全文获取类型
收费全文 | 1065篇 |
免费 | 62篇 |
专业分类
林业 | 64篇 |
农学 | 17篇 |
基础科学 | 6篇 |
120篇 | |
综合类 | 151篇 |
农作物 | 32篇 |
水产渔业 | 72篇 |
畜牧兽医 | 581篇 |
园艺 | 27篇 |
植物保护 | 57篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 35篇 |
2020年 | 31篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 27篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 34篇 |
2013年 | 43篇 |
2012年 | 56篇 |
2011年 | 80篇 |
2010年 | 43篇 |
2009年 | 22篇 |
2008年 | 57篇 |
2007年 | 47篇 |
2006年 | 59篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 16篇 |
2000年 | 16篇 |
1999年 | 14篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 14篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1968年 | 4篇 |
1948年 | 9篇 |
排序方式: 共有1127条查询结果,搜索用时 31 毫秒
1.
Kevin R. Stuart Arnold G. Eversole David E. Brune 《Journal of the World Aquaculture Society》2001,32(1):105-111
Abstract.— The freshwater mussel Elliptio complanata was provided water containing green algae and cyanobacteria delivered from the Partitioned Aquaculture System (PAS) at eight flow rates to determine algal filtration rates as mg of particulate organic carbon (POC)/kg wet tissue weight per h. The dominant taxon in cyanobacterial waters was Microcystis while the dominant taxa in green algal waters were Scenedesmus and Ankistrodesmus . The cell counts of Scenedesmus and Ankistrodesmus were the only algal taxa that were significantly different between the incoming water and water filtered by mussels. Filtration rates of POC obtained from green algal water were significantly greater than from cyanobacteria-dominated waters at all flow rates. A significant increase in mean filtration rate was observed as flow rates increased. The filtration rate of green algae increased as POC concentration increased, peaking at 28 mg C/L. A maximum filtration rate was not observed with cyanobacterial waters. 相似文献
2.
Polycythaemia vera was diagnosed in a three-year-old domestic shorthaired cat referred because of seizures and a high packed cell volume (PCV). Laboratory examination revealed severe erythrocytosis (PCV 79 per cent). Diagnosis was reached by excluding causes for relative and secondary absolute polycythaemia. As phlebotomy proved impossible for initial treatment due to hyperviscosity, four leeches were used to suck blood and the PCV was consequently reduced to 64 per cent. A further 24 hours later, when bleeding at the sites of sucking had stopped, the PCV was 56 per cent. Long-term management of the condition was achieved with hydroxyurea (100 mg/cat once daily) and intermittent phlebotomy. Initial treatment using leeches in cases of polycythaemia vera is a simple, non-invasive, well tolerated and effective method where phlebotomy is not possible. 相似文献
3.
4.
Stephanie A Smith Anthony H Tobias 《Veterinary Clinics of North America: Small Animal Practice》2004,34(5):1245-1271
ATE remains a devastating complication of cardiac disease. Despite some improvements in our understanding of the underlying causes and clinical features of this disease, short-term management remains a challenge, and mortality is high. Long-term mortality is primarily attributable to the severe underlying cardiac disease. Many questions remain to be answered regarding the ideal management approach for feline ATE. The authors' preferred diagnostic and therapeutic approaches for these difficult patients are detailed in Box. 1. 相似文献
5.
Marcelo Gómez DVM Larry Freeman DVM MS Jeryl Jones DVM PhD Otto Lanz DVM Pam Arnold 《Veterinary radiology & ultrasound》2004,45(1):29-37
Computed tomographic (CT) venography of the cervical vertebral canal was performed in six, clinically normal, adult mixed-breed dogs from 14 to 23 kg. After dogs were euthanized and saline perfused, a gelatin and iothalamate mixture was injected into the right external jugular vein. Contiguous, 4-mm-thick CT images were obtained with dogs in sternal recumbency. Dogs were kept in the same position as for the CT scan and frozen to approximately -8 degrees C. All post-contrast CT images were analyzed using similar bone window and level settings. Additional multiplanar reformatted dorsal images were obtained in all dogs. The frozen cadavers were sectioned through the cervical region extending from the occiput to T1 at approximately 8-mm intervals. The frozen sections were then compared with the CT images. The CT appearance of the normal cervical vertebral venous system was described and illustrated. Components such as the internal vertebral venous plexus, interarcuate veins, intervertebral veins, and vertebral veins were clearly identified on the CT images. 相似文献
6.
