全文获取类型
收费全文 | 421篇 |
免费 | 31篇 |
国内免费 | 22篇 |
专业分类
林业 | 16篇 |
农学 | 13篇 |
基础科学 | 1篇 |
17篇 | |
综合类 | 51篇 |
农作物 | 34篇 |
水产渔业 | 74篇 |
畜牧兽医 | 135篇 |
园艺 | 85篇 |
植物保护 | 48篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 38篇 |
2012年 | 26篇 |
2011年 | 17篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1955年 | 4篇 |
排序方式: 共有474条查询结果,搜索用时 15 毫秒
1.
Alba Marina Cotes Philippe Lepoivre Jean Semal 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(5):497-506
An experimental protocol consisting in the colonisation of pregerminated bean seeds dressed withTrichoderma sp. was used in order to study the mechanisms correlated with the protective effect againstPythium splendens. Seed dressed with TH-11 (T. koningii) for 24 h presented a higher protective effect and a higher level of seed colonisation as compared to those dressed with TH-13 (T. longibranchiatum). The levels of seed coat colonisation by TH-11 and TH-13 was shown to be correlated with the carboxymethylcellulase activity, as measured in the seed coats retreived from germinating dressed bean seeds. The seed coat colonisation was also associated with an increased activities of endo-1,3--glucanase and endochitinase measured in seed extracts, and an inhibitory effect of seed extracts onPythium sporangia germination. Pretreatment of TH-13-dressed seeds with a commercial cellulase improved all parameters mentioned above, thus suggesting a role of cellulase activity in the colonisation process and the linked protective effect. The possible role of hydrolytic enzymes in the protective effects is discussed. 相似文献
2.
AIM:To study the effect of TGF-β1 and TNF-α antisense PS-ODNS on ex vivo expansion of hematopoietic stem/progenitor cells (HSPC). METHODS:CD34+cells were purified from fresh umbilical cord blood by immunomagnetic beads, and mononuclear cells were purified from bone marrow by Ficoll-hypaque. The effects of TGF-β1 and /or TNF-α antisense PS-ODNS on ex vivo expansion of CD34+ cells、CFU-GEMM、CFU-GM、CFU-E and BFU-E were detected by using liquid and semi-solid culture systems.RESULTS:TGF-β1 antisense PS-ODNS cooperated with cytokines increased the number of CD34+ cells, CFU-GEMM, CFU-GM, CFU-E and BFU-E, which was as 4, 2.6, 2.7, 1.8, 2.1 times as that of the control (the cytokines combination), respectively. TNF-α antisense PS-ODNS cooperated with cytokines respectively increased the number of CD34+ cells, CFU-GEMM, CFU-GM, CFU-E and BFU-E by 4, 2.9, 2.6, 1.7, 1.8 times as that of the control. The above two antisense PS-ODNS cooperated with cytokines could respectively increased the number of CD34+ cells, CFU-GEMM, CFU-GM, CFU-E and BFU-E by 5.3, 2.1, 2.7, 1.9, 1.8 times as that of the control.CONCLUSION:Inhibition of endogenous TGF-β1 and TNF-α by antisense PS-ODNS will be one of the effective methods to expand HSPC ex vivo. 相似文献
3.
AIM:To investigate the effect of tea-polyphenols (TP) on the activation of NF-κB and the expression of TGF-β1 mRNA in THP-1 cells (a human acute monocytic leukemia cell line). METHODS:THP-1 cells were incubated with the different concentrations of TP, VLDL, LDL or ox-LDL. In the THP-1 cellls, the nuclear malposition rate of NF-κB was detected with immunohistochemistry technique, the positive index of the TGF-β1 mRNA expression was detected by hybridization in situ, and accumulation of total cholesterol (TC) in cells incubated with 0.4-40 μg/L TP was determined with oxidase assay. RESULTS:The nuclear malposition rate of NF-κB, the positive index of the TGF-β1 mRNA expression and TC in THP-1 cells incubated with 0.4-40 μg/L of TP were lower than those with 0 μg/L of TP in TP-V group, TP-L group and TP-O (P<0.05). The differences of these markers in THP-1 cells incubated with more than 40 μg/L TP in TP-V group, TP-L group and TP-O were not statistically significant, compared with TP-C group (P>0.05). CONCLUSION:TP inhibited the activation of NF-κB, the expression of TGF-β1 mRNA and the foam cell formation in the mono-macrophage. 相似文献
4.
