全文获取类型
收费全文 | 83504篇 |
免费 | 4677篇 |
国内免费 | 93篇 |
专业分类
林业 | 3257篇 |
农学 | 2057篇 |
基础科学 | 471篇 |
8719篇 | |
综合类 | 15497篇 |
农作物 | 3148篇 |
水产渔业 | 3495篇 |
畜牧兽医 | 46261篇 |
园艺 | 859篇 |
植物保护 | 4510篇 |
出版年
2019年 | 737篇 |
2018年 | 1202篇 |
2017年 | 1322篇 |
2016年 | 1145篇 |
2015年 | 1035篇 |
2014年 | 1403篇 |
2013年 | 2869篇 |
2012年 | 2307篇 |
2011年 | 2812篇 |
2010年 | 1788篇 |
2009年 | 1962篇 |
2008年 | 2764篇 |
2007年 | 2518篇 |
2006年 | 2396篇 |
2005年 | 2251篇 |
2004年 | 2224篇 |
2003年 | 2297篇 |
2002年 | 2090篇 |
2001年 | 2511篇 |
2000年 | 2536篇 |
1999年 | 1963篇 |
1998年 | 867篇 |
1997年 | 855篇 |
1996年 | 838篇 |
1995年 | 944篇 |
1994年 | 788篇 |
1993年 | 846篇 |
1992年 | 1689篇 |
1991年 | 1855篇 |
1990年 | 1780篇 |
1989年 | 1744篇 |
1988年 | 1565篇 |
1987年 | 1651篇 |
1986年 | 1644篇 |
1985年 | 1611篇 |
1984年 | 1261篇 |
1983年 | 1125篇 |
1979年 | 1153篇 |
1978年 | 898篇 |
1977年 | 760篇 |
1975年 | 775篇 |
1974年 | 1027篇 |
1973年 | 1026篇 |
1972年 | 1044篇 |
1971年 | 993篇 |
1970年 | 991篇 |
1969年 | 904篇 |
1968年 | 811篇 |
1967年 | 802篇 |
1966年 | 732篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
992.
The performance was compared of cows sired by Holstein, Jersey or Brown Swiss bulls out of Holstein-Friesian×Gir dams of 1/2 to 3/4 Holstein-Friesian content. The animals were kept in a single herd under the same management. The data were analysed by least-squares techniques under a model that included the fixed effects of breed of sire, Bos taurus fraction of the dam, parity, year and season of calving, and a random cow effect. Based on 480 observations, the milk yields per lactation for the Holstein, Jersey and Brown Swiss sired groups were 2821±163, 2320±61 and 2418±119 kg, respectively. The corresponding means for fat yield per lactation were 96.9±6.6, 86.8±2.5 and 92.8±4.8 kg; for protein yield per lactation were 85.3±5.1, 71.3±1.9 and 76.3±3.7 kg; for lactation length, 339±18, 283±7 and 313±14 days for fat percentage, 3.37±0.10, 3.73±0.04 and 3.77±0.07%; and for protein percentage, 3.02±0.05, 3.10±0.02 and 3.16±0.04%. The respective calving intervals were 487±24, 408±11 and 461±245 days. The yields of milk and protein per day of calving interval were similar in the Jersey and Holstein sired groups, while the former had higher yields of fat, implying that production economics might favour the smaller Jersey crosses in production systems in which the males were not reared. Crossing with Brown Swiss did not improve performance over the Holstein sired crosses. 相似文献
993.
Pregnant St. Croix White and Barbados Blackbelly hair sheep ewes were used to evaluate the effect of supplemental nutrition around the time of lambing on ewe and lamb performance during the dry and wet seasons on St. Croix. Beginning 14 d before expected day of lambing (d 0) and for 21 d postpartum, one group of ewes was fed a pelleted supplement in addition to grazing guinea grass pasture (FEED). Other ewes in the flock grazed pasture only (CONTROL). This study was conducted during the dry season (June through September; FEED n = 14 and CONTROL n = 15) and during the wet season the next year (October through January; FEED n = 11 and CONTROL n = 12). The 24-h milk production of each ewe was measured on d 7, 21, 35, 49, and 63. Ewes were exposed to sterile rams equipped with marking harnesses to detect estrus during the postpartum period. The FEED ewes lost less weight postpartum during both seasons (P < 0.0001) and had higher milk production (P < 0.009) than CONTROL ewes during the dry season. During the dry season, the time to the first postpartum estrus did not differ (P > 0.10) between FEED and CONTROL ewes (46.9 +/- 2.7 vs 52.9 +/- 2.6 d, respectively). During the wet season, the time to first postpartum estrus was less (P < 0.07) in FEED than in CONTROL ewes (33.0 +/- 3.1 vs 41.1 +/- 2.9 d, respectively). The FEED ewes had higher lamb birth weight (P < 0.04) and weaning weight (P < 0.05) than CONTROL ewes (3.2 +/- 0.1 and 12.2 +/- 0.5 vs 2.9 +/- 0.1 and 10.9 +/- 0.5 kg, respectively) during the dry season. In the wet season, lamb birth weight and weaning weight were similar (P > 0.10) between FEED and CONTROL (3.2 +/- 0.1 and 15.5 +/- 0.7 vs 3.1 +/- 0.1 and 15.3 +/- 0.6 kg, respectively). Lambs born during the wet season had higher (P < 0.0001) ADG than lambs born during the dry season (194.4 +/- 5.9 vs 127.7 +/- 4.7 g/d, respectively). Strategic nutritional supplementation of hair sheep ewes may provide a method for increasing the weight of lambs produced during the dry season in the tropics, but it does not seem to be beneficial during the wet season. 相似文献
994.
