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941.
  1. Freshwater ecosystems represent less than 0.01% of Earth's surface water but proportionately encompass the most species-rich environment on the planet, including nearly one-third of all vertebrate species. Even though inland continental waters are widely regarded as highly endangered ecosystems, their species assemblages are mostly ignored in conservation plans, largely because spatial patterns of freshwater species remain poorly understood. This is particularly severe throughout the Neotropics, most notably in the Amazon superbasin, where the sheer biotic diversity is coupled with a severe lack of biodiversity knowledge at several levels.
  2. Spatial patterns of Neotropical freshwater fishes focusing mainly on the Amazon superbasin were investigated. First, Endemic Amazonian Fish Areas (EAFAs) representing central units for the conservation of continental fishes were delimited. Interpolated maps were then analysed using alternative methodologies to delimit spatial patterns of diversity and endemicity across the Amazon superbasin. Several biogeographical analyses used a comprehensive dataset of species and geographical coordinates of Amazonian fishes.
  3. The results reveal well-defined spatial patterns of species richness and endemicity in the Amazonian fish fauna, showing that most protected areas are concentrated in a single bioregion (Amazon lowlands). Those areas are incongruent and insufficient to protect endemic and threatened species, which are mostly distributed in upland regions.
  4. Effective conservation of the Amazonian fish fauna should include EAFAs within protected areas, especially those undergoing deforestation and hydropower development pressure and containing a high concentration of threatened species.
  5. The following EAFAs should be considered as conservation priorities: Upper Araguaia, Upper Tocantins, Lower Teles Pires/Serra do Cachimbo, Chapada dos Parecis and Upper Marañon. These regions should be urgently protected to avert the loss of important trophic relationships and unique elements of the Amazonian fish fauna.
  相似文献   
942.
  1. Freshwater ecosystems, providing valuable goods and services to humans, have been subjected to multiple human impacts, among which climate change plays a central role in threats to species. It is expected that protected areas, the cornerstone of biodiversity conservation efforts, will assume a decisive role in protecting freshwater species from the impacts of climate change.
  2. This study assessed the effects of climate change on migratory fish of the second largest neotropical river basin, evaluating the effectiveness of protected areas in safeguarding fish species, and hence the ecological functions that they perform and the ecosystem resources that they provide. The present range of 23 migratory fish of economic interest in the Paraná–Paraguay basin was estimated and the responses to future climatic shifts projected to the middle and end of the 21st century were examined, quantifying predictive uncertainties.
  3. Changes and losses of climatically suitable areas will trigger severe contractions in range, with the greatest impact on the most valuable species in commercial fishing, where range losses are likely to surpass 65% in the future. The main channel of the Upper Paraná River and tributaries of its left margin are projected to serve as climatic refuges for many species, and such regions are not affected by high predictive uncertainty. The results revealed that protected areas do not sufficiently protect migratory fish at present, and that they will continue to offer negligible protection in the face of climate change.
  4. This study alerts decision makers to the potential damage to inland fishery resources from climate change and provides useful information to guide conservation strategies spatially. We advocate that the creation of new protected areas and the redesign of the existing network to encompass regions that maximize current and future occupancy of migratory fish are crucial to conserve the valuable ecological, societal, and economic benefits that they provide.
  相似文献   
943.
The study of more than 700 charcoals from the Vaccaean settlement of Pintia (Padilla del Duero, Valladolid) provides new local and detailed data about the Iron Age II forest composition in Continental-Mediterranean inland Spain. Pinus gr. sylvestris/nigra (from which an unexpectedly high number of charcoals were identified), together with Mediterranean pines (also highly represented), Juniperus L. and evergreen and deciduous Quercus, were the main taxa living in the area, revealing two different marked biogeographical elements in the late-Holocene landscapes of the Duero basin: Mediterranean and Eurosiberian. On one hand, the results shed new light on the assessment of the origin of Mediterranean pinewoods in the area. On the other hand, the charcoal assemblage of Pintia reveals a more important presence of the current Mediterranean highland pines in the lowlands of the Central Iberian Peninsula in the late-Holocene suggesting the existence of interglacial refugia. Finally, this work highlights palaeoecological studies as valuable tools to support decisions on forest management related to conservation and restoration of our natural heritage.  相似文献   
944.

Background  

This work analyzes the effect of social isolation (a mild stressor) on the 24-h variation of pituitary-testicular function in young Wistar rats, assessed by measuring circulating levels of prolactin, FSH, LH and testosterone.  相似文献   
945.
