全文获取类型
收费全文 | 589篇 |
免费 | 22篇 |
专业分类
林业 | 17篇 |
农学 | 52篇 |
7篇 | |
综合类 | 7篇 |
农作物 | 3篇 |
水产渔业 | 21篇 |
畜牧兽医 | 471篇 |
园艺 | 1篇 |
植物保护 | 32篇 |
出版年
2020年 | 8篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 9篇 |
2012年 | 13篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 48篇 |
2008年 | 15篇 |
2007年 | 25篇 |
2006年 | 22篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 27篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 5篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有611条查询结果,搜索用时 187 毫秒
1.
DAVID A. JIMNEZ ROBERT T. O'BRIEN JOHNA D. WALLACE EMILY KLOCKE 《Veterinary radiology & ultrasound》2011,52(2):196-200
Nine normal juvenile dogs were evaluated with direct jejunal contrast‐enhanced ultrasonography via midline celiotomy. Three different doses of ultrasound contrast medium (Definity®) were injected through a peripheral venous catheter. Time‐intensity curves were used to calculate baseline, time to initial rise, inflow slope, time‐to‐peak, peak intensity (PI), and outflow slope for each administered dose. PI was directly proportional to dose. Outflow slope was similar for all patients, independent of dose. The most favorable images were acquired with a dose of 0.030 ml/kg given as a rapid intravenous manual bolus. The technique and normal jejunal perfusion pattern described herein may provide useful data for evaluation of intestinal vascular, inflammatory, and neoplastic disease in the dog. 相似文献
2.
3.
Hepatic myelolipoma incarcerated in a peritoneopericardial diaphragmatic hernia was diagnosed in an 11-year-old, desexed female Persian cat. The cat was initially referred for investigation of tachypnoea and dyspnoea. Peritoneopericardial diaphragmatic hernia is a common incidental finding in cats and is usually asymptomatic. Myelolipoma is an extremely rare benign tumour, composed of extramedullary haematopoietic cells and adipose tissue. Myelolipomas are hypothesised to result from metaplastic alteration, rather than a neoplastic process, although this theory cannot be substantiated. The present case is only the fourth report of such an unusual occurrence in cats and displays significant differences to previous reports. Hepatic entrapment and burgeoning of the mass within the pericardial sac resulted in cardiac tamponade and overt signs of right-sided cardiac failure. Surgical intervention was successful and despite concerns regarding the cat's clinical presentation and the gross appearance of the lesion(s), a good long-term outcome is anticipated. 相似文献
4.
LEWIS INCZE HUIJIE XUE NICHOLAS WOLFF DANYA XU CARL WILSON ROBERT STENECK RICHARD WAHLE PETER LAWTON NEAL PETTIGREW YONG CHEN 《Fisheries Oceanography》2010,19(1):1-20
We used a coupled biophysical model to investigate larval transport and connectivity patterns in the Gulf of Maine lobster ( Homarus americanus ) population. Biological 'particles' were released at over 21 000 locations every 10 days over a 4-month hatching period, and were followed from hatching through late postlarval stage. In addition to circulation and dispersion, model calculations included spatial patterns of egg production, temporal patterns of hatching, temperature-dependent development, vertical distribution and mortality. We ran the model for three larval production seasons using the same hatching patterns and individual-based modeling parameters but different flow patterns in the coastal current system. Model results gave distribution and abundance patterns of competent postlarvae that closely resembled observed, alongshore patterns of lobster settlement density. We evaluated the relative contribution of all source regions to the total number of competent postlarvae in a series of medium-size zones along the coastal shelf, many of which are used in lobster management. Connectivity depended on many factors, including patterns of egg production and transport, and the location and size of the receiving zones. Self recruitment ranged from a few percent to >90% of competent postlarvae. Although it was common for postlarvae to come from many, often distant, sources, most of the competent postlarvae in a zone originated within one to two zones in the prevailing 'up-stream' direction, forming shorter connections along the coast than the energetic currents might otherwise suggest. Inshore migrations during summer hatching may contribute to these shorter patterns of connectivity. Transport in the prevailing 'upstream' direction was also indicated. 相似文献
5.
6.
7.
NADER SOLTANI ROBERT E. NURSE DARREN E. ROBINSON PETER H. SIKKEMA 《Weed Biology and Management》2008,8(1):25-30
Four field trials were conducted over a 2 year period at Exeter (2005, 2006), Harrow (2006), and Ridgetown (2006), Ontario, Canada, to evaluate the tolerance of pinto and small red Mexican (SRM) beans to the preplant-incorporated (PPI) application of trifluralin, dimethenamid, S -metolachlor, KIH-485, imazethapyr, and flumetsulam. All the treatments, including the untreated control, were maintained weed-free during the growing season. The PPI application of trifluralin, dimethenamid, and S -metolachlor resulted in minimal transient visual injury, with no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of the pinto and SRM beans. The PPI application of imazethapyr and flumetsulam, especially at the high rate, initially caused 13% injury and reduced the plant height and shoot dry weight by 15 and 28%, respectively, but these injuries were transient and had no effect on the seed maturity and yield of the pinto and SRM beans. The PPI application of KIH-485 caused 80% injury to the pinto and SRM beans and reduced the plant height, shoot dry weight, and yield. The dry bean maturity was also delayed. Based on these results, trifluralin, dimethenamid, S -metolachlor, imazethapyr, and flumetsulam, applied as PPI herbicides, have the potential to be used in a weed management program for pinto and SRM beans. However, KIH-485, applied as a PPI herbicide at the doses evaluated, does not have an adequate margin of crop safety for use in pinto and SRM bean production in Ontario. 相似文献
8.
