全文获取类型
收费全文 | 14455篇 |
免费 | 986篇 |
国内免费 | 113篇 |
专业分类
林业 | 1359篇 |
农学 | 592篇 |
基础科学 | 119篇 |
3642篇 | |
综合类 | 734篇 |
农作物 | 779篇 |
水产渔业 | 1444篇 |
畜牧兽医 | 5350篇 |
园艺 | 246篇 |
植物保护 | 1289篇 |
出版年
2023年 | 130篇 |
2022年 | 192篇 |
2021年 | 367篇 |
2020年 | 394篇 |
2019年 | 336篇 |
2018年 | 631篇 |
2017年 | 657篇 |
2016年 | 648篇 |
2015年 | 510篇 |
2014年 | 589篇 |
2013年 | 929篇 |
2012年 | 1155篇 |
2011年 | 1080篇 |
2010年 | 646篇 |
2009年 | 530篇 |
2008年 | 819篇 |
2007年 | 825篇 |
2006年 | 687篇 |
2005年 | 682篇 |
2004年 | 565篇 |
2003年 | 540篇 |
2002年 | 441篇 |
2001年 | 305篇 |
2000年 | 307篇 |
1999年 | 243篇 |
1998年 | 68篇 |
1997年 | 71篇 |
1996年 | 47篇 |
1995年 | 47篇 |
1994年 | 38篇 |
1993年 | 37篇 |
1992年 | 68篇 |
1991年 | 49篇 |
1990年 | 59篇 |
1989年 | 59篇 |
1988年 | 47篇 |
1987年 | 44篇 |
1986年 | 50篇 |
1985年 | 58篇 |
1984年 | 44篇 |
1983年 | 44篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1979年 | 37篇 |
1978年 | 33篇 |
1977年 | 31篇 |
1974年 | 35篇 |
1973年 | 46篇 |
1972年 | 33篇 |
1971年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
David Espinosa-Avilés Víctor Manuel Salomón-Soto Socorro Morales-Martínez 《Journal of zoo and wildlife medicine》2008,39(1):21-27
Blood samples from 16 adult, wild Mexican beaded lizards were obtained for complete blood count and serum biochemical analysis. In addition, both oral and cloacal swab samples were collected and submitted for bacteriologic culture. This is the first report of hematologic and bacterial data from free-living beaded lizards. This information will serve as baseline reference values for future health assessment studies in conservation, captive breeding, and research programs. 相似文献
132.
Ediane Batista da Silva Bruna Daniella de Souza Silva Jerônimo Rafael Ruiz Leon André Kipnis Isabel K.F. de Miranda Santos Ana Paula Junqueira-Kipnis 《Veterinary journal (London, England : 1997)》2011,187(2):276-278
This study evaluated the Mycobacterium tuberculosis protein antigen MPT-51, the trimeric antigen 85 (Ag85) complex, and Bacillus Calmette-Guérin (BCG) in an indirect ELISA to diagnose bovine tuberculosis (TB) from serum samples. Serum was collected from 208 intra-dermal tuberculin test (ITT)-positive and 54 ITT-negative animals from a region where bovine TB is endemic. Using the Ag85 and BCG antigens, the indirect ELISA was able to discriminate ITT-positive from ITT-negative animals. This level of discrimination was not achieved when using the MPT-51 antigen. The highest sensitivity (Se) and specificity (Sp) of the test was found when BCG was used (Se, 82%; Sp, 91%). Further work in different epidemiological settings and with larger numbers of animals will be required to validate these findings. 相似文献
133.
Soares RM de Souza SL Silveira LH Funada MR Richtzenhain LJ Gennari SM 《Veterinary parasitology》2011,180(3-4):344-348
We have studied the variability of glutamate dehydrogenase (gdh) and small subunit ribosomal (SSU) rRNA coding genes of Giardia species in fecal samples isolated from wild and exotic animals in Brazil, and compared with homologous sequences of isolates from human and domestic animals characterized in previous studies. Cysts of Giardia duodenalis were obtained from feces of naturally infected monkeys (Alouatta fusca) (n=20), chinchillas (Chinchilla lanigera) (n=3), ostriches (Struthio camelus) (n=2) and jaguar (Panthera onca) (n=1). Assemblage AI was assigned to the unique isolate of jaguar. All the samples from monkeys, chinchillas, and ostriches were assigned to Assemblage B. There was little evolutionary divergence between the referred isolates and isolates described elsewhere. The Assemblage B isolates identified in this study were closely related to Assemblage BIV isolated from humans. The molecular identification of Assemblages A and B of G. duodenalis isolates from exotic and wild animals demonstrates that such hosts may be a potential reservoir for zoonotic transmission of G. duodenalis. 相似文献
134.
Reynolds BS Boudet KG Faucher MR Geffre A Germain C Lefebvre HP 《Journal of the American Animal Hospital Association》2008,44(2):51-59
Pediatric devices based on a capillary system may provide an alternative to vacuum tubes for canine blood sampling. The potential advantages are absence of vein collapse, limited blood volume sampled, and improved safety. The aim of this study was to compare routine plasma and hematological variables in seven healthy dogs using both techniques. Five biochemical analytes were measured, and a complete hematological examination and plasma exogenous creatinine clearance test were performed. No clinically relevant difference between the two techniques was observed for any variable or functional test assessed. 相似文献
135.
Lunardi M Headley SA Lisbôa JA Amude AM Alfieri AA 《Research in veterinary science》2008,85(3):599-604
When first described in 1946, bovine viral diarrhea (BVD) was characterized as an acute transmissible disease associated with severe leucopenia, high fever, depression, diarrhea, gastrointestinal erosions, and hemorrhages. Recently the severe acute form has been related only to some hypervirulent BVDV-2 strains. This article reports the detection of BVDV-1b associated with an acute and fatal outbreak of BVD in a Brazilian beef cattle herd. Depression, anorexia, watery diarrhea, sialorrhea, and weakness were observed in six steers. One of these animals was evaluated for laboratorial, clinical, and pathological alterations. Laboratory findings were non-specific; clinically, the animal was weak, with dehydration and erosive oral lesions. Pathological alterations were predominant at the tongue, esophagus, and rumen. A RT-PCR assay using primers to partially amplify the 5′ untranslated region (5′UTR) of the BVDV genome was performed and identified BVDV in all clinical samples analyzed. Phylogenetic analysis of BVDV derived from lymph node revealed that this strain was clustered within the BVDV subtype 1b. This differentiating was only possible to be performed by molecular characterization since both clinical presentation and pathologic findings were similar to BVDV-2 infection. 相似文献
136.
de Siqueira A Cassiano FC Landi MF Marlet EF Maiorka PC 《Journal of Feline Medicine and Surgery》2012,14(10):723-728
Animal cruelty is defined as a deliberate action that causes pain and suffering to an animal. In Brazil, legislation known as the Environmental Crimes Law states that cruelty toward all animal species is criminal in nature. From 644 domestic cats necropsied between January 1998 and December 2009, 191 (29.66%) presented lesions highly suggestive of animal cruelty. The main necroscopic finding was exogenous carbamate poisoning (75.39%) followed by blunt-force trauma (21.99%). Cats from 7 months to 2 years of age were the most affected (50.79%). In Brazil, violence is a public health problem and there is a high prevalence of domestic violence. Therefore, even if laws provide for animal welfare and protection, animals are common targets for violent acts. Within a context of social violence, cruelty toward animals is an important parameter to be considered, and the non-accidental lesions that were found are evidence of malicious actions. 相似文献
137.
A Anadón M R Martínez-Larra?aga M J Díaz C Vélez P Bringas 《American journal of veterinary research》1990,51(11):1756-1759
The pharmacokinetics of pipemidic acid after 2 single doses were studied in broiler chickens. Chickens were given single IV and oral doses of 10 and 30 mg of pipemidic acid/kg of body weight. Blood samples were collected over 8 hours after each dose administration. High-pressure liquid chromatography with UV detection was used to determine concentrations in plasma of pipemidic acid. The plasma concentration-time curves after IV administration followed 2-compartment characteristics, rapid initial distribution phase, and a terminal elimination phase. The pharmacokinetic variables differed significantly between single doses of 10 and 30 mg of pipemidic acid/kg. Mean disposition variables were a half-life at alpha phase of 0.06 hours or 0.33 hours, a half-life at beta phase of 1.18 hours or 1.72 hours, a volume of distribution in the central compartment of 0.12 L/kg or 0.31 L/kg, a volume of distribution during the elimination beta phase of 1.64 L/kg or 1.05 L/kg, and a total plasma clearance of 0.97 L/h.kg or 0.41 L/h.kg, for the 10 or 30 mg/kg dose, respectively. After oral administration, the pipemidic acid plasma profile could be adequately described by a 1-compartment model. After the single oral doses of 10 and 30 mg of pipemidic acid/kg, pipemidic acid was absorbed rapidly (time to maximal concentration of 0.31 hours or 0.71 hours) and eliminated with a mean half-life of 0.86 hours or 0.61 hours, respectively. The bioavailability was 39% at 10 mg of pipemidic acid/kg and 61% at 30 mg of pipemidic acid/kg. 相似文献
138.
Parraguez VH Atlagich MA Urquieta B Galleguillos M De Los Reyes M Kooyman DL Araneda S Raggi LA 《Canadian journal of veterinary research》2010,74(3):193-199
Fetal weight and the placenta of sheep at high altitude (HA) are affected by hypoxia. Placental changes (an increase in placental size and vascularization) are greater in ewes from populations that have lived for several generations at HA than in those exposed during just 1 gestation. This study investigated placental expression of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS), 2 molecules involved in placental angiogenesis that could be upregulated by hypoxia. Two groups of ewes were maintained at HA (3589 m) during pregnancy: HA-native ewes (group HH) and ewes native to lowlands but moved to HA immediately after the diagnosis of pregnancy (group LH). A control group (LL) was kept at sea level. Near term, placentomes were removed, weighed, and processed for immunohistochemical detection of VEGF and eNOS, as well as for vascular area measurement. Placental weight was significantly higher in the HH group than in the LH and LL groups; between the latter 2 groups there was no significant difference. The placental area occupied by vasculature was significantly greater in both the HA groups than in the LH group; the number of placentomes was greatest in the LL group. The density of VEGF and eNOS in the placentome tissue was significantly greater in both HA groups than in the LL group. Although the density of VEGF was significantly lower in the HH group than in the LH group, no differences were observed in eNOS density between the HH and LH animals. These results demonstrate that chronic hypoxia upregulates the expression of placental VEGF and eNOS, suggesting an important role of these molecules in the placental response to HA hypoxia. In addition, an attenuated response to hypoxia in VEGF synthesis may be part of the long-term process of adaptation to HA. 相似文献
139.
Renal handling of calcium and phosphorus in experimental renal hyperparathyroidism in dogs 总被引:3,自引:0,他引:3
García-Rodríguez MB Pérez-García CC Ríos-Granja MA Cano-Rábano MJ Peña-Penabad M Gallego-Morales D García-Partida P Diez-Prieto I 《Veterinary research》2003,34(4):379-387
Twenty-four hour urinary excretion, fractional excretion and the filtered load of calcium and phosphorus were monitored as hyperparathyroidism evolved in a model of progressive canine renal failure. Thirteen beagles of both sexes aged four and a half months were used. Nine of them were subjected to a renal damaging schedule (neomycine, 60 mg/kg/48 h, IM, 32 weeks) in order to induce chronic renal failure leading to secondary hyperparathyroidism (2HPT group). The remaining four were kept as the control group. The experiment was conducted over 32 weeks. Blood and 24 h urine were collected every four weeks. Calcium, phosphorus and creatinine were analyzed. Plasma parathormone and calcitonin were determined at weeks 0, 12, 24 and 32. The level of renal function in the 2HPT animals was reduced to 25% of that of the controls (endogenous creatinine clearance was 0.45 +/- 0.22 mL/min/kg as opposed to 1.81 +/- 0.54 mL/min/kg). Hyperparathyroidism was confirmed by a progressive increase in the levels of the parathyroid hormone. Calcitonin levels were not modified. A tendency to hypocalcaemia was observed, reaching statistically significant levels from the twenty-eighth week of the study, when hyperphosphataemia also became significant. Daily urinary excretion of calcium and phosphorus remained at values considered normal throughout the experiment with no alteration imputable to the impaired renal function. This is explained by the decrease in the filtered load of these elements (in both cases statistically significant from the 24th week on) being associated with an increase in their fractional excretion. Thus, calcium and phosphorus urinary excretion values could be maintained in a normal range up to the end of the experiment, showing that renal calcium handling in dogs with experimentally induced renal failure seems to differ from that observed in human patients. 相似文献
140.
There are very few resistance records on cattle nematodes. South American successive records have been increasing rapidly since the year 2000. In Argentina, increasing dissatisfaction based on the exclusive use of macrocyclic lactones has prompted the use of benzimidazoles in the Pampean region. The studied farm is located in the Argentina humid Pampas and had apparently poor results after anthelmintic treatments. Evaluation of resistance was firstly based on faecal egg reduction after treatment in November 2001 and June 2002 and was complemented with worm counts obtained by necropsy in June 2002. The study reports that the reduction of faecal egg excretion after benzimidazole (reduction 31-79%) or ivermectin treatments (76-97%) in November 2001 was insufficient and these poor results were confirmed in June 2002 (benzimidazoles (65-89%) and ivermectin (47-77%)). Several methods for evaluating faecal egg count reduction were performed and yielded different results. A new method based on the estimated faecal egg counts (corrected from the initial faecal egg counts and animal type using a general linear model) was used and gave higher flexibility in the interpretation of putative resistance to anthelmintics. From necropsy results, it could be concluded that Cooperia oncophora was resistant to avermectins and benzimidazoles and that Cooperia punctata, Ostertagia ostertagi and Haemonchus placei were resistant to benzimidazoles. This case of multispecies and multidrug resistance is probably not unique and could reflect the emergence of resistances in Argentina. This emergence is probably due to the intensive use of anthelmintics, the absence of refugia, and the frequent circulation of infected cattle. 相似文献