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961.
JÉRÔME ORIVEL JULIEN GRANGIER JULIEN FOUCAUD JULIEN LE BRETON FRANÇOIS‐XAVIER ANDRÈS HERVÉ JOURDAN JACQUES H. C. DELABIE DENIS FOURNIER PHILIPPE CERDAN BENOIT FACON ARNAUD ESTOUP ALAIN DEJEAN 《Ecological Entomology》2009,34(4):504-512
Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges. 相似文献
962.
963.
Lörinczi E Napp J Contreras-Jurado C Pardo LA Stühmer W 《European biophysics journal : EBJ》2009,38(3):279-284
The ether-à-go-go potassium channels hEag1 and hEag2 are highly homologous. Even though both possess identical voltage-sensing
domain S4, the channels act differently in response to voltage. Therefore we asked whether transmembrane domains other than
the voltage sensor could contribute to the voltage-dependent behaviour of these potassium channels. For this chimaeras were
created, in which each single transmembrane domain of hEag1 was replaced by the corresponding segment of hEag2. The voltage-dependent
properties of the chimaeras were analysed after expression in Xenopus laevis oocytes using the two-electrode voltage-clamp method. By this we found, that only the mutations in transmembrane domains
S5 and S6 are able to change the voltage sensitivity of hEag1 by shifting the half-activation potential (V
50) to values intermediate between the two wild types. Moreover, the presence of Mg2+ has strong effects on the voltage sensitivity of hEag2 shifting V
50 by more than 50 mV to more positive values. Interestingly, despite the identical binding site Mg2+ showed only little effects on hEag1 or the chimaeras. Altogether, our data suggest that not only transmembrane spanning regions,
but also non-membrane spanning regions are responsible for differences in the behaviour of the hEag1 and hEag2 potassium channels.
EBSA Satellite meeting: Ion channels, Leeds, July 2007. 相似文献
964.
This study describes the preparation of two new chelating materials derived from succinylated mercerized cellulose (cell 1). Cell 1 was activated through two different methods by using diisopropylcarbodiimide and acetic anhydride (to form an internal anhydride) and reacted with triethylenetetramine in order to obtain cell 2 and 4. New modified celluloses were characterized by mass percent gain, concentration of amine functions, elemental analysis, and infrared spectroscopy. Cell 2 and 4 showed degrees of amination of 2.8 and 2.3 mmol/g and nitrogen content of 6.07% and 4.61%, respectively. The capacity of cell 2 and 4 to adsorb Cu2+, Cd2+, and Pb2+ ions from single aqueous solutions were examined. The effect of contact time, pH, and initial concentration of metal ions on the metal ions uptake was also investigated. Adsorption isotherms were well fitted by the Langmuir model. The maximum adsorption capacity of cell 2 and 4 were found to be 56.8 and 69.4 mg/g for Cu2+; 68.0 and 87.0 mg/g for Cd2+; and 147.1 and 192.3 mg/g for Pb2+, respectively. 相似文献
965.
966.
Simon Blanchet Lionel Méjean Jean-François Bourque Sovan Lek Frédéric Thomas David J. Marcogliese Julian J. Dodson Géraldine Loot 《Oecologia》2009,160(1):37-47
Phenotypic differences between infected and non-infected hosts are often assumed to be the consequence of parasite infection.
However, pre-existing differences in hosts’ phenotypes may promote differential susceptibility to infection. The phenotypic
variability observed within the host population may therefore be a cause rather than a consequence of infection. In this study,
we aimed at disentangling the causes and the consequences of parasite infection by calculating the value of a phenotypic trait
(i.e., the growth rate) of the hosts both before and after infection occurred. That procedure was applied to two natural systems
of host–parasite interactions. In the first system, the infection level of an ectoparasite (Tracheliastes polycolpus) decreases the growth rate of its fish host (the rostrum dace, Leuciscus leuciscus). Reciprocally, this same phenotypic trait before infection modulated the future level of host sensitivity to the direct
pathogenic effect of the parasite, namely the level of fin degradation. In the second model, causes and consequences linked
the growth rate of the fish host (the rainbow smelt, Osmerus mordax) and the level of endoparasite infection (Proteocephalus tetrastomus). Indeed, the host’s growth rate before infection determined the number of parasites later in life, and the parasite biovolume
then decreased the host’s growth rate of heavily infected hosts. We demonstrated that reciprocal effects between host phenotypes
and parasite infection can occur simultaneously in the wild, and that the observed variation in the host phenotype population
was not necessarily a consequence of parasite infection. Disentangling the causality of host–parasite interactions should
contribute substantially to evaluating the role of parasites in ecological and evolutionary processes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
967.
Functional Characterization of the Arabidopsis β-Ketoacyl-Coenzyme A Reductase Candidates of the Fatty Acid Elongase 总被引:1,自引:0,他引:1 下载免费PDF全文
968.
