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101.
Reptilian transferrins: evolution of disulphide bridges and conservation of iron-binding center 总被引:1,自引:0,他引:1
Transferrins, found in invertebrates and vertebrates, form a physiologically important family of proteins playing a major role in iron acquisition and transport, defense against microbial pathogens, growth and differentiation. These proteins are bilobal in structure and each lobe is composed of two domains divided by a cleft harboring an iron atom. Vertebrate transferrins comprise of serotransferrins, lactoferrins and ovotransferrins. In mammals serotransferrins transport iron in physiological fluids and deliver it to cells, while lactoferrins scavenge iron, limiting its availability to invading microbes. In oviparous vertebrates there is only one transferrin gene, expressed either in the liver to be delivered to physiological fluids as serotransferrin, or in the oviduct with a final localization in egg white as ovotransferrin. Being products of one gene sero- and ovotransferrin are identical at the amino-acid sequence level but with different, cell specific glycosylation patterns. Our knowledge of the mechanisms of transferrin iron binding and release is based on sequence and structural data obtained for human serotransferrin and hen and duck ovotransferrins. No sequence information about other ovotransferrins was available until our recent publication of turkey, ostrich, and red-eared turtle (TtrF) ovotransferrin mRNA sequences [Ciuraszkiewicz, J., Olczak, M., Watorek, W., 2006. Isolation, cloning and sequencing of transferrins from red-eared turtle, African ostrich and turkey. Comp. Biochem. Physiol. 143 B, 301-310]. In the present paper, ten new reptilian mRNA transferrin sequences obtained from the Nile crocodile (NtrF), bearded dragon (BtrF), Cuban brown anole (AtrF), veiled and Mediterranean chameleons (VtrF and KtrF), sand lizard (StrF), leopard gecko (LtrF), Burmese python (PtrF), African house snake (HtrF), and grass snake (GtrF) are presented and analyzed. Nile crocodile and red-eared turtle transferrins have a disulphide bridge pattern identical to known bird homologues. A partially different disulphide bridge pattern was found in the Squamata (snakes and lizards). The possibility of a unique interdomain disulphide bridge was predicted for LtrF. Differences were found in iron-binding centers from those of previously known transferrins. Substitutions were found in the iron-chelating residues of StrF and TtrF and in the synergistic anion-binding residues of NtrF. In snakes, the transferrin (PtrF, HtrF and GtrF) N-lobe "dilysine trigger" occurring in all other known transferrins was not found, which indicates a different mechanism of iron release. 相似文献
102.
Lolium temulentum L. (Darnel ryegrass) has been proposed to be used as a model species for functional genomics studies in forage and turf grasses,
because it is a self-fertile, diploid species with a short life cycle and is closely related to other grasses. Embryogenic
calluses were induced from mature embryos of a double haploid line developed through anther culture. The calluses were broken
up into small pieces and used for Agrobacterium tumefaciens-mediated transformation. A. tumefaciens strain EHA105 harboring pCAMBIA1301 and pCAMBIA1305.2 vectors were used to infect embryogenic callus pieces. Hygromycin was
used as a selection agent in stable transformation experiments. Hygromycin resistant calluses were obtained after 4–6 weeks
of selection and transgenic plants were produced in 10–13 weeks after Agrobacterium-mediated transformation. Fertile plants were readily obtained after transferring the transgenics to the greenhouse. Transgenic
nature of the regenerated plants was demonstrated by Polymerase chain reaction (PCR), Southern hybridization analysis, and
GUS staining. Progeny analysis showed Mendelian inheritance of the transgenes. The transformation system provides a valuable
tool for functionality tests of candidate genes in forage and turf grasses. 相似文献
103.
