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81.
Evaluating the performance of species richness estimators: sensitivity to sample grain size 总被引:12,自引:1,他引:11
1. Fifteen species richness estimators (three asymptotic based on species accumulation curves, 11 nonparametric, and one based in the species-area relationship) were compared by examining their performance in estimating the total species richness of epigean arthropods in the Azorean Laurisilva forests. Data obtained with standardized sampling of 78 transects in natural forest remnants of five islands were aggregated in seven different grains (i.e. ways of defining a single sample): islands, natural areas, transects, pairs of traps, traps, database records and individuals to assess the effect of using different sampling units on species richness estimations. 2. Estimated species richness scores depended both on the estimator considered and on the grain size used to aggregate data. However, several estimators (ACE, Chao 1, Jackknifel and 2 and Bootstrap) were precise in spite of grain variations. Weibull and several recent estimators [proposed by Rosenzweig et al. (Conservation Biology, 2003, 17, 864-874), and Ugland et al. (Journal of Animal Ecology, 2003, 72, 888-897)] performed poorly. 3. Estimations developed using the smaller grain sizes (pair of traps, traps, records and individuals) presented similar scores in a number of estimators (the above-mentioned plus ICE, Chao2, Michaelis-Menten, Negative Exponential and Clench). The estimations from those four sample sizes were also highly correlated. 4. Contrary to other studies, we conclude that most species richness estimators may be useful in biodiversity studies. Owing to their inherent formulas, several nonparametric and asymptotic estimators present insensitivity to differences in the way the samples are aggregated. Thus, they could be used to compare species richness scores obtained from different sampling strategies. Our results also point out that species richness estimations coming from small grain sizes can be directly compared and other estimators could give more precise results in those cases. We propose a decision framework based on our results and on the literature to assess which estimator should be used to compare species richness scores of different sites, depending on the grain size of the original data, and of the kind of data available (species occurrence or abundance data). 相似文献
82.
Freitas M Da Poian AT Barth OM Rebello MA Silva JL Gaspar LP 《Cell biochemistry and biophysics》2006,44(3):325-335
Mayaro virus is an enveloped virus that belongs to the Alphavirus genus. To gain insight into the mechanism involved in Mayaro virus membrane fusion, we used hydrostatic pressure and low
pH to isolate a fusion-active state of Mayaro glycoproteins. In response to pressure, E1 glycoprotein undergoes structural
changes resulting in the formation of a stable conformation. This state was characterized and correlated to that induced by
low pH as measured by intrinsic fluorescence, 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid, dipotassium salt fluorescence,
fluorescence resonance energy transfer, electron microscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
In parallel, we used a neutralization assay to show that Mayaro virus in the fusogenic state retained most of the original
immunogenic properties and could elicit high titers of neutralizing antibodies. 相似文献
83.
84.
Oliveira AV Gaspar AR Francisco SC Quintela DA 《International journal of biometeorology》2012,56(2):319-332
The present experimental work is dedicated to the analysis of the effect of walking on the thermal insulation of the air layer
(I
a
) and on the convective heat transfer coefficients (h
conv
) of the human body. Beyond the standing static posture, three step rates were considered: 20, 30 and 45 steps/min. This corresponds
to walking speeds of approximately 0.23, 0.34 and 0.51 m/s, respectively. The experiments took place in a climate chamber
with an articulated thermal manikin with 16 independent parts. The indoor environment was controlled through the inner wall
temperatures since the objective of the tests was restricted to the influence of the walking movements under calm conditions.
Five set points were selected: 10, 15, 20, 25 and 30°C, and the operative temperature within the test chamber varied between
11.9 and 29.6°C. The highest and lowest I
a
values obtained were equal to 0.87 and 0.71 clo, respectively, and the reduction in insulation due to walking ranged between
9.8 and 11.5%. The convective coefficients (h
conv
) for the whole body and for the different body segments were also determined for each step rate. In the case of the whole
body, for the standing static reference posture, the mean value of h
conv
was equal to 3.3 W/m2°C and a correlation [Nu = Nu(Gr)] for natural convection is also presented in good agreement with previous results. For the other postures, the values of
h
conv
were equal to 3.7, 3.9 and 4.2 W/m2°C, respectively for 20, 30 and 45 steps/min. 相似文献
85.
Fernandes AS Costa J Gaspar J Rueff J Cabral MF Cipriano M Castro M Oliveira NG 《Free radical research》2012,46(9):1157-1166
The unique redox and catalytic chemistry of Cu has justified the development of novel Cu complexes for different therapeutic uses including cancer therapy. In this work, four pyridine-containing aza-macrocyclic copper(II) complexes were prepared (CuL1-CuL4) varying in ring size and/or substituents and their superoxide scavenging activity evaluated. CuL3, the most active superoxide scavenger, was further studied as a modulator of the cytotoxicity of oxaliplatin in epithelial breast MCF10A cells and in MCF7 breast cancer cells. Our results show that CuL3 enhances the therapeutic window of oxaliplatin, by both protecting non-tumour cells and increasing its cytotoxic effect in breast carcinoma cells. CuL3 is thus a promising complex to be further studied and to be used as a lead compound for the optimization of novel chemotherapy sensitizers. 相似文献
86.
87.
88.
Kevers Claire Franck Thierry Strasser Reto J. Dommes Jacques Gaspar Thomas 《Plant Cell, Tissue and Organ Culture》2004,77(2):181-191
Hyperhydricity of micropropagated shoots, formerly called vitrification, undoubtedly results from growth and culture conditions, subjectively reputated as stressing factors: wounding, infiltration of soft culture medium, generally of a high ionic strength, rich in nitrogen and in growth regulators in a special balance, in a humid and gaseous confined atmosphere. Stress is (objectively) defined as a disruption of homeostasis resulting from a constraint escaping the usual flexibility of metabolism. It induces another temporary (reversible) or definitive (irreversible) thermodynamic physiological state. The state-change concept developed by Strasser (1988) and Strasser and Tsimilli-Michael (2001) is applicable to the phenomenon of hyperhydricity. An appraisal of the redox capacities of hyperhydrated shoots together with a study of some enzymic activities that catalyse pentose phosphate and glycolytic pathways has indeed shown that such shoots have evolved towards a temporary state of lower differentiation or a juvenile state with a sufficient activity to survive and to defend themselves. 相似文献
89.
M. Bouchet Th. Gaspar T. A. Thorpe 《In vitro cellular & developmental biology. Plant》1978,14(10):819-823
Summary A comparison of the soluble and cell-wall-bound isoperoxidases of normal auxin-requiring and auxin-independent (habituated)
tobacco callus revealed that normal tissues contained a higher level of isoperoxidases. There were also qualitative differences
in these isoperoxidases. Partially purified soluble and ionically bound isoperoxidases of normal callus likewise exhibited
higher auxin-oxidase activities. Normal tissues also were found to contain higher levels of auxin-oxidase inhibitors (auxin
protectors). Overall, however, the data indicate that there is a higher rate of auxin destruction in normal tobacco callus
than in habituated tissue. This presumably leads to insufficient endogenous auxin for growth.
This study was supported in part by grants to T.G. from the Center IRSIA d'Etude de la Reproduction végétale and the FRFC
Contract No. 2.9009. it Was carried out while T.A.T. was the holder of a senior Fellowship under the NATO senior Scientists
Program. 相似文献
90.