全文获取类型
收费全文 | 9967篇 |
免费 | 548篇 |
国内免费 | 9篇 |
专业分类
林业 | 767篇 |
农学 | 330篇 |
基础科学 | 85篇 |
2093篇 | |
综合类 | 1543篇 |
农作物 | 436篇 |
水产渔业 | 581篇 |
畜牧兽医 | 3675篇 |
园艺 | 274篇 |
植物保护 | 740篇 |
出版年
2023年 | 58篇 |
2022年 | 83篇 |
2021年 | 163篇 |
2020年 | 185篇 |
2019年 | 209篇 |
2018年 | 193篇 |
2017年 | 208篇 |
2016年 | 235篇 |
2015年 | 168篇 |
2014年 | 259篇 |
2013年 | 455篇 |
2012年 | 538篇 |
2011年 | 662篇 |
2010年 | 415篇 |
2009年 | 346篇 |
2008年 | 584篇 |
2007年 | 575篇 |
2006年 | 609篇 |
2005年 | 581篇 |
2004年 | 501篇 |
2003年 | 505篇 |
2002年 | 481篇 |
2001年 | 147篇 |
2000年 | 149篇 |
1999年 | 168篇 |
1998年 | 108篇 |
1997年 | 89篇 |
1996年 | 89篇 |
1995年 | 77篇 |
1994年 | 56篇 |
1993年 | 74篇 |
1992年 | 74篇 |
1991年 | 89篇 |
1990年 | 87篇 |
1989年 | 89篇 |
1988年 | 70篇 |
1987年 | 85篇 |
1986年 | 59篇 |
1985年 | 88篇 |
1984年 | 59篇 |
1983年 | 79篇 |
1982年 | 46篇 |
1981年 | 40篇 |
1980年 | 42篇 |
1979年 | 47篇 |
1978年 | 42篇 |
1976年 | 38篇 |
1974年 | 36篇 |
1973年 | 44篇 |
1969年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The results of a computer model designed to demonstrate the effect of antimicrobial exposure (therapy) on the likelihood of isolating putative pathogens and on the proportion of successfully isolated organisms resistant to specific antimicrobials are presented. The results indicate that the observed percentage resistant is not a reliable indicator of the actual percentage resistant in the source population. Data from the Bruce County Beef Project in 1979-80 are used to verify some of the assumptions used in the model. 相似文献
993.
994.
995.
996.
Five soil profiles from a saline zone in the province of Seville (“Marismas del Guadalquivir”, SW. Spain) and one from an adjacent non-saline zone, have been analyzed in order to determine their physical and chemical properties and their classification.All of these soils are recent and of fine texture. Hydraulic conductivity, except in top layers, as well as aeration porosity, is always low; non-available water holding capacity and linear extensibility, high. Differences are however found between those located near the river channel and those at the limit of Marismas in contact with vertisols, due to parent material, situation and use. Particularly noticeable is the progressive increment of their vertic character. 相似文献
997.
998.
999.
Y Gu A P Schinckel T G Martin J C Forrest C H Kuei L E Watkins 《Journal of animal science》1992,70(6):1708-1718
Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight. 相似文献
1000.
Gregory K. Ogilvie Richard B. Ford David M. Vail Lisa M. Walters M. D. Salman C. Babineau Martin J. Fettman 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(1):62-66
After a 12-hour fast, blood samples were obtained from 31 dogs with previously untreated lymphoma. Blood samples were also collected from 16 of these dogs after up to 5 treatments with doxorubicin (30 mg/m2 intravenously every 3 weeks). All 16 dogs underwent complete remission. Five dogs were re-evaluated after relapse and after overt signs of cancer cachexia had become clinically apparent. Samples were assayed for 8 quantitative parameters: total cholesterol (T-CH) and total triglyceride (T-TG) concentrations, and the concentration of cholesterol and triglyceride in each of the three major lipoprotein fractions, very-low-density lipoprotein (VLDL-CH and VLDL-TG), low-density lipoprotein (LDL-CH and LDL-TG), and high-density lipoprotein (HDL-CH and HDL-TG). The results were compared with those from 20 healthy control dogs of similar weight and age before and 3 weeks after being given one dose of doxorubicin (30 mg/m2 intravenously). The administration of doxorubicin to control dogs resulted in a significant (P> .05) decrease in T-CH, LDL-CH, and HDL-CH, as well as a significant increase in VLOL-TG and HDL-TG. When compared with untreated controls, untreated dogs with lymphoma had significantly higher concentrations of VLDL-CH, T-TG, VLDL-TG, LDL-TG, and HDL-TG, and significantly lower concentrations of HDL-CH. HDL-TG and VLDL-TG concentrations from dogs with lymphoma were significantly increased above pretreatment values after relapse and development of overt signs of cancer cachexia. Dogs in remission that were evaluated after one dose of doxorubicin had significantly higher concentrations of T-CH, VLDL-CH, T-TG, and LDL-TG when compared with controls that were evaluated after an identical dose of doxorubicin. HDL-TG increased significantly over pretreatment values in dogs with lymphoma after doxorubicin therapy. These results suggest that dogs with lymphoma have significant alterations in lipid profiles, and with the possible exception of HDL-CH, these abnormalities do not normalize when clinical remission is obtained. 相似文献