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131.
Polydiacetylenes (PDAs), which possess unique properties that allow them to change color in response to environmental changes such as variations in pH, temperature, and molecular binding, have been widely investigated as signal transducers in biosensor applications. Most PDA-based sensors reported to date have been evaluated largely on the basis of their ability to detect purified samples, however, and their specificity has rarely been tested. In this study, novel PDAs fabricated on polyvinylidene fluoride (PVDF) strips by photoreaction of composite diacetylene self-assemblies were developed as biosensors, and nonspecific binding to off-target biomolecules was assessed. A mixed PDA surface containing biotin and ethanolamide bound the target, i.e., streptavidin, more specifically than did biotin alone. The optimized PDA biosensor exhibited approximately 2850-fold higher selectivity for streptavidin relative to bovine serum albumin controls. A PDA biosensor that was further prepared showed distinctive signals for the urine of diabetic patients compared to urine samples from healthy/non-diabetic person due to the concentration of microalbuminuria. To our knowledge, this is the first strip-type biosensor fabricated with PDAs and the first PDA-based biosensor that can effectively overcome the problem of nonspecific binding. 相似文献
132.
Deepika Sharma Rupam Kapoor Ashok K. Bhatnagar 《World journal of microbiology & biotechnology》2008,24(3):395-400
Curculigo orchioides Gaertn. (family Hypoxidaceae) is an endangered anticarcinogenic and aphrodisiac herb, native of India. This study reports
the effect of three arbuscular mycorrhizal (AM) fungal inocula on post-transplanting performance of ‘in vitro’ raised C. orchioides plantlets. The three AM fungal inocula consisted of two monospecific cultures of Glomus geosporum and G. microcarpum and one crude consortium of AM fungal spores isolated from rhizosphere soil of C. orchioides growing in natural habitat. Complete plantlets of C. orchioides were raised by direct organogenesis of leaf explants on half strength Murashige and Skoog’s medium devoid of any growth hormone.
C. orchioides plantlets responded significantly different to all three mycorrhizal treatments. Mycorrhization enhanced the survival rate
of C. orchioides plantlets to 100%. The inoculated plantlets fared significantly better than the uninoculated ones in terms of biomass production
and number of leaves and roots per plant. Mycorrhizal plantlets exhibited higher concentrations of photosynthetic pigments
as well as minerals P, Mg, Cu, Zn, Mn and Fe in both shoots and roots. Among the three inocula tested, plantlets inoculated
with the mixed consortium of AM fungi consistently performed better in terms of the parameters evaluated. The study suggests
use of mixed consortium of AM fungi over monospecific cultures for the sustainable cultivation and conservation of endangered
medicinal plant: Curculigo orchioides. 相似文献
133.
Surface tensiometry and vibrational sum-frequency spectroscopy were used to examine the structure and organization in phospholipid monolayers at the aqueous/vapor interface in the absence and in the presence of simple, charged surfactants. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was the phospholipid employed in these studies and surfactants included sodium dodecyl sulfate (SDS) and dodecyl trimethyl ammonium bromide (DTAB). DPPC spontaneously spreads on a pure water (pH = 5.5) surface to form monolayers as evidenced by an equilibrium spreading pressure (ESP) of 7.9 ± 2.3 mN/m and a clearly resolved vibrational spectrum. Low concentrations of surfactants inhibit the spreading of DPPC and result in significantly lower ESP values. Anionic and cationic surfactants at higher concentrations have opposite effects on monolayer organization; SDS creates well-organized monolayers while DTAB leads to poor organization of lipid molecules. Surface-specific vibrational spectra showed that high concentrations of charged surfactants (≥ 100 µM) lead to accumulation of net surface charges as evidenced by destructive and constructive interferences. Selectively deuterating surfactants results in changes in vibrational band intensities and phases enabling assignment of relative orientations of equivalent functional groups belonging to the lipid and surfactant. 相似文献
134.
David Posada 《Journal of molecular evolution》2001,52(5):434-444
Models of sequence evolution play an important role in molecular evolutionary studies. The use of inappropriate models of
evolution may bias the results of the analysis and lead to erroneous conclusions. Several procedures for selecting the best-fit
model of evolution for the data at hand have been proposed, like the likelihood ratio test (LRT) and the Akaike (AIC) and
Bayesian (BIC) information criteria. The relative performance of these model-selecting algorithms has not yet been studied
under a range of different model trees. In this study, the influence of branch length variation upon model selection is characterized.
This is done by simulating sequence alignments under a known model of nucleotide substitution, and recording how often this
true model is recovered by different model-fitting strategies. Results of this study agree with previous simulations and suggest
that model selection is reasonably accurate. However, different model selection methods showed distinct levels of accuracy.
Some LRT approaches showed better performance than the AIC or BIC information criteria. Within the LRTs, model selection is
affected by the complexity of the initial model selected for the comparisons, and only slightly by the order in which different
parameters are added to the model. A specific hierarchy of LRTs, which starts from a simple model of evolution, performed
overall better than other possible LRT hierarchies, or than the AIC or BIC.
Received: 2 October 2000 / Accepted: 4 January 2001 相似文献
135.
