全文获取类型
收费全文 | 712篇 |
免费 | 54篇 |
国内免费 | 56篇 |
专业分类
822篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 49篇 |
2021年 | 66篇 |
2020年 | 54篇 |
2019年 | 44篇 |
2018年 | 49篇 |
2017年 | 22篇 |
2016年 | 33篇 |
2015年 | 55篇 |
2014年 | 36篇 |
2013年 | 44篇 |
2012年 | 48篇 |
2011年 | 48篇 |
2010年 | 22篇 |
2009年 | 32篇 |
2008年 | 29篇 |
2007年 | 18篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 2篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1985年 | 4篇 |
1982年 | 2篇 |
排序方式: 共有822条查询结果,搜索用时 0 毫秒
21.
22.
23.
Yu Lichun Zhang Caihui Chen Yuan Li Qian Wang Jing Sun Shuzhen 《Molecular biology reports》2020,47(7):5165-5173
Molecular Biology Reports - Parthenolide (PTL) is a natural product from the shoots of Tanacetum parthenium, which has immunomodulatory effects in multiply type of diseases. This study aimed to... 相似文献
24.
Rong Huang Daifang Wang Shuzhen Liu Longhua Guo Fangfang Wang Zhenyu Lin Bin Qiu Guonan Chen 《Chirality》2013,25(11):751-756
The preparative‐scale separation of chiral compounds is vitally important for the pharmaceutical industry and related fields. Herein we report a simple approach for rapid preparative separation of enantiomers using functional nucleic acids modified gold nanoparticles (AuNPs). The separation of DL‐tryptophan (DL‐Trp) is demonstrated as an example to show the feasibility of the approach. AuNPs modified with enantioselective aptamers were added into a racemic mixture of DL‐Trp. The aptamer‐specific enantiomer (L‐Trp) binds to the AuNPs surface through aptamer‐L‐Trp interaction. The separation of DL‐Trp is then simply accomplished by centrifugation: the precipitate containing L‐Trp bounded AuNPs is separated from the solution, while the D‐Trp remains in the supernatant. The precipitate is then redispersed in water. The aptamer is denatured under 95 °C and a second centrifugation is then performed, resulting in the separation of AuNPs and L‐Trp. The supernatant is finally collected to obtain pure L‐Trp in water. The results show that the racemic mixture of DL‐Trp is completely separated into D‐Trp and L‐Trp, respectively, after 5 rounds of repeated addition of fresh aptamer‐modified AuNPs to the DL‐Trp mixture solution. Additionally, the aptamer‐modified AuNPs can be repeatedly used for at least eight times without significant loss of its binding ability because the aptamer can be easily denatured and renatured in relatively mild conditions. The proposed approach could be scaled up and extended to the separation of other enantiomers by the adoption of other enantioselective aptamers. Chirality 25:751–756, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
25.
Bei Wen Longfei Li Yu Liu Hongna Zhang Xiaoyu Hu Xiao-quan Shan Shuzhen Zhang 《Plant and Soil》2013,362(1-2):345-354
Aims
There is a need to predict trace metal concentration in plant organs at given development stages. The aim of this work was to describe the Cd hyperaccumulation kinetics in the different plant organs, throughout the complete cultivation cycle, independently of a possible soil effect.Methods
Plants of Noccaea caerulescens were exposed in aeroponics to three constantly low Cd concentrations and harvested at 6 to 11 dates, until siliquae formation.Results
Dry matter allocation between roots and shoots was constant over time and exposure concentrations, as well as Cd allocation. However 86 % of the Cd taken up was allocated to the shoots. Senescent rosette leaves showed similar Cd concentrations to the living ones, suggesting no redistribution from old to young organs. The Cd root influx was proportional to the exposure concentration and constant over time, indicating that plant development had no effect on this. The bio-concentration factor (BCF), i.e. [Cd]plant/[Cd2+]solution for the whole plant, roots or shoots was independent of the exposure concentration and of the plant stage.Conclusions
Cadmium uptake in a given plant part could therefore be predicted at any plant stage by multiplying the plant part dry matter by the corresponding BCF and the Cd2+ concentration in the exposure solution. 相似文献26.
Determining differentially expressed genes (DEGs) between biological samples is the key to understand how genotype gives rise to phenotype. RNA-seq and microarray are two main technologies for profiling gene expression levels. However, considerable discrepancy has been found between DEGs detected using the two technologies. Integration data across these two platforms has the potential to improve the power and reliability of DEG detection. We propose a rank-based semi-parametric model to determine DEGs using information across different sources and apply it to the integration of RNA-seq and microarray data. By incorporating both the significance of differential expression and the consistency across platforms, our method effectively detects DEGs with moderate but consistent signals. We demonstrate the effectiveness of our method using simulation studies, MAQC/SEQC data and a synthetic microRNA dataset. Our integration method is not only robust to noise and heterogeneity in the data, but also adaptive to the structure of data. In our simulations and real data studies, our approach shows a higher discriminate power and identifies more biologically relevant DEGs than eBayes, DEseq and some commonly used meta-analysis methods. 相似文献
27.