Hugues Guyot Claude Saegerman Pascal Lebreton Charlotte Sandersen Frédéric Rollin 《Journal of trace elements in medicine and biology》2009,23(2):116-123
Selenium (Se), iodine (I), zinc (Zn) and copper (Cu) deficiencies in cattle have been reported in Europe. These deficiencies are often associated with diseases. The aim of the study was to assess trace element status in Belgian cattle herds showing pathologies and to compare them to healthy cattle herds. Eighty-two beef herds with pathologies, 11 healthy beef herds, 65 dairy herds with pathologies and 20 healthy dairy herds were studied during barn period. Blood and/or milk samples were taken in healthy animals. Plasma Zn, Cu, inorganic I (PII) and activity of glutathione peroxidase in erythrocytes (GPX) were assayed. In milk, I concentration was measured. Data about pathologies and nutrition in the herds were collected. According to defined thresholds, it appeared that a large proportion of deficient herds belonged to “sick” group of herds. This conclusion was supported by the mean value of trace elements and by the fact that a majority of individual values of trace elements was below the threshold. Dairy herds had mean values of trace elements higher than beef herds. More concentrates and minerals were used in healthy herds versus “sick” herds. These feed supplements were also used more often in dairy herds, compared to beef herds. Trace elements deficiencies are present in cattle herds in Belgium and are linked to diseases. Nutrition plays a major role in the trace elements status. 相似文献
969.
Frédéric Schmitt Padavattan Govindaswamy Olivier Zava Georg Süss-Fink Lucienne Juillerat-Jeanneret Bruno Therrien 《Journal of biological inorganic chemistry》2009,14(1):101-109
Mononuclear 5-(4-pyridyl)-10,15,20-triphenylporphyrin and 5-(3-pyridyl)-10,15,20-triphenylporphyrin as well as tetranuclear
5,10,15,20-tetra(4-pyridyl)porphyrin (tetra-4-pp) and 5,10,15,20-tetra(3-pyridyl)porphyrin) (tetra-3-pp) arene ruthenium(II)
derivatives (arene is C6H5Me or p-Pr
i
C6H4Me) were prepared and evaluated as potential dual photosensitizers and chemotherapeutics in human Me300 melanoma cells. In
the absence of light, all tetranuclear complexes were cytotoxic (IC50 ≤ 20 μM), while the mononuclear derivatives were not (IC50 ≥ 100 μM). Kinetic studies of tritiated thymidine and tritiated leucine incorporations in cells exposed to a low concentration
(5 μM) of tetranuclear p-cymene derivatives demonstrated a rapid inhibition of DNA synthesis, while protein synthesis was inhibited only later, suggesting
arene ruthenium–DNA interactions as the initial cytotoxic process. All complexes exhibited phototoxicities toward melanoma
cells when exposed to laser light of 652 nm. At low concentration (5 μM), LD50 of the mononuclear derivatives was between 5 and 10 J/cm2, while for the tetranuclear derivatives LD50 was approximately 2.5 J/cm2 for the [Ru4(η6-arene)4(tetra-4-pp)Cl8] complexes and less than 0.5 J/cm2 for the [Ru4(η6-arene)4(tetra-3-pp)Cl8] complexes. Examination of cells under a fluorescence microscope revealed the [Ru4(η6-arene)4(tetra-4-pp)Cl8] complexes as cytoplasmic aggregates, whereas the [Ru4(η6-arene)4(tetra-3-pp)Cl8] complexes were homogenously dispersed in the cytoplasm. Thus, these complexes present a dual synergistic effect with good
properties of both the arene ruthenium chemotherapeutics and the porphyrin photosensitizer. 相似文献
970.
Capel F Prod'homme M Béchet D Taillandier D Balage M Attaix D Combaret L 《The Journal of nutritional biochemistry》2009,20(8):570-576
Skeletal muscle proteolysis is inhibited by oral feeding in the young and mature but not in the elderly. However, the proteolytic pathway(s) responsible for the decreased muscle proteolysis in the postprandial (PP) state is (are) unknown in the young. Moreover, muscle proteolysis is inhibited by both insulin (INS) and amino acids (AA) in vitro, but their respective roles on specific proteolytic pathways in vivo remain to be elucidated. The aim of this study was to investigate the respective role of INS and AA on the inhibition of proteolytic pathways in the PP state in skeletal muscles from young, mature and old rats. Rats were fed over 1 h either a 25% (AA+) or a 0% (AA-) amino acid/protein meal. In each nutritional condition, PP insulin secretion was maintained (AA+/INS+ and AA-/INS+) or blocked (AA+/INS- and AA-/INS-) with diazoxide injections. We report that the PP inhibition of proteolysis in young rats was mediated by the increased INS secretion and resulted from a down-regulation of both lysosomal and Ca(2+)-dependent proteolysis. Moreover, our data showed that proteasome activities are inhibited by either INS or AA in mature rats, whereas they become selectively insensitive to AA in old rats. In conclusion, the present work provides direct evidence that the lack of PP regulation of proteasome-dependent proteolysis in old rats resulted from a selective resistance to AA. 相似文献