全文获取类型
收费全文 | 132766篇 |
免费 | 7288篇 |
国内免费 | 93篇 |
专业分类
林业 | 5396篇 |
农学 | 4281篇 |
基础科学 | 832篇 |
17087篇 | |
综合类 | 21523篇 |
农作物 | 5402篇 |
水产渔业 | 6700篇 |
畜牧兽医 | 68112篇 |
园艺 | 1805篇 |
植物保护 | 9009篇 |
出版年
2020年 | 1183篇 |
2019年 | 1378篇 |
2018年 | 2038篇 |
2017年 | 2336篇 |
2016年 | 2102篇 |
2015年 | 1747篇 |
2014年 | 2235篇 |
2013年 | 5306篇 |
2012年 | 4127篇 |
2011年 | 5115篇 |
2010年 | 3256篇 |
2009年 | 3402篇 |
2008年 | 4990篇 |
2007年 | 4687篇 |
2006年 | 4372篇 |
2005年 | 4107篇 |
2004年 | 3865篇 |
2003年 | 3986篇 |
2002年 | 3557篇 |
2001年 | 4156篇 |
2000年 | 4254篇 |
1999年 | 3373篇 |
1998年 | 1478篇 |
1997年 | 1390篇 |
1996年 | 1289篇 |
1995年 | 1531篇 |
1994年 | 1359篇 |
1993年 | 1233篇 |
1992年 | 2584篇 |
1991年 | 2702篇 |
1990年 | 2591篇 |
1989年 | 2613篇 |
1988年 | 2371篇 |
1987年 | 2349篇 |
1986年 | 2430篇 |
1985年 | 2342篇 |
1984年 | 1883篇 |
1983年 | 1681篇 |
1982年 | 1149篇 |
1979年 | 1750篇 |
1978年 | 1398篇 |
1977年 | 1152篇 |
1976年 | 1214篇 |
1975年 | 1292篇 |
1974年 | 1501篇 |
1973年 | 1516篇 |
1972年 | 1406篇 |
1971年 | 1304篇 |
1970年 | 1253篇 |
1969年 | 1284篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
Freitas Ana C. Stafuzza Nedenia B. Barbero Marina M. D. Santos Daniel J. A. Fortes Marina R. S. Tonhati Humberto 《Tropical animal health and production》2020,52(1):415-423
Tropical Animal Health and Production - Animal breeding programs have used molecular genetic tools as an auxiliary method to identify and select animals with superior genetic merit for milk... 相似文献
992.
Faccin J. E. G. Laskoski F. Quirino M. Gonçalves M. A. D. Mallmann A. L. Orlando U. A. D. Mellagi A. P. G. Bernardi M. L. Ulguim R. R. Bortolozzo F. P. 《Tropical animal health and production》2020,52(3):1073-1079
Tropical Animal Health and Production - Housing nursery pigs according to body weight is an observed common practice in production systems and, supposedly, improves growth performance and reduces... 相似文献
993.
Robles Jimenez Lizbeth E. Ruiz Perez Jose A. Nicolas Di Lorenzo Chay Canul Alfonso J. Ramirez-Rivera Julio Cesar Villegas-Estrada Daniela Vargas-Bello-Pérez Einar Gonzalez-Ronquillo Manuel 《Tropical animal health and production》2020,52(3):1257-1267
Tropical Animal Health and Production - Currently for the reduction of methane (CH4) emissions are using fodder rich in condensed tannins, however, not yet known exactly how they act in the rumen... 相似文献
994.
To examine the effect of a modification of a typically Irish dairy calf-to-beef production system, Charolais × Friesian steers were offered a finishing ration of grass silage ad libitum and 5.6 kg concentrates daily for 174 days prior to slaughter at 25 months of age or grass silage ad libitum for 174 days, followed by pasture for 167 days and slaughter at 30 months of age. Finishing at pasture increased carcass weight (376 vs. 342 kg) but did not affect intra-muscular lipid concentration (28 vs. 24 g/kg). Finishing at pasture decreased Longissimus thoracis et lumborum lightness (35.6 vs. 36.9) and increased shear force of muscle at 2 (8.54 vs 4.32) and 7 days (5.21 vs 3.64 kg) post-mortem but not at 14 days post-mortem (4.45 vs. 3.42 kg). Finishing at pasture did not affect the sensory characteristics of tenderness, juiciness, firmness or chewiness and tended (P < 0.1) to decrease texture and acceptability. It is concluded that modification of this beef production system as described, had minor effects on beef quality which are unlikely to be of commercial significance. 相似文献
995.
Christopherson PW Insalaco TA van Santen VL Livesey L Bourne C Boudreaux MK 《Veterinary pathology》2006,43(1):78-82
Glanzmann thrombasthenia (GT) is an inherited, intrinsic platelet defect characterized by a quantitative or qualitative change in the platelet glycoprotein complex IIb-IIIa (integrin alpha(IIb)beta3). The subunits are encoded by separate genes and both subunits must be expressed for a stable complex to form on the platelet surface; therefore, a defect in either gene can result in GT. 相似文献
996.
997.
Gardner RB Hart KA Stokol T Divers TJ Flaminio MJ 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2006,20(1):198-203
A 5-week-old Fell Pony colt was examined for fever, lethargy, and anemia. The colt had been lethargic for 1 week before examination, had continued to nurse, had a temperature of 104°F (40°C), and was treated with ceftiofur (5 mg/kg IM q12h). Approximately 36 hours before examination, the colt developed watery diarrhea. Blood work performed by the referring veterinarian on the day of admission revealed a PCV of 10%. 相似文献
998.
Liste G María GA Buil T García-Belenguer S Chacón G Olleta JL Sañudo C Villarroel M 《DTW. Deutsche tier?rztliche Wochenschrift》2006,113(2):59-64
The transport of domestic animals by road can increase levels of stress and decrease meat quality, especially in unfavourable climates. The purpose of this study was to investigate the effect of journey duration and vertical position on the transport truck on some physiological indicators of stress and on instrumental meat quality parameters in commercial rabbits. In the summer months (June and July, 2003), 78 rabbits were subjected to either long (7 h) (LJ) or short (1 h) (SJ) journeys (3 replicates each, n = 6) between the farm and an abattoir in northern Spain. The position (top, middle, or bottom) occupied by the rabbits on the Multi-Floor cage Rolling Stand (MFRS) of the transport truck was recorded. Blood samples were collected at sticking and meat pH was measured at 24 h post-mortem (pH24). At 48 h post-mortem, samples of the M. longissimus dorsi were used to determine water-holding capacity (WHC) and instrumental tenderness using an INSTRON machine. The levels of corticosterone, glucose, lactate, and creatine kinase were slightly higher in LJ than in SJ samples, but the difference was not statistically significant (p < or = 0.10). Independent of journey length, rabbits in the middle and bottom of the MFRS showed higher levels (p < or = 0.05) of glucose and creatine kinase (middle), and corticosterone (bottom) than the rabbits located at the top floor. The pH 24 and WHC values of the SJ and LJ rabbits did not differ significantly. Journey length had a significant effect (p < or = 0.01) on meat tenderness. The meat from rabbits subjected to LJ had higher values of maximum stress and total toughness than did the SJ rabbits (p < or = 0.05). There were similar differences (p < or = 0.05) between LJ and SJ rabbits in their stress values of compression at 20% and 40% (measures of the tenderness of raw meat). In hot weather, the position on the transport truck appeared to have a greater effect on rabbit welfare than the duration of the journey. 相似文献
999.
Chakeredza S Edrada RA Ebel R ter Meulen U 《Journal of animal physiology and animal nutrition》2006,90(3-4):165-172
An experiment was conducted to evaluate the metabolic products of chlorocholine chloride (CCC) in eggs and meat of laying hens fed a diet containing (15)N-CCC. Ten brown laying hens were randomly divided into two groups of five each. One group was offered (15)N-CCC free diet while the other group received a diet with 100 ppm (15)N-CCC for 11 days. Samples of eggs and meat from the laying hens were collected. Egg yolks and albumen were separated. Meat was collected from the breast and femur. The metabolic products of CCC were measured using ion trap electrospray ionisation mass spectrometry (ion trap-ESI-MS/MS). Determination of CCC or its metabolites in eggs and meat showed that CCC was metabolised to choline. Corresponding MS/MS spectra were obtained for m/z 104 (choline) or 105 ((15)N-choline), whereas nothing was detected at m/z 122 (CCC) or 123 ((15)N-CCC). The results from this study indicate that CCC will be metabolised in tissues of laying hens. 相似文献
1000.
Duscher G Pleydell D Prosl H Joachim A 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2006,53(3):138-144
The prevalence rates of Echinococcus multilocularis in foxes (n=5600) evaluated in several Austrian surveys conducted between 1991 and 2004 were analysed for spatial and temporal differences. Data from early studies (1993-1997) in which the intestinal scraping technique (IST) was utilized were compared with data from recent (1999-2004) investigations, which made use of the shaking in a vessel technique (SVT), and it was assessed whether or not the infection rates of Austrian foxes had increased between the investigated intervals. In total, data from 85 districts are presented and both the retrospective and recent data are available from 39 of these districts. A Bayesian hierarchical model of parasite prevalences is presented which (i) accounts for differences in the sensitivity of IST and SVT, (ii) incorporates spatial auto-correlation between neighbouring districts, (iii) investigates the possibility of a temporal shift in the infection status of foxes, and (iv) quantifies uncertainty at each level of the model. The national average prevalence rates in the mid-1990s and at the turn of the millennium were 2.4% (95% confidence intervals 1.1-4.8) and 3.9% (95% confidence intervals 1.5-8.4) respectively. Above average prevalence rates were observed in the western and the northern parts of the country. Evidence is also presented for a temporal augmentation of the prevalence rates in some districts in the northern and eastern parts of the country. These findings are in concordance with several investigations in other European states where both newly emerged areas and elevated levels of transmission in existing endemic areas have been found. None of the districts investigated here showed significant evidence of a drop in prevalence. 相似文献