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741.
Kelly F. O. Ribeiro Valria F. Martins Thorsten Wiegand Flavio A. M. Santos 《Ecology and evolution》2021,11(4):1797
The investigation of ecological processes that maintain species coexistence is revealing in naturally disturbed environments such as the white‐sand tropical forest, which is subject to periodic flooding that might pose strong habitat filtering to tree species. Congeneric species are a good model to investigate the relative importance of ecological processes that maintain high species diversity because they tend to exploit the same limiting resources and/or have similar tolerance limits to the same environmental conditions due to their close phylogenetic relationship. We aim to find evidence for the action and relative importance of different processes hypothesized to maintain species coexistence in a white‐sand flooded forest in Brazil, taking advantage of data on the detailed spatial structure of populations of congeneric species. Individuals of three Myrcia species were tagged, mapped, and measured for diameter at soil height in a 1‐ha plot. We also sampled seven environmental variables in the plot. We employed several spatial point process models to investigate the possible action of habitat filtering, interspecific competition, and dispersal limitation. Habitat filtering was the most important process driving the local distribution of the three Myrcia species, as they showed associations, albeit of different strength, to environmental variables related to flooding. We did not detect spatial patterns, such as spatial segregation and smaller size of nearby neighbors, that would be consistent with interspecific competition among the three congeneric species and other co‐occurring species. Even though congeners were spatially independent, they responded to differences in the environment. Last, dispersal limitation only led to spatial associations of different size classes for one of the species. Given that white‐sand flooded forests are highly threatened in Brazil, the preservation of their different habitats is of utmost importance to the maintenance of high species richness, as flooding drives the distribution of species in the community. 相似文献
742.
María M. Caffaro Jorge M. Vivanco Flavio H. Gutierrez Boem Gerardo Rubio 《Plant Growth Regulation》2011,64(3):241-249
Root architecture is of key importance for plant nutrition and performance. It is known that root architecture is determined
by genetics and environmental conditions. The aim of the present study was to evaluate if root exudation within a given plant
has a role in the development of root architecture. We conducted a series of experiments using Arabidopsis thaliana Ler and Col grown with and without activated charcoal (AC). The addition of AC lowered the concentration of secondary metabolites
in the growth media by more than 90%. Our results consistently showed that the addition of AC significantly decreased the
number of lateral roots (38% in Ler and 27% in Col), but this decrease was compensated by an increase in the root length per
unit of lateral root (83% in Ler and 96% in Col). This compensation resulted in a non-significant effect of AC on the total
length of lateral roots. The effects of AC on root architecture were partially or totally reverted by the differential supplementation
of root exudates from other plants of the same ecotype. Our results indicate a direct role of secondary metabolites present
in the root exudates in the development of root architecture. 相似文献
743.
Marcio Nucci Arnaldo L. Colombo Flavio Queiroz-Telles 《Current fungal infection reports》2009,3(1):15-20
Paracoccidioidomycosis is the most frequent endemic mycosis in South America. The infection is more prevalent in rural workers,
and recent epidemiologic data suggest that changes in agricultural practices (such as a decrease in coffee plantations and
an increase in sugar cane plantations) may result in a reduction in the incidence of infection. After being inhaled, Paracoccidioides brasiliensis usually causes a benign and transient pulmonary infection that may progress to an acute form or, more frequently, reactivate
later as a chronic disease. The diagnosis is usually made by direct examination and culture of clinical specimens; serologic
tests may be of help, especially antigen detection. The drug of choice for the chronic form is oral itraconazole, whereas
patients with more severe forms may be treated with intravenous amphotericin B or sulfamethoxazoletrimethoprim. The newer
azole voriconazole is also effective, and it may be a good alternative because it can be given by oral or intravenous route. 相似文献
744.
Chromoblastomycosis (CBM) is an implantation mycosis mainly occurring in tropical and subtropical zones worldwide. If not diagnosed at early stages, patients with CBM require long-term therapy with systemic antifungals flanked by various physical treatment regimens. As in other neglected endemic mycoses, comparative clinical trials have not been performed for this disease; nowadays, therapy is mainly based on a few open trials and on expert opinions. Itraconazole, either as monotherapy or associated with other drugs, or with physical methods, is widely used. Recently, photodynamic therapy has been employed successfully in combination with antifungals in patients presenting with CBM. In the present paper, the most used therapeutic options against CBM are reviewed as well as the several factors that may have impact on the patient’s outcome. 相似文献
745.
Besides the excavation of underground nest chambers, Atta vollenweideri grass-cutting ants build ventilation turrets on the topmost openings of their huge nests. Turret construction was studied
in a laboratory colony, addressing the question whether turrets are simply heaps of disposed soil, or result from the import
and a particular spatial arrangement of materials. The colony was daily offered different building materials, i.e., clay,
coarse and fine sands, which workers collected and deposited around a nest opening to construct a turret. After 10 days, the
spatial arrangement of the different building materials, offered either simultaneously or consecutively in independent experiments,
was characterized via thin sections and micromorphological analysis of the turret’s walls. Workers did not select particular
materials to be imported for turret building, but were selective in their spatial distribution and assembly into the turret
structure. Particular types of microstructures were observed depending on the available materials, such as simple piles of
sands, porous fabrics only composed of clay pellets, or fabrics with clay and sands combined. Turrets were very dynamic structures:
while most imported materials were initially piled up at the shortest distance from the source, a marked subsequent material
redistribution occurred as the turret grew, resulting in a new, mixed structure. Material re-assembly was particular evident
when clay and sands were offered consecutively: a remarkable tendency to construct microstructures combining both materials
was observed, i.e., clays were mobilized and included in sandy walls, and sands were intercalated in much compact clay walls.
