全文获取类型
收费全文 | 1283篇 |
免费 | 60篇 |
国内免费 | 15篇 |
专业分类
林业 | 143篇 |
农学 | 34篇 |
基础科学 | 4篇 |
202篇 | |
综合类 | 237篇 |
农作物 | 50篇 |
水产渔业 | 65篇 |
畜牧兽医 | 549篇 |
园艺 | 14篇 |
植物保护 | 60篇 |
出版年
2023年 | 12篇 |
2021年 | 21篇 |
2020年 | 21篇 |
2019年 | 18篇 |
2018年 | 19篇 |
2017年 | 27篇 |
2016年 | 33篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 48篇 |
2012年 | 51篇 |
2011年 | 51篇 |
2010年 | 49篇 |
2009年 | 41篇 |
2008年 | 56篇 |
2007年 | 49篇 |
2006年 | 43篇 |
2005年 | 44篇 |
2004年 | 43篇 |
2003年 | 45篇 |
2002年 | 20篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1994年 | 16篇 |
1992年 | 21篇 |
1991年 | 32篇 |
1990年 | 18篇 |
1989年 | 31篇 |
1988年 | 12篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1982年 | 9篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1976年 | 9篇 |
1974年 | 15篇 |
1973年 | 11篇 |
1972年 | 14篇 |
1970年 | 20篇 |
1969年 | 11篇 |
1968年 | 14篇 |
1967年 | 21篇 |
1966年 | 9篇 |
排序方式: 共有1358条查询结果,搜索用时 15 毫秒
31.
R Kasimanickam S Schroeder M Assay V Kasimanickam DA Moore JM Gay WD Whittier 《Reproduction in domestic animals》2014,49(5):775-782
The objectives were (i) to evaluate the effect of temperament, determined by modified 2‐point chute exit and gait score, on artificial insemination (AI) pregnancy rates in beef heifers following fixed time AI and (ii) to determine the effect of temperament on cortisol, substance‐P, prolactin and progesterone at initiation of synchronization and at the time of AI. Angus beef heifers (n = 967) at eight locations were included in this study. At the initiation of synchronization (Day 0 = initiation of synchronization), all heifers received a body condition score (BCS), and temperament score (0 = calm; slow exit and walk or 1 = excitable; fast exit or jump or trot or run). Blood samples were collected from a sub‐population of heifers (n = 86) at both synchronization initiation and the time of AI to determine the differences in serum progesterone, cortisol, prolactin and substance‐P concentrations between temperament groups. Heifers were synchronized with 5‐day CO‐Synch+ controlled internal drug release (CIDR) protocol and were inseminated at 56 h after CIDR removal. Heifers were examined for pregnancy by ultrasound 70 days after AI to determine AI pregnancy. Controlling for synchronization treatment (p = 0.03), facility design (p = 0.05), and cattle handling facility design by temperament score interaction (p = 0.02), the AI pregnancy differed between heifers with excitable and calm temperament (51.9% vs 60.3%; p = 0.01). The alley‐way with acute bends and turns, and long straight alley‐way had lower AI pregnancy rate than did the semicircular alley‐way (53.5%, 56.3% and 67.0% respectively; p = 0.05). The serum hormone concentrations differed significantly between different types of cattle handling facility (p < 0.05). The cattle handling facility design by temperament group interactions significantly influenced progesterone (p = 0.01), cortisol (p = 0.01), prolactin (p = 0.02) and substance‐P (p = 0.04) both at the initiation of synchronization and at the time of AI. Inter‐ and intra‐rater agreement for temperament scoring were moderate and good (Kappa = 0.596 ± 0.07 and 0.797 ± 0.11) respectively. The predictive value for calm and pregnant to AI was 0.87, and excited and non‐pregnant to AI was 0.76. In conclusion, the modified 2‐point temperament scoring method can be used to identify heifers with excitable temperament. Heifers with excitable temperament had lower AI pregnancy. Further, cattle handling facility design influenced the temperament and AI pregnancy. 相似文献
32.
As a result of the high lability and slow growth of Campylobacter fetus subspecies, the laboratory diagnosis of bovine genital campylobacteriosis has always been difficult. This is especially true under South African conditions, where farms are far apart, laboratories are only present in major centres and there are high ambient temperatures. In order to overcome the shortcomings associated with traditional diagnostic methods, the implementation of a molecular assay was sought. This work describes how a previously published PCR assay (MG3F/ MG4R primers) was adapted, optimised and applied in the diagnostic laboratory to test preputial samples directly for the presence of Campylobacter fetus. Field evaluation of the assay revealed an analytical sensitivity and specificity of 85.7% and 99%, respectively. Subsequent genotyping and phenotyping of a diverse collection of South African field isolates revealed that South Africa has an unexpected and previously unreported high incidence of Campylobacter fetus subsp. venerealis biovar intermedius strains. These strains were not identified correctly by the subspecies-specific primer set evaluated. Until such time that cost- effective genotyping methods are available to diagnostic laboratories in South Africa, and other countries with these atypical Campylobacter fetus subsp. venerealis strains, the need for bacterial culture will persist. Identification to subspecies level of isolates at present remains dependent upon a single phenotypic criterion, namely tolerance to 1% glycine. 相似文献
33.
34.
