全文获取类型
收费全文 | 974篇 |
免费 | 54篇 |
专业分类
林业 | 80篇 |
农学 | 31篇 |
基础科学 | 10篇 |
186篇 | |
综合类 | 124篇 |
农作物 | 33篇 |
水产渔业 | 96篇 |
畜牧兽医 | 369篇 |
园艺 | 18篇 |
植物保护 | 81篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 17篇 |
2016年 | 33篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 49篇 |
2012年 | 48篇 |
2011年 | 69篇 |
2010年 | 43篇 |
2009年 | 35篇 |
2008年 | 58篇 |
2007年 | 55篇 |
2006年 | 61篇 |
2005年 | 65篇 |
2004年 | 48篇 |
2003年 | 60篇 |
2002年 | 49篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1967年 | 3篇 |
1959年 | 6篇 |
1957年 | 2篇 |
1949年 | 3篇 |
1945年 | 2篇 |
排序方式: 共有1028条查询结果,搜索用时 15 毫秒
41.
42.
Martín-Cabrejas MA Ariza N Esteban R Mollá E Waldron K López-Andréu FJ 《Journal of agricultural and food chemistry》2003,51(5):1254-1259
The effect of different conditions of pea germination on dietary fiber (DF) composition was studied. Insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) were subjected to acid hydrolysis, and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Germinated peas exhibited significantly higher contents of total dietary fiber (TDF) than the raw sample, due to the increases of both DF fractions. Under darkness conditions, germination exhibited the highest contents of IDF and SDF. Decreasing IDF/SDF ratios showed that the carbohydrate changes did not take place to the same extent during germination, the SDF fraction being the most affected. The detailed chemical composition of fiber fractions reveals increases of cellulose in the IDF of germinated samples, whereas SDF exhibits a decrease of pectic polysaccharides and also increases of polysaccharides rich in glucose and mannose. The DF results were corroborated by a comparative examination of the cell wall carbohydrate composition. 相似文献
43.
Pierre Feutry Philippe Keith Christophe Pécheyran Fanny Claverie Tony Robinet 《Ecology of Freshwater Fish》2011,20(4):636-645
Abstract – Strontium/Calcium (Sr/Ca) and Barium/Calcium (Ba/Ca) ratios were measured in 60 otoliths of the French Polynesian flagtail Kuhlia malo. Both elemental ratios were needed to correctly distinguish residence in marine, brackish and fresh water. High Sr/Ca and low Ba/Ca around the nucleus of all otoliths provided evidence of marine residency during the early life of all individuals. At about 0.5 mm from the core, Ba/Ca increased rapidly and remained high in all otoliths. High and unstable Sr/Ca ratios were attributed to estuarine residency, whereas low and stable Sr/Ca ratios were attributed to freshwater residency. These chemical signatures inferred that following recruitment to rivers, some fish remained in the estuary, while others moved upstream. Some individuals shared their time between fresh and brackish waters later in life. The findings of this study have important implications for the protection of nearshore, brackish and freshwater environments for the conservation of this French Polynesian diadromous species. 相似文献
44.
Williamson NL Frank LA Hnilica KA 《Journal of the American Veterinary Medical Association》2002,221(6):802-806
OBJECTIVE: To determine how rapidly trimethoprim-sulfamethoxazole affects serum total thyroxine (T4) and thyroid-stimulating hormone (TSH) concentrations in euthyroid dogs and how quickly hormone concentrations return to reference values following discontinuation of administration. DESIGN: Prospective study. ANIMALS: 7 healthy euthyroid dogs. PROCEDURE: Dogs were given trimethoprim-sulfamethoxazole (26.5 to 31.3 mg/kg [12 to 14.2 mg/lb], PO, q 12 h) for a maximum of 6 weeks. A CBC and Schirmer tear test were performed and serum total T4 and TSH concentrations were measured weekly. Administration of trimethoprim-sulfamethoxazole was discontinued if total T4 concentration was less than the lower reference limit and TSH concentration was greater than the upper reference limit or if persistent neutropenia developed. RESULTS: Six dogs had total T4 concentrations less than the lower reference limit within 3 weeks; T4 concentration was decreased after 1 week in 3 of these 6 dogs. In these 6 dogs, TSH concentration was greater than the upper reference limit within 4 weeks. In 1 dog, T4 and TSH concentrations were not affected, despite administration of trimethoprim-sulfamethoxazole for 6 weeks. Neutropenia developed in 4 dogs. In 1 dog, the neutropenia resolved while trimethoprim-sulfamethoxazole was still being administered. In the other 3, neutrophil counts returned to reference values 1 week after drug administration was discontinued. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of trimethoprim-sulfamethoxazole at a dosage of 26.5 to 31.3 mg/kg, PO, every 12 hours can substantially alter serum total T4 and TSH concentrations and neutrophil counts in dogs within as short a time as a few weeks. 相似文献
45.
46.
