全文获取类型
收费全文 | 5470篇 |
免费 | 341篇 |
国内免费 | 205篇 |
专业分类
林业 | 284篇 |
农学 | 422篇 |
基础科学 | 67篇 |
949篇 | |
综合类 | 784篇 |
农作物 | 364篇 |
水产渔业 | 371篇 |
畜牧兽医 | 2126篇 |
园艺 | 132篇 |
植物保护 | 517篇 |
出版年
2023年 | 33篇 |
2022年 | 49篇 |
2021年 | 96篇 |
2020年 | 87篇 |
2019年 | 102篇 |
2018年 | 130篇 |
2017年 | 155篇 |
2016年 | 157篇 |
2015年 | 123篇 |
2014年 | 157篇 |
2013年 | 243篇 |
2012年 | 272篇 |
2011年 | 300篇 |
2010年 | 248篇 |
2009年 | 223篇 |
2008年 | 290篇 |
2007年 | 284篇 |
2006年 | 242篇 |
2005年 | 226篇 |
2004年 | 207篇 |
2003年 | 268篇 |
2002年 | 331篇 |
2001年 | 322篇 |
2000年 | 190篇 |
1999年 | 147篇 |
1998年 | 40篇 |
1997年 | 43篇 |
1996年 | 35篇 |
1995年 | 46篇 |
1994年 | 44篇 |
1993年 | 37篇 |
1992年 | 48篇 |
1991年 | 41篇 |
1990年 | 54篇 |
1989年 | 51篇 |
1988年 | 33篇 |
1987年 | 39篇 |
1986年 | 30篇 |
1985年 | 34篇 |
1984年 | 51篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1980年 | 23篇 |
1979年 | 28篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1975年 | 25篇 |
1974年 | 37篇 |
1972年 | 30篇 |
1971年 | 37篇 |
排序方式: 共有6016条查询结果,搜索用时 15 毫秒
991.
992.
Doolaege EH Raes K De Vos F Verhé R De Smet S 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(2):196-202
The absorption, distribution and elimination of carnosic acid, the main antioxidant found in rosemary was studied, in vivo, in rats. Therefore, carnosic acid was administrated in a single dose, intravenously (20.5 ± 4.2 mg/kg) and orally (64.3 ± 5.8 mg/kg),
to four and nine rats, respectively. Blood samples were collected at different time points, and plasma concentrations of carnosic
acid were determined using LC-MS. Furthermore, total collection of urine and feces was done during 4 h and 24 h for the intravenous
and oral administrations, respectively. After euthanizing the rats, intestinal content, liver and muscle tissue were sampled
to determine carnosic acid concentrations. The bioavailability of carnosic acid, after 360 min, was 40.1%. Traces of carnosic
acid were found in the rats intestinal content, liver and muscle tissue of abdomen and legs. The recovery of carnosic acid
in the feces, 24 h after oral administration, was 15.6 ± 8.2%. Carnosic acid is absorbed into the bloodstream after oral administration
in rats and is therefore bioavailable. It was found that carnosic acid in vivo is present in its free form and that its main elimination route is the fecal route. 相似文献
993.
994.
Isabel Guadano Procesi Azzurra Carnio Federica Berrilli Margherita Montalbano Di Filippo Alessia Scarito Cristina Amoruso Marco Barni Marco Ruffini Giulia Barlozzari Manuela Scarpulla Claudio De Liberato 《Zoonoses and public health》2022,69(1):46-54
Giardia duodenalis is the most common intestinal protozoan in humans and animals worldwide, including eight morphologically identical assemblages, infecting pets, livestock, wildlife and human beings. Assemblages A and B are those with the higher zoonotic potential, and they have been detected in several mammals other than humans; the others (C to H) show a higher host specificity. Cats can harbour both the specific Assemblage F and the zoonotic ones A and B. Several studies have been carried out on G. duodenalis genotypes in cats; however, the role of this species in the epidemiology of giardiasis is still poorly understood. In this scenario, the present study carried out the detection and genetic characterization at sub-assemblage level of G. duodenalis from colony stray cats in central Italy. In the period 2018–2019, 133 cat faecal samples were analysed for the presence of G. duodenalis cysts by a direct immunofluorescence assay. Positive samples were subsequently subjected to molecular analyses for assemblage/sub-assemblage identification. Forty-seven samples (35.3%) were positive for G. duodenalis cysts by immunofluorescence. G. duodenalis DNA was amplified at SSU-rDNA locus from 39 isolates: 37 were positive for zoonotic Assemblage A and 2 showed a mixed infection (A + B). Positive results for the β-giardin gene were achieved for 25 isolates. Sequence analysis revealed 16 isolates belonging to Sub-assemblage AII and 8 to Sub-assemblage AIII. One isolate resulted as ambiguous AI/AIII. Large sequence variability at the sub-assemblage level was detected, with several double peaks and mutations, making complex a proper isolate allocation. When compared with previous studies, the 35.3% prevalence of G. duodenalis in cats reported in the present article was surprisingly high. Moreover, all positive cats resulted to be infected with zoonotic assemblages/sub-assemblages, thus indicating stray cats as a possible source of human giardiasis and highlighting the sanitary relevance of cat colonies in the study area. 相似文献
995.
