全文获取类型
收费全文 | 516篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
林业 | 36篇 |
农学 | 17篇 |
基础科学 | 4篇 |
163篇 | |
综合类 | 17篇 |
农作物 | 29篇 |
水产渔业 | 43篇 |
畜牧兽医 | 162篇 |
园艺 | 20篇 |
植物保护 | 64篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 13篇 |
2017年 | 20篇 |
2016年 | 16篇 |
2015年 | 3篇 |
2014年 | 12篇 |
2013年 | 38篇 |
2012年 | 32篇 |
2011年 | 45篇 |
2010年 | 17篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 37篇 |
2006年 | 26篇 |
2005年 | 30篇 |
2004年 | 28篇 |
2003年 | 13篇 |
2002年 | 23篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1963年 | 2篇 |
1961年 | 1篇 |
排序方式: 共有555条查询结果,搜索用时 31 毫秒
71.
Lucia Prellwitz Fabiana Nunes Zambrini Jos Domingos Guimares Marco Antonio Paula de Sousa Maria Emília Franco Oliveira Alexandre Rosetto Garcia Srgio Novita Esteves Pawel Mieczyslaw Bartlewski Joanna Maria Gonalves Souza‐Fabjan Jeferson Ferreira Fonseca 《Reproduction in domestic animals》2019,54(9):1230-1235
This study compared the effects of intravaginal and intravenous routes of oxytocin (OT) administration in 46 oestrous‐induced Santa Inês ewes (6‐day treatment with progestin‐releasing intravaginal sponges and a single injection of 200 IU of eCG at the time of sponge removal) that underwent transcervical embryo recovery 6–7 days after oestrous onset and mating. All ewes received 37.5 μg of d‐cloprostenol via latero‐vulvar route, and 1 mg of oestradiol benzoate i.m. 16 hr before and 50 IU of OT 20 min before non‐surgical embryo recovery (NSER), with OT being administered intravenously (n = 21) or intravaginally (n = 21). An overall oestrous response was 95.6% (44/46), and adequate cervical retraction could be accomplished in 78.6% (33/42) of ewes. The percentage of successful NSER procedures was 57% (24/42) or 72.7% (24/33) of animals with sufficient cervical retraction. The duration of NSER procedure averaged 28 min (range: 17–40 min) and ~96% of flushing fluid could be recovered (range: 85%–100%). Out of 18 ewes that could not undergo NSER, 12 (66.6%) presented various anatomical barriers, whilst the other 33.4% did not present these barriers and still could not be traversed. Excluding the ewes with those anatomical features, the overall success rate of NSER was 80% (24/30). The route of OT administration had no effect on NSER efficiency or the ease with which transcervical embryo flushing was performed. Both routes of OT administration can be used for cervical dilation protocol. Discarding ewes with anatomical features precluding cervical penetration is highly recommended to increase the efficacy of NSER in sheep. 相似文献
72.