Irrespective of the materials used, walls showed a marked regular porosity in the range 50–60%, with the exception of secondary
galleries that occasionally permeated the turret structure, which evinced lower porosity and therefore a more compact microstructure.
Ants appeared to respond to local variations in the structural stability of the construction, since clay coatings smoothed
and reinforced the surface of unstable sandy gallery walls. The observed building responses appear to be aimed at the maintenance
of a porous yet mechanically-stable structure. The attained turret porosity may represent a compromise between high structural
stability and low construction costs because of savings in material import. 相似文献
746.
Victor A. Cortes Dolores Busso Pablo Mardones Alberto Maiz Antonio Arteaga Flavio Nervi Attilio Rigotti 《Biological reviews of the Cambridge Philosophical Society》2013,88(4):825-843
Cholesterol has evolved to fulfill sophisticated biophysical, cell signalling, and endocrine functions in animal systems. At the cellular level, cholesterol is found in membranes where it increases both bilayer stiffness and impermeability to water and ions. Furthermore, cholesterol is integrated into specialized lipid‐protein membrane microdomains with critical topographical and signalling functions. At the organismal level, cholesterol is the precursor of all steroid hormones, including gluco‐ and mineralo‐corticoids, sex hormones, and vitamin D, which regulate carbohydrate, sodium, reproductive, and bone homeostasis, respectively. This sterol is also the immediate precursor of bile acids, which are important for intestinal absorption of dietary lipids as well as energy homeostasis and glucose regulation. Complex mechanisms maintain cholesterol within physiological ranges and the dysregulation of these mechanisms results in embryonic or adult diseases, caused by either excessive or reduced tissue cholesterol levels. The causative role of cholesterol in these conditions has been demonstrated by genetic and pharmacological manipulations in animal models of human disease that are discussed herein. Importantly, the understanding of basic aspects of cholesterol biology has led to the development of high‐impact pharmaceutical therapies during the past century. The continuing effort to offer successful treatments for prevalent cholesterol‐related diseases, such as atherosclerosis and neurodegenerative disorders, warrants further interdisciplinary research in the coming decades. 相似文献
747.
Jesús E. Maldonado Flavio Orta Davila Brent S. Stewart Eli Geffen Robert K. Wayne 《Marine Mammal Science》1995,11(1):46-58
Intraspecific patterns of mitochondrial DNA sequence variation were determined among California sea lions ( Zalophus califomianus californianus ) from three colonies along the Pacific coast of southern and Baja California and one colony in the Gulf of California. We found no variation in 368 base pairs (bp) of cytochrome b sequence among 40 sea lions from these localities, but analysis of 360 base pairs of control region revealed eleven genotypes. The four genotypes found in the Gulf of California population were unique and phylogenetically distinct from those found in sea lions along the Pacific coast. The average sequence divergence between Gulf and Southern California genotypes was 4.3%, suggesting a relatively long period of isolation. However, colonies along the Pacific coast, which are less than 200 km apart, shared mtDNA genotypes, indicating that recent genetic exchange has occurred between them. Therefore, we suggest that regional female philopatry exists in California sea lions. Regional boundaries may be related to oceanic currents or patchiness in the distribution of resources. Further research is needed to better understand the underlying causes of genetic differentiation in the California sea lion. 相似文献
748.
The evolution of cranial base and face in Cercopithecoidea and Hominoidea: Modularity and morphological integration 下载免费PDF全文
749.
Depolarized low-frequency Raman spectra from several cyclodextrin–water solutions have been investigated as a function of
both temperature and macrocycle concentration. The differences between the vibrational spectra of solutions and pure water
have been discussed, focusing the attention on the modifications of the vibrational bands assigned to the H-bond bending and
stretching intermolecular modes of water. These features are in turn related to the structural changes occurring in the H-bonded
water molecules allowing us to evince a destructuring effect on the tetrahedral hydrogen bonding arrangements induced in solution
by increasing temperature and solute concentration. 相似文献
750.
Silvia Consalvi Chiara Mozzetta Paolo Bettica Massimiliano Germani Francesco Fiorentini Francesca Del Bene Maurizio Rocchetti Flavio Leoni Valmen Monzani Paolo Mascagni Pier Lorenzo Puri Valentina Saccone 《Molecular medicine (Cambridge, Mass.)》2013,19(1):79-87
Previous work has established the existence of dystrophin–nitric oxide (NO) signaling to histone deacetylases (HDACs) that is deregulated in dystrophic muscles. As such, pharmacological interventions that target HDACs (that is, HDAC inhibitors) are of potential therapeutic interest for the treatment of muscular dystrophies. In this study, we explored the effectiveness of long-term treatment with different doses of the HDAC inhibitor givinostat in mdx mice—the mouse model of Duchenne muscular dystrophy (DMD). This study identified an efficacy for recovering functional and histological parameters within a window between 5 and 10 mg/kg/d of givinostat, with evident reduction of the beneficial effects with 1 mg/kg/d dosage. The long-term (3.5 months) exposure of 1.5-month-old mdx mice to optimal concentrations of givinostat promoted the formation of muscles with increased cross-sectional area and reduced fibrotic scars and fatty infiltration, leading to an overall improvement of endurance performance in treadmill tests and increased membrane stability. Interestingly, a reduced inflammatory infiltrate was observed in muscles of mdx mice exposed to 5 and 10 mg/kg/d of givinostat. A parallel pharmacokinetic/pharmacodynamic analysis confirmed the relationship between the effective doses of givinostat and the drug distribution in muscles and blood of treated mice. These findings provide the preclinical basis for an immediate translation of givinostat into clinical studies with DMD patients. 相似文献