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991.
Aaron G. Carfagnini F. Helen Rodd Kayin B. Jeffers Ashley E. E. Bruce 《Environmental Biology of Fishes》2009,86(3):403-409
Female zebrafish housed in aquaria with spatial complexity (plastic plants) over a 13–16-week period showed reduced levels
of aggressive behavior compared to females in bare tanks. In tanks with plants, there was no relationship between levels of
aggression and fecundity but, in bare tanks, females experiencing the highest levels of aggression showed reduced fecundity.
Our results suggest that it may be beneficial, when maintaining zebrafish at moderate to high densities or working with especially
aggressive strains, to house them in spatially complex conditions. 相似文献
992.
Tetsuya Sakamaki 《Primates; journal of primatology》2009,50(4):321-332
Chimpanzees (Pan troglodytes) form multi-male and multi-female unit groups with fission–fusion grouping patterns. Short-range interaction (SRI) plays
an important role in the unity of these groups and in maintaining social bonds among members. This study evaluated three models
of chimpanzee social structure that differed according to the emphasis each placed on social bonds between the sexes, i.e.,
the male-only, the bisexual, and the male-bonded unit-group model. I investigated differences in SRI between the sexes among
group members in well-habituated wild chimpanzees in Mahale Mountains National Park, Tanzania. I followed six focal adult
males and six females, and quantified their respective SRI with other chimpanzees. Except between subordinate males and adult
females, adults in general engaged in SRI with about 60–90% of the individuals with whom they made visual contact each day,
whether in large or small parties. Although the number of social grooming (SGR) partners was limited, male–male SGR networks
were wider than were either male–female or female–female SGR networks among adults. The number of contact-seeking behavior
(CSB) partners was also limited, but dominant males had more CSB partners. Adult females mainly interacted by pant-grunt greeting
(PGG) with adult males, but tended to do so mainly with the highest-ranking male(s) within visual contact. These results indicated
that the social bonds among adult males were essential to group unity. Because of clear male dominance, adult females established
peaceful coexistence with all group members despite less frequent SRI with subordinate males by maintaining affiliative social
bonds with dominant males, thereby supporting the male-bonded unit-group model. Adult females had many female SRI partners,
but these interactions did not involve performing conspicuous behaviors, suggesting that females maintain social bonds with
other females in ways that differ from how such bonds are maintained with and between adult males. 相似文献
993.
Learning involves a usually adaptive response to an input (an external stimulus or the organism℉s own behaviour) in which
the input-response relation is memorized; some physical traces of the relation persist and can later be the basis of a more
effective response. Using toy models we show that this characterization applies not only to the paradigmatic case of neural
learning, but also to cellular responses that are based on epigenetic mechanisms of cell memory. The models suggest that the
research agenda of epigenetics needs to be expanded. 相似文献
994.
Maurecilne Lemes da Silva Daniela Lopes Paim Pinto Miguel Pedro Guerra Eny Iochevet Segal Floh Cláudio Horst Bruckner Wagner Campos Otoni 《Plant Cell, Tissue and Organ Culture》2009,99(1):47-54
The objective of the present work was to induce somatic embryogenesis from zygotic embryos of Passiflora cincinnata Masters. Zygotic embryos formed calli on media with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and
4.5 μM benzyladenine (BA) after 30 days of in vitro culture. A concentration of 18.1 μM 2,4-D resulted in the largest number
of somatic embryos. Embryogenic calli were yellowish and friable, forming whitish proembryogenic masses. Morphologically,
embryogenic cells were small and had large nuclei and dense cytoplasm, whereas non-embryogenic cells were elongated, with
small nuclei and less dense cytoplasm. Calli cultured under white light on basal Murashige and Skoog’s medium with activated
charcoal produced embryos in all developmental stages. There were differences among the treatments, with some leading to the
production of calli with embryos and some only to callus formation. Some abnormalities were associated with somatic embryos,
including fused axes, fused cotyledons and polycotyledonary embryos. Production of secondary somatic embryos occurred in the
first cycle of primary embryo development. Secondary embryos differentiated from the surface of the protodermal layer of primary
embryos with intense cell proliferation, successive mitotic divisions in the initial phase of embryoid development, and a
vascular system formed with no connection to the parental tissue. This secondary embryogenic system of P. cincinnata is characterized by intense proliferation and maintenance of embryogenic competence after successive subcultures. This reproducible
protocol opens new prospects for massive propagation and is an alternative to the current organogenesis-based transformation
protocol. 相似文献
995.
996.