BACKGROUND: Beta-cypermethrin, a synthetic pyrethroid insecticide, was applied frequently in the control of health pests including houseflies, Musca domestica L., in China. However, different levels of resistance to beta-cypermethrin were monitored in field strains of houseflies. A strain of M. domestica, 4420-fold resistant to beta-cypermethrin after continuous 25 generations of selection, was used in this paper to determine the mode of inheritance of pyrethroid resistance. RESULTS: The estimated realized heritability (h(2)) of beta-cypermethrin resistance was 0.30 in this resistant strain. Results of bioassays showed no significant difference in values of LD(50) and slope of log dose-probit lines between reciprocal progenies F(1) and F'(1), and yielded values of - 0.10 (F(1)) and - 0.11 (F'(1)) for the degree of dominance (D). Chi-square analysis from responses of self-bred and backcross progenies (F(2), BC(1) and BC(2) respectively) indicated that the null hypothesis, a single gene responsible for resistance, was accepted. The minimum number of independent segregation genes was 0.93 for F(1) by Lande's method. CONCLUSION: It was concluded that beta-cypermethrin resistance in the housefly was inherited as a single, major, autosomal and incompletely recessive factor. These results would provide the basic information for pest management programmes. 相似文献
5.
Canine anal sac apocrine gland adenocarcinoma (ASAGAC) is an uncommon but highly invasive and metastatic malignancy. Toceranib phosphate (Palladia) is a receptor tyrosine kinase (RTK) inhibitor that targets several members of the split kinase RTK family. These membrane receptors are important for cell cycling, apoptosis and angiogenesis, all of which can contribute to carcinogenesis. The objective of this study was to evaluate archived, paraffin-embedded canine ASAGAC and normal canine anal sacs for immunohistochemical detection of Kit and platelet-derived growth factor receptor beta (PDGFR-β). Two of 77 neoplasms (2.6%) expressed Kit. Fifteen of the neoplasms (19.5%) were positive for PDGFR-β expression. None of the normal canine anal sac epithelium expressed Kit or PDGFR-β. Because of these results, further investigation should be considered to determine the role of RTKs in the clinical course and treatment of canine ASAGAC. 相似文献
6.
JS Munday H Bentall D Aberdein M Navarro FA Uzal S Brown 《New Zealand veterinary journal》2020,68(4):242-246
ABSTRACTCase history and clinical findings: A flock of 20 sheep was kept within three paddocks on a single property. None of the animals in the flock had been vaccinated against any disease for at least three years. Abdominal bloating and haemorrhagic diarrhoea were observed in Lamb 1 at 24 hours-of-age. The lamb subsequently died within an hour of the onset of clinical signs. Lamb 2 was 3-days-old when observed to be recumbent with opisthotonus. The lamb was treated with dextrose, vitamins B1 and B12, and penicillin G, but died 4 hours later.Pathological findings: Examination of Lamb 1 revealed markedly increased gas within the peritoneum and within dilated loops of intestine. The intestines were dark red and contained large quantities of haemorrhagic fluid. Histology of the intestines revealed peracute mucosal necrosis with minimal accompanying inflammation. The intestinal lumen contained cell debris, haemorrhage, and myriad large Gram-positive bacilli. The intestines of Lamb 2 did not appear bloated or reddened. However, multiple fibrin clots were visible within the pericardial sac. Histopathological examination revealed small foci of necrosis within the mucosa of the distal intestine. The necrotic foci were often associated with large numbers of large Gram-positive bacilli.Immunohistochemsitry and molecular biology: Intestinal samples from Lamb 1 were processed for Clostridium perfringens immunohistochemistry, which revealed large numbers of intralesional, positively immunostained rods. Fragments corresponding to the expected sizes for genes encoding alpha, beta, and epsilon C. perfringens typing toxins were amplified by PCR from DNA extracted from formalin-fixed sections of intestine.Diagnosis: Lamb dysentery due to C. perfringens type B.Clinical relevance: C. perfringens bacteria have a worldwide distribution, but disease due to C. perfringens type B has only been diagnosed in a small number of countries and has never been reported in New Zealand or Australia. C. perfringens type B produce both beta toxin and epsilon toxins, therefore both haemorrhagic enteritis and systemic vascular damage can develop. As many animals are exposed to C. perfringens without developing disease, there must be additional unknown factors that resulted in disease in these particular sheep. Vaccines that specifically protect against C. perfringens type B are available and may be recommended for use in smaller non-commercial flocks, as in the present case. 相似文献
7.
