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61.
The transposable elements of the Drosophila melanogaster euchromatin: a genomics perspective 下载免费PDF全文
Kaminker JS Bergman CM Kronmiller B Carlson J Svirskas R Patel S Frise E Wheeler DA Lewis SE Rubin GM Ashburner M Celniker SE 《Genome biology》2002,3(12):research0084.1-842
Background
Transposable elements are found in the genomes of nearly all eukaryotes. The recent completion of the Release 3 euchromatic genomic sequence of Drosophila melanogaster by the Berkeley Drosophila Genome Project has provided precise sequence for the repetitive elements in the Drosophila euchromatin. We have used this genomic sequence to describe the euchromatic transposable elements in the sequenced strain of this species.Results
We identified 85 known and eight novel families of transposable element varying in copy number from one to 146. A total of 1,572 full and partial transposable elements were identified, comprising 3.86% of the sequence. More than two-thirds of the transposable elements are partial. The density of transposable elements increases an average of 4.7 times in the centromere-proximal regions of each of the major chromosome arms. We found that transposable elements are preferentially found outside genes; only 436 of 1,572 transposable elements are contained within the 61.4 Mb of sequence that is annotated as being transcribed. A large proportion of transposable elements is found nested within other elements of the same or different classes. Lastly, an analysis of structural variation from different families reveals distinct patterns of deletion for elements belonging to different classes.Conclusions
This analysis represents an initial characterization of the transposable elements in the Release 3 euchromatic genomic sequence of D. melanogaster for which comparison to the transposable elements of other organisms can begin to be made. These data have been made available on the Berkeley Drosophila Genome Project website for future analyses. 相似文献62.
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Vegetative and generative dispersal capacity of field released transgenic aspen trees 总被引:2,自引:0,他引:2
Matthias?FladungEmail author Olaf?Nowitzki Birgit?Ziegenhagen Sandeep?Kumar 《Trees - Structure and Function》2003,17(5):412-416
Transfer of genes by pollen or wind-dispersed seed is considered a main potential risk when field release experiments with transgenic trees are initiated. In Germany, the first release experiment with genetically transformed trees was initiated in 1996. To ensure that the transgenic trees remained in the vegetative phase, the duration of the experiment was limited to 5 years. In total, 457 1-year-old trees including eight transgenic aspen lines carrying either the 35S- rolC or the rbcS- rolC gene construct, and three control clones were transferred to the field. In 1998 and 2000, 12 plants of transgenic lines all carrying the 35S- rolC gene construct formed female flower buds. Furthermore, one young aspen plant identified as a root sucker was observed in 1999 followed by an increasing number of root suckers derived from transgenic and non-transgenic trees in 2000 and 2001. In 2001, the last year of the field trial, 15 root suckers were detected outside the field. In total, 234 root suckers were harvested in 2000 and 2001 and analysed for their transgenic status. More than half of the roots suckers investigated showed the presence of the rbcS- rolC gene construct. We concluded that in addition to the widely accepted generative propagation, vegetative dispersal capacity of transgenic perennial plants is also important and must be included in risk assessment studies. 相似文献
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Rifampicin (Rif) is a first line drug used for tuberculosis treatment. However, the emergence of drug resistant strains has necessitated synthesis and testing of newer analogs of Rif. Mycobacterium smegmatis is often used as a surrogate for M. tuberculosis. However, the presence of an ADP ribosyltransferase (Arr) in M. smegmatis inactivates Rif, rendering it impractical for screening of Rif analogs or other compounds when used in conjunction with them (Rif/Rif analogs). Rifampicin is also used in studying the role of various DNA repair enzymes by analyzing mutations in RpoB (a subunit of RNA polymerase) causing Rif resistance. These analyses use high concentrations of Rif when M. smegmatis is used as model. Here, we have generated M. smegmatis strains by deleting arr (Δarr). The M. smegmatis Δarr strains show minimum inhibitory concentration (MIC) for Rif which is similar to that for M. tuberculosis. The MICs for isoniazid, pyrazinamide, ethambutol, ciprofloxacin and streptomycin were essentially unaltered for M. smegmatis Δarr. The growth profiles and mutation spectrum of Δarr and, Δarr combined with ΔudgB (udgB encodes a DNA repair enzyme that excises uracil) strains were similar to their counterparts wild-type for arr. However, the mutation spectrum of ΔfpgΔarr strain differed somewhat from that of the Δfpg strain (fpg encodes a DNA repair enzyme that excises 8-oxo-G). Our studies suggest M. smegmatis Δarr strain as an ideal model system in drug testing and mutation spectrum determination in DNA repair studies. 相似文献
68.
Saikat Boliar Supratik Das Manish Bansal Brihaspati N. Shukla Shilpa Patil Tripti Shrivastava Sweety Samal Sandeep Goswami C. Richter King Jayanta Bhattacharya Bimal K. Chakrabarti 《PloS one》2015,10(3)
An ideal HIV-1 Env immunogen is expected to mimic the native trimeric conformation for inducing broadly neutralizing antibody responses. The native conformation is dependent on efficient cleavage of HIV-1 Env. The clade B isolate, JRFL Env is efficiently cleaved when expressed on the cell surface. Here, for the first time, we report the identification of a native clade C Env, 4-2.J41 that is naturally and efficiently cleaved on the cell surface as confirmed by its biochemical and antigenic characteristics. In addition to binding to several conformation-dependent neutralizing antibodies, 4-2.J41 Env binds efficiently to the cleavage-dependent antibody PGT151; thus validating its native cleaved conformation. In contrast, 4-2.J41 Env occludes non-neutralizing epitopes. The cytoplasmic-tail of 4-2.J41 Env plays an important role in maintaining its conformation. Furthermore, codon optimization of 4-2.J41 Env sequence significantly increases its expression while retaining its native conformation. Since clade C of HIV-1 is the prevalent subtype, identification and characterization of this efficiently cleaved Env would provide a platform for rational immunogen design. 相似文献
69.
Nitrogen fertilizer and landscape position impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass 下载免费PDF全文
Eric G. Mbonimpa Chang O. Hong Vance N. Owens R. Michael Lehman Shannon L. Osborne Thomas E. Schumacher David E. Clay Sandeep Kumar 《Global Change Biology Bioenergy》2015,7(4):836-849
This study was conducted to evaluate the impacts of N fertilizer and landscape position on carbon dioxide (CO2) and methane (CH4) fluxes from a US Northern Great Plains landscape seeded to switchgrass (Panicum virgatum L.). The experimental design included three N levels (low, 0 kg N ha−1; medium, 56 kg N ha−1; and high, 112 kg N ha−1) replicated four times. The experiment was repeated at shoulder and footslope positions. Soil CO2 and CH4 fluxes were monitored once every 2 weeks from May 2010 to October 2012. The CO2 fluxes were 40% higher at the footslope than the shoulder landscape position, and CH4 fluxes were similar in both landscape positions. Soil CO2 and CH4 fluxes averaged over the sampling dates were not impacted by N rates. Seasonal variations showed highest CO2 release and CH4 uptake in summer and fall, likely due to warmer and moist soil conditions. Higher CH4 release was observed in winter possibly due to increased anaerobic conditions. However, year to year (2010–2012) variations in soil CO2 and CH4 fluxes were more pronounced than the variations due to the impact of landscape positions and N rates. Drought conditions reported in 2012, with higher annual temperature and lower soil moisture than long-term average, resulted in higher summer and fall CO2 fluxes (between 1.3 and 3 times) than in 2011 and 2010. These conditions also promoted a net CH4 uptake in 2012 in comparison to 2010 when there was net CH4 release. Results from this study conclude that landscape positions, air temperature, and soil moisture content strongly influenced soil CO2 fluxes, whereas soil moisture impacted the direction of CH4 fluxes (uptake or release). However, a comprehensive life cycle analysis would be appropriate to evaluate environmental impacts associated with switchgrass production under local environmental conditions. 相似文献
70.
Sanjay Basu Christopher Millett Sandeep Vijan Rodney A. Hayward Sanjay Kinra Rahoul Ahuja John S. Yudkin 《PLoS medicine》2015,12(5)