Leandro G. Franco Carlos Henrique M. Wilges Daniel P. Junior Sofia A. Cerejo Lilian T. Nishimura Isabela P. Bittar 《Veterinary anaesthesia and analgesia》2018,45(3):250-259
Objective
To evaluate the effects of ketamine continuous rate infusions (CRI) at two dose rates on cardiovascular function and serum creatine kinase MB isoenzyme (CK-MB) and troponin I in healthy conscious dogs.Study design
Experimental, prospective, crossover, randomized, blinded study.Animals
Eight adult mixed-breed dogs, aged 6 ± 1 years and weighing 19 ± 8.6 kg (mean ± standard deviation).Methods
Dogs were administered an intravenous bolus of ketamine (0.5 mg kg?1) followed by a ketamine CRI for 12 hours (20 μg kg?1 minute?1; treatment TC20 or 40 μg kg?1 minute?1; treatment TC40). Sedation, heart rate (HR), mean arterial pressure (MAP), electrocardiographic and echocardiographic parameters were evaluated at baseline (T0) and 1 (T1), 2 (T2), 4 (T4), 8 (T8), 12 (T12) and 24 (T24) hours after ketamine infusion started. Serum concentrations of CK-MB and troponin I were measured at baseline and 12, 24 and 48 hours after infusion started.Results
HR increased over the first 4 hours, significantly at T1 in TC20 and at T4 in TC40 when compared with T0 (p < 0.05). MAP was significantly increased at T2 in TC40 when compared with TC20. Behavioral changes, such as stereotypical head movements and twitches, occurred within 4 hours in TC40. There were no significant changes in echocardiographic examinations in any dog when compared with baseline. There were no temporal changes in serum CK-MB activity either within or between treatments (p > 0.05). No troponin I was detected in any sample.Conclusions and clinical relevance
No indication of myocardial injury resulting from ketamine infusion was detected in this study in healthy dogs. Further studies are needed to assess the ketamine infusion effects on antinociception and other organ function not evaluated in the present study. 相似文献73.
Inteeworn N Ohlerth S Höpfl G Guscetti F Bley CR Wergin MC Roos M Gassmann M Kaser-Hotz B 《Veterinary journal (London, England : 1997)》2007,173(3):564-570
PTK787/ZK 222584 is an inhibitor of the vascular endothelial growth factor (VEGF) receptor tyrosine kinases. In this study, the effectiveness of PTK787/ZK 222584 and radiation on canine oral melanoma xenografts was assessed. Xenografts were treated with radiotherapy (4x6Gy), or with PTK787/ZK 222584, or with a combination of both. Treatment efficacy was assessed using a tumour growth delay assay, serial power Doppler and pO(2) measurements during and after therapy. There was a significant growth delay for the group treated with radiation alone and for the combined treatment group. However, tumour growth delay was similar in both groups. Tumours were hypoxic before irradiation and no significant re-oxygenation occurred during therapy. In all tumours, vascularity and perfusion were significantly lower at the end of the study but no significant differences in perfusion, vascularity and oxygenation status were observed between and within treatment groups. The combination of PTK787/ZK 222584 and radiotherapy did not perform better than radiotherapy alone in this model. 相似文献
74.
75.
Milagros R. de la Peña Annie Villa Franco Hermoso P. IgcasanJr Mary Dianne Grace N. Arnaldo Ramil M. Piloton Soledad S. Garibay Vicente T. Balinas 《Aquaculture International》2018,26(4):1119-1134
The optimum culture conditions of the local strain Chaetoceros calcitrans were determined to improve biomass and reduce cost of production. Under outdoor culture conditions, higher cell density was attained when the cultures were enriched with Tungkang Marine Research Laboratory (TMRL) medium composed of cheap technical grade reagents and cultured at 25 g L?1 salinity. The cultures were lighted with two 40 W cool-white GE fluorescent tubes (24–35 μmol photon m?2 s?1). Using semi-continuous culture system under established optimum culture conditions, C. calcitrans can be re-cultured thrice and concentrated at each culture cycle using electrolytic flocculation method to produce 4.6 kg m?3 of diatom paste. The viability of concentrated C. calcitrans after 3 months of storage was comparable to live diatom cells. Simple preservation technique by low-temperature storage is convenient for storing algal concentrates for use as starter cultures and for feeding invertebrates. The paste costs USD 8.24 kg?1 inclusive of the assets and flocculation materials for culturing and harvesting the diatom, respectively. This study established the suitable conditions for mass culture of C. calcitrans and produced concentrated diatoms in paste form that is readily available for aquaculture hatcheries at a lower cost. 相似文献
76.
77.
78.
