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71.
Qingrong Sun Hongyan Sun Richard L. Bell Huifeng Li Li Xin 《Plant Cell, Tissue and Organ Culture》2011,107(1):131-140
A wide range of phenotypic variation was observed among neopolyploids obtained from the diploid pear cultivar ‘Fertility’
by in vitro colchicine treatment. The variant plantlets had alterations in leaf characteristics. Neopolyploids had significantly
different ratios of leaf length to leaf width compared to the diploid control. Shoot regeneration from leaf explants and rooting
ability from in vitro shoots of neopolyploids was examined. Regeneration frequencies of shoots from leaf explants of seven
of the nine neopolyploids were significantly decreased compared to the diploid control. The organogenic potential of neopolyploids
was highly genotype-dependent for both shoots and roots. Tetraploid clone 4x − 4 failed to regenerate shoots from leaf explants
and the pentaploid clone 5x − 2 failed to root from in vitro shoots. The results suggest that polyploidization caused the
decrease in or loss of in vitro organogenic potential. Regenerated shoots derived from neopolyploids showed different phenotypes,
depending on the ploidy of the donor plant. 相似文献
72.
Feed grain production for on-farm use is widespread in Bavarian agriculture and garants a reliable production of healthy foodstuff. Therefore the quality of feed grain is very important for farmers. In an orientating investigation of the on-farm stored feed grain quality from the harvest years 1991 to 2000 1757 samples were analysed. Based on values for guidance by the German government for DON and ZEA and Commission Regulation EC No 472/2002 for OTA the results show that only 2% of the positive samples have amounts higher then 0,05 mg ZEA/kg grain, 4% of the positive samples contain more then 1 mg DON/kg grain and 2% of the positive samples have amounts higher then 0,003 mg OTA/kg feed grain. These illustrate the good conservation and storage quality on Bavarian farms. 相似文献
73.
Inward rectifying potassium (KIR) currents in medium spiny (MS) neurons of nucleus accumbens inactivate significantly in ~40% of the neurons but not in the
rest, which may lead to differences in input processing by these two groups. Using a 189-compartment computational model of
the MS neuron, we investigate the influence of this property using injected current as well as spatiotemporally distributed
synaptic inputs. Our study demonstrates that KIR current inactivation facilitates depolarization, firing frequency and firing onset in these neurons. These effects may be
attributed to the higher input resistance of the cell as well as a more depolarized resting/down-state potential induced by
the inactivation of this current. In view of the reports that dendritic intracellular calcium levels depend closely on burst
strength and spike onset time, our findings suggest that inactivation of KIR currents may offer a means of modulating both excitability and synaptic plasticity in MS neurons. 相似文献
74.
75.
76.
Food availability is important to the dynamics of animal social organizations or populations. However, the role of winter
food availability in animal population dynamics is still controversial. We carried out an experimental study to test Lack’s
hypothesis that reduced food in winter limits survival and spring numbers of breeding individuals of social groups, using
the Mongolian gerbil (Meriones unguiculatus) as model species. We established 24 gerbil social groups in 24, 10 × 10 m, pens in September 2008. We provided wheat seeds
as supplemental food in 12 enclosures from September 2008 to March 2009; the other 12 enclosures, not provided with supplemental
food, served as controls. We live-trapped gerbils at a 2-week interval from September to April. Supplemental food during winter
increased biweekly survival by 10% relative to that in control groups. Only four control social groups survived to the end
of our study whereas all 12 food-supplemented social groups survived through our study period. Supplemental food also increased
cumulative numbers of recruits and group sizes of gerbils. We conclude that winter food availability limits winter survival
and spring social groups or population sizes of Mongolian gerbils. 相似文献
77.
Plant gene responses to frequency-specific sound signals 总被引:1,自引:0,他引:1
Mi-Jeong Jeong Chang-Ki Shim Jin-Ohk Lee Hawk-Bin Kwon Yang-Han Kim Seong-Kon Lee Myeong-Ok Byun Soo-Chul Park 《Molecular breeding : new strategies in plant improvement》2008,21(2):217-226
We identified a set of sound-responsive genes in plants using a sound-treated subtractive library and demonstrated sound regulation
through mRNA expression analyses. Under both light and dark conditions, sound up-regulated expression of rbcS and ald. These are also light-responsive genes and these results suggest that sound could represent an alternative to light as a
gene regulator. Ald mRNA expression increased significantly with treatment at 125 and 250 Hz, whereas levels decreased significantly with treatment
at 50 Hz, indicating a frequency-specific response. To investigate whether the ald promoter responds to sound, we generated transgenic rice plants harboring a chimeric gene comprising a fusion of the ald promoter and GUS reporter. In three independent transgenic lines treated with 50 or 250 Hz for 4 h, GUS mRNA expression was up-regulated at 250 Hz, but down-regulated at 50 Hz. Thus, the sound-responsive mRNA expression pattern
observed for the ald promoter correlated closely with that of ald, suggesting that the 1,506 bp ald promoter is sound-responsive. Therefore, we propose that in transgenic plants, specific frequencies of sound treatment could
be used to regulate the expression of any gene fused to the ald promoter. 相似文献
78.
