全文获取类型
收费全文 | 1147篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
林业 | 113篇 |
农学 | 21篇 |
基础科学 | 12篇 |
259篇 | |
综合类 | 130篇 |
农作物 | 116篇 |
水产渔业 | 34篇 |
畜牧兽医 | 376篇 |
园艺 | 28篇 |
植物保护 | 103篇 |
出版年
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 17篇 |
2019年 | 20篇 |
2018年 | 26篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 17篇 |
2014年 | 28篇 |
2013年 | 53篇 |
2012年 | 48篇 |
2011年 | 56篇 |
2010年 | 32篇 |
2009年 | 39篇 |
2008年 | 45篇 |
2007年 | 51篇 |
2006年 | 60篇 |
2005年 | 71篇 |
2004年 | 43篇 |
2003年 | 53篇 |
2002年 | 47篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 18篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1972年 | 7篇 |
1971年 | 8篇 |
1926年 | 11篇 |
1925年 | 10篇 |
1924年 | 7篇 |
排序方式: 共有1192条查询结果,搜索用时 15 毫秒
991.
992.
Jais A Klein D Wolfesberger B Walter I 《Veterinary immunology and immunopathology》2011,140(3-4):207-214
The role of VEGF and its receptors has extensively been studied in tumours. In contrast, the presence and function of VEGF in normal tissues like the lymph node has not been given much attention until now. To study the expression of VEGF, VEGFR-1, VEGFR-2 and VEGFR-3 in the heterogenous cell population of the canine lymph node, laser capture microdissection was used to isolate pure cell fractions of macrophages, lymphocytes, endothelial cells, and capsule cells of the canine lymph node. To clarify if macrophages take up VEGF from the environment or express VEGF, VEGFR-1, VEGFR-2 or VEGFR-3 themselves, the mRNA expression was studied by real-time RT-PCR. After RNA isolation and subsequent analysis with the Agilent 2100 Bioanalyzer only RNA samples with appropriate RNA integrity were used for real-time PCR. For the accurate relative quantification of mRNA expression levels several reference genes were evaluated. It was shown that the reference genes HPRT1 and B2M serve as reliable reference genes for gene expression studies in the canine lymph node. Expression data analysis revealed no significant difference in VEGF expression levels between endothelial cells and the other investigated cells. VEGFR-1 expression was significantly lower in lymphocytes. Also macrophages showed a highly significant lower expression of VEGFR-1 compared to endothelial cells. In addition, the VEGFR-2 expression in lymphocytes and macrophages was significantly lower in comparison to endothelial cells. We were not able to detect VEGFR-3 mRNA in the lymphocyte cell population, in macrophages and cells of the lymph node capsule VEGFR-3 was expressed at very low levels. It was shown that laser capture microdissection in combination with quantitative real-time PCR is a valuable tool for studying the expression patterns of specific cells in their microenvironment. Our results support the hypothesis that VEGF and its receptors have other biological roles besides stimulating angiogenesis in the normal lymph node. These biological functions need to be clarified in further studies. 相似文献
993.
Di Guardo G Di Cesare A Otranto D Casalone C Iulini B Mignone W Tittarelli C Meloni S Castagna G Forster F Kennedy S Traversa D 《Veterinary parasitology》2011,183(1-2):31-36
This study reports the occurrence of Toxoplasma gondii in the brain of three striped dolphins (Stenella ceoruleoalba) found stranded on the Ligurian Sea coast of Italy between 2007 and 2008. These animals showed a severe, subacute to chronic, non-purulent, multifocal meningo-encephalitis, with the cerebral parenchyma of two dolphins harbouring protozoan cysts and zoites immunohistochemically linked to T. gondii. Molecular, phylogenetic and mutation scanning analyses showed the occurrence of Type II and of an atypical Type II T. gondii isolates in one and two dolphins, respectively. In spite of the different molecular patterns characterizing the above T. gondii genotypes, the brain lesions observed in the three animals showed common microscopic features, with no remarkable differences among them. The role of T. gondii in causing the meningo-encephalitis is herein discussed. 相似文献
994.
995.
996.
