全文获取类型
收费全文 | 1185篇 |
免费 | 73篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 18篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 38篇 |
2014年 | 46篇 |
2013年 | 93篇 |
2012年 | 67篇 |
2011年 | 72篇 |
2010年 | 55篇 |
2009年 | 39篇 |
2008年 | 66篇 |
2007年 | 64篇 |
2006年 | 51篇 |
2005年 | 63篇 |
2004年 | 55篇 |
2003年 | 66篇 |
2002年 | 86篇 |
2001年 | 21篇 |
2000年 | 23篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 23篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 19篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1980年 | 5篇 |
1975年 | 3篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1964年 | 2篇 |
排序方式: 共有1258条查询结果,搜索用时 15 毫秒
21.
Yoshihiro Takasugi Keiji Kawata Takahiko Okuda Yoshihisa Koga Nobuyuki Mizuguchi Shigeaki Yamanaka Shinsuke Watanabe 《Experimental Animals》2003,52(5):429-432
Age-related alterations and differences of weights and those of amino acid concentrations in the cerebrospinal fluid (CSF) were evaluated between Sprague Dawley (SD) rats and Wistar Kyoto (WKY) rats from eight to twenty weeks of age. The weights of SD rats were heavier than WKY rats at all ages. The age-related alterations of the CSF concentration of many amino acids within each strain were significant but showed no significant trend with age. Between the strains, the concentration differences of excitatory and inhibitory amino acids were not frequent although the concentrations of arginine, alanine and threonine were significantly higher in SD rats than in WKY rats. These results suggest that the different CSF concentrations of amino acids may relate to characteristics of rat strains. 相似文献
22.
Extraction of the aerial parts of Dumasia truncata Sieb et Zucc. afforded two new triterpenoidal saponins, together with four known ones. The structures of the new compounds were elucidated by spectral analysis as 3-O--l-rhamnopyranosyl-(1 → 3)-β-d-glucuronopyranosy-28-O-β-d-glucopyransoyl hederagenin and 3-O-β-d-xylopyranosyl-(1 → 2)-[-l-rhamnopyranosyl(1 → 3)]-β-d-glucuronopyranosyl oleanic acid. 相似文献
23.
Virulent and avirulent Rhodococcus equi infection in T-cell deficient athymic nude mice: pathologic, bacteriologic and immunologic responses 总被引:1,自引:0,他引:1
24.
Yoshihisa Iwamoto Yusaku Suzuki Akinobu Kurita Yoko Watanabe Tadayori Shimizu Hirohisa Ohgami Yasutake Yanagihara 《Microbiology and immunology》1995,39(11):831-837
A new species, Vibrio trachuri sp. nov., was isolated from the cultured Japanese horse mackerel (Trachurus japonicus). These Vibrio were Gram negative, motile rods and formed yellow colonies on BTB teepol and TCBS plate, turned TSI medium to yellow and was sensitive to 150 μM O/129 (2,4-diamino-6,7-diisopropyl pteridine phosphate) like Listonella anguillarum which has been described as Vibrio anguillarum. However, the results of VP test and decarboxylation of lysine or dihydrolation of arginine suggested that these Vibrio are rather closely related to V. parahaemolyticus. DNA similarity determined by the microplate hybridization technique revealed that these Vibrio are genetically quite distant from Listonella anguillarum or V. parahaemolyticus and rather close to V. harveyi, although there was no Vibrio species which had more than 70% similarity value. From these results we propose to nominate Vibrio trachuri sp. nov. for this new Vibrio species. 相似文献
25.
The effects of ACTH, its o-nitrophenyl sulfenyl derivative (NPS-ACTH) and dibutyryl cyclic AMP (dbc AMP) on the ultrastructural morphology of adrenocortical cells of adult rats in monolayer culture have been investigated. NPS-ACTH, which has previously been shown to stimulate steroidogenesis but not cAMP synthesis in adrenal cells, induced the same characteristic transformation of mitochondrial architecture as produced by ACTH or high concentrations of dbcAMP. All three agents caused the disappearance of electron-opaque granules present in the mitochondria of unstimulated cells. It was found that these granules could be extracted with EGTA (ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetate). These results are discussed in the light of the known importance of calcium ions in the actions of ACTH. 相似文献
26.
Two allyl hydroperoxy guaianolide sesquiterpene lactones (peroxyeupahakonin-A and -B) and five new guaianolides (eupahakonin-A and -B, eupahakonenin-A and -B, and eupahakonesin) were isolated from E. chinense and characterized. The allyl hydroperoxy sesquiterpene lactones were characterized by spectral and chemical methods. They were prepared chemically by photosensitized oxygenation of eupahakonin-A. 相似文献
27.
28.
The relation between codon usage and gene-expression levels is an intensively investigated and discussed topic in the field of molecular evolution. We statistically analyzed 25 Escherichia coli gene sequences by a new classification of synonymous codons and found that (i) there are two distinct types of linkage between codon usage and gene-expression levels in E. coli, and (ii) one of the two kinds of codon preferences (the codon preference concerned with interaction of GC/AT choice at three codon positions) is observed significantly in weakly expressed genes. 相似文献
29.
Hamako Sasamoto Akira Kondo Yoshihisa Hosoi Hisae Maki Keiji Odani 《In vitro cellular & developmental biology. Plant》1992,28(3):132-136
Summary Protoplasts were isolated from cotyledons of 1- to 1.5-mo.-old seedlings ofChamaecyparis obtusa using 1% driselase or 0.25% pectolyase Y-23 in combination with 1% cellulase RS in 0.6M mannitol solution. Cell division and colony formation were induced efficiently in liquid Murashige and Skoog’s (MS) medium
containing 0.6M mannitol and 10 to 30 μM 2,4-dichlorophenoxyacetic acid or 1 μM of naphthaleneacegic acid at the cell density of 1 to 2×103 ml. Continued callus proliferations was observed by transferring tissue to fresh medium of the same composition as the induction
medium without mannitol. Campbell and Durzan’s medium and ammonium nitrate-free MS medium were less effective than MS medium.
High concentration of benzyladenine (1 or 10 μM) was inhibitory to cell division. 相似文献
30.
A new pentafunctional cross-linking amino acid, termed allodesmosine, was isolated from bovine ligamentum nuchae elastin. This compound was a very hygroscopic, white amorphous solid with a faint yellow tinge, soluble in aqueous solvents but not dry methanol; it was characterized by UV, FAB mass and NMR spectroscopy. The compound was shown by UV and 1H-NMR to have a pyridinium ring structure similar to desmosine. Mass spectral analysis indicated a parent compound with a mass of 655. We postulated that it arose by condensation of a reduced aldol condensation product of allysine, allysine and lysine. 相似文献