全文获取类型
收费全文 | 9725篇 |
免费 | 640篇 |
国内免费 | 50篇 |
专业分类
林业 | 638篇 |
农学 | 489篇 |
基础科学 | 82篇 |
1831篇 | |
综合类 | 651篇 |
农作物 | 473篇 |
水产渔业 | 801篇 |
畜牧兽医 | 4412篇 |
园艺 | 133篇 |
植物保护 | 905篇 |
出版年
2023年 | 86篇 |
2022年 | 148篇 |
2021年 | 284篇 |
2020年 | 283篇 |
2019年 | 340篇 |
2018年 | 361篇 |
2017年 | 365篇 |
2016年 | 372篇 |
2015年 | 262篇 |
2014年 | 364篇 |
2013年 | 576篇 |
2012年 | 600篇 |
2011年 | 616篇 |
2010年 | 316篇 |
2009年 | 339篇 |
2008年 | 501篇 |
2007年 | 482篇 |
2006年 | 441篇 |
2005年 | 400篇 |
2004年 | 374篇 |
2003年 | 329篇 |
2002年 | 372篇 |
2001年 | 266篇 |
2000年 | 253篇 |
1999年 | 216篇 |
1998年 | 64篇 |
1997年 | 63篇 |
1996年 | 60篇 |
1995年 | 55篇 |
1994年 | 38篇 |
1993年 | 41篇 |
1992年 | 86篇 |
1991年 | 62篇 |
1990年 | 62篇 |
1989年 | 67篇 |
1988年 | 64篇 |
1987年 | 52篇 |
1986年 | 48篇 |
1985年 | 60篇 |
1984年 | 37篇 |
1983年 | 45篇 |
1982年 | 32篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 24篇 |
1977年 | 23篇 |
1974年 | 23篇 |
1973年 | 29篇 |
1972年 | 25篇 |
1970年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Simões-Mattos L Mattos MR Teixeira MJ Oliveira-Lima JW Bevilaqua CM Prata-Júnior RC Holanda CM Rondon FC Bastos KM Coêlho ZC Coêlho IC Barral A Pompeu MM 《Veterinary parasitology》2005,127(3-4):199-208
Over the last few years, several cases of feline leishmaniasis (FL) with cutaneous and visceral forms have been reported around the world. Nonetheless, the real susceptibility of cats to infection with Leishmania spp. and the outcome of leishmaniasis in these animals are poorly understood. Experimental studies on feline models will contribute to the knowledge of natural FL. Thus, in order to determine the susceptibility of domestic cats (Felis catus) to experimental infection with Leishmania braziliensis, 13 stray cats were infected with 10(7) promastigotes by the intradermal route in the ear and nose simultaneously and followed up for 72 weeks. Soon after infection, the earliest indication of a lesion was a papule on the ear at 2 weeks post-infection (w.p.i.). The emergence of satellite papules around the primary lesion was observed about 4 w.p.i. Two weeks later these papules coalesced and formed a huge and irregular nodule. Thereafter, there was lesion dissemination to the external and marginal surface of the ipsilateral ear, and later to the contralateral ear. At 10 w.p.i., some nodules became ulcerated. Nose lesions presented a similar evolution. At both sites, the largest lesion sizes occurred at 10 w.p.i. and started to decrease 15 days later. Ear and nose nodules healed at 32 and 40 w.p.i., respectively. Specific L. braziliensis IgG antibody titers (optical density> or = 0.01 as positive result) were detected as early as 2 w.p.i. (0.09 +/- 0.02) in only three animals (23%), and all cats had positive titers at 20 w.p.i. (0.34 +/- 0.06). Only three animals (38%) continued to show positive serology at 72 w.p.i. (0.08 +/- 0.02). Up to that time, none of the cats had lesion recurrence. In a feline model of cutaneous leishmaniasis, it seems that there is no correlation between active lesions and positive serology. The implications of these data are discussed. 相似文献
982.
Saito KC Bechara GH Nunes ET de Oliveira PR Denardi SE Mathias MI 《Veterinary parasitology》2005,129(3-4):299-311
This study presents the morphology of the ovary, as well as the dynamics of the vitellogenesis process in oocytes of the cattle-tick Boophilus microplus. The ovary of these individuals is of the panoistic type; therefore, it lacks nurse cells. This organ consists of a single tubular structure, continuous, and composed of a lumen delimitated by a wall of small epithelial cells with rounded nuclei. In this tick species, the oocytes were classified into six stages varying from I to VI and according to: cytoplasm appearance and presence of the germ vesicle, yolk granules, and chorion. Oocytes of various sizes and at different developmental stages remain attached to the ovary through a cellular pedicel until completing stage V. Afterwards, they are liberated into the lumen and from there to the exterior. Some oocytes (classified as type VI) showed an atypical appearance indicating that some of the cellular components would be undergoing a degenerative process and/or reabsorption. 相似文献
983.
