全文获取类型
收费全文 | 1472篇 |
免费 | 165篇 |
国内免费 | 1篇 |
出版年
2023年 | 8篇 |
2022年 | 9篇 |
2021年 | 24篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 33篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 81篇 |
2014年 | 86篇 |
2013年 | 91篇 |
2012年 | 116篇 |
2011年 | 74篇 |
2010年 | 50篇 |
2009年 | 61篇 |
2008年 | 63篇 |
2007年 | 75篇 |
2006年 | 65篇 |
2005年 | 65篇 |
2004年 | 63篇 |
2003年 | 55篇 |
2002年 | 67篇 |
2001年 | 26篇 |
2000年 | 40篇 |
1999年 | 28篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1974年 | 6篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1969年 | 10篇 |
1965年 | 6篇 |
排序方式: 共有1638条查询结果,搜索用时 15 毫秒
1.
2.
The non-recombining nature of the Y-chromosome determines the non-independence of alleles between loci. The evolution of short tandem repeat (STR) loci in the Y-chromosome is the result of different factors such as differential mutation rates, mutation modes, gene conversion, selection and demographic processes. The degree of correlation between loci is dependent on the magnitude of these processes. The simulation of data is a routine tool used for testing hypotheses in population and evolutionary studies. The most basic parameters hitherto used in lineage haplotype simulations are the allele frequency distributions and mutation rates, assuming either full independence or linkage between loci. In this study we introduce use of the Spearman correlation coefficient to estimate the degree of dependence between non-recombining loci. Then, both the interdependence between loci and the allele frequency distributions at multi-allelic loci are incorporated in an algorithm for simulating haplotypes. We illustrate the method using published and unpublished Y-chromosome STR data. 相似文献
3.
4.
Frank M. Maas Luit J. de Kok Ingrid Hoffmann Pieter J. C. Kuiper 《Physiologia plantarum》1987,70(4):713-721
Exposure of spinach (Spinacia oleracea L. cv. Monosa) to 0.25 μl l?1 H2S reduced the relative growth rate by 26, 47 and 60% at 15, 18 and 25°C, respectively. Shoot to root ratio decreased in plants fumigated at 18 and 25°C. Growth of spinach was not affected by a 2-week exposure to 0.10 or 0.25 μl l?1 SO2. Both H2S and SO2 fumigation increased the content of sulfhydryl compounds and sulfate. A 2-week exposure to 0.25 μl l?1 H2S resulted in an increase in sulfhydryl and sulfate content of 250 to 450% and 63 to 248% in the shoots, respectively, depending on growth temperature. Exposure to 0.15 and 0.30 μl l?1 H2S at 20°C for 2 weeks resulted in a 46% increase in sulfate content of the shoots at 0.30 μl l?1 and no detectable increase at 0.15 μl l?1 H2S; the sulfate content of the roots increased by 195 and 145% at 0.15 and 0.30 μl l?1 H2S, respectively. Fumigation with 0.25 μl l?1 SO2 at 20°C for 2 weeks resulted in an increase in sulfhydryl content and sulfate content in the shoots of 285% and 300 to 1100%. H2S fumigation during the 12 h light period or only during the dark period resulted in identical growth reduction and accumulation of sulfhydryl compounds; they were about 50 and 67% of those observed in continuously exposed plants. H2S- and SO2-exposed plants showed an increased transpiration rate, which was mainly caused by an increased dark-period transpiration. No effect of H2S and SO2 on the water uptake of the plants and the osmotic potential of the leaves was detected. Plants fumigated with 0.25 μl l?1 H2S for 2 weeks were smaller and differed morphologically from the control plants by slightly more abaxially curved leaf margins. Cross sections of the leaves showed smaller cells at the margins and smaller and fewer air spaces. The increased transpiration in the H2S-exposed plants is discussed in relation to the observed morphological changes. 相似文献
5.
Quantitative electroelution of oligonucleotides and large DNA fragments from gels and purification by electrodialysis 总被引:5,自引:0,他引:5
We have designed a new device [Biotrap (Elutrap in the U.S.A. and Canada), available from Schleicher & Schuell] for electroelution, -concentration , and -dialysis of DNA and other charged macromolecules above 5 kDa. In an electric field, the DNA migrates in an open channel out of the gel slice through a microporous membrane, BT2, into the trap section, where it is retained by a very dense, non-adsorbant, and inert membrane BT1. Specifically designed for use in an electric field, the matrix of this new membrane is much denser than that of dialysis membranes. In contrast to dialysis membranes, BT1 will not adsorb large DNA fragments nor allow passage of small DNA fragments when subjected to an electric field. In the absence of an electric field, BT1 and BT2 effectively seal the trap, maintaining the final elution volume of the purified sample. The trap can contain from 200-600 microliter and is collected from above with a pipet. In the experiments described here, 85-95% of oligonucleotides (14-mer) and large (150 kb) DNA fragments were recovered, independent of fragment length. The purity of the eluted DNA was demonstrated by restriction enzyme digestion, nick-translation, primer extension, end-labeling with polynucleotide kinase, and ligation. Electrodialysis was successfully used for the complete removal of common contaminants inhibiting the polynucleotide kinase reaction and for the removal of CsCl from DNA samples. 相似文献
6.
