全文获取类型
收费全文 | 4573篇 |
免费 | 287篇 |
国内免费 | 12篇 |
专业分类
林业 | 214篇 |
农学 | 236篇 |
基础科学 | 48篇 |
731篇 | |
综合类 | 345篇 |
农作物 | 188篇 |
水产渔业 | 196篇 |
畜牧兽医 | 2368篇 |
园艺 | 111篇 |
植物保护 | 435篇 |
出版年
2021年 | 40篇 |
2020年 | 85篇 |
2019年 | 63篇 |
2018年 | 94篇 |
2017年 | 104篇 |
2016年 | 85篇 |
2015年 | 62篇 |
2014年 | 98篇 |
2013年 | 211篇 |
2012年 | 170篇 |
2011年 | 228篇 |
2010年 | 185篇 |
2009年 | 174篇 |
2008年 | 209篇 |
2007年 | 179篇 |
2006年 | 177篇 |
2005年 | 165篇 |
2004年 | 151篇 |
2003年 | 146篇 |
2002年 | 165篇 |
2001年 | 131篇 |
2000年 | 117篇 |
1999年 | 108篇 |
1998年 | 67篇 |
1997年 | 44篇 |
1996年 | 51篇 |
1995年 | 45篇 |
1994年 | 48篇 |
1993年 | 57篇 |
1992年 | 87篇 |
1991年 | 75篇 |
1990年 | 81篇 |
1989年 | 75篇 |
1988年 | 44篇 |
1987年 | 58篇 |
1986年 | 47篇 |
1985年 | 56篇 |
1984年 | 61篇 |
1983年 | 51篇 |
1982年 | 53篇 |
1980年 | 33篇 |
1979年 | 39篇 |
1978年 | 45篇 |
1977年 | 44篇 |
1976年 | 43篇 |
1975年 | 34篇 |
1974年 | 41篇 |
1972年 | 34篇 |
1971年 | 34篇 |
1969年 | 42篇 |
排序方式: 共有4872条查询结果,搜索用时 296 毫秒
221.
K Forster CS Galina M Maquivar G Van der Laan R Arnoni A Verduzco 《Reproduction in domestic animals》2007,42(6):566-570
Thirty cyclic, non-suckled Brahman cows were divided into three groups, all of which were synchronized sequentially with CIDR-B and observed continuously for 100 h to determine different behavioural oestrus signs. Twenty-four hours after implant withdrawal, all synchronized cows in the group, together with all other cows displaying oestrus, were subjected to intensive ultrasonographic observations (every 6 h for 120 h) to pinpoint the moment of ovulation. In the first group, oestrus and ovulation response was 60% (6/10), in the second 44% (4/9) showed oestrus and six ovulated, and in the third group oestrus and ovulation were 80% (8/10). Significant differences were observed between the second and third groups (p < 0.05). No differences were observed in the duration of oestrus, time when oestrus was displayed after implant withdrawal, time of ovulation and onset of oestrus, end of oestrus to ovulation, and intensity of oestrus on a point scale. The relationship between duration of oestrus and time of ovulation was r(2) = 0.16. Ovulation, on average, was 32.1 +/- 14.5 h after the onset of oestrus, 22.3 +/- 16.5 h after the end of oestrus, and 91.8 +/- 16.7 after implant withdrawal, although no significant differences were observed. One non-synchronized animal showed oestrous activity in the second group but failed to ovulate. In the third group, 8 animals showed oestrus, 4 with high concentrations of progesterone. Of the other four one ovulated. In conclusion, oestrous behaviour is not necessarily the best marker to predict the time when ovulation takes place due to variation in the length of the oestrous period and the possible integration of non-ovulatory animals into sexually active groups. 相似文献
222.
223.
