全文获取类型
收费全文 | 1815篇 |
免费 | 88篇 |
国内免费 | 2篇 |
专业分类
林业 | 124篇 |
农学 | 27篇 |
基础科学 | 4篇 |
273篇 | |
综合类 | 219篇 |
农作物 | 81篇 |
水产渔业 | 93篇 |
畜牧兽医 | 930篇 |
园艺 | 34篇 |
植物保护 | 120篇 |
出版年
2023年 | 17篇 |
2022年 | 9篇 |
2021年 | 26篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 40篇 |
2017年 | 41篇 |
2016年 | 44篇 |
2015年 | 43篇 |
2014年 | 43篇 |
2013年 | 84篇 |
2012年 | 103篇 |
2011年 | 149篇 |
2010年 | 43篇 |
2009年 | 74篇 |
2008年 | 113篇 |
2007年 | 115篇 |
2006年 | 99篇 |
2005年 | 104篇 |
2004年 | 89篇 |
2003年 | 90篇 |
2002年 | 75篇 |
2001年 | 25篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 16篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 18篇 |
1974年 | 5篇 |
1970年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有1905条查询结果,搜索用时 10 毫秒
41.
Two feeding studies were conducted to examine the impact of dietary inclusion of specific feed ingredients on manure characteristics and manure odor. In one study, 72 finishing pigs were used to evaluate the effects of distillers dried grains with solubles (DDGS) on pig performance, manure characteristics, and odorous emissions. Three diets containing 0, 5, and 10% DDGS were fed during six 4-wk feeding periods. Week 1 served as a dietary adjustment period. Animals were housed in two feeding rooms (six pigs/room) with one treatment/room. A new group of animals (average initial BW = 85.8 kg) was used for each feeding period. Diets were replicated four times. Rooms were equipped with individual shallow manure storage pits that were cleaned once weekly (d 7). On d 4 and 7 of each week, manure pit samples, for chemical analyses, and air samples, for olfactometry analysis, were collected from each room. Odor dilution threshold was greater on d 7 than on d 4 of manure storage across all treatments (P < 0.01). No treatment differences in manure composition were noted. In the second study, weaned pigs (approximately 5 wk old) were fed isonitrogenous diets containing 0, 1.5, or 3% bloodmeal. Pigs were housed by diet (three pigs/diet) in one of four individual feeding rooms. A new group of pigs was used for each of the two, 4-wk feeding periods. During period 1, the 3% bloodmeal diet was fed in two of the four rooms; the 0% bloodmeal diet was fed in two rooms during period 2. Manure samples, for chemical analyses, and air samples, for olfactometry analysis, were collected 2 d per week (d 4 and d 6) from each room during wk 2 through 4. No significant treatment differences were observed for odor dilution threshold (P = 0.30). Longer manure storage time, 6 d vs 4 d, resulted in a larger odor dilution ratio (P < 0.01). Manure composition was unaltered by storage time. Results suggest that odor intensifies during storage. 相似文献
42.
Gillespie BE Moorehead H Lunn P Dowlen HH Johnson DL Lamar KC Lewis MJ Ivey SJ Hallberg JW Chester ST Oliver SP 《Veterinary therapeutics : research in applied veterinary medicine》2002,3(4):373-380
Fifty-one chronically infected lactating dairy cows were used to evaluate the efficacy of extended pirlimycin therapy regimens for treatment of intramammary infections by environmental Streptococcus spp and Staphylococcus aureus. Cows (n = 47) with one or more infected mammary quarters were blocked by parity and randomly allocated to one of three groups for treatment with pirlimycin (50 mg/mammary quarter) as follows: one treatment per day for 2 days (n = 36 infected mammary quarters); one treatment per day for 5 days (n = 36 infected mammary quarters); and one treatment per day for 8 days (n = 20 infected mammary quarters). Four cows with nine infected mammary quarters were included as untreated controls. Milk samples from each mammary quarter were collected 7 days before treatment, immediately before treatment, and weekly for 4 weeks after the final treatment for microbiological evaluation. A bacteriologic cure was defined as a treated, infected quarter that was bacteriologically negative for the presence of previously identified bacteria at weekly intervals after treatment. Efficacy of pirlimycin therapy against intramammary infections caused by environmental Streptococcus spp and S. aureus was 44.4%, 61.1%, and 95.0% for the 2-, 5-, and 8-day treatment regimens, respectively. None of the infections in the untreated control quarters was cured. Significant differences in efficacy were detected between all pirlimycin groups and the untreated control group, between the 8- and 2-day treatment regimens, and between the 8-day and 5-day treatment regimens (P < or = .05). Results of this study indicate that extended pirlimycin therapy was effective in eliminating intramammary infections caused by environmental streptococci and S. aureus in lactating dairy cows. 相似文献
43.
ABSTRACT Ontogeny of the invasion process by Colletotrichum acutatum and C. fragariae was studied on petioles and stolons of the strawberry cultivar Chandler using light and electron microscopy. The invasion of host tissue by each fungal species was similar; however, each invasion event occurred more rapidly with C. fragariae than with C. acutatum. Following cuticular penetration via an appressorium, subsequent steps of invasion involved hyphal growth within the cuticle and within the cell walls of epidermal, subepidermal, and subtending cells. Both species of fungi began invasion with a brief biotrophic phase before entering an extended necrotrophic phase. Acervuli formed once the cortical tissue had been moderately disrupted and began with the development of a stroma just beneath the outer periclinal epidermal walls. Acervuli erupted through the cuticle and released conidia. Invasion of the vascular tissue typically occurred after acervulus maturation and remained minimal. Chitin distribution in walls of C. fragariae was visualized with gold-labeled wheat germ agglutinin. The outer layer of bilayered walls of conidia, germ tubes, and appressoria contained less chitin than unilayered hyphae in planta. 相似文献
44.
