全文获取类型
收费全文 | 17695篇 |
免费 | 946篇 |
国内免费 | 17篇 |
专业分类
林业 | 855篇 |
农学 | 573篇 |
基础科学 | 131篇 |
2585篇 | |
综合类 | 2750篇 |
农作物 | 965篇 |
水产渔业 | 1019篇 |
畜牧兽医 | 8586篇 |
园艺 | 209篇 |
植物保护 | 985篇 |
出版年
2021年 | 162篇 |
2020年 | 172篇 |
2019年 | 205篇 |
2018年 | 326篇 |
2017年 | 382篇 |
2016年 | 284篇 |
2015年 | 217篇 |
2014年 | 326篇 |
2013年 | 711篇 |
2012年 | 546篇 |
2011年 | 675篇 |
2010年 | 458篇 |
2009年 | 447篇 |
2008年 | 675篇 |
2007年 | 594篇 |
2006年 | 552篇 |
2005年 | 480篇 |
2004年 | 451篇 |
2003年 | 453篇 |
2002年 | 389篇 |
2001年 | 495篇 |
2000年 | 484篇 |
1999年 | 381篇 |
1998年 | 186篇 |
1997年 | 209篇 |
1995年 | 195篇 |
1994年 | 159篇 |
1993年 | 173篇 |
1992年 | 288篇 |
1991年 | 322篇 |
1990年 | 310篇 |
1989年 | 314篇 |
1988年 | 291篇 |
1987年 | 252篇 |
1986年 | 296篇 |
1985年 | 256篇 |
1984年 | 211篇 |
1983年 | 208篇 |
1979年 | 253篇 |
1978年 | 166篇 |
1975年 | 171篇 |
1974年 | 235篇 |
1973年 | 215篇 |
1972年 | 253篇 |
1971年 | 230篇 |
1970年 | 204篇 |
1969年 | 194篇 |
1968年 | 158篇 |
1967年 | 160篇 |
1966年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
J. Plendl M. Bahramsoltani O. Gemeinhardt H. Hünigen S. Käßmeyer P. Janczyk 《Anatomia, histologia, embryologia》2009,38(5):355-360
Teaching morphology, a fundamental part of medicine curricula is traditionally based on lectures and practical trainings. We introduced peer-assisted learning (PAL) and student expert teams to the courses to give the students the possibility to improve their free speech and self-confidence. We involved students in active preparation of online materials such as labelled e-slides and e-pics . We offered online digital microscopy (ZoomifyTM ) and dissection (CyberPrep) allowing repeating the learned material and studying veterinary morphology outside the dissection theatre. Over 60% of first and third semester students profited from being a peer or being taught by a peer and 50% said the expert teams were an excellent method to learn the topographic anatomy. Almost all students applied ZoomifyTM and CyberPrep and 75% of them found the digital microscopy and dissection to be a helpful or very helpful learning tool. In face of reduced contact hours, these forms of education compensated in part the lost teaching time. We observed improvement of rhetoric and presentation skills and self-confidence. The approaches should therefore find their constant place in the veterinary medicine curricula. 相似文献
72.
Carcass measurements for weight, longissimus muscle area, 12-13th-rib fat thickness, and marbling score, as well as for live animal measurements of weight at the time of ultrasound, ultrasound longissimus muscle area, ultrasound 12-13th-rib fat thickness, and ultrasound-predicted percentage ether extract were taken on 2,855 Angus steers. The average ages for steers at the time of ultrasound and at slaughter were 391 and 443 d, respectively. Genetic and environmental parameters were estimated for all eight traits in a multivariate animal model. In addition to a random animal effect, the model included a fixed effect for contemporary group and a covariate for measurement age. Heritabilities for carcass weight, carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound weight, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.48, 0.45, 0.35, 0.42, 0.55, 0.29, 0.39, and 0.51, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, carcass marbling score and ultrasound-predicted percentage ether extract, and carcass and ultrasound weight were 0.69, 0.82, 0.90, and 0.96, respectively. Additional estimates were derived from a six-trait multivariate animal model, which included all traits except those pertaining to weight. This model included a random animal effect, a fixed effect for contemporary group, as well as covariates for both measurement age and weight. Heritabilities for carcass longissimus muscle area, carcass fat thickness, carcass marbling score, ultrasound longissimus muscle area, ultrasound fat thickness, and ultrasound-predicted percentage ether extract were 0.36, 0.39, 0.40, 0.17, 0.38, and 0.49, respectively. Genetic correlations between carcass and ultrasound longissimus muscle area, carcass and ultrasound fat thickness, and carcass marbling and ultrasound-predicted percentage ether extract were 0.58, 0.86, and 0.94, respectively. The high, positive genetic correlations between carcass and the corresponding real-time ultrasound traits indicate that real-time ultrasound imaging is an alternative to carcass data collection in carcass progeny testing programs. 相似文献
73.
