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991.
Current theory suggests that mass change in adult birds while breeding may be adaptive (to reduce wing-loading during nestling
feeding) or result from physiological stress. To test which might be more important in determining mass loss in breeding Savi’s
Warblers (Locustella luscinioides), we used a new approach in which the variation in four indices of body condition was described: weight, fat score, muscle
score and lean weight (i.e. excluding fat and muscle). We expected weight variations to be adaptive if they involved changes
in fat and lean weight, whereas physiological stress should influence the muscle score to a greater extent. As in other species,
females showed a greater variation in weight, and carried more fat, than males during the breeding cycle. During incubation,
females had greater weight and fat score than males. The weight remained constant and lean weight declined in both sexes,
whereas females increased in muscle, which probably reflects the regression of the reproductive organs. During the nestling
stage, both sexes declined significantly in all four indices of condition, showing evidence of physiological stress. However,
the greater decline in weight in females than in males is consistent with the flight-adaptation hypothesis, as are the cyclic
changes in lean weight associated with the various nesting attempts. The fact that both sexes declined significantly in weight,
muscle and lean weight with an increasing number of nesting attempts, but not in fat, which was recovered after each nestling
period, also indicates that both reproductive stress and adaptive changes occur during breeding. When the whole breeding season
was considered, females showed a greater decline in muscle than males, which we interpret to be evidence for a greater reproductive
stress in females. We suggest that the small breast muscle size and depleted protein reserves at the end of the breeding period
might influence future survival through impaired flight ability and a compromised post-breeding moult. 相似文献
992.
Pedro J. Alcolea Manuel J. Gómez Mercedes Domínguez Vicente Larraga 《International journal for parasitology》2010,40(13):1497-1516
Leishmania infantum is the causative agent of zoonotic visceral leishmaniasis in the Mediterranean Basin. The promastigote and amastigote stages alternate in the life cycle of the parasite, developing inside the sand-fly gut and inside mammalian phagocytic cells, respectively. High-throughput genomic and proteomic analyses have not focused their attention on promastigote development, although partial approaches have been made in Leishmania major and Leishmania braziliensis. For this reason we have studied the expression modulation of an etiological agent of visceral leishmaniasis throughout the life cycle, which has been performed by means of complete genomic microarrays. In the context of constitutive genome expression in Leishmania spp. described elsewhere and confirmed here (5.7%), we found a down-regulation rate of 68% in the amastigote stage, which has been contrasted by binomial tests and includes the down-regulation of genes involved in translation and ribosome biogenesis. These findings are consistent with the hypothesis of pre-adaptation of the parasite to intracellular survival at this stage. 相似文献
993.
994.
The chromatin structure is important for recognition and repair of DNA damage. Many DNA damage response proteins accumulate
in large chromatin domains flanking sites of DNA double-strand breaks. The assembly of these structures—usually termed DNA
damage foci—is primarily regulated by MDC1, a large nuclear mediator/adaptor protein that is composed of several distinct
structural and functional domains. Here, we are summarizing the latest discoveries about the mechanisms by which MDC1 mediates
DNA damage foci formation, and we are reviewing the considerable efforts taken to understand the functional implication of
these structures. 相似文献
995.
996.
Maritza Omaña-Molina Arturo González-Robles Ana Ruth Cristóbal-Ramos Edmundo Salinas-Moreno Manuel Sánchez-Cornejo Adolfo Martínez-Palomo 《Experimental parasitology》2010,126(1):73-78
The present study demonstrates that when Acanthamoeba castellanii trophozoites are co-cultivated with isolated human corneas, the amoeba can be invasive and cause damage to the intact corneal epithelium without the requirement of previous corneal abrasion. After adhesion, A. castellanii trophozoites migrate between cells forming bumps on the corneal cell layers and reaching Bowman´s membrane in 3 h, although no evidence of cell damage was observed until the phagocytic process was detected. Likewise, conditioned medium produced damage to the corneal cells that was proportional to the time of incubation, but this cytophatic effect involved only the most superficial layer of the human cornea and was not enough to explain amoebic invasion of Bowman´s membrane. As a result of our observations, we suggest that the mechanical action of the trophozoites and phagocytosis of corneal cells during the process of corneal invasion are more important than previously suggested. 相似文献
997.
