全文获取类型
收费全文 | 1188篇 |
免费 | 70篇 |
国内免费 | 10篇 |
专业分类
林业 | 72篇 |
农学 | 79篇 |
基础科学 | 27篇 |
444篇 | |
综合类 | 110篇 |
农作物 | 108篇 |
水产渔业 | 81篇 |
畜牧兽医 | 211篇 |
园艺 | 29篇 |
植物保护 | 107篇 |
出版年
2023年 | 20篇 |
2022年 | 54篇 |
2021年 | 78篇 |
2020年 | 78篇 |
2019年 | 96篇 |
2018年 | 124篇 |
2017年 | 108篇 |
2016年 | 86篇 |
2015年 | 39篇 |
2014年 | 45篇 |
2013年 | 139篇 |
2012年 | 61篇 |
2011年 | 76篇 |
2010年 | 48篇 |
2009年 | 28篇 |
2008年 | 39篇 |
2007年 | 32篇 |
2006年 | 29篇 |
2005年 | 12篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有1268条查询结果,搜索用时 15 毫秒
21.
Yuqin Wu Xiaonan Yin Youli Wang Tahir Mahmood Muhammad Shahid Dafei Yin Jianmin Yuan 《Animal Science Journal》2020,91(1)
This study was aimed to explore the comparative acidifying properties of 2‐hydroxy‐4‐(methylthio) butanoic acid (HMTBA) and a combination of DL‐methionine (DLM) and acidifier in male broiler production. A total of 480 1‐day‐old broiler chicks were randomly divided into four treatments: A (low HMTBA, 0.057% HMTBA); B (low acidifier, 0.05% DLM + 0.057% acidifier); C (high HMTBA, 0.284% HMTBA); and D (high acidifier, 0.25% DLM + 0.284% acidifier). At 21 d, growth performance, chyme pH, digestive enzyme activities, and intestinal microflora were measured. The pH of crop, gizzard, and ileum contents was higher in the HMTBA treatment group than in DLM + acidifier treatment group. Furthermore, acidifier supplementation promoted growth of butyrate‐producing bacteria such as Faecalibacterium, whereas high HMTBA (0.284%) inhibited the proliferation of acid‐producing bacteria including Roseburia and Collinsella. The chymotrypsin activity was lower in the HMTBA group than in the DLM + acidifier group. In contrast, high‐level HMTBA group showed higher average daily gain and average daily feed intake than the DLM + acidifier group. These results suggested that HMTBA work through different pathways with DLM plus acidifier. 相似文献
22.
23.
Estrous expressions in dairy cows have been shortened and weakened. Dairy heifers, on the other hand, may not have had such changes in estrous signs as observed in cows, since they have less stresses than cows. The aim of this study was to describe the duration of estrus in a herd of dairy heifers. A total of 56 Holstein Friesian heifers estrus was synchronized using two different hormonal protocols. They were checked for primary and secondary estrous signs with the help of heat detection devices for 48 h at an interval of 4 h starting at 16.00 hour, one day after PGF2α treatment. Onset and end of standing estrus during 48 h observation period was recorded in 35 of the 44 heifers coming into estrus within 5 days after PGF2α treatment during the observation period. The duration of standing estrus on the average (±SD) was 9.7 ± 5.3 h. Percentage of heifers with standing estrus longer than 12 h was 40%, and 53% showed standing estrus only for 4–8 h. It is indicated that duration of estrus in dairy heifers has been shortened recently. 相似文献
24.
1. A study was designed to investigate the comparative effect of supplementary vitamin E, vitamin C, probiotics and dietary crude protein concentration on semen traits and seminal plasma biochemical parameters in male broiler breeders after Zn-induced moulting. 2. A total of 180 male broiler breeders were induced to moult at 65 weeks of age by mixing ZnO in diet at the rate 3000?mg/kg of feed. After moulting, the males were divided into six groups that were given feed supplemented with: vitamin C (500?IU/kg), vitamin E (100?IU/kg), protein (140?g CP/kg), probiotics (50?mg/kg) and the combination of these components, while one group was kept as a control. Semen samples were collected weekly and semen volume, spermatozoa concentration, motility and dead spermatozoa percentage were determined. Seminal plasma was separated to determine the concentration of total antioxidant capacity (TAC), homocysteine, paraoxonase (PON1), arylesterase, ceruloplasmin, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. 3. Semen volume was significantly higher in the vitamin E and C groups compared to the control. Spermatozoa motility was higher in the vitamin E group and dead spermatozoa percentage was significantly lower in the vitamin C group compared with the control group. 4. Seminal plasma TAC was higher in the vitamin E group, homocysteine was lower in the vitamin C and E groups. PON1 was higher in the combination group. Arylesterase increased significantly in the vitamin C and combination groups over time. Seminal plasma AST was significantly lower in the vitamin C and E supplemented groups whereas ALT decreased significantly only in the vitamin E group compared with the control. Higher concentrations of ceruloplasmin were observed in the combination group compared with the other treatments. 5. It was concluded that additional vitamin E and C or their combination was the most potent nutrient treatment for improving the semen traits and seminal plasma biochemical characteristics in male broiler breeders after Zn-induced moulting. 相似文献
25.
Mahr-un-Nisa Shahzad MA Phillips CJ Sarwar M 《Tropical animal health and production》2012,44(5):947-952
Urea is a common ingredient of the diets of intensively fed lambs, but is increasingly required for industrial processes.
Maize steep liquor (MSL) is a by-product of maize grain degradation to produce starch that may be a suitable replacement.
Fifty growing lambs were fed on equinitrogenous diets in which between 0% and 80% of the urea was replaced by MSL; their growth
and metabolism were recorded over 70 days. Increasing replacement of urea by MSL increased feed intake and nutrient digestibilities,
leading to increased growth rates, more efficient feed conversion, and increased nitrogen retention. Concentrations of triiodothyroxin,
thyroxin, glucose, and methionine were increased by replacement of urea by liquor, and plasma urea was reduced. This study
suggests that MSL is a suitable replacement for up to 80% of urea in the diet of rapidly growing lambs. 相似文献
26.
Qaisar Shahzad Muhammad Waqas Liping Pu Armughan Ahmed Wadood Long Xie Asma Ul Husna Kailin Yang Jingyuan Wang Huiyan Xu Kehuan Lu Yangqing Lu 《Reproduction in domestic animals》2020,55(9):1115-1123
Buffalo is considered short-day breeder in tropical and subtropical part of the world and seasonality and photoperiodism impart major influence on its fertility. However, its impact on in vitro embryo production (IVEP) remains elusive. Therefore, this study investigated the effect of seasonal variations and photoperiodism on morphological and molecular parameters of IVEP in buffalo. For this purpose, we conducted two different experiments on the oocytes obtained by aspirating follicles from abattoir derived ovaries. In Exp. I, retrospective analysis was performed for oocyte recovery, blastocyst and hatching rate, during four consecutive seasonal periods (i.e. January–March, April–June, July–September and October–December). In Exp. II, oocytes from peak breeding and non-breeding seasons were subjected to 24 hr in vitro maturation and evaluated for polar body extrusion to assess maturation rate. Results showed that embryo development was markedly low during second quarter (April–June) and maximum during fourth quarter (October–December) of the year; referred as non-breeding and breeding seasons, respectively. Comparative data analysis demonstrated that poor oocyte quality is major reason for lesser efficiency of embryo production during non-breeding season than peak breeding season as suggested by poor oocyte recovery (2.31 ± 0.10 vs. 3.65 ± 0.27) and maturation rate (33.32 ± 2.1 vs. 63.15 ± 7.31). Subsequently, comparative gene expression analysis of blastocysts during peak breeding season significantly upregulated pluripotency gene (OCT-4) and downregulated heat shock protein 90, as compared to non-breeding season. Therefore, it could be divulged from the present study that seasonal variations and photoperiodism have profound effect on oocyte quality and subsequent embryo development. It is recommended to find suitable additives for in vitro maturation that could mitigate seasonal effects. 相似文献
27.
Mubbashar Hassan Usman Arshad Güneş Erdoğan Nasim Ahmad 《Reproduction in domestic animals》2020,55(10):1425-1433
The objectives of the study were to evaluate haemodynamic changes and their relationships among ipsilateral (IPS) and contralateral (CONT) uterine arteries (UA) during different stages of pregnancy in Bos indicus cows. Multiparous pregnant cows (n = 40) having a gestation length 30.47 ± 0.54 (mean ± SD) days were randomly enrolled and subjected to Doppler ultrasonography sequentially at 1st, 2nd, 4th, 6th and 8th months of gestation. Blood flow indices including diameter of UA (mm), blood flow volume (BFVo, ml/min), blood flow velocity (BFVe, cm/s), time-averaged maximum velocity (TAMV, cm/s), pulsatility index (PI) and resistance index (RI) were recorded. Data were analysed with mixed models using the PROC MIXED procedures, and Pearson correlation coefficients were calculated using the PROC CORR statement in SAS. The final statistical models included the fixed effects of side of UA, gestation month and the interaction between side of UA and gestation month. Results revealed that the mean diameter of the UA (12.13 ± 0.22 vs. 10.09 ± 0.22), BFVo (1236.33 ± 0.55 vs. 770.41 ± 0.55), BFVe (17.18 ± 0.42 vs. 15.58 ± 0.42) and TAMV (17.11 ± 0.44 vs. 15.77 ± 0.44) was higher (p < .05) in IPS as compared to CONT side of the UA in cows. However, PI and RI did not differ between IPS and CON arteries of uterus in cows. A very high and positive correlation (r = .89; p < .05) existed between the diameter of UA and BFVo starting from 1st to 8th months of gestation in IPS as well as CONT sides of UA. Moreover, TAMV was highly and positively correlated (r = .91; p < .05) with BFVe throughout the gestation. In conclusion, these haemodynamic changes in the UA could be used as a valuable validity tool to differentiate the compromised pregnancy in Bos indicus cows. 相似文献
28.
Kifah Jumaah Odhaib Kazeem Dauda Adeyemi Muideen Adewale Ahmed Muhammad Faseleh Jahromi Shokri Jusoh Anjas Asmara Samsudin Abdul Razak Alimon Halimatun Yaakub Awis Qurni Sazili 《Tropical animal health and production》2018,50(5):1011-1023
The objective of this study was to determine the effects of dietary supplementation of Nigella sativa L. seeds, Rosmarinus officinalis L. leaves and their combination on rumen metabolism, nutrient intake and digestibility, growth performance, immune response and blood metabolites in Dorper lambs. Twenty-four entire male Dorper lambs (18.68?±?0.6 kg, 4–5 months old) were randomly assigned to a concentrate mixture containing on a dry matter basis either, no supplement (control, T1), 1% R. officinalis leaves (T2), 1% N. sativa seeds (T3) or 1% R. officinalis leaves +1% N. sativa seeds (T4). The lambs had ad libitum access to urea-treated rice straw (UTRS) and were raised for 90 days. Supplemented lambs had greater (P?< 0.05) intake of DM and UTRS than the control lambs. The T4 lambs had lower (P?< 0.05) nutrient digestibility than those fed other treatments. Total and daily weight gain was greater (P?< 0.05) in T2 lambs than those fed other diets. The T3 and T4 lambs had greater (P?< 0.05) ruminal pH than the T1 and T2 lambs. Supplemented lambs had lower (P?<?0.05) ruminal total volatile fatty acids, acetate, propionate, NH3-N and C18:0 than the control lambs. The T4 lambs had lower (P?< 0.05) population of Fibrobacter succinogenes, Ruminococcus albus, methanogens and total protozoa compared with those fed other diets. Supplemented lambs had lower (P?< 0.05) neutrophils, basophils and serum urea and greater (P?<?0.05) serum IgA and IgG compared with the control lambs. The current results emphasised the variation in the efficacy of medicinal plants in ruminant nutrition. 相似文献
29.
Muhammad Saeed Daryoush Babazadeh Muhammad Naveed Muhammad Asif Arain Faiz Ul Hassan Sun Chao 《Tropical animal health and production》2017,49(7):1329-1338
Betaine is found ubiquitously in plants, animals, microorganisms, and rich dietary sources including seafood, spinach, and wheat bran. The chief physiological role of betaine is to function as a methyl donor and an osmolyte. Betaine also acts as an osmolyte, to maintain the avian’s cellular water and ion balance to improve the avian’s capacity against heat stress via preventing dehydration and osmotic inactivation. It helps in maintaining the protective osmolytic activity, especially in heat-stressed birds. Betaine may promote various intestinal microbes against osmotic variations and thus improve microbial fermentation activity. Previous studies showed that dietary supplementation of betaine in poultry diets could positively affect nutrients’ digestibility, reduce abdominal fat weight, and increase breast meat yield. In addition, betaine has been reported to protect internal organs and boost their performance. Its inclusion in poultry diet is sparing essential amino acids like choline and methionine. In addition, it may play an important role in lean meat production by positively affecting the lipid metabolism with increased fatty acids catabolism and thus reducing carcass fat deposition. The aim of this review article was to broaden the knowledge regarding betaine and its importance in the poultry industry to cope with the heat stress problem. Moreover, it should be added to the diet as a natural anti-stressor through different routes (water/feed) to overcome the heat stress problem. However, further studies need to be conducted at the genetic and molecular basis to elucidate the mechanism behind the betaine as a natural anti-heat agent to decrease the heat stress problem in the poultry industry. 相似文献
30.
This project was conducted to investigate the comparative efficiency of competitive ELISA (cELISA), standard Agar Gel Immunodiffusion
Test (AGID) and Precipitinogen Inhibition Test (PIT) for the diagnosis of Peste des Petits Ruminants (PPR) in Pakistan. To deal with this, serum samples from 198 sheep and 82 goats were collected from three different government
livestock farms and all the samples were run simultaneously with the three serological tests. The samples found positive for
PPR antibodies through cELISA, AGID and PIT were 96 (34.2%), 60 (21.4%) and 72 (25.7%), respectively. Kappa statistics were
applied to evaluate the concordance between the laboratory-based test (cELISA) and field-based tests (AGID and PIT). Kappa
statistics scores for cELISA versus AGID and PIT were 0.6343 (95% Confidence Interval CI 0.5231–0.7456) and 0.7134 (95% Confidence
Interval CI 0.5987–0.8281), respectively, which indicate a “substantial” agreement between cELISA and AGID and “significant”
agreement between cELISA and PIT. AGID and PIT revealed relative diagnostic sensitivities with cELISA of 59.3% and 69.7% and
relative diagnostic specificities of 98.3% and 97.2%, respectively. The data suggested that for mass screening and control
of PPR, these serological tests proved practical in the absence of cELISA since they have high relative diagnostic specificities
and a satisfactory relative diagnostic sensitivities. 相似文献