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951.
952.
The peninsula effect – a decrease in species richness from the base to the tip of a peninsula – has been tested for a diverse range of taxa at continental and regional scales. We investigated the peninsula effect at a local scale by examining bird species occurrence in riparian strips (peninsulas) of native eucalypt forest within a radiata pine plantation in the Tumut region, south-eastern Australia. Peninsulas were elongated but 'blind' extensions of a core area of native eucalypt forest. Birds were surveyed by the area search method, within 1.0-ha quadrats established along peninsulas ( n =14), in October and November 2002. Data were analysed using generalized linear mixed models. A significant decrease in bird species richness from the base towards the tip of the peninsulas was observed. The proportion of large bird species recorded per quadrat showed a significant decrease from the base towards the tip of the peninsulas. This pattern was not observed for small birds. Several species were more abundant at the base of the peninsulas than away from the core area of eucalypt forest. The peninsula effect can occur locally in landscape mosaics. Factors leading to the observed patterns of species occurrence may be distinct from those proposed in investigations of the peninsula effect with a biogeographical (macroscale) context. In our microscale study, foraging incursions of individual birds from the core area of native forest through peninsulas were a major factor giving rise to higher bird species richness in the more basal portions of peninsulas. 相似文献
953.
The fish fauna of the newly inundated Lake Itezhi-tezhi, Zambia was observed between 1980 and 1985. Marked changes in the community structure were identified. The most obvious were a decline in species diversity and a shift in species composition from acommunity with a preponderance of Alesles lateralis (Boulenger) (Characidae), to one dominated by cichlids. These changes were primarily due to members of the families Cyprinidae, Mormyridae and Schilbeidae being unable to adapt to the new environmental conditions, such as spawning and feeding grounds, and their inability to cope with fluctuating water levels in the lake. It was suggested that a sound fishery data collection system be implemented to provide reliable information on which to base management policy. 相似文献
954.
Abstract: The impacts of four pesticides used for control of citrus thrips, Scirtothrips citri (Moulton), were evaluated in both field and laboratory populations of a predaceous mite, Euseius tularensis Congdon. Abamectin and chlorfenapyr had the least impact of pesticides evaluated on a field population of E. tularensis and predaceous mite levels mirrored those observed in the untreated control but at a slightly depressed level. Spinosad reduced predaceous mites somewhat but they recovered to 50% of the level in the untreated control by the end of the trial. Mite populations were low throughout the trial in plots treated with cyfluthrin. As an overall summary statistic, cumulative predator mite-days ranged from 73.6% of the level observed in the untreated control with abamectin to 67.1% with chlorfenapyr, 36.8% with spinosad and 11.7% with cyfluthrin. Three additional field trials confirmed abamectin's minimal impact. In laboratory studies of adult female mite mortality on field-weathered, pesticide-treated leaves, cyfluthrin caused high mortality on day 1 after treatment and all mites that were not killed were driven off leaf discs until day 21. When mites were placed on leaf discs 1 day after treatment with abamectin, spinosad, or chlorfenapyr, 67.5% of the mites died on chlorfenapyr discs. By 7 days after treatment, no material but cyfluthrin showed a significant impact. Implications to citrus integrated pest management are discussed. 相似文献
955.
A. Freese J. Benes R. Bolz O. Cizek M. Dolek A. Geyer P. Gros M. Konvicka A. Liegl & C. Stettmer 《Animal Conservation》2006,9(4):388-397
The knowledge of ecological requirements of declining butterflies of European woodlands remains limited, which hinders conservation management of their localities. This also applies for continentally threatened scarce fritillary Euphydryas maturna . On the basis of the largest data set on its habitat use ever collected in Central Europe, we analyse habitat requirements of its populations in Austria (A), the Czech Republic (Cz) and Germany (D). All studied populations inhabit open-canopy sites within woodlands, but larval survival decreases under full sun and preferred sites are relatively humid and sheltered. Nests of pre-hibernation larvae occur at terminal branches of Fraxinus excelsior , 1.5–3 m above the ground. Pre-hibernation mortality reaches 70% (Cz, D). Another limiting factor is quality of woodland vegetation: post-hibernation larvae consume a wide range of herbs and shrubs, and adult distribution is linked to nectar availability. The butterfly thus depends on highly heterogeneous early successional stages of deciduous woods, historically maintained by coppicing (Cz, D) and forest pasture (A). Restoration of these traditional methods offers the only chance for survival of E. maturna in Central Europe, and the butterfly may become a flagship for other threatened organisms of open-canopy woodlands. 相似文献
956.
957.
