全文获取类型
收费全文 | 3510篇 |
免费 | 225篇 |
国内免费 | 7篇 |
专业分类
林业 | 157篇 |
农学 | 64篇 |
基础科学 | 17篇 |
387篇 | |
综合类 | 544篇 |
农作物 | 73篇 |
水产渔业 | 218篇 |
畜牧兽医 | 1931篇 |
园艺 | 72篇 |
植物保护 | 279篇 |
出版年
2023年 | 22篇 |
2022年 | 33篇 |
2021年 | 67篇 |
2020年 | 74篇 |
2019年 | 58篇 |
2018年 | 55篇 |
2017年 | 66篇 |
2016年 | 62篇 |
2015年 | 57篇 |
2014年 | 86篇 |
2013年 | 170篇 |
2012年 | 185篇 |
2011年 | 214篇 |
2010年 | 141篇 |
2009年 | 130篇 |
2008年 | 190篇 |
2007年 | 196篇 |
2006年 | 182篇 |
2005年 | 168篇 |
2004年 | 177篇 |
2003年 | 171篇 |
2002年 | 137篇 |
2001年 | 56篇 |
2000年 | 53篇 |
1999年 | 44篇 |
1998年 | 35篇 |
1997年 | 33篇 |
1996年 | 37篇 |
1995年 | 28篇 |
1994年 | 27篇 |
1993年 | 39篇 |
1992年 | 44篇 |
1991年 | 40篇 |
1990年 | 50篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 35篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 18篇 |
1983年 | 23篇 |
1981年 | 19篇 |
1980年 | 21篇 |
1979年 | 34篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1974年 | 18篇 |
1972年 | 16篇 |
1970年 | 16篇 |
1969年 | 16篇 |
排序方式: 共有3742条查询结果,搜索用时 15 毫秒
861.
Elizabeth L. Wagner Gary D. Potter ) Pete G. Gibbs Elena M. Eller Brett D. Scott Martha M. Vogelsang Rosemary L. Walzem 《Journal of Equine Veterinary Science》2010
Nine mature horses were used to evaluate superoxide dismutase (SOD) response to a low-intensity standard exercise test and the effect of copper (Cu) and zinc (Zn) supplement form on enzyme activity. The modified switchback experiment was conducted over seven 28-day periods. Horses were conditioned to perform an average daily workload of 3.93 kg∗km∗10−3 with a digestible energy (DE) demand of approximately 29 Mcal. Following a controlled Cu and Zn repletion-depletion diet sequence, horses were fed a diet intended to be marginally deficient in Cu and Zn with the minerals supplemented in either sulfate or organic chelate forms. Horses were then subjected to a standardized exercise test to enable evaluation of SOD activity during exercise and immediate recovery. In the final analyses, mineral contents of the experimental diets were significantly different (P < .05). The mean mineral concentration of the sulfate diet was 6.28 ppm Cu and 35.99 ppm Zn, while the chelate diet contained 23.62 ppm Cu and 90.67 ppm Zn. Even so, resting SOD activity was not altered by diet (1793.47 ± 323.00 U/g Hb for the sulfate diet, 1355.70 ± 148.32 U/g Hb for the organic-chelate diet), nor did SOD activity change in response to the low-intensity workout. The SOD activity was unchanged by feeding a Cu and Zn supplemented diet to horses fed to be in a mineral-deficient state. These exercise bouts did not appear to have a significant impact on SOD activity. Other types of oxidative stress should be considered when trying to evaluate the antioxidant responsiveness of this enzyme. 相似文献
862.
Melissa A. Moyer Katherine Scott Rachel E. Cianciolo 《The Canadian veterinary journal. La revue veterinaire canadienne》2016,57(5):501-506
This report describes a 3-year-old female Doberman pinscher dog with ligneous conjunctivitis and a protein-losing nephropathy not associated with underlying plasminogen deficiency. Glomerulonephropathy in this circumstance had a positive outcome. 相似文献
863.
864.
Timothy H. Dietz Cody B. Scott Erika J. Campbell Corey J. Owens Charles A. Taylor Richard Brantely 《Strength and Conditioning Journal》2010,63(3):366-372
Redberry (Juniperus pinchotii Sudw.) and ashe (Juniperus ashei Buchh.) juniper dominate rangelands throughout central Texas. Our objective was to attempt to improve the efficacy of goats as a biological control mechanism for juniper through behavioral training. Conditioning sheep and goats to increase the palatability of chemically defended plants can be a useful tool in brush control. Previous research illustrated that goats can be conditioned to consume more juniper while in individual pens when foraging choices are limited. To test whether this creates a longer-lasting increase in juniper preference, we determined if goats would continue to consume juniper on pasture for one year after being fed juniper in individual pens for 14 d. Female Boer-cross goats (n = 40) were randomly divided into two treatments: conditioned and naive to juniper. At approximately 12 mo of age, conditioned goats were placed in individual pens and fed redberry juniper 1 h daily for 14 d, while naive goats received only alfalfa pellets to meet maintenance requirements. After the pen-feeding phase of the study, goats were placed in one of four pastures (10 goats · pasture?1) for 12 mo. Two pastures housed conditioned goats, and two pastures housed naive goats at a moderate stocking rate (1 animal unit · yr?1 · 8 ha?1). Bite count surveys were conducted twice per month, while herbaceous standing crop and monoterpene levels were measured once per month. Juniper preference varied monthly; however, conditioned goats consistently ate more (P < 0.05) juniper than naive goats except for April, when the study began, and March, when the study ended. When selection of herbaceous forages decreased, conditioned goats increased selection of juniper, while naive goats increased selection of other palatable shrubs. Seasonal changes of monoterpene levels in juniper had no apparent effect on juniper preference. We contend that feeding juniper at weaning will increase use of the plant in grazing situations. 相似文献
865.
866.
D W Scott W H Miller Jr G A Reinhart H O Mohammed M S Bagladi 《Canadian journal of veterinary research》1997,61(2):145-153
A commercial, lamb and rice, dog food with an omega-6:omega-3 fatty acid ratio of 5.5:1 was fed in a single-blinded, self-controlled clinical trial to 18 atopic dogs. The pruritus in 8 of these dogs (44.4%) was satisfactorily controlled within 7 to 21 d, returned within 3 to 14 d after the diet was withdrawn, and was again controlled when the diet was reinstated. Plasma and skin levels of examined fatty acids changed in all 18 dogs when their diet was switched to the test diet. Dogs responding to the test diet had a different pattern of fatty acid change as compared to the dogs which failed to respond to the diet, suggesting that there are subsets of atopic dogs with different fatty acid metabolism capabilities. 相似文献
867.
Schatzberg SJ Haley NJ Barr SC de Lahunta A Sharp NJ 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2005,19(4):553-559
The objective of this investigation was to determine whether or not herpesvirus (herpes-), adenovirus (adeno-), or canine parvovirus DNA is present in the brains of dogs with necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalitis (GME). Paraffin-embedded brain specimens from 12 histopathologically confirmed dogs with NME, 3 with NLE, and 7 with GME were screened for viral DNA with degenerate herpes- and adenovirus polymerase chain reaction (PCR) and a canine parvovirus-specific PCR. Positive-control specimens included genomic viral DNA and paraffin-embedded tissues from dogs with confirmed herpes-, adeno-, or canine parvovirus infections. Herpes-, adeno-, or canine parvovirus DNA was amplified by PCR from the corresponding positive-control specimens. Negative controls included 7 dogs with various brain disorders and produced no viral amplicons. The 22 dogs with NME, NLE, and GME were negative for viral DNA. Additional studies testing for other viruses or inherited genetic mutations are warranted to gain insight into the etiologies of NME, NLE, and GME. We discuss potential etiologies and provide a clinical and histopathologic overview of these common canine encephalitides. 相似文献
868.
A review of case material from the Cornell University College of Veterinary Medicine from 1988 to 1996 identified 20 dogs and one cat with definitive or presumed erythema multiforme. An additional 24 dogs and five cats with definitive or presumed erythema multiforme were found in the veterinary literature. Erythema multiforme accounted for only 0.40% and 0.11%, respectively, of all the canine and feline dermatology cases examined over a 9-year period. German Shepherd dogs and Pembroke Welsh Corgis appeared predisposed. The condition was manifested as a vesiculobullous and/or ulcerative dermatosis in the majority of dogs and cats. In dogs, the most commonly affected body sites included the ventrum (especially axillae and groin), mucocutaneous junctions, oral cavity, pinnae, and footpads. Histopathological findings in cutaneous and mucocutaneous biopsy specimens were consistent with previously published criteria. In dogs, erythema multiforme occurred more frequently in patients receiving drug therapy. In cats, all cases of erythema multiforme were presumed to be drug related. Elimination of the associated trigger factor and supportive care usually resulted in resolution of the erythema multiforme within 1–2 weeks. Four dogs with severe idiopathic erythema multiforme were successfully managed with glucocorticoids or azathioprine. 相似文献
869.
Arroyo LG Rousseau JD Staempfli HR Weese JS 《The Canadian veterinary journal. La revue veterinaire canadienne》2005,46(12):1130-1131
Clostridium difficile-associated diarrhea was suspected in a 1-week-old elk (Cervus elaphus) calf. The isolation of a toxigenic strain of C. difficile from a diarrheic fecal sample, along with exclusion of other enteropathogens, formed the basis of this presumptive diagnosis. Further study is indicated to evaluate the role of C. difficile in neonatal diarrhea in elk. 相似文献
870.
Ian Young Lisa Waddell Javier Sanchez Barbara Wilhelm Scott A. McEwen Andrijana Rajić 《Preventive veterinary medicine》2014
Knowledge synthesis refers to the integration of findings from individual research studies on a given topic or question into the global knowledge base. The application of knowledge synthesis methods, particularly systematic reviews and meta-analysis, has increased considerably in the agri-food public health sector over the past decade and this trend is expected to continue. The objectives of our review were: (1) to describe the most promising knowledge synthesis methods and their applicability in agri-food public health, and (2) to summarize the recent advancements, challenges, and opportunities in the use of systematic review and meta-analysis methods in this sector. We performed a structured review of knowledge synthesis literature from various disciplines to address the first objective, and used comprehensive insights and experiences in applying these methods in the agri-food public health sector to inform the second objective. We describe five knowledge synthesis methods that can be used to address various agri-food public health questions or topics under different conditions and contexts. Scoping reviews describe the main characteristics and knowledge gaps in a broad research field and can be used to evaluate opportunities for prioritizing focused questions for related systematic reviews. Structured rapid reviews are streamlined systematic reviews conducted within a short timeframe to inform urgent decision-making. Mixed-method and qualitative reviews synthesize diverse sources of contextual knowledge (e.g. socio-cognitive, economic, and feasibility considerations). Systematic reviews are a structured and transparent method used to summarize and synthesize literature on a clearly-defined question, and meta-analysis is the statistical combination of data from multiple individual studies. We briefly describe and discuss key advancements in the use of systematic reviews and meta-analysis, including: risk-of-bias assessments; an overall quality-of-evidence approach; engagement of stakeholders; Bayesian, multivariate, and network meta-analysis; and synthesis of diagnostic test accuracy studies. We also highlight several challenges and opportunities in the conduct of systematic reviews (e.g. inclusion of grey literature, minimizing language bias, and optimizing search strategies) and meta-analysis (e.g. inclusion of observational studies and approaches to address the insufficient reporting of data and significant heterogeneity). Many of these developments have yet to be comprehensively applied and evaluated in an agri-food public health context, and more research is needed in this area. There is a need to strengthen knowledge synthesis capacity and infrastructure at the regional, national, and international levels in this sector to ensure that the best available knowledge is used to inform future decision-making about agri-food public health issues. 相似文献