全文获取类型
收费全文 | 5652篇 |
免费 | 234篇 |
国内免费 | 8篇 |
专业分类
林业 | 482篇 |
农学 | 207篇 |
基础科学 | 51篇 |
1324篇 | |
综合类 | 733篇 |
农作物 | 248篇 |
水产渔业 | 357篇 |
畜牧兽医 | 1893篇 |
园艺 | 170篇 |
植物保护 | 429篇 |
出版年
2023年 | 28篇 |
2022年 | 52篇 |
2021年 | 97篇 |
2020年 | 111篇 |
2019年 | 138篇 |
2018年 | 106篇 |
2017年 | 125篇 |
2016年 | 130篇 |
2015年 | 92篇 |
2014年 | 145篇 |
2013年 | 263篇 |
2012年 | 319篇 |
2011年 | 393篇 |
2010年 | 247篇 |
2009年 | 202篇 |
2008年 | 344篇 |
2007年 | 341篇 |
2006年 | 358篇 |
2005年 | 357篇 |
2004年 | 317篇 |
2003年 | 293篇 |
2002年 | 306篇 |
2001年 | 76篇 |
2000年 | 70篇 |
1999年 | 86篇 |
1998年 | 66篇 |
1997年 | 54篇 |
1996年 | 52篇 |
1995年 | 44篇 |
1994年 | 27篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 35篇 |
1990年 | 38篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 35篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1974年 | 16篇 |
1973年 | 18篇 |
1972年 | 14篇 |
排序方式: 共有5894条查询结果,搜索用时 15 毫秒
31.
32.
Mastrorilli C Spangler EA Christopherson PW Aubry OA Newton JC Smith AN Kennis RA Weismann JL Moore PF 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2012,41(3):412-418
A 9‐month‐old male Great Dane had progressive generalized nodular dermatopathy for several months. There were > 100 raised, alopecic, firm, painful nodules throughout the skin. Aspirates from several lesions yielded moderate numbers of irregularly round or polygonal to spindle‐shaped cells with mild to moderate anisocytosis and few inflammatory cells, and the cytologic interpretation was proliferation of mesenchymal or histiocytic cells. On histopathologic examination, nodules were composed of densely packed sheets of round to spindle‐shaped cells with mild anisokaryosis and low mitotic activity. Multifocal histiocytic sarcoma with a spindle‐cell pattern was diagnosed based on morphologic features and intense expression of CD18. Additional immunophenotypic analysis on frozen sections of tissue confirmed the diagnosis of histiocytic sarcoma; expression of CD18, CD45, CD1a, CD11b, and CD11c, limited expression of Thy‐1 (CD90) and CD80, and lack of expression of CD4, CD11d, and CD86 indicated that the cells were likely interstitial dendritic cells; a review of reactive and neoplastic dendritic cells is provided. Based on staging, internal organs were not affected. Sequential treatment with lomustine and doxorubicin failed to prevent progression of the cutaneous lesions, and the dog died 3 months after initial diagnosis. At necropsy, a focus of neoplastic cells was present in one lymph node, but except for skin other organs were not involved. The clinical presentation of histiocytic sarcoma may be unusual, and neoplastic cells may lack overt features of malignancy on cytologic and histopathologic examination. In some instances, immunophenotyping is required to differentiate histiocytic sarcoma from other histiocytic disorders. 相似文献
33.
Hanley CS MacWilliams P Giles S Paré J 《The Canadian veterinary journal. La revue veterinaire canadienne》2006,47(10):1015-1017
A domestic ferret was presented for episodic regurgitation. Cytologic examination and culture of an enlarged submandibular lymph node revealed Cryptococcus neoformans variety grubii (serotype A). The ferret was successfully treated with itraconazole. This is the first documented case of Cryptococcus neoformans variety grubii in a ferret in the United States. 相似文献
34.
35.
We here describe the transmission of the pig roundworm, Ascaris suum to chimpanzees maintained in the Copenhagen Zoo, Denmark. Using a technique for whole genome fingerprinting, amplified fragment length polymorphism (AFLP) and the technique PCR restricted fragment length polymorphism (PCR-RFLP) of the internal transcribed spacer region (ITS) of the nuclear ribosomal DNA, the worms from the chimpanzees were compared with Ascaris spp obtained from humans and pigs in order to identify the source of the infection. By the use of different distance and clustering based methods on the AFLP data set the worms from the chimpanzees were assigned to the same cluster as that of the worms from pigs. The PCR-RFLP analysis supported the AFLP results. Therefore, the zoo chimpanzees have required Ascaris infections by cross-infection from pigs. Pigs as a potential source of Ascaris infections for both captive and wild chimpanzees and other animals, therefore needs to be considered and appropriate steps taken to prevent such infection. 相似文献
36.
37.
38.
Peter B. Best 《African Zoology》2013,48(2):177-179
The catch per unit effort of Oreochromis mossambicus, Clarias gariepinus and Cyprinus carpio at different localities at Hartbeespoort Dam was investigated. Catches of the three species were between three and ten times higher on the southern shore of the lake than on the northern shore. The gradient of each locality was found to be the most important variable determining catch. Gill-net catches of O. mossambicus from littoral and limnetic stations indicated equal abundance of the species in these two habitats. The implications of the results for improved predictions of fish yield from lakes, and for management are discussed. 相似文献
39.
Peter B. Best 《African Zoology》2013,48(2):181-185
For most of the year, Meyer’s parrots in the Okavango Delta do not form large feeding flocks, and groups larger than two or three are probably the result of opportunistic aggregation at favoured food items after dispersion from communal roosts. Communal roosting likely does not facilitate flocking unless the food resources are close to the roost site, but may function in anti-predator defence. Meyer’s parrots appear to be dependent on riverine forest, Acacia-Combretum marginal woodland and mopane woodland for roost sites in the Okavango Delta. They aggregated more during the breeding season due to their specialist nutritional requirements, and female dependence on food provisioning by the male parrots. Meyer’s parrots may be sedentary in the Okavango Delta, but the possibility of limited local movements in other areas (especially the Zimbabwean highlands) should be investigated. 相似文献
40.
Sara Granström Christian Bressen Pipper Rasmus Møgelvang Peter Sogaard Jakob Lundgren Willesen Jørgen Koch 《Journal of Veterinary Cardiology》2012,14(4):479-488
ObjectivesThe aims of this study were to compare the effect of sample volume (SV) size settings and sampling method on measurement variability and peak systolic (s′), and early (e′) and late (a′) diastolic longitudinal myocardial velocities using color tissue Doppler imaging (cTDI) in cats.AnimalsTwenty cats with normal echocardiograms and 20 cats with hypertrophic cardiomyopathy.MethodsWe quantified and compared empirical variance and average absolute values of s′, e′ and a′ for three cardiac cycles using eight different SV settings (length 1,2,3 and 5 mm; width 1 and 2 mm) and three methods of sampling (end-diastolic sampling with manual tracking of the SV, end-systolic sampling without tracking, and random-frame sampling without tracking).ResultsNo significant difference in empirical variance could be demonstrated between most of the tested SVs. However, the two settings with a length of 1 mm resulted in a significantly higher variance compared with all settings where the SV length exceeded 2 mm (p < 0.001). There was an overall significant effect of sampling method on the variability of measurements (p = 0.003) and manual tracking obtained the lowest variance. No difference in average values of s′, e′ or a′ could be found between any of the SV settings or sampling methods.ConclusionWithin the tested range of SV settings, an SV length of 1 mm resulted in higher measurement variability compared with an SV length of 3 and 5 mm, and should therefore be avoided. Manual tracking of the sample volume is recommended. 相似文献