全文获取类型
收费全文 | 2430篇 |
免费 | 160篇 |
专业分类
林业 | 186篇 |
农学 | 110篇 |
基础科学 | 13篇 |
569篇 | |
综合类 | 125篇 |
农作物 | 118篇 |
水产渔业 | 359篇 |
畜牧兽医 | 912篇 |
园艺 | 56篇 |
植物保护 | 142篇 |
出版年
2024年 | 3篇 |
2023年 | 31篇 |
2022年 | 36篇 |
2021年 | 108篇 |
2020年 | 89篇 |
2019年 | 119篇 |
2018年 | 98篇 |
2017年 | 106篇 |
2016年 | 91篇 |
2015年 | 68篇 |
2014年 | 102篇 |
2013年 | 143篇 |
2012年 | 195篇 |
2011年 | 204篇 |
2010年 | 114篇 |
2009年 | 119篇 |
2008年 | 143篇 |
2007年 | 136篇 |
2006年 | 126篇 |
2005年 | 114篇 |
2004年 | 110篇 |
2003年 | 101篇 |
2002年 | 74篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2590条查询结果,搜索用时 31 毫秒
991.
Carlos G. das Neves Swaantje Roth Espen Rimstad Etienne Thiry Morten Tryland 《Veterinary microbiology》2010
Herpesviruses of the genus Varicellovirus are known to infect and cause disease in a variety of ruminant species, but the impact of cervid herpesvirus 2 (CvHV2) in reindeer (Rangifer tarandus) is mostly unknown. Reindeer is a circum-polar species with a total estimated number of more than 5 million animals. Mortality may reach high values, as in northern Norway, especially in calves (37%; 2005–2006), and disease can potentially account for some of this mortality. CvHV2 has been isolated during a natural outbreak of infectious keratoconjunctivitis, indicating an etiologal link. Serological screening has shown that CvHV2 infection is prevalent in Northern Norway and experimental infection studies have demonstrated that viremia, latency and vertical transmission occur for CvHV2. The present review aims at summarizing current knowledge on the epidemiology, pathogenesis and molecular virology of CvHV2. 相似文献
992.
Freitas EP Rahal SC Gioso MA Vulcano LC Shimano AC da Silva JV Noritomi PY El Warrak AO 《Journal of veterinary dentistry》2010,27(4):212-221
This study aimed to develop a plate to treat fractures of the mandibular body in dogs and to validate the project using finite elements and biomechanical essays. Mandible prototypes were produced with 10 oblique ventrorostral fractures (favorable) and 10 oblique ventrocaudal fractures (unfavorable). Three groups were established for each fracture type. Osteosynthesis with a pure titanium plate of double-arch geometry and blocked monocortical screws of free angulation were used. The mechanical resistance of the prototype with unfavorable fracture was lower than that of the favorable fracture. In both fractures, the deflection increased and the relative stiffness decreased proportionally to the diminishing screw number The finite element analysis validated this plate study, since the maximum tension concentration observed on the plate was lower than the resistance limit tension admitted by the titanium. In conclusion, the double-arch geometry plate fixed with blocked monocortical screws has sufficient resistance to stabilize oblique fractures, without compromising mandibular dental or neurovascular structures. 相似文献
993.
Carlos R. Cunha Author Vitae Emanuel Peres Author Vitae Raul Morais Author Vitae Ana A. Oliveira Author Vitae Samuel G. Matos Author Vitae Miguel A. Fernandes Author Vitae P.J.S.G. Ferreira Author Vitae Author Vitae 《Computers and Electronics in Agriculture》2010,73(2):154-164
This paper describes a Viticulture Service-Oriented Framework (VSOF) which turns around context elements or tags that are placed in the field and which can be decoded by mobile devices such as mobile phones or PDAs. The tags are used to automatically associate a field location to the relevant database tables or records and also to access contextual information or services. By pointing a mobile device to a tag, the viticulturalist may download data such as climatic data or upload information such as disease and pest incidence in a simple way, without having to provide coordinates or any other references, and without having to return to a central office. This work is part of an effort to implement a large-scale distributed cooperative network in the Douro Demarcated Region in Northeast Portugal, a region in which the effort makes particular sense due to the extremely variable topography and mesoclimates. The possibility of exchanging contextualized information and accessing contextualized services in the field, using well-known devices such as cell phones, may contribute to increase the rate of adoption of information technology in viticulture, and contribute to more efficient and closer-to-the-crops practices. 相似文献
994.
Stimulatory effect of thyroid hormones improves larval development and reproductive performance in alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) 下载免费PDF全文
Sergio Castillo Kent Bollfrass Roberto Mendoza Quenton Fontenot Juan Pablo Lazo Carlos Aguilera Allyse Ferrara 《Aquaculture Research》2015,46(9):2079-2091
Development of alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) larvae was evaluated after exposure of embryos to thyroid hormones (TH) by two different methods of administration. For the first method, alligator gar embryos were placed in a water bath with triiodothyronine (T3; 1 ppm for 2 h), and control treatment embryos were placed in a water bath without T3. For the second method, spotted gar adult males and females were injected with different TH during induced spawning: a group was injected with T3 [20 mg kg?1 body weight (BW)], a second group with thyroxine (T4; 20 mg kg?1 BW), a third group with thyroid‐stimulating hormone (TSH; 4 IU kg?1BW) and a control group with dimethyl sulfoxide. Both methods resulted in increases in the concentrations of T3 and T4 in embryos of both species. An increase in the alkaline enzymatic activity of TH‐treated larvae was observed as well as an increase in the RNA:DNA, RNA:Dry weight and DNA:Dry weight ratios at hatching. Some positive effects of TH application were: a significant increase in the hatching rate of spotted gar larvae from TH‐injected parents and a higher percentage of successful spawns. Evenness of larval sizes and a higher survival rate were observed in alligator gar larvae. Snout development was accelerated by TH treatment in both species. 相似文献
995.
996.
Enriching Artemia nauplii with a high DHA‐containing lipid emulsion: search for an optimal protocol 下载免费PDF全文
Elena Viciano Óscar Monroig Ana Salvador Jaume Amat Susana Fiszman Juan Carlos Navarro 《Aquaculture Research》2015,46(5):1066-1077
This study aimed to investigate practical strategies to optimize the use of a high‐docosahexaenoic acid (DHA) lipid emulsion (M70), a product with great potential in live prey enrichments for marine larviculture. Considering its particularly high content in DHA (22:6n‐3), the adequate utilization of the emulsion for Artemia enrichments was evaluated in a series of six experiments. More specifically, the bioencapsulation efficiency of M70 into Artemia nauplii was tested under different experimental conditions of oxygen source, aeration flow, incubation temperature, concentration and dosage, as well as nauplial densities. Our results showed that an optimal utilization of M70 is achieved with incubation temperatures of 28°C, moderate aeration flows and nauplial densities of 300 ind per mL. In addition, the emulsion can be dispensed in the enrichment medium in one single dose of 0.8 g L?1, with no apparent detrimental effects on its oxidative stability and Artemia nauplii survival during enrichment. 相似文献
997.
Bruno Zaché Carlos Frederico Wilcken Ronelza Rodrigues Dacosta Everton Pires Soliman 《Phytoparasitica》2010,38(4):355-357
First report on the parasitoid Trichospilus diatraeae of the genus in Eulophidae found in the field parasitizing pupae of the eucalyptus defoliating looper Melanolophia consimilaria. This opens new perspectives for the use of this parasitoid in biological control programs against caterpillars of forestry
importance. 相似文献
998.
Manuel Valero Santiago García-Martínez Manuel J. Giner Aranzazu Alonso Juan J. Ruiz 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(3):399-405
Rumple is a serious peel collapse of Primofiori lemons in the southeast of Spain with an unresolved aetiology. Symptoms typically
occur on fruits at ripening under wet conditions as dark sunken lesions producing premature fruit drop and damaged fruits
unacceptable for fresh commercialization. A total of 16 Colletotrichum spp. isolates established from rumple-affected lemons collected during the autumn of 2007 from two different orchards were
characterized by molecular and phenotypic assays and compared with reference isolates. Species-specific PCR reactions using
β-tubulin 2 nucleotide sequences showed Colletotrichum gloeosporioides to predominate (81.5%) with limited occurrence of C. acutatum (18.75%). Among the C. gloeosporioides isolates, five (38.5%) showed benomyl resistance and eight (61.5%) were highly sensitive to the fungicide. The limited occurrence
of C. acutatum could be related to factors such as the presence of both species on the same fruit, unfavourable meteorological conditions
and low disease incidence. This work reveals an association of C. gloeosporioides and C. acutatum isolates with rumple disease of lemons and expands the range of C. acutatum on citrus. 相似文献
999.