A total of 272 Cotswold pigs (17 +/- 1 d) were utilized in three experiments to evaluate the nutritive value of spray-dried egg proteins for early-weaned pigs. In all experiments, pigs were stratified by sex and initial BW and then assigned randomly to experimental diets. In Exp. 1, four corn-soybean meal-based diets containing 7% of either spray-dried porcine plasma (SDPP), spray-dried technical albumen (SDTA), SDTA stored at 70 degrees C for 3 d (SDTA-ht), or spray-dried whole egg (SDWE) were assigned to five pens each with four pigs for a 3-wk study period. Average daily gain, ADFI, and gain:feed ratio (G:F) were determined. At the end of wk 3, five pigs per treatment were killed to determine ileal AA and energy digestibilities, as well as Enterobacteriaceae counts. Compared with the SDPP diet, ADG and G:F were lower (P < 0.05) for SDTA-, SDTA-ht- and SDWE-containing diets. Apparent ileal digestibilities of cystine, histidine, isoleucine, methionine, and threonine in the SDPP diet were lower (P < 0.05) than in diets containing spray-dried egg products. Ileal digestible energy content did not differ (P > 0.05) in all diets (3.1 to 3.2 Mcal/kg). Enterobacteriaceae counts were lower in the SDTA-ht diet than in either the SDTA or SDWE diets (P < 0.05). In Exp. 2, the effect of substituting SDPP with varying levels of SDTA was investigated. Diets were randomly assigned to five pens (except for the 100% SDTA diet, which had four pens), each with four pigs. Average daily gain, ADFI, and G:F decreased linearly as the level of SDTA was increased in the diet (P < 0.05). Replacing SDPP with SDTA at 25 or 50% had no effect on pig performance (P > 0.10). In Exp. 3, phase I diets containing 0, 25, or 50% SDTA in place of SDPP (7% of the diet) were each assigned at random to eight pens each with four pigs for a 14-d period, after which all pigs were switched to a common phase II diet lacking both SDPP and SDTA for another 14 d. Average daily feed intake and ADG did not differ among all diets in phase I and II and overall (d 0 to 28). Pigs fed the diet containing 50% SDTA in phase I had lower (P < 0.05) G:F than those fed the SDPP diet. The results indicate that technical albumen can replace 25 to 50% of SDPP in early-weaned pig diets without compromising performance, and further suggest that heat-treated SDTA may affect intestinal microbial population in pigs. 相似文献
35.
36.
Schmidt WD 《DTW. Deutsche tier?rztliche Wochenschrift》2003,110(5):210-212
The expert group of the German Veterinary Chamber has established a frame-work of basic knowledge for education and examination of normal dog owners together with other groups. The most important topics of the theoretical part are: Ethology (social-behaviour, communication dog-human and dog-dog, education, dog-training, learning, psychology, fear, aggression), keeping and caring (prevention, first aid, handling), nutrition and health (diets, vaccination, parasites, diseases), breeding (sexual differences, knowledge about dog-breeds and their needs), dogs in public and family (laws, interaction, obedience, control. The practical part concentrates on the ability of the owner to influence and control his dog, practical handling and the dogs' obedience. Minimum age of owners is 18 years, the dog should be between 18 and 24 months old. The owner has to pass the theoretical exam only once in his/her life, the practical-part has to be repeated with every new dog older than 18 months. 相似文献
37.
There are very few resistance records on cattle nematodes. South American successive records have been increasing rapidly since the year 2000. In Argentina, increasing dissatisfaction based on the exclusive use of macrocyclic lactones has prompted the use of benzimidazoles in the Pampean region. The studied farm is located in the Argentina humid Pampas and had apparently poor results after anthelmintic treatments. Evaluation of resistance was firstly based on faecal egg reduction after treatment in November 2001 and June 2002 and was complemented with worm counts obtained by necropsy in June 2002. The study reports that the reduction of faecal egg excretion after benzimidazole (reduction 31-79%) or ivermectin treatments (76-97%) in November 2001 was insufficient and these poor results were confirmed in June 2002 (benzimidazoles (65-89%) and ivermectin (47-77%)). Several methods for evaluating faecal egg count reduction were performed and yielded different results. A new method based on the estimated faecal egg counts (corrected from the initial faecal egg counts and animal type using a general linear model) was used and gave higher flexibility in the interpretation of putative resistance to anthelmintics. From necropsy results, it could be concluded that Cooperia oncophora was resistant to avermectins and benzimidazoles and that Cooperia punctata, Ostertagia ostertagi and Haemonchus placei were resistant to benzimidazoles. This case of multispecies and multidrug resistance is probably not unique and could reflect the emergence of resistances in Argentina. This emergence is probably due to the intensive use of anthelmintics, the absence of refugia, and the frequent circulation of infected cattle. 相似文献
38.
Thirty canine urinary calculi, most of which had been qualitatively classified as struvite calculi, were analyzed by instrumental neutron activation analysis at the University of Missouri Research Reactor. Measurements of sodium, magnesium, aluminum, silicon, phosphorus, chloride, potassium, and calcium were possible, using a dual irradiation procedure. Magnesium was used to calculate the percentage of struvite mineral, Mg(NH4) (PO4) X 6H2O, in the calculi by making use of the stoichiometric relationship of the element magnesium to the mineral. For those calculi containing greater than 80% struvite, the mean elemental concentrations were found to be 0.12% Na, 9.35% Mg, 0.0033% Al, 12.1% P, 0.02% Cl, 0.85% K, and 2.05% Ca. A new method for determination of silicon in urinary calculi also was discussed. Two calculi were found to contain 45.0% and 37.3% silicon, and 1 mixed calculus was composed of 1.4% silicon. 相似文献
39.
40.
Interaction of chlorhexidine with trisEDTA or miconazole in vitro against canine meticillin‐resistant and ‐susceptible Staphylococcus pseudintermedius isolates from two UK regions 下载免费PDF全文