The isolation and identification of Yersinia enterocolitica from minced meat on CIN agar medium is still one of the major problems in food microbiology because of the low selectivity of cefsulodin–irgasan–novobiocin (CIN) agar. A total of 198 minced meat samples were collected from commercial establishments (butcher shops and supermarkets) in seven German cities in order to investigate the sensitivity and specificity of three identification techniques suitable for the differentiation of Y. enterocolitica within the rich background flora on CIN agar plates. As expected isolation of Y. enterocolitica from minced meat on CIN agar medium after 72 h enrichment in peptone, sorbitol and bile salts (PSB) broth was difficult because all plates were abundantly covered with numerous ‘typical’Yersinia‐like colonies of bull's eye appearance as well as with atypical colonies. Based on the phenotype of the colonies it was possible to detect colonies showing Yersinia‐like growth on CIN agar in 52 samples (26%). For identification of Y. enterocolitica the API 20E system (bioMerieux, Nürtingen, Germany), the Yersinia identification kit (Merlin, Bornheim‐Hersel, Germany) and a 16S rRNA based PCR assay were compared. Only in one sample (0.5%) a Y. enterocolitica strain was detected by all methods. Of the three identification systems tested for routine laboratory diagnostics the API 20E system was found to be the most suitable tool to identify Y. enterocolitica colonies within the rich background flora from minced meat samples on CIN agar plates. 相似文献
7.
Erin L Deters Allison J VanDerWal Katherine R VanValin Stephanie L Hansen 《Journal of animal science》2021,99(6)
To assess the relative bioavailability of bis-glycinate bound Cu, 90 Angus-cross steers (265 ± 21 kg) were blocked by body weight (BW) to pens with GrowSafe bunks and randomly assigned to dietary treatments (14 to 18 steers/treatment): 0 mg supplemental Cu/kg dry matter (DM; CON), 5 or 10 mg supplemental Cu/kg DM as Cu sulfate (CS5; CS10) or bis-glycinate bound Cu (GLY5; GLY10). Steers received a high antagonist growing diet (analyzed 4.9 mg Cu/kg DM, 0.48% S, and 5.3 mg Mo/kg DM). Steers were weighed at the beginning (days 1 and 0) and end (days 125 and 126) of the trial to determine average daily gain (ADG) and gain:feed (G:F). Blood was collected from all steers on days 0, 28, 56, 84, and 126. Liver samples were collected on days −3 or −2 and day 123 or 124. Data were analyzed using ProcMixed of SAS (experimental unit = steer; fixed effect = treatment and block). Plasma Cu was analyzed as repeated measures (repeated effect = day). Plasma and liver Cu concentrations were regressed against total Cu intake using ProcGLM to calculate relative bioavailability of GLY. Final BW and overall ADG were greatest for CS5 and CS10 and least for CON and GLY5 (P = 0.01). Overall, DMI was not affected by treatment (P = 0.14), but overall G:F tended to be greatest for CS5, CS10, and GLY5 and least for CON (P = 0.08). Total and supplemental Cu intake was greatest for steers supplemented either source at 10 mg Cu/kg DM and least for CON (P < 0.01). However, total and supplemental Cu intake was greater for CS5 than GLY5 (P < 0.01). Final liver Cu concentrations were greatest for CS10, least for CON, CS5, and CS10, and intermediate for GLY10 (P < 0.01). Final plasma Cu was greatest for steers supplemented either source at 10 mg Cu/kg DM (P < 0.01). Relative bioavailability of GLY was 82% compared to CS based on liver Cu (P < 0.01) but did not differ based on plasma Cu (P = 0.60). The lesser bioavailability of GLY relative to CS could be due to a high concentration of dietary antagonists and lower solubility of GLY (68.9% relative to CS) in pH conditions (5.2) similar to the ruminal pH of a beef animal consuming a high concentrate diet. Future studies should examine the effects of bis-glycinate bound Cu fed in blended combination with inorganic Cu sulfate to determine the most effective blend of sources for feedlot cattle experiencing varying amounts of dietary Cu antagonists. 相似文献
8.
