全文获取类型
收费全文 | 580篇 |
免费 | 38篇 |
专业分类
林业 | 20篇 |
农学 | 14篇 |
基础科学 | 9篇 |
114篇 | |
综合类 | 73篇 |
农作物 | 46篇 |
水产渔业 | 37篇 |
畜牧兽医 | 226篇 |
园艺 | 23篇 |
植物保护 | 56篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 30篇 |
2012年 | 31篇 |
2011年 | 35篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 34篇 |
2007年 | 30篇 |
2006年 | 34篇 |
2005年 | 32篇 |
2004年 | 30篇 |
2003年 | 36篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1995年 | 3篇 |
1992年 | 7篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 10篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1952年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有618条查询结果,搜索用时 0 毫秒
611.
Awad H Antunes S Galindo RC do Rosário VE de la Fuente J Domingos A El Hussein AM 《Veterinary parasitology》2011,181(2-4):146-152
Disease prevalence studies are one of the most valuable tools to demonstrate the risk or impact of certain infections in local and global economies. The data obtained in these studies contribute to develop strategies for disease control. The present study aims to provide information about the prevalence of babesiosis and anaplasmosis in the northern regions of Sudan. Blood samples from four different states of Sudan were collected from apparently healthy cattle (n=692), DNA was extracted and the prevalence of Babesia and Anaplasma species was analyzed by PCR. The results confirmed the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale in cattle in northern Sudan with overall prevalence rates of 4.0%, 1.9% and 6.1%, respectively. Statistical analysis revealed that the prevalence of B. bigemina, B. bovis and A. marginale varies significantly between Sudanese states as well as in different age groups, while gender seems not to have a significant effect on the prevalence of these pathogens among Sudanese cattle. The highest prevalence for B. bigemina was found in the Aljazirah State while the highest number of A. marginale positive samples was reported in River Nile. 相似文献
612.
Beltran E Dennis R Foote A De Risio L Matiasek L 《Veterinary radiology & ultrasound》2012,53(4):417-419
A 7-year-old male neutered domestic short-haired cat had depression for 5 months and acute blindness. A lesion at the level of the rostral and middle cranial fossae was suspected. A large pituitary mass compressing the optic chiasm was detected in magnetic resonance images and there was also evidence of recent intratumoral hemorrhage, leading to a diagnosis of pituitary apoplexy; these findings were confirmed at postmortem examination. Pituitary apoplexy is a clinical syndrome characterized by acute neurologic signs related to hemorrhagic infarction within a pituitary tumor. Pituitary apoplexy should be considered in patients with acute onset of blindness and altered mental status. 相似文献
613.
Cecilia Robat Ruth Houseright Joanne Murphey Saundra Sample Marie Pinkerton 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2016,45(3):484-489
An 11‐year‐old neutered male Alaskan Malamute mixed‐breed dog was presented with a complaint of polyuria/polydipsia (PU/PD), weight loss, tachypnea, regurgitation, and a previous history of nontreated osteosarcoma of the right distal radius, diagnosed 21 months prior. On physical examination, an abdominal mass was palpated. The abdominal mass was aspirated and cytologically diagnosed as a neuroendocrine tumor, suspected to be a pheochromocytoma. Laboratory examination revealed a mild anemia and thrombocytopenia, markedly elevated ATP and ALP activities, and moderate hypercalcemia. A low‐dose dexamethasone suppression test and endogenous adrenocorticotropic hormone (ACTH) concentration were compatible with pituitary hyperadrenocorticism. On urinalysis, proteinuria was noted as well as a high urine metanephrine/creatinine ratio, consistent with a diagnosis of pheochromocytoma. The dog was treated with supportive care and euthanized 6 months later due to decreasing quality of life. On necropsy, an extra‐adrenal pheochromocytoma (paraganglioma) was diagnosed in the caudal abdomen, and a pituitary adenoma and an osteosarcoma of the right distal radius were confirmed. 相似文献
614.
