全文获取类型
收费全文 | 359篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
林业 | 18篇 |
农学 | 3篇 |
基础科学 | 4篇 |
53篇 | |
综合类 | 64篇 |
农作物 | 8篇 |
水产渔业 | 20篇 |
畜牧兽医 | 204篇 |
园艺 | 1篇 |
植物保护 | 12篇 |
出版年
2023年 | 3篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2012年 | 23篇 |
2011年 | 22篇 |
2010年 | 10篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 15篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1995年 | 3篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1979年 | 3篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1957年 | 2篇 |
1941年 | 2篇 |
1938年 | 2篇 |
排序方式: 共有387条查询结果,搜索用时 562 毫秒
141.
Etienne Cté DVM Maureen C. Carroll DVM Kathy A. Beck DVM Lillian Good DVM Kristi Gannon DVM 《Veterinary radiology & ultrasound》2002,43(3):281-286
Because urinary bladder rupture can be life threatening, a simple, safe technique for evaluating patients is desirable. Current diagnostic protocols involve radiographic imaging, but ultrasound-based contrast techniques have not been methodically evaluated in veterinary patients with urologic trauma. Ultrasound contrast cystography (contrast cystosonography) involves infusion of microbubbled saline solution through a urinary catheter. It was performed in an in vitro model and in 2 dogs with naturally occurring urinary bladder rupture. A positive result consisted of visualizing microbubbles sonographically in fluid surrounding the bladder immediately after infusion of contrast into the urinary catheter. A positive result was obtained both in the in vitro model and in the 2 dogs, with radiographic and surgical confirmation of naturally occurring intraperitoneal urinary bladder rupture in the dogs. Based on the results of this study, ultrasound contrast cystography appears to be more sensitive than two-dimensional (2D) abdominal sonography for detecting naturally occurring urinary bladder rupture in dogs. 相似文献
142.
143.
Beck PA Hutchison S Gunter SA Losi TC Stewart CB Capps PK Phillips JM 《Journal of animal science》2007,85(2):545-555
Three sorghum x Sudangrass hybrids were planted in twelve 0.2-ha plots to test the effect of date of harvest and hybrid on plant maturity, DM yield, chemical composition, and in situ DM and fiber disappearance. Sweet Sunny Sue (a non-brown midrib (BMR) hybrid; nonBMR), NutriPlus BMR (a BMR hybrid; NP-BMR), and Dry Stalk BMR (a BMR hybrid; DS-BMR) were planted on 26 June 2003 at 22.4 kg of seed/ha. Beginning 34 d after planting, plant height and phenological growth stage were assessed weekly in 10 random, 0.5-m(2) quadrats per plot. Plants were clipped to 2.5 cm in height and analyzed for CP, NDF, and ADF using near-infrared spectroscopy. Composite samples harvested from each plot on d 34, 48, and 63 were incubated in the rumen of 3 steers to determine the in situ disappearance of DM and NDF in a 3 x 3 Latin square. Forage yield was greater (P < or =0.02) for nonBMR than NP-BMR on d 41 and 55 and tended (P = 0.08) to be greater on d 48. The DS-BMR hybrid produced more (P = 0.04) forage DM than the NP-BMR on d 48. When DM yield was regressed on growth stage at harvest, BMR hybrids were predicted to produce 265 kg/ha more DM (P < 0.01) than nonBMR, at the late-boot stage. At all harvest dates, NDF concentrations were less (P < or =0.02) for BMR than nonBMR. The DS-BMR had greater (P < or =0.02) NDF concentrations than NP-BMR on d 41, 48, 55, and 63. Detergent fiber concentrations were predicted to be greater (P < 0.01) in nonBMR than BMR when regressed on growth stage at harvest, but the magnitude of the differences in fiber concentration diminished with growth stage. The A fractions of DM and NDF were greater (P < 0.01) and the C fraction was less (P < 0.01) for BMR hybrids than nonBMR. The B fraction of DM was not affected (P = 0.15) by hybrid type. The B fraction of NDF was not different (P = 0.28) on d 34 but was greater (P < 0.01) on d 48 and 63 for BMR than nonBMR. Effective degradability of NDF and DM was greater (P < 0.02) for BMR than nonBMR on all harvest dates. The A fraction of DM was less for DS-BMR than NP-BMR (P < 0.01), but the B and C fractions of NDF and DM did not differ (P > 0.13) between BMR hybrids. This research indicates that forage chemical composition and ruminal in situ disappearance are improved in the BMR sorghum x Sudangrass hybrids tested compared with the nonBMR. Yield reductions are commonly reported for BMR hybrids, but predicted DM yields in the current study were not reduced if harvested at a similar phenological growth stage. 相似文献
144.