T M Slaghek M J van Vliet A A Maas J P Kamerling J F Vliegenthart 《Carbohydrate research》1989,195(1):75-86
4-Methoxybenzyl 2,4-di-O-benzyl-3-O-[2,4,6-tri-O-benzyl-3-O-(3,4,6-tri-O-benzyl-alpha-D- galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L-rhamnopyranoside (22), a building block for the alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap fragment of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B [----2)-alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap-( 1----X)-D- RibOH-(5-P----]n (6A, X = 3; 6B, X = 4) has been synthesised. Ethyl 3-O-allyl-2,4,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside was coupled with 4-methoxybenzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside in ether, using methyl triflate as promoter. The resulting alpha-D-Glcp-(1----3)-alpha-L-Rhap derivative was deallylated with KOBut in N,N-dimethylformamide followed by 0.1M HCl in 9:1 acetone-water. The product was coupled with 3,4,6-tri-O-acetyl-2-O-allyl-alpha,beta-D-galactopyranosyl trichloroacetimidate in ether, using trimethylsilyl triflate, to yield 19. Deacetylation, benzylation, and deallylation then gave 22. 相似文献
7.
Sodium lactate delays toxin production by Clostridium botulinum in cook-in-bag turkey products.
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Comminuted raw turkey, containing 1.4% sodium chloride, 0.3% sodium phosphate, and 0 (control), 2.0, 2.5, 3.0, or 3.5% sodium lactate, was inoculated with a 10-strain mixture of proteolytic type A and B Clostridium botulinum spores. The inoculated turkey was vacuum packaged and cooked by immersion in heated water to an internal temperature of 71.1 degrees C. Samples were incubated at 27 degrees C for up to 10 days. Five samples per treatment were examined for botulinal toxin at specific intervals. Sodium lactate exhibited an antibotulinal effect which was concentration dependent. Processed turkey containing 0, 2.0, 2.5, 3.0, or 3.5% sodium lactate was toxic after 3, 4 to 5, 4 to 6, 7 or 7 to 8 days, respectively. Subsequent studies with a broth medium revealed that lactate, not the sodium ion, was the principal factor in delaying botulinal-toxin formation. 相似文献
8.
Many soybean [Glycine max (L.) Merr.] genotypes that are grown in solution cultures are highly sensitive to the combination of both salinity and inorganic
phosphate (Pi) in the substrate. This effect has been observed on numerous occasions on plants grown in a saline medium that
contained a substantial amount of Ca (i.e., CaCl2/NaCl=0.5 on a molar basis). Because Ca is important in regulating ion transport and membrane permeability, solution culture
experiments were designed to examine the effects of various concentrations of Pi and ratios of CaCl2/NaCl (0 to 0.5 on a molar basis) at a constant osmotic potential (−0.34 MPa) on this adverse interaction. Four soybean cultivars
(‘Lee’, ‘Lee 74’ ‘Clark’ and ‘Clark 63’) were tested.
No adverse salinity x Pi interaction was found on Lee at any ratio and leaf P and Cl were maintained below 300 and 200 mmol
kg−1 dry wt, respectively. Clark, Clark 63 and Lee 74 soybean plants, on the other hand, were severely injured by solution salinity
(−0.34 MPa osmotic potential) when substrate Pi was ≥0.12 mM. Reduced substrate Ca did not intensify the salinity x Pi interaction. On the contrary, the onset of injury was hastened
and more severe with increased CaCl2/NaCl ratios in isotonic solutions. Shoot and root growth rates decreased as injury increased. Leaf P concentrations from
these cultivars grown in saline solutions with 0.12 mM Pi were excessive (>600 mmol kg−1 dry wt) compared with concentrations commonly found in soybean leaf tissue yet they were independent of the severity of injury.
Since leaf Cl increased wiht increased CaCl2/NaCl ratio, we suspect that the severity of foliar injury was related to the combined effects of excessive P and Cl within
the tissue. Lee 74, the only injured cultivar examined that excluded Cl from its leaves, was less sensitive than either Clark
cultivar and its injury was characteristically different. Other ion interactions were reported that may have played a role
in injury susceptibility. 相似文献
9.
Of the nine species of Tropodiaptomus occurring in Equatorial East Africa, seven are redescribed and figured in great detail. Their relationships are discussed. A primary homonym is eliminated, and types are indicated wherever possible. 相似文献
10.
Koen Martens 《Hydrobiologia》1985,124(1):81-83
Salinity tolerance, and the effects of temperature upon it, of the Australian ostracod Mytilocypris henricae (Chapman) was determined in direct transfer experiments using adults. Animals were subjected to a combination of 11 salinities (ranging between 0.0 g · 1–1 and 45.0 g · 1–1) and 4 temperatures (10, 15, 20 and 25 °C). Survival was analysed using two statistical techniques: the logit linear model and the proportional hazards model. Results show that both salinity and temperature have a significant effect on survival, but there is no significant interaction between temperature and salinity. 相似文献