全文获取类型
收费全文 | 297篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
林业 | 23篇 |
农学 | 6篇 |
65篇 | |
综合类 | 30篇 |
农作物 | 11篇 |
水产渔业 | 27篇 |
畜牧兽医 | 124篇 |
园艺 | 11篇 |
植物保护 | 13篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 12篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1950年 | 1篇 |
1948年 | 1篇 |
1933年 | 1篇 |
1932年 | 1篇 |
1931年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有310条查询结果,搜索用时 0 毫秒
31.
Solforosi L Criado JR McGavern DB Wirz S Sánchez-Alavez M Sugama S DeGiorgio LA Volpe BT Wiseman E Abalos G Masliah E Gilden D Oldstone MB Conti B Williamson RA 《Science (New York, N.Y.)》2004,303(5663):1514-1516
Neuronal death is a prominent, but poorly understood, pathological hallmark of prion disease. Notably, in the absence of the cellular prion protein (PrPC), the disease-associated isoform, PrPSc, appears not to be intrinsically neurotoxic, suggesting that PrPC itself may participate directly in the prion neurodegenerative cascade. Here, cross-linking PrPC in vivo with specific monoclonal antibodies was found to trigger rapid and extensive apoptosis in hippocampal and cerebellar neurons. These findings suggest that PrPC functions in the control of neuronal survival and provides a model to explore whether cross-linking of PrPC by oligomeric PrPSc can promote neuronal loss during prion infection. 相似文献
32.
Changelian PS Flanagan ME Ball DJ Kent CR Magnuson KS Martin WH Rizzuti BJ Sawyer PS Perry BD Brissette WH McCurdy SP Kudlacz EM Conklyn MJ Elliott EA Koslov ER Fisher MB Strelevitz TJ Yoon K Whipple DA Sun J Munchhof MJ Doty JL Casavant JM Blumenkopf TA Hines M Brown MF Lillie BM Subramanyam C Shang-Poa C Milici AJ Beckius GE Moyer JD Su C Woodworth TG Gaweco AS Beals CR Littman BH Fisher DA Smith JF Zagouras P Magna HA Saltarelli MJ Johnson KS Nelms LF Des Etages SG Hayes LS Kawabata TT 《Science (New York, N.Y.)》2003,302(5646):875-878
Because of its requirement for signaling by multiple cytokines, Janus kinase 3 (JAK3) is an excellent target for clinical immunosuppression. We report the development of a specific, orally active inhibitor of JAK3, CP-690,550, that significantly prolonged survival in a murine model of heart transplantation and in cynomolgus monkeys receiving kidney transplants. CP-690,550 treatment was not associated with hypertension, hyperlipidemia, or lymphoproliferative disease. On the basis of these preclinical results, we believe JAK3 blockade by CP-690,550 has potential for therapeutically desirable immunosuppression in human organ transplantation and in other clinical settings. 相似文献
33.
Tirichine L Sandal N Madsen LH Radutoiu S Albrektsen AS Sato S Asamizu E Tabata S Stougaard J 《Science (New York, N.Y.)》2007,315(5808):104-107
Legume root nodules originate from differentiated cortical cells that reenter the cell cycle and form organ primordia. We show that perception of the phytohormone cytokinin is a key element in this switch. Mutation of a Lotus japonicus cytokinin receptor gene leads to spontaneous development of root nodules in the absence of rhizobia or rhizobial signal molecules. The mutant histidine kinase receptor has cytokinin-independent activity and activates an Escherichia coli two-component phosphorelay system in vivo. Mutant analysis shows that cytokinin signaling is required for cell divisions that initiate nodule development and defines an autoregulated process where cytokinin induction of nodule stem cells is controlled by shoots. 相似文献
34.
35.
David Süss Michael Iwersen Vanessa Schweinzer Erika Gusterer Peter Kanz Stefanie Krieger Harald Pothmann Karen Wagener Michael Hoelker Dawit Tesfaye Karl Schellander Ariane Helmbrecht Claudia Parys Marc Drillich 《Reproduction in domestic animals》2019,54(9):1265-1273
There is evidence that supplementing methionine has positive effects on uterine environment, oocyte quality and embryo development in cattle. Thus, the objective of this study was to evaluate reproductive traits of cows supplemented with rumen‐protected methionine (RPM) during early to mid‐lactation in comparison with an untreated control group (CON). An additional focus was on the effect of puerperal diseases on reproductive performance parameters in RPM‐supplemented group MET and in CON. A total of 1,709 multiparous Holstein‐Friesian cows were enrolled in this field trial conducted on a commercial dairy farm in Slovakia. Cows were allocated at approximately 12 days post‐partum (dpp) to either CON or MET, the latter supplemented with 25.0 g–27.2 g RPM per cow per day incorporated into the total mixed ration (TMR) until leaving the study pen at approximately 140 dpp. The amount of RPM was calculated based on individual feed ingredients analysis and adjusted during the study period when TMR changed. Cows were monitored during the post‐partum period by vaginal examination (day 5 pp), measuring of beta‐hydroxybutyrate in blood (3, 5, and 8 dpp) and by vaginal examination, uterine cytology and measuring of back fat thickness by ultrasound (all at 31 ± 3 dpp). Compared with CON, cows supplemented with RPM did not show better reproduction performance parameters (first service submission rate, days to first service, conception risk, days open 140). Results from binary logistic regression model for the risk of conception showed that metritis had a significant effect, but the supplementation of methionine had not. Results of Cox regression analysis for the odds of conception within 140 dpp revealed only metritis and clinical endometritis as significant factors. In conclusion, supplementation of RPM had no beneficial effect on reproductive performance in this study farm compared with an untreated control group. 相似文献
36.
