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1.
In mountainous Mediterranean regions, land abandonment processes in past decades are hypothesized to trigger secondary vegetal
succession and homogenization, which in recent years has increased the size of burned areas. We conducted an analysis of temporal
changes in landscape vegetal spatial pattern over a 15-year period (1984–1998) in a rural area of 672.3 km2 in Eastern Spain to investigate the relationship between local landscape heterogeneity and wildfire occurrence. Heterogeneity
was analyzed from textural metrics derived from non-classified remote sensing data at several periods, and was related to
wildfire history in the study area. Several neural network models found significant relationships between local spatial pattern
and future fire occurrence. In this study, sensitivity analysis of the texture variables suggested that fire occurrence, estimated
as probability of burning in the near future, increased where local homogeneity was higher. 相似文献
2.
Genetic variation of sweet potatoes (Ipomoea batatas L.) cultivated in Chile determined by RAPDs 总被引:1,自引:0,他引:1
Boris Sagredo Patricio Hinrichsen Horacio López Alberto Cubillos Carlos Muñoz 《Euphytica》1998,101(2):193-198
RAPD (randomly amplified polymorphic DNA) technology was applied to analyze the genetic variability of sweet potato germplasm
existing in Chile and elsewhere. Analysis of 28 cultivars from all over the world showed polymorphic bands with all 18 primers
tested. A total of 124 RAPD bands were scored with an average of 6.9 polymorphic bands per primer. These results confirm that
sweet potato exhibits high genetic variation. Two groups were distinguished: one containing Peruvian cultivars, and another
containing cultivars from the rest of the world. Analysis of 14 accessions from Central Chile and one from Northern Chile
showed polymorphic bands with 24 of 26 primers tested, but almost all of the 140 polymorphic bands merely showed the distinctness
of the Northern accession. The almost complete uniformity of the other 14 accessions shows that sweet potato germplasm collected
in Central Chile has very little genetic variability and may be derived from a single cultivar.
Based on these results and on historical records, some hypotheses are proposed to explain the origin of sweet potatoes cultivated
in Chile.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Lorena Caro-Corrales Jose Caro-Corrales Angel Valdez-Ortiz Jose Lopez-Valenzuela Hector Lopez-Moreno Daniel Coronado-Velazquez Emilio Hernandez-Ortiz Jose Rendon-Maldonado 《Journal of insect science (Online)》2015,15(1)
The Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most harmful pests of mango causing direct damage by oviposition on the fruit pulp. Mango for export is subjected to hydrothermal treatment as a quarantine method for the control of this pest, but exposure to heat for long periods of time reduces considerably the quality and shelf-life of treated fruit. The aim of this work was to study morphological changes of third-instar larvae and adults of A. ludens after in vitro exposure to high temperature at sublethal times. A heating block system was used to expose larvae at 46.1°C for 19.6 and 12.9 min, producing 94.6 and 70% mortality, respectively. Treated larvae were processed for optical microscopy. A fraction of surviving treated larvae was separated into containers with artificial diet to allow development into adults. Adult sexual organs were dissected and processed for transmission electron microscopy analysis. Results showed that 94.6% of the treated larvae died at 46.1°C for 19.6 min and none of the surviving larvae eclosed to adulthood, as they developed as malformed puparia. For the in vitro treatment at 46.1°C during 12.9 min, 70% of the treated larvae died and only 3.75% reached the adult stage, but ultrastructural damage in the male testes and in the female ovaries was observed. Additionally, 11.1% of the adult flies from the in vitro treatment also showed wing malformation and were incapable of flying. The analysis showed that surviving flies were unable to reproduce. 相似文献
4.
5.
Aparicio-Fernández X Reynoso-Camacho R Castaño-Tostado E García-Gasca T González de Mejía E Guzmán-Maldonado SH Elizondo G Yousef GG Lila MA Loarca-Pina G 《Plant foods for human nutrition (Dordrecht, Netherlands)》2008,63(1):35-40
Jamapa bean is a black Phaseolus vulgaris variety rich in condensed tannins, anthocyanins and flavonols with interesting biological activities. The objective of this
work was to evaluate the antiradical capacity (ARC) of a Jamapa bean methanolic extract (BME) and some of the proanthocyanidin-rich
fractions derived from it, using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The effect of the BME on some proteins involved
in apoptosis on HeLa cells was also evaluated. A strong correlation between proanthocyanidin concentration in BME and antiradical
capacity was found, suggesting that these compounds contribute significantly to antiradical activity. BME was a better radical
scavenger than butylated hydroxytoluene (45.6 and 33.9% ARC at 400 μM, respectively). Two proanthocyanidin-rich fractions
obtained after a preliminary separation of the BME using Toyopearl (TP4 and TP6) exhibited a higher antiradical activity than
the parent extract. The treatment of HeLa cells with 35 μg BME/ml/24 h increased the expression of Bax and Caspase-3, pro-apoptotic
proteins (6.13 and 1.2 times for Caspase-3 and Bax, respectively). The mechanism of action of some proteins involved in apoptosis
was also evaluated, and the results suggest that black Jamapa bean could be an important source of polyphenolic compounds
with potential biological use as antioxidant and anticancer agents. 相似文献
6.
