全文获取类型
收费全文 | 71091篇 |
免费 | 4067篇 |
国内免费 | 34篇 |
专业分类
林业 | 3253篇 |
农学 | 2532篇 |
基础科学 | 479篇 |
8754篇 | |
综合类 | 11414篇 |
农作物 | 2618篇 |
水产渔业 | 3699篇 |
畜牧兽医 | 36676篇 |
园艺 | 942篇 |
植物保护 | 4825篇 |
出版年
2018年 | 1095篇 |
2017年 | 1149篇 |
2016年 | 1080篇 |
2015年 | 922篇 |
2014年 | 1154篇 |
2013年 | 2665篇 |
2012年 | 2084篇 |
2011年 | 2481篇 |
2010年 | 1707篇 |
2009年 | 1765篇 |
2008年 | 2604篇 |
2007年 | 2375篇 |
2006年 | 2335篇 |
2005年 | 2132篇 |
2004年 | 2195篇 |
2003年 | 2165篇 |
2002年 | 2039篇 |
2001年 | 2368篇 |
2000年 | 2377篇 |
1999年 | 1926篇 |
1998年 | 913篇 |
1997年 | 821篇 |
1996年 | 782篇 |
1995年 | 861篇 |
1994年 | 843篇 |
1993年 | 767篇 |
1992年 | 1523篇 |
1991年 | 1542篇 |
1990年 | 1662篇 |
1989年 | 1507篇 |
1988年 | 1450篇 |
1987年 | 1340篇 |
1986年 | 1384篇 |
1985年 | 1336篇 |
1984年 | 1128篇 |
1983年 | 1025篇 |
1982年 | 628篇 |
1979年 | 1004篇 |
1978年 | 795篇 |
1977年 | 717篇 |
1976年 | 676篇 |
1975年 | 719篇 |
1974年 | 766篇 |
1973年 | 830篇 |
1972年 | 803篇 |
1971年 | 748篇 |
1970年 | 729篇 |
1969年 | 744篇 |
1967年 | 658篇 |
1966年 | 631篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
271.
272.
273.
274.
Thirty eight newly weaned hinds were randomly allocated to one of two equal groups. One group received ivermectin, the other, oxfendazole at dose rates of 0.2 mg/kg and 4.5 mg/kg, respectively. All deer were drenched four times and were grazed on pasture. Both anthelmintics reduced D. viviparus faecal larval counts to low levels 20 days after dosing, but the mean larval output and the proportion of deer shedding D. viviparus larvae at 27 and 33 days after treatment, were significantly lower in the ivermectin treated group. There was no significant difference in weight gain between the two groups throughout the trial. This study suggests that ivermectin prevents reinfection with D. viviparus for approximately 14 days longer than oxfendazole. 相似文献
275.
Stein T Martineau GP Morris R Charette R 《The Canadian veterinary journal. La revue veterinaire canadienne》1987,28(6):355-362
It is proposed that just as the stethoscope and thermometer are fundamental tools for individual medicine, production and health recording systems are fundamental tools for effective population medicine. Treatment and control of clinical diseases as the primary objective is no longer considered appropriate for livestock population. Disease in populations now describes a deviation between what is happening and what is expected to happen. This redefinition of disease implies that it is of multifactorial origin and thus a different problem solving approach must be implemented. Therefore, a swine enterprise must be considered as a system, a set of interdependent components continuously interacting to produce pork. As a system, it is characterized by certain properties: change, environment, counterintuitive behavior, drift to low performance, interdependency, and organization. A redefinition of diseases implies also that they are not only “treated” but managed. Management consists of planning, monitoring, evaluation, and analysis. For this process to be implemented successfully, a goal-directed recording system providing a farm-based infrastructure for problem solving is essential. Clinical problem solving (diagnosis) is thus based on epidemiological and demographic methods. 相似文献
276.
Denicourt M Gradel D Martineau GP 《The Canadian veterinary journal. La revue veterinaire canadienne》1987,28(6):346-354
Environment is of primary importance to animal health and development. Ventilation is a problem in establishing an adequate environment, particularly in swine housing. In order for veterinarians to deal with this problem, a fundamental understanding of the building is necessary. The present article describes a clinical approach to ventilation diagnosis problems in the piggery. 相似文献
277.
278.
McKenna PB 《New Zealand veterinary journal》1987,35(6):94-97
A new approach to the interpretation of faecal egg counts using a simple "formula", is described. It is suggested that adoption of this procedure may enable the likely level and frequency distribution of strongyle worm burdens (Nematodirus excluded) in young sheep flocks to be estimated. The potential relevance of this information to the diagnosis of gastrointestinal parasitism is discussed. 相似文献
279.
Canfield PJ Watson AD Ratcliffe RC 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1987,16(1):21-28
Dyserythropoiesis characterized by enhanced intramedullary destruction, pathologic sideroblasts and siderocytes, and hemoglobin crystallization was detected in a female Cocker Spaniel presented for poor exercise tolerance. Examination of peripheral blood revealed intraerythrocytic crystals, granulation of erythrocytes, nucleated erythroid cells, reticulocytosis and marked variation in erythrocyte morphology in the absence of anemia. Bone marrow examination revealed sideroblasts, a low M:E ratio and evidence of enhanced intramedullary destruction of erythroid cells. Electron microscopy of peripheral blood and bone marrow confirmed pathologic mitochondrial iron accumulation in erythroid cells and the presence of intraerythrocytic hemoglobin crystals. A cause for the hematologic changes was not identified. After the animal became clinically normal, siderocytes disappeared from peripheral blood but intraerythrocytic crystals and reticulocytosis persisted. 相似文献
280.
J. E. M. Scheerboom P. W. M. Van Adrichem M. A. M. Taverne 《Veterinary research communications》1987,11(3):253-269
With electromyography and strain gauges the uterine motility of the sow during the oestrous cycle and early pregnancy was studied. Special attention was paid to characterization of myometrial activity at the time of intrauterine migration of blastocysts.From recordings of 4 animals (3 became pregnant) 3 types of electrical spiking activity (each could be correlated with an elevation of the strain gauge tension) were discerned. Two of them appeared regularly and were suitable for analysis: High Voltage Slow Acticity (with relative high amplitude and low frequency of spikes) and Low Voltage Fast Activity (with relative low aplitude and high frequency of spikes).The sexual status markedly influenced myometrial activity: during prooestrus and oestrus only one type of electrical activity was present whereas the myoelectrical complex (an episode of this activity and the subsequent interval of inactivity) was shorter than 10 min. During dioestrus the myoelectrical complex was longer than 10 min and High Voltage Slow Activity (solely on the cervix and bifurcation) and Low Voltage Fast Activity occurred simultaneously in episodes which mainly appeared to originate on the bifurcation.The characteristics of uterine activity during pregnancy were similar to those of a cyclic sow until day 12. It was only on day 12 that gestation appeared from an increased frequency of myoelectrical complexes.It is concluded that Low Voltage Fast Activity as it was found on the uterine horn at days 8–9 might be involved in the process of intra-uterine migration of blastocysts. In cyclic and in pregnant animals the patterns of Low Voltage Fast Activity were similar. Therefore, the occurrence of Low Voltage Fast Activity is independent of the actual presence of blastocysts. It seems to be exhibited in dependence on the ovarian hormones. 相似文献