Barger A Graca R Bailey K Messick J de Lorimier LP Fan T Hoffmann W 《Veterinary pathology》2005,42(2):161-165
Aspiration of lytic bone lesions is an excellent diagnostic test in the initial evaluation of primary bone neoplasia. However, cytologically, it can be difficult to differentiate osteosarcoma (OSA) from other bone neoplasms, including fibrosarcoma, chondrosarcoma, synovial cell sarcoma, and plasma cell myeloma. The purpose of this study is to determine the sensitivity and specificity of alkaline phosphatase (ALP) staining to differentiate OSA from other tumors that express vimentin by immunocytochemistry or immunohistochemistry. ALP is a hydrolytic enzyme present in multiple tissues including liver, kidney, intestine, placenta, and bone. Hypothetically, neoplasms actively producing bone should be specifically positive for ALP staining. Unstained, cytologic specimens were incubated for 8-10 minutes with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indolyl phosphate toluidine salt-phosphatase substrate. A positive reaction stains the membrane of the cells gray to black. Samples were counterstained with a Romanowsky's stain to determine whether the sample was of representative cellularity. A total of 61 vimentin-positive neoplasms have been evaluated and confirmed histopathologically. Tumors that expressed vimentin and were positive for ALP included 33 OSAs, one multi-lobular tumor of bone, one amelanotic melanoma, and one chondrosarcoma. Tumors that expressed vimentin and were negative for ALP included chondrosarcomas (three of four), multiple fibrosarcomas, and multiple synovial cell sarcomas. The sensitivity is 100%, and the specificity is 89%. In conclusion, ALP appears to be a highly sensitive and fairly specific marker in the diagnosis of OSA. 相似文献
984.
Weiss DJ Evanson OA de Souza C Abrahamsen MS 《American journal of veterinary research》2005,66(4):721-726
OBJECTIVES: To evaluate the role of interleukin (IL)-10 in the inability of monocyte-derived bovine macrophages to kill Mycobacterium avium subsp paratuberculosis organisms in vitro. SAMPLE POPULATION: Monocytes were obtained from healthy adult Holstein dairy cows that had negative results when tested for infection with M avium subsp paratuberculosis. PROCEDURE: Monocyte-derived macrophages were incubated with M avium subsp paratuberculosis for 2, 6, 24, 72, or 96 hours with or without addition of saturating concentrations of a goat anti-human IL-10 that has been documented to neutralize bovine IL-10 activity. Variables assessed included ingestion and killing of M avium subsp paratuberculosis; expression of tumor necrosis factor (TNF)-alpha, IL-12, IL-8, major histocompatability (MHC) class II, vacuolar H+ ATPase, and B cell CLL/lymphoma 2 (BCL-2); production of nitric oxide; acidification of phagosomes; and apoptosis of macrophages. RESULTS: Neutralization of IL-10 enabled macrophages to kill 57% of M avium subsp paratuberculosis organisms within 96 hours. It also resulted in an increase in expression of TNF-alpha, IL-12, IL-8, MHC class II, and vacuolar H+ ATPase; decrease in expression of BCL-2; increase in acidification of phagosomes; apoptosis of macrophages; and production of nitric oxide. CONCLUSIONS AND CLINICAL RELEVANCE: The capacity of M avium subsp paratuberculosis to induce IL-10 expression may be a major determinant of virulence for this organism. 相似文献
985.
OBJECTIVE: To evaluate the use of subdermal plexus skin flaps for closing defects after excision of cutaneous and subcutaneous tumors in dogs and to compare outcome of flaps secured with sutures and those secured with butyl-cyanoacrylate and intermittent sutures. STUDY DESIGN: Clinical study. ANIMALS: Fifteen dogs. METHODS: After excision of cutaneous or subcutaneous tumors the skin defect was reconstructed by random flaps based on the subdermal plexus. Flap skin edges were apposed with simple interrupted 4-0 monofilament nylon sutures (group 1; 5 dogs) or nylon sutures alternated with butyl-cyanoacrylate adhesive (group 2; 10 dogs). Flaps were evaluated every 48 hours when bandages were changed, until complete healing. RESULTS: Random flaps based on the subdermal plexus were effectively used to close wound defects; mean flap survival was 89%. Partial flap necrosis occurred in 4 dogs. Wound margins apposed with butyl-cyanoacrylate had thinner and more esthetic scars than sutured margins. CONCLUSION: Random flaps based on the subdermal plexus proved to be versatile for covering limb wounds after excision of cutaneous or subcutaneous tumors. Mean survival rate was comparable to that reported for axial pattern flaps. Butyl-cyanoacrylate adhesive was easy to apply, allowed accurate margin apposition with good cosmetic outcome and reduced sutures needed. CLINICAL RELEVANCE: Cyanoacrylate adhesive should be considered in lieu of suture closure to secure random skin flaps based on the subdermal plexus in dogs. 相似文献
986.
987.
988.
989.
G. T. N. de Leeuw 《European journal of plant pathology / European Foundation for Plant Pathology》1972,78(3):107-109
Samenvatting Bladeren vanHyoscyamus niger planten vertoonden chlorotische lokale lesies 7 dagen na inoculatie met sap van mozaïekziekeHippeastrum-planten. Met sap vanHippeastrum-planten zonder mozaïeksymptomen werd geen reactie verkregen. In dooppreparaten gemaakt van chlorotische lesies inHyoscyamus-bladeren en van bladeren vanHippeastrum planten met mozaïeksymptomen werden draadvormige virusdeeltjes van 648–772 nm aangetroffen. Het virus kon met sap geperst uit geïnoculeerdeHyoscyamus-planten weer op gezondeHippeastrum-planten worden overgebracht. 相似文献
990.