Evidence for a functional bone morphogenetic protein (BMP) system in the porcine ovary 总被引:3,自引:0,他引:3
Bone morphogenetic proteins (BMPs) play important roles in controlling fertility and ovulation rate. There is however, little information on the BMP system in the ovary of a large polyovular species. The aims of the present study were to investigate BMP-2 and -6 protein expression in the porcine ovary, their effects on granulosa cells in culture and their mechanism of action. Cells and oocytes were recovered from healthy antral follicles 2–6 mm in diameter. When assessed by Western blotting, oocytes and follicular fluid contained BMP-2 and -6. In addition, BMP-2 and -6 were observed in granulosa cells and BMP-2 was also found in theca cells. Granulosa cells were cultured in a serum-free system for 144 h in the presence of increasing doses (0, 3, 30 and 100 ng/ml) of BMP-2 or BMP-6. Both BMPs suppressed progesterone production in a dose-dependent manner after 48 h (P < 0.001) and 144 h (P < 0.05). Only BMP-6 stimulated cell proliferation at 100 ng/ml (P < 0.05). Investigation into the mechanism of action found that BMP-2 and -6 decreased cyclic adenosine monophosphate (cAMP) production (P < 0.01), expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) protein (P < 0.001) and steroidogenic acute regulatory protein (StAR) (BMP-6 only; P < 0.05). This supports the hypothesis that BMP-2 and -6 act as luteinization inhibitors. In conclusion, these findings provide evidence for the presence of a complex signalling mechanism in the porcine ovary and suggest that both BMP-2 and -6 may act in a paracrine manner to control granulosa cell function in this large polyovulatory species. 相似文献
615.
Hampered cumulus expansion of porcine cumulus‐oocyte complexes by excessive presence of alpha2‐macroglobulin is likely mediated via inhibition of zinc‐dependent metalloproteases 下载免费PDF全文
Ruth Appeltant Dominiek Maes Jo Bijttebier Katleen Van Steendam Hans Nauwynck Ann Van Soom 《Animal Science Journal》2017,88(9):1279-1290
In vitro maturation (IVM) in serum causes hampered expansion of porcine cumulus‐oocyte complexes (COCs) due to excessive alpha2‐macroglobulin (A2M). This study investigated two hypotheses that could explain the effect of A2M: (i) binding of epidermal growth factor (EGF) to A2M, followed by its decreased availability; and (ii) inhibition of zinc‐dependent metalloproteases. Cumulus expansion was evaluated based on the diameter of the COCs, the proportion of COCs participating in a floating cloud and the proportion of COCs with loss of cumulus cells. The first hypothesis of decreased EGF availability was tested by increasing the EGF concentration (20 and 50 ng/mL vs. 10 ng/mL), but was not confirmed because cumulus expansion did not improve. To verify the second hypothesis of inhibited zinc‐dependent metalloproteases, the effect of tissue inhibitor of metalloproteases‐3 (TIMP‐3) on cumulus expansion during IVM with and without A2M was investigated. To immuno‐neutralize A2M, serum was pre‐incubated with A2M antibodies. Impaired cumulus expansion because of TIMP‐3 could only be observed during IVM in 10% of serum with A2M antibodies. No effect of TIMP‐3 was observed in medium without A2M antibodies. These results indicate that A2M and TIMP‐3 share a common target, a zinc‐dependent metalloprotease. Future research is directed toward the identification of the protease involved. 相似文献
616.
617.
Effect of synthetic auxins on fruit size of five cultivars of Japanese plum (Prunus salicina Lindl.)
Most of the Japanese plum (Prunus salicina) cultivars grown in Israel produce relatively small fruit. Application of 2 l solution tree−1 of 25 mg l−1 2,4-dichlorophenoxypropionic acid (2,4-DP) as butoxyethyl ester (Power™), 15 mg l−1 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) as free acid (Maxim®), or 25 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) + 30 mg l−1 naphthaleneacetic acid (NAA) (0.3% Amigo™) at the beginning of pit-hardening, when fruitlet diameter was ca. 22 mm, caused an appreciable and significant increase in fruit size. The yield of large fruit per cv.: ‘Kesselmen’ (100% increase), ‘Songold’ (100%), ‘Black Diamond’ (800%), ‘Royal Diamond’ (160%) and ‘Royal Zee’ (100%). As a result, the total yield of all five cultivars was also increased dramatically. Anatomical studies with ‘Songold’ revealed that the main effect of these synthetic auxins was via direct stimulation of fruit cell enlargement. The above auxins had no negative effect either on fruit quality at harvest (and after 1 week in shelf-life), or on return yield in the following year. 相似文献
618.
Wardle DA Bardgett RD Callaway RM Van der Putten WH 《Science (New York, N.Y.)》2011,332(6035):1273-1277
Ecosystems worldwide are losing some species and gaining others, resulting in an interchange of species that is having profound impacts on how these ecosystems function. However, research on the effects of species gains and losses has developed largely independently of one another. Recent conceptual advances regarding effects of species gain have arisen from studies that have unraveled the mechanistic basis of how invading species with novel traits alter biotic interactions and ecosystem processes. In contrast, studies on traits associated with species loss are fewer, and much remains unknown about how traits that predispose species to extinction affect ecological processes. Species gains and losses are both consequences and drivers of global change; thus, explicit integration of research on how both processes simultaneously affect ecosystem functioning is key to determining the response of the Earth system to current and future human activities. 相似文献