全文获取类型
收费全文 | 70867篇 |
免费 | 3965篇 |
国内免费 | 34篇 |
专业分类
林业 | 3224篇 |
农学 | 2529篇 |
基础科学 | 477篇 |
8696篇 | |
综合类 | 11415篇 |
农作物 | 2606篇 |
水产渔业 | 3640篇 |
畜牧兽医 | 36607篇 |
园艺 | 907篇 |
植物保护 | 4765篇 |
出版年
2018年 | 1053篇 |
2017年 | 1129篇 |
2016年 | 1056篇 |
2015年 | 907篇 |
2014年 | 1136篇 |
2013年 | 2628篇 |
2012年 | 2058篇 |
2011年 | 2461篇 |
2010年 | 1683篇 |
2009年 | 1751篇 |
2008年 | 2592篇 |
2007年 | 2362篇 |
2006年 | 2326篇 |
2005年 | 2124篇 |
2004年 | 2193篇 |
2003年 | 2165篇 |
2002年 | 2036篇 |
2001年 | 2366篇 |
2000年 | 2375篇 |
1999年 | 1925篇 |
1998年 | 912篇 |
1997年 | 821篇 |
1996年 | 782篇 |
1995年 | 861篇 |
1994年 | 843篇 |
1993年 | 767篇 |
1992年 | 1523篇 |
1991年 | 1542篇 |
1990年 | 1662篇 |
1989年 | 1507篇 |
1988年 | 1450篇 |
1987年 | 1340篇 |
1986年 | 1384篇 |
1985年 | 1336篇 |
1984年 | 1128篇 |
1983年 | 1025篇 |
1982年 | 628篇 |
1979年 | 1004篇 |
1978年 | 795篇 |
1977年 | 717篇 |
1976年 | 676篇 |
1975年 | 719篇 |
1974年 | 766篇 |
1973年 | 830篇 |
1972年 | 803篇 |
1971年 | 748篇 |
1970年 | 729篇 |
1969年 | 744篇 |
1967年 | 658篇 |
1966年 | 631篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
Capece BP Navarro M Arcalis T Castells G Toribio L Perez F Carretero A Ruberte J Arboix M Cristòfol C 《Veterinary journal (London, England : 1997)》2003,165(3):266-275
Three single oral doses (8.5, 10, and 14 mg/kg) of a racemic formulation of albendazole sulphoxide (ABZSO) were administered to pregnant rats on day 10 of gestation. Mother plasma and embryo concentrations of ABZSO enantiomers and albendazole sulphone (ABZSO(2)) were determined 9 h after administration. The (-)-ABZSO enantiomer showed higher peak concentrations in both maternal plasma and embryo than the (+) enantiomer. An increase in embryo concentrations of ABZSO enantiomers and ABZSO(2) was only observed when dose rose to 14 mg/kg. There was an increase in resorption when the dose increased, but significant differences were only found in the higher dose group when compared with the other groups. The incidence of external and skeletal malformations (mostly of the tail, vertebrae and ribs) rose significantly in the 10 mg/kg group, producing almost 20% and 90% of malformed fetuses, respectively, and gross external and skeletal abnormalities in the thoracic region and limbs were also found. 相似文献
942.
OBJECTIVE: To quantify the effect on gap stiffness and cranial to caudal bending stiffness of conversion of the 6 distal clamps of planar bilateral fixator models to sliding clamps and the effect of attachment of composite beams to the sliding clamp models. STUDY DESIGN: Mdash;Mechanical testing performed on models. SAMPLE POPULATION: Five models using birch dowels and a commercially available external skeletal fixator system. METHODS: A segmentally comminuted, middiaphyseal fracture was simulated with the use of wooden dowels, and a bilateral 6-pin fixator was applied to create each of 5 models. The models were mechanically tested with all fixed clamps, with the 6 distal clamps converted to sliding clamps and with composite beams attached to the sliding clamp models. Testing was carried out in axial loading with physiologically relevant loads for a canine model, and in bending in the cranial to caudal plane. RESULTS: Sliding clamp fixators with composite beams attached exhibited a nonlinear increase in axial loading gap stiffness as load increased. The composite beam group also exhibited an increase in cranial to caudal bending stiffness as compared with fixed clamp and sliding clamp models. CONCLUSIONS: Using composite beam elements, planar bilateral external fixators can be constructed such that the fracture site would undergo controlled amounts of displacement at low loads and lessening displacement at higher loads. CLINICAL RELEVANCE: The nonlinear stiffness profile attained by the addition of composite beam elements to a planar external fixator allows controlled axial micromotion at the fracture site. Because controlled axial micromotion appears to stimulate fracture healing, a nonlinear stiffness profile of this type should enhance fracture healing. 相似文献
943.
