全文获取类型
收费全文 | 149篇 |
免费 | 16篇 |
国内免费 | 1篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1958年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 29 毫秒
1.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
2.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
3.
M. Jeuken S.J. 《Acta biotheoretica》1958,13(1):29-46
Summary In this paper we intend to propose a definition of function in biology. First we delimitated the problem and pointed out that a definition must not be related to hypotheses such as the causal connexion between form and function, phylogenetics or evolution, but that only the existence of functions is to be considered. The elements to be expressed in the definition are: the relation of function to form, the dynamic character, the integration into the activity of the total organism, the possibility of latent functions and the fact that in the case of mechanical functions the function is not itself action, but directly related to it. So we proposed the following definition: A biological function is a property of a definite part of the total organism, marked by a certain form or structure, which property is actual or potential activity itself or directly related to activity, and by which the development and the maintenance of the organism as a whole is enabled to proceed in a harmonious way.We finished with some theoretical remarks in which the logical dependence of the function on the form is brought forward. Therefore form and function are not an example of the principle of complementarity, as is stated byMeyer-Abich. Attention is also given to a former paper byBarge on the form-function problem. This paper served as the starting point for the present discussion.
Zusammenfassung Wir haben in dieser Abhandlung versucht eine Definition der biologischen Funktion zu geben. Zunächst beschränkten wir uns darauf, darzulegen, dass man bei einer Definition nicht auf Hypothesen hinweisen soll, wie z.B. auf den Kausalzusammenhang zwischen Form und Funktion, Phylogenese oder Evolution. Es soll lediglich des Bestehen von Funktionen berücksichtigt werden.Folgende Elemente müssen in der Definition zum Ausdruck kommen: die Beziehung der Funktion zur Form, der dynamische Charakter, die Integrierung in die Aktivität des Organismus als Ganzes, die Möglichkeit latenter Funktionen und die Tatsache, dass die Funktion im Falle einer mechanischen Funktion selbst nicht Aktivität ist, jedoch in direkter Beziehung zu ihr steht.Wir haben daher die folgende Definition vorgeschlagen: Eine biologische Funktion ist die Eigenschaft eines bestimmten Teiles des Organismus als Ganzes der eine bestimmte Form oder Struktur besitzt: diese Eigenschaft ist ihrerseits wirkliche oder mögliche Aktivität oder aber steht in einem direkten Verhältnis zu ihr; sie ermöglicht die harmonische Entwicklung und Erhaltung des Organismus als Ganzes.Zum Abschluss machten wir einige theoretische Bemerkungen in denen wir die logische Abhängigkeit der Funktion von der Form darlegten. Form und Funktion sind demzufolge kein Musterbeispiel für das Komplementaritäts-prinzip so wie es vonMeyer-Abich angeführt wird. Wir haben uns auch mit einer früheren Abhandlung über das Form-Funktion-Problem vonBarge befasst. Sie diente uns als Ausgangspunkt für die gegenwärtige Erörterung.
Résumé Dans cette étude nous avons l'intention de proposer une définition de fonction en biologie. D'abord nous avons délimité le problème et faisons remarquer qu'une définition ne doit pas être mise en rapport avec des hypothèses comme la relation causale entre forme et fonction, phylogénèses ou évolution, mais que seule l'existence de fonctions doît être considerée. Les éléments qui doivent être exprimés sont: la relation de fonction à la forme, le caractère dynamique, l'intégration dans l'activité de l'organisme total, la possibilité de fonctions latentes et le fait qu'au cas de fonctions méchaniques le fonction même n'est pas action, mais y est immédiatement relative. Ainsi nous proposons la définition suivante: Une fonction biologique est une propriété d'une partie définie de l'organisme total, marquée par une certaine forme ou structure, laquelle propriété est activité actuelle ou potentielle elle-même, ou bien directement relative à l'activité et par laquelle le développement et le maintien de l'organisme total est mis à même d'avancer harmonieusement.Nous avons fini en faisant quelques remarques théoriques, où nous avons exposé que la fonction dépend logiquement de la forme. C'est pourquoi forme et fonction ne sont pas un exemple du principe de complémentement comme cela a été prétendu parMeyer-Abich. Nous avons également fait attention à une étude antérieure deBarge touchant le problème forme-fonction. Cette étude a servi comme point de départ à la discussion présente.相似文献
4.
Schistosomiasis vector snails are subjected to extreme seasonal changes, particularly in ephemeral rivers and lentic waterbodies. In the tropics, aestivation is one of the adaptive strategies for survival and is used by snails in times of extremely high temperatures and desiccation. Aestivation therefore plays an important role in maintaining the transmission of schistosomiasis. This review assesses the possible impacts of climate change on the temporal and spatial distribution of schistosomiasis-transmitting snails with special emphasis on aestivation, and discusses the effect of schistosome infection on aestivation ability. The impacts of parasite development on snails, as well as physiological changes, are discussed with reference to schistosomiasis transmission. This review shows that schistosome-infected snails have lower survival rates during aestivation, and that those that survive manage to get rid of the infection. In general, snail aestivation ability is poor and survival chances diminish with time. Longer dry periods result in fewer, as well as uninfected, snails. However, the ability of the surviving snails to repopulate the habitats is high. 相似文献
5.