ROBERT MARSH BRIAN PETRIE CHRISTOPHER R. WEIDMAN ROBERT R. DICKSON JOHN W. LODER CHARLES G. HANNAH KENNETH FRANK & KEN DRINKWATER 《Fisheries Oceanography》1999,8(1):39-49
A mass mortality of `warm-water' tilefish in the Middle Atlantic Bight between April and August of 1882 suggests an episode of extreme cold in the shelf waters off the north-eastern United States. This cooling is hypothesized to be a consequence of enhanced equatorwards transport of cold water in the Labrador Current, coincident with a minimum in the North Atlantic Oscillation (NAO) index during the early 1880s.
Although there is little direct evidence for this historical event, an analogue for the 1880s cooling is found in the 1960s, at the most recent NAO-index minimum. Post-1945 observations in the Middle Atlantic Bight / Gulf of Maine region reveal changes in winter baroclinic circulation between cool and warm decades, with greater equatorward penetration of south-westwards flow along the shelf-edge during the cool 1960s. Over the period 1934–77, the NAO is found to account for 17% of the interannual variance in Labrador Current transport around the Grand Banks.
Proxy evidence for the cold episode of the early 1880s is sought. Records of bottom temperature in the Middle Atlantic Bight region are reconstructed using stable oxygen isotopic analysis on the annual bands of shells of a bivalve mollusc ( Arctica islandica ) and an empirical model of covariability with local air temperature. The result is confirmation of the presence of anomalously cold water during the early 1880s. 相似文献
Although there is little direct evidence for this historical event, an analogue for the 1880s cooling is found in the 1960s, at the most recent NAO-index minimum. Post-1945 observations in the Middle Atlantic Bight / Gulf of Maine region reveal changes in winter baroclinic circulation between cool and warm decades, with greater equatorward penetration of south-westwards flow along the shelf-edge during the cool 1960s. Over the period 1934–77, the NAO is found to account for 17% of the interannual variance in Labrador Current transport around the Grand Banks.
Proxy evidence for the cold episode of the early 1880s is sought. Records of bottom temperature in the Middle Atlantic Bight region are reconstructed using stable oxygen isotopic analysis on the annual bands of shells of a bivalve mollusc ( Arctica islandica ) and an empirical model of covariability with local air temperature. The result is confirmation of the presence of anomalously cold water during the early 1880s. 相似文献
9.
CHRISTIE L. STEWART ROBERT E. NURSE CHRIS GILLARD PETER H. SIKKEMA 《Weed Biology and Management》2010,10(1):40-47
Weed management options for adzuki-bean growers in Ontario, Canada are limited due to few herbicide registrations. Four field trials were conducted at three locations in south-western Ontario in 2007 and 2008 to determine the tolerance of adzuki bean to several preplant-incorporated (PPI), pre-emergence (PRE), and post-emergence (POST) herbicides. All the herbicides were applied at the doses registered for use in soybean. The application of pendimethalin, cloransulam-methyl, and halosulfuron-methyl (PPI), flumetsulam, cloransulam-methyl, and halosulfuron-methyl (PRE), and acifluorfen and fomesafen (POST) caused ≤15% crop injury; however, the injury was transient and did not reduce the adzuki bean yield. The POST application of cloransulam-methyl and imazethapyr caused ≤23% crop injury and reduced the biomass by ≤50%, but did not reduce the plant height or crop yield. Metribuzin, flumetsulam, atrazine, and pyroxasulfone (PPI), metribuzin, linuron, pyroxasulfone, and atrazine (PRE), and bentazon, imazethapyr plus bentazon, halosulfuron-methyl, and thifensulfuron-methyl (POST) caused ≤61% crop injury. These treatments reduced the biomass, plant height, and crop yield. Based on these results, pendimethalin, cloransulam-methyl, and halosulfuron-methyl applied PPI, flumetsulam, cloransulam-methyl, and halosulfuron-methyl applied PRE, and acifluorfen and fomesafen applied POST might be potential weed management options for weed management in adzuki bean. Cloransulam-methyl and imazethapyr applied POST will need further evaluation due to phytotoxicity concerns. Metribuzin, flumetsulam, atrazine, and pyroxasulfone applied PPI, metribuzin, linuron, atrazine, and pyroxasulfone applied PRE, and bentazon, imazethapyr plus bentazon, halosulfuron-methyl, and thifensulfuron-methyl applied POST did not have an adequate margin of safety. 相似文献
10.