全文获取类型
收费全文 | 555篇 |
免费 | 37篇 |
专业分类
林业 | 34篇 |
农学 | 21篇 |
基础科学 | 4篇 |
132篇 | |
综合类 | 40篇 |
农作物 | 37篇 |
水产渔业 | 35篇 |
畜牧兽医 | 233篇 |
园艺 | 12篇 |
植物保护 | 44篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 24篇 |
2016年 | 20篇 |
2015年 | 29篇 |
2014年 | 20篇 |
2013年 | 41篇 |
2012年 | 36篇 |
2011年 | 54篇 |
2010年 | 31篇 |
2009年 | 20篇 |
2008年 | 42篇 |
2007年 | 33篇 |
2006年 | 21篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1973年 | 5篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有592条查询结果,搜索用时 15 毫秒
91.
German AJ Holden S Bissot T Morris PJ Biourge V 《Journal of Feline Medicine and Surgery》2008,10(5):452-459
Obesity is one of the most common medical diseases in cats, but there remains little information on success of weight loss regimes in obese client-owned cats. No information currently exists on body composition changes during weight loss in clinical cases. Twelve obese client-owned cats undertook a weight loss programme incorporating a high-protein low fat diet. Body composition was quantified by dual-energy X-ray absorptiometry, before and after weight loss. Mean (+/-standard deviation) weight loss was 27+/-6.8% of starting weight, and mean rate of weight loss was 0.8+/-0.32% per week. Mean energy allocation during weight loss was 32+/-7.0 kcal/kg target weight. Mean composition of tissue lost was 86:13:1 (fat:lean:bone mineral). The proportion of lean tissue loss was positively associated with overall percentage of weight loss (simple linear regression, r(2)=44.2%, P=0.026). Conventional weight loss programmes produce safe weight loss, but lean tissue loss is an inevitable consequence in cats that lose significant proportions of their starting body weight. 相似文献
92.
Valéria Café Mar?al Anna Oevermann Tim Bley Patrizia Pfister Julien Miclard 《Journal of veterinary science (Suw?n-si, Korea)》2008,9(1):113-115
A 4-month-old female Holstein Friesian calf was referred to the Veterinary Teaching Hospital, University of Berne, Switzerland for evaluation of ataxia, weakness, apathy and stunted growth. Clinical examination revealed generalized ataxia, propioceptive deficits, decreased menace response and sensibility. Postmortem examination did not reveal macroscopic changes of major organs. Histologically, the brain and the spinal cord lesions were characterized by polymicrocavitation, preferentially affecting the white matter fibers at the junction of grey and white matter and by the presence of Alzheimer type II cells. The liver revealed lesions consistent with a congenital portosystemic shunt, characterized by increased numbers of arteriolar profiles and hypoplasia to absence of portal veins. The pathological investigations along with the animal history and clinical signs indicated a hepatic encephalomyelopathy due to a congenital portosystemic shunt. 相似文献
93.
Fractals and search paths in mammals 总被引:6,自引:0,他引:6
The fractal index by Katz and George (1985) for thecharacterization of planar curves is applied to wolf search pathsrecorded by radio-telemetry. All the sets of paths studied showspatial patterns whose complexity is between a straight line anda true random walk. Females fractal dimensions show significantchanges throughout the year, depending on the state of their lifecycle (normal, breeding and wandering). There are alsodifferences between males and females, but not between adults andnon-adults. The results are discussed with regard to wolffood-search strategies. 相似文献
94.
Bech-Sàbat G López-Gatius F Santolaria P García-Ispierto I Pabón M Nogareda C Yániz JL Almería S 《Veterinary parasitology》2007,145(1-2):164-167
Progesterone has been reported to reduce Th1 responses during pregnancy. Thus, given that an excessive Th1 response could lead to abortion in Neospora-infected dairy cows, we hypothesized a reduction in abortion risk following progesterone supplementation during the mid-gestation period in these animals. Seropositive animals were assigned on day 120 of gestation to a Control (n=33) or Treatment (n=34) group. Treatment consisted of progesterone supplementation by fitting a progesterone releasing intravaginal device containing 1.55g of progesterone for 28 days. Mean Neospora caninum antibody titres tested by ELISA on days 40, 90 and 120 of gestation were used to classify the cows as showing high (> or =30 units) or low (<30 units) titration. Abortion rate showed a significant increase (P<0.01) in the Treatment group (35%) compared to the Control (9%). Using logistic regression procedures, there was a significant (P<0.0001) interaction between progesterone treatment and antibody titration. Progesterone-treated cows with a high antibody titre showed a likelihood of abortion 14.3 times higher than those not treated, while in cows with low antibody titres, exogenous progesterone had not effect. Our results do not support our starting hypothesis and suggest that progesterone supplementation in cows with high N. caninum antibody titres increases the risk of abortion possibly by affecting cell-mediated immune responses. 相似文献
95.