In the Okavango Delta 98–99% of the water from inflow and rainfall is lost to the atmosphere through evapotranspiration. As
a consequence 94% of inflowing solutes are retained within the Delta landscape. This process might be expected to result in
an entirely saline environment, but that is not the case: the surface waters have very low salinity, supporting a typical
freshwater biota. It has been deduced that the numerous islands in the Delta (about 150,000 within an area of 13,500 km2) have been formed through evapotransporative concentration in the groundwater, of infiltrating solutes, followed by precipitation
and volume increase. Evidence of this is the large amount of calcrete in island soils. These islands of 3–10 m thickness with
clayey soils are underlain by fine Kalahari sand to a depth of 200–300 m, which also indicates that they are formed through
surface processes. The infiltration rate of surface water from floodplains and streams into islands is very high, and is predominantly
a lateral process that is unidirectional. Evapotranspiration in the riparian woodland zone cause the ground-waters in the
central area of islands—with halophyte grasslands—to have very high salinities. By use of chloride as a conservative element
the concentration factor between central island groundwater and surface water is calculated to be 500–1,000. This groundwater
is depleted of calcium and magnesium supporting the early deductions that these elements have precipitated as calcrete. There
is also a large depletion of silicate and potassium that probably have precipitated as well forming the clayey soils typical
of the islands. The central island groundwater is dominated by sodium, bicarbonate and dissolved organic matter. The gradual
increase of salinity here causes a periodic let off of this water through a density-driven process to deeper layers. This
process together with island growth through precipitation of solutes are the two major sink processes of inflowing solutes
and explains why the Okavango Delta is at present a freshwater system. The whole island complex is calculated to be 100,000–400,000 years
old while some intensely studied islands may be younger: 80,000–240,000 years. The discrepancy is explained by a biassed selection
of islands currently in flooded areas with better growth conditions. The uniqueness of the Okavango Delta and ideas for future
research are discussed. 相似文献
79.
We determined the incidence of curculionid beetles of the genus Lonchophorus on aborted and not aborted flower buds and developing fruits of the tree Ceiba pentandra in southeastern Costa Rica. Beetle larvae were found in reproductive parts of all trees sampled trees. The frequency of beetle
larvae was greater in aborted buds and immature fruits. A positive correlation between larvae development and flower bud development
indicates that female oviposition occurred in an early flower developmental stage and time until bud abortion is variable.
Weevil herbivory could be considered as one of the main factors that cause flower bud and fruit abortion in C. pentandra.
Resumen Determinamos la incidencia de curculiónidos del género Lonchophorus en botones florales y frutos inmaduros tanto abortados como no abortados en el árbol Ceiba pentandra en el SE de Costa Rica. Las larvas de curculiónidos fueron encontradas en todos los árboles muestreados. La frecuencia de larvas fue mayor en botones y frutos abortados. Una correlación positiva entre el desarrollo larval y el desarrollo del botón indica que la oviposición ocurre en una fase temprana de este y que el tiempo hasta el aborto es variable. La herbivoría por larvas de curculiónidos puede ser uno de los factores más importantes en el aborto de botones y frutos inmaduros en C. pentandra.相似文献
80.
Modelling biological invasions over homogeneous and inhomogeneous landscapes using level set methods
The establishment, spread and subsequent degradation of existing environments by invasive species is a worldwide problem affecting
native and agricultural ecosystems. The phenomenal cost to governments as a result of research and eradication or control
drives the need to understand invasion characteristics. In this paper we develop a method for modelling the boundary of an
invasion over time with model inputs being the initial distribution of the invasion and the speed at which the invasion front
moves over time. This speed function can depend on the topography of the ground cover and we consider examples of homogeneous
and inhomogeneous spread. The possibility of a long-distance dispersal event occurring is also considered. In particular,
examples of the spread of emergent weeds and weeds which favour creeks and river beds in New Zealand are presented. 相似文献