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61.
Helicoverpa armigera Hubner Lepidoptera: Noctuidae is one of the most serious insect pests in the Old World. In India, it causes substantial losses to legume, fibre, cereal oilseed and vegetable crops. This paper reviews the literature on the biology, ecology, efficacy, rearing and augmentation of endemic parasitoids and predators, as well as exotic parasitoids introduced and released in India. It also provides updated lists of H. armigera natural enemies native to India. In addition, reports of augmentative releases of Trichogramma spp., the most extensively studied natural enemy of H. armigera are summarized. 相似文献
62.
Recombinant human pigment epithelium-derived factor (PEDF): characterization of PEDF overexpressed and secreted by eukaryotic cells. 总被引:1,自引:0,他引:1
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E. Stratikos E. Alberdi P. G. Gettins S. P. Becerra 《Protein science : a publication of the Protein Society》1996,5(12):2575-2582
Pigment epithelium-derived factor (PEDF) is a serpin found in the interphotoreceptor matrix of the eye, which, although not a proteinase inhibitor, possesses a number of important biological properties, including promotion of neurite outgrowth and differential expression in quiescent versus senescent states of certain cell types. The low amounts present in the eye, together with the impracticality of using the eye as a source for isolation of the human protein, make it important to establish a system for overexpression of the recombinant protein for biochemical and biological studies. We describe here the expression and secretion of full-length glycosylated human recombinant PEDF at high levels (> 20 micrograms/ mL) into the growth medium of baby hamster kidney cells and characterization of the purified rPEDF by circular dichroism and fluorescence spectroscopies and neurite outgrowth assay. By these assays, the recombinant protein behaves as expected for a correctly folded full-length human PEDF. The availability of milligram amounts of PEDF has permitted quantitation of its heparin binding properties and of the effect of reactive center cleavage on the stability of PEDF towards thermal and guanidine hydrochloride denaturation. 相似文献
63.
Marie-France Dietsch 《Vegetation History and Archaeobotany》1996,5(1-2):89-97
Recent rescue excavations at Bercy (Paris), a site on the alluvial plain of the Seine valley, yielded plant remains which
are associated with the recent occupation phase dating from the middle Neolithic II (Chasséen), when a village was established
on the former channel of the river Seine. Various contexts (the channel, the flat lower part of the bank, and several archaeological
features) have been studied and 84 taxa have been identified. Cultivated plants are represented by Triticum aestivum/durum, T. dicoccum, T. monococcum and Hordeum vulgare. Among the wild plants with potentially edible fruits or seeds, only very few satisfy the various criteria for association
with human activities: Corylus avellana, Vitis sylvestris, Cornus sanguinea, Quercus sp. and Prunus spinosa of which carbonized fruits were also present, were found in archaeological features and were very abundant. Though not found
in archaeological features, we consider that Crataegus monogyna (carbonized and well represented) and Rubus spp. (especially abundant) were not deposited there naturally and had also been intentionally collected. Finally, it is suggested
that the allochthonous (varied) origin of these taxa is the reason why there are no concentrations of their fruits in the
channel. The exploitation of wild seeds and fruits appears to have been very selective. All other wild taxa can be attributed
to natural deposition. 相似文献
64.