74.
Zaks KL Tan EO Thrall MA 《Journal of the American Veterinary Medical Association》2005,226(9):1516-8, 1500
A 5-year-old pit bull-type dog was examined because of lethargy and black feces, and a presumptive diagnosis of methemoglobinemia was made on the basis of grossly visible brown discoloration of the mucous membranes and urine. Heinz body formation was seen on examination of blood smears, and severe anemia developed 3 days later. The dog did not have any history of exposure to toxins or drugs that have been associated with Heinz body formation. The only remarkable historical finding was that the dog had been wandering loose the day prior to initial examination and returned home smelling strongly of skunk spray. Skunk spray contains thiols and other compounds that are strong oxidizing agents. It was speculated that the methemoglobinemia and Heinz body anemia were a result of exposure to these compounds. Skunk interactions with dogs usually have malodorous but otherwise harmless results. However, findings in this dog suggest that more serious consequences may develop in isolated cases. 相似文献
75.
K. O. Ali U. T. Brenøe 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(4):246-252
Three genotypes of chickens including one commercial broiler (CB) and two others from the Norwegian gene bank [Barred Plymouth Rock (BPR) and Jærhøn (JH)] were raised from 1 day to 20 weeks of age with a free choice of a commercial starter ration and whole-grain wheat. Body weights and pen-feed intakes were recorded every 2 weeks. The weight–age data were fitted to a Gompertz growth equation where, among other parameters, adult body weights were estimated and used for size scaling. The heavier CB chickens consumed more food (starter and wheat) than the other two genotypes. The maximum proportions of whole-grain wheat in the diet were 0.56, 0.68 and 0.75 for BPR, CB and JH birds, respectively. Although the proportions of whole-grain wheat were similar between the genotypes as age progressed, their maintenance requirement and feed intakes relative to body weight suggested a major genetic role and a possible interplay of both genetic potential and body size. 相似文献
76.
Mariette van den BergSimone O. Hoskin PhD Chris W. Rogers Alex Grinberg PhD 《Journal of Equine Veterinary Science》2013
Abrupt dietary transitions and feeding of rapidly fermentable diets are common practices in the horse industry and have been associated with digestive and metabolic disorders that can impair the performance of horses. The present study investigated the effect of dietary transition from pasture grazing to confinement with concentrate feeding, and back, on fecal pH and bacterial populations of Streptococcus spp and Lactobacillus spp. Six Thoroughbred fillies, previously grazing perennial ryegrass and white clover-based pasture, were housed in individual stalls and fed an increasing ratio of concentrate to conserved forages for 13 days (days 1-13), followed by an abrupt transition back to only pasture-grazing for 3 days (days 14-16). The concentrate was initially offered at 0.83 kg dry matter (DM)/d and increased to 5 kg DM/d, whereas ensiled alfalfa was initially offered at 0.61 kg DM/d, increasing to 1.22 kg DM/d. Meadow hay was initially offered at 6.73 kg DM/d, decreasing to 1.6 kg DM/d. Fecal specimens were collected daily for determination of pH, and every 2 days for quantitative analysis of Streptococcus spp and Lactobacillus spp. Mean fecal pH increased significantly from pasture baseline values (pH 6.18) during the initial confinement and supplementation on day 1 (6.37), day 2 (6.52), day 3 (6.58), and day 4 (6.43) (standard error of mean [SEM]: 0.056; P < .001). By day 5, mean fecal pH values had decreased to, and remained at, baseline values until the horses returned to pasture, when another increase occurred at day 15 (6.45). Fecal colony forming units (cfu) of Streptococcus spp and Lactobacillus spp increased linearly (r = 0.94; P < .001) from 6.0 and 6.1 log10 cfu/g on day -4, to 7.8 log10 cfu/g on day 14 (SEM: 0.2 P < .001), respectively. Fecal cfu decreased on return to a pasture-only diet (P < .001). In this study, the increment of bacterial populations was associated with a relatively stable fecal pH and highlights the difficulty in identifying the effects of dietary transition on the equine hindgut health, without microbial culture. 相似文献
77.
