全文获取类型
收费全文 | 151篇 |
免费 | 31篇 |
专业分类
林业 | 3篇 |
农学 | 1篇 |
7篇 | |
综合类 | 32篇 |
农作物 | 2篇 |
水产渔业 | 3篇 |
畜牧兽医 | 120篇 |
园艺 | 1篇 |
植物保护 | 13篇 |
出版年
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1995年 | 2篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1958年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1947年 | 1篇 |
1942年 | 2篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1920年 | 1篇 |
排序方式: 共有182条查询结果,搜索用时 15 毫秒
71.
Biodiversity conservation and the eradication of poverty 总被引:3,自引:0,他引:3
Adams WM Aveling R Brockington D Dickson B Elliott J Hutton J Roe D Vira B Wolmer W 《Science (New York, N.Y.)》2004,306(5699):1146-1149
It is widely accepted that biodiversity loss and poverty are linked problems and that conservation and poverty reduction should be tackled together. However, success with integrated strategies is elusive. There is sharp debate about the social impacts of conservation programs and the success of community-based approaches to conservation. Clear conceptual frameworks are needed if policies in these two areas are to be combined. We review the links between poverty alleviation and biodiversity conservation and present a conceptual typology of these relationships. 相似文献
72.
Increased availability of commercially derived composts and problems with disposal of polyethylene mulch are factors which precipitated an investigation of the long term effects of organic and polyethylene film mulches on soils, plant growth, and yields. Three experiments were performed comparing polyethylene film mulch (PM) with mulches of commercial municipal solid waste compost (MW), dried sewage sludge (SS) and wood chips (WC). In 1990, bell pepper (Capsicum annum L.) plants on PM yielded 8.9 t'ha“1, which was significantly higher than the 1.9,4.6, and 7.2 t?ha?1 produced at MW compost rates of 13, 40 and 121 t?ha?1, respectively. Yields increased linearly with increasing rates of compost mulch. In spring, 1992, each organic material was applied at 224 and 336 t?ha?1 and winter (spaghetti) squash (Cucurbita pepo L.) was seeded. Soil moisture was higher under organic mulches than under PM. Soil temperatures in the mornings were not significantly different among mulches, but in the afternoons: SS>PM>MW>WC. Plants grown on PM had larger shoots and roots and produced more fruit per plant, but, because of plant losses to disease, had lower total yields than plants grown in MW and WC. Higher soil Na content occurred in MW plots and high electrical conductivity (EC) occurred in soils of SS plots. In fall, 1992, bell peppers transplanted into the same plots produced 4.7, 4.5, 3.3, and 2.7 t?ha?1 from PM, MW, WC, and SS, respectively. Soil tests detected higher NO3-N in WC plots, higher K in PM, higher Zn in MW, and lower Mn and higher Mg in SS plots, than in other treatments. Vegetables grown on PM produced higher fruit yields than those on organic mulches, however, plant losses to disease were also highest in PM plots. Environmental and economic considerations and governmental regulations may encourage organic mulch utilization by commercial vegetable growers. 相似文献
73.
A Ali AF Ahmed EE Mehana O El‐Tookhy A Al‐Hawas 《Reproduction in domestic animals》2013,48(2):e17-e19
A 10‐year‐old, clinically healthy, male dromedary camel had presented a history of progressive unilateral testicular enlargement over the past 5 years. The animal had mated with 32 females during that period; all had conceived. The sex ratio of his offspring was one male to 31 females. Ultrasound examination of the right testicle revealed a diffusely heterogeneous parenchyma with no identifiable normal testicular tissue. The enlarged testicle was surgically removed. Macroscopically, the testicle had a glistening pink surface and contained multiple soft, bulging nodules. Histopathologically, a well‐differentiated, diffuse seminoma was diagnosed. In conclusion, this study describes the fertility, sex ratio, clinical findings and ultrasonographic imaging in a male dromedary camel affected with unilateral testicular seminoma. 相似文献
74.