Xiaojing Kuang Lingling Sun Shuzhen Liu Zhenzhen Zhao Danrui Zhao Song Liu Bing Luo 《Virologica Sinica》2016,(4):306-313
The relationship between the Filaggrin gene(FLG) rs2065955 polymorphism and susceptibility to Epstein-Barr virus(EBV)-associated gastric carcinoma(EBVa GC) and EBV-negative gastric carcinoma(EBVn GC) was investigated in Shandong Province,China.We detected the FLG rs2065955 genotype and allele distribution by using PCR and restriction fragment length polymorphism(RFLP) in 64 EBVa GC,82 EBVn GC,and 111 normal control samples.Immunohistochemistry was used to detect the level of FLG protein in 35 EBVa GC and 51 EBVn GC tumor tissues.Compared with normal controls,the genotype CC and allele C of FLG rs2065955 showed higher frequency in EBVa GC and EBVn GC.There was no significant difference between EBVa GC and EBVn GC in allele distribution of FLG rs2065955,but the genotype CC was found more frequently in EBVa GC than in EBVn GC.The risk of developing either EBVa GC or EBVn GC in genotype CC was higher than in other genotypes.Furthermore,genotype CC of FLG rs2065955 may contribute more to the risk of developing EBVa GC than EBVn GC.There was no significant difference in the expression level of FLG protein between EBVa GC and EBVn GC.In conclusion,the FLG rs2065955 polymorphism was significantly related to gastric carcinoma.Allele C of FLG rs2065955 could be a risk factor for EBVa GC or EBVn GC,while genotype CC of FLG rs2065955 was especially associated with EBVa GC. 相似文献
28.
Polly Campbell Lena Arvalo Heather Martin Charles Chen Shuzhen Sun Ashlee H. Rowe Michael S. Webster Jeremy B. Searle Bret Pasch 《Ecology and evolution》2019,9(22):12886-12896
Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we characterize the incidence of, and potential barriers to, hybridization among three closely related species of grasshopper mice (genus Onychomys). All three species use long‐distance acoustic signals to attract and localize mates; Onychomys arenicola and Onychomys torridus are acoustically similar and morphologically cryptic whereas Onychomys leucogaster is larger and acoustically distinct. We used genotyping‐by‐sequencing (GBS) to test for evidence of introgression in 227 mice from allopatric and sympatric localities in the western United States and northern Mexico. We conducted laboratory mating trials for all species pairs to assess reproductive compatibility, and recorded vocalizations from O. arenicola and O. torridus in sympatry and allopatry to test for evidence of acoustic character displacement. Hybridization was rare in nature and, contrary to prior evidence for O. torridus/O. arenicola hybrids, only involved O. leucogaster and O. arenicola. In contrast, laboratory crosses between O. torridus and O. arenicola produced litters whereas O. leucogaster and O. arenicola crosses did not. Call fundamental frequency in O. torridus and O. arenicola was indistinguishable in allopatry but significantly differentiated in sympatry, a pattern consistent with reproductive character displacement. These results suggest that assortative mating based on a long‐distance signal is an important isolating mechanism between O. torridus and O. arenicola and highlight the importance of behavioral barriers in determining the permeability of species boundaries. 相似文献
29.
Haobin Zhao Xiaoguang Xu Shuzhen Lei Dongyan Shao Chunmei Jiang Junling Shi Yawen Zhang Li Liu Shuzhen Lei Hui Sun Qingsheng Huang 《Journal of cellular physiology》2019,234(5):6414-6427
This study revealed that iturin A-like lipopeptides produced by Bacillus subtillis induced both paraptosis and apoptosis in heterogeneous human epithelial colorectal adenocarcinoma (Caco-2) cells. Autophagy was simultaneously induced in Caco-2 cells treated with iturin A-like lipopeptides at the early stage and inhibited at the later stage. A western blot analysis showed that the lipopeptides induced apoptosis in Caco-2 cells via a mitochondrial-dependent pathway, as indicated by upregulated expression of the apoptotic genes bax and bad and downregulated expression of the antiapoptotic gene bcl-2. The induction of paraptosis in Caco-2 cells was indicated by the occurrence of many cytoplasmic vacuoles accompanied by endoplasmic reticulum (ER) dilatation and mitochondrial swelling and dysfunction. ER stress also occurred with significant increases in reactive oxygen species and Ca2+ levels in cells. Autophagy was detected by a transmission electron microscopy analysis and by upregulated expression of LC3-II and downregulated expression of LC3-I. The inhibition of autophagy at the later stage was shown by upregulated expression of p62. This study revealed the capability of iturin A-like B. subtilis lipopeptides to simultaneously execute antitumor potential via multiple pathways. 相似文献
30.
Zhu Yanji Li Qian Xun Wenlong Chen Yuan Zhang Caihui Sun Shuzhen 《Molecular biology reports》2019,46(4):3809-3816
Molecular Biology Reports - The purpose of our research is to elucidate whether oxLDL activates P2X7R in cultured human podocytes and if the activation of P2X7R leads to podocyte apoptosis.... 相似文献