全文获取类型
收费全文 | 2272篇 |
免费 | 127篇 |
国内免费 | 1篇 |
专业分类
林业 | 67篇 |
农学 | 48篇 |
基础科学 | 10篇 |
310篇 | |
综合类 | 377篇 |
农作物 | 111篇 |
水产渔业 | 178篇 |
畜牧兽医 | 1119篇 |
园艺 | 35篇 |
植物保护 | 145篇 |
出版年
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 27篇 |
2018年 | 20篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 24篇 |
2014年 | 28篇 |
2013年 | 69篇 |
2012年 | 72篇 |
2011年 | 96篇 |
2010年 | 48篇 |
2009年 | 39篇 |
2008年 | 99篇 |
2007年 | 89篇 |
2006年 | 123篇 |
2005年 | 106篇 |
2004年 | 97篇 |
2003年 | 111篇 |
2002年 | 99篇 |
2001年 | 40篇 |
2000年 | 45篇 |
1999年 | 44篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 25篇 |
1992年 | 46篇 |
1991年 | 38篇 |
1990年 | 36篇 |
1989年 | 41篇 |
1988年 | 34篇 |
1987年 | 45篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 26篇 |
1982年 | 19篇 |
1979年 | 21篇 |
1978年 | 21篇 |
1976年 | 20篇 |
1975年 | 25篇 |
1974年 | 36篇 |
1973年 | 29篇 |
1972年 | 23篇 |
1971年 | 20篇 |
1970年 | 20篇 |
1969年 | 16篇 |
1966年 | 16篇 |
排序方式: 共有2400条查询结果,搜索用时 15 毫秒
991.
992.
A survey study was conducted to determine the generality of chlorinated biphenyl formation from the photolysis of chlorine-containing herbicides in aqueous solution. Seven herbicides from the phenylurea, anilide and carbamate classes were examined. In this study, the photoreaction under investigation proceeded via the coupling of two herbicide molecules to yield a chlorinated biphenyl with concomitant loss of hydrogen chloride. In preliminary studies using ultraviolet lamps, 4-chlorophenyl methylcarbamate (PPG-124) gave a chlorinated biphenyl with only one carbamate side chain, and chlorpropham gave no chlorinated biphenyl, but rather a hydroxylated biphenyl. Employing ultraviolet lamps or natural sunlight, photolyses of monuron, diuron, linuron, metobromuron and propanil produced halogenated biphenyls according to the photocoupling reaction under investigation. All yields of chlorinated biphenyls from sunlight photolysis were approximately 1% or lower. 相似文献
993.
994.
995.
Rawson EA Aronsohn MG Burk RL 《Journal of the American Animal Hospital Association》2005,41(3):166-170
Simultaneous bilateral femoral head and neck ostectomy (FHO) was performed on 15 dogs for severe bilateral hip dysplasia. A follow-up survey was performed 6 to 48 months after surgery to assess the postoperative recovery and activity levels of the operated dogs. All dogs had normal activity levels and were pain free according to their owners. Owner satisfaction regarding the outcome of the surgery was high. Simultaneous bilateral FHO was a viable surgical option for the treatment of painful bilateral hip disease in dogs, especially when other surgical options were not indicated or were cost prohibitive. 相似文献
996.
997.
Association between exercise-induced pulmonary hemorrhage and performance in Thoroughbred racehorses
Hinchcliff KW Jackson MA Morley PS Brown JA Dredge AE O'Callaghan PA McCaffrey JP Slocombe RE Clarke AE 《Journal of the American Veterinary Medical Association》2005,227(5):768-774
OBJECTIVE: To determine whether exercise-induced pulmonary hemorrhage (EIPH) was associated with racing performance inThoroughbred horses not medicated with furosemide and not using nasal dilator strips. DESIGN: Observational cross-sectional study. ANIMALS: 744 two- to 10-year-old Thoroughbred horses racing in Melbourne, Australia. PROCEDURE: Horses were enrolled prior to racing, and a tracheobronchoscopic examination was performed after 1 race. Examinations were recorded on videotape, and presence and severity (grade 0 to 4) of EIPH were subsequently determined by 3 observers blinded to the horses' identity. Race records were abstracted for each horse examined. RESULTS: Overall, 52.1% of horses eligible for participation in the study were examined, and horses that were examined did not differ from horses that were not examined in regard to age, sex distribution, or proportion of horses that won or finished in the first 3 positions. Horses with EIPH grades < 1 were 4.0 times as likely to win, 1.8 times as likely to finish in the first 3 positions, and 3.03 times as likely to be in the 90th percentile or higher for race earnings as were horses with grades > 2. Horses with EIPH grades > 1 finished significantly farther behind the winner than did horses without EIPH. However, odds that horses with grade 1 EIPH would win or finish in the first 3 positions were not significantly different from odds for horses without EIPH. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips. 相似文献
998.
Frana TS Carlson SA Rauser DC Jones BD Fergen BJ Griffith RW 《American journal of veterinary research》2004,65(12):1616-1620
OBJECTIVE: To investigate the effect of an Escherichia that produced microcin 24 (Mcc24) on shedding of of Salmonella enterica serotypeTyphimurium in swine and evaluate evidence of in vivo activation of the Mcc24-mediated, multiple-antibiotic resistance (mar) operon. ANIMALS: 36 crossbred weaned pigs. PROCEDURE: 24 pigs were allocated to 2 groups (12 pigs/group). Pigs in 1 group received daily oral administration of an Mcc24-producing E coli, whereas the other group received a non-Mcc24-producing E coli. All pigs were challenge exposed with Salmonella Typhimurium chi4232. A third group of 6 pigs received Mcc24-producing E coli and was challenge exposed with an Mcc24-sensitive, marA-deleted strain of Salmonella Typhimurium 4232. After challenge exposure, fecal samples from all pigs were cultured to detect shedding of Salmonella Typhimurium and Salmonella Typhimurium isolates were screened for resistance to ciprofloxacin. Fecal samples were collected throughout the study, and tissue samples were collected during necropsy. RESULTS: Differences in shedding of Salmonella Typhimurium were not detected between groups receiving Mcc24-producing or non-Mcc24-producing E coli. No significant differences were found in quantitative analysis between groups receiving Mcc24-producing and non-Mcc24-producing E coli. Evidence of mar activation was not detected. CONCLUSIONS AND CLINICAL RELEVANCE: Microcin-producing E coli did not exert an effect on shedding of SalmonellaTyphimurium or mar activation in pigs. It may be difficult or impractical to create the conditions required for Mcc24 to be an effective part of a food safety intervention to reduce shedding of Salmonella Typhimurium. 相似文献
999.
1000.
Smith GW Gehring R Riviere JE Yeatts JL Baynes RE 《Journal of the American Veterinary Medical Association》2004,224(11):1827-1830
OBJECTIVE: To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows. DESIGN: Prospective study. ANIMALS: 5 lactating dairy cows. PROCEDURE: After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination. RESULTS: Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 microg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE: Ceftiofur administered by the intramammary route as an extra-label treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times. 相似文献