An optimized system of computerized image analysis was used to investigate variations in the adherence of Staphylococcus intermedius to canine corneocytes from four different breed groups and six different anatomical sites. S. intermedius showed significantly greater adherence to the head and neck compared with the dorsum, but adherence to the limb, axilla and groin did not differ from other sites. Furthermore, there was significantly greater adherence of S. intermedius to corneocytes from the dorsum, forelimb, axilla and groin of Boxers and Bull Terriers than Spaniels and Hounds. S. intermedius, and also Pseudomonas aeruginosa, exhibited abundant adherence, which was significantly greater than Staphylococcus aureus, Streptococcus canis, Klebsiella pneumoniae and Escherichia coli. In addition, S. intermedius adherence demonstrated a sigmoid dose-response curve with increasing bacterial concentration. These results suggest that S. intermedius adheres to canine corneocytes by a specific receptor-ligand interaction and adheres to the skin of some breeds more avidly than others. However, variations in adherence between body regions would not account for the predilection sites of canine bacterial pyoderma. 相似文献
47.
Precolostral calves and their dams were serologically investigated for the presence of antibodies against Bovine Herpesvirus 1 in diagnostic tests with a very high sensitivity and specificity. Although the syndesmo-chorial type of placenta of ruminants does not transfer gamma globulins, a large number of calves had antibodies, in most cases in a very low concentration. Significant correlations were found between the serological status of the dam, the status of the calf, and the titre of antibodies. Oral intake of maternal blood by the calf at birth or transmission or leakage of maternal antibodies during pregnancy might be possible causes of precolostrally positive calves. From the results it is concluded that to reduce the risk of obtaining BHV1-positive calves, BHV1-negative dams should be selected for breeding purposes. 相似文献
48.
J'mai M. Gayle Noah D. Cohen M. Keith Chaffin 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(3):140-146
In order to identify variables obtained at admission that could be used to predict survival in septicemic foals, medical records of 65 foals diagnosed with septicemia were reviewed. Initially, variables were analyzed independently (univariate analysis) for association with survival. Of the physical examination and historical data examined using univariate analysis, the ability to stand at admission, respiratory rate ≥ 60 breaths per minute (bpm), and normal-appearing mucous membranes were significantly associated with survival. Foals with history of induced parturition were significantly less likely to survive. The following hematologic and serum biochemical variables determined at admission were significantly associated with survival: white blood cell count a 6,000 cells/μL, neutrophil count <4,000 cells/μL, serum albumin concentration <2.2 g/dL, serum glucose concentration <120 mg/ dL, blood pH ≥ 7.35, and positive base excess. The administration of plasma at admission was significantly associated with survival. Stepwise multiple logistic regression analysis was performed to evaluate the association between survival and variables identified as significantly associated with survival in bivariate analysis. The final multivariate model selected included the variables standing, duration of clinical signs (24-hour intervals) prior to admission, respiratory rate a 60 bpm, neutropenia (> 4,000 cells/μL), and neonatal age category. The probability of survival was significantly increased for foals that were standing, had a respiratory rate a 60 bpm, and that had a neutrophil count <4,000 cells/μL at admission. Probability of survival was significantly decreased for foals that had a longer duration of clinical signs prior to admission. For each 24 hours of duration, the estimated risk of death was increased by 5.8-fold. 相似文献
49.
The concentrations of Pb, CO, CH4 and total hydrocarbons have been measured at a roadside site and at the exit of a multistorey car park. Average concentrations over short periods (10 to 25 min) have been calculated for each pollutant and possible correlations between these average levels of the different pollutants investigated. Significant correlations were found at only one site and the conclusion was drawn that it is only under exceptional conditions that correlations in levels exist over these extremely short averaging periods. 相似文献
50.
Antonio Paoli Tatiana Moro Gerardo Bosco Antonino Bianco Keith A. Grimaldi Enrico Camporesi Devanand Mangar 《Marine drugs》2015,13(2):996-1009
Background: the ketogenic diet (KD) has become a widely used nutritional approach for weight loss. Some of the KD’s positive effects on metabolism and cardiovascular risk factors are similar to those seen after n-3 polyunsaturated fatty acids (ω-3) supplementation. We hypothesized that a ketogenic Mediterranean diet with phytoextracts combined with ω-3 supplementation may have increased positive effects on cardiovascular risk factors and inflammation. Methods: We analyzed 34 male overweight subjects; aged between 25 and 65 years who were overall healthy apart from overweight. The subjects followed a ketogenic diet protocol for four weeks; with (KDO3) or without (KD) ω-3 supplementation. Results: All subjects experienced a significant loss of body weight and body fat and there was no significant differences between treatment (body weight: KD—4.7 kg, KDO3—4.03 kg, body fat KD—5.41 kg, KDO3—5.86 kg). There were also significant decreases in total cholesterol, LDL-c, and glucose levels. Triglycerides and insulin levels decreased more in KDO3 vs. KD subjects, with a significant difference. All the investigated inflammatory cytokines (IL-1β, IL-6, TNF-α) decreased significantly in KDO3 subjects whilst only TNF-α showed a significant decrease in KD subjects over the 12 month study period. No significant changes were observed in anti-inflammatory cytokines (IL-10 and IL-1Ra), creatinine, urea and uric acid. Adiponectin increased significantly only in the KDO3 group. Conclusions: ω-3 supplementation improved the positive effects of a ketogenic Mediterranean diet with phytoextracts on some cardiovascular/metabolic risk factors and inflammatory state. 相似文献