Erlacher-Reid C Hoffman WE Priede M Pulver R Tuttle AD 《Journal of zoo and wildlife medicine》2011,42(4):671-679
The primary purpose of this study was to establish plasma biochemistry parameters for healthy recently wild-caught purple mouth moray eels (Gymnothorax vicinus) to provide a baseline of data for improved medical care in an aquarium or zoologic setting and for wild health assessments. Thirty-one clinically healthy purple mouth moray eels of unknown age and sex were caught from the wild, and were anesthetized 50 days following capture for blood collection from the ventral coccygeal vein. The median plasma biochemistry values were as follows: hematocrit = 21%, creatinine kinase = 2,100 U/L, lactate dehydrogenase = 97 U/L, aspartate aminotransferase = 88 U/L, alanine aminotransferase = 51 U/L, alkaline phosphatase 3,939 U/L, gamma-glutamyl transpeptidase = 1 U/L, amylase = 40 U/L, blood urea nitrogen = < 11 mg/dl, glucose = 21 mg/dl, calcium = 12.5 mg/dl, triglyceride = 206 mg/dl, creatinine = 0.1 mg/dl, cholesterol = 334 mg/dl, total bilirubin = < 0.1 mg/dl, phosphorus = 6.5 mg/dl, total protein = 4.2 g/dl, albumin = 1.5 g/dl, globulin = 2.7 g/dl, albumin/ globulin ratio = 0.6, sodium = 185 mmol/L, potassium = 3.7 mmol/L, and chloride = 175 mmol/L. Alkaline phosphatase isoenzyme results indicate that the majority of the plasma alkaline phosphatase is the liver isoenzyme. The data acquired in this study also provide baseline values for cholesterol and triglycerides in recently wild-caught moray eels to aid in monitoring elevations to these values in an aquarium setting over time so adjustments to the dietary regime may be utilized to prevent or improve conditions such as lipid keratopathy. 相似文献
997.
Stützer B Simon K Lutz H Majzoub M Hermanns W Hirschberger J Sauter-Louis C Hartmann K 《Journal of Feline Medicine and Surgery》2011,13(2):81-87
In the past, feline leukaemia virus (FeLV) infection, and also latent FeLV infection, were commonly associated with lymphoma and leukaemia. In this study, the prevalence of FeLV provirus in tumour tissue and bone marrow in FeLV antigen-negative cats with these tumours was assessed. Seventy-seven diseased cats were surveyed (61 antigen-negative, 16 antigen-positive). Blood, bone marrow, and tumour samples were investigated by two polymerase chain reaction (PCR) assays detecting deoxyribonucleic acid (DNA) sequences of the long terminal repeats (LTR) and the envelope (env) region of the FeLV genome. Immunohistochemistry (IHC) was performed in bone marrow and tumour tissue. None of the antigen-negative cats with lymphoma was detectably infected with latent FeLV. The prevalence of FeLV viraemia in cats with lymphoma was 20.8%. This suggests that causes other than FeLV play a role in tumorigenesis, and that latent FeLV infection is unlikely to be responsible for most feline lymphomas and leukaemias. 相似文献
998.
Jerry D. Volesky Walter H. Schacht Ann E. Koehler Erin Blankenship Patrick E. Reece 《Strength and Conditioning Journal》2011,64(5):506-513
Root growth is important to the competitive ability of plants, and understanding how herbage defoliation affects root growth has implications for development of management strategies. Objectives were to determine the effects of defoliation intensity and frequency on root characteristics and herbage production of slender wheatgrass (Elymus trachycaulus [Link.] Shinners), Nebraska sedge (Carex nebrascensis C. Dewey), and “Steadfast” birdsfoot trefoil (Lotus corniculatus L.). Plants of each species were transplanted into containers that had been placed in the ground at wet meadow field sites the prior year. There were eight replications of a control and five defoliation treatments, which were combinations of different frequencies (two or five times) and intensities (light or heavy) and haying. Treatments were applied for a single growing season, and aboveground biomass was collected. Containers were extracted in October, and plant crowns, rhizomes, and roots were separated from the soil. Defoliation treatment did not affect total root weight, length, and surface area of Nebraska sedge or birdsfoot trefoil (P>0.10). Slender wheatgrass total root weight was less when defoliated five times (4.46 g·container?1) than when defoliated twice (6.62 g·container?1) during the growing season. More frequent defoliation of slender wheatgrass also reduced length (20%) and surface area (21%) compared to less frequent defoliation. However, defoliation frequency did not affect aboveground biomass. Defoliation intensity did not affect aboveground production or root characteristics of the three species. Abundant soil moisture in meadows likely buffers negative effects of defoliation. For all species, two defoliation events (e.g., haying followed by grazing) does not appear to negatively affect root growth and herbage production. 相似文献
999.
1000.
This paper describes results of the first field demonstration conducted to evaluate an innovative in situ chemical reduction technology to rapidly degrade 81?m2 of high concentrations of explosives contaminated soils at Ravenna Army Ammunition Plant, Ravenna, Ohio, USA. The primary explosives of concern and associated baseline levels of contamination were 2,4,6-trinitrotoluene (TNT) (383?mg/kg), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) (180?mg/kg), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (15?mg/kg). The in situ chemical treatment process involved selected reductant of sodium hydrosulfite (Na2S2O4) at optimal pH (9?C10) with appropriate buffers (e.g., sodium bicarbonate and potassium carbonate) that, when mixed with water, generate free radicals that react very rapidly to degrade nitroaromatics to carbon dioxide (CO2), formate (HCOO?C), and gaseous nitrogen compounds (NOx). Significant reductions in TNT, RDX, and HMX (>95?%) were observed within 24?h and achieved response complete in under 2?weeks after in situ application of the buffered sodium hydrosulfite. 相似文献