Evidence for plant exploitation and vegetation history from three Early Neolithic pre-pottery sites on the Euphrates (Syria) 总被引:3,自引:0,他引:3
George Willcox 《Vegetation History and Archaeobotany》1996,5(1-2):143-152
Archaeobotanical results based on a limited number of samples from three aceramic sites dating from 9800 to 7800 B.P., which
are under excavation in the valley of the Middle Euphrates, are discussed. The finds are presented simply by presence, and
are compared to the contemporary vegetation and finds from similar sites. Carbonised plant remains recovered by flotation
from levels dated to between 9800 and 9200 B.P. (Dja'de and Jerf al Ahmar) indicate that wild cereals (einkorn wheat, rye
and barley) and pulses (lentils, pea and bitter vetch) were exploited. Other plants such as wild grasses, Pistacia, wild almond and oak, suggest that the local vegetation provided a rich diversity of resources. A study of possible weed
taxa is being carried out in order to see whether this assemblage could be used to identify the cultivation of morphologically
wild cereals for this period. Ninth millennium B.P. levels at Halula see the appearance of domestic crops such as emmer, naked
wheat and barley, but wild-type cereals persist. The cultivars appear to have been introduced from elsewhere and later ninth
millennium B.P. species include olive and flax. Ash, vine, maple, plane, alder and elm from the gallery forest, wild rye,
wild einkorn, deciduous oak, wild almond, Pistacia, and Pyrus, from the hinterland, indicate cooler conditions. 相似文献
65.
Paul D. Sniegowski 《Journal of molecular evolution》1995,40(1):94-101
Several recent reports have claimed that adaptive mutants in bacteria and yeast are induced by selective conditions. The results of these reports suggest that mutants can arise nonrandomly with respect to fitness, contrary to what has been widely accepted. In several cases that have received careful experimental reexamination, however, the detection of seemingly nonrandom mutation has been explained as an experimental artifact. In the remaining cases, there is no evidence to suggest that cells have the capacity to direct or choose which genetic variants will arise. Instead, current models propose processes by which genetic variants persist as mutations only if they enable cell growth and DNA replication. Most of these models are apparently contradicted by experimental data. One model, the hypermutable state model, has recently received limited circumstantial support. However, in this model the origin of adaptive mutants is random; the apparent nonrandomness of mutation is merely a consequence of natural selection. The critical distinction between the origin of genetic variation (mutation) and the possible consequence of that variation (selection) has been neglected by proponents of directed mutation. 相似文献
66.
Rhodopsinlike opsins constitute a distinct phylogenetic group (Yokoyama 1994, Mol. Biol. Evol. 11:32–39). This RH2 group includes the green-sensitive opsins in chicken and goldfish and the blue-sensitive opsin in a nocturnal lizard gecko. In the present study, we isolated and sequenced the genomic DNA clones for the RH2 opsin gene, rh2
Ac
, of the diurnal lizard Anolis carolinensis. This single-copy gene spans 18.3 kb from start to stop codons, making it the longest opsin gene known in vertebrates. Phylogenetic analysis strongly suggests that rh2
Ac
is more closely related to the chicken green opsin gene than to the gecko blue opsin gene. This gene tree differs from the organismal tree, where the two lizard species should be most closely related, implying that rh2
Ac
and the gecko blue-sensitive opsin genes have been derived from duplicate ancestral genes.Correspondence to: S. Yukiyama 相似文献
67.
Eiji Nitasaka Tsuneyuki Yamazaki M. M. Green 《Molecular & general genetics : MGG》1995,247(2):164-168
A large proportion of spontaneous mutations inDrosophila melanogaster strains of laboratory origin are associated with insertions of mobile DNA elements. As a first step toward determining whether spontaneous laboratory mutations are predictive for mutational events occurring in the wild, recessivebrown (bw) eye color mutants were isolated. By inbreeding the progeny of wild-caughtDrosophila melanogaster females,bw mutations were isolated from seven separate geographic sites distributed among Japan, California, Siberia and Hungary. Among a total of 14 mutations studied, no case of transposon mutagenesis was found. At least 4 mutations are associated with small deletions in thebw gene. The remainder are inseparable from wild-typebw by Southern analysis and are presumed to be basepair changes or very small indels. Although only two spontaneousbw mutants of laboratory origin have been analyzed molecularly, one is a mobile element insertion. 相似文献
68.