Radford AD Stockley P Taylor IR Turner R Gaskell CJ Kaney S Humphris G Magrath C 《The Veterinary record》2003,152(14):422-427
A course in communication skills has been developed specifically for veterinary students, based on those delivered at many medical schools, and making extensive use of professional actors as simulated clients. Its aim is to raise awareness of the importance of communication among veterinary undergraduates at all stages of the curriculum, and it allows them to role-play in acted-out scenarios. Facilitated small groups provide an environment in which students can receive feedback on their own performance and also give feedback to their colleagues. An independent evaluation suggests that the opportunity to role-play increased the students' confidence in communicating with others. They were able to identify their personal strengths as communicators and gain insights into the aspects of communication they could improve. Feedback and subsequent discussions were highly valued, with the actors playing a crucial role in providing feedback from the client's perspective. Students were able to use the knowledge they acquired when consulting with real clients. Most of the students suggested that the course should continue in its current format, but with more time provided for it in the curriculum. 相似文献
944.
945.
Jessica Fry Juan Pérez Casanova Lynn Lush Andy Walsh Cyr Couturier 《Journal of aquatic animal health》2015,27(1):57-64
The direct exposure of fish eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps, including safe contact times, exposure levels, and potential long-term effects on aquaculture species in both freshwater and seawater. The effect of different ozone (O3) doses (0.5–1.0, 1.5–2.0, and 2.5–3.0 mg of O3/L for 90 s) on recently fertilized eggs of Atlantic Cod Gadus morhua and eyed eggs of Atlantic Salmon Salmo salar and Rainbow Trout Oncorhynchus mykiss was evaluated in comparison with the effects of two commercial disinfectants: Perosan (0.004 mg/L) and Ovadine (100 mg/L). The impact of ozone application was evaluated based on hatching success, larval nucleic acid concentration, larval growth, and survival. Overall, results indicated that ozonation of Atlantic Cod eggs at a dose less than 3.0 mg/L for 90 s produced no negative effect on the larvae up to 30 d posthatch. Furthermore, ozonation of Atlantic Salmon and Rainbow Trout eggs generated no negative effect on the larvae, based on monitoring until 85% yolk sac re-absorption (16 d posthatch).
Received May 6, 2014; accepted October 24, 2014 相似文献
946.
Brunker JD Hoover JP 《The Canadian veterinary journal. La revue veterinaire canadienne》2007,48(3):292-295
A mixed breed dog treated for ehrlichiosis and systemic histoplasmosis developed a refractory thrombocytopenia. When an abdominal mass was detected, exploratory laparotomy and biopsies confirmed lymphoma, which on immunohistochemical stains was determined to be of B-cell origin. Conceivably, the B-cell lymphoma in this dog was associated with chronic inflammation from ehrlichiosis, histoplasmosis, or both. 相似文献
947.
