全文获取类型
收费全文 | 2769篇 |
免费 | 175篇 |
国内免费 | 4篇 |
出版年
2022年 | 13篇 |
2021年 | 29篇 |
2020年 | 13篇 |
2019年 | 23篇 |
2018年 | 32篇 |
2017年 | 17篇 |
2016年 | 54篇 |
2015年 | 62篇 |
2014年 | 94篇 |
2013年 | 282篇 |
2012年 | 121篇 |
2011年 | 137篇 |
2010年 | 100篇 |
2009年 | 70篇 |
2008年 | 114篇 |
2007年 | 145篇 |
2006年 | 151篇 |
2005年 | 128篇 |
2004年 | 136篇 |
2003年 | 134篇 |
2002年 | 121篇 |
2001年 | 115篇 |
2000年 | 88篇 |
1999年 | 70篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 30篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 32篇 |
1992年 | 50篇 |
1991年 | 45篇 |
1990年 | 41篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 36篇 |
1986年 | 28篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1974年 | 10篇 |
1973年 | 8篇 |
排序方式: 共有2948条查询结果,搜索用时 218 毫秒
121.
Tomoya Ogawa Motoshi Yasui Masanao Matsui 《Bioscience, biotechnology, and biochemistry》2013,77(8):1445-1447
The Colletotrichum lagenarium PKS1 gene was expressed in the heterologous fungal host, Aspergillus oryzae, under the starch-inducible α-amylase promoter to identify the direct product of polyketide synthase (PKS) encoded by the PKS1 gene. The main compound produced by an A. oryzae transformant was isolated and characterized to be 1,3,6,8-tetrahydroxynaphthalene (T4HN) as its tetraacetate. Since the PKS1 gene was cloned from C. lagenarium to complement the nonmelanizing albino mutant, T4HN was assumed to be an initial biosynthetic intermediate, and thus the product of the PKS reaction, but had not been isolated from the fungus. The production of T4HN by the PKS1 transformant unambiguously identified the gene to encode a PKS of pentaketide T4HN. In addition, tetraketide orsellinic acid and pentaketide isocoumarin were isolated, the latter being derived from a pentaketide monocyclic carboxylic acid, as by-products of the PKS1 PKS reaction. Production of the pentaketide carboxylic acid provided insights into the mechanism for the PKS1 polyketide synthase reaction to form T4HN. 相似文献
122.
123.
Kenji Mori Masanao Matsui Yusuke Sumiki 《Bioscience, biotechnology, and biochemistry》2013,77(3):205-222
In order to clarify the structure of ring A of gibberellins, thirteen lactones of cyclohexan series, of which eight were new, were prepared to examine their infrared spectra. So far; the experiment is concerned, γ-lactones show the characteristic absorption band in the rang 1775~1782 cm?1 in dioxane, while 5-ones in the range 1730/~1762 cm?1. Since the absorptio band due to lactone carbonyl of gibberellins occurs at the range 1777~1786 cm?1 in dioxane, the lactone ring of gibberellins seems to be γ. 相似文献
124.
Ikuo Matsui Toshiyuki Kameyama Kunio Oishi Ko Aida 《Bioscience, biotechnology, and biochemistry》2013,77(3):833-835
The inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamide derivatives on human 5-lipoxygenase (5-LO), a key enzyme in arachidonic acid cascades, were examined using 5-LO produced by Escherichia coli. Some of the tested compounds inhibited the conversion of arachidonic acid to 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE), and in particular the N-phenylbutyl derivative was about 30 times more active (IC50 = 35 μm) than caffeic acid (IC50 = 1000 μm), a known selective 5-LO inhibitor. 相似文献
125.
The 2,3-Dihydro-lH-pyrrolo[l,2-a]indole ring system was synthesised by the condensation reaction of toluquinone and 2-cyanomethylenepyrrolidine. 相似文献
126.
Susumu Murata Hirokazu Matsui Seiya Chiba Tokuji Shimomura 《Bioscience, biotechnology, and biochemistry》2013,77(10):2131-2135
The substrate specificity of rice α-glucosidase II was studied. The enzyme was active especially on nigerose, phenyl-α-maltoside and maltooligosaccharides. The actions on isomaltose and phenyl-α-glucoside were weak, and on sucrose and methyl-α-glucoside, negligible. The α-glucans, such as soluble starch, amylopectin, β-limit dextrin, glycogen and amylose, were also hydrolyzed.The ratio of the maximum velocities for hydrolyses of maltose (G2), nigerose (N), kojibiose (K), isomaltose (I), phenyl-α-maltoside (?M) and soluble starch (SS) was estimated to be 100: 94.4: 14.2: 7.1: 89.5: 103.1 in this order, and that for hydrolyses of malto-triose (G3), -tetraose (G4), -pentaose (G5), -hexaose (G6), -heptaose (G7), -octaose (G8), and amyloses ( and ), 113: 113: 113: 106: 113: 100: 106: 106. The Km values for N, K, I, ?M and SS were 2.4 mm, 0.58 mm, 20 mm, 1.6 mm and 5.0 mg/ml, respectively; those for G2, G3, G4, G5, G6, G7, G8, and , 2.4 mm, 2.2 mm, 2.1 mm, 1.5 mm, 1.0 mm, 1.1 mm, 0.95 mm, 1.5 mm and 1.1 mm.Rice α-glucosidase II is considered an enzyme with a preferential activity on maltooligosaccharides. 相似文献
127.
Masateru Miyano Akio Kobayashi Masanao Matsui 《Bioscience, biotechnology, and biochemistry》2013,77(9):673-677
d,l-Derrisic acid (IIa, R′: H) was synthesized from d,l-hydroxy dihydrotubanol (Ve) by Hoesch condensation with a nitrile (VI). The possible optical resolution of d,l-IIa was demonstrated by a conventional “reversed resolution” method.This communication and previous works constitute the first total synthesis of natural rotenone (Ia). 相似文献
128.
The structure of a minor component in the oxidation products of crude natural variotin oxidized with manganese dioxide is elucidated. The synthesis of the investigated compound, N-(6-oxo-2,4-trans, tralls-heptadienoyl) 2-pyrrolidonide, and the reduction of the substance are also described. 相似文献
129.
Hiroyasu Koyama Katsura Kogure Kenji Mori Masanao Matsui 《Bioscience, biotechnology, and biochemistry》2013,77(4):915-920
Antimycinone A3, which is a neutral fragment of mild alkaline hydrolysate of antimycin A3, and its stereoisomers were synthesized stereoselectively from methyl trans-2-n-butylpent-3-enoate or methyl cis-2-n-butylpent-3-enoate, and natural antimycinone A3 was proved to possess Hα-Hβ and Hβ-Hγ trans configuration. 相似文献
130.
So called ambreinolal (IV),* a component of ambergris, was first synthesized by CrO3 oxidation of ambreinolol (III)* which was obtained from ambreinolide (II) by reduction with LiAlH4. Ambreinolol (III) was converted to the C17-saturated oxide (VII) in a good yield through the monotosylate (VIII) by treatment with p-toluenesulfonyl chloride in pyridine.Ambrein (I), a major constituent of ambergris, was easily converted to ambrein-tetrahydropyranylether (II), of which thermal decomposition gave back ambrein (I). The tetrahydropyranylether (II) was oxidized to ambreinolal-tetrahydropyranylether (V) in two steps. Ambreinolal-tetrahydropyranylether (V) was synthesized from ambreinolol (VII) in four steps and converted to the C17-unsaturated oxide (VI) on heating. 相似文献