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991.
The biogeography of naturalization in alien plants 总被引:9,自引:0,他引:9
Aim This paper reviews the main geographical determinants of naturalization in plants.
Location Global.
Methods Comparative studies of large data sets of alien floras are the main source of information on global patterns of naturalization.
Results Temperate mainland regions are more invaded than tropical mainland regions but there seems to be no difference in invasibility of temperate and tropical islands. Islands are more invaded than the mainland. The number of naturalized species in temperate regions decreases with latitude and their geographical ranges increase with latitude. The number of naturalized species on islands increases with temperature. Naturalized species contribute to floristic homogenization, but the phenomenon is scale-dependent.
Main conclusions Some robust patterns are evident from currently available data, but further research is needed on several aspects to advance our understanding of the biogeography of naturalization of alien plants. For example, measures of propagule pressure are needed to determine the invasibility of communities/ecosystems/regions. The patterns discussed in this paper are derived largely from numbers and proportions of naturalized species, and little is known about the proportion of introduced species that become naturalized. Further insights on naturalization rates, i.e. the proportion of aliens that successfully naturalize within regions, and on geographical and other determinants of its variation would provide us with better understanding of the invasion process. Comparative studies, and resulting generalizations, are almost exclusively based on numbers of species, but alien species differ in their impact on native biodiversity and ecosystem processes. 相似文献
Location Global.
Methods Comparative studies of large data sets of alien floras are the main source of information on global patterns of naturalization.
Results Temperate mainland regions are more invaded than tropical mainland regions but there seems to be no difference in invasibility of temperate and tropical islands. Islands are more invaded than the mainland. The number of naturalized species in temperate regions decreases with latitude and their geographical ranges increase with latitude. The number of naturalized species on islands increases with temperature. Naturalized species contribute to floristic homogenization, but the phenomenon is scale-dependent.
Main conclusions Some robust patterns are evident from currently available data, but further research is needed on several aspects to advance our understanding of the biogeography of naturalization of alien plants. For example, measures of propagule pressure are needed to determine the invasibility of communities/ecosystems/regions. The patterns discussed in this paper are derived largely from numbers and proportions of naturalized species, and little is known about the proportion of introduced species that become naturalized. Further insights on naturalization rates, i.e. the proportion of aliens that successfully naturalize within regions, and on geographical and other determinants of its variation would provide us with better understanding of the invasion process. Comparative studies, and resulting generalizations, are almost exclusively based on numbers of species, but alien species differ in their impact on native biodiversity and ecosystem processes. 相似文献
992.
Tradeoffs and thresholds in the effects of nitrogen addition on biodiversity and ecosystem functioning: evidence from inner Mongolia Grasslands 总被引:19,自引:0,他引:19
YONGFEI BAI JIANGUO WU † CHRISTOPHER M. CLARK† SHAHID NAEEM‡ QINGMIN PAN JIANHUI HUANG LIXIA ZHANG XINGGUO HAN 《Global Change Biology》2010,16(1):358-372
Nitrogen (N) deposition is widely considered an environmental problem that leads to biodiversity loss and reduced ecosystem resilience; but, N fertilization has also been used as a management tool for enhancing primary production and ground cover, thereby promoting the restoration of degraded lands. However, empirical evaluation of these contrasting impacts is lacking. We tested the dual effects of N enrichment on biodiversity and ecosystem functioning at different organizational levels (i.e., plant species, functional groups, and community) by adding N at 0, 1.75, 5.25, 10.5, 17.5, and 28.0 g N m?2 yr?1 for four years in two contrasting field sites in Inner Mongolia: an undisturbed mature grassland and a nearby degraded grassland of the same type. N addition had both quantitatively and qualitatively different effects on the two communities. In the mature community, N addition led to a large reduction in species richness, accompanied by increased dominance of early successional annuals and loss of perennial grasses and forbs at all N input rates. In the degraded community, however, N addition increased the productivity and dominance of perennial rhizomatous grasses, with only a slight reduction in species richness and no significant change in annual abundance. The mature grassland was much more sensitive to N‐induced changes in community structure, likely as a result of higher soil moisture accentuating limitation by N alone. Our findings suggest that the critical threshold for N‐induced species loss to mature Eurasian grasslands is below 1.75 g N m?2 yr?1, and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5 g N m?2 yr?1. This work highlights the tradeoffs that exist in assessing the total impact of N deposition on ecosystem function. 相似文献
993.
