全文获取类型
收费全文 | 8637篇 |
免费 | 527篇 |
国内免费 | 50篇 |
专业分类
林业 | 578篇 |
农学 | 435篇 |
基础科学 | 80篇 |
1542篇 | |
综合类 | 631篇 |
农作物 | 429篇 |
水产渔业 | 627篇 |
畜牧兽医 | 3983篇 |
园艺 | 124篇 |
植物保护 | 785篇 |
出版年
2023年 | 78篇 |
2022年 | 139篇 |
2021年 | 257篇 |
2020年 | 249篇 |
2019年 | 314篇 |
2018年 | 271篇 |
2017年 | 299篇 |
2016年 | 315篇 |
2015年 | 214篇 |
2014年 | 308篇 |
2013年 | 480篇 |
2012年 | 481篇 |
2011年 | 532篇 |
2010年 | 266篇 |
2009年 | 298篇 |
2008年 | 437篇 |
2007年 | 422篇 |
2006年 | 383篇 |
2005年 | 366篇 |
2004年 | 338篇 |
2003年 | 297篇 |
2002年 | 336篇 |
2001年 | 242篇 |
2000年 | 245篇 |
1999年 | 205篇 |
1998年 | 60篇 |
1997年 | 58篇 |
1996年 | 59篇 |
1995年 | 53篇 |
1994年 | 37篇 |
1993年 | 40篇 |
1992年 | 82篇 |
1991年 | 55篇 |
1990年 | 61篇 |
1989年 | 70篇 |
1988年 | 63篇 |
1987年 | 51篇 |
1986年 | 46篇 |
1985年 | 58篇 |
1984年 | 39篇 |
1983年 | 42篇 |
1982年 | 30篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1974年 | 24篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1970年 | 27篇 |
排序方式: 共有9214条查询结果,搜索用时 15 毫秒
991.
Ocular lesions associated with Trypanosoma spp. infection have been described in man and many animal species. However, loss of vision has not been demonstrated in humans presenting Chagas disease or in animals affected by different trypanosome species. In order to assess the possible ocular disorders caused by Trypanosoma evansi infection, six goats were inoculated with 1 x 10(5) T. evansi and maintained for 12 months and four goats were used as control. The inoculated animals became positive at serological and parasitological tests at 1-month post-inoculation and showed a subclinical course of the disease. Unilateral superficial corneal ulceration and retinochoroiditis were observed in two inoculated animals. Data from ocular neurologic examination and electroretinography showed no significant differences between inoculated and non-inoculated goats. It could be concluded that Trypanosoma evansi can produce ocular lesion but without apparent loss of vision in goats. 相似文献
992.
Clinical and topographic magnetic resonance characteristics of suspected brain infarction in 40 dogs
Garosi L McConnell JF Platt SR Barone G Baron JC de Lahunta A Schatzberg SJ 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2006,20(2):311-321
Medical records of 40 dogs presented for evaluation of acute-onset, nonprogressive, intracranial dysfunction by means of magnetic resonance imaging (MRI) diagnosis of brain infarction were reviewed. Location of the brain infarcts was: 11 of 38, telencephalic; 8 of 38, thalamic/midbrain; 18 of 38, cerebellar; and 3 of 38, multifocal. Telencephalic infarcts developed within the territory of the middle cerebral (4/11), rostral cerebral (2/11), and striate (5/11) arteries. Thalamic/midbrain infarcts developed within the territory of perforating arteries of the caudal portion of the thalamus and rostral portion of the brainstem (8/8). All cerebellar infarcts (18/38) were within the territory of the rostral cerebellar artery or one of its branches. All infarcts appeared nonhemorrhagic, with marked contrast enhancement observed in only 3 of 38 dogs, all of which were imaged more than 7 days after the onset of signs of neurologic dysfunction. Diffusion-weighted imaging (DWI) sequences were available from 6 dogs, all imaged within 5 days of the onset of signs of neurologic dysfunction. Suspected infarcts were hyperintense on DWI sequences and were hypointense on the apparent diffusion coefficient map. Telencephalic infarcts caused abnormal mental status, contralateral postural reaction deficit, contralateral nasal hypalgesia, contralateral menace deficit, and ipsilateral circling. Thalamic/midbrain infarcts caused contralateral or ipsilateral postural reaction deficit, contralateral menace deficit, ipsilateral head tilt or turn, nystagmus, ventrolateral strabismus, and anisocoria. Cerebellar infarcts caused ipsilateral asymmetric cerebellar quality ataxia, head tilt, intermittent opisthotonus, nystagmus, and ipsilateral menace deficit with apparent normal vision. 相似文献
993.
994.
In Burkina Faso, African Animal Trypanosomosis (AAT) is still a major hindrance to cattle breeding, especially in the Mouhoun river basin, which was identified as a priority area for tsetse control. The attempt of the present work was to assess the abundance of tsetse flies and AAT risk using remote sensing coupled to field environmental data, along a Mouhoun river section of 234 km long, harbouring an open riverine forest where G. tachinoides Westwood is the predominant tsetse species. The water course was classified into three epidemiological landscapes, corresponding to a "disturbed", "natural" and finally "border" vegetal formation at the interface of the two formers. Using the mean number of infected flies by trap and by day as a risk indicator, the border landscape was found to be 5.4 (1.3-12.0) and 15.8 (4.7-41.6) times more risky than the natural and disturbed ones respectively. These results led to propose that a campaign against tsetse, undertaken by a development project called PAEOB (Projet d'Appui à l'Elevage dans l'Ouest du Burkina Faso), should be focussed on only 34% of the hydrographic network. 相似文献
995.
Quantified transmission parameters of Foot-and-Mouth Disease Virus (FMDV) are needed for epidemic models used for control and surveillance. In this study, we quantified the within- and between-pen transmission of FMDV in groups of pigs by estimating the daily transmission rate beta, i.e. the number of secondary infections caused by one infectious pig during one day, using an SIR (susceptible-infectious-removed) model. Within-pen transmission was studied in four groups of ten pigs in which 5 infected and 5 susceptible pigs had direct contact; between-pen transmission was studied in one group of ten pigs in which 5 infected and 5 susceptible pigs had indirect contact. Daily results of virus isolation of oropharyngeal fluid were used to quantify the transmission rate beta, using Generalised Linear Modelling (GLM) and a maximum likelihood method. In addition, we estimated the expected time to infection of the first pig within a pen T(w) and in the indirect-contact pen T(b). The between-pen transmission rate beta(b) was estimated to be 0.59 (0.083-4.18) per day, which was significantly lower than the within-pen transmission rate beta(w) of 6.14 (3.75-10.06). T(w) was 1.6 h, and T(b) was 16 h. Our results show that the transmission rate is influenced by contact structure between pigs. 相似文献
996.
de la Fe C Assunção P Rosales RS Antunes T Poveda JB 《Veterinary journal (London, England : 1997)》2006,171(3):532-538
Mycoplasma mycoides subsp. mycoides (LC) (Mmm LC) and Mycoplasma agalactiae are the most important mycoplasma species involved in the contagious agalactia syndrome. A total of 25 field strains from Spain and the two type strains were analysed by SDS-PAGE and immunoblotting. Two polyclonal antisera (PAbs) raised against a pool of strains of each mycoplasma species were used. The results revealed a high degree of protein variability among the field strains. The type strain of Mmm LC appeared to be representative of the field strains of this species, whereas this was not the case with the M. agalactiae type strain. Whereas M. agalactiae is known to possess a gene family regulating surface antigen diversity, there is a need to study the mechanisms used byMmm LC to generate antigenic variability in more detail. 相似文献
997.
Trujillo M Mateos R Collantes de Teran L Espartero JL Cert R Jover M Alcudia F Bautista J Cert A Parrado J 《Journal of agricultural and food chemistry》2006,54(11):3779-3785
Antioxidant activities of lipophilic hydroxytyrosyl acetate, palmitate, oleate, and linoleate were compared with those of hydroxytyrosol, alpha-tocopherol, and butylhydroxytoluene (BHT) in both glyceridic matrix and biological systems. Aliquots of a glyceridic matrix spiked with various concentrations of antioxidant were subjected to accelerated oxidation in a Rancimat apparatus operated at 90 degrees C. The relationships between induction time (IT) and antioxidant concentration (mmol/kg) presented by hydroxytyrosol and hydroxytyrosyl acetate, palmitate, oleate, and linoleate were similar. Hydroxytyrosol and its esters showed greater antioxidant activity than alpha-tocopherol or BHT. We also evaluated the capacity of hydroxytyrosyl esters to protect proteins and lipids against oxidation caused by peroxyl radicals, using a brain homogenate as an ex vivo model. All tested compounds showed a protective effect in these systems, which was greater in preventing the generation of carbonyl groups in protein than of malondialdehyde in lipid. Inclusion of a lipophilic chain in the hydroxytyrosol molecule enhanced its antioxidant capacities in this biological model. 相似文献
998.
In this study, factors influencing the disruption and aggregation of casein micelles during high-pressure (HP) treatment at 250 MPa for 40 min were studied in situ in serum protein-free casein micelle suspensions. In control milk, light transmission increased with treatment time for approximately 15 min, after which a progressive partial reversal of the HP-induced increase in light transmission occurred, indicating initial HP-induced disruption of casein micelles, followed by reformation of casein aggregates from micellar fragments. The extent of HP-induced micellar disruption was negatively correlated with the concentration of casein micelles, milk pH, and levels of added ethanol, calcium chloride, or sodium chloride and positively correlated with the level of added sodium phosphate. The reformation of casein aggregates during prolonged HP treatment did not occur when HP-induced disruption of casein micelles was limited (<60%) or very extensive (>95%) and was promoted by a low initial milk pH or added sodium phosphate, sodium chloride, or ethanol. On the basis of these findings, a mechanism for HP-induced disruption of casein micelles and subsequent aggregation of micellar fragments is proposed, in which the main element appears to be HP-induced solubilization of micellar calcium phosphate. 相似文献
999.
Julia Peixoto de Albuquerque Fabio Faria da Mota Irene von der Weid Lucy Seldin 《European Journal of Soil Biology》2006,42(4):200-207
Strains belonging to Paenibacillus durus isolated from the rhizosphere of various grasses and from bulk soil were previously divided into five phenotypic groups (A1–A5) based on the fermentation pattern of six carbohydrates (A1: sorbitol (+), A2: dulcitol and tagatose (+), A3: starch and glycogen (+), A4: starch, glycogen and d-arabitol (+) and A5: negative for these carbohydrates). This study aimed to assess whether plant types select for specific P. durus phenotypic groups. For that purpose, polymerase chain reaction-restriction fragment length polymorphism analysis of part of genes encoding 16S rRNA (ARDRA) and DNA gyrase subunit B (gyrB-RFLP) were used to produce genetic fingerprints. ARDRA and gyrB-RFLP data were clustered together to generate a dendrogram and two main clusters were observed. Cluster I showed a predominance of strains isolated from wheat, maize and sugarcane rhizospheres. Strains isolated from maize were distributed among the five patterns of carbohydrate metabolism, while strains isolated from sugarcane showed to be predominantly able to metabolize starch and glycogen. Neither sorbitol- nor arabitol-metabolizing strains were found in cluster II, which consisted of strains isolated from soil and from all plant species used. Our results suggest that the plants influenced the diversity of P. durus in their rhizospheres. 相似文献
1000.
de Onis M Onyango AW Borghi E Garza C Yang H;WHO Multicentre Growth Reference Study Group 《Public health nutrition》2006,9(7):942-947
OBJECTIVES: To compare growth patterns and estimates of malnutrition based on the World Health Organization (WHO) Child Growth Standards ('the WHO standards') and the National Center for Health Statistics (NCHS)/WHO international growth reference ('the NCHS reference'), and discuss implications for child health programmes. DESIGN: Secondary analysis of longitudinal data to compare growth patterns (birth to 12 months) and data from two cross-sectional surveys to compare estimates of malnutrition among under-fives. SETTINGS: Bangladesh, Dominican Republic and a pooled sample of infants from North America and Northern Europe. SUBJECTS: Respectively 4787, 10 381 and 226 infants and children. RESULTS: Healthy breast-fed infants tracked along the WHO standard's weight-for-age mean Z-score while appearing to falter on the NCHS reference from 2 months onwards. Underweight rates increased during the first six months and thereafter decreased when based on the WHO standards. For all age groups stunting rates were higher according to the WHO standards. Wasting and severe wasting were substantially higher during the first half of infancy. Thereafter, the prevalence of severe wasting continued to be 1.5 to 2.5 times that of the NCHS reference. The increase in overweight rates based on the WHO standards varied by age group, with an overall relative increase of 34%. CONCLUSIONS: The WHO standards provide a better tool to monitor the rapid and changing rate of growth in early infancy. Their adoption will have important implications for child health with respect to the assessment of lactation performance and the adequacy of infant feeding. Population estimates of malnutrition will vary by age, growth indicator and the nutritional status of index populations. 相似文献