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase
下载免费PDF全文
![点击此处可从《EMBO reports》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sharon C Mithoe Christina Ludwig Michiel JC Pel Mara Cucinotta Alberto Casartelli Malick Mbengue Jan Sklenar Paul Derbyshire Silke Robatzek Corné MJ Pieterse Ruedi Aebersold Frank LH Menke 《EMBO reports》2016,17(3):441-454
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex. 相似文献
6.
Jeuken LJ 《Biochimica et biophysica acta》2003,1604(2):67-76
Protein-protein electron transfer (ET) plays an essential role in all redox chains. Earlier studies which used cross-linking and increased solution viscosity indicated that the rate of many ET reactions is limited (i.e., gated) by conformational reorientations at the surface interface. These results are later supported by structural studies using NMR and molecular modelling. New insights into conformational gating have also come from electrochemical experiments in which proteins are noncovalently adsorbed on the electrode surface. These systems have the advantage that it is relatively easy to vary systematically the driving force and electronic coupling. In this review we summarize the current knowledge obtained from these electrochemical experiments and compare it with some of the results obtained for protein-protein ET. 相似文献
7.
Battistuzzi G Bellei M Borsari M Canters GW de Waal E Jeuken LJ Ranieri A Sola M 《Biochemistry》2003,42(30):9214-9220
The reduction thermodynamics (Delta H degrees '(rc) and Delta S degrees '(rc)) for native Paracoccus versutus amicyanin, for Alcaligenes faecalis S-6 pseudoazurin, and for the G45P, M64E, and K27C variants of Pseudomonas aeruginosa azurin were measured electrochemically. Comparison with the data available for other native and mutated blue copper proteins indicates that the features of metal coordination and the electrostatic potential due to the protein matrix and the solvent control the reduction enthalpy in a straightforward way. However, the effects on the reduction potential are rather unpredictable owing to the entropic contribution to E degrees ', which is mainly determined by solvent reorganization effects. Analysis of all the Delta H degrees '(rc) and Delta S degrees '(rc) values available for this protein class indicates that enthalpy-entropy compensation occurs in the reduction thermodynamics of wt cupredoxins from different sources, as well as for mutants of the same species. The findings indicate that the reduction enthalpies and entropies for these species are strongly affected by reduction-induced reorganization of solvent molecules within the solvation sphere of the protein. The absence of a perfect enthalpy-entropy compensation is due to the fact that while the differences between reduction entropies are dominated by solvent reorganization effects, those between reduction enthalpies are significantly controlled by intrinsic molecular factors related to the selective stabilization of the reduced form by coordination features of the copper site and electrostatic effects at the interface with the protein matrix. 相似文献
8.
1-Thio-beta-D-galactofuranosides: synthesis and evaluation as beta-D- galactofuranosidase inhibitors
Marino C; Marino K; Miletti L; Manso Alves MJ; Colli W; de Lederkremer RM 《Glycobiology》1998,8(9):901-904
Beta-D-galactofuranosidase is a good chemotherapeutic target for the design
of inhibitors, since beta-D-galactofuranose is a constituent of important
parasite glycoconjugates but is not present in the host mammals. With this
aim, we have synthesized for the first time alkyl, benzyl and aryl
1-thio-beta-D-galactofuranosides by condensation of
penta-O-benzoyl-alpha,beta-D-galactofuranose with the corresponding thiols,
in the presence of SnCl4as catalyst. The complete chemical and
spectroscopical characterization of these compounds showed that the
reaction was stereoselective. Debenzoylation with sodium methoxide afforded
the beta-S-galactofuranosides in high yield. The thioglycosides were tested
as inhibitors of the beta-D- galactofuranosidase of Penicillium fellutanum,
using for the first time 4-nitrophenyl-beta-D-galactofuranoside as
chromogenic substrate. The 4- aminophenyl-1-thio-beta-D-galactofuranoside,
obtained by catalytic hydrogenation of the nitrophenyl derivative, was the
best inhibitor being then an adequate ligand for the preparation of an
affinity phase aimed at the isolation of beta-d-galactofuranosidases from
different sources. Also the inhibitory activity of d-galactono-1, 4-lactone
was shown.
相似文献
9.
M Alonso N Alonso Rodriguez C Garzelli M Martínez Lirola M Herranz S Samper MJ Ruiz Serrano E Bouza D García de Viedma 《BMC microbiology》2010,10(1):151
Background
The Beijing lineage of Mycobacterium tuberculosis is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases. 相似文献10.
Jason A Roberts Michael S Roberts Andrew Semark Andrew A Udy Carl MJ Kirkpatrick David L Paterson Matthew J Roberts Peter Kruger Jeffrey Lipman 《BMC anesthesiology》2011,11(1):1-7