全文获取类型
收费全文 | 1143篇 |
免费 | 101篇 |
出版年
2023年 | 9篇 |
2021年 | 18篇 |
2020年 | 26篇 |
2019年 | 12篇 |
2018年 | 19篇 |
2017年 | 16篇 |
2016年 | 32篇 |
2015年 | 47篇 |
2014年 | 69篇 |
2013年 | 71篇 |
2012年 | 81篇 |
2011年 | 90篇 |
2010年 | 51篇 |
2009年 | 47篇 |
2008年 | 75篇 |
2007年 | 65篇 |
2006年 | 45篇 |
2005年 | 67篇 |
2004年 | 50篇 |
2003年 | 46篇 |
2002年 | 50篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1969年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有1244条查询结果,搜索用时 17 毫秒
1.
2.
Dominic A. Edward Jocelyn Poissant Alastair J. Wilson Tracey Chapman 《Evolution; international journal of organic evolution》2014,68(6):1651-1660
Many reproductive traits that have evolved under sexual conflict may be influenced by both sexes. Investigation of the genetic architecture of such traits can yield important insight into their evolution, but this entails that the heritable component of variation is estimated for males and females—as an interacting phenotype. We address the lack of research in this area through an investigation of egg production and copula duration in the fruit fly, Drosophila melanogaster. Despite egg production rate being determined by both sexes, which may cause sexual conflict, an assessment of this trait as an interacting phenotype is lacking. It is currently unclear whether copula duration is determined by males and/or females. We found significant female, but not male, genetic variance for egg production rate that may indicate reduced potential for ongoing sexually antagonistic coevolution. In contrast, copula duration was determined by significant genetic variance in both sexes. We also identified genetic variation in egg retention among virgin females. Although previously identified in wild populations, it is unclear why this should be present in a laboratory stock. This study provides a novel insight into the shared genetic architecture of reproductive traits that are the subject of sexual conflict. 相似文献
3.
Kim Y. Hung Themis J. Michailides Jocelyn G. Millar Astri Wayadande Alec C. Gerry 《PloS one》2015,10(5)
House flies are of major concern as vectors of food-borne pathogens to food crops. House flies are common pests on cattle feedlots and dairies, where they develop in and feed on animal waste. By contacting animal waste, house flies can acquire human pathogenic bacteria such as Escherichia coli and Salmonella spp., in addition to other bacteria, viruses, or parasites that may infect humans and animals. The subsequent dispersal of house flies from animal facilities to nearby agricultural fields containing food crops may lead to pre-harvest food contamination with these pathogens. We hypothesized that odors from honeydew, the sugary excreta produced by sucking insects feeding on crops, or molds and fungi growing on honeydew, may attract house flies, thereby increasing the risk of food crop contamination. House fly attraction to honeydew-contaminated plant material was evaluated using a laboratory bioassay. House flies were attracted to the following plant-pest-honeydew combinations: citrus mealybug on squash fruit, pea aphid on faba bean plants, whitefly on navel orange and grapefruit leaves, and combined citrus mealybug and cottony cushion scale on mandarin orange leaves. House flies were not attracted to field-collected samples of lerp psyllids on eucalyptus plants or aphids on crepe myrtle leaves. Fungi associated with field-collected honeydews were isolated and identified for further study as possible emitters of volatiles attractive to house flies. Two fungal species, Aureobasidium pullulans and Cladosporium cladosporioides, were repeatedly isolated from field-collected honeydew samples. Both fungal species were grown in potato dextrose enrichment broth and house fly attraction to volatiles from these fungal cultures was evaluated. House flies were attracted to odors from A. pullulans cultures but not to those of C. cladosporioides. Identification of specific honeydew odors that are attractive to house flies could be valuable for the development of improved house fly baits for management of this pest species. 相似文献
4.