豆科与禾本科牧草间作的生长互作效应及对氮、磷养分吸收的影响 总被引:2,自引:0,他引:2
为了解牧草间作对作物生长和养分吸收的影响,以及为不同牧草优化配置、豆科和禾本科牧草间作提高结氮量提供理论依据,本试验采用随机区组试验设计,研究了间作对柱花草、扭黄茅和孔颖草的生物量和氮磷吸收的影响。结果表明,由于柱花草生物固氮,对扭黄茅和孔颖草养分吸收和生长有促进作用,与柱花草间作后的扭黄茅和孔颖草与禾本科牧草单作模式相比,能获得高的养分吸收量和产量。与各自单作对比,间作体系中的禾本科牧草生物量高于单作0.06%和26.78%;与柱花草单作对比,两个间作体系中的柱花草生物量低于单作9.70%和12.83%。扭黄茅与柱花草间作后,对氮磷的吸收量高于单作扭黄茅24.26%和35.18%,对氮磷的吸收量高于单作孔颖草40.64%和47.50%。相对于单作而言,柱花草分别与扭黄茅和孔颖草间作,对氮吸收量分别降低8.31%和28.94%,磷吸收量分别降低3.56%和20.58%。而且两种间作模式当量比均大于1,具有间作优势;柱花草/扭黄茅间作系统生产力、种间竞争能力高于柱花草/孔颖草,具有产量优势。在株行距为50 cm种植密度下,间作体系中禾本科牧草生长旺盛,柱花草的生长受到抑制,在与两个禾本科牧草间作中为弱竞争作物。结果表明,在合理的种植密度下,适合的牧草配置能够充分利用各种资源,促进种间有益作用,提高单位面积牧草产量和禾本科牧草氮磷的吸收,有利于改善牧草品质。 相似文献
996.
997.
Three horses with sudden onset severe lameness were admitted for further diagnostic investigation. All horses had variable changes on radiographs in the distal tarsal region. Because of the sudden onset and severe degree of lameness, a magnetic resonance imaging (MRI) examination was performed. All horses showed areas of increased signal intensity in short tau inversion recovery (STIR) images involving the central and/or third tarsal bones. These lesions involved both the subchondral bone and bone marrow and are currently defined as bone marrow lesions (BML). Two horses were treated with shockwave therapy, one received intra‐articular medication. Two of the horses returned to previous athletic level and one is still in rehabilitation. 相似文献
998.
999.
1000.
Roohparvar R Mehrabi R Van Nistelrooy JG Zwiers LH De Waard MA 《Pest management science》2008,64(7):685-693
BACKGROUND: The major facilitator superfamily (MFS) drug transporter MgMfs1 of the wheat pathogen Mycosphaerella graminicola (Fuckel) J Schroeter is a potent multidrug transporter with high capacity to transport strobilurin fungicides in vitro. The data presented in this paper indicate that, in addition to the predominant cause of strobilurin resistance, cytochrome b G143A subsititution, MgMfs1 can play a role in sensitivity of field strains of this pathogen to trifloxystrobin. RESULTS: In a major part of field strains of M. graminicola (collected in the Netherlands in 2004) containing the cytochrome b G143A substitution, the basal level of expression of MgMfs1 was elevated as compared with sensitive strains lacking the G143A substitution. Induction of MgMfs1 expression in wild-type isolates upon treatment with trifloxystrobin at sublethal concentrations proceeded rapidly. Furthermore, in disease control experiments on wheat seedlings, disruption mutants of MgMfs1 displayed an increased sensitivity to trifloxystrobin. CONCLUSION: It is concluded that the drug transporter MgMfs1 is a determinant of strobilurin sensitivity of field strains of M. graminicola. 相似文献