Eduardo R. Trentacoste Carlos M. Puertas Víctor O. Sadras 《European Journal of Agronomy》2010,32(4):249-254
Olive oil yield and its components (fruit number, average fruit weight and fruit oil concentration) depend on crop load and source–sink ratios as affected by environmental conditions, management and the alternate bearing typical of the species. The aims of this work were to: (i) establish quantitative relationships between oil yield and its components as affected by fruit load in a high-yielding production system, (ii) analyse the dynamics of fruit weight and fruit oil concentration in terms of rates and durations, and (iii) explore the relationships between the dynamics of oil and water in fruit. In a fully irrigated olive orchard in Mendoza (32° S), Argentina, cv. Arbequina trees with similar crown volume and three fruit loads (3-fold range) were monitored during two seasons. Oil yield was positively associated with both fruit number and fruit fresh weight, but not with fruit oil concentration. Across seasons and fruit loads, fruit yield increased linearly with fruit number at ~1.5 kg per thousand fruit and reached a maximum ~60 kg tree?1 (or 25 t ha?1) at a fruit load of 32,700 fruit tree?1. The fruit filling rate was affected by fruit load, while the duration of fruit growth and the dynamics of oil and water concentration were unaffected by fruit load. Fruit water concentration reached a minimum at the onset of Stage III of fruit growth, which was marked by a rapid increase in oil concentration. Fruit fresh weight and oil weight increased with source–sink ratio from ~0.5 up to a threshold ~2 m3 crown per thousand fruit. In contrast, a 8-fold range of source–sink ratio did not affect fruit oil concentration. 相似文献
1000.
Wilson Roberto Maluf Vanisse de Fátima Silva Maria das Graças Cardoso Luiz Antonio Augusto Gomes Álvaro Carlos Gonçalves Neto Gabriel Mascarenhas Maciel Daniela Aparecida Castro Nízio 《Euphytica》2010,176(1):113-123
Zingiberene (ZGB) and acylsugars (AS) are allelochemicals responsible for high levels of arthropod resistance found in Solanum habrochaites (= Lycopersicon hirsutum) var. hirsutum ‘PI 127826’ and S. (= L.) pennelli ‘LA 716’, respectively. These accessions were used to develop commercial lines with good levels of pest resistance. The objective
of the present work was to assess the ZGB and AS contents and the levels of resistance to Tuta absoluta in tomato hybrids between high ZGB × high AS lines, as compared with their parental lines and with commercial checks. High
AS homozygous lines [TOM-688 and TOM-689, both originated from the interspecific cross S. lycopersicum (= L. esculentum) × S. pennelli], high ZGB homozygous lines (ZGB-703 and ZGB-704, both derived from the interspecific cross S. lycopersicum × S. habrochaites var. hirsutum), double heterozygotes for both ZGB and AS, single heterozygotes for ZGB, and single heterozygotes for AS were assessed for
AS and ZGB contents. Low-ZGB low-AS checks ‘Débora Max’ and ‘TOM-684’ were used, as well as checks with high ZGB (PI 127826)
and high AS (LA 716). The genotypes were submitted to infestation with South American tomato pinworm adults in a screenhouse,
and oviposition counts were taken 10 days after the initial infestation date. Plants were scored for overall plant damage
and percent leaflets attacked up to the 38th day after infestation. Genotypes heterozygous for ZGB or AS showed allelochemical
contents intermediate to those of their high and low content parents, indicating incompletely dominant gene action for contents
of each of the allelochemicals. There were no significant differences in T. absoluta oviposition between high-AS homozygous genotypes, high-ZGB homozygotes, single heterozygotes for AS, single heterozygotes
for ZGB and double heterozygotes for ZGB and AS, but all these genotypes showed egg counts significantly lower than the low-ZGB
low-AS checks. Feeding damage of T. absoluta was higher in the low-ZGB low-AS checks than in any other ZGB-rich or AS-rich tomato genotype. Relative to ZGB or AS single
heterozygotes, the heterozygotes for both ZGB and AS showed higher levels of resistance to the insect, as measured by overall
plant damage, indicating a synergic effect of the allelochemicals on resistance. 相似文献