Equine red blood cells were washed in saline heavy water (2H2O) to exchange the hydrogen atoms of the non-hemoglobin components with deuterons. This led to novel neutron scattering measurements of protein vibrations within a cellular system and permitted a comparison with inelastic neutron scattering measurements on purified horse hemoglobin, either dry or wetted with 2H2O. As a function of wavevector transfer Q and the frequency transfer v the neutron response typified by the dynamic structure factor S(Q, v) was found to be similar for extracted and cellular hemoglobin at low and high temperatures. At 77 K, in the cells, a peak in S(Q, v) due to the protein was found near 0.7 THz, approximately half the frequency of a strong peak in the aqueous medium. Measurements at higher temperatures (170 and 230 K) indicated similar small shifts downwards in the peak frequencies of both components. At 260 K the low frequency component became predominantly quasielastic, but a significant inelastic component could still be ascribed to the aqueous scattering. Near 295 K the frequency responses of both components were similar and centered near zero. When scattering due to water is taken into account it appears that the protein neutron response in, or out of, red blood cells is little affected by hydration in the low frequency regime where Van der Waals forces are thought to be effective. 相似文献
5.
Gene amplification at a locus encoding a putative Na+/H+ antiporter confers sodium and lithium tolerance in fission yeast. 下载免费PDF全文
We have identified a new locus, sodium 2 (sod2) based on selection for increased LiCl tolerance in fission yeast, Schizosaccharomyces pombe. Tolerant strains have enhanced pH-dependent Na+ export capacity and sodium transport experiments suggest that the gene encodes an Na+/H+ antiport. The predicted sod2 gene product can be placed in the broad class of transporters which possess 12 hydrophobic transmembrane domains. The protein shows some sequence similarity to the human and bacterial Na+/H+ antiporters. Overexpression of sod2 increased Na+ export capacity and conferred sodium tolerance. Osmotolerance was not affected and sod2 cells were unaffected for growth in K+. In a sod2 disruption strain cells were incapable of exporting sodium. They were hypersensitive to Na+ or Li+ and could not grow under conditions that approximate pH7. The sod2 gene amplification could be selected stepwise and the degree of such amplification correlated with the level of Na+ or Li+ tolerance. 相似文献
6.
Renato M Salgado Luciane P Capelo Rodolfo R Favaro Jocelyn D Glazier John D Aplin Telma MT Zorn 《Reproductive biology and endocrinology : RB&E》2009,7(1):60
Background
Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination. 相似文献7.
8.
Molecular Analysis of Human, Porcine, and Poultry Enterococcus faecium Isolates and Their erm(B) Genes 下载免费PDF全文
E. De Leener A. Martel E. M. De Graef J. Top P. Butaye F. Haesebrouck R. Willems A. Decostere 《Applied microbiology》2005,71(5):2766-2770
Fifty-nine erm(B)-positive Enterococcus faecium strains isolated from pigs, broilers, and humans were typed using multilocus sequence typing (MLST), and the coding sequence of the erm(B) gene was determined. Identical erm(B) gene sequences were detected in genetically unrelated isolates. Furthermore, genetically indistinguishable strains were found to contain different erm(B) alleles. This may suggest that horizontal exchange of the erm(B) gene between animal and human E. faecium strains or the existence of a common reservoir of erm(B) genes might be more important than direct transmission of resistant strains. 相似文献
9.
10.
Effect of tubulozole, a new synthetic microtubule inhibitor, on the induction of casein gene expression by prolactin 总被引:1,自引:0,他引:1
J L Servely G M Geuens P Martel L M Houdebine M de Brabander 《Biology of the cell / under the auspices of the European Cell Biology Organization》1987,59(2):121-127
Colchicine and related drugs are known to inhibit milk secretion. They are also able to prevent stimulation of casein and DNA synthesis by prolactin in the mammary gland. The present report reports data obtained with tubulozole, a new antimitotic drug. Tubulozole C added to culture medium of isolated rabbit epithelial mammary cells strongly inhibited their multiplication. Simultaneously, at a concentration of 1 microM, it prevented almost completely the induction of beta-casein mRNA. Induced cells were rapidly deinduced by addition of the drug to the medium. A similar inhibition was observed when the induction was obtained with prolactin alone or with its two stimulators insulin and glucocorticoids. Tubulozole T, an isomer of tubulozole C which is known to be ineffective in disrupting microtubules, did not alter prolactin actions. These data and those obtained with other tubulin-binding drugs strongly suggest that the integrity of microtubules is required for prolactin to deliver its message to the mammary cell. 相似文献