Jankowski MK Ogilvie GK Lana SE Fettman MJ Hansen RA Powers BE Mitchener KM Lovett SD Richardson KL Parsley L Walton JA 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2002,16(1):105-108
Matrix metalloproteinases (MMPs) are enzymes that play key roles in angiogenesis, tumor invasion, and metastasis in a wide variety of species. The purpose of this study was to evaluate pro and active MMP 2 and 9 concentrations in tumor, normal stromal tissue, and serum from tumor-bearing cats. We hypothesized that serum concentrations of pro and active forms of MMPs 2 and 9 would be predictive of MMP concentrations in tumor tissue and that these MMP concentrations would correlate with the histopathologic grade of the malignancies. Pro and active forms of MMPs 2 and 9 were determined by gelatin zymography and subsequent computerized densitometry from tumor and nearby stromal tissue and serum from 49 cats with various malignancies. The serum concentrations of MMPs from these tumor-bearing cats were compared with serum concentrations of MMPs from 44 normal cats of similar age and gender. Measurable concentrations of MMPs 2 and 9 were found within tumor, stromal, and serum samples. Mean concentrations of total pro and active MMPs 2 and 9 within tumor tissue were significantly higher (P values <.0001, .0031, <.001, and .0064, respectively) when compared with stromal tissue from the same animals. Serum MMP concentrations from tumor-bearing cats were higher than those from normal cats. Poor correlation was found between serum MMP concentrations and tissue MMP concentrations of increasing histologic grades of malignancies. 相似文献
45.
Dernell WS Van Vechten BJ Straw RC LaRue SM Powers BE Withrow SJ 《Journal of the American Animal Hospital Association》2000,36(3):245-251
Twenty dogs with histopathologically confirmed primary (n=15) or metastatic (n=5) osteosarcoma (n=14) or fibrosarcoma (n=6) of the vertebral column were treated with surgery (n=4), radiation therapy and chemotherapy (n=6), surgery and chemotherapy (n=2), or surgery, radiation, and chemotherapy (n=8). All dogs died due to their disease; 15 died due to local failure, and five died due to nonvertebral metastasis. Overall median survival time was 135 days, with a range of 15 to 600 days. Of the factors evaluated, only postoperative neurological status had a significant influence on outcome by multivariate analysis. This study supports the overall guarded prognosis for dogs with vertebral neoplasia. Better combinations of surgery, chemotherapy, and radiation therapy remain to be defined for this difficult subset of animal cancer. 相似文献
46.
Bruce K Wobeser Beverly A Kidney Barbara E Powers Stephen J Withrow Monique N Mayer Maria T Spinato Andrew L Allen 《Journal of veterinary diagnostic investigation》2007,19(4):439-443
Agreement among pathologists interpreting histologic specimens is an area of interest within human pathology, but little work in this area has been reported in the veterinary literature. Agreement among pathologists evaluating routine histologic sections of amputated digits from cats and dogs submitted to multiple diagnostic centers was examined. Histologic sections from surgical specimens were reviewed in a blinded fashion by two pathologists, and a comparison to the original diagnosis, as stated in the diagnostic report, was recorded. A total of 513 cases were reviewed, and complete agreement was reached in 409 (79.7%). Of the 104 instances of disagreement, 77 (74.0%) were considered to be of clinical significance. The diagnosis of keratoacanthoma was disagreed with in 19 of 21 diagnoses (90.4%). No other individual diagnosis was similarly disputed. The overall level of disagreement is large and is similar to that reported in human pathology and suggests that further study of this issue would be useful in veterinary pathology. 相似文献
47.
48.
Susan J. Sprague Marie-Hélène Balesdent Hortense Brun Helen L. Hayden Stephen J. Marcroft Xavier Pinochet Thierry Rouxel Barbara J. Howlett 《European journal of plant pathology / European Foundation for Plant Pathology》2006,114(1):33-40
Resistance of Brassica napus (oilseed rape, canola) conferred by three different major resistance genes has been overcome by changes in virulence of Leptosphaeria maculans populations in France and Australia. In South Australia where B. napus cultivars with major gene resistance derived from Brassica rapa ssp. sylvestris were grown extensively, resistance was rendered ineffective within 3 years of commercial release of the cultivar. Disease
severity was higher on cultivars with sylvestris-derived resistance than cultivars with polygenic resistance. This Australian situation is compared to that in France, where
resistance conferred by the Rlm1 gene was overcome nation-wide in 5 years under commercial cropping practices, and also where a source of resistance introgressed
into B. napus from B. juncea was rendered inefficient in 3 years in experimental field plots near Rennes. 相似文献
49.
Barbara I. Zemann Antony S. Moore William M. Rand Gail Mason David M. Ruslander Angela E. Frimberger Carrie A. Wood Deborah A. L'Heureux John Gliatto Susan M. Cotter 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(6):465-470
Ninety-eight dogs with lymphoma treated with a 5-drug combination chemotherapy regimen (vincristine, L-asparaginase. cyclophosphamide, doxorubicin, prednisone [VELCAP-L]) were evaluated for pretreatment characteristics predictive for response and remission duration. The complete remission rate was 69%, with a median remission duration of 55 weeks. Dogs with advanced stage of disease, constitutional signs, dogs that were older, and dogs that were dyspneic were less likely to achieve remission. Once in remission, small dogs and dogs without pretreatment thrombocytopenia were likely to have longer remission duration. Toxicoses were frequent, but rarely fatal, and no predictitive factors were found for a dog developing toxicoses. VELCAP-L is an effective treatment for dogs in stage I-III lymphoma, particularly in young, small animals. 相似文献
50.