78.
P A Bobade O O Oduye H O Aghomo 《Revue d'élevage et de médecine vétérinaire des pays tropicaux》1989,42(2):211-217
A survey of 287 dogs for antibodies against Babesia canis in dogs in an endemic area, using ELISA, produced a prevalence of 43 per cent. Antibodies occurred in dogs of all age groups, the prevalence being significantly lower in dogs aged 1 to 6 months than in older dogs. There were no differences between indigenous Nigerian dogs and exotic (foreign) dogs; and between the sexes in the prevalence of antibodies. Antibodies were more prevalent in dogs with B. canis parasitaemia and in those with a higher risk of infection. Also antibodies were detected in some puppies born to seropositive bitches. The ELISA test failed to detect antibodies in 36.1 per cent of dogs with B. canis parasitaemia. 相似文献
79.
M Tokuriki O Aoki Y Niki Y Kurakawa M Hataya T Kita 《American journal of veterinary research》1989,50(6):950-957
Electromyographic (EMG) activity of 4 muscles of the cubital joint and the strain of forelimb hooves were recorded telemetrically in 4 Thoroughbreds (with and without a rider) standing, walking, trotting, and cantering. Bipolar fine wire electrodes were inserted into the muscles, and strain gauges were attached to the hoof wall. Motion pictures (16 mm), synchronized with EMG tracings, were taken to obtain kinematic data. When horses were standing, the biceps brachii had tonic activity, but the brachialis and the caput longum and the caput laterale of the triceps brachii had no EMG activity. The biceps brachii had EMG activity during the stance phase. The brachialis had EMG activity from the end of the stance phase to the middle of the swing phase. Unlike the biceps brachii, the brachialis acted as a flexor muscle of the cubital joint during locomotion. The EMG activity of the caput longum of the triceps brachii was detected from midswing phase to early stance phase. The EMG activity of the caput laterale of the triceps brachii began in midswing or late-swing phase and ceased in early stance or midstance phase. During locomotion, caput longum EMG activity always preceded caput laterale activity. When horses were cantering, the brachialis and the caput longum (acting mainly in the swing phase) had an EMG activity phase different from those in leading and trailing forelimbs. These 4 muscles had similar EMG activity patterns during locomotion in horses with and without a rider. 相似文献
80.
Añor S Lipsitz D Williams DC Tripp L Willits N Maselli R LeCouteur RA 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(4):545-550
Single-fiber electromyography (SFEMG), a technique used to investigate neuromuscular transmission, has been described previously in the pelvic limb of dogs. Because preferential involvement of isolated muscle groups can occur in disorders of neuromuscular transmission, SFEMG was done in the peroneus longus (PL), extensor carpi radialis (ECR), and orbicularis oculi (OO) muscles of 10 adult, clinically normal dogs. Jitter was calculated as the mean absolute value of the consecutive differences in latency of 50 single muscle fiber action potentials after stimulation of intramuscular nerve bundles at the level of the motor point in at least 20 muscle fibers per muscle. Bilateral recordings were performed in 3 dogs. Mean jitter values were determined for each muscle, and differences among muscle groups and among dogs were compared. The upper limits of mean consecutive difference (mean plus 3 standard deviations) for the PL, ECR, and OO muscles were 21.94, 22.53, and 23.39 micros, respectively, and the upper limit of mean consecutive difference for individual muscle fibers in the respective fiber pools was 28.62, 36.39, and 35.68 micros. Jitter values for the ECR and OO were significantly higher than the jitter value for the PL muscle (P < .05). Significant differences among muscles or dogs or between sides were not observed for the ECR. Significant differences among dogs were observed for OO jitter values and were attributed to extremely low jitter values in 1 dog. Significant differences were demonstrated between sides for the PL and were attributed to small sample size. Results of this study provide normative data that can be used in the application of the stimulated SFEMG technique to dogs with suspected disorders of neuromuscular transmission. 相似文献