Abstract CASE HISTORY: Ovariohysterectomy was performed on an adult Cavalier King Charles Spaniel. The skin that had been clipped for surgery was noticed to be erythematous 8 days later. CLINICAL AND PATHOLOGICAL FINDINGS: Poorly defined patches containing multiple papules were visible bilaterally within the clipped skin. These became larger over the following 2 weeks, and samples were collected for histology. Seven days later, the lesions were multiple raised masses, up to 5 cm in diameter. Histology revealed numerous cup-shaped epidermal proliferations extending into the dermis. The presence of keratinocytes with increased quantities of blue-grey cytoplasm, and koilocytosis suggested papillomavirul infection; Canis familiaris papillomavirus (CfPV-2) DNA was amplified from two separate samples. Complete regression was observed 8 weeks after the lesions had been initially observed. DIAGNOSIS: Multiple inverted papilloma confined to skin that had been clipped for surgery. CLINICAL RELEVANCE: This is the first time that the development of canine cutaneous papillomas has been associated with surgery. The nature of the association between surgery and development of the papillomas is uncertain. However, it is possible that damage to superficial skin could promote the formation of papillomas. This is the first identification of CfPV-2 in New Zealand. 相似文献
75.
Thomas TM Marcellin-Little DJ Roe SC Lascelles BD Brosey BP 《American journal of veterinary research》2006,67(12):1974-1979
OBJECTIVE: To compare measurements obtained by use of a universal plastic goniometer (UG) and an electrogoniometer (EG) and from radiographs and to compare joint motion in German Shepherd Dogs and Labrador Retrievers. ANIMALS: 12 healthy adult German Shepherd Dogs and data previously collected from 16 healthy adult Labrador Retrievers. PROCEDURES: German Shepherd Dogs were sedated. One investigator then measured motion of the carpal, cubital (elbow), shoulder, tarsal, stifle, and hip joints of the sedated dogs. Measurements were made in triplicate with a UG and an EG. Radiographs were taken of all joints in maximal flexion and extension. Values were compared between the UG and EG and with values previously determined for joints of 16 Labrador Retrievers. RESULTS: An EG had higher variability than a UG for all dogs. The EG variability appeared to result from the technique for the EG. German Shepherd Dogs had lower values in flexion and extension than did Labrador Retrievers for all joints, except the carpal joints. German Shepherd Dogs had less motion in the tarsal joints, compared with motion for the Labrador Retrievers, but had similar motion in all other joints. CONCLUSIONS AND CLINICAL RELEVANCE: A UG is reliable for obtaining measurements in German Shepherd Dogs. There was higher variability for the EG than for the UG, and an EG cannot be recommended for use. 相似文献
76.
77.
78.
FTV Pereira FC Braga KC Burioli JR Kfoury Jr LJ Oliveira PC Papa AF Carvalho CE Ambrósio FW Bazer MA Miglino 《Reproduction in domestic animals》2010,45(5):907-914
The objectives of this investigation were to understand transplacental transport of iron by secreted uteroferrin (UF) and haemophagous areas of water buffalo placenta and clarify the role(s) of blood extravasation at the placental‐maternal interface. Placentomes and interplacentomal region of 51 placentae at various stages of gestation were fixed, processed for light and transmission electron microscopy, histochemistry and immunohistochemistry. Haemophagous areas were present in placentomes collected between 4 and 10 months of pregnancy. Perl’s reaction for ferric iron was negative in placentomes, but positive in endometrial glands. Positive staining for UF indicated areas in which it was being taken up by phagocytosis and/or fluid phase pinocytosis in areolae of the interplacentomal mesenchyme, with little staining in endometrial stroma. Imunohistochemistry detected UF in trophectoderm of haemophagous regions of placentomes and in other parts of the foetal villous tree, but the strongest immunostaining was in the epithelial cells and lumen of uterine glands. Ultrastructural analyses indicated that erythrophagocytosis was occurring and that erythrocytes were present inside cells of the chorion that also contained endocytic vesicles and caveolae. Results of this study indicate that both the haemophagous areas of placentomes and the areolae at the interface between chorion and endometrial glands are important sites for iron transfer from mother to foetal‐placental tissues in buffalo throughout pregnancy. 相似文献
79.
80.
A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10 degrees and 50 degreesC. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI. 相似文献