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131.
Increasing evidences have indicated that humic substances can induce plant growth and productivity by functioning as an environmental
source of auxinic activity. Here we comparatively evaluate the effects of indole-3-acetic acid (IAA) and humic acids (HA)
isolated from two different soils (Inseptsol and Ultisol) and two different organic residues (vermicompost and sewage sludge)
on root development and on activities of plasmalemma and tonoplast H+ pumps from maize roots. The data show that HA isolated from these different sources as well as low IAA concentrations (10−10 and 10−15 M) improve root growth through a markedly proliferation of lateral roots along with a differential activation not only of
the plasmalemma but also of vacuolar H+-ATPases and H+-pyrophosphatase. Further, the vacuolar H+-ATPase had a peak of stimulation in a range from 10−8 to 10−10 M IAA, whereas the H+-pyrophosphatase was sensitive to a much broader range of IAA concentrations from 10−3 to 10−15 M. It is proposed a complementary view of the acid growth mechanism in which a concerted activation of the plasmalemma and
tonoplast H+ pumps plays a key role in the root cell expansion process driven by environment-derived molecules endowed with auxinic activity,
such as that of humic substances. 相似文献
132.
Kawamoto Y Shotake T Nozawa K Kawamoto S Tomari K Kawai S Shirai K Morimitsu Y Takagi N Akaza H Fujii H Hagihara K Aizawa K Akachi S Oi T Hayaishi S 《Primates; journal of primatology》2007,48(1):27-40
We investigated the diversity and phylogeography of mitochondrial DNA (mtDNA) in Japanese macaques (Macaca fuscata), an endemic species in Japan that has the northernmost distribution of any non-human primate species. DNA samples from 135
localities representing the entire range of this species were compared. A total of 53 unique haplotypes were observed for
the 412-bp partial mtDNA control region sequence, with length variation distinguishing the two subspecies. Clustering analyses
suggested two putative major haplogroups, of which one was geographically distributed in eastern Japan and the other in western
Japan. The populations in the east showed lower mtDNA diversity than those in the west. Phylogeographical relationships of
haplotypes depicted with minimum spanning network suggested differences in population structure. Population expansion was
significant for the eastern but not the western population, suggesting establishment of the ancestral population was relatively
long ago in the west and recent in the east. Based on fossil evidence and past climate and vegetation changes, we inferred
that the postulated population expansion may have taken place after the last glacial period (after 15,000 years ago). Mitochondrial
DNA showed contrasting results in both variability and phylogenetic status of local populations to those of previous studies
using protein variations, particularly for populations in the periphery of the range, with special inference on habitat change
during the glacial period in response to cold adaptation.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
133.
This article explores factors that shape population structure in novel environments that have received scant theoretical attention: cities. Urban bird populations exhibit higher densities and lower diversity. Some work suggests this may result from lower predation pressure and more predictable and abundant resources. These factors may lead to populations with few winners and many losers regarding access to food, body condition, and reproductive success. We explore these hypotheses with an individual-energy-based competition model with two phenotypes of differing foraging ability. We show that low frequency resource fluctuations favor strong competitors and vice versa. We show that low predation skews equilibrium populations in favor of weak competitors and vice versa. Increasing the time between resource pulses can thus shift population structure from weak to strong competitor dominance. Given recent evidence for more constant resource input and lower predation in urban areas, the model helps understand observed urban bird population structure. 相似文献
134.
We have studied DNA sequence variation in and around the genes ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups
of India, with a view to investigating the relative roles of demographic history and natural selection in shaping the observed
patterns of variation. The total numbers of single nucleotide polymorphisms (SNPs) detected at the ICAM1 and TNF loci were 29 and 12, respectively. Haplotype and allele frequencies differed significantly across populations. The site frequency
spectra at these loci were significantly different from those expected under neutrality, and showed an excess of intermediate-frequency
variants consistent with balancing selection. However, as expected under balancing selection, there was no significant reduction
of F
ST
values compared to neutral autosomal loci. Mismatch distributions were consistent with population expansion for both loci.