M. R. Evans A. L. R. Thomas 《Proceedings. Biological sciences / The Royal Society》1997,264(1379):211-217
Studies of the evolution of elaborate ornaments have concentrated on their role in increasing attractiveness to mates. The classic examples of such sexually selected structures are the elongated tails of some bird species. Elongated tails can be divided into three categories: graduated tails, pin tails and streamers. There seems to be little debate about whether graduated and pin tails are ornaments; i.e. costly signals used in mate choice. However, in the case of streamers there is considerable discussion about their function. It has been suggested that tail streamers could be (i) entirely naturally selected, (ii) entirely sexually selected, (iii) partly naturally and partly sexually selected. The prime example of a species with tail streamers is the swallow (Hirundo rustica) in which both sexes have tail streamers. In this paper we discuss the aerodynamic consequences of different types of manipulation of the streamer and/or outer tail feather. We make qualitative predictions about the aerodynamic performance of swallows with manipulated tail streamers; these predictions differ depending on whether streamers have a naturally or sexually selected function. We demonstrate that these hypotheses can only be separated if tail streamers are shortened and changes in aerodynamic performance measured during turning flight. 相似文献
69.
Ruth Meléndez Enrique Meléndez-Hevia Marta Cascante 《Journal of molecular evolution》1997,45(4):446-455
Optimization of molecular design in cellular metabolism is a necessary condition for guaranteeing a good structure–function
relationship. We have studied this feature in the design of glycogen by means of the mathematical model previously presented
that describes glycogen structure and its optimization function [Meléndez-Hevia et al. (1993), Biochem J 295: 477–483]. Our
results demonstrate that the structure of cellular glycogen is in good agreement with these principles. Because the stored
glucose in glycogen must be ready to be used at any phase of its synthesis or degradation, the full optimization of glycogen
structure must also imply the optimization of every intermediate stage in its formation. This case can be viewed as a molecular
instance of the eye problem, a classical paradigm of natural selection which states that every step in the evolutionary formation of a functional structure
must be functional. The glycogen molecule has a highly optimized structure for its metabolic function, but the optimization
of the full molecule has meaning and can be understood only by taking into account the optimization of each intermediate stage
in its formation.
Received: 23 October 1996 / Accepted: 21 April 1997 相似文献
70.
Shneior Lifson 《Journal of molecular evolution》1997,44(1):1-8
Theories of the origin of life have proposed hypotheses to link inanimate to animate matter. The theory proposed here derived
the crucial stages in the origin of animate matter directly from the basic properties of inanimate matter. It asked what were
the general characteristics of the link, rather than what might have been its chemical details. Life and its origin are shown to be one continuous physicochemical process of replication, random variation, and natural
selection. Since life exists here and now, animate properties must have been initiated in the past somewhere. According to
the theory, life originated from an as yet unknown elementary autocatalyst which occurred spontaneously, then replicated autocatalytically. As it multiplied to macroscopic abundance, its replicas
gradually exhausted their reactants. Random chemical drift initiated diversity among autocatalysts. Diversity led to competition. Competition and depletion of reactants slowed down the rates of net replication
of the autocatalysts. Some reached negative rates and became extinct, while those which stayed positive ``survived.' Thus
chemical natural selection appeared, the first step in the transition from inanimate to animate matter. It initiated the first animate property, fitness, i.e., the capacity to adapt to the environment and to survive. As the environment was depleted of reactants, it was enriched with sequels—namely, with decomposition products and all other products which accompany autocatalysis. The changing environment exerted
a selective pressure on autocatalysts to replace dwindling reactants by accumulating sequels. Sequels that were incorporated
into the autocatalytic process became internal components of complex autocatalytic systems. Primitive forms of metabolism and organization were thus initiated. They evolved further by the same mechanism to ever higher levels of complexity, such
as homochirality (handedness) and membranal enclosure. Subsequent evolution by the same mechanism generated cellular metabolism,
cell division, information carriers, and a genetic code. Theories of self-organization without natural selection are refuted.
Received: 29 March 1996 / Accepted: 30 May 1996 相似文献