全文获取类型
收费全文 | 1231篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
林业 | 65篇 |
农学 | 25篇 |
基础科学 | 18篇 |
239篇 | |
综合类 | 159篇 |
农作物 | 61篇 |
水产渔业 | 94篇 |
畜牧兽医 | 481篇 |
园艺 | 36篇 |
植物保护 | 103篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 18篇 |
2019年 | 24篇 |
2018年 | 23篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 18篇 |
2013年 | 60篇 |
2012年 | 72篇 |
2011年 | 87篇 |
2010年 | 62篇 |
2009年 | 56篇 |
2008年 | 80篇 |
2007年 | 80篇 |
2006年 | 86篇 |
2005年 | 69篇 |
2004年 | 72篇 |
2003年 | 78篇 |
2002年 | 85篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有1281条查询结果,搜索用时 0 毫秒
171.
In trace metal (TM)-contaminated agricultural soils, management of TM availability is important for safe crop production. In addition, maintenance or improvement of soil quality is vital for sustainable crop cultivation. Decreased TM phytoavailability and increased soil quality can be achieved by the application of various immobilizing agents to soil, which can supply both macronutrients and organic matter. This study investigated the long-term influences of four common immobilizing agents on so... 相似文献
172.
Yankovskaya V Horsefield R Törnroth S Luna-Chavez C Miyoshi H Léger C Byrne B Cecchini G Iwata S 《Science (New York, N.Y.)》2003,299(5607):700-704
The structure of Escherichia coli succinate dehydrogenase (SQR), analogous to the mitochondrial respiratory complex II, has been determined, revealing the electron transport pathway from the electron donor, succinate, to the terminal electron acceptor, ubiquinone. It was found that the SQR redox centers are arranged in a manner that aids the prevention of reactive oxygen species (ROS) formation at the flavin adenine dinucleotide. This is likely to be the main reason SQR is expressed during aerobic respiration rather than the related enzyme fumarate reductase, which produces high levels of ROS. Furthermore, symptoms of genetic disorders associated with mitochondrial SQR mutations may be a result of ROS formation resulting from impaired electron transport in the enzyme. 相似文献
173.
Peter Graham Coulson Jeffery Vincent Norriss Gary Jackson David Victor Fairclough 《Fisheries Management and Ecology》2019,26(3):236-248
The reproductive biology of Centroberyx gerrardi (Günther) was investigated across ~2,000 km of its southern Australian distribution, encompassing different jurisdictions and varying environmental features. Greater gonad mass and prevalence of spawning fish, along with lower ratios of lengths at maturity:maximum lengths and ages at maturity:maximum ages, were identified at the western‐most (Capes) and eastern‐most (Great Australian Bight; GAB) regions. Across the study region, spawning peaks in summer/autumn, when water temperatures are warmest. Regional differences in potential “reproductive output,” while not consistent with the eastward decline in mean monthly water temperature, may instead be related to summer upwelling in the Capes and GAB, driving greater oceanic productivity prior to peak spawning, supporting larval survival. In autumn, the prevailing southward and eastward flowing, downwelling Leeuwin Current (LC) strengthens, providing a dispersal mechanism along the west and south Australian coasts, but limiting upwelling effects. Predicted changes in environmental conditions and their potential impacts on C. gerrardi are discussed, in particular how these factors may affect recruitment to stocks and fisheries, requiring a better understanding of source‐sink relationships for this species. As environmental changes occur, management strategies to sustain fish resources must adapt to spatially variable and changing reproductive output and be collaborative across jurisdictions. 相似文献
174.
175.
Abtahian F Guerriero A Sebzda E Lu MM Zhou R Mocsai A Myers EE Huang B Jackson DG Ferrari VA Tybulewicz V Lowell CA Lepore JJ Koretzky GA Kahn ML 《Science (New York, N.Y.)》2003,299(5604):247-251
Lymphatic vessels develop from specialized endothelial cells in preexisting blood vessels, but the molecular signals that regulate this separation are unknown. Here we identify a failure to separate emerging lymphatic vessels from blood vessels in mice lacking the hematopoietic signaling protein SLP-76 or Syk. Blood-lymphatic connections lead to embryonic hemorrhage and arteriovenous shunting. Expression of slp-76 could not be detected in endothelial cells, and blood-filled lymphatics also arose in wild-type mice reconstituted with SLP-76-deficient bone marrow. These studies reveal a hematopoietic signaling pathway required for separation of the two major vascular networks in mammals. 相似文献
176.
177.
178.
179.
180.
Myers CJ Magdesian KG Kass PH Madigan JE Rhodes DM Marks SL 《Veterinary journal (London, England : 1997)》2009,181(2):137-144
This retrospective study describes the use of and complications associated with parenteral nutrition (PN) administration to 53 equine neonates at the University of California Veterinary Medical Teaching Hospital. Medical records were examined and information obtained on signalment, physical examination, clinical diagnosis, outcome, total hospitalization time, insulin administration, microbiology culture results, other complications (i.e. thrombophlebitis) and necropsy findings. Complete blood count and serum biochemistry analytes, venous blood gas, serum electrolyte and glucose concentrations, and blood lactate concentration results were compared before and during PN administration in all foals. Seventeen foals (32%) developed hypertriglyceridemia (>200mg/dL). Triglyceride concentrations >200mg/dL were significantly (P=0.049) associated with non-survival. Forty-seven foals (89%) developed hyperglycemia (blood glucose >120mg/dL) and eight (15%) developed catheter-related complications (thrombosis or local sepsis). Packed cell volume, total protein, creatinine, blood urea nitrogen, and sorbitol dehydrogenase concentrations decreased while foals were on PN, while serum chloride concentration increased. This study highlighted that hypertriglyceridemia during the acute phase of neonatal illness may be detrimental to outcome, and that the safety of lipid-containing solutions in foals warrants further study. 相似文献