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121.
The indole-3-pyruvate decarboxylase gene (ipdC), coding for a key enzyme of the indole-3-pyruvic acid pathway of IAA biosynthesis in Azospirillum brasilense SM was functionally disrupted in a site-specific manner. This disruption was brought about by group II intron-based Targetron
gene knock-out system as other conventional methods were unsuccessful in generating an IAA-attenuated mutant. Intron insertion
was targeted to position 568 on the sense strand of ipdC, resulting in the knock-out strain, SMIT568s10 which showed a significant (∼50%) decrease in the levels of indole-3-acetic
acid, indole-3-acetaldehyde and tryptophol compared to the wild type strain SM. In addition, a significant decrease in indole-3-pyruvate
decarboxylase enzyme activity by ∼50% was identified confirming a functional knock-out. Consequently, a reduction in the plant
growth promoting response of strain SMIT568s10 was observed in terms of root length and lateral root proliferation as well
as the total dry weight of the treated plants. Residual indole-3-pyruvate decarboxylase enzyme activity, and indole-3-acetic
acid, tryptophol and indole-3-acetaldehyde formed along with the plant growth promoting response by strain SMIT568s10 in comparison
with an untreated set suggest the presence of more than one copy of ipdC in the A. brasilense SM genome. 相似文献
122.
H. J. Barclay 《Population Ecology》2001,43(3):197-206
Models were constructed for control of a pest species by the release of sterile insects and these models explored the consequences
of incomplete sterility. This feature was then coupled with the lack of competitive ability of released insects, the immigration
of insects from outside the control area, and the mode of population regulation (density independent vs. density dependent).
Using the density-independent models, it was seen that the limits on residual fertility of treated insects become much more
stringent when incomplete sterilization is combined with a lack of competitive ability and immigration of insects into the
control area. Strong density dependence in the system has a marked moderating effect on the requirements for sterility, competitive
ability, and immigration. However, if the density-independent limits on these factors are exceeded, then suppression is possible,
but collapse of the pest population is impossible using sterile releases alone. Even suppression might not be satisfactory
if these three detrimental factors are prominent. It is suggested that one remedy is the use of the sterile release method
in combination with other control methods.
Received: January 18, 2001 / Accepted: August 7, 2001 相似文献
123.
端粒酶反义cDNA对乳腺癌细胞损伤修复能力的影响 总被引:3,自引:0,他引:3
利用反义核酸技术将端粒酶RNA的全长cDNA反向导入乳腺癌MCF 7细胞基因组中 .通过单细胞凝胶电泳实验发现 ,其DNA受H2 O2 损伤后的修复能力下降 .但端粒酶活性抑制为何引起其DNA损伤修复能力下降的原因尚待进一步研究 . 相似文献
124.
125.
Apparent decoupling of prey recognition ability with prey availability in an insular snake population 总被引:2,自引:0,他引:2
Numerous studies on the feeding behavior of snakes have reported the consistency of tongue-flick responses with their natural
diets. For representatives of widely distributed, dietary generalist species from particular localities, we can expect that
their tongue-flick responses to potential prey unavailable in their original habitats have been reduced whereas those to prey
common in the habitats have been enhanced. To test this hypothesis, intraspecific variation in tongue-flick responses to prey
chemicals was examined using ingestively naive snakes (Elaphe quadrivirgata) from dietarily different populations: populations from the main Japanese island, where the snakes' diet predominantly consists
of sympatric frogs, and from Mikura-jima Island, where no frogs occur and the snakes thus chiefly prey on lizards. We presented
chemical stimuli from six items including those from their natural and potential prey (fish, frog, lizard, mouse, water, and
cologne) to newborn snakes. Significant effects of stimuli on the tongue-flick responses were detected. On the other hand,
effects of population and interaction between stimuli and population were not significant, and individual comparisons revealed
no significant interlocality differences in responses to either frog or lizard chemicals. Thus, our hypothesis was not supported.
However, in the Mikura-jima sample, significantly fewer snakes responded to frog chemicals than in the main island sample.
The significance of the inconsistency between prey recognition ability and prey availability in the Mikura-jima population
are discussed.
Received: October 17, 2000 / Accepted: December 14, 2000 相似文献
126.
甜高粱茎秆糖锤度配合力的测定 总被引:3,自引:0,他引:3
曹文伯 《植物遗传资源学报》2002,3(4):23-27
经测定,本试验各参试甜高梁品种茎秆糖锤度性状的配合力效应及其相对效应值存在显著差别。在亲本不育系中以 Tx625A 为最高(4.44、45.16%);在亲本恢复系中以4035为最高(2.01、20.44%)。由于双亲的交互作用,各组合之特殊配合力相对效应值,以 Tx622A×4034最高,为28.99%,其次是 Tx625A×4008,为19.83%。说明在应用三系选育甜高粱杂交种时,为了获得高锤度的组合,特殊配合力相对效应值高是重要的指标,关键在于亲本的选择及其组配方式。 相似文献
127.