Power of the joint segregation analysis method for testing mixed major-gene and polygene inheritance models of quantitative traits 总被引:10,自引:0,他引:10
J. Wang D. W. Podlich M. Cooper I. H. DeLacy 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(5):804-816
Understanding the genetic architecture of quantitative traits can greatly assist the design of strategies for their manipulation
in plant-breeding programs. For a number of traits, genetic variation can be the result of segregation of a few major genes
and many polygenes (minor genes). The joint segregation analysis (JSA) is a maximum-likelihood approach for fitting segregation
models through the simultaneous use of phenotypic information from multiple generations. Our objective in this paper was to
use computer simulation to quantify the power of the JSA method for testing the mixed-inheritance model for quantitative traits
when it was applied to the six basic generations: both parents (P1 and P2), F1, F2, and both backcross generations (B1 and B2) derived from crossing the F1 to each parent. A total of 1968 genetic model-experiment scenarios were considered in the simulation study to quantify the
power of the method. Factors that interacted to influence the power of the JSA method to correctly detect genetic models were:
(1) whether there were one or two major genes in combination with polygenes, (2) the heritability of the major genes and polygenes,
(3) the level of dispersion of the major genes and polygenes between the two parents, and (4) the number of individuals examined
in each generation (population size). The greatest levels of power were observed for the genetic models defined with simple
inheritance; e.g., the power was greater than 90% for the one major gene model, regardless of the population size and major-gene
heritability. Lower levels of power were observed for the genetic models with complex inheritance (major genes and polygenes),
low heritability, small population sizes and a large dispersion of favourable genes among the two parents; e.g., the power
was less than 5% for the two major-gene model with a heritability value of 0.3 and population sizes of 100 individuals. The
JSA methodology was then applied to a previously studied sorghum data-set to investigate the genetic control of the putative
drought resistance-trait osmotic adjustment in three crosses. The previous study concluded that there were two major genes
segregating for osmotic adjustment in the three crosses. Application of the JSA method resulted in a change in the proposed
genetic model. The presence of the two major genes was confirmed with the addition of an unspecified number of polygenes.
Received: 18 August 2000 / Accepted: 9 March 2001 相似文献
136.
V. K. Srivastava G. D. Mishra A. Chaturvedi 《Biometrical journal. Biometrische Zeitschrift》1981,23(1):1-8
For a linear regression model with random coefficients, this paper considers the estimation of the mean of coefficient vector which, in turn, involves the estimation of variances of random coefficients. The conventional estimation methods for it sometimes provides negative estimates. In order to circumvent this kind of difficulty, a proposal is forwarded and is examined in the light of existing ones. 相似文献
137.
Metal clusters are ubiquitously used as electron-transfer (ET) agents in biology. Their presence raises the question of how
the polynuclear nature of these systems influences ET. In an earlier study, a theoretical model was formulated to describe
ET from a mixed-valence dimer to a diamagnetic acceptor. In the present work, this approach is generalized to analyze the
effect of valence delocalization on the rate of ET in a larger class of donor–acceptor systems. Our results indicate that
the effect of valence delocalization on ET rate depends on whether the mixed-valence (MV) state occurs in the initial or final
state of the reaction and on the reaction regime (normal vs inverted) as defined by Marcus. The analysis provides a possible
correlation between the rate constant for ET from CuA to heme a and the difference in the valence delocalization of the CuA centers in wild-type and mutant species of cytochrome c oxidase. We have analyzed the dependence of the electron flow through extended circuits containing MV clusters on valence
delocalization. A significant effect was found in the fast ET regime where the capacity of the circuit to conduct electrons
is optimally used. The possibility of controlling electron conduction by tuning valence delocalization is briefly addressed.
Received: 16 July 1997 / Accepted: 26 November 1997 相似文献
138.
A new mixed-valence copper coordination polymer with copper-copper metal bonds in a two-dimensional network was generated from an in situ oxidation reaction route under hydrothermal conditions. The synthesis of this coordination polymer demonstrated that the novel compounds that may not be accessible using the known methods could be synthesized via an oxidation reaction route. The reaction conditions are mild enough to keep the building blocks intact during the oxidation and self-assembly process under hydrothermal conditions. 相似文献
139.
140.
BackgroundCancer screening is below targets in Ontario, Canada. Our objective was to identify and quantify the barriers and facilitators for breast, cervical and colorectal cancer screening for under and never screened (UNS) residents living in Ontario between 2011 and 2013.MethodsWe used a multi-phased mixed methods study design. Results from thematic analysis of focus group discussions with health care providers and UNS community members were used to develop an on-line, province-wide, cross-sectional survey to estimate the prevalence of barriers and facilitators for the provincial population. Adjusted prevalence odds ratios and 95% confidence intervals were estimated for UNS compared to regularly screened participants using logistic regression.ResultsFour focus groups were held with health service providers and sixteen with UNS community members. Top barriers and facilitators themed around provider-patient communication, fear and embarrassment, history of physical or sexual abuse, social determinants of health (including low literacy, lack of awareness, and health insurance), symptoms appearing, and family and friends. 3075 participants completed the online survey. Compared to regularly screened participants, UNS had significantly higher odds of reporting: no regular health care provider; not feeling comfortable talking about screening; or the Doctor or Nurse Practitioner not suggesting screening. UNS also had significantly higher odds of reporting the facilitators: the test being less scary/painful or uncomfortable; friend/family insisting on getting screened; starting to have symptoms; or an easier test that could be done at home.ConclusionsInterventions addressing fear through individual, interpersonal and structural facilitators may increase cancer screening. 相似文献