Zarazúa S Pérez-Severiano F Delgado JM Martínez LM Ortiz-Pérez D Jiménez-Capdeville ME 《Neurochemical research》2006,31(8):1069-1077
Chronic arsenic exposure is associated with nervous system damage, vascular disease, hepatic and renal damage as well as different types of cancer. Alterations of nitric oxide (NO) in the periphery have been detected after arsenic exposure, and we explored here NO production in the brain. Female Wistar rats were exposed to arsenite in drinking water (4–5 mg/kg/day) from gestation, lactation and until 4 months of age. NOS activity, NO metabolites content, reactive oxygen species production (ROS) and lipid peroxidation (LPx) were determined in vitro in the striatum, and NO production was estimated in vivo measuring citrulline by microdialysis. Exposed animals showed a significantly lower response to NMDA receptor stimulation, reduction of NOS activity and decreased levels of nitrites and nitrates in striatum. These markers of NO function were accompanied by significantly higher levels of LPx and ROS production. These results provide evidence of NO dysfunction in the rat brain associated with arsenic exposure. 相似文献
998.
Within the psychological literature there are a number of models that reproduce the defining properties of habituation to a single stimulus. However, most of them do not reproduce the phenomenon of dishabituation shown in empirical studies, consisting in the recovery of a stimulus previously habituated upon the appearance of a novel stimulus. The present work offers a model of habituation which, in addition to reproducing the basic properties of habituation to a stimulus, also does so when more than one stimulus is presented, and thus includes the dishabituation phenomenon. This model consists of two functions, one called "activation" and the other "availability", and is tested by means of simulation of the responses in the context of different stimulus patterns. The results of the simulation show a good qualitative fit to the empirical results on the phenomena of habituation, including dishabituation. In addition, the model is suitable for inclusion in associative models that reproduce classical conditioning, which will make it possible in the future to incorporate into these in a simple way the influence that the habituation of each stimulus may have on its association with other stimuli. 相似文献
999.
Soria-Díaz ME Rodríguez-Carvajal MA Tejero-Mateo P Espartero JL Morón B Sousa C Megías M Thomas-Oates J Gil-Serrano AM 《FEMS microbiology letters》2006,255(1):164-173
Rhizobium gallicum is a fast-growing bacterium found in European, Australian and African soils; it was first isolated in France. It is a microsymbiont which is able to nodulate plants of the genus Phaseolus. Rhizobium gallicum bv. gallicum R602 produces four extracellular signal molecules consisting of a linear backbone of N-acetyl glucosamine, bearing on the nonreducing terminal residue an N-methyl group and different N-acyl substituents. The four acyloligosaccharides terminate with a sulfated N-acetylglucosaminitol. This unit may be also acetylated. These structures were determined using carbohydrate and methylation analysis, mass spectrometric analysis and one-dimensional- and two-dimensional-nuclear magnetic resonance experiments. This work establishes the common structure that a lipochito-oligosaccharide must have so that the Rhizobium that produces and excretes it is able to nodulate plants of Phaseolus vulgaris. The substituents common to all the molecules are an N-methyl group and a C(18:1) fatty acid on the nonreducing terminal residue. 相似文献
1000.
Noy A Meyer T Rueda M Ferrer C Valencia A Pérez A de la Cruz X López-Bes JM Pouplana R Fernandez-Recio J Luque FJ Orozco M 《Journal of biomolecular structure & dynamics》2006,23(4):447-456
Analysis, storage, and transfer of molecular dynamic trajectories are becoming the bottleneck of computer simulations. In this paper we discuss different approaches for data mining and data processing of huge trajectory files generated from molecular dynamic simulations of nucleic acids. 相似文献