ELISABETE CORREIA HELENA FREITAS 《Botanical journal of the Linnean Society. Linnean Society of London》2002,140(4):383-390
Drosophyllum lusitanicum (L.) Link (Droseraceae), Erva pinheira orvalhada, an endangered carnivorous plant, is a local endemic of clearings in pine, cork oak and oak forests or their successional shrublands in the western Iberian Peninsula and Morocco. The conservation status, distribution and population dynamics of this species are only partially known, both for Spanish and Portuguese occurrences. Portuguese distribution data from herbarium and bibliographic sources were collected for this study. Field work on 50 populations was undertaken in order to improve knowledge on their conservation status and possible threats. Natural causes, infrastructure and housing construction are stressed as the most important threats. Germination tests were carried out and the distribution patterns, plant height and the number of flowers were studied in an arbitrarily chosen population. A relatively high light requirement and low competitive ability to gain light are considered factors likely for the microdistribution pattern. Drosophyllum lusitanicum cannot compete for light in habitats with intense competition. Seeds from D. lusitanicum have reduced probability of germination when adult plants are already growing in the area. It is hypothesized that seed germination shows a similar pattern to flowering, viz over a considerable time rather than in a sudden flush. This strategy may be a key factor for the species' survival, representing attempts to take advantage of available resources, preventing intraspecific competition and, finally, preventing sudden total disappearance of a population, resulting from any catastrophic events due to natural causes or to human activity. As a result of this study, some conservation measures are suggested. © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 383–390. 相似文献
128.
Iwona Żur Andrzej Skoczowski Sebastian Pieńkowski Franciszek Dubert 《Acta Physiologiae Plantarum》2002,24(1):11-17
The uptake rate of 14C-labelled sucrose, myo-inositol and PC was studied in callus cultures of two oilseed rape cultivars, characterized by different in vitro regeneration ability. Transfer of calli onto regeneration stimulating medium resulted in changes of examined substances uptake
rate, which were depended on tissue morphogenic potential. Non-regenerating calli of both cultivars increased uptake rate
of sucrose whereas changes in incorporation of other compounds were under genome control. Significant increase of uptake rate
of all tested compounds was observed as result of organogenesis initiation. Such differences, in the responses of organogenic
and non-organogenic tissue indicate that this parameter could be useful as marker of organogenesis
A correlation was observed between the rate of sucrose uptake and its concentration in the medium, which suggests an advantage
to passive transport through the callus cell membrane. Lack of such correlation in the case of other labels indicates that
this processes are selective and under cell control. 相似文献
129.
Żur Iwona Skoczowski Andrzej Niemczyk Elżbieta Dubert Franciszek 《Acta Physiologiae Plantarum》2002,24(1):3-10
Changes in the membrane lipid and sterols content and composition were studied during induction and differentiation in callus
cultures of Brassica napus var. oleifera. Callus induction was associated with an increase of DGDG content, significant changes in fatty acids composition of all
lipid fractions and increased degree of lipid unsaturation. The membrane lipid composition of tissue at different degrees
of differentiation was found to vary significantly, particularly two weeks after transfer of callus to regeneration medium.
The main differences concerned the content and composition of galactolipids. Curiously in many cases, these differences declined
during subsequent culture, in spite of the morphogenesis process which was in progress. Another result of differentiation
was the change in free sterol composition: in shoot regenerating calli the content of stigmasterol had rose whereas the accumulation
of campesterol decreased. Even though observed changes in membrane properties may not play a role in morphogenesis they are
nevertheless useful as developmental markers and can be invaluable in understanding biochemical basis of morphogenesis. 相似文献
130.
When prey are attacked by predators, escape ability has an obvious
influence on the probability of survival. Laboratory studieshave suggested that flight performance of female birds mightbe affected by egg production. This is the first study of changesin take-off ability, and thus potentially in predation risk,during reproduction in wild birds. We trapped individual maleand female blue tits repeatedly during the breeding season.Females were 14% heavier and flew 20% slower (probably as aconsequence of a lower ratio of flight muscle to body mass)during the egg-laying period than after the eggs had hatched.However, flight muscle size did not change to compensate for
changes in body mass over this period. In contrast, males showedno changes in either body mass, muscle size, or flight abilityover the same period. Furthermore, the impairment of flightin females increased with the proportion of the clutch thathad been laid, an effect that was independent of body mass
and muscle size. This indicates that egg production causes additional
physiological changes in the female body that produce impairedlocomotor performance. We suggest that courtship feeding offemale blue tits by their mates might reduce predation riskduring the period when female take-off ability is impairedby reducing the time females have to spend foraging and thusreducing the time they are exposed to increased predation. 相似文献