全文获取类型
收费全文 | 1461篇 |
免费 | 41篇 |
专业分类
1502篇 |
出版年
2023年 | 25篇 |
2022年 | 28篇 |
2021年 | 47篇 |
2020年 | 32篇 |
2019年 | 48篇 |
2018年 | 39篇 |
2017年 | 42篇 |
2016年 | 48篇 |
2015年 | 48篇 |
2014年 | 96篇 |
2013年 | 106篇 |
2012年 | 110篇 |
2011年 | 147篇 |
2010年 | 87篇 |
2009年 | 67篇 |
2008年 | 85篇 |
2007年 | 82篇 |
2006年 | 80篇 |
2005年 | 70篇 |
2004年 | 66篇 |
2003年 | 55篇 |
2002年 | 45篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有1502条查询结果,搜索用时 10 毫秒
201.
Hydrogen peroxide pretreatment of roots enhanced oxidative stress response of tomato under cold stress 总被引:1,自引:0,他引:1
Özlem Darcansoy İşeri Didem Aksoy Körpe Feride Iffet Sahin Mehmet Haberal 《Acta Physiologiae Plantarum》2013,35(6):1905-1913
In the view of physiological role of H2O2, we investigated whether exogenous H2O2 application would affect short-term cold response of tomato and induce acclimation. Pretreatments were performed by immersing roots into 1 mM H2O2 solution for 1 h when transferring seedlings from seedling substrate to soil (acclimated group). Cold stress (3 °C for 16 h) caused significant reduction in relative water content (RWC) of control and non-acclimated (distilled water treated) groups when compared with unstressed plants. H2O2 promoted maintenance of relatively higher RWC under stress. Anthocyanin level in leaves of acclimated plants under cold stress was significantly higher than that of unstressed control and non-acclimated plants. Malondialdehyde (MDA) levels demonstrated low temperature induced oxidative damage to control and non-acclimated plants. MDA remained around unstressed conditions in acclimated plants, which demonstrate that H2O2 acclimation protected tissues against cold induced lipid peroxidation. H2O2 acclimation caused proline accumulation in roots under cold stress. Ascorbate peroxidase (APX) activity in roots of cold stressed and unstressed H2O2 acclimated plants increased when compared with control and non-acclimated plants, with highest increase in roots of acclimated plants under cold stress. CAT levels in roots of acclimated plants also increased, whereas levels remained unchanged in unstressed plants. Endogenous H2O2 levels significantly increased in roots of control and non-acclimated plants under cold stress. On the other hand, H2O2 content in roots of acclimated plants was significantly lower than control and non-acclimated plants under cold stress. The results presented here demonstrated that H2O2 significantly enhanced oxidative stress response by elevating the antioxidant status of tomato. 相似文献
202.
Molecular Biology Reports - Angiogenesis is a new vessel formation process that plays a role in various physiological and pathological conditions. This process is controlled by the balance between... 相似文献
203.
Sohel Md Mahmodul Hasan Akyuz Bilal Konca Yusuf Arslan Korhan Gurbulak Kutlay Abay Murat Kaliber Mahmut Cinar Mehmet Ulas 《Mammalian genome》2020,31(9-12):309-324
Mammalian Genome - Maternal nutrition during pregnancy is one of the major intrauterine environmental factors that influence fetal development by significantly altering the expression of genes that... 相似文献
204.
205.
206.
Yilmaz M Ara C Isik B Karadag N Yilmaz S Polat A Coban S Duzova H 《Cell biochemistry and function》2007,25(6):625-632
We investigated the protective role of aminoguanidine (AG) in rat liver injury induced by chronic biliary obstruction. Secondary biliary cirrhosis was induced by bile duct ligation for 14 days. Swiss albino rats were divided into three groups: Common bile duct ligated (CBDL) rats; Group A, CBDL rats treated with AG as Group B and simple laparotomy group known as the Sham group; Group C. Group B received 200 mg/kg of AG intraperitoneally daily throughout 14 days. The present data showed decreased gama glutamyl transferase (GGT), aspartate aminotransferase (AST), bilirubin and alanine aminotransferase (ALT) levels in the AG treated rats, when compared with CBDL rats (p < 0.05). In the AG treated rats, tissue levels of malondialdehyde (MDA) were significantly lower than that in CBDL rats (p < 0.001). Although the levels of glutathione (GSH) in AG treated rats were higher and myeloperoxidase (MPO) were lower than that in CBDL rats, the difference was not statistically significant (p > 0.05). The levels of interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were significantly lower and although the levels of interleukin-6 (IL-6) were lower in AG treated rats than that in CBDL rats, the difference was not statistically significant. Administration of AG in the rats with biliary obstruction resulted in inhibition of ductular proliferation and portal inflammation. The present study demonstrates that intraperitoneal administration of AG in CBDL rats maintains antioxidant defenses, reduces liver oxidative and cytokine damage and ductular proliferation and portal inflammation. This effect of AG may be useful in the preservation of liver injury in cholestasis. 相似文献
207.
