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991.
992.
Strong pollinator‐mediated selection for increased flower brightness and contrast in a deceptive orchid 下载免费PDF全文
Nina Sletvold Judith Trunschke Mart Smit Jeffrey Verbeek Jon Ågren 《Evolution; international journal of organic evolution》2016,70(3):716-724
Contrasting flower color patterns that putatively attract or direct pollinators toward a reward are common among angiosperms. In the deceptive orchid Anacamptis morio, the lower petal, which makes up most of the floral display, has a light central patch with dark markings. Within populations, there is pronounced variation in petal brightness, patch size, amount of dark markings, and contrast between patch and petal margin. We tested whether pollinators mediate selection on these color traits and on morphology (plant height, number of flowers, corolla size, spur length), and whether selection is consistent with facilitated or negative frequency‐dependent pollination. Pollinators mediated strong selection for increased petal brightness (Δβpoll = 0.42) and contrast (Δβpoll = 0.51). Pollinators also tended to mediate stabilizing selection on brightness (Δγpoll = –0.27, n.s.) favoring the most common phenotype in the population. Selection for reduced petal brightness among hand‐pollinated plants indicated a fitness cost associated with brightness. The results demonstrate that flower color traits influence pollination success and seed production in A. morio, indicating that they affect attractiveness to pollinators, efficiency of pollen transfer, or both. The documented selection is consistent with facilitated pollination and selection for color convergence toward cooccurring rewarding species. 相似文献
993.
Photosynthetic organisms need protection against excessive light. By using non‐photochemical quenching, where the excess light is converted into heat, the organism can survive at higher light intensities. This process is partly initiated by the formation of zeaxanthin, which is achieved by the de‐epoxidation of violaxanthin and antheraxanthin to zeaxanthin. This reaction is catalyzed by violaxanthin de‐epoxidase (VDE). VDE consists of three domains of which the central lipocalin‐like domain has been the most characterized. By truncating the domains surrounding the lipocalin‐like domain, we show that VDE activity is possible without the C‐terminal domain but not without the N‐terminal domain. The N‐terminal domain shows no VDE activity by itself but when separately expressed domains are mixed, VDE activity is possible. This shows that these domains can be folded separately and could therefore be studied separately. An increase of the hydrodynamic radius of wild‐type VDE was observed when pH was lowered toward the pH required for activity, consistent with a pH‐dependent oligomerization. The C‐terminally truncated VDE did not show such an oligomerization, was relatively more active at higher pH but did not alter the KM for ascorbate. Circular dichroism measurements revealed the presence of α‐helical structure in both the N‐ and C‐terminal domains. By measuring the initial formation of the product, VDE was found to convert a large number of violaxanthin molecules to antheraxanthin before producing any zeaxanthin, favoring a model where violaxanthin is bound non‐symmetrically in VDE. 相似文献
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The in vitro and in vivo specificity of the family of peptide:N-acetylgalactosaminyltransferases (GalNAcT) is analyzed on the basis of the reactivity and/or inhibitory activity of peptides and protein segments. The transferases appear to be multi-substrate enzymes with extended active sites containing a least nine subsites that interact cooperatively with a linear segment of at least nine amino acid residues on the acceptor polypeptide. Functional acceptor sites are located on the surface of the protein and extended conformations (-strand conformation) are preferred. The acceptor specificity of GalNAc-T can be predicted from the primary structure of the acceptor peptide with an accuracy of 70 to 80%. The same GalNAc-T enzymes catalyze the glycosylation of both serine and threonine residues. The higher in vitro catalytic efficiency toward threonine versus serine is the result of enhanced binding as well as increased reaction velocity, both effects being the result of steric interactions between the active site of the enzyme and the methyl group of threonine. Results from substrate binding studies suggest that GalNAc-T catalyzed transfer proceeds via an ordered sequential mechanism. 相似文献
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Significant efforts have been made to determine the correlation structure of common SNPs in the human genome. One method has
been to identify the sets of tagSNPs that capture most of the genetic variation. Here, we evaluate the transferability of
tagSNPs between populations using a population sample of Sami, the indigenous people of Scandinavia. Array-based SNP discovery
in a 4.4 Mb region of 28 phased copies of chromosome 21 uncovered 5,132 segregating sites, 3,188 of which had a minimum minor
allele frequency (mMAF) of 0.1. Due to the population structure and consequently high LD, the number of tagSNPs needed to
capture all SNP variation in Sami is much lower than that for the HapMap populations. TagSNPs identified from the HapMap data
perform only slightly better in the Sami than choosing tagSNPs at random from the same set of common SNPs. Surprisingly, tagSNPs
defined from the HapMap data did not perform better than selecting the same number of SNPs at random from all SNPs discovered
in Sami. Nearly half (46%) of the Sami SNPs with a mMAF of 0.1 are not present in the HapMap dataset. Among sites overlapping
between Sami and HapMap populations, 18% are not tagged by the European American (CEU) HapMap tagSNPs, while 43% of the SNPs
that are unique to Sami are not tagged by the CEU tagSNPs. These results point to serious limitations in the transferability
of common tagSNPs to capture random sequence variation, even between closely related populations, such as CEU and Sami.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
999.
Åsa Lankinen Sofia Hydbom Maria Strandh 《Evolution; international journal of organic evolution》2017,71(10):2359-2369
Although sexual selection and sexual conflict are important evolutionary forces in animals, their significance in plants is uncertain. In hermaphroditic organisms, such as many plants, sexual conflict may occur both between mating partners (interlocus conflict) and between male and female sex roles within an individual (intralocus conflict). We performed experimental evolution, involving lines that were crossed with either one or two pollen donors (monogamous or polyandrous lines), in the hermaphroditic plant (Collinsia heterophylla) where early fertilizations are associated with female fitness costs (reduced seed set). Artificial polyandry for four generations resulted in enhanced pollen performance and increased female fitness costs compared to the monogamous and source (starting material) lines. Female fitness was also reduced in the monogamous line, indicating a possible trade‐off between sex roles, resulting from early pollination. We performed a second experiment to investigate a potential harming effect of pollen performance on seed set. We found that high siring success of early arriving pollen competing with later‐arriving pollen was associated with high female fitness costs, consistent with an interlocus sexual conflict. Our study provides evidence for the importance of sexual selection in shaping evolution of plant reproductive strategies, but also pinpoints the complexity of sexual conflict in hermaphroditic species. 相似文献
1000.
应用一步PCR法检测并鉴定马疱疹病毒1型和4型 总被引:1,自引:0,他引:1
聚合酶链反应(PCR)可作为一种快速检测并鉴别马疱疹病毒1型(EHV-1)和马疱疹病毒4型(EHV-4)的诊断方法。PCR引物是根据编码EHV-1和EHV-4的糖蛋白B( gB)基因上的共有的核苷酸序列或型特有的核苷酸序列设计的。利用这两种病毒的型特异性混合引物,在一步PCR反应中检测并鉴别EHV-1和EHV-4,而同一疱疹病毒科的单纯疱疹病毒1型(HSV-1)、伪狂犬病毒(PRV)、马立克氏病病毒(MDV)均无特异性扩增。应用建立的PCR方法检测了普氏野马流产胎儿病科,实验结果表明,这种PCR方法是一种直接检测并鉴定EHV-1和EHV-4的快速、敏感的诊断方法,同时,它可在一步PCR反应中直接鉴别这两种病毒,可用于病料中EHV-1和EHV-4检测的初步筛选。 相似文献