全文获取类型
收费全文 | 92178篇 |
免费 | 3332篇 |
国内免费 | 38篇 |
专业分类
林业 | 3742篇 |
农学 | 3463篇 |
基础科学 | 661篇 |
11301篇 | |
综合类 | 13534篇 |
农作物 | 3367篇 |
水产渔业 | 4967篇 |
畜牧兽医 | 47713篇 |
园艺 | 1166篇 |
植物保护 | 5634篇 |
出版年
2020年 | 774篇 |
2019年 | 982篇 |
2018年 | 1582篇 |
2017年 | 1848篇 |
2016年 | 1674篇 |
2015年 | 1404篇 |
2014年 | 1718篇 |
2013年 | 3717篇 |
2012年 | 2928篇 |
2011年 | 3587篇 |
2010年 | 2339篇 |
2009年 | 2329篇 |
2008年 | 3471篇 |
2007年 | 3209篇 |
2006年 | 3137篇 |
2005年 | 2668篇 |
2004年 | 2575篇 |
2003年 | 2592篇 |
2002年 | 2373篇 |
2001年 | 3389篇 |
2000年 | 3304篇 |
1999年 | 2553篇 |
1998年 | 983篇 |
1997年 | 1051篇 |
1996年 | 883篇 |
1995年 | 1022篇 |
1994年 | 895篇 |
1993年 | 896篇 |
1992年 | 1845篇 |
1991年 | 1920篇 |
1990年 | 1856篇 |
1989年 | 1858篇 |
1988年 | 1607篇 |
1987年 | 1594篇 |
1986年 | 1627篇 |
1985年 | 1528篇 |
1984年 | 1226篇 |
1983年 | 1032篇 |
1982年 | 713篇 |
1979年 | 1060篇 |
1978年 | 816篇 |
1975年 | 815篇 |
1974年 | 897篇 |
1973年 | 864篇 |
1972年 | 806篇 |
1971年 | 795篇 |
1970年 | 801篇 |
1969年 | 780篇 |
1968年 | 708篇 |
1967年 | 734篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
T. S. G. A. M. van den Ingh J. Rothuizen W. E. van den Brom 《The Veterinary quarterly》2013,33(2):150-157
Summary The clinical and pathological features of extrahepatic cholestasis in 19 dogs are presented. The condition was most often caused by partial or complete occlusion of the choledochal duct due to neoplastic diseases (12 cases), inflammatory processes (3 cases), or eventration and incarceration of the liver (I case). In only three cases was the condition due to intraluminal obstruction of the choledochal duct. The anamnestic, laboratory and pathological parameters of these 19 dogs were compared with the findings in 21 dogs with intrahepatic cholestasis. Statistical analysis of these parameters indicated that the presence of acholic faeces, the degree of icterus and the level of plasma γGT where the only parameters of value in the clinical differentation of extrahepatic from intrahepatic cholestasis. Histological examination of liver biopsies is a simple aid to a confident in vivo diagnosis of extrahepatic cholestasis. 相似文献
993.
994.
Antimicrobial susceptibility and serotypes of Actinobacillus (Haemophilus) pleuropneumoniae recovered from Missouri swine 总被引:4,自引:0,他引:4
W H Fales L G Morehