全文获取类型
收费全文 | 2697篇 |
免费 | 191篇 |
国内免费 | 6篇 |
专业分类
林业 | 183篇 |
农学 | 50篇 |
基础科学 | 28篇 |
423篇 | |
综合类 | 483篇 |
农作物 | 72篇 |
水产渔业 | 297篇 |
畜牧兽医 | 1074篇 |
园艺 | 92篇 |
植物保护 | 192篇 |
出版年
2023年 | 23篇 |
2022年 | 29篇 |
2021年 | 66篇 |
2020年 | 80篇 |
2019年 | 94篇 |
2018年 | 99篇 |
2017年 | 111篇 |
2016年 | 90篇 |
2015年 | 66篇 |
2014年 | 85篇 |
2013年 | 121篇 |
2012年 | 177篇 |
2011年 | 229篇 |
2010年 | 138篇 |
2009年 | 84篇 |
2008年 | 170篇 |
2007年 | 185篇 |
2006年 | 141篇 |
2005年 | 156篇 |
2004年 | 154篇 |
2003年 | 149篇 |
2002年 | 111篇 |
2001年 | 33篇 |
2000年 | 29篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1967年 | 5篇 |
1966年 | 4篇 |
1965年 | 3篇 |
1952年 | 3篇 |
排序方式: 共有2894条查询结果,搜索用时 0 毫秒
31.
Adin CA Farese JP Cross AR Provitola MK Davidson JS Jankunas H 《American journal of veterinary research》2004,65(3):283-288
OBJECTIVE: To describe a percutaneously controlled static hydraulic urethral sphincter (SHUS) and evaluate urodynamic effects of the SHUS in canine cadavers. SAMPLE POPULATION: Cadavers of 6 adult female dogs. PROCEDURE: Cadavers were obtained immediately after dogs were euthanatized. Baseline maximal urethral closure pressure (MUCP) and cystourethral leak point pressure (CLPP) were measured by use of a urethral pressure profilometer. An SHUS system was constructed by use of a silicone vascular occluder and subcutaneous infusion port. The SHUS system was then placed around the pelvic urethra in each cadaver. Measurements of MUCP and CLPP were repeated after varying occlusion of the SHUS (0%, 25%, and 50% occlusion). Baseline MUCP and CLPP values were compared with values obtained at 0%, 25%, and 50% occlusion of the SHUS by use of repeated-measures ANOVA. RESULTS: Mean +/- SD MUCP for canine cadavers was 7 +/- 1.3 cm H2O at baseline, which increased to 127 +/- 53 cm H2O after 50% occlusion of the SHUS. Mean CLPP was 11 +/- 8.6 cm H2O at baseline, which increased to 73 +/- 38 cm H2O after 50% occlusion of the SHUS. Mean MUCP and CLPP were significantly associated with the amount of occlusion. CONCLUSIONS AND CLINICAL RELEVANCE: The SHUS had positive effects on MUCP and CLPP in canine cadavers. Therefore, additional evaluation of the SHUS in live dogs is warranted. 相似文献
32.
Jonathan L. Stowater DVM MS Christopher R. Lamb MA VETMB 《Veterinary radiology & ultrasound》1989,30(5):232-239
The ultrasonographic features of paraprostatic cysts in nine dogs are described along with historical, clinical, surgical and pathologic findings. Cysts occurred predominantly in older, large breed dogs (mean age 8 years, range 3–11 years). The most common presenting complaints were depression, inappetance, stranguria, tenesmus and bloody penile discharge. A palpable abdominal mass was the most common physical finding. Ultrasonographically, paraprostatic cysts were usually large anechoic structures; many contained internal septa. Moderately large anechoic cavities or cysts were also detected in the prostatic parenchyma of five dogs, and in two of these communication with the paraprostatic cyst was visualized. There were no clearly distinct ultrasonographic criteria to discriminate septic from nonseptic paraprostatic cysts. 相似文献
33.
Jacob F Polzin DJ Osborne CA Neaton JD Kirk CA Allen TA Swanson LL 《Journal of the American Veterinary Medical Association》2005,226(3):393-400
OBJECTIVE: To determine whether urine protein-to-creatinine ratio (UP:C) > or = 1.0 at initial diagnosis of chronic renal failure (CRF) is associated with greater risk of development of uremic crises, death, and progression of renal failure in dogs. DESIGN: Prospective cohort study. ANIMALS: 45 dogs with CRF PROCEDURE: Dogs were prospectively assigned to 2 groups on the basis of initial UP:C < 1.0 or 2 > or = 1.0. The association between magnitude of proteinuria and development of uremic crises and death was determined before and after dogs with initial UP:C > or =1.0 were assigned to 3 subgroups and compared with dogs with initial UP:C < 1.0. Changes in reciprocal serum creatinine concentration were used to estimate decrease in renal function. RESULTS: Initially, dogs had similar clinical characteristics with the exception of systolic blood pressure and UP:C. Relative risks of development of uremic crises and death were approximately 3 times higher in dogs with UP:C > or =1.0, compared with dogs with UP:C < 1.0. Relative risk of adverse outcome was approximately 1.5 times higher for every 1-unit increment in UP:C. The decrease in renal function was of greater magnitude in dogs with UP:C > or =1.0, compared with dogs with UP:C < 1.0. CONCLUSIONS AND CLINICAL RELEVANCE: Initial UP:C > or =1.0 in dogs with CRF was associated with greater risk of development of uremic crises and death, compared with dogs with UP:C < 1.0. Initial determinations of UP:C in dogs with naturally occurring CRF may be of value in refining prognoses. 相似文献
34.
M M Christopher V Perman J W Eaton 《Journal of the American Veterinary Medical Association》1989,194(8):1045-1056
Propylene glycol (PG) is a common preservative and source of synthetic carbohydrates in soft-moist pet foods. Propylene glycol was fed to cats for 5 weeks at concentrations found in commercial diets (1.6 g/kg of body weight; 12% of diet on a dry-weight basis) and for 3 weeks at concentrations exceeding usual intake (8 g/kg; 41% of diet). There was a dose-dependent increase in Heinz body percentage to 28% in cats fed the low dose of PG and to 92% in cats fed the high dose. Erythrocyte half-life, measured using [14C]-cyanate hemoglobin (Hb), decreased significantly (P less than 0.05) by 18.8% and 60% in cats fed the low and high PG doses, respectively. The PCV in cats fed the low dose was unaffected, whereas cats fed the high dose had a mean (+/- SEM) decrease in PCV from 33.5 +/- 1.05% to 26.3 +/- 1.45%, accompanied by punctate reticulocytosis and bone marrow erythroid hyperplasia. A dose-dependent increase in iron pigment was found in the liver and spleen of all cats. In cats fed the low dose of PG, erythrocyte reduced glutathione concentration actually increased from 7.02 +/- 0.56 to 9.74 +/- 0.69 mumol/g of Hb, but decreased to 2.96 +/- 0.27 mumol/g of Hb in cats fed the high dose. There was no significant increase in methemoglobin concentration. These results indicated that PG cannot be considered innocuous even at concentrations consumed by cats eating commercial diets. Heinz body-induced acceleration of RBC destruction develops in a dose-dependent manner, so that cats with greater food intake, ie, lactating queens and nursing kittens, are at greater risk for development of PG-induced Heinz body hemolytic anemia. 相似文献
35.
36.
37.
Hanley CS MacWilliams P Giles S Paré J 《The Canadian veterinary journal. La revue veterinaire canadienne》2006,47(10):1015-1017
A domestic ferret was presented for episodic regurgitation. Cytologic examination and culture of an enlarged submandibular lymph node revealed Cryptococcus neoformans variety grubii (serotype A). The ferret was successfully treated with itraconazole. This is the first documented case of Cryptococcus neoformans variety grubii in a ferret in the United States. 相似文献
38.
A review of CpGs and their relevance to aquaculture 总被引:8,自引:0,他引:8
CpG oligodeoxynucleotides (ODN) have been described as functioning as natural adjuvants because they promote professional antigen presenting cell (APC) function and co-stimulate lymphocytes. The majority of studies into the immune effects of CpG ODN to date have been carried out on mammals where they are proving very successful at stimulating innate and adaptive immune responses in a variety of species as well as protecting them from bacterial, viral and protozoan pathogens. Fish also possess the ability to raise both innate and adaptive immune responses to invading pathogens and interest in the effect of CpG ODN on the piscine immune system is growing. Various studies have now been carried out to elicit the effects of CpG ODN on diverse fish species showing that 31 different B-class CpG ODN exert various immune responses both in vivo and in vitro in salmonids, cyprinids and pleuronectiformes. These responses include activation of macrophages, proliferation of leucocytes and stimulation of cytokine expression. CpG ODN have also been shown to be protective against bacterial and viral challenge as well as against pathogenic amoebae. As would be expected these effects are all dependent on not only the ODN sequence and length but on the concentration and the species in which it is being used. This review provides the first comprehensive overview of all CpG ODN tested in fish to date and brings together all the work carried out in this field. 相似文献
39.
We present a case of reactive histiocytic disease involving the orbit, optic nerve, retina, and choroid in a Border Collie dog initially presenting for vision loss. Long-term partial return of vision has been achieved with systemic immunosuppression. Anterior segment and ocular surface manifestations of reactive histiocytic disease in dogs are relatively common. Posterior segment and orbital involvement, however, are minimally documented in the existing literature. To the authors' knowledge, this is the first report of disease confined to the orbit and posterior segment as well as the first report of vision loss as a presenting complaint for reactive histiocytic disease. Clinical, magnetic resonance imaging, cytologic, and histopathologic findings are reviewed. 相似文献
40.