首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   194篇
  免费   26篇
  国内免费   6篇
林业   7篇
农学   1篇
  13篇
综合类   30篇
农作物   4篇
畜牧兽医   161篇
园艺   4篇
植物保护   6篇
  2023年   1篇
  2022年   3篇
  2021年   1篇
  2020年   4篇
  2019年   6篇
  2018年   10篇
  2017年   2篇
  2016年   12篇
  2015年   10篇
  2014年   7篇
  2013年   15篇
  2012年   9篇
  2011年   10篇
  2010年   15篇
  2009年   5篇
  2008年   15篇
  2007年   12篇
  2006年   11篇
  2005年   10篇
  2004年   3篇
  2003年   5篇
  2002年   7篇
  2001年   7篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   5篇
  1995年   2篇
  1994年   5篇
  1993年   6篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1979年   1篇
  1974年   1篇
  1972年   2篇
  1971年   1篇
  1928年   1篇
排序方式: 共有226条查询结果,搜索用时 343 毫秒
1.
At the time of AI following Ovsynch protocol, a total of 51 buffaloes were randomly divided in a first group (n = 30) subjected to conventional AI into the uterine body with 20 million non-sex sorted frozen-thawed spermatozoa, while a second group (n = 21) was inseminated near the utero-tubal junction (UTJ) ipsilateral to the ovary carrying the preovulatory follicle with 2.5 million live (4 million total) sex-sorted frozen-thawed spermatozoa. The semen used for flowcytometric sorting was collected and processed on a farm in Italy, and then shipped to a laboratory in Germany. Eleven buffaloes were inseminated with X-chromosome bearing spermatozoa and 10 with Y-chromosome bearing spermatozoa. Conception rates after conventional and UTJ inseminations were 43.3% (n = 13) and 42.8% (n = 9) respectively (p = 0.97). Eight of the nine foetuses obtained after insemination with sexed spermatozoa corresponded to the sex as predicted by the cell sorting procedure (five male and four female foetuses by ultrasound vs six male and three female foetuses by cell sorting). In conclusion, for the first time buffalo semen has been successfully subjected to procedures for flowcytometric sperm sorting and freezing. Low doses of sexed spermatozoa have been deposited near the UTJ giving conception rates similar to those of conventional AI with full dose.  相似文献   
2.
To determine the plasma pharmacokinetics of suppository acetaminophen (APAP) in healthy dogs and clinically ill dogs. This prospective study used six healthy client‐owned and 20 clinically ill hospitalized dogs. The healthy dogs were randomized by coin flip to receive APAP orally or as a suppository in crossover study design. Blood samples were collected up to 10 hr after APAP dosing. The hospitalized dogs were administered APAP as a suppository, and blood collected at 2 and 6 hr after dosing. Plasma samples were analyzed by ultra‐performance liquid chromatography with triple quadrupole mass spectrometry. In healthy dogs, oral APAP maximal concentration (CMAX=2.69 μg/ml) was reached quickly (TMAX=1.04 hr) and eliminated rapidly (T1/2 = 1.81 hr). Suppository APAP was rapidly, but variably absorbed (CMAX=0.52 μg/ml TMAX=0.67 hr) and eliminated (T1/2 = 3.21 hr). The relative (to oral) fraction of the suppository dose absorbed was 30% (range <1%–67%). In hospitalized ill dogs, the suppository APAP mean plasma concentration at 2 hr and 6 hr was 1.317 μg/ml and 0.283 μg/ml. Nonlinear mixed‐effects modeling did not identify significant covariates affecting variability and was similar to noncompartmental results. Results supported that oral and suppository acetaminophen in healthy and clinical dogs did not reach or sustain concentrations associated with efficacy. Further studies performed on different doses are needed.  相似文献   
3.
A 4-month-old German shepherd puppy developed hindquarter weakness after vaccination with a multivalent vaccine. This is suggestive of post-vaccinal polyradiculoneuritis. To date, only 1 similar case has been reported, which may be due to the under-reporting of suspected adverse drug reactions.  相似文献   
4.