García-Feliz C Collazos JA Carvajal A Vidal AB Aladueña A Ramiro R de la Fuente M Echeita MA Rubio P 《Zoonoses and public health》2007,54(8):294-300
The present study is the first conducted in Spain to estimate the bacteriological herd prevalence of Salmonella enterica in fattening units and to describe the Salmonella serovar diversity on these farms using a sample representative of the entire swine population. For this purpose, 10 faecal samples were collected from 10 different pens containing pigs close to market weight in a total of 232 fattening units. Total sample size was proportionally distributed according to the fattener census in each of the regions of the country and all the samples were examined by culture of 25 g of faecal material. One hundred (43.1%) farms had at least one Salmonella-positive sample (95% CI: 37-49.1%). Salmonella enterica was detected in 290 (12.5%) pooled faecal floor samples (95% CI: 11.2-13.8%). The apparent herd prevalence of salmonellosis was similar among multi-site, finishing and farrow to finish farms. Overall, 24 different serovars were identified, with S. Typhimurium, S. Rissen and S. Derby being the most common both at herd and sample level. Results of phage typing were available for the 91 isolates of S. Typhimurium. A total number of 10 different phage types were identified, with DT 193 being the most frequent. Phage types DT 104, DT 104b and DT U302, which have been associated with several multi-resistant patterns, accounted for 23% and 29% of the Typhimurium total isolates or Typhimurium infected farms respectively. 相似文献
948.
Territo PR Freise KJ Newhall K Barnhart SD Peters SC Engleking DR Burnett TJ Abdul-Karim B Shannon HE 《Journal of veterinary pharmacology and therapeutics》2007,30(6):508-515
The development and validation of the maximal electro-shock (MES) model using phenobarbital (Pb) as the positive control is described. This approach builds on previous work in rodent model systems, and has been adapted to dogs as a tool for pharmaceutical dose selection. Dogs, like rodents, exhibit generalized convulsions which manifest as progressive clinical signs in a dose (electrical current) dependent fashion. At the limit (300 mA, 200 msec) animals underwent clonic-tonic convulsions consistent with complete generalized (Grand Mal) seizures with a grade 3 clinical score (CS) and a menace response time of 98.5 +/- 24.4 sec (n = 8). Pretreatment of animals with Pb at 3, 10, and 30 mg/kg, in a 4-by-4 complete block crossover design (Latin-Square), resulted in a dose-dependant reduction in CS and menace response time. Estimates of plasma Pb concentration taken prior to MES induction showed a similar dose-dependent reduction in CS and menace response time with concentration. Using a cumulative logistic regression model, a predicted 50% probability of a CS = 1 was approximately 11.4 mg/kg. In addition, plasma Pb concentrations predicted a 50% probability of a CS = 1 occurs at plasma Pb concentration of approximately 16.0 mug/mL. Combined these data suggest that MES is a useful model for evaluating generalized convulsions in canines and may provide a tool for dose selection of novel pharmaceutical compounds. 相似文献
949.
JF Pycock S. Dieleman P. Drifjhout Y. van der Brug C. Oei GC van der Weijden 《Reproduction in domestic animals》1995,30(4):224-227
950.
Neutrophil mediated and IgA dependent antibacterial immunity against enteropathogenic Escherichia coli in the porcine intestinal mucosa 总被引:1,自引:0,他引:1
The role of polymorphonuclear neutrophils (PMN) in the antibacterial immunity against enteropathogenic Escherichia coli (EEC) 0:149 in the porcine intestine was studied using intestinal Thiry-Vella loop (T-V loop) as a model. Intraluminal immunizations of T-V loops resulted in elevated levels of immunoglobulin A (IgA) anti-EEC 0:149 antibody in the loop secretions, an infiltration of PMN in the lumen of the loops and an increase in the concentrations of lactoferrin (LF), lysozyme (LY), cationic proteins (CP), and a specific bactericidal response in the immunized loops. PMN were observed by electron microscopy (EM) to be actively phagocytic in the lumen of the immune loops. EM observations of loop fluids as well as the abrogating effect of iron on the in vivo bactericidal response strongly suggest that the pMN played an important role in the bactericidal response in the loops against EEC. In addition to phagocytosis by PMN and subsequent intracellular killing, disintegration of PMN in the lumen of the loops and extracellular killing of EEC by the antibacterial products of PMN such as LF, LY and CP, with and/or without synergistic effect of IgA antibodies, also contribute to the bactericidal response of the immunized loops. 相似文献