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131.
Neural oscillation is one of the most extensively investigated topics of artificial neural networks. Scientific approaches
to the functionalities of both natural and artificial intelligences are strongly related to mechanisms underlying oscillatory
activities. This paper concerns itself with the assumption of the existence of central pattern generators (CPGs), which are the plausible neural architectures with oscillatory capabilities, and presents a discrete and generalized
approach to the functionality of locomotor CPGs of legged animals. Based on scheduling by multiple edge reversal (SMER), a primitive and deterministic distributed algorithm, it is shown how oscillatory building block (OBB) modules can be created and, hence, how OBB-based networks can be formulated as asymmetric Hopfield-like neural networks
for the generation of complex coordinated rhythmic patterns observed among pairs of biological motor neurons working during
different gait patterns. It is also shown that the resulting Hopfield-like network possesses the property of reproducing the
whole spectrum of different gaits intrinsic to the target locomotor CPGs. Although the new approach is not restricted to the
understanding of the neurolocomotor system of any particular animal, hexapodal and quadrupedal gait patterns are chosen as
illustrations given the wide interest expressed by the ongoing research in the area.
Received: 14 June 2002 / Accepted: 18 February 2003 /
Published online: 20 May 2003
Correspondence to: Z. Yang (e-mail: zhijun.yang@ed.ac.uk)
Acknowledgements. This work was partially supported by CNPq, the Brazilian Research Agency, under support number 143032/96-8. We are grateful
for the helpful discussions with Prof. V.C. Barbosa, Dr. A.E. Xavier, Dr. M.S. Dutra, and Dr. A.F.R. Araújo. The donations
of FPGA hardware and software from XILINX Incorporation under the order No. XUP2930 and XUP3576 are also highly appreciated. 相似文献
132.
Nieh JC Contrera FA Nogueira-Neto P 《Proceedings. Biological sciences / The Royal Society》2003,270(1529):2191-2196
Research on bee communication has focused on the ability of the highly social bees, stingless bees (Hymenoptera, Apidae, Meliponini) and honeybees (Apidae, Apini), to communicate food location to nest-mates. Honeybees can communicate food location through the famous waggle dance. Stingless bees are closely related to honeybees and communicate food location through a variety of different mechanisms, many of which are poorly understood. We show that a stingless bee, Trigona hyalinata, uses a pulsed mass-recruitment system that is highly focused in time and space. Foragers produced an ephemeral, polarized, odour trail consisting of mandibular gland secretions. Surprisingly, the odour trail extended only a short distance away from the food source, instead of providing a complete trail between the nest and the food source (as has been described for other stingless bees). This abbreviated trail may represent an intermediate strategy between full-trail marking, found in some stingless bees, and odour marking of the food alone, found in stingless bees and honeybees. 相似文献
133.
Cell killing by avian leukosis virus subgroup B (ALV-B) in cultures has been extensively studied, but the molecular basis of this process has not been established. Here we show that superinfection, which has been linked to cell killing by ALV-B, plays no crucial role in cell death induction. Instead, we show that signaling by the ALV-B receptor, TVB(S3), a member of the tumor necrosis factor receptor family, is essential for ALV-B-mediated cell death. TVB(S3) activated caspase-dependent apoptosis during ALV-B infection. Strikingly, apoptosis induction occurred predominantly in uninfected cells, while ALV-B-infected cells were protected against cell death. This bystander killing phenomenon was reproduced in a virus-free system by cocultivating ALV-B Env-expressing cells with TVB(S3)-expressing cells. Taken together, our results indicated that ALV-B-mediated apoptosis is triggered by ALV-B Env-TVB(S3) interactions. 相似文献
134.
135.
136.
Probanza A Mateos JL Lucas García JA Ramos B De Felipe MR Gutierrez Mañero FJ 《Microbial ecology》2001,41(2):140-148
The effect of co-inoculation with Pisolithus tinctorius and a PGPR belonging to the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105) in enhancing growth of Pinus pinea plants and the changes that occurred in rhizosphere microbial communities and the degree of mycorrhization were evaluated.
