全文获取类型
收费全文 | 854篇 |
免费 | 74篇 |
国内免费 | 62篇 |
出版年
2023年 | 27篇 |
2022年 | 37篇 |
2021年 | 26篇 |
2020年 | 71篇 |
2019年 | 64篇 |
2018年 | 42篇 |
2017年 | 30篇 |
2016年 | 39篇 |
2015年 | 43篇 |
2014年 | 60篇 |
2013年 | 83篇 |
2012年 | 51篇 |
2011年 | 48篇 |
2010年 | 58篇 |
2009年 | 46篇 |
2008年 | 39篇 |
2007年 | 41篇 |
2006年 | 27篇 |
2005年 | 32篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有990条查询结果,搜索用时 15 毫秒
121.
Akio Shimizu Kagayaki Morishima Masahiro Kobayashi Masahiko Kunimoto Ichiro Nakayama 《Journal of applied phycology》2008,20(1):83-88
Conchospore germlings of Porphyra yezoensis were stained with a fluorescent dye for DNA and observed with confocal laser scanning microscopy (CLSM). Relative DNA values
of the germling nuclei were obtained by measuring fluorescence intensities of nuclear regions of the optically sliced specimens,
using the mean value of the smallest blade cells as a reference of the genomic n value. Such quantification revealed that the nuclear DNA amounts of the one-cell, two-cell, and four-cell-stage germlings
are approximately 4 × n, 2 × n, and n ∼2 × n values respectively; these values agreed well with the expected ones from the hypothesis that meiosis corresponds to the
first successive cell divisions after the conchospore germination. These results are consistent with a previous study on cytogenetic
analysis of the chimaera blade formation (Ohme and Miura 1988, Plant Sci 57:135–140) and not consistent with a recent microscopic study (Wang et al. 2006, Phycol Res 54:201–207) which proposed that the first meiotic division occurs at the conchospore formation and the second
division at the germination. 相似文献
122.
A simple and accurate method involving high-performance liquid chromatography with evaporative light scattering detection was developed for the simultaneous determination of five triterpenoid saponin components in Clematis L. spp. for the first time. The analysis was performed on a Zorbax SB-C(18) column and gradient elution with acetonitrile and water with 0.1% formic acid was utilised. All the calibration curves exhibited good linear characteristics with correlation coefficients in the range from 0.9979 to 0.9997. The limits of detection and limits of quantification were less than 0.152 and 0.506 microg, respectively. The overall recoveries for the five analytes were between 91.3 and 99.5%. A total of 10 samples from Clematis L. spp. were analysed under optimised conditions and the chemical profiles provided information for the identification of botanical origin, the development of new medicinal resources and chemotaxonomic investigation. 相似文献
123.
Jong Wan Park Ho Sub Jung Hea Yeon Lee Tomoji Kawai 《Biotechnology and Bioprocess Engineering》2005,10(6):505-509
For the purpose of developing a direct label-free electrochemical detection system, we have systematically investigated the
electrochemical signatures of each step in the preparation procedure, from a bare gold electrode to the hybridization of label-free
complementary DNA, for the streptavidin-modified electrode. For the purpose of this investigation, we obtained the following
pertinent data; cyclic voltammogram measurements, electrochemical impedance spectra and square wave voltammogram measurements,
in Fe(CN)6
3−/Fe(CN)6
4− solution (which was utilized as the electron transfer redox mediator). The oligonucleotide molecules on the streptavidin-modified
electrodes exhibited intrinsic redox activity in the ferrocyanide-mediated electrochemical measurements. Furthermore, the
investigation of electrochemical electron transfer, according to the sequence of oligonucleotide molecules, was also undertaken.
This work demonstrates that direct label-free oligonucleotide electrical recognition, based on biofunctional streptavidin-modified
gold electrodes, could lead to the development of a new biosensor protocol for the expansion of rapid, cost-effective detection
systems. 相似文献
124.
ABSTRACT In this article, we marshal qualitative and quantitative evidence for a distinctive U.S. working-class perspective that criticizes and dissents from the society's consumerist orthodoxy. On the basis of ethnographic and archival research in white central New York and eastern Pennsylvania, Doukas suggested that the frugal, work-centered ideology of historical U.S. working classes—the "gospel of work"—persisted as counterhegemonic in today's "gospel of wealth" consumerism. Durrenberger quantitatively tested for "gospel of work" orientations and found confirmation among predominantly white central Pennsylvanian labor unionists. We argue that the combination of methods warrants a more confident generalization and that the "wage of whiteness" needs to be assessed in regional and historic context. We conclude that "gospel of work" values are widely held despite a century-long corporate-sponsored campaign to promote consumerism and caution against assuming consumerist hegemony in the United States. 相似文献
125.