D. HANNAH J. C. Z. WOINARSKI C. P. CATTERALL J. C. MCCOSKER N. Y. THURGATE R. J. FENSHAM 《Austral ecology》2007,32(3):261-276
Abstract This study reports on the responses of bird assemblages to woodland clearance, fragmentation and habitat disturbance in central Queensland Australia, a region exposed to very high rates of vegetation clearance over the last two to three decades. Many previous studies of clearing impacts have considered situations where there is a very sharp management contrast between uncleared lands and cleared areas: in this situation, the contrast is more muted, because both cleared lands and uncleared savanna woodlands are exposed to cattle grazing, invasion by the exotic grass Cenchrus ciliaris and similar fire management. Bird species richness (at the scale of a 1‐ha quadrat) was least in cleared areas (8.1 species), then regrowth areas (14.6 species), then uncleared woodlands (19.9 species). Richness at this scale was unrelated to woodland fragment size, connectivity or habitat condition; but declined significantly with increasing abundance of miners (interspecifically aggressive colonial honeyeaters). At whole of patch scale, richness increased with fragment size and decreased with abundance of miners. This study demonstrates complex responses of individual bird species to a regional management cocktail of disturbance elements. Of 71 individual bird species modelled for woodland fragment sites, the quadrat‐level abundance of 40 species was significantly related to at least one variable representing environmental position (across a rainfall gradient), fragment condition, fragment size and/or connectivity. This study suggests that priorities for conservation management include: cessation of broad‐scale clearing; increased protection for regrowth (particularly where this may bolster connectivity and/or size of woodland fragments); control of miners; maintenance of fallen woody debris in woodlands; increase in fire frequency; and reduction in the incidence of grazing and exotic pasture grass. 相似文献
104.
Puccinellia distans (Jacq.) Parl. is a common grass species found throughout the world. It can grow in arid and saline environments as well as under toxic boron concentrations. In this work we performed sequence related amplified polymorphism (SRAP) marker analysis on 20 wild P. distans genotypes to understand the genetic relationships among different genotypes and subspecies. We tested 119 SRAP primer pairs and found that 43 were polymorphic. The molecular data were then analyzed to determine the genetic relationships and population structure of the genotypes. We were able to trace the origin of genotypes that were carried to distant locations or gathered for research purposes. We also found that geographical distance between genotypes was not an important determinant of genetic relationships as even distantly located Puccinellia genotypes were closely related. As P. distans is known to be tolerant to salinity stress and toxic mineral concentrations, the findings of this work can be used as a starting point for selection of genotypes that should be tested under such conditions. 相似文献
105.
Using euhalophytes to understand salt tolerance and to develop saline agriculture: Suaeda salsa as a promising model 总被引:5,自引:0,他引:5
Background As important components in saline agriculture, halophytes can help to provide food for a growing world population. In addition to being potential crops in their own right, halophytes are also potential sources of salt-resistance genes that might help plant breeders and molecular biologists increase the salt tolerance of conventional crop plants. One especially promising halophyte is Suaeda salsa, a euhalophytic herb that occurs both on inland saline soils and in the intertidal zone. The species produces dimorphic seeds: black seeds are sensitive to salinity and remain dormant in light under high salt concentrations, while brown seeds can germinate under high salinity (e.g. 600 mm NaCl) regardless of light. Consequently, the species is useful for studying the mechanisms by which dimorphic seeds are adapted to saline environments. S. salsa has succulent leaves and is highly salt tolerant (e.g. its optimal NaCl concentration for growth is 200 mm). A series of S. salsa genes related to salt tolerance have been cloned and their functions tested: these include SsNHX1, SsHKT1, SsAPX, SsCAT1, SsP5CS and SsBADH. The species is economically important because its fresh branches have high value as a vegetable, and its seed oil is edible and rich in unsaturated fatty acids. Because it can remove salts and heavy metals from saline soils, S. salsa can also be used in the restoration of salinized or contaminated saline land.Scope Because of its economic and ecological value in saline agriculture, S. salsa is one of the most important halophytes in China. In this review, the value of S. salsa as a source of food, medicine and forage is discussed. Its uses in the restoration of salinized or contaminated land and as a source of salt-resistance genes are also considered. 相似文献
106.