Skin pigmentation is a human phenotype that varies greatly among human populations and it has long been speculated that this
variation is adaptive. We therefore expect the genes that contribute to these large differences in phenotype to show large
allele frequency differences among populations and to possibly harbor signatures of positive selection. To identify the loci
that likely contribute to among-population human skin pigmentation differences, we measured allele frequency differentiation
among Europeans, Chinese and Africans for 24 human pigmentation genes from 2 publicly available, large scale SNP data sets.
Several skin pigmentation genes show unusually large allele frequency differences among these populations. To determine whether
these allele frequency differences might be due to selection, we employed a within-population test based on long-range haplotype
structure and identified several outliers that have not been previously identified as putatively adaptive. Most notably, we
identify the DCT gene as a candidate for recent positive selection in the Chinese. Moreover, our analyses suggest that it is likely that different
genes are responsible for the lighter skin pigmentation found in different non-African populations.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
208.
Fire resistance of Douglas fir (Pseudotsuga menzieesi) treated with borates and natural extractives 总被引:1,自引:0,他引:1
The objective of this study was to determine fire resistance of Douglas fir (Pseudotsuga menzieesi (Mirb.) Franco) specimens treated with borate supplemented aqueous solutions of brutia pine bark powder, acorn powder, sumach leaf powder, and gall-nut powder. Boric acid (BA) and borax (BX) were used as borates which are the most commonly used fire retardants in wood preservation industry. Natural extractives (brutia pine bark powder, sumach leaf powder, acorn powder, and gall-nut powder) were also used which have toxic efficiency against insects and fungi due to their tannin contents. A commercial treatment compound Tanalith-CBC (copper-borate-chromate), which is an impregnation chemical, is used for comparison. The fire test method was performed in three stages: flame stage, without flame stage, and glowing stage. Results indicated that the lowest temperature for flame stage, without flame stage, and glowing stage were obtained for specimens treated with BA and BX mixture (7:3; weight:weight). The lowest mass loss was found for the specimens treated with a mixture of BA and BX. Natural extractives did not improve fire resistance of the samples. However, boric acid and borax had excellent fire retardant effectiveness over untreated and treated samples with natural extractives. 相似文献
209.
The motif prediction problem is to predict short, conserved subsequences that are part of a family of sequences, and it is a very important biological problem. Gibbs is one of the first successful motif algorithms and it runs very fast compared with other algorithms, and its search behavior is based on the well-studied Gibbs random sampling. However, motif prediction is a very difficult problem and Gibbs may not predict true motifs in some cases. Thus, the authors explored a possibility of improving the prediction accuracy of Gibbs while retaining its fast runtime performance. In this paper, the authors considered Gibbs only for proteins, not for DNA binding sites. The authors have developed iGibbs, an integrated motif search framework for proteins that employs two previous techniques of their own: one for guiding motif search by clustering sequences and another by pattern refinement. These two techniques are combined to a new double clustering approach to guiding motif search. The unique feature of their framework is that users do not have to specify the number of motifs to be predicted when motifs occur in different subsets of the input sequences since it automatically clusters input sequences into clusters and predict motifs from the clusters. Tests on the PROSITE database show that their framework improved the prediction accuracy of Gibbs significantly. Compared with more exhaustive search methods like MEME, iGibbs predicted motifs more accurately and runs one order of magnitude faster. 相似文献
210.
The pathogenic fungus Aspergillus alliaceus has been shown to have potential for the biocontrol of Orobanche spp. (broomrape), a root parasitic plant. The effectiveness of A. alliaceus in reducing Orobanche infection was analysed using pesta granules prepared with different food formulations. The results showed that pesta granules comprising of fungal mycelia/spore mixtures from liquid and solid culture, sclerotia and fungal mycelia reduced Orobanche infection to a greater extent in below ground conditions when applied early and at high doses before crop sowing. In addition, pesta granules eliminated the risk of broomrape contamination within a 0.2–0.3 cm diameter of the granules. The sclerotial pathogenicity of A. alliaceus was compared with those of other fungi reported in other studies. In addition, some morphological and histological studies on the fungal pathogenicity on broomrape plants after infection are presented. The present study reveals the potential of sclerotial A. alliaceus pesta granule applications for long-term broomrape biocontrol under field conditions. 相似文献