Guillermo J. Martínez Pastur Pablo L. Peri Juan M. Cellini María V. Lencinas Marcelo Barrera Horacio Ivancich 《Annals of Forest Science》2011,68(3):587-594
•Introduction
Silviculture systems applied in Nothofagus pumilio forests are based on opening the canopy to stimulate natural regeneration by modifying light and soil moisture. The objective is to evaluate regeneration dynamics of N. pumilio along different forest canopy and solar radiation gradients. 相似文献7.
Berta Caballero-López José M. Blanco-Moreno Nicolás Pérez-Hidalgo José M. Michelena-Saval Juli Pujade-Villar Emilio Guerrieri José A. Sánchez-Espigares F. Xavier Sans 《Journal of pest science》2012,85(1):81-88
The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because
of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there
are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context,
a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect
the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional
groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences
(specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass
cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the
total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids
was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields
indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate
that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community
characteristics should be considered to better understand cereal aphid control. 相似文献
8.
José Manuel Mirás-Avalos Francisco Pérez-Sarmiento Rosalía Alcobendas Juan José Alarcón Oussama Mounzer Emilio Nicolás 《Irrigation Science》2016,34(2):161-173
Irrigation techniques that reduce water applications are increasingly applied in areas with scarce water resources. In this study, the effect of two regulated deficit irrigation (RDI) strategies on peach [Prunus persica (L.) Batsch cv. “Catherine”] performance was studied over three growing seasons. The experimental site was located in Murcia (SE Spain), a Mediterranean region. Two RDI strategies (restricting water applications at stage II of fruit development and postharvest) based on stem water potential (Ψs) thresholds (?1.5 and ?1.8 MPa during fruit growth and ?1.5 and ?2.0 MPa during postharvest) were compared to a fully irrigated control. Soil water content (θv), Ψs, gas exchange parameters, vegetative growth, crop load, yield and fruit quality were determined. RDI treatments showed significantly lower values of θv and Ψs than control trees when irrigation water was restricted, causing reductions in stomatal conductance and photosynthesis rates. Vegetative growth was reduced by RDI, as lower shoot lengths and pruning weights were observed under those treatments when compared to control. However, fruit size and yield were unaffected, and fruit quality was slightly improved by RDI. Water savings from 43 to 65 % were achieved depending on the year and the RDI strategy, and no negative carryover effect was detected during the study period. In conclusion, RDI strategies using Ψs thresholds for scheduling irrigation in mid–late maturing peach trees under Mediterranean conditions are viable options to save water without compromising yield and even improving fruit quality. 相似文献
9.
Juan Antonio Ramirez‐Merlano Víctor Mauricio Medina‐Robles Pablo Emilio Cruz‐Casallas 《Aquaculture Research》2011,42(6):738-745
The effects of straws volume, cryoprotectants and thawing temperatures were evaluated on the sperm quality of cachama blanca Piaractus brachypomus (Cuvier), an important Colombian fish species. Sexually mature fish were induced to ovulation or spermiation with a carp pituitary extract. A pool of suitable sperm samples was diluted in glucose, egg yolk, dimethyl sulphoxide (DMSO‐10%), methanol (MET‐10%) or ethylene glycol (ETG‐5%) and packed in 0.5, 2.5 or 5.0 mL straws and frozen in nitrogen vapour. The thawing process was performed in a 35 or an 80 °C water bath. The fertility was evaluated after 6 h post fertilization. The highest motility percentage (33 ± 3%) was observed with sperm cryopreserved with DMSO, packed in 5 mL straws and thawed at 35 °C. The treatments with DMSO and MET packed in 0.5 and 5.0 mL straws and thawed at 35 °C showed the highest fertility (higher than 71%) and the lowest fertility was obtained with MET‐2.5 mL (9 ± 5%). In all the treatments, a significant decrease in the sperm quality was observed at 80 °C. Sperm cryopreserved with DMSO‐10% or MET‐10%, packed in 2.5 or 5.0 mL straws are suitable to achieve acceptable fertilization and to fertilize high amounts of eggs. 相似文献
10.
Hymenoptera wasps associated with the Asian gall wasp of chestnut (Dryocosmus kuriphilus) in Calabria,Italy 总被引:1,自引:0,他引:1
Vincenzo Palmeri Pasquale Cascone Orlando Campolo Saverio B. Grande Francesca Laudani Antonino Malacrinò Emilio Guerrieri 《Phytoparasitica》2014,42(5):699-702
The parasitoid complex of the Asian chestnut gall wasp Drycosmus kuriphilus Yasumatsu was studied in Calabria (Italy). A total of 14 different species of parasitoids were collected, of which three are recorded on the Asian gall wasp for the first time. The composition of the parasitoid complex collected in Calabria was compared with that reported from Italy and from Europe. The altitude of the sites of collection seemed to have an effect on the distribution and abundance of the single species of parasitoids. 相似文献