Amine-reactive isobaric tagging reagents such as iTRAQ (isobaric tags for relative and absolute quantitation) have recently become increasing popular for relative protein quantification, cell expression profiling, and biomarker discovery. This is due mainly to the possibility of simultaneously identifying and quantifying multiple samples. The principles of iTRAQ may also be applied to absolute protein quantification with the use of synthetic peptides as standards. The prerequisites that must be fulfilled to perform absolute quantification of proteins by iTRAQ have been investigated and are described here. Three samples of somatropin were quantified using iTRAQ and synthetic peptides as standards, corresponding to a portion of the protein sequence. The results were compared with those obtained by quantification of the same protein solutions using double exact matching isotope dilution mass spectrometry (IDMS). To obtain reliable results, the appropriate standard peptides needed to be selected carefully and enzymatic digestion needed to be optimized to ensure complete release of the peptides from the protein. The kinetics and efficiency of the iTRAQ derivatization reaction of the standard peptides and digested proteins with isobaric tagging reagents were studied using a mixture of seven synthetic peptides and their corresponding labeled peptides. The implications of incomplete derivatization are also presented. 相似文献
126.
127.
128.
C L Eriksson de Rezende E T Mallinson A Gupte S W Joseph 《Journal of industrial microbiology & biotechnology》2001,26(4):222-225
Controlling water activity (a
w) can significantly impact the growth of Salmonella in poultry litter and manure — a phenomenon that was studied quantitatively using two common serotypes of Salmonella. The quantitative effect of changes in levels of a
w on Salmonella populations was determined using inoculated, frosted glass rectangles placed in closed chambers (microcosms). Glass rectangles
with known concentrations of Salmonella enteritidis and S. brandenburg were placed in microcosms maintained at an a
w level of 0.893 for 24 h at room temperature (RT) and then transferred to other microcosms maintained at the same temperature
but with higher a
w levels (0.932 and 0.987). Salmonella populations on the slides were quantified at 4, 18, 24, and 48 h. Slightly elevated levels of a
w (<0.1, i.e., 10% equilibrium relative humidity) for 24 h resulted in a 100-fold increase in counts of Salmonella. The data also suggested that in vitro adaptation to dry environments may occur when the organisms are exposed to alternating levels of relatively high and low
(0.987 and 0.893) levels of a
w. Any increased tolerance of Salmonella to reduced levels of a
w could be the result of physico-chemical changes in the organism due to selective environmental pressure, formation of a protective
biofilm, and/or entry into a dormant state. Results from this study are compatible with those from previously reported on-farm
surveys, reinforcing the contention that maintaining a
w below 0.85 in and around litter/manure surfaces in poultry or livestock bedding areas may be a critical factor in safe production
of food. Journal of Industrial Microbiology & Biotechnology (2001) 26, 222–225.
Received 18 May 2000/ Accepted in revised form 24 January 2001 相似文献
129.
《Molecular & cellular proteomics : MCP》2022,21(12):100441
- Download : Download high-res image (178KB)
- Download : Download full-size image
130.
《Molecular & cellular proteomics : MCP》2022,21(10):100281
Spermatozoa are central to fertilization and the evolutionary fitness of sexually reproducing organisms. As such, a deeper understanding of sperm proteomes (and associated reproductive tissues) has proven critical to the advancement of the fields of sexual selection and reproductive biology. Due to their extraordinary complexity, proteome depth-of-coverage is dependent on advancements in technology and related bioinformatics, both of which have made significant advancements in the decade since the last Drosophila sperm proteome was published. Here, we provide an updated version of the Drosophila melanogaster sperm proteome (DmSP3) using improved separation and detection methods and an updated genome annotation. Combined with previous versions of the sperm proteome, the DmSP3 contains a total of 3176 proteins, and we provide the first label-free quantitation of the sperm proteome for 2125 proteins. The top 20 most abundant proteins included the structural elements α- and β-tubulins and sperm leucyl-aminopeptidases. Both gene content and protein abundance were significantly reduced on the X chromosome, consistent with prior genomic studies of X chromosome evolution. We identified 9 of the 16 Y-linked proteins, including known testis-specific male fertility factors. We also identified almost one-half of known Drosophila ribosomal proteins in the DmSP3. The role of this subset of ribosomal proteins in sperm is unknown. Surprisingly, our expanded sperm proteome also identified 122 seminal fluid proteins (Sfps), proteins originally identified in the accessory glands. We show that a significant fraction of ‘sperm-associated Sfps’ are recalcitrant to concentrated salt and detergent treatments, suggesting this subclass of Sfps are expressed in testes and may have additional functions in sperm, per se. Overall, our results add to a growing landscape of both sperm and seminal fluid protein biology and in particular provides quantitative evidence at the protein level for prior findings supporting the meiotic sex-chromosome inactivation model for male-specific gene and X chromosome evolution. 相似文献