全文获取类型
收费全文 | 6394篇 |
免费 | 358篇 |
国内免费 | 4篇 |
专业分类
林业 | 528篇 |
农学 | 284篇 |
基础科学 | 38篇 |
1763篇 | |
综合类 | 285篇 |
农作物 | 449篇 |
水产渔业 | 659篇 |
畜牧兽医 | 2080篇 |
园艺 | 123篇 |
植物保护 | 547篇 |
出版年
2024年 | 7篇 |
2023年 | 83篇 |
2022年 | 115篇 |
2021年 | 242篇 |
2020年 | 245篇 |
2019年 | 245篇 |
2018年 | 284篇 |
2017年 | 300篇 |
2016年 | 275篇 |
2015年 | 224篇 |
2014年 | 298篇 |
2013年 | 441篇 |
2012年 | 542篇 |
2011年 | 518篇 |
2010年 | 293篇 |
2009年 | 236篇 |
2008年 | 426篇 |
2007年 | 435篇 |
2006年 | 306篇 |
2005年 | 275篇 |
2004年 | 222篇 |
2003年 | 229篇 |
2002年 | 199篇 |
2001年 | 39篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1980年 | 5篇 |
1977年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1969年 | 3篇 |
1966年 | 4篇 |
1934年 | 2篇 |
排序方式: 共有6756条查询结果,搜索用时 13 毫秒
21.
OBJECTIVE: To evaluate a technique for preservation of organoleptic tissue characteristics (color, odor, texture, and flexibility) in cadavers used for surgical instruction. STUDY DESIGN: Experimental study. ANIMALS: Forty-three canine cadavers. METHODS: Cadavers were preserved with a modified Larssen solution of the Hospital Cochim, Paris and cryopreservation. Tissue handling qualities were evaluated in surgical laboratory sessions. RESULTS: All cadavers kept texture and tissues consistency, especially skin and muscle, similar to those of live animals. Some skin desquamation and pallor of the mucous membranes occurred with repetitive freeze-thaw cycles. CONCLUSIONS: This preservation technique provides acceptable cadaver quality and tissue handling for use in surgical instruction. CLINICAL RELEVANCE: Preparation of patient cadavers by intravascular injection of modified Larssen solution yielded suitable instructional models for surgical training. 相似文献
22.
23.
Otranto D Paradies P Testini G Latrofa MS Weigl S Cantacessi C Mencke N de Caprariis D Parisi A Capelli G Stanneck D 《Veterinary parasitology》2008,153(3-4):320-328
Canine monocytic ehrlichiosis (CME) caused by Ehrlichia canis is the most known canine tick-borne disease (TBD) spread throughout the world. Preventing tick bites is a priority to reduce the risk of TBDs and it was the aim of the present study to evaluate the efficacy of a combination of imidacloprid 10% and permethrin 50% (ImPer) (Advantix; Bayer AG, Germany) in a spot-on formulation to control CME under field conditions. On January-March 2005, 845 dogs from two kennels in southern Italy (kennels of Bari (KB)- and Ginosa (KG)), with a history of tick infestation were initially tested by serology and PCR assay for E. canis infection. Data on Leishmania infantum infection were also available from a previous study carried out on the same dog population. One hundred twenty-six dogs (14.9%) presented anti-E. canis antibodies with a relative prevalence of 15.6% (n=65 dogs in KB) and 14.2% (n=61 dogs in KG). Five hundred thirty-five animals found negative both for E. canis and L. infantum infections were enrolled in three groups (Group A--treated with ImPer once a month; Group B--treated every 2 weeks; and Group C--untreated control animals) and monitored for E. canis infection by serology and PCR in November 2005 (first follow-up) and in March 2006 (second follow-up). The E. canis infection was serologically revealed, at the first and/or second follow-up, in 26 animals from Group C in KB and KG (mean incidence density rate (IDR), 13.24%) while in none of the animals from Group A (KB and KG) and only in one animal from Group B (IDR 1.13%) in KG. The final protection efficacy of ImPer ranged from 95.57% to 100% in Groups B and A. At PCR only 15 dogs from KG were positive for Rickettsiales only at the first follow-up and at the sequence analysis two (both in Group C) revealed 100% homology with E. canis sequences while 13 with Anaplasma platys. Four out of 13 A. platys PCR-positive dogs were also seropositive for E. canis at one or both follow-ups. ImPer, by virtue of its repellent and acaricidal activity against ticks, has been shown to be efficacious to prevent E. canis infection in treated dogs living under natural conditions in endemic areas. 相似文献
24.
