全文获取类型
收费全文 | 16063篇 |
免费 | 1484篇 |
国内免费 | 1967篇 |
出版年
2024年 | 51篇 |
2023年 | 247篇 |
2022年 | 584篇 |
2021年 | 942篇 |
2020年 | 730篇 |
2019年 | 845篇 |
2018年 | 760篇 |
2017年 | 511篇 |
2016年 | 727篇 |
2015年 | 1083篇 |
2014年 | 1258篇 |
2013年 | 1252篇 |
2012年 | 1536篇 |
2011年 | 1413篇 |
2010年 | 829篇 |
2009年 | 759篇 |
2008年 | 917篇 |
2007年 | 816篇 |
2006年 | 707篇 |
2005年 | 584篇 |
2004年 | 474篇 |
2003年 | 419篇 |
2002年 | 341篇 |
2001年 | 227篇 |
2000年 | 180篇 |
1999年 | 214篇 |
1998年 | 156篇 |
1997年 | 140篇 |
1996年 | 99篇 |
1995年 | 78篇 |
1994年 | 73篇 |
1993年 | 75篇 |
1992年 | 76篇 |
1991年 | 63篇 |
1990年 | 54篇 |
1989年 | 54篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1974年 | 5篇 |
1970年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Ulrik Pedersen-Bjergaard Lars B geskov Nielsen Kai Jensen Lars Edvinsson Inger Jansen Jes Olesen 《Peptides》1989,10(6):1147-1152
Neurokinin A (NKA), substance P (SP) and the two peptides combined (SP + NKA) were injected intracutaneously on the forearm and into the temporal muscle of healthy volunteers. Pain intensity, cutaneous wheal and flare responses and tenderness of the temporal muscle were quantitated. SP but not NKA induced cutaneous pain. This relates the algesic effect of SP to the specific N-terminal amino acid sequence of the peptide, not shared by NKA. NKA, however, potentiated the algesic effect of SP as SP + NKA induced a significantly prolonged cutaneous pain sensation. Both peptides induced wheals, but only SP induced flare. These results confirm previous studies relating wheal formation to the identical C-terminal amino acid sequence of the two peptides and flare reaction to the N-terminal part of SP. Injections into the temporal muscle did not cause pain or tenderness. 相似文献
22.
23.
.钱敏之;.傅萼辉;.徐惠珠;.叶银根 《武汉植物学研究》1988,6(3):267-274
本文针对湖北贝母生产中存在繁殖系数低的问题,研究了单鳞片砂培繁殖对提高鳞茎繁殖率的效果和原理。试验结果表明:1.单鳞片繁殖率为对照种鳞茎的5—9倍,2.低温(2—10℃)预处理4—8周和暗条件培养,能有效地提高子球形成率,促使子球迅速长大,3.植物激素(6-BA、KT、2,4-D)处理,有利于促进鳞片不定芽原基的分化,繁殖率为种茎繁殖的9—11倍;4.单鳞片繁殖的小鳞茎主要发生在鳞片基部的茎盘上,还可发生在鳞片的远轴面上,但不发生在近轴面。 相似文献
24.
Immunization of mice with a synthetic GM3-lactam-BSA (bovine serum albumin) conjugate (designed to emulate the corresponding natural GM3-lactone conjugate), followed by fusion of splenocytes with myeloma cells, gave rise to more than 300 monoclonal hybridomas producing antibodies to GM3-lactam-BSA, which did not react with Glc-BSA and BSA. Eight antibody clones were randomly chosen from the positive 300 hybridomas. The eight clones, all belonging to the IgG class, were unreactive against GM3-ganglioside, whereas two antibodies (P5-1 and P5-3, both IgG1, ) reacted with GM3-ganglioside lactone. Binding of these two antibodies to the GM3-lactam-BSA conjugate was inhibited by soluble glycosides of GM2-, GM3-, and GM4-lactam and by GM3- and GM4-lactam, respectively, but not by Gb3 or asialo-GM1 and GM2-saccharides. A third antibody (P3; IgG2b, ) was inhibited by GM2-, GM3-, and GM4-lactam, but did not recognize GM3-ganglioside lactone. 相似文献
25.
From dilution series in defined mineral medium, a marine iregular coccoid methanogenic bacterium (strain MTP4) was isolated
that was able to grow on methanethiol as sole source of energy. The strain also grew on dimethylsulfide, mono-, di-, and trimethylamine,
methanol and acetate. On formate the organism produced methane without significant growth. Optimal growth on MT, with doubling
times of about 20 h, occurred at 30°C in marine medium. The isolate required p-aminobenzoate and a further not identified
vitamin. Strain MTP4 had a high tolerance to hydrogen sulfide but was very sensitive to mechanical forces or addition of detergents
such as Triton X-100 or sodium dodecylsulfate. Methanethiol was fermented by strain MTP4 according to the following equation:
相似文献
26.
Formation of dimethylsulfide and methanethiol from methoxylated aromatic compounds and inorganic sulfide by newly isolated anaerobic bacteria 总被引:1,自引:0,他引:1
Formation of gas and of methylated sulfur compounds was observed in anaerobic enrichment cultures with methoxylated aromatic compounds as substrates. Via direct dilution of mud samples in defined reduced media supplemented with trimethoxybenzoate or syringate two new strains of anaerobic homoacetogenic bacteria (strain TMBS4 and strain SA2) were obtained in pure culture. Both strains produced dimethylsulfide and methanethiol during growth on methoxylated aromatic compounds. Growth tests and determination of stoichiometries demonstrated that the volatile sulfur compounds were formed from the methyl group at the aromatic ring and the sulfide added as reducing agent to the medium (R = aromatic residue): 2 R - O - CH3 + H2 S 2 R - OH + (CH3)2SDimethylsulfide was the major organic sulfur compound formed, whereas methanethiol appeared only as intermediate in small quantities. The isolates grew also with trihydroxybenzenes such as gallate, phloroglucinol, or pyrogallol without formation of methylated sulfur compounds. The aromatic compounds were degraded to acetate. The freshwater strain TMBS4 also fermented pyruvate. Other aliphatic or aromatic compounds were not utilized. External electron acceptors (sulfate, nitrate, fumarate) were not reduced. Both strains were mesophilic and formed rod-shaped, non-motile, Gram-negative cells. Spore formation was not observed. Tentatively, both isolates can be affiliated to the genus Pelobacter.Abbreviations TMB
3,4,5-trimethoxybenzoate
- MT
methanethiol
- DMS
dimethylsulfide 相似文献
27.
Dr. Jian Wen Chen Lanping Zhang Jiantao Song Fen Hwang Qinghua Dong Jian Liu Yumin Qian 《Current microbiology》1992,24(4):189-192
The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z. 相似文献
28.
29.
|