Bruno I Cappellozza David W Bohnert Maria M Reis Kendall C Swanson Stephanie J Falck Reinaldo F Cooke 《Journal of animal science》2021,99(6)
This experiment evaluated the influence of protein supplementation frequency (SF) and amount offered on intake, nutrient digestibility, and ruminal fermentation by rumen-fistulated beef steers consuming low-quality [2.9% crude protein (CP); dry matter (DM) basis], cool-season forage. Seven Angus × Hereford steers (300 ± 27 kg) fitted with ruminal cannulas were randomly assigned to 1 of 7 treatments in an incomplete 7 × 4 Latin square. Treatments, in a 2 × 3 factorial design plus a non-supplemented control (CON), consisted of 2 levels of supplemental soybean meal, 100% (F) or 50% (H) of the estimated rumen-degradable protein requirement, provided daily (D), once every 5 d (5D), or once every 10 d (10D). Experimental periods were 30 d and dry matter intake (DMI) was measured from days 19 to 28. On days 21 (all supplements provided) and 30 (only daily supplements provided; day immediately prior to supplementation for 5D and 10D treatments) ruminal fluid was collected for ruminal pH, ammonia-N (NH3), volatile fatty acids (VFA), and determination of ruminal fermentation variables. Forage and total DM, organic matter (OM), and nitrogen (N) intake increased with supplementation (P ≤ 0.04). However, a linear effect of SF × amount of supplement interaction was observed for forage and total DM, OM, and N intake (P ≤ 0.04), with each variable decreasing as SF decreased, but the decrease being greater with F vs. H. Apparent total tract DM, OM, and neutral detergent fiber digestibility was not affected by supplementation or amount of supplement provided (P ≥ 0.10). In contrast, N digestibility increased with supplementation and for F vs. H (P < 0.01). Digestibility of DM, OM, and N increased linearly as SF decreased (P ≤ 0.03). When all supplements were provided, ruminal NH3, total VFA, and molar proportions of all individual VFA increased with supplementation (P ≤ 0.04), whereas acetate:propionate ratio decreased (P < 0.01). When only daily supplements were provided, none of the aforementioned fermentation parameters were affected (P ≥ 0.09). In summary, reducing the amount of supplemental CP provided to ruminants consuming low-quality forages, when supplementation intervals are >5 d, can be a management tool to maintain acceptable levels of DMI, nutrient digestibility, and ruminal fermentation while reducing supplementation cost. 相似文献
9.
Bruno I Cappellozza David W Bohnert Maria M Reis Megan L Van Emon Christopher S Schauer Stephanie J Falck Reinaldo F Cooke 《Journal of animal science》2021,99(6)
We evaluated the influence of amount and crude protein (CP) supplementation frequency (SF) on nitrogen (N) use by wethers and the performance of late-gestation beef cows. In exp. 1, seven Western whiteface wethers (31.8 ± 1.4 kg) were used in an incomplete 7 × 4 Latin square to evaluate intake and N use. Wethers received one of the seven treatments in a 2 × 3 factorial design containing two levels of supplemental soybean meal offered at a rate of 100% (F) or 50% (H; 50% of F) of the estimated CP requirement daily, once every 5, or once every 10 d, plus a non-supplemented control (CON). Low-quality cool-season forage (4.9 % CP; dry matter [DM] basis) was provided daily for ad libitum intake. Experimental periods lasted 30 d. In exp. 2, 84 Angus × Hereford cows (560 ± 35 kg) were stratified by age, body condition score (BCS), and expected calving date and allocated to 1 of the 21 feedlot pens (three pens per treatment). Pens were randomly assigned to receive the same treatments as in exp. 1 and cows had free access to low-quality cool-season forage (2.9% CP; DM basis). Cow body weight (BW) and BCS were measured every 14 d until calving and within 24 h after calving. In exp. 1, supplementation did not alter total DM and organic matter (OM) intake (P ≥ 0.26), but both parameters linearly decreased as SF decreased (P = 0.02). Supplementation increased DM, OM, and neutral detergent fiber (NDF) digestibility (P ≤ 0.02). Additionally, F feeding linearly increased DM, OM, and NDF digestibility as SF decreased (P ≤ 0.04). Digestibility of N, N balance, and digested N retained were greater with supplementation (P < 0.01), and N digestibility linearly increased as SF decreased (P = 0.01). Mean plasma urea-N concentration was not only greater (P < 0.01) for supplemented vs. CON wethers but also greater (P = 0.03) for F vs. H. In exp. 2, pre-calving BCS change was greater (P = 0.03) for supplemented cows. A linear effect of SF × supplementation rate for pre-calving BCS change was noted (P = 0.05), as F-supplemented cows lost more BCS compared with H as SF decreased. When considering supplementation intervals greater than 5 d, reducing the quantity of supplement provided, compared with daily supplementation, may be a feasible management strategy to maintain acceptable nutrient use and animal performance while reducing supplement and labor costs. 相似文献
10.