Georg Carlsson Cecilia Palmborg Ari Jumpponen Michael Scherer-Lorenzen Peter Högberg Kerstin Huss-Danell 《Plant Ecology》2009,205(1):87-104
This study is the first to investigate quantitative effects of plant community composition and diversity on N2 fixation in legumes. N2 fixation in three perennial Trifolium species grown in field plots with varied number of neighbouring species was evaluated with the 15N natural abundance method (two field sites, several growing seasons, no N addition) and the isotope dilution method (one
site, one growing season, 5 g N m−2). The proportion of plant N derived from N2 fixation, pNdfa, was generally high, but the N addition decreased pNdfa, especially in species-poor communities. Also following
N addition, the presence of grasses in species-rich communities increased pNdfa in T. hybridum and T. repens L., while legume abundance had the opposite effect. In T. repens, competition for light from grasses appeared to limit growth and thereby the amount of N2 fixed at the plant level, expressed as mg N2 fixed per sown seed. We conclude that the occurrence of diversity effects seems to be largely context dependent, with soil N availability being
a major determinant, and that species composition and functional traits are more important than species richness regarding
how neighbouring plant species influence N2 fixation in legumes. 相似文献
997.
Ray C. Bartolo Natalie Harfoot Mike Gill Kristy Demmers Bernie McLeod A. Grant Butt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(8):997-1010
The colon of the brushtail possum does not have an electrogenic secretory response. Given the functional significance of electrogenic
Cl− secretion in the intestine of eutherian mammals, we have investigated the secretory response in the small intestine of this
marsupial. In the Ussing chamber cAMP-dependent secretagogues stimulated a sustained increase in ileal short-circuit current
(Isc), whereas Ca2+-dependent secretagogues induced a transient increase. Both the responses were inhibited by mucosal addition of the anion
channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (100 μmol l−1), consistent with an anion secretory response. However, the responses were not inhibited by serosal bumetanide (10 μmol l−1) and were independent of bath Cl−, indicating that the stimulated ileal Isc does not involve electrogenic Cl− secretion driven by the NaK2Cl cotransporter, NKCC1. Consistent with this, there were low levels of NKCC1 expression in the
ileal epithelium. In particular, NKCC1 expression in the ileal crypt cells was comparable to that of the villous cells. This
differs from eutherian mammals where high levels of NKCC1 expression in the ileal crypt cells are associated with their role
in Cl− secretion. The cAMP- and Ca2+-dependent secretory responses were inhibited by the removal of HCO3
− suggesting that these responses were due to electrogenic HCO3
− secretion. We conclude that the ileum of the possum does not secrete Cl− due to low levels of NKCC1 expression. It does however appear to secrete HCO3
−. These results are further significant examples of differences in the transport function of the possum intestinal epithelium
compared with eutherian mammals. 相似文献
998.
999.
Effects of crude oil on survival,morphology, and anatomy of two aquatic macrophytes from the Amazon floodplains 总被引:1,自引:0,他引:1
Aline Lopes Sonia Maciel da Rosa-Osman Maria Teresa Fernandez Piedade 《Hydrobiologia》2009,636(1):295-305
Aquatic herbaceous macrophytes grow in profusion in the Amazon fertile varzea floodplains. A large number of species occur
but only a few are particularly abundant, supporting food chains, contributing substantially to carbon and nutrient cycles.
Their growth and role in the ecosystem depend, among other, on its life cycles and habits, floating or semi-aquatic. Although
in the last decades, petroliferous activity intensified in the Central Amazon region and so did oil spills, the effect of
petroleum on the native aquatic plants is unknown. The present study was designed to test experimentally the survival and
morpho-anatomical modifications of the free floating water hyacinth Eichhornia crassipes and the semi-aquatic grass Echinochloa polystachya to 10 different concentrations of crude oil. Higher concentrations of crude oil caused the mortality in both species; however,
lethal dose (LD50) values showed that E. polystachya was more sensitive than E. crassipes. Despite the higher tolerance of E. crassipes, the inhibition of root and leaf growth as well as anatomical modifications in leaves were registered in higher concentrations.
Additionally, the oil caused a reduction in leaf numbers in both species. Although mortality of the floating species was lower,
it may increases over time, since important alterations in morphology and anatomy occurred. These results show that oil spills
in the Amazon varzea can cause severe alterations in the aquatic flora and in the floodplain dynamics. 相似文献
1000.
Malin Sandström Anders Lansner Jeanette Hellgren-Kotaleski Jean-Pierre Rospars 《Journal of computational neuroscience》2009,27(3):337-355
We modeled the firing rate of populations of olfactory receptor neurons (ORNs) responding to an odorant at different concentrations.
Two cases were considered: a population of ORNs that all express the same olfactory receptor (OR), and a population that expresses
many different ORs. To take into account ORN variability, we replaced single parameter values in a biophysical ORN model with
values drawn from statistical distributions, chosen to correspond to experimental data. For ORNs expressing the same OR, we
found that the distributions of firing frequencies are Gaussian at all concentrations, with larger mean and standard deviation
at higher concentrations. For a population expressing different ORs, the distribution of firing frequencies can be described
as the superposition of a Gaussian distribution and a lognormal distribution. Distributions of maximum value and dynamic range
of spiking frequencies in the simulated ORN population were similar to experimental results. 相似文献