Malin Larm Bodil Elmhagen Sandra M Granquist Erika Brundin Anders Angerbjörn 《Human Dimensions of Wildlife》2018,23(3):257-272
There are both positive and negative impacts on wildlife associated with wildlife tourism. In Sweden, the endangered Arctic fox is subject to a growing tourist interest. In the Helags mountain region there are guided Arctic fox safari tours that provide visitors with information about the Arctic fox. A survey of five separate groups of visitors in the region revealed that knowledge about the status of Arctic foxes and awareness of the behavioral guidelines for Arctic fox encounters improved after participation in a safari tour and with increasing Arctic fox interaction. We propose a schematic model summarizing the diverse ways in which wildlife tourism affects wildlife and their relative importance for conservation. The Arctic fox population in Sweden is small and sensitive to disturbance, but the positive impacts of Arctic fox tourism seem to compensate for the negative and contribute to their conservation under the current level of tourism pressure. 相似文献
37.
Cerón JJ Carli E Tasca S Martinez-Subiela S Caldin M 《American journal of veterinary research》2008,69(9):1141-1147
OBJECTIVE: To evaluate the use of EDTA tubes for collection of blood samples for assays of secondary hemostasis in dogs. ANIMALS: 108 dogs of various ages, breeds, and sexes (19 healthy and 89 with abnormalities of secondary hemostasis). PROCEDURES: Blood samples were collected via cephalic venipuncture and transferred to sodium citrate tubes and EDTA tubes. Plasma was harvested from each type of tube for assays of concentrations of fibrinogen and D-dimer as well as prothrombin time, activated partial thromboplastin time, and antithrombin activity. Intra-assay and interassay precision and correlation coefficients for all hemostatic tests were calculated for each type of plasma sample. The effect of storage conditions on assay results for the 2 types of plasma samples was also evaluated. RESULTS: Results of hemostatic tests were highly correlated between citrated and EDTA-treated plasma samples. Intra-assay imprecision for all hemostatic tests with the exception of D-dimer concentration was < 10% for both citrated and EDTA-treated plasma samples; interassay imprecision was higher for EDTA-treated versus citrated plasma samples. Storage of plasma samples for 1 hour did not result in significantly different assay results for either type of plasma sample, but storage for 2 hours significantly affected values for EDTA-treated plasma samples. CONCLUSIONS AND CLINICAL RELEVANCE: Although evaluation of the sensitivity and specificity of hemostatic tests that use EDTA-treated plasma samples is required, EDTA may be a suitable alternative to sodium citrate as an anticoagulant for use in hemostatic testing in conditions in which tests could be performed within 1 hour after sample collection. 相似文献
38.
Saito KC Bechara GH Nunes ET de Oliveira PR Denardi SE Mathias MI 《Veterinary parasitology》2005,129(3-4):299-311
This study presents the morphology of the ovary, as well as the dynamics of the vitellogenesis process in oocytes of the cattle-tick Boophilus microplus. The ovary of these individuals is of the panoistic type; therefore, it lacks nurse cells. This organ consists of a single tubular structure, continuous, and composed of a lumen delimitated by a wall of small epithelial cells with rounded nuclei. In this tick species, the oocytes were classified into six stages varying from I to VI and according to: cytoplasm appearance and presence of the germ vesicle, yolk granules, and chorion. Oocytes of various sizes and at different developmental stages remain attached to the ovary through a cellular pedicel until completing stage V. Afterwards, they are liberated into the lumen and from there to the exterior. Some oocytes (classified as type VI) showed an atypical appearance indicating that some of the cellular components would be undergoing a degenerative process and/or reabsorption. 相似文献
39.
40.
Freezing technologies are very important to preserve gametes and embryos of animals with a good pedigree or those having high genetic value. The aim of this work was to compare immature and in vitro matured porcine oocytes regarding their morphology and ability to be fertilised after vitrification by the open pulled straw (OPS) method. In four experiments 830 oocytes were examined. To investigate the effect of cumulus cells on oocyte survival after OPS vitrification, both denuded and cumulus-enclosed oocytes were vitrified at the germinal vesicle (GV) stage, then after vitrification they were matured in vitro. Besides, in vitro matured oocytes surrounded with a cumulus and those without a cumulus were also vitrified. The survival of oocytes was evaluated by their morphology. After in vitro fertilisation the rates of oocytes penetrated by spermatozoa were compared. Our results suggest that the vitrification/warming procedure is the most effective in cumulus-enclosed oocytes (22.35 +/- 1.75%). There was no difference between the order of maturation and vitrification in cumulus-enclosed oocytes, which suggests the importance of cumulus cells in protecting the viability of oocytes during cryopreservation. 相似文献