Gross inequities in disease burden between developed and developing countries are now the subject of intense global attention. Public and private donors have marshaled resources and created organizational structures to accelerate the development of new health products and to procure and distribute drugs and vaccines for the poor. Despite these encouraging efforts directed primarily from and funded by industrialized countries, sufficiency and sustainability remain enormous challenges because of the sheer magnitude of the problem. Here we highlight a complementary and increasingly important means to improve health equity: the growing ability of some developing countries to undertake health innovation.  相似文献   
946.
An outbreak of paralytic poliomyelitis occurred in the Dominican Republic (13 confirmed cases) and Haiti (8 confirmed cases, including 2 fatal cases) during 2000-2001. All but one of the patients were either unvaccinated or incompletely vaccinated children, and cases occurred in communities with very low (7 to 40%) rates of coverage with oral poliovirus vaccine (OPV). The outbreak was associated with the circulation of a derivative of the type 1 OPV strain, probably originating from a single OPV dose given in 1998-1999. The vaccine-derived poliovirus associated with the outbreak had biological properties indistinguishable from those of wild poliovirus.  相似文献   
947.
Commercial micropropagation of plants is enhanced with the use of liquid media cultures; however the presence of hyperhydricity is commonly observed in cultures of the succulent plant Agave tequilana Weber cultivar azul, this phenomenon persists even with the use of temporary immersion systems (TIS). Thin cell suspension layer technology is proposed to solve this problem. This technology fuses the advantages of a liquid culture made through cellular dissociation, and the use of solid medium for somatic embryogenesis expression of the species. The technology was evaluated by means of two experiments in order to know the influence of gelling agent phytagel®, and of sucrose concentrations through interaction with three cellular suspension densities. It was clear that concentrations of phytagel at 6, 8, 10 or 12 g l?1 are not significant for embryoid expression of A. tequilana. On the other hand, sucrose at 30 and 60 g l?1 have statistically superior values than concentration of 120 g l?1. A larger cellular density (161 × 103 cells ml?1) gave a statistical difference in number of embryoids. The advantages of thin cell suspension layer were remarkable: it encouraged complete expression of embryoids without transfer to extra media cultures, and a higher number of generated embryoid was obtained. Absence of hyperhydricity was observed in all regenerants.  相似文献   
948.
Two methods have been tested in order to produce large quantities of Ecteinascidia turbinata for the extraction of anti-tumoral substances. With the first method, the capacity of generating biomass from settlement of larvae in a natural environment was estimated. The second method consisted of fragmenting colonies into small pieces, which were transplanted onto plastic screen where partial periodic collections of the colony could be carried out. For the first method, two different artificial substrates for settlement of larvae were studied: lines composed of hanging strips of wood, and plastic cords. The average production per unit of surface was significantly different between the two artificial substrates ( P < 0.005) (4.25 kg/M2 on the wooden strips after 75 days versus 1.39 kg/m2 on the plastic cords after 80 d). The transplant experiment showed a 93% survival of the colony 26 d after the colonies were transplanted and settled, and 96.48 kg of average biomass were collected, indicating a 235% increase in biomass. This system permits stolonial regrowth of the biomass fixed on the surface, without new transplants or settlements being needed, so that a continuous production can be maintained. The fragmentation of the colonies stimulate genet growth rates through the production of small daughter colonies which individually have higher relative growth rates than large colonies and, therefore, collectively have higher absolute growth rates than a large colony of similar biomass. The production of E. turbinata using a combination of the two methods is an example of successful production of metabolites from marine organisms while protecting natural populations.  相似文献   
949.
Tomato severe rugose virus (ToSRV) is the most important begomovirus transmitted and spread by the whitefly Bemisia tabaci in tomato crops in Brazil. Cultural practices are being adopted, along with insecticides, for controlling this virus. However, little is known about the importance of weeds in the pathosystem, which can contribute to the failure of these practices. This work aimed to evaluate the role of Datura stramonium and Nicandra physaloides as alternative hosts of ToSRV and verify the viral influence on the biological performance of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species. N. physaloides was a better alternative host for ToSRV when combined with MEAM1 whiteflies, while D. stramonium was mostly a good host for whitefly reproduction. Viral infection improved MEAM1 performance on both host plants but affected MED performance negatively. These data suggest that both weeds can be of some importance for the pathosystem, and their control should be included in management programmes.  相似文献   
950.
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