全文获取类型
收费全文 | 3884篇 |
免费 | 242篇 |
国内免费 | 2篇 |
专业分类
林业 | 332篇 |
农学 | 80篇 |
基础科学 | 17篇 |
670篇 | |
综合类 | 643篇 |
农作物 | 168篇 |
水产渔业 | 359篇 |
畜牧兽医 | 1482篇 |
园艺 | 120篇 |
植物保护 | 257篇 |
出版年
2023年 | 40篇 |
2022年 | 59篇 |
2021年 | 101篇 |
2020年 | 126篇 |
2019年 | 155篇 |
2018年 | 149篇 |
2017年 | 115篇 |
2016年 | 134篇 |
2015年 | 94篇 |
2014年 | 141篇 |
2013年 | 201篇 |
2012年 | 262篇 |
2011年 | 324篇 |
2010年 | 170篇 |
2009年 | 155篇 |
2008年 | 262篇 |
2007年 | 265篇 |
2006年 | 221篇 |
2005年 | 205篇 |
2004年 | 186篇 |
2003年 | 195篇 |
2002年 | 145篇 |
2001年 | 31篇 |
2000年 | 20篇 |
1999年 | 37篇 |
1998年 | 27篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1971年 | 6篇 |
1928年 | 5篇 |
1925年 | 6篇 |
1924年 | 6篇 |
排序方式: 共有4128条查询结果,搜索用时 125 毫秒
91.
92.
93.
Hlne Amory DVM PhD Dip. ECEIM Daniel Jean DMV MSc PhD Dip. ACVIM R. Leveille DVM Dip. ACVR Robert Higgins DVM MSc DSc Andr Vrins DVM 《Journal of Equine Veterinary Science》2006,26(8):364-369
Retropharyngeal infections in horses normally induce local painful swelling of the retropharyngeal area, which may lead to dyspnea, dysphagia, and systemic manifestations. Differential diagnosis of local painful swelling of the retropharyngeal area includes retropharyngeal lymph node infection, neoplasm, cellulitis, hematoma, guttural pouch empyema, parotiditis, and jugular thrombosis. Apart from Streptococcus equi ssp. equi, other bacteria are rarely reported as a cause of retropharyngeal abscesses. The reason for this might be a lack of specific sampling to identify the causative agent. This work deals with a case of retropharyngeal infection in an 11-year-old Standardbred stallion with acute depression, fever, tachycardia, asymmetric painful swelling in the throat area, ptyalism, and respiratory distress. Endoscopy, radiography, ultrasonography, blood analysis, and cytological examination of a puncture sample taken from the throat mass were consistent with a pyogenic to pyogranulomatous retropharyngeal inflammation. The clinical evolution was initially satisfactory in response to treatment with nonsteroidal anti-inflammatory drugs and antibiotics, but clinical signs relapsed twice, each time a few weeks after cessation of antibiotic therapy. The bacteriologic finding in this case was unusual and consisted of the isolation of a Pasteurella multocida strain that was obtained after the second relapse (ie, 79 days after initial admission), using a brain heart infusion (BHI) medium, and after two successive negative bacteriological cultures performed on day one of clinical signs and at the first relapse of clinical signs, respectively. 相似文献
94.
Francisco J. Escobedo David J. Nowak John E. Wagner Carmen Luz De la Maza Manuel Rodríguez Daniel E. Crane Jaime Hernndez 《Urban Forestry & Urban Greening》2006,4(3-4):105-114
Santiago, Chile's semi-arid climate and urbanized environment poses a severe limitation for the establishment and maintenance of urban forests. Municipalities, or comunas, are the main stakeholders in the management of Santiago's public urban forests. A tenable hypothesis would be that as the socioeconomic level of a comuna increases, the better the condition of a comuna's urban forest. Unfortunately, there is little comprehensive information on management, public expenditure, and structure of Santiago's public and private urban forests. To examine this hypothesis, Santiago was divided into socioeconomic strata, then using air photo interpretation and stratified field sampling, urban forest structures were quantified by socioeconomic strata. In addition, interview surveys were used to determine municipal urban forest management and expenditures for different public urban forests based on socioeconomic strata. Urban forests in the high socioeconomic strata had fewer public trees, greater tree cover, tree and leaf area density, and leaf area index than lower socioeconomic strata. The percentage of total municipal budget allocated to public urban forest management was consistent among strata, but the total public urban forest budgets were greater in the high socioeconomic strata. Public urban forest structure is related to the socioeconomic strata of Santiago's different comunas. 相似文献
95.
Joseph Aubert Mouen Bedimo Daniel Bieysse Ibrahim Njiayouom Jean Pierre Deumeni Christian Cilas Jean Loup Nottéghem 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(4):391-400
In the high altitude regions of Africa, coffee berry disease (CBD), caused by Colletotrichum kahawae, is the main constraint for arabica coffee (Coffea arabica) production. However, certain agricultural practices can reduce losses caused by the disease and thereby promote optimum
production. On small family farms in Cameroon, mixed cropping with fruit trees, intercropping with food crops and maintenance
pruning of coffee trees are very widespread agricultural practices that can affect CBD epidemics. Consequently, an epidemiological
study was conducted to assess how cultural practices affected the disease in an arabica coffee smallholding in Cameroon. The
disease was monitored on a weekly basis over four successive years (2002–2005) on coffee trees in diverse cultural situations.
Cultural practices likely to reduce losses due to CBD were identified. The infection rate was significantly lower on coffee
trees grown intensively than on coffee trees grown in the traditional manner. Coffee trees located under the shade of fruit
trees were significantly less attacked than those located in full sunlight. In addition, berries on the leafless parts of
branches, near the main trunk of the coffee tree, were less infected than those on leafy sections. These results show that
maintenance pruning, removal of mummified berries, and mixed cropping with shade plants are cultural practices which create
environmental conditions that limit CBD development. 相似文献
96.
Gregory B. Daniel DVM MS Kyle K. Kerstetter DVM Jill E. Sackman DVM PhD Janice M. Bright MS DVM Dorothy Schmidt BS 《Veterinary radiology & ultrasound》1998,39(5):459-469
Radionuclide ventriculography has been used in humans to evaluate valvular incompetency. The stroke volume ratio, derived from the radionuclide ventriculogram, is used to quantify the severity of mitral regurgitation (MR). Previous studies conducted in humans have shown that left to right stroke volume ratio increases as the severity of MR increases. In this study, we evaluated radionuclide ventriculography as a noninvasive method to detect MR in dogs with surgically created mitral insufficiency. Six male and three female adult, conditioned mongrel dogs were used. Scintigraphic studies were performed prior to and 4 weeks after surgically created MR. Because of the overlap of the left and right ventricles when viewed from a left lateral position, we combined data from a first-pass radionuclide angiocardiogram with the radionuclide ventriculogram to obtain a corrected stroke volume ratio. Blood flow transit parameters were also derived from the first-pass radionuclide angiocardiogram. Standard left ventricular functional indices were also measured from the radionuclide ventriculogram. On the left lateral view of the heart, 25 to 30% of the right ventricular volume overlaps the left ventricle. After correcting for the overlap, the stroke volume ratio of normal dogs was 1.17±0.178 (mean±SD), which increased to 2.06±0.41 (mean±SD) (p<.001) 4 weeks after creation of MR. The was no significant change in left ventricular ejection fraction or peak rate of ejection following MR. The transit times of blood through the left ventricle were measured from the first-pass radionuclide angiocardiogram and were expressed as half-time clearance, peak clearance rate, and time to peak clearance rate. The baseline half-time clearance was 2.07±0.71 s (mean±SD), which increased to 6.70±4.89 s (mean±SD) (p=.02) after creation of MR. The baseline peak clearance rate was 49.75±8.96 cts/s (mean±SD), which decreased to 23.12±6.84 cts/s (mean±SD) (p<.001) after creation of MR. Stroke volume ratios significantly increased following creation of MR. Blood flow transit through the left ventricle slowed following creation of MR. The variability of these parameters were small in the baseline studies, suggesting these techniques may be clinically useful to gauge the severity of MR in dogs. 相似文献
97.
98.
Robert A. Spotts Kelly M. Wallis Maryna Serdani Daniel T. O’Gorman Peter L. Sholberg 《Postharvest Biology and Technology》2009,51(2):227-231
The objectives of this study were to develop primers and a real time PCR protocol for the postharvest biocontrol yeast Cystofilobasidium infirmominiatum (Cim). The application of this technology was developed to quantify Cim on the surfaces of apple, two pear cultivars, and sweet cherry fruit treated over a range of concentrations. Statistically significant relationships were observed between Cim DNA on fruit surfaces, expressed as μg/m2, and CFU/L of dip suspensions for apple, pear, and sweet cherry. In addition, the relationship for each fruit was significantly different from the other three fruits. Threshold values of concentrations of Cim DNA on the fruit surface were calculated based on regression equations and a dose of 2.0 × 1011 CFU/L of dip suspension, the dose for optimum decay control, and were 4.8, 7.0, 16.5, and 25.2 μg/m2 for Bosc pear, Lapins sweet cherry, d’Anjou pear, and Golden Delicious apple, respectively. Monitoring Cim DNA concentration on fruit surfaces will assure that Cim is being properly applied to fruit and that a sufficient number of cells are present for optimum decay control. 相似文献
99.
Blood samples were taken at weekly intervals from 54 dairy cows (mainly Friesians and Jerseys) during the periods 8 weeks before and 8 weeks after calving. The cows were divided into two age groups; group 1 consisting of 26 cows aged 2 1/2 years and group 2 consisting of 28 cows aged 5–9 years. The changes in the erythrocyte sodium (ENa) and the erythrocyte potassium (EK) concentrations before and after calving were expressed as the slopes for each component regressed on weeks. In the older cows the concentration of ENa decreased (p<0.05) while that of EK increased (p<0.05) after calving. Both the ENa and EK concentrations varied significantly (p<0.01) between cows in the two age groups. The prepartum and postpartum ENa and the postpartum EK concentrations varied significantly (p<0.05) between weeks. EK type did not influence the changes in ENa or EK concentrations before or after calving. 相似文献
100.
M H Gatei M F Lavin R C Daniel 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1990,37(8):575-580
In order to elucidate whether natural infection of BLV in cattle might induce humoral immunological responses, changes in IgG1, IgG2, and IgM concentrations in the sera of infected cattle were determined. Twelve BLV-infected cattle were used. Cattle of different breeds were classified serologically and haematologically into BLV + PL+, BLV + PL- and BLV-free groups. Ig concentrations in the sera of the three groups were quantitated using a commercial single radial immunodiffusion assay. The findings were compared to those of BLV-free cattle. The serum IgM concentrations were significantly lower in cattle with PL (P less than 0.001) than in BVL + PL- and BLV-free cattle. The IgM concentrations tended to be lower in BLV+ PL- than those of BVL-free cattle. There were no significant differences in IgG1 and IgG2 serum concentrations between the three experimental cattle groups. IgG1 was the predominant subtype in the sera of all cattle groups. 相似文献