Pecinali NR Gomes RN Amendoeira FC Bastos AC Martins MJ Pegado CS Bastos OM Bozza PT Castro-Faria-Neto HC 《Veterinary parasitology》2005,134(1-2):121-130
Toxocara canis is a nematode of the Ascaridae family that normally parasites the small intestine of canid species. Humans are accidentally infected upon ingestion of embryonated eggs, and can manifest several clinical alterations such as fever, hepatomegaly, splenomegaly, respiratory symptoms, muscle pain and anorexia. In the present work, we investigated the kinetics of tissue distribution of L2 larva in lungs, liver, kidney, brain, skeletal muscle and myocardium. Also, we analyzed the blood and bronchoalveolar lavage fluid (BAL) for levels of IL-6, IFN-gamma, eotaxin and Regulated on Activation Normal T Cell Expressed and Secreted (RANTES) in experimental murine T. canis infection. We observed liver, lung and kidney lesions correlated to larva migration as early as the first day of infection. After the seventh post-infection day, larva could also be detected in brain, skeletal muscle and heart, as an indicator of biphasic migration pattern. Increased inflammatory activity was detected in BAL and plasma of infected animals, as was an intense eosinophil migration associated with an increase in the levels of all the cytokines studied. In conclusion, our results establish a tight correlation between tissue lesions caused by larva migration and increased plasma levels of pro-inflammatory and eosinophil chemotactic cytokines. Thus, murine T. canis infection may prove to be useful in understanding the role of cytokines in infection. 相似文献
25.
26.
MI Menéndez MA Phelps EA Hothem AL Bertone 《American journal of veterinary research》2012,73(9):1453-1461
Objective-To determine the pharmacokinetics of methylprednisolone (MP) and the relationship between MP and hydrocortisone (HYD) concentrations in plasma and urine after intra-articular (IA) administration of 100 or 200 mg of MP acetate (MPA) to horses. Animals-Five 3-year-old Thoroughbred mares. Procedures-Horses exercised on a treadmill 3 times/wk during the study. Horses received 100 mg of MPA IA, then 8 weeks later received 200 mg of MPA IA. Plasma and urine samples were obtained at various times for 8 weeks after horses received each dose of MPA; concentrations of MP and HYD were determined. Pharmacokinetic-pharmacodynamic estimates for noncompartmental and compartmental parameters were determined. Results-Maximum concentration of MP in plasma was similar for each MPA dose; concentrations remained greater than the lower limit of quantitation for 18 and 7 days after IA administration of 200 and 100 mg of MPA, respectively. Maximum concentration and area under the observed concentration-time curve for MP in urine were significantly higher (approximately 10-and 17-fold, respectively) after administration of 200 versus 100 mg of MPA. Hydrocortisone concentration was below quantifiable limits for ≥ 48 hours in plasma and urine of all horses after administration of each MPA dose. Conclusions and Clinical Relevance-Pharmacokinetics of MP may differ among IA MPA dosing protocols, and MP may be detected in plasma and urine for a longer time than previously reported. This information may aid veterinarians treating sport horses. Further research is warranted to determine whether plasma HYD concentration can aid identification of horses that received exogenous glucocorticoids. 相似文献
27.
28.
29.
Quintal AP Ribeiro Ede S Rodrigues FP Rocha FS Floeter-Winter LM Nunes CM 《Veterinary parasitology》2011,176(2-3):112-119
Leishmaniasis is kept in nature by the participation of several animal species. This study evaluated the presence of Leishmania spp. in skin samples of free-ranging marsupials Micoureus paraguayanus (n=95) and Didelphis albiventris (n=191), captured in Morro do Diabo State Park and in sections of its surrounding forest, in the region of Pontal do Paranapanema, S?o Paulo State, Brazil. The samples were tested for the presence of kDNA of Leishmania spp. by polymerase chain reaction (PCR) and by real time PCR (qPCR). All samples from D. albiventris tested by PCR were negative for the presence of kDNA of Leishmania spp. However, when tested by qPCR, the positivity was 1.6%. A positivity of 7.4% by PCR and 11.6% by qPCR was observed for M. paraguayanus. Sixty-four per cent (9/14) of positive animals were limited to the same forest fragment. Presence of Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis was detected in M. paraguayanus samples. While D. albiventris is the most studied marsupial species due to its urban habits, other marsupial species such as M. paraguayanus can be potential reservoirs of Leishmania spp. and should also be studied. 相似文献
30.
Chen SJ Foster WR Jure-Kunkel MN Girit E Abraham R Hefta LJ Gao S Yonan CR Lin JH Dambach DM 《Veterinary immunology and immunopathology》2008,126(3-4):377-381
CD137 plays an important role as a co-stimulatory molecule in activated T cells. Agonistic CD137 specific antibodies have been investigated as therapeutic agents to promote tumor-specific immune responses by direct activation of T cells. As part of the pre-clinical pharmacological evaluation of cynomolgus monkeys, monkey CD137 was cloned and characterized. The deduced amino acid sequence encoded a full-length gene of 254 amino acids 95% identical to human CD137. Sequence variants identified in monkey CD137 include four splice variants lacking the transmembrane domain. These variants were detectable in human including two previously unreported variants. Two missense single nucleotide polymorphisms were detected present in 42 and 50% of 36 monkeys tested. In both monkey and human, mRNA expression of full-length CD137 and splice variants were significantly increased in peripheral blood mononuclear cells (PBMCs) upon stimulation by anti-CD3 antibodies. Recombinant monkey CD137 protein was bound with high affinity by an agonistic anti-human CD137 antibody but not by an anti-mouse CD137 antibody. In summary, compared to human, monkey CD137 showed distinct extracellular domain amino acid sequence and sequence polymorphisms. Thus, antibodies directed against epitopes in this extracellular domain could have differences in pharmacologic activity between cynomolgus monkeys and human or across individual cynomolgus monkeys. 相似文献