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991.
Martin Singheiser Dennis T. T. Plachta Sandra Brill Peter Bremen Robert F. van der Willigen Hermann Wagner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2010,196(3):227-240
We studied the influence of frequency on sound localization in free-flying barn owls by quantifying aspects of their target-approaching
behavior to a distant sound source during ongoing auditory stimulation. In the baseline condition with a stimulus covering
most of the owls hearing range (1–10 kHz), all owls landed within a radius of 20 cm from the loudspeaker in more than 80%
of the cases and localization along the azimuth was more accurate than localization in elevation. When the stimulus contained
only high frequencies (>5 kHz) no changes in striking behavior were observed. But when only frequencies from 1 to 5 kHz were
presented, localization accuracy and precision decreased. In a second step we tested whether a further border exists at 2.5 kHz
as suggested by optimality models. When we compared striking behavior for a stimulus having energy from 2.5 to 5 kHz with
a stimulus having energy between 1 and 2.5 kHz, no consistent differences in striking behavior were observed. It was further
found that pre-takeoff latency was longer for the latter stimulus than for baseline and that center frequency was a better
predictor for landing precision than stimulus bandwidth. These data fit well with what is known from head-turning studies
and from neurophysiology. 相似文献
992.
Ilka Wittig Bjoern Meyer Heinrich Heide Mirco Steger Lea Bleier Zibiernisha Wumaier Michael Karas Hermann Schägger 《BBA》2010,1797(6-7):1004-1011
Here we study ATP synthase from human ρ0 (rho zero) cells by clear native electrophoresis (CNE or CN-PAGE) and show that ATP synthase is almost fully assembled in spite of the absence of subunits a and A6L. This identifies subunits a and A6L as two of the last subunits to complete the ATP synthase assembly. Minor amounts of dimeric and even tetrameric forms of the large assembly intermediate were preserved under the conditions of CNE, suggesting that it associated further into higher order structures in the mitochondrial membrane. This result was reminiscent to the reduced amounts of dimeric and tetrameric ATP synthase from yeast null mutants of subunits e and g detected by CNE. The dimer/oligomer-stabilizing effects of subunits e/g and a/A6L seem additive in human and yeast cells. The mature IF1 inhibitor was specifically bound to the dimeric/oligomeric forms of ATP synthase and not to the monomer. Conversely, nonprocessed pre-IF1 still containing the mitochondrial targeting sequence was selectively bound to the monomeric assembly intermediate in ρ0 cells and not to the dimeric form. This supports previous suggestions that IF1 plays an important role in the dimerization/oligomerization of mammalian ATP synthase and in the regulation of mitochondrial structure and function. 相似文献
993.
994.
Hermann B. Frieboes Fang Jin Yao-Li Chuang John S. Lowengrub Vittorio Cristini 《Journal of theoretical biology》2010,264(4):1254-1278
We extend the diffuse interface model developed in Wise et al. (2008) to study nonlinear tumor growth in 3-D. Extensions include the tracking of multiple viable cell species populations through a continuum diffuse-interface method, onset and aging of discrete tumor vessels through angiogenesis, and incorporation of individual cell movement using a hybrid continuum-discrete approach. We investigate disease progression as a function of cellular-scale parameters such as proliferation and oxygen/nutrient uptake rates. We find that heterogeneity in the physiologically complex tumor microenvironment, caused by non-uniform distribution of oxygen, cell nutrients, and metabolites, as well as phenotypic changes affecting cellular-scale parameters, can be quantitatively linked to the tumor macro-scale as a mechanism that promotes morphological instability. This instability leads to invasion through tumor infiltration of surrounding healthy tissue. Models that employ a biologically founded, multiscale approach, as illustrated in this work, could help to quantitatively link the critical effect of heterogeneity in the tumor microenvironment with clinically observed tumor growth and invasion. Using patient tumor-specific parameter values, this may provide a predictive tool to characterize the complex in vivo tumor physiological characteristics and clinical response, and thus lead to improved treatment modalities and prognosis. 相似文献
995.
Alejandra J. Troncoso Nancy J. Cabezas Eric H. Faúndez Alejandro Urzúa Hermann M. Niemeyer 《Oecologia》2010,162(2):413-425
Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their
mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct
hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was
performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied
to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory
cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past
their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display
characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators,
(2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical
profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds
from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species
regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual
organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects. 相似文献
996.
Clemens Röhrl Stefanie Fruhwürth Sabine Maria Schreier Alfred Lohninger Andrea Dolischka Manfred Hüttinger Nina Zemann Marcela Hermann Witta Strobl Herbert Stangl 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2010,1801(2):198-204
Recent evidence suggests that scavenger receptor, class B, type I (SR-BI) plays a physiological role in VLDL metabolism. SR-BI was reported to mediate β-VLDL uptake; however, cellular details of this process are not well characterized. In the present study we show that SR-BI delivers cholesterol derived from β-VLDL to LDL receptor negative SR-BI over-expressing Chinese Hamster Ovarian cells (ldlA7-SRBI). Cell association of β-VLDL was ∼ 3 times higher after SR-BI over-expression, which was competed by β-VLDL, but only to a lesser extent by HDL and LDL. Almost all of the associated β-VLDL was located intracellularly, and therefore could not be released by a 50-fold excess of unlabeled β-VLDL. β-VLDL was degraded at a rate of 6 ng β-VLDL/mg cell protein and hour. In contrast to ldlA7 cells, β-VLDL association was competed by LDL in cells with a functional LDL receptor like CHO and HepG2 cells, indicating a strong impact of the LDL receptor in β-VLDL uptake. β-VLDL degradation was similar to ldlA7-SRBI cells. When β-VLDL uptake was followed using fluorescence microscopy, β-VLDL showed a different uptake pattern in SR-BI over-expressing cells, ldlA7-SRBI, compared to LDL receptor containing cells, CHO and HepG2. 相似文献
997.
Graham H. Pyke Paul R. Ehrlich 《Biological reviews of the Cambridge Philosophical Society》2010,85(2):247-266
Housed worldwide, mostly in museums and herbaria, is a vast collection of biological specimens developed over centuries. These biological collections, and associated taxonomic and systematic research, have received considerable long‐term public support. The work remaining in systematics has been expanding as the estimated total number of species of organisms on Earth has risen over recent decades, as have estimated numbers of undescribed species. Despite this increasing task, support for taxonomic and systematic research, and biological collections upon which such research is based, has declined over the last 30‐40 years, while other areas of biological research have grown considerably, especially those that focus on environmental issues. Reflecting increases in research that deals with ecological questions (e.g. what determines species distribution and abundance) or environmental issues (e.g. toxic pollution), the level of research attempting to use biological collections in museums or herbaria in an ecological/environmental context has risen dramatically during about the last 20 years. The perceived relevance of biological collections, and hence the support they receive, should be enhanced if this trend continues and they are used prominently regarding such environmental issues as anthropogenic loss of biodiversity and associated ecosystem function, global climate change, and decay of the epidemiological environment. It is unclear, however, how best to use biological collections in the context of such ecological/environmental issues or how best to manage collections to facilitate such use. We demonstrate considerable and increasingly realized potential for research based on biological collections to contribute to ecological/environmental understanding. However, because biological collections were not originally intended for use regarding such issues and have inherent biases and limitations, they are proving more useful in some contexts than in others. Biological collections have, for example, been particularly useful as sources of information regarding variation in attributes of individuals (e.g. morphology, chemical composition) in relation to environmental variables, and provided important information in relation to species' distributions, but less useful in the contexts of habitat associations and population sizes. Changes to policies, strategies and procedures associated with biological collections could mitigate these biases and limitations, and hence make such collections more useful in the context of ecological/environmental issues. Haphazard and opportunistic collecting could be replaced with strategies for adding to existing collections that prioritize projects that use biological collections and include, besides taxonomy and systematics, a focus on significant environmental/ecological issues. Other potential changes include increased recording of the nature and extent of collecting effort and information associated with each specimen such as nearby habitat and other individuals observed but not collected. Such changes have begun to occur within some institutions. Institutions that house biological collections should, we think, pursue a mission of ‘understanding the life of the planet to inform its stewardship’ ( Krishtalka & Humphrey, 2000 ), as such a mission would facilitate increased use of biological collections in an ecological/environmental context and hence lead to increased appreciation, encouragement and support from the public for these collections, their associated research, and the institutions that house them. 相似文献
998.
Donati C Hiller NL Tettelin H Muzzi A Croucher NJ Angiuoli SV Oggioni M Dunning Hotopp JC Hu FZ Riley DR Covacci A Mitchell TJ Bentley SD Kilian M Ehrlich GD Rappuoli R Moxon ER Masignani V 《Genome biology》2010,11(10):R107-19
Background
Streptococcus pneumoniae is one of the most important causes of microbial diseases in humans. The genomes of 44 diverse strains of S. pneumoniae were analyzed and compared with strains of non-pathogenic streptococci of the Mitis group.Results
Despite evidence of extensive recombination, the S. pneumoniae phylogenetic tree revealed six major lineages. With the exception of serotype 1, the tree correlated poorly with capsular serotype, geographical site of isolation and disease outcome. The distribution of dispensable genes - genes present in more than one strain but not in all strains - was consistent with phylogeny, although horizontal gene transfer events attenuated this correlation in the case of ancient lineages. Homologous recombination, involving short stretches of DNA, was the dominant evolutionary process of the core genome of S. pneumoniae. Genetic exchange occurred both within and across the borders of the species, and S. mitis was the main reservoir of genetic diversity of S. pneumoniae. The pan-genome size of S. pneumoniae increased logarithmically with the number of strains and linearly with the number of polymorphic sites of the sampled genomes, suggesting that acquired genes accumulate proportionately to the age of clones. Most genes associated with pathogenicity were shared by all S. pneumoniae strains, but were also present in S. mitis, S. oralis and S. infantis, indicating that these genes are not sufficient to determine virulence.Conclusions
Genetic exchange with related species sharing the same ecological niche is the main mechanism of evolution of S. pneumoniae. The open pan-genome guarantees the species a quick and economical response to diverse environments. 相似文献999.
Jens Selige Hermann Tenor Armin Hatzelmann Torsten Dunkern 《Journal of cellular physiology》2010,223(2):317-326
Interleukin‐1β (IL‐1β) and basic fibroblast growth factor (bFGF) are important regulators of proliferation, and their expression is increased in lungs of patients with asthma, idiopathic pulmonary fibrosis (IPF), or chronic obstructive pulmonary disease (COPD). We investigated the effect of IL‐1β and bFGF on proliferation of human lung fibroblasts and the role of COX‐2, PGE2, and cAMP in this process. Furthermore, the effect of phosphodiesterase (PDE) 3 and 4 inhibition was analyzed. In primary human lung fibroblasts low concentrations of IL‐1β (<10 pg/ml) potentiated the bFGF‐induced DNA synthesis, whereas higher concentrations revealed antiproliferative effects. Higher concentrations of IL‐1β‐induced COX‐2 mRNA and protein associated with an increase in PGE2 and cAMP, and all of these parameters were potentiated by bFGF. The PDE4 inhibitor piclamilast concentration‐dependently reduced proliferation by a partial G1 arrest. The PDE3 inhibitor motapizone was inactive by itself but enhanced the effect of the PDE4 inhibitor. This study demonstrates that bFGF and IL‐1β act in concert to fine‐tune lung fibroblast proliferation resulting in amplification or reduction. The antiproliferative effect of IL‐1β is likely attributed to the induction of COX‐2, which is further potentiated by bFGF, and the subsequent generation of PGE2 and cAMP. Inhibition of PDE4 inhibition (rather than PDE3) may diminish proliferation of human lung fibroblasts and therefore could be useful in the therapy of pathological remodeling in lung diseases. J. Cell. Physiol. 223: 317–326, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
1000.
Johannes S. Gach Paul G. Furtm��ller Heribert Quendler Paul Messner Ralf Wagner Hermann Katinger Renate Kunert 《The Journal of biological chemistry》2010,285(2):1122-1127
The human monoclonal antibody 2G12 is a member of a small group of broadly neutralizing antibodies against human immunodeficiency virus type 1. 2G12 adopts a unique variable heavy domain-exchanged dimeric configuration that results in an extensive multivalent binding surface and the ability to bind with high affinity to densely clustered high mannose oligosaccharides on the “silent” face of the gp120 envelope glycoprotein. Here, we further define the amino acids responsible for this extraordinary domain-swapping event in 2G12. 相似文献