UV curing of perfluoro-alkyl-polyacrylate resins able to impart water as well as oil-repellency to cotton fabrics was studied
in comparison with conventional thermal polymerization. The process was assessed through weight gain and gel content measurements
while the properties conferred to cotton fabrics were determined in terms of water and oil contact angles, moisture adsorption,
and water vapor permeability. The polymerization yields were of the same order (>80 %) of those obtained with thermal curing
as well as the high contact angles with water (>127°) and oil (>118°) even at low resin add-on (3 %). UV cured resins yielded
oil contact angles mostly higher than 120° denoting super oil-repellent surfaces. Moreover the water and oil-repellency was
adequately maintained after washing. The moisture adsorption of finished fabrics was lower than that of untreated cotton,
but slightly higher for UV cured than thermally treated fabrics. Water vapor transmission rate showed that the finish treatment,
thermal as well as by UV curing, does not reduce the breathability of the original cotton. DSC analysis demonstrated that
the fiber pyrolysis is affected by the polymer add-on, while FTIR-ATR spectra of all finished fabrics showed typical peaks
of ester and C-F groups. XPS analysis showed small differences between thermal and UV curing coatings with each resin, while
coatings with the lowest percentage of fluorine groups did not affect the water and oil-repellency. 相似文献
79.
The savannah of central Brazil occupies 208 million ha, of which about 54 million ha have been converted to cultivated pasture. The aim of this study was to provide the dynamics of evapotranspiration (ET) in a Brachiaria brizantha cultivated pasture in the Brazilian Savannah region at the beginning of the rainy season and determine biological and environmental factors that influence ET by using the decoupling approach. A meteorological station and an eddy covariance system were placed at the studied site. The above‐ground biomass production of the B. brizantha pasture responded rapidly to the onset of the rainy season. Leaf area index (LAI) increased from 0·4 to 1·1 between 15 November and 3 December, with a corresponding increase in live biomass. Average ET during the study period was 2·6 ± 0·9 mm. Daily ET was significantly correlated with maximum vapour pressure deficit and precipitation. The average of daytime decoupling factor obtained over 2 d without rain was 0·50 ± 0·06. The B. brizantha pasture deployed in this region showed an intermediate coupling which takes ET to be influenced by both atmospheric conditions and by the available radiation at the canopy. 相似文献
80.
Omar Varela Mariana Varas Donna Rattalino Franco Crabbè Mariano Ordano 《Arid Land Research and Management》2017,31(4):418-430
In deserts, shrubs determine landscape structure and influence plant productivity by creating nutrient-enriched environments. Attributes vary among shrub species, thus their contribution to soil characteristics is expected to vary as well, and nutrient input under shrub cover will depend on species attributes. We propose that plant size determines the contribution to soil chemical characteristics. Therefore, the contribution of larger species will be higher than smaller ones. Also, each species will contribute differentially for each chemical parameter. To corroborate these premises, we measured six soil chemical characteristics in areas covered by shrubs and in bare soil, as well as among five nurse species, in four sites of the Monte desert (La Rioja, Argentina). A multivariate analysis of variance (MANOVA) indicated significant variation between cover conditions and locations. Supporting previous studies, the presence of shrubs improved soil properties. Chemical concentration between soils under shrubs and bare soils, respectively, showed as mean and (SD) were: carbon(%): 0.82 (0,47), 0.52 (0.22); nitrates (ppm): 33,33 (67,36), 2.63 (0.56); phosphorous(ppm): 16.76 (25.02), 6.56 (1.92); electrical conductivity (dS m?1): 0.24 (0,43), 0.03 (0,02); pH: 6.93 (0.56), 7.62 (0.53); and water content (%): 3,17 (8.94), 2.47 (9.15). Chemical characteristics also varied according to the nurse species. Larger nurse species affected the ensemble of chemical characteristics, after controlling for cover condition and site. Larger plant species (Bulnesia retama, Prosopis torquata, and Zuccagnia punctata) were significantly associated with higher carbon and higher nitrates concentration. These results suggest that soil properties are enhanced by the size of nurse plant species. 相似文献