全文获取类型
收费全文 | 1272篇 |
免费 | 95篇 |
出版年
2022年 | 6篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 21篇 |
2016年 | 29篇 |
2015年 | 49篇 |
2014年 | 45篇 |
2013年 | 67篇 |
2012年 | 85篇 |
2011年 | 84篇 |
2010年 | 60篇 |
2009年 | 38篇 |
2008年 | 74篇 |
2007年 | 59篇 |
2006年 | 72篇 |
2005年 | 81篇 |
2004年 | 73篇 |
2003年 | 64篇 |
2002年 | 42篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 21篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1970年 | 9篇 |
1966年 | 4篇 |
排序方式: 共有1367条查询结果,搜索用时 723 毫秒
91.
Polyphenols from some foodstuffs as inhibitors of ovalbumin permeation through caco-2 cell monolayers 总被引:3,自引:0,他引:3
Kobayashi S Watanabe J Fukushi E Kawabata J Nakajima M Watanabe M 《Bioscience, biotechnology, and biochemistry》2003,67(6):1250-1257
Some spices showed high inhibitory activity against ovalbumin permeation through Caco-2 cell monolayers. Pimentol from allspice, rosmarinic acid and luteolin-7-O-beta-glucuronide from thyme, quercetin-3-O-beta-glucuronide from coriander and rutin from tarragon were identified as the active principles. A structure-activity relationship study among the active isolates and their related compounds indicated that the presence of a catechol structure played an important role in the inhibitory activity of each compound. 相似文献
92.
Yasuda M Nakashita H Hasegawa S Nishioka M Arai Y Uramoto M Yamaguchi I Yoshida S 《Bioscience, biotechnology, and biochemistry》2003,67(2):322-328
Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is induced through the salicylic acid-mediated pathway. N-cyanomethyl-2-chloroisonicotinamide (NCI) is able to induce a broad range of disease resistance in tobacco and rice and induces SAR marker gene expression without SA accumulation in tobacco. To clarify the detailed mode of action of NCI, we analyzed its ability to induce defense gene expression and resistance in Arabidopsis mutants that are defective in various defense signaling pathways. Wild-type Arabidopsis treated with NCI exhibited increased expression of several pathogenesis-related genes and enhanced resistance to the bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. NCI induced disease resistance and PR gene expression in NahG transgenic plants, but not in the npr1 mutant. NCI could induce PR gene expression in the etr1-1, ein2-1 and jar1-1 mutants. Thus, NCI activates SAR, independently from ethylene and jasmonic acid, by stimulating the site between SA and NPR1. 相似文献
93.
94.
Takehara M Ito E Saito T Nishioka Y Ashihara K Yamashita S Koizumi M Kudo R 《Acta cytologica》2000,44(6):1077-1080
BACKGROUND: Malignant melanoma in the vagina is very rare, but its diagnosis is usually easy if a melanin pigment is present. With cytodiagnosis, however, it is difficult to differentiate amelanotic melanoma or scantily pigmented melanoma from other conditions. In the present case, monoclonal antibody HMB-45, the efficacy of which has been established in histologic studies, was used in the cytodiagnosis of amelanotic melanoma in the vagina. CASE: A woman, aged 78 years, presented with a brownish, nodular tumor, diameter 3 cm, in the vagina. Scraping smears with Papanicolaou staining showed nonepithelial malignant cells without granules suggesting melanin. Smears stained with HMB-45 showed positive immunoreactivity. The diagnosis underwent histologic confirmation of amelanotic melanoma on the initial biopsy. CONCLUSION: Cytodiagnosis was made with HMB-45, which proved very effective in the differential cytodiagnosis of amelanotic melanoma and scantily pigmented melanoma, particularly because it obviated the need for tissue invasion. 相似文献
95.
The nucleotide sequences of the D-loop region and its flanking genes of the mitochondrial DNA (mtDNA) from Japanese pond frogs were determined by the methods of PCR, cloning, and sequencing. The frogs belonged to two species, one subspecies, and one local race. The gene arrangements adjacent to the D-loop region were analyzed. The frogs shared a unique mitochondrial gene order that was found in Rana catesbeiana; i.e., cyt b--D-loop region--tRNA(Leu(CUN))--tRNA(Thr)--tRNA(Pro)--tRNA(Phe)--12S rRNA. The arrangements of the three tRNA genes of these frogs were different from those of X. laevis, a species which has the same overall structure as in mammals. Highly repetitive sequences with repeat units (16-bp or 17-bp sequence specific for each taxon) were found in the D-loop region. The length of repetitive sequences varied from 0.6 kbp to 1.2 kbp, and caused the extensive size variation in mtDNA. Several short sequence elements such as putative TAS, OH, CSB-1, and CSB-2 were found in the D-loop region of these frogs. The sequences of these short regulatory elements were conserved in R. catesbeiana, X. laevis, and also in human. The comparison of sequence divergences of the D-loop region and its adjacent genes among various taxa revealed that the rates of nucleotide substitutions depend on genes. The nucleotide sequences of the 3'-side segment of the D-loop region were the most variable among taxa, whereas those of the tRNA and 12S rRNA genes were the most conservative. 相似文献
96.
Shirakawa R Yoshioka A Horiuchi H Nishioka H Tabuchi A Kita T 《The Journal of biological chemistry》2000,275(43):33844-33849
Upon activation, platelets release many active substances stored in alpha- and dense-core granules. However, the molecular mechanisms governing regulated exocytosis are not yet fully understood. Here, we have established an assay system using permeabilized platelets to analyze the Ca(2+)-induced exocytosis of both types of granules, focusing on RabGTPases. Incubation with Rab GDP dissociation inhibitor, an inhibitory regulator of RabGTPases, reduced membrane-bound RabGTPases extensively, and caused strong inhibition of the Ca(2+)-induced secretion of von Willebrand factor (vWF) stored in alpha-granules, but not that of [(3)H]5-hydroxytryptamine (5-HT) in dense-core granules. Specifically, Rab4 co-fractionated with vWF and P-selectin (an alpha-granule marker) upon separation of platelet organelles by density gradient centrifugation. Incubation of the permeabilized platelets with cell extracts expressing the dominant negative mutant of His-tagged Rab4S22N, but not with those of similar mutant His-Rab3BT36N, inhibited the vWF secretion, whereas neither of the cell extracts affected the [(3)H]5-HT secretion. Importantly, the inhibition of vWF secretion was rescued by depleting the cell extracts of the His-Rab4S22N with nickel beads. Thus, in platelets, the regulatory mechanisms governing alpha- and dense-core granule secretions are distinct, and Rab4 is an essential regulator of the Ca(2+)-induced exocytosis of alpha-granules. 相似文献
97.
Involvement of jasmonate- and salicylate-related signaling pathways for the production of specific herbivore-induced volatiles in plants 总被引:25,自引:0,他引:25
We compared volatiles from lima bean leaves (Phaseolus lunatus) infested by either beet armyworm (Spodoptera exigua), common armyworm [Mythimna (Pseudaletia) separata], or two-spotted spider mite (Tetranychus urticae). We also analyzed volatiles from the leaves treated with jasmonic acid (JA) and/or methyl salicylate (MeSA). The volatiles induced by aqueous JA treatment were qualitatively and quantitatively similar to those induced by S. exigua or M. separata damage. Furthermore, both S. exigua and aqueous JA treatment induced the expression of the same basic PR genes. In contrast, gaseous MeSA treatment, and aqueous JA treatment followed by gaseous MeSA treatment, induced volatiles that was qualitatively and quantitatively more similar to the T. urticae-induced volatiles than those induced by aqueous JA treatment. In addition, T. urticae damage resulted in the expression of the acidic and basic PR genes that were induced by gaseous MeSA treatment and by aqueous JA treatment, respectively. Based on these data, we suggest that in lima bean leaves, the JA-related signaling pathway is involved in the production of caterpillar-induced volatiles, while both the SA-related signaling pathway and the JA-related signaling pathway are involved in the production of T. urticae-induced volatiles. 相似文献
98.
Koichiro Harada Hideki Kubo Yoshitaka Tomigahara Kazuhiko Nishioka Junya Takahashi Mio Momose Shinichi Inoue Atsuyuki Kojima 《Bioorganic & medicinal chemistry letters》2010,20(1):272-275
The synthesis and SAR studies of 3- and 4-substituted 7-hydroxycoumarins as novel 17β-HSD3 inhibitors are discussed. The most potent compounds from this series exhibited low nanomolar inhibitory activity with acceptable selectivity versus other 17β-HSD isoenzymes and nuclear receptors. 相似文献
99.
100.