The objectives of this work were to determine the changes in the expression of neuroendocrine markers in Leydig cell by oestradiol treatment, and to determine whether testosterone is able to recover partially the effects of hormonal suppression induced by oestradiol. Adult male rats were injected daily with either 50 microg of oestradiol or oestradiol plus testosterone propionate (25 mg every 3 days) for 15 days. The animals were sacrificed and testicles were dissected and processed by routine histological protocols. FSH and LH serum levels were determined by radioimmunoassay. The visualization of antigens was achieved by the streptavidin-peroxidase immunohistochemical method. Antibodies against chromogranin A (CrA), S-100 protein (S-100), P substance (PS), synaptofisin (SYN), neurofilament protein (NF), gliofibrillary acidic protein (GFAP) and neuron specific enolase (NSE) were used. The mean LH and FSH serum concentrations were consistently suppressed with hormonal treatments. Intermediate filaments (NF and GFAP) showed no difference in their expression. The expression of S-100, NSE and SYN was significantly lower in both hormone-treated groups. In oestradiol-treated rats, the immunoreactivity of CrA and SP decreased significantly but was restored after testosterone supplementation. Although the nature and functions of many of these substances in Leydig cells remain unknown, these results are consistent with the hypothesis that the expression of some neuroendocrine markers is hormonally controlled.  相似文献   
5.
This study determined the impact of porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis coinfection on the pharmacokinetic (PK) profile of ceftiofur hydrochloride in pigs after intramuscular (i.m.) injection. Eighteen clinically normal crossbred gilts were assigned by weight into a challenge group (10 pigs) and control group (eight pigs). Pigs in both groups received a single i.m. injection of ceftiofur hydrochloride (Excenel RTU Sterile Suspension; Zoetis) at a 5 mg/kg BW dose. Serial blood samples were collected to characterize the plasma concentration curve. After a 10 days drug washout period, the challenge group was inoculated with 2 mL of PRRSV isolate VR‐2385 (105.75 50% tissue culture infective doses per mL) intranasally and 8 days later inoculated S. suis. When clinical disease was evident, the second PK assessment began in both challenge and control groups. Coinfected pigs demonstrated lower values of AUC and CMAX, but higher values of Cl/F and Vz/F indicating drug kinetics were altered by infection. The data from this study have implications on ceftiofur treatment regimens in diseased pigs.  相似文献   
6.
The aim of this work was to evaluate the effect of relaxin on fertility parameters of buffalo frozen/thawed sperm. Sperm were incubated in the absence of capacitating agents (negative control), with a known capacitating agent such as heparin (positive control) and with 50 and 100 ng/ml relaxin for 2 and 4 h. Sperm viability, motility, capacitation and the effect of relaxin on the fertilizing ability after heterologous IVF were evaluated. Although viability was not affected, relaxin increased (p < 0.05) sperm motility compared to the negative and positive controls both after 2 h (60.0 ± 2.0, 60.0 ± 3.1, 68.3 ± 1.7 and 69.4 ± 2.7, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) and 4 h (55.0 ± 2.5, 53.3 ± 3.0, 62.2 ± 3.0 and 65.0 ± 3.2, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin) incubation. When sperm were incubated with both 100 ng/ml relaxin and heparin, a decrease (p < 0.01) of pattern A, that is low capacitation level, was observed compared to the negative control both after 2 h (54.4, 34.3 and 36.4%, respectively, in negative control, positive control and 100 ng/ml relaxin) and 4 h (51.9, 35.0 and 34.3%, respectively, in negative control, positive control and 100 ng/ml relaxin). Moreover, an increase (p < 0.01) of pattern EA, that is high capacitation level, was recorded with 100 ng/ml relaxin and heparin compared to the negative control both after 2 h (44.1, 59.3 and 57.7%, respectively, in negative control, positive control and 100 ng/ml relaxin) and after 4 h (43.0, 54.4 and 56.0%, respectively, in negative control, positive control and 100 ng/ml relaxin). Finally, relaxin increased (p < 0.01) cleavage rate compared to the negative control (57.1 ± 4.4, 72.5 ± 6.0, 71.4 ± 5.5 and 73.6 ± 2.9, respectively, in negative control, positive control, 50 and 100 ng/ml relaxin). In conclusion, relaxin has a beneficial effect on motility, capacitation and fertilizing ability of frozen–thawed buffalo sperm.  相似文献   
7.
