, unsymmetrical 2',3'-diacyloxy-p-terphenyls, thelephantin O (1) and terrestrins C and D (2 and 3, respectively), was achieved via a practical route which was also applicable to the synthesis of the symmetrical diesters vialinin A/terrestrin A (4) and terrestrin B (5). Compounds 1-5 exhibited cytotoxicity against cancer cells (HepG2 and Caco2) with IC(50) values of 13.6-26.7 μmol/L. 相似文献
993.
Isozaki K Ogata K Haga Y Sasano D Ogawa T Kurata H Nakamura M Naota T Takaya H 《Chemical communications (Cambridge, England)》2012,48(33):3936-3938
A new type of Pt-complex-bound amino acid was synthesized by condensation of a cyclometalated Pt complex with the side-chain residue of N- and C-alkylated glutamic acid. Self-assembly of the Pt-bound lipophilic amino acid afforded a supramolecular gel in organic solvents, which comprised fibrous lamellar aggregates that supported a highly oriented Pt array. 相似文献
994.
Chaikittisilp W Hu M Wang H Huang HS Fujita T Wu KC Chen LC Yamauchi Y Ariga K 《Chemical communications (Cambridge, England)》2012,48(58):7259-7261
Nanoporous carbons with high surface area are achieved through direct carbonization of a commercially available zeolitic imidazolate framework (ZIF-8) without any additional carbon sources. The resultant nanoporous carbons exhibit high electrochemical capacitances in an acidic aqueous electrolyte. 相似文献
995.
996.
997.
998.
Y Kasai N Michihata H Nishimura T Hirokane H Yamada 《Angewandte Chemie (International ed. in English)》2012,51(32):8026-8029
Quite strained: The total synthesis of (+)-davidiin, an ellagitannin with more substituents in axial than in equatorial positions, requires a conformational lock of the glucose, induced by steric repulsion between adjacent bulky silyloxy groups. This conformational lock played a pivotal role in 1)?the β-selective formation of the glycosyl ester at the anomeric position, 2)?the formation of the 1,6-HHDP bridge, and 3)?the complete control of axial chirality in the aryl-aryl coupling. 相似文献
999.
Yamada Y Miyahigashi T Ohkubo K Fukuzumi S 《Physical chemistry chemical physics : PCCP》2012,14(30):10564-10571
Photocatalytic hydrogen evolution has been made possible by using oxalate as a carbon-neutral electron source, metal nanoparticles as hydrogen-evolution catalysts and the 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh(+)-NA), which forms the long-lived electron-transfer state upon photoexcitation, as a photocatalyst. The hydrogen evolution was conducted in a deaerated mixed solution of an aqueous buffer and acetonitrile (MeCN) [1:1 (v/v)] by photoirradiation (λ > 340 nm). The gas evolved during the photocatalytic reaction contained H(2) and CO(2) in a molar ratio of 1:2, indicating that oxalate acts as a two-electron donor. The hydrogen yield based on the amount of oxalate reached more than 80% under pH conditions higher than 6. Ni and Ru nanoparticles as well as Pt nanoparticles act as efficient hydrogen-evolution catalysts in the photocatalytic hydrogen evolution. The photocatalyst for hydrogen evolution can be used several times without significant deactivation of the catalytic activity. Nanosecond laser flash photolysis measurements have revealed that electron transfer from oxalate to the photogenerated QuPh˙-NA˙(+), which forms a π-dimer radical cation with QuPh(+)-NA [(QuPh˙-NA˙(+))(QuPh(+)-NA)], occurs followed by subsequent electron transfer from QuPh˙-NA to the hydrogen-evolution catalyst in the photocatalytic hydrogen evolution. Oxalate acts as an efficient electron source under a wide range of reaction conditions. 相似文献
1000.
Sato Y Zhang Y Seino T Sugimoto T Nishizawa S Teramae N 《Organic & biomolecular chemistry》2012,10(20):4003-4006
We report on highly selective binding of a naphthyridine derivative with a trifluoromethyl group to cytosine opposite an abasic site in DNA duplexes; the binding-induced fluorescence quenching is applicable to the analysis of a C-related single-base mutation in DNAs amplified by PCR. 相似文献