Nogareda C López-Gatius F Santolaria P García-Ispierto I Bech-Sàbat G Pabón M Mezo M Gonzalez-Warleta M Castro-Hermida JA Yániz J Almeria S 《Veterinary parasitology》2007,148(3-4):193-199
The dynamics of antibody production against Neospora caninum during the gestation period was examined in chronically infected dairy cows. Data were obtained from 86 pregnant parous dairy cows, 21 of which had suffered abortion. The cows belonged to two herds in which a diagnosis of N. caninum infection had been previously confirmed in aborted foetuses. Pregnancy diagnosis and blood collection were performed on post-insemination Days 40, 90, 120, 150, 180, 210, and at parturition or until the time of abortion detection. Blood plasma was tested for antibodies against N. caninum using ELISA. The non-aborting cows were divided into two groups according to whether their antibody values in the second half of gestation had increased or not, while aborting cows were classified as those showing an antibody peak before abortion or those not showing a pre-abortion peak. Differences in antibody values throughout pregnancy in each group of non-aborting and aborting cows were analysed by GLM repeated measures of analysis of variance. While 32 non-aborting cows (49%) showed a significant and consistent increase in anti-Neospora antibody values during the second half of gestation, antibody values in the remaining 33 non-aborting cows were practically constant throughout gestation. An antibody peak around abortion was observed in 11 aborting cows (52%), while antibody values in the remaining 10 aborting cows were similar before and at abortion. Seroprevalence fluctuations, defined as seronegative blood samples at some point during the gestation period, were, furthermore, observed in 2 aborting and 11 non-aborting cows. Our results indicate two clearly distinguishable types of humoral immune dynamics throughout gestation: an increased or flat production of antibodies during the second half of gestation in non-aborting animals and before abortion in aborting cows. The observation that some Neospora-infected dams can exhibit negative antibody values at any time during gestation, particularly at parturition or abortion, prompts future studies designed to explore the use of new ELISA strategies at the farm level. 相似文献
96.
It was nearly 100 years ago that the decline in quality and yield observed in potato crops was attributed to the accumulation of pathogens in seed tubers saved from one field generation to the next. As a direct result of this realization, seed potato certification programs have been initiated throughout the world. While these programs have different administrative structures and employ various methodologies, they are all dedicated to the primary goal of producing a sufficient volume of high quality seed tubers as free from disease causing organisms as possible. Viral diseases are especially problematic because they have serious economic affects and their physical and biological properties make them difficult to control. Until recently, certification programs have relied on methodologies including the use of virus-free material obtained from tissue culture, strict adherence to practices that minimize the mechanical and insect spread of virus, physical inspection of seed increase plots to identify and minimize the number of virus-infected plants, and the increase of seed materials for only a limited number of years to insure that any infected materials are “flushed out” of the system. Approximately 10 years ago, it was first observed that virus resistance can be obtained by using transformation techniques to insert viral genes into the genome of plants. Subsequently, researchers in private and public laboratories have shown that potato plants produced in this way are highly resistant or immune to several viral diseases. The effect that the deployment of these materials may have on the seed potato certification process is the subject of this paper. 相似文献
97.
Although many age-related changes have been described in the nervous system of different species, few authors have specifically studied the topic. Knowledge of such changes is essential to veterinary pathologists, who must distinguish the lesions of specific pathologic processes from those arising as a result of normal aging. The brains of 20 old dogs, ranging in age from 8 to 18 years, were compared with those of 10 young dogs using routine staining techniques (hematoxilin and eosin, periodic acid-Schiff), special staining techniques (periodic acid-methenamine silver stain), and immunohistochemical techniques to detect glial fibrillary acid protein, neurofilaments, ubiquitin, and beta-amyloid. Changes affected meninges and choroid plexuses, meningeal and parenchymal vessels, neurons, and glial cells. Of special interest was the presence of polyglucosan bodies, cerebrovascular amyloid deposition, senile plaques, and ubiquitinated bodies. Some of the age-related changes found, particularly lipofuscin, polyglucosan bodies, and beta-amyloid protein deposition, may play a role in the pathogenesis of the canine cognitive dysfunction syndrome. The dog could be used as a natural animal model for the study of normal aging and human neurodegenerative diseases. 相似文献
98.
99.
Exploring connectivity between spawning and nursery areas of Mullus barbatus (L., 1758) in the Mediterranean through a dispersal model 下载免费PDF全文
Connectivity between spawning and nursery areas plays a major role in determining the spatial structure of fish populations and the boundaries of stock units. Here, the potential effects of surface current on a red mullet population in the Central Mediterranean were simulated using a physical oceanographic model. Red mullet larvae were represented as Lagrangian drifters released in known spawning areas of the Strait of Sicily (SoS), which represents one of the most productive demersal fishing‐grounds of the Mediterranean. To consider the effect of inter‐annual variability of oceanographic patterns, numerical simulations were performed for the spawning seasons from 1999 to 2012. The main goal was to explore connectivity between population subunits, in terms of spawning and nursery areas, inhabiting the northern (Sicilian‐Maltese) and southern (African) continental shelves of the SoS. The numerical simulations revealed a certain degree of connectivity between the Sicilian–Maltese and the African sides of the SoS. Connectivity is present in both directions, but it is stronger from the Sicilian–Maltese spawning areas to the African nurseries owing to the marine circulation features of the region. However, because the majority of the larvae are transported to areas unsuitable for settlement or outside the SoS, the dispersal process is characterized by a strong loss of potential settlers born in the spawning areas. These results are in agreement with the low genetic heterogeneity reported for this species in the Mediterranean Sea and support the existence of a metapopulation structure of red mullet in the SoS and the adjacent areas. 相似文献