Both bacterial strains of Bacillus promote the growth of Pinus pinea seedlings, but this biological effect does not imply a synergic effect with mycorrhizal infection. However, the positive
response to mycorrhiza in a longer-term experiment it could be expected. The introduction of both inocula causes an lateration
in the microbial rhizosphere composition, despite the low levels of inocula that were found at the end of the assay. 相似文献
137.
High yield of endoreduplication induced by ICRF-193: a topoisomerase II catalytic inhibitor 总被引:4,自引:0,他引:4
Previous studies have demonstrated that phenolic compounds, including genistein (4',5,7-trihydroxyisoflavone) and resveratrol (3,4',5-trihydroxystilbene), are able to protect against carcinogenesis in animal models. This study was undertaken to examine the ability of genistein and resveratrol to inhibit reactive oxygen species (ROS)-mediated strand breaks in phi X-174 plasmid DNA. H(2)O(2)/Cu(II) and hydroquinone/Cu(II) were used to cause oxidative DNA strand breaks in the plasmid DNA. We demonstrated that the presence of genistein at micromolar concentrations resulted in a marked inhibition of DNA strand breaks induced by either H(2)O(2)/Cu(II) or hydroquinone/Cu(II). Genistein neither affected the Cu(II)/Cu(I) redox cycle nor reacted with H(2)O(2) suggest that genistein may directly scavenge the ROS that participate in the induction of DNA strand breaks. In contrast to the inhibitory effects of genistein, the presence of resveratrol at similar concentrations led to increased DNA strand breaks induced by H(2)O(2)/Cu(II). Further studies showed that in the presence of Cu(II), resveratrol, but not genistein was able to cause DNA strand breaks. Moreover, both Cu(II)/Cu(I) redox cycle and H(2)O(2) were shown to be critically involved in resveratrol/copper-mediated DNA strand breaks. The above results indicate that despite their similar in vivo anticarcinogenic effects, genistein and resveratrol appear to exert different effects on oxidative DNA damage in vitro. 相似文献
138.
139.
Chambergo FS Bonaccorsi ED Ferreira AJ Ramos AS Ferreira Júnior JR Abrahão-Neto J Farah JP El-Dorry H 《The Journal of biological chemistry》2002,277(16):13983-13988
Despite the intense interest in the metabolic regulation and evolution of the ATP-producing pathways, the long standing question of why most multicellular microorganisms metabolize glucose by respiration rather than fermentation remains unanswered. One such microorganism is the cellulolytic fungus Trichoderma reesei (Hypocrea jecorina). Using EST analysis and cDNA microarrays, we find that in T. reesei expression of the genes encoding the enzymes of the tricarboxylic acid cycle and the proteins of the electron transport chain is programmed in a way that favors the oxidation of pyruvate via the tricarboxylic acid cycle rather than its reduction to ethanol by fermentation. Moreover, the results indicate that acetaldehyde may be channeled into acetate rather than ethanol, thus preventing the regeneration of NAD(+), a pivotal product required for anaerobic metabolism. The studies also point out that the regulatory machinery controlled by glucose was most probably the target of evolutionary pressure that directed the flow of metabolites into respiratory metabolism rather than fermentation. This finding has significant implications for the development of metabolically engineered cellulolytic microorganisms for fuel production from cellulose biomass. 相似文献
140.
Felipe AE Teruel MT Cabodevila JA Callejas SS 《Reproduction, nutrition, development》2002,42(1):15-24
The purpose of the present study was to determine the chronology of the pre-implantation embryonic development in Myocastor coypus (coypu). It was carried out by daily colpocytological examination and controlled mating of 33 females. Oocytes and embryos were obtained by flushing from day 0 to day 10 post-coitus (p.c.). On day 1 p.c., oocytes predominated whereas on day 2 p.c. zygotes were predominant. The cleavage period was from day 3 to day 6 p.c.. Morulae were collected from day 6 to day 9 p.c., whereas blastocysts were collected on days 8 and 9. From oviduct flushing, the embryos in the zygote stage and up to the morula stage with less than a 30-cell stage were recovered. Embryos in the morula stage with 30 or more cells and up to the growing blastocyst stage were collected from the flushing of hemiuteri. 相似文献