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81.
82.
A three‐dimensional analysis of startle behaviours of guppies Poecilia reticulata, in dyads or alone, from two populations that show distinct differences in shoaling behaviour was performed. During the first few seconds after a startling stimulus, changes in behaviour, which could be critical if an individual is to survive a predatory attack, and the interactions between pairs of P. reticulata were examined. The enhanced social interactions immediately after the stimulus, as a proxy for shoaling behaviour, and their dissipation were quantified. Social (individuals tested in dyads) v. asocial (tested alone) responses to the startling stimulus were also compared. The three‐dimensional reconstruction, from a two‐camera, high‐frame‐rate tracking system allowed for the tracking of the individuals' speed and speed recovery and, for P. reticulata in dyads, interindividual distance and orientation. For the dyads from the high‐predation population, the closer the individuals were to each other, the more likely they were to be parallel, but no correlation was found for the low‐predation P. reticulata. The startle response of P. reticulata comprised the following sequence: freezing, darting and skittering and recovery to pre‐stimulus swimming behaviour. Upon repeated encounters with the stimulus, a reduced shoaling and startle response was observed, although the rate of reduction was faster in P. reticulata from the high‐predation population than those from the low‐predation population. The results are discussed in light of what is known about the anti‐predator behaviour of this species. 相似文献
83.
Soltész A Tímár I Vashegyi I Tóth B Kellos T Szalai G Vágújfalvi A Kocsy G Galiba G 《Plant biology (Stuttgart, Germany)》2011,13(5):757-766
Cold acclimation is necessary for winter wheat (Triticum aestivum L.) to achieve its genetically determined maximum freezing tolerance, and cold also fulfils the vernalisation requirement. Chromosome 5A is a major regulator of these traits. The aim of the present study was to discover whether changes in the half‐cell redox potential of the glutathione/glutathione disulphide (GSH/GSSG) and ascorbate/dehydroascorbate (AA/DHA) couples induced by cold acclimation are related to freezing tolerance and vernalisation requirement in a specific genetic system including chromosome 5A substitution lines. The amounts of H2O2 and AA, and the AA/DHA ratio showed a rapid and transient increase in the crown of all genotypes during the first week of acclimation, followed by a gradual increase during the subsequent 2 weeks. The amount of GSH and its ratio compared to GSSG quickly decreased during the first day, while later these parameters showed a continuous slow increase. The H2O2, AA and GSH concentrations, AA/DHA and GSH/GSSG ratios and the half‐cell reduction potential of the GSH/GSSG couple were correlated with the level of freezing tolerance after 22 days at 2 °C; hence these parameters may have an important role in the acclimation process. In contrast to H2O2 and the non‐enzymatic antioxidants, the lipid peroxide concentration and activity of the four antioxidant enzymes exhibited a transient increase during the first week, with no significant difference between genotypes. None of the parameters studied showed any relationship with the vegetative/generative transition state monitored as apex morphology and vernalisation gene expression. 相似文献
84.
Peggy?L.?Edds-WaltonEmail author Richard?R.?Fay 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2005,191(12):1079-1086
Our previous studies have shown that the peripheral auditory system of the toadfish encodes the direction of a sound source.
Here, we compare directional responses of peripheral saccular afferents, cells in the descending octaval nucleus (DON) of
the medulla, and the torus semicircularis (TS) of the midbrain. Recording locations in the brain were labeled with neurobiotin
to confirm the site. To compare directional responses among cells, we calculated an index [sharpening ratio (SR)] that weights
the relative strength of responses to the best direction for that cell and to the adjacent stimulus angles tested. Unsharpened
saccular afferents tend to have a cosinusoidal directional response pattern (DRP) with an expected SR of 0.87. In DON, more
than 60% of the cells exhibited directional sharpening (defined as SR <0.8). In TS, more than 80% of the cells exhibited directional
sharpening. We conclude that directional auditory sharpening first occurs in DON and some additional sharpening occurs in
the ascending pathway to the midbrain, particularly in azimuth. The sharpening of directional selectivity is likely to be
an important component of the neural computations underlying directional hearing. 相似文献
85.