8.
Gene expression in black tiger prawns (Penaeus monodon) was studied following intra-muscular injection of CMVGal plasmid into the second abdominal segment. We used an in situ staining technique to detect -gal expression in one- and three-month-old injected prawns. We found that only one of the three-month-old prawns expressed the marker gene (2 days after injection), and the site of expression was confined to the sixth abdominal segment away from the injection site. We repeated the experiment on a new batch of three-month-old prawns, but using fluorometric determination technique. This time we found that -gal expression was detected (6/42) at the site of injection after 2, 7, and 14 days. In two other test samples, transgene expression was detected in the sixth abdominal segment only, further confirming the possibility of injected DNA dispersal. The results of the study also suggest that direct gene transfer is a feasible technique in black tiger prawns. 相似文献
9.
MEHDI Heydari 《干旱区科学》2019,11(1):43-57
This study aimed to investigate the interaction between regions with different climatic conditions(arid vs. semi-arid) and management(protected vs. unprotected) on the turnover and nestedness of vegetation in relation to physical, chemical and biological properties of soils in the Ilam Province of Iran. In each of the two regions, we sampled 8 sites(4 managed and 4 unmanaged sites) within each of which we established 4 circular plots(1000 m~2) that were used to investigate woody species, while two micro-plots(1 m×1 m) were established in each 1000-m~2 plot to analyze herbaceous species. In each sample unit, we also extracted three soil samples(0–20 cm depth) for measuring soil properties. The results indicated that the interaction between region and conservational management significantly affected the percent of canopy cover of Persian oak(Quercus brantii Linddl), soil respiration, substrate-induced respiration, as well as beta and gamma diversities and turnover of plant species. The percent of oak canopy cover was positively correlated with soil silt, electrical conductivity, available potassium, and alpha diversity, whereas it was negatively correlated with plant turnover. In addition, plant turnover was positively related to available phosphorus, while nestedness of species was positively related to organic carbon and total nitrogen. According to these results, we concluded that physical, chemical, and biological characteristics of limited ecological niche generally influenced plant diversity. Also, this study demonstrated the major contribution of the beta diversity on gamma diversity, especially in semi-arid region, because of the higher heterogeneity of vegetation in this area. 相似文献
10.
以K326、云烟85和红花大金元中部烟叶为材料,分析了相同生态条件下不同烤烟品种成熟及烘烤过程中烟叶类胡萝卜素含量的变化。结果表明:在烟叶成熟期和烘烤过程中,不同烤烟品种类胡萝卜素含量及成熟期降解速度均存在很大差异。K326欠熟烟叶中类胡萝卜素含量很高,但是随着叶片衰老变黄,类胡萝卜素含量大幅、快速降低。云烟85和红花大金元欠熟烟叶中类胡萝卜素含量明显低于K326,但红花大金元成熟期类胡萝卜素的降解幅度明显小于K326和云烟85。因此,红花大金元适熟和过熟烟叶中的类胡萝卜素含量均高于K326和云烟85。烘烤过程中3个烤烟品种烟叶的类胡萝卜素含量均呈现下降趋势,但以烘烤温度由25℃升至45℃的变黄期下降幅度最大,并且也呈现K326降解速度最快,红花大金元最慢的变化规律,因此,红花大金元初烤烟叶中的类胡萝卜素含量高于K326和烟85。 相似文献