994.
Conserving biodiversity under climate change: the rear edge matters 总被引:10,自引:0,他引:10
Modern climate change is producing poleward range shifts of numerous taxa, communities and ecosystems worldwide. The response of species to changing environments is likely to be determined largely by population responses at range margins. In contrast to the expanding edge, the low-latitude limit (rear edge) of species ranges remains understudied, and the critical importance of rear edge populations as long-term stores of species' genetic diversity and foci of speciation has been little acknowledged. We review recent findings from the fossil record, phylogeography and ecology to illustrate that rear edge populations are often disproportionately important for the survival and evolution of biota. Their ecological features, dynamics and conservation requirements differ from those of populations in other parts of the range, and some commonly recommended conservation practices might therefore be of little use or even counterproductive for rear edge populations. 相似文献
995.
小麦体细胞再生株(R1)的染色体变异分析 总被引:5,自引:0,他引:5
吴鹤鸣 《Acta Botanica Sinica》1992,34(3):226-232
本文研究了普通小麦(Triticum aestivum)、“宁麦三号”等5个基因型的体细胞再生株(R_1)减数分裂各期的染色体异常行为。结果表明:再生株 R_1代有丝分裂时表现为染色体数量上的变异,最常见的有2n-2类型,其次是2n-1类型,也有少数为2n 1和2n-4等变异类型;再生株 R_1花粉母细胞减数分裂过程中出现单价体、多价体、染色体桥、落后染色体、断片和微核等异常现象,并与各基因型细胞遗传程度上差异有关。 相似文献
996.
Evidence for divergence of response in Indica,Japonica, and wild rice to high CO2 × temperature interaction 下载免费PDF全文
Diane R. Wang James A. Bunce Martha B. Tomecek David Gealy Anna McClung Susan R. McCouch Lewis H. Ziska 《Global Change Biology》2016,22(7):2620-2632
High CO2 and high temperature have an antagonistic interaction effect on rice yield potential and present a unique challenge to adapting rice to projected future climates. Understanding how the differences in response to these two abiotic variables are partitioned across rice germplasm accessions may be key to identifying potentially useful sources of resilient alleles for adapting rice to climate change. In this study, we evaluated eleven globally diverse rice accessions under controlled conditions at two carbon dioxide concentrations (400 and 600 ppm) and four temperature environments (29 °C day/21 °C night; 29 °C day/21 °C night with additional heat stress at anthesis; 34 °C day/26 °C night; and 34 °C day/26 °C night with additional heat stress at anthesis) for a suite of traits including five yield components, five growth characteristics, one phenological trait, and four photosynthesis‐related measurements. Multivariate analyses of mean trait data from these eight treatments divide our rice panel into two primary groups consistent with the genetic classification of INDICA/INDICA‐like and JAPONICA populations. Overall, we find that the productivity of plants grown under elevated [CO2] was more sensitive (negative response) to high temperature stress compared with that of plants grown under ambient [CO2] across this diversity panel. We report differential response to CO2 × temperature interaction for INDICA/INDICA‐like and JAPONICA rice accessions and find preliminary evidence for the beneficial introduction of exotic alleles into cultivated rice genomic background. Overall, these results support the idea of using wild or currently unadapted gene pools in rice to enhance breeding efforts to secure future climate change adaptation. 相似文献
997.