In this study a combination of cytoenzymological and immunocytochemical techniques was used in order to demonstrate the presence of cyclic nucleotide metabolism in chloroplasts of higher plants. Catalytic cytochemistry was used to localize adenylyl cyclase activity by means of electron microscope investigation on Nicotiana tabacum cv. Petit Havana leaf fragments. Various immunocytochemical techniques were explored to visualize the presence of the second messenger adenosine 3':5'-cyclic monophosphate. Making use of adenylyl imidodiphosphate as a substrate, the enzyme activity was predominantly located at the intermembrane space of the chloroplast envelope. In order to provide further topographical information, intact, isolated chloroplasts were submitted to the same cytoenzymological procedure and revealed stromal adenylyl cyclase activity. Using high-pressure freezing as a physical fixative to obtain an instantaneous metabolic arrest the cellular vitrified water phase was sublimed under ultra-high vacuum by means of molecular distillation drying, avoiding recrystallization and hence redistribution of small highly diffusible molecules. This sequential combination preserved 3':5'-cAMP epitope retention in chloroplasts as was demonstrated by immunogold labelling. These results further substantiate in a unique way the growing evidence of the presence of an organelle-specific cAMP metabolism in higher plants. Furthermore the data presented support the status of chloroplasts as an excellent model to further investigate cAMP metabolism and to correlate it with a variety of physiological functions. 相似文献
86.
Zh.?I?SimovEmail author G.?Y.?Ivanov 《World journal of microbiology & biotechnology》2005,21(3):345-350
Summary The changes in the number of the starter microorganisms Lb. delbrueckii subsp. bulgaricus and Str. thermophiluswere followed in frozen-stored Kashkaval cheese made from cow’s milk. Kashkaval samples of various aging times were produced industrially, frozen at T=−16 °C and stored at T=−10 to −12 °C for 12 months. It was found that the number of Lb. delbrueckiisubsp. bulgaricus and Str. thermophilusdecreased considerably during frozen storage. The decrease was more substantial for Lb. delbrueckiisubsp. bulgaricus, which was evidence for its greater sensitivity to the impact of low temperatures. The aging time of Kashkaval did not influence the changes in the starter culture during frozen storage but is important for its amount in the product aged after defrosting. There was an increase in the Str. thermophilus: Lb. delbrueckiisubsp. bulgaricus ratio in samples with shorter aging time subjected to frozen storage and aged after defrosting. The changes in the starter culture in frozen stored Kashkaval cheese can be controlled by an appropriate combination of the two factors: aging time and period of frozen storage. 相似文献
87.
Parker-Thornburg JV Alana JL Smith CN Detry M Rojas ML Baskin KK 《Transgenic research》2005,14(5):685-690
The production of chimeric mice is a complex process, requiring the careful coordination of tissue culture cell growth, production
of a large number (30–75) of competent blastocysts and the availability of appropriately timed pseudo pregnant female mice.
Failure at any of these steps can impinge upon the rapid production of chimeras. One potential improvement for the efficient
generation of chimeric mice would be the utilization of cryopreserved embryos suitable for injection. C57Bl/6 morulae were
frozen using a standard 2-step protocol with ethylene glycol as the cryopreservation agent. We determined that cryopreserved
morulae could thaw, culture to blastocyst stage in KSOM media and survive injection at rates equivalent to control embryos.
Cryopreserved morulae were also equivalent to controls at all later stages in the process of production of chimeric mice,
including birth rate, percentage chimerism of resulting animals and ability to produce germline progeny. Hence, cryopreservation
of morulae for blastocyst injection is a suitable option to enhance the efficiency of chimeric mouse generation. 相似文献
88.
89.
Numerical simulation of selective freezing of target biological tissues following injection of solutions with specific thermal properties 总被引:3,自引:0,他引:3
Recently, we proposed a method for controlling the extent of freezing during cryosurgery by percutaneously injecting some solutions with particular thermal properties into the target tissues. In order to better understand the mechanism of the enhancement of freezing by these injections, a new numerical algorithm was developed to simulate the corresponding heat transfer process that is involved. The three-dimensional phase change processes in biological tissues subjected to cryoprobe freezing, with or without injection, were compared numerically. Two specific cases were investigated to illustrate the selective freezing method: the injection of solutions with high thermal conductivity; the injection of solutions with low latent heat. It was found that the localized injection of such solutions could significantly enhance the freezing effect and decrease the lowest temperature in the target tissues. The result also suggests that the injection of these solutions may be a feasible and flexible way to control the size of the ice ball and its direction of growth during cryosurgery, which will help to optimize the treatment process. 相似文献
90.