On the other hand, the phylogenetic network among haplotypes for the TNF locus was similar to expectations under population expansion, while that for the ICAM1 was as expected under balancing selection. Nucleotide diversity at the ICAM1 locus was an order of magnitude lower in the promoter region, compared to the introns or exons, but no such difference was
noted for the TNF gene. Thus, we conclude that the pattern of nucleotide variation in these genes has been modulated by both demographic history
and selection. This is not surprising in view of the known allelic associations of several polymorphisms in these genes with
various diseases, both infectious and noninfectious. 相似文献
135.
Grabov A 《Annals of botany》2007,99(6):1035-1041
BACKGROUND AND AIMS: Potassium transporters belonging to the KT/KUP/HAK family are important for various aspects of plant life including mineral nutrition and the regulation of development. Genes encoding these transporters are present in the genomes of all plants, but have not been found in the genomes of Protista or Animalia. The aim of this Botanical Briefing is to analyse the function of KT/KUP/HAK transporters from evolutionary, molecular and physiological perspectives. SCOPE: This Briefing covers the phylogeny and evolution of KT/KUP/HAK transporters, the role of transporters in plant mineral nutrition and potassium homeostasis, and the role of KT/KUP/HAK transporters in plant development. 相似文献
136.
Day length affects the dynamics of leaf expansion and cellular development in Arabidopsis thaliana partially through floral transition timing 总被引:2,自引:0,他引:2
Background and Aims: Plant aerial development is well known to be affected by daylength in terms of the timing and developmental stage of floraltransition. Arabidopsis thaliana is a long dayplant in which the time to flower is delayed by short days andleaf number is increased. The aim of the work presented herewas to determine the effects of different day lengths on individualleaf area expansion. The effect of flower emergence per se onthe regulation of leaf expansion was also tested in this study. Methods: Care was taken to ensure that day length was the only sourceof micro-meteorological variation. The dynamics of individualleaf expansion were analysed in Ler and Col-0 plants grown underfive day lengths in five independent experiments. Responsesat cellular level were analysed in Ler plants grown under variousday lengths and treatments to alter the onset of flowering. Key Results: When the same leaf position was compared, the final leaf areaand both the relative and absolute rates of leaf expansion weredecreased by short days, whereas the duration of leaf expansionwas increased. Epidermal cell number and cell area were alsoaltered by day-length treatments and some of these responsescould be mimicked by manipulating the date of flowering. Conclusions: Both the dynamics and cellular bases of leaf development arealtered by differences in day length even when visible phenotypesare absent. To some extent, cell area and its response to daylength are controlled by whole plant control mechanisms associatedwith the onset of flowering. 相似文献
137.
Susan E. Gresens Kenneth T. Belt Jamie A. Tang Daniel C. Gwinn Patricia A. Banks 《Hydrobiologia》2007,575(1):173-190
In a longitudinal study of two streams whose lower reaches received unattenuated urban stormwater runoff, physical disturbance
by stormflow was less important than the persistant unidentified chemical impacts of urban stormwater in limiting the distribution
of Chironomidae, and Ephemeroptera, Trichoptera and Plecoptera (EPT). A hierarchical spatial analysis showed that chironomid
density did not decrease from rural to urban stream reaches. Instead, the taxonomic composition of chironomid assemblages
was significantly altered in urban versus rural reaches; chironomid assemblages in urban reaches exhibited higher average
pollution tolerance scores. In contrast, the density of EPT was significantly lower in urban reaches. Despite higher values
of stormflow tractive force in urban reaches, streambed stability tended to be greater in urban reaches. Modeling of temporal
variation in chironomid density showed similar patterns in both rural and urban reaches: chironomid density had a unimodal
relationship to rainfall index (RI), with highest densities at intermediate values of RI. Models of EPT density over time
in rural reaches showed no significant relation to RI, and temporal variation in EPT density in urban reaches was not predictable.
The abundance of fine particulate organic matter, including periphyton (FPOM), on cobbles was greater in urban reaches and
showed a much greater degree of temporal variation than in rural reaches. In urban reaches, a negative relation between FPOM
and RI indicated the importance of stormflow abrasion.
Handling editor: K. Martens 相似文献
138.
Modelling radiation fluxes in simple and complex environments—application of the RayMan model 总被引:3,自引:0,他引:3
The most important meteorological parameter affecting the human energy balance during sunny weather conditions is the mean
radiant temperature Tmrt. It considers the uniform temperature of a surrounding surface giving off blackbody radiation, which results in the same
energy gain of a human body given the prevailing radiation fluxes. This energy gain usually varies considerably in open space
conditions. In this paper, the model ‘RayMan’, used for the calculation of short- and long-wave radiation fluxes on the human
body, is presented. The model, which takes complex urban structures into account, is suitable for several applications in
urban areas such as urban planning and street design. The final output of the model is, however, the calculated Tmrt, which is required in the human energy balance model, and thus also for the assessment of the urban bioclimate, with the
use of thermal indices such as predicted mean vote (PMV), physiologically equivalent temperature (PET) and standard effective
temperature (SET*). The model has been developed based on the German VDI-Guidelines 3789, Part II (environmental meteorology,
interactions between atmosphere and surfaces; calculation of short- and long-wave radiation) and VDI-3787 (environmental meteorology,
methods for the human-biometeorological evaluation of climate and air quality for urban and regional planning. Part I: climate).
The validation of the results of the RayMan model agrees with similar results obtained from experimental studies. 相似文献
139.
Trans-Arctic dispersals and population and range expansions during the Pleistocene enhanced opportunities for evolutionary diversification and contributed to the process of speciation within the capelin, a northern marine-fish complex exhibiting a circumpolar distribution. Capelin is composed of four highly divergent and geographically discrete mitochondrial DNA (mtDNA) clades (609 bp; cytochrome b). Two clades occur in the North Atlantic, one associated with Canadian Atlantic waters, including Hudson Bay, and the second distributed from West Greenland to the Barents Sea. Two additional clades occur in the Arctic and northeast Pacific Oceans, representing the most recent divergence within the capelin phylogenetic tree. Judged from mtDNA diversity, capelin populations comprising all clades experienced at least one demographic and spatial reduction-expansion episode during recent Pleistocene glaciations that imprinted their molecular architecture. The large contemporary populations in the northeast Pacific and Arctic Oceans exhibited significant genetic structure whereas no such structure was detected in the equally extensive North Atlantic clades. All clades are characterized by one or two prevalent mtDNA haplotypes distributed over the entire range of the clade. Assuming a Pacific ancestor for capelin, we infer that capelin dispersed on two separate occasions to the North Atlantic. A more recent event resulted in the isolation of eastern Pacific and Arctic clades, with the Arctic clade positioned for a potential third Atlantic invasion, as revealed by the presence of this clade in the Labrador Sea. The Labrador Sea is a potential contact zone for three of the four capelin clades. 相似文献
140.
The connectivity among marine populations is determined by the dispersal capabilities of adults as well as their eggs and larvae. Dispersal distances and directions have a profound effect on gene flow and genetic differentiation within species. Genetic homogeneity over large areas is a common feature of coral reef fishes and can reflect high dispersal capability resulting in high levels of gene flow. If fish larvae return to their parental reef, gene flow would be restricted and genetic differentiation could occur. Larabicus quadrilineatus (Labridae) is considered as an endemic fish species of the Red Sea and Gulf of Aden. The juveniles of this species are cleaner fish that feed on ectoparasites of other fishes. Here, we investigated the genetic population structure and gene flow in L. quadrilineatus among five locations in the Red Sea to infer connectivity among them. To estimate genetic diversity, we analysed 369 bp of 237 mitochondrial DNA control region sequences. Haplotype and nucleotide diversities were higher in the southern than in the northern Red Sea. Analysis of molecular variance (amova) detected the highest significant genetic variation between northern and central/southern populations (Phi(CT) = 0.01; P < 0.001). Migration analysis revealed a several fold higher northward than southward migration, which could be explained by oceanographic conditions and spawning season. Even though the Phi(ST) value of 0.01 is rather low and implies a long larval dispersal distance, estimates based on the isolation-by-distance model show a very low mean larval dispersal distance (0.44-5.1 km) compared to other studies. In order to enable a sustainable ornamental fishery on the fourline wrasse, the results of this study suggest that populations in the northern and southern Red Sea should be managed separately as two different stocks. The rather low larval dispersal distance of about 5 km needs to be considered in the design of marine protected areas to enable connectivity and self-seeding. 相似文献