145.
NCG Pieri AF Souza JB Casals KCS Roballo CE Ambrósio DS Martins 《Reproduction in domestic animals》2015,50(4):625-631
The precise determination of the embryonic chronology is very important in reproductive biotechnologies, especially in estimating embryonic age. Thus, there is a need for greater knowledge and standardization for determining the chronology of embryonic development and functional morphology. We describe aspects of embryonic development in two domestic carnivores to add knowledge about organ peculiarities and for application in veterinary practice, in prenatal development and in the biotechnology fields. We found that the development of differential characteristics of embryonic organs occurs in the first trimester of pregnancy for both species. Thus, using the combination of the crown‐rump length, macroscopic analysis and optical microscopy, it is possible to predict gestational age more precisely in animals that lack a defined breed and establish an embryonic pattern. 相似文献
146.
Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby 总被引:1,自引:0,他引:1
DK Yeomans J Barriot DW Dunham RW Farquhar JD Giorgini CE Helfrich AS Konopliv JV McAdams JK Miller WM Owen DJ Scheeres SP Synnott BG Williams 《Science (New York, N.Y.)》1997,278(5346):2106-2109
The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter. 相似文献
147.
M Wüst J Reindl S Fuchs T Beck A Mosandl 《Journal of agricultural and food chemistry》1999,47(8):3145-3150
A novel enantioselective synthesis of nerol oxide (3, 6-dihydro-4-methyl-2-(2-methyl-1-propenyl)-2H-pyran) was used for the determination of the absolute configuration at C-2. The order of elution of the enantiomers on octakis-(2, 3-di-O-butyryl-6-O-tert-butyldimethylsilyl)-gamma-cyclodextrin in OV 1701-vi as the chiral stationary phase in enantioselective GC was determined as (2R) before (2S). Enantioselective multidimensional GC/MS (enantio-MDGC/MS) was used for the determination of the enantiomeric ratios of nerol oxide in different geranium oils. As a result, in all investigated oils nerol oxide occurs as a racemate. The biogenesis of nerol oxide in Pelargonium species was investigated by feeding experiments using deuterium-labeled neryl glucoside as the precursor. The Pelargonium plants were able to convert the fed precursor into racemic nerol oxide, which has to be considered as a "natural racemate". 相似文献
148.
149.
Simplified strigolactams as potent analogues of strigolactones for the seed germination induction of Orobanche cumana Wallr. 下载免费PDF全文
150.
Beck JJ Staatz AJ Pelsue DH Kudnig ST MacPhail CM Seim HB Monnet E 《Journal of the American Veterinary Medical Association》2006,229(12):1934-1939
OBJECTIVE: To evaluate risk factors associated with death and development of perioperative complications in dogs undergoing surgery for treatment of gastric dilatation-volvulus (GDV). DESIGN: Retrospective case series. ANIMALS: 166 dogs. PROCEDURES: Records of dogs with confirmed GDV that underwent surgery were reviewed. Logistic regression was performed to identify factors associated with development of complications (ie, hypotension, arrhythmias, gastric necrosis necessitating gastrectomy, disseminated intravascular coagulation, peritonitis, sepsis, postoperative dilatation, postoperative vomiting, and incisional problems) and with short-term outcome (ie, died vs survived to the time of suture removal). RESULTS: Short-term mortality rate was 16.2% (27/166). Risk factors significantly associated with death prior to suture removal were clinical signs for > 6 hours prior to examination, combined splenectomy and partial gastrectomy, hypotension at any time during hospitalization, peritonitis, sepsis, and disseminated intravascular coagulation. Partial gastrectomy was not a significant risk factor for death but was for peritonitis, disseminated intravascular coagulation, sepsis, and arrhythmias. Age, gastrectomy, and disseminated intravascular coagulation were risk factors for development of hypotension. Use of a synthetic colloid or hypertonic saline solution was associated with a significantly decreased risk of hypotension. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the prognosis for dogs undergoing surgery because of GDV is good but that certain factors are associated with an increased risk that dogs will develop perioperative complications or die. 相似文献