G Hoflack G Opsomer T Rijsselaere A Van Soom D Maes A de Kruif L Duchateau 《Reproduction in domestic animals》2007,42(2):153-161
Subjective microscopic sperm motility results have recently been demonstrated to differ between Holstein-Friesian (HF) and Belgian Blue (BB) bulls. However, such assessments are rather imprecise. In the present study, sperm motility was assessed objectively by means of the Hamilton Thorne CEROS version 12.2c computer-assisted sperm motility analyser (CASA), and differences between the BB and HF breed could also be demonstrated. Higher percentages of both totally (p < 0.0001) and progressively (p < 0.0001) motile spermatozoa were encountered in the HF breed compared with the BB breed. Furthermore, a lower kinetic efficiency of the BB spermatozoa, evidenced by a lower beat cross-frequency (p = 0.0007) combined with a higher lateral head displacement (p = 0.0015), was the basis for the lower velocity of BB sperm cells. Additionally, BB spermatozoa move less straight forward, resulting in a lower straightness (p < 0.0001). No sperm motility differences were observed between age groups within the BB breed. The breed differences were observed in the examined bull populations residing at AI centres, in Belgium for the BB bulls and in the Netherlands for the HF bulls. However, these bull populations are selected for fertility. A similar pattern was observed in an unselected bull population of both breeds, although these differences were mostly non-significant for the different CASA parameters. Nevertheless, these data suggest that a genetic component might be responsible for the observed sperm motility breed differences. 相似文献
224.
(接《新饲料》第10期第14页)2针对食品安全进行饲料的营养调控2.1霉菌毒素的控制霉菌毒素是最重要的饲料污染物之一,并且会给动物以及公众健康带来严重影响。霉菌毒素有多种危 相似文献
225.
226.
227.
Jrme Van Biervliet DVM Dipl ACVIM Marc Kraus DVM Dipl ACVIM Brett Woodie DVM Dipl ACVS Thomas J. Divers DVM Dipl ACVIM Dipl ACVECC Anna Gelzer Dr. Med. Vet. Dipl ACVIM Dorothy Ainsworth DVM PhD Dipl ACVIM 《Journal of Veterinary Cardiology》2006,8(1):69-73
A 5-year-old Holstein cow, pregnant with a valuable calf, was presented with signs of heart failure (tachycardia, peripheral edema, and distended jugular veins) related to pericardial lymphoma and associated cardiac tamponade. In addition, pleural effusion was present in both hemithoraces. Medical treatment, which consisted of repeated pericardiocenteses, placement of indwelling pleural catheters, administration of intravenous fluid therapy, antibiotics and anti-inflammatory drugs, was ineffective in controlling recurrence of clinical signs despite a temporary improvement. A standing thoracoscopic pericardiotomy was performed in an attempt to reduce clinical signs of heart failure and to prolong life. Clinical signs of heart failure abated and no recurrence was seen. Standing thoracoscopic pericardiotomy along with possible corticosteroids can be recommended as palliative treatment in an effort to extend life for reproductive performance in genetically valuable animals. 相似文献
228.
Frdric Billen DVM Nicole Van Israël DVM CertVC MSc Dipl ECVIM 《Journal of Veterinary Cardiology》2006,8(1):63-68
This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes. 相似文献
229.
230.
A. Andreu C. Tonón M. Van Damme M. Huarte G. Daleo 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(8):777-783
It has been proposed that susceptibility of potato to Phytophthora infestans would be a consequence of suppression and /or delaying of defense reactions by a soluble glucan which is released by compatible races of the fungus. In this report, the reaction of potato tuber slices (Solanum tuberosum cv. Huinkul) infected with either race I (1,4,7,8,10,11) or C (1,4,10,11) of Phytophthora infestans was studied. Race C grew better on slices than race I. Glucans from both races were isolated and their effect on the accumulation of phytoalexins and glucanases in tuber slices was studied. The glucans from the less virulent race (I) did not affect the accumulation of phytoalexins and glucanases in tuber slices infected or elicited with eicosapentaenoic acid, whereas the glucans from race C produced 70% inhibition of phytoalexin accumulation and reduced by 50% the induction of glucanase activities. Purified glucanases from potato degraded the glucans from race C but not from race I. The results reported here show that, at least on this cultivar, glucans from both races affected defense responses in a different manner, which could reflect structural differences between these glucans. 相似文献