Gill JL Matika O Williams JL Worton H Wiener P Bishop SC 《Animal : an international journal of animal bioscience》2010,4(1):1-8
Sensory traits, such as juiciness and tenderness, are known to be important to the consumer and thus will influence their consumption of meat, specifically beef. These traits are difficult to measure and often require the use of taste panels to assess the complex parameters involved in the eating experience. Such panels are potentially a large source of measurement error, which may reduce the effectiveness of breeding programmes based on the data they generate. The aim of this study was to assess the quality of such taste panel-derived sensory traits as well as calculating genetic parameters and residual correlations for these traits along with a further set of traditional carcass quality traits. The study examined a sample of 443 Aberdeen Angus-cross animals collected from 14 breeder-finisher farms throughout Scotland. To assess the quality of the taste panel measurements, three consistency statistics were calculated: (i) panel-member consistency, i.e. the extent to which an individual panel member varied in their scoring for a given trait over the period of the experiment; (ii) repeatability, i.e. the consistency with which an individual panel member was able to score a trait on repeated samples from the same animal; and (iii) reproducibility, i.e. the extent to which taste panel members agreed with each other when scoring a trait. These consistency statistics were moderately high, particularly for panel-member consistency and reproducibility, with values ranging from 0.48 to 0.81 and 0.43 to 0.73 respectively. Estimated heritabilities were low for most of the sensory taste-panel-evaluated traits where the maximum value was 0.16 for overall liking. Residual correlations were high between many of the closely related sensory traits, although few significant correlations were found between the carcass quality data and meat quality traits. 相似文献
998.
Louise Ilum Sørensen Juha Mikola Minna-Maarit Kytöviita Johan Olofsson 《Ecosystems》2009,12(5):830-842
Mammal grazing is composed of three mechanisms—removal of foliar tissue (defoliation), return of nutrients via dung and urine
(fertilization), and trampling. To evaluate the relative role of these mechanisms in the effect of reindeer grazing on soil
biota in northern grasslands, we subjected experimental plots in a sub-arctic alpine meadow to defoliation, fertilization
(using NPK-solution), simulated trampling, and their factorial combinations once a year from 2002 to 2004 and measured the
response of plants and decomposers (including microbes, nematodes, collembolans, and enchytraeids) in 2004. Trampling affected
both plant and decomposer communities: the coverage of the moss Pleurozium schreberi and the sedge Carex vaginata, as well as the abundance of collembolans and enchytraeids were reduced in trampled plots. Trampling and fertilization also
interacted significantly, with fertilization increasing the abundance of bacteria and bacterial-feeding and omnivorous nematodes
in trampled plots only, and trampling decreasing fungal biomass in non-fertilized plots only. Defoliation had no overall effects
on plants or decomposers. Nematode genera were not affected by the experimental treatments, but nematode and plant communities
were significantly associated, and all decomposer biota, except collembolans, were strongly affected by the spatial heterogeneity
of the study site. Our results indicate that trampling may have larger and defoliation and fertilization smaller roles than
anticipated in explaining reindeer grazing effects in sub-arctic grasslands. However, even the effects of trampling seem to
be outweighed by the spatial heterogeneity of decomposer abundances. This suggests that in sub-arctic grasslands spatial variation
in abiotic factors can be a more important factor than grazing in controlling soil biota abundances.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Author contributions LIS was involved in planning of the study, fieldwork, lab work, analysis, and wrote the article with contributions from all
other authors; JM and MMK conceived the study and contributed to the data analyses; MMK further contributed to the field work
and JM refined the final appearance of the text; JO started and was responsible for managing the field experiment, collecting
the plant data and gave advice on statistical analysis. 相似文献
999.
LuJiang Qu Wei Liu FangXi Yang ZhuoCheng Hou JiangXia Zheng GuiYun Xu Ning Yang 《中国科学:生命科学英文版》2009,52(11):1030-1035
In order to elucidate the domestication history of Peking ducks, 190 blood samples from six Chinese indigenous duck breeds were collected with186 individualsgenotyped by 15 microsatellite markers. Both the FST and Nei’s standard genetic distances (Ds) from the microsatellite data indicated high genetic differentiation between Peking duck and other Chinese indigenous breeds. The haplotype network with mtDNA data showed that most of the Peking duck haplotypes were distinctly different from those of other domestic breeds. Although the H01 haplotype was shared by all domesticated duck breeds, Peking ducks displayed 12 specific domestic duck haplotypes, including four similar haplotypes H02, H04, H08 and H22, that formed a single haplogroup (A). Both H02 and H22 haplotypes were also shared by mallard and Peking ducks, indicating that Peking ducks originated from wild mallard ducks. 相似文献
1000.