Inflorescence apices are suitable explants for the rapid in vitro propagation of Musa spp. However, the diploid and triploid banana cultivars showed different in vitro responses with respect to the hormone combinations
in Murashige and Skoog medium. The diploid cultivar (Sannachenkadali, AA) induced a maximum number of multiple shoots in 8.9 μM
6-benzyl adenine (BA) whereas the triploid cultivar (Red banana, AAA) exhibited maximum multiplication in 22.2 μM 6-benzyl
adenine. MS medium supplemented with 11.4 μM indole acetic acid and 17.8 μM BA was also suitable for shoot proliferation in
triploid cultivar but not in the diploid cultivar. The regenerated shoots were rooted in Murashige and Skoog basal medium
within 10–15 days. The rooted plantlets were transferred to vermiculite and maintained at a temperature of 25 ± 2°C for 10 days
and then at room temperature (30–32°C) for 2 weeks before transferring to potted soil compost mixture. The plantlets showed
100% survival. 相似文献
958.
We describe a protocol for somatic embryogenesis of Protea cynaroides, with potential for high frequency production of this important horticultural species. Somatic embryos formed directly on
both P. cynaroides mature zygotic embryos and excised cotyledons cultured on MS medium without growth regulators. The addition of growth regulators
such as naphthalene acetic acid (NAA) (5; 13 and 27 μM) and 2,4-dichlorophenoxyacetic acid (2,4-D) (5; 11 and 23 μM), in combination
with thidiazuron (TDZ) (1 μM), benzylaminopurine (BAP) (1 μM) or kinetin (1 μM) suppressed the formation of somatic embryos.
After eight weeks in culture, formation of somatic embryos was observed. Zygotic explants formed the most embryos when cultured
in a 12-h photoperiod in comparison to explants cultured in the dark. Up to 83% of these embryos germinated after transferal
to the germination medium containing 0.3 μM GA3. Significantly fewer embryos germinated in MS medium with no growth regulators, or supplemented with higher concentrations
of GA3, while low germination percentages were also observed in MS media containing casein hydrolysate and coconut water. The germination
of normal somatic embryos (two separate cotyledons and a single radicle) was observed only in media containing either no growth
regulators, 0.3 μM GA3 or 1 μM GA3. All embryos that germinated in high concentrations of GA3 were malformed. 相似文献
959.
Esmaeil Ebrahimie Mohammad Reza Naghavi Abdolhadi Hosseinzadeh Mohammad Reza Behamta Manijeh Mohammadi-Dehcheshmeh Ahmad Sarrafi German Spangenberg 《Plant Cell, Tissue and Organ Culture》2007,90(3):293-311
In this study, using cumin embryo as explant and manipulating plant growth regulators (PGRs) in regeneration medium, the main
in vitro morphogenesis pathways including direct shoot organogenesis, direct somatic embryogenesis, indirect somatic embryogenesis,
and indirect shoot organogenesis were obtained. The effects of PGRs, subculture, and light on the induction and progression
of different pathways were studied in detail. Direct shoot organogenesis occurred on the meristematic zone, while direct somatic
embryogenesis was observed on hypocotyl part of cumin embryo (more differentiated part). Application of BAP (0.1 mgl−1) was the sole triggering factor for induction of callus and indirect regeneration pathways. Exogenous IAA played the central
role in the direct somatic embryogenesis pathway; however, the combined effects of IAA and NAA along with the high endogenous
cytokinin level resulted in direct shoot organogenesis. Subculturing revealed accelerating effects on direct somatic embryogenesis
pathway and callus formation. Conversely, subculturing had negative effect on direct shoot organogenesis pathway. In certain
combinations of PGRs, like 0.4 mgl−1 IAA + 0.4 mgl−1 NAA, co-induction and co-regeneration of different pathways were observed. Investigation of genotype dependencies of different
pathways showed that direct pathways are more genotype-dependent, stable, and faster than indirect pathways. This research
presents the embryo of cumin as a convenient model material for induction and comparison of different morphogenesis pathways. 相似文献
960.
Koen Gillis Johan Gielis Hilde Peeters Emmy Dhooghe Jan Oprins 《Plant Cell, Tissue and Organ Culture》2007,91(2):115-123
A reliable protocol for mass propagation via somatic embryogenesis in mature bamboos has been established using pseudospikelets
of Bambusa balcooa. Fourty percent of the explants gave rise to multiple regenerants within 4 months. This conversion rate is sufficiently high
to use the process in commercial mass production. Further, shoot apical meristems can also be used as primary explants without
lost of efficiency.
Regenerated plants were uniform and identical to the mother plant and to plants obtained by axillary branching with respect
to growth characteristics and morphology. Furthermore, epigenetic changes could not be detected by Methylation Sensitive AFLP
(MSAP). During the complete process no changes in ploidy level could be observed.
The process allows for a cost reduction for this tropical bamboo for forestry of up to 57% compared to micropropagation via
axillary branching. For the first time, a reliable process based on somatic embryogenesis has been developed that is well
suited for commercial micropropagation of elite mature bamboos. 相似文献