Agroforestry Systems - The potential of agroforestry systems (AFS) for atmospheric carbon sequestration in degraded tropical lands is of key interest for climate change and rural development...  相似文献   
8.
The objective of this study was to determine the pharmacokinetics of intravenous and oral firocoxib in 10 healthy preweaned calves. Firocoxib (0.5 mg/kg) was initially administered i.v. to calves, and following a 14‐day washout period, animals received firocoxib orally prior to cautery dehorning. Firocoxib concentrations were determined by liquid chromatography–tandem mass spectrometry. Changes in hematology and plasma chemistry were determined using automated methods. Computer software was used to estimate pharmacokinetic parameters best described with a two‐compartment model for i.v. administration and a one‐compartment model for p.o. administration. Following i.v. dosing, the geometric mean (range) T1/2K10 and T1/2β were 6.7 (4.6–9.7) and 37.2 (23.5–160.4) h, respectively, Vss was 3.10 (2.10–7.22) L/kg, and CL was 121.7 (100.1–156.7) mL/h/kg. Following oral administration, geometric mean (range) Cmax was 127.9 (102.5–151.3) ng/mL, Tmax was 4.0 (2.6–5.6) h, and T1/2K10 was 18.8 (14.2–25.5) h. Bioavailability of oral firocoxib was calculated using the AUC derived from both study populations to be 98.4% (83.1–117.6%). No adverse clinical effects were evident following firocoxib administration. Pharmacokinetic analysis of i.v. and p.o. firocoxib indicates high bioavailability and a prolonged terminal half‐life in preweaned calves.  相似文献   
9.
Monensin, a polyether ionophore antibiotic, is potentially an important agent for bloat relief in dairy cows grazing temperate legume-based pasture. A series of studies was undertaken to determine the effect of monensin, when delivered continuously in the rumen of lactating dairy cows by means of controlled-release capsules (monensin CRC). Such devices release approximately 300 mg/head/day for 100 d. A short-term pilot study made at Ruakura, New Zealand, tested monensin CRC in cows selected for high susceptibility to bloat and grazing lucerne (Medicago sativa) or red clover (Trifolium pratense). Treatment significantly reduced the incidence of bloat, while milk yield and protein yield were increased. There was no effect on fat yield. Following the pilot study, 6 large-scale field experiments involving a total of 368 lactating dairy cows, were made in Australia and New Zealand to confirm the effectiveness of monensin CRC for bloat control and to measure the effect of such treatment on milk production and composition. A severe bloat problem occurred in 2 experiments, mild bloat occurred in 2 others, while no visual signs of bloat were observed in the remaining 2 experiments. Bloat was significantly (P less than 0.05) reduced by monensin CRC treatment when data was pooled over the 4 experiments in which bloat occurred. Daily milk yield was increased in all experiments from a mean of 17.7 in untreated groups to 18.8 kg/head/day (P less than 0.05) in monensin CRC-treated cows. Protein percentage was not affected by treatment, while there was a decrease from 4.29 to 4.10% fat, although total fat yield was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
10.
柴达木盆地弃耕地盐渍状况的主分量分析   总被引:30,自引:5,他引:25  
采用主分量分析(PCA)方法对柴达木盆地弃耕地盐渍化状况进行了研究,结果表明,该地属于中重度氯化物盐渍地、耕作层含盐量在0.5%-4.0%之间,盐分表聚强烈,基本无自然淋溶过程。耕作层第一、二主分量显著,累计贡献率高达95.0%左右,反映了该区土壤含盐量及盐离子分布规律,认为全盐量、Cl^-,Mg^2+是该弃耕地盐渍环境的特征因子。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号