Evolutionary divergence of β–expansin structure and function in grasses parallels emergence of distinctive primary cell wall traits 下载免费PDF全文
Javier Sampedro Mara Guttman Lian‐Chao Li Daniel J. Cosgrove 《The Plant journal : for cell and molecular biology》2015,81(1):108-120
Expansins are wall‐loosening proteins that promote the extension of primary cell walls without the hydrolysis of major structural components. Previously, proteins from the EXPA (α–expansin) family were found to loosen eudicot cell walls but to be less effective on grass cell walls, whereas the reverse pattern was found for EXPB (β–expansin) proteins obtained from grass pollen. To understand the evolutionary and structural bases for the selectivity of EXPB action, we assessed the extension (creep) response of cell walls from diverse monocot families to EXPA and EXPB treatments. Cell walls from Cyperaceae and Juncaceae (families closely related to grasses) displayed a typical grass response (‘β–response’). Walls from more distant monocots, including some species that share with grasses high levels of arabinoxylan, responded preferentially to α–expansins (‘α–response’), behaving in this regard like eudicots. An expansin with selective activity for grass cell walls was detected in Cyperaceae pollen, coinciding with the expression of genes from the divergent EXPB–I branch that includes grass pollen β–expansins. The evolutionary origin of this branch was located within Poales on the basis of phylogenetic analyses and its association with the ‘sigma’ whole‐genome duplication. Accelerated evolution in this branch has remodeled the protein surface in contact with the substrate, potentially for binding highly substituted arabinoxylan. We propose that the evolution of the divergent EXPB–I group made a fundamental change in the target and mechanism of wall loosening in the grass lineage possible, involving a new structural role for xylans and the expansins that target them. 相似文献
107.
Microsite determinants of variability in seedling and cutting establishment in tropical forest restoration plantations 下载免费PDF全文
David Douterlungne Bruce G. Ferguson Ilyas Siddique Lorena Soto‐Pinto Guillermo Jímenez‐Ferrer Mayra E. Gavito 《Restoration Ecology》2015,23(6):861-871
Plantations are frequently established on abandoned pasture lands to speed forest recovery. This strategy requires matching a tree species mix with the prevailing microenvironmental conditions. In four degraded pastures of the Mexican Lacandon rainforest, we planted 2,400 trees of 6 species (Guazuma ulmifolia, Inga vera, Ochroma pyramidale, Trichospermum mexicanum, Bursera simaruba, and Spondias mombin) to (1) test survival, initial growth, and establishment costs; (2) evaluate whether vegetative cuttings outperform direct seeding or transplants of nursery‐raised seedlings; (3) determine tree response to herbaceous dominance and soil compaction; and (4) scrutinize the results' consistency across sites and sampling scales of tree–microenvironment interactions (individual tree vs. averaged plot responses). After 2 years, overall survival and growth rates were high for 2 of 3 nursery‐raised species. Contrary to expectations, all seedlings outperformed the cuttings while direct seeding resulted in a cost‐effective option of intermediate efficacy. The impact of soil resistance to root penetration on tree biomass accumulation was species dependent while bulk density was not relevant. Soil‐covering, herbaceous vegetation accelerated growth in 3 of 4 tested species during the dry season. At this initial stage of forest restoration in abandoned pastures, Guazuma and Trichospermum were the most restoration‐effective species. Costs can be reduced by using direct‐seeding Inga and avoiding weeding during the dry season. Finally, our results demonstrate how species selection trials can be misleading due to site variations in tree response and to sampling scales that fail to account for small‐scale environmental heterogeneity. We recommend ways to improve the design of restoration trials. 相似文献
108.
Daniel Fitamo Seyoum Leta Gurja Belay Bekele Lemma Mats Olsson 《Soil & Sediment Contamination》2011,20(7):745-766
Irrigation with untreated wastewater from several industrial, commercial, and domestic discharges for decades caused accumulation of various heavy metals and metalloids in soils along the Akaki River in Ethiopia. Assessment of environmental threats and the potential phytoremediation of the soils require understanding of the toxic elements’ uptake and distribution in plant parts. Hence, a greenhouse study was performed to examine the phytoavailability and distribution of Cr, Ni, Co, Cu, Zn, Cd, Pb, Hg, Se, V, and As in forage grasses: Oat (Avena sativa), Rhodes grass (Chloris gayana), Setaria (Setaria sphacelata), and the legumes Alfalfa (Medicago sativa) and Desmodium (Desmodium unicinatum). The average contents of Cr, Ni, Co, Cu, Zn, Pb, Hg, Se, and V in the plants were generally higher than the background levels for forage grasses/legumes, and some of these elements were in the phytotoxic range. Root bioconcentration factor (BCF = root to soil concentration ratio) > 1 was observed for Cu (Oat, Rhodes, Desmodium, and Setaria: Fluvisol), Zn (Setaria: Fluvisol), Cd (Rhodes: Fluvisol; Setaria from both soils) and Hg (Oat and Alfalfa: Fluvisol). Alfalfa and Desmodium displayed translocation factor > 1 (TF = shoot to root concentration ratio) for most heavy metals. Most heavy metals/metalloids may pose a health threat to humans and stock via introduction to the food chain. The plant factors (species and plant part), soil factors (soil type, soil fractions, pH, and CEC), and their interactions significantly (p < 0.05) influenced plant heavy metal and metalloid levels. However, the role of plant part and species emerged as the most important on heavy metal uptake, translocation, sequestration, and ultimately transfer to the food chain. Accordingly, the uptake and distribution of heavy metals/metalloids in the plants reflect the potential environmental and health hazards attributable to the use of fodder grasses, legumes, and cultivation of vegetables in soils with polymetallic and metalloid contamination. 相似文献
109.
Cattle pastures established in areas previously covered by tropical rainforest can be abandoned in unproductive and degraded conditions. Transplanting native tree species to pastures is one common practice among rainforest restoration techniques, but several environmental barriers compromise transplant success. We assessed whether the presence of isolated trees and the removal of pasture grasses affect survival, growth, and allometry of transplanted saplings of the pioneer tree Trema micrantha (L.) Blume (Ulmaceae) into abandoned pastures in southeast Mexico. An isolated tree was selected in the center of each of four pasture sites of one hectare, and grass treatments were applied under the tree's canopy (0–10 m from the trunk) and in open pasture (15–48 m from the trunk). Grass removal treatments were control (grass present), cut with machete, herbicide application, and total grass removal with a gardening hoe. After 1 year, sapling survival was not different between the canopy and pasture areas (53%). Saplings showed higher survival probability (p < 0.05) in the hoe treatment (63 ± 9%) than in the control treatment (38 ± 9%). Height and crown cover growth rates were faster under the canopy of isolated trees compared with the open pasture. Saplings showed significantly greater crown area/height ratios under the canopy of isolated trees. Stressful environmental conditions restricted sapling growth in the open pasture. We conclude that complete removal of grasses and transplanting T. micrantha saplings in the vicinity of isolated trees can improve transplant success. 相似文献
110.
丛枝菌根真菌对百喜草的生理特性的影响 总被引:1,自引:0,他引:1
采用盆栽法研究了丛枝菌根(AM)真菌摩西球囊霉(Glomus mosseae)对水分胁迫条件下百喜草(Paspalum notatum)生长、渗透调节及抗氧化酶的影响。结果表明:接种AM真菌显著提高了百喜草的株高、地上部与根部鲜重、地上部P、K、Mn及根部P、Ca、Mn含量,明显降低了地上部Zn及根部Fe、B、Cu水平;随着干旱程度的加深,接种株的地上部相对含水量及叶绿素含量相对稳定且均显著高于未接种株,接种株地上部相对电导率、MDA含量均显著低于未接种株,接种株的地上部POD活性与脯氨酸含量均显著增加且均显著高于未接种株,AM侵染对SOD活性的影响较小。可见,接种AM真菌Glomus mosseae提高了植株体内保护酶活性(如POD)及渗透调节能力(如脯氨酸、P、K、Ca等渗透调节物含量的增加),从而显著增强了百喜草的抗旱性。 相似文献