The purpose of this study was to determine the origin and subsequent spread of feline calicivirus (FCV), feline herpesvirus (FHV), and feline enteric coronavirus (FECV) in cats relinquished to shelters. FCV was isolated from the oral fauces of 11% of healthy cats upon entry, and isolation rates were highest for kittens (33%). FHV shedding was very low (4%) at the time of entry and occurred mainly in juveniles. FECV shedding was also common among newly relinquished cats (33%), especially older kittens and juveniles (90%). The subsequent spread of all three viruses was rapid and efficient in the shelter environment. Fifteen percent of cats were shedding FCV, 52% FHV, and 60% FECV after 1 week. More detailed studies were done with FECV shedding, which could be accurately quantitated. The amounts of FECV shed by infected cats ranged from 10(2)to 10(16)particles/swab of feces. FECV shedding was several logs higher in young kittens with primary infection than adult cats with primary infections. The mean levels of FECV shedding among adults were the same for primary and chronic infections. Although shelters were not the primary source of these viruses for many relinquished cats, factors intrinsic to the shelter environment were critical in amplifying shedding and spread to susceptible individuals. Extrinsic factors were especially important for the spread of FHV and FECV. FHV shedding rates increased from 4% to 50% in 1 week's time. The speed and magnitude of the increase in FHV shedding suggested that there was reactivation of latent infections as well as acquisition of new infections. FECV shedding increased 10 to 1,000,000 fold in 1 week among cats that were already infected at entry, and more than one-half of initially negative cats were shedding FECV a week later. Feline calicivirus infection was the least likely to spread in the shelter. The infection rate only increased from 11 to 15% in 1 week. 相似文献
995.
Jennifer E Stokes S Dru Forrester 《Veterinary Clinics of North America: Small Animal Practice》2004,34(4):909-22, vi
This article provides a source for easy reference, summarizing in one location newly recognized and unusual causes of acute renal failure (ARF) in dogs and cats. Several of the causes discussed in this article have been described previously. New or unusual causes of ARF in dogs and cats include infectious diseases (leptospirosis,borreliosis, and babesiosis), nephrotoxicants (aminoglycosides,vitamin D, and nonsteroidal anti-inflammatory drugs), and plant material (lilies and raisins/grapes). 相似文献
996.
997.
998.
T. J. Younkin E. G. Davis B. Kukanich 《Journal of veterinary pharmacology and therapeutics》2017,40(4):342-347
The primary study objective was to compare the pharmacokinetics of p.o. terbinafine alone to p.o. terbinafine administered with p.o. cimetidine in healthy adult horses. The second objective was to assess the pharmacokinetics of terbinafine when administered per rectum in two different suspensions at 30 mg/kg to adult horses. Six healthy adult horses were included in this crossover study. Plasma terbinafine concentrations were quantified with liquid chromatography and mass spectrometry. The half‐life (geometric mean) was 8.38 and 10.76 h, for p.o. alone and p.o. with cimetidine, respectively. The mean maximum plasma concentrations were 0.291 μg/mL at 1.54 h and 0.418 μg/mL at 1.28 h for p.o. alone and p.o. with cimetidine, respectively. Terbinafine with cimetidine had an average CMAX 44% higher and the relative F was 153% compared p.o. terbinafine alone, but was not statistically different (P > 0.05). Terbinafine was infrequently detected when administered per rectum in two different suspensions (water or olive oil). Minor adverse effects included oral irritation, fever, and colic. All resolved spontaneously. More pharmacokinetic studies are indicated assessing drug–drug interactions and using multiple dosing intervals to improve our knowledge of effective oral dosing, the potential for drug accumulation, and systemic adverse effect of terbinafine in horses. 相似文献
999.
E. Treggiari L. Ressel G. A. Polton J. Benoit I. Desmas L. Blackwood 《Veterinary and comparative oncology》2017,15(1):i-i
The cover image, by E. Treggiari et al., is based on the Original Article Clinical outcome, PDGFRß and KIT expression in feline histiocytic disorders: a multicentre study, DOI: 10.1111/vco.12142 .
1000.
Outcome and complications in dogs with appendicular primary bone tumors treated with stereotactic radiotherapy and concurrent surgical stabilization 下载免费PDF全文