全文获取类型
收费全文 | 328篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
355篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 26篇 |
2014年 | 22篇 |
2013年 | 29篇 |
2012年 | 28篇 |
2011年 | 30篇 |
2010年 | 17篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有355条查询结果,搜索用时 15 毫秒
311.
312.
313.
Dr. Choy Ker Woon Prof. Dr. Fasihuddin Badruddin Ahmad Dr. Nor Hisam Zamakshshari 《化学与生物多样性》2023,20(9):e202300166
Cancer has become the primary cause of death worldwide, and anticancer drugs are used to combat this disease. Synthesis of anticancer drugs has limited success due to adverse side effects has made compounds from natural products with minimal toxicity gain much popularity. Piper species are known to have a biological effect on human health. The biological activity is due to Piper species rich with active secondary metabolites that can combat most diseases, including cancer. This review will discuss the phytochemistry of Piper species and their anticancer activity. The identification and characterization of ten active metabolites isolated from Piper species were discussed in detail and their anticancer mechanism. These metabolites were mainly found could inhibit anticancer through caspase and P38/JNK pathways. The findings discussed in this review support the therapeutic potential of Piper species against cancer due to their rich source of active metabolites with demonstrated anticancer activity. 相似文献
314.
Aiman Faizudin Aziz Nor Azma Yusuf Boon Chin Tan Norzulaani Khalid 《Plant Cell, Tissue and Organ Culture》2017,128(1):25-41
We evaluated the ploidy levels and tissue culture responses of 16 Japanese Miscanthus accessions, which are registered and vegetatively maintained in the National Agriculture and Food Research Organization GeneBank, Japan, to screen suitable genotypes for the molecular breeding of Miscanthus species. A ploidy analysis showed that most M. sinensis and M. sinensis var. condensatus (var. condensatus) were putative diploids, but one accession identified as M. sinensis was unexpectedly a putative tetraploid. Additionally, M. sacchariflorus and its hybrid accessions were putative tetraploids. The deoxyribonucleic acid levels in var. condensatus were significantly higher than those in the diploid M. sinensis. Of the accessions, 10, including M. sinensis and var. condensatus, could induce plant regenerable embryogenic calli from apical meristems. We selected three of these M. sinensis accessions for further experiments because their calli growth rates were faster than those of the var. condensatus accessions. Tissue culture experiments with the selected accessions indicated that the frequencies of callus and green shoot formation strongly correlated with genotype. The broad-sense heritabilities of the embryogenic callus and green shoot formation frequencies in the selected accessions were 0.75 and 0.65, respectively, indicating that the cultures’ responses were mainly controlled by genetic factors. Thus, we further selected one accession that had the highest efficiencies in callus and green shoot formation, and we observed that light during callus culturing significantly inhibited calli growth, but promoted plant regeneration from calli in the selected accession. 相似文献
315.
316.
A Point Mutation in the Ethylene-Inducing Xylanase Elicitor Inhibits the β-1-4-Endoxylanase Activity But Not the Elicitation Activity 下载免费PDF全文
Noa Furman-Matarasso Eitan Cohen Quansheng Du Nor Chejanovsky Uri Hanania Adi Avni 《Plant physiology》1999,121(2):345-352
Ethylene-inducing xylanase (EIX) elicits plant defense responses in certain tobacco (Nicotiana tabacum) and tomato cultivars in addition to its xylan degradation activity. It is not clear, however, whether elicitation occurs by cell wall fragments released by the enzymatic activity or by the xylanase protein interacting directly with the plant cells. We cloned the gene encoding EIX protein and overexpressed it in insect cells. To determine the relationship between the two activities, substitution of amino acids in the xylanase active site was performed. Substitution at glutamic acid-86 or -177 with glutamine (Gln), aspartic acid (Asp), or glycine (Gly) inhibited the β-1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177 also lost the ability to induce the hypersensitive response and ethylene biosynthesis. However, mutants having Gln-86, Gly-86, Asp-177, or Gly-177 retained ability to induce ethylene biosynthesis and the hypersensitive response. Our data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter. 相似文献
317.
Endophytic fungi have been shown to be a promising source of biologically active natural products. In the present study, extracts of four endophytic fungi isolated from plants of the National Park, Pahang were evaluated for their cytotoxic activity and the nature of their active compounds determined. Those extracts exhibiting activity with IC(50) values less than 17 μg/ml against HCT116, MCF-7 and K562 cell lines were shown to induce apoptosis in these cell lines. Molecular analysis, based on sequences of the rDNA internal transcribed spacers ITS1 and ITS4, revealed all four endophytic fungi to be ascomycetes: three sordariomycetes and a dothideomycete. Six known compounds, cytochalasin J, dechlorogriseofulvin, demethylharzianic-acid, griseofulvin, harzianic acid and 2-hexylidene-3-methyl-succinic acid were identified from a rapid dereplication technique for fungal metabolites using an in-house UV library. The results from the present study suggest the potential of endophytic fungi as cytotoxic agents, and there is an indication that the isolates contain bioactive compounds that mainly kill cancer cells by apoptosis. 相似文献
318.
319.
320.
Katarina Norén Maria Kempe 《International journal of peptide research and therapeutics》2009,15(4):287-292
The synthesis of multilayered magnetic nanoparticles (MNPs) for use as a support in solid-phase peptide synthesis (SPPS) is
described. Silanization of magnetite (Fe3O4) nanoparticles with 3-(trimethoxysilyl)propyl methacrylate introduced polymerizable groups on the surface. Polymerization
with allylamine, trimethylolpropane trimethacrylate, and trimethylolpropane ethoxylate (14/3 EO/OH) triacrylate provided a
polymeric coating and amino groups to serve as starting points for the synthesis. After coupling of an internal reference
amino acid and a cleavable linker, the coated MNPs were applied as the solid phase during synthesis of Leu-enkephalinamide
and acyl carrier protein (65-74) by Fmoc chemistry. A “high-load” version of the MNP support (0.32 mmol/g) was prepared by
four consecutive cycles of Fmoc-Lys(Fmoc)-OH coupling and Fmoc deprotection. Successful synthesis of Leu-enkephalin was demonstrated
on the “high-load” MNPs. Chemical stability studies proved the particles to be stable under SPPS conditions and magnetization
measurements showed that the magnetic properties of the particles were maintained throughout derivatizations and SPPS. The
MNPs were further characterized by high-resolution transmission electron microscopy, inductively coupled plasma atomic emission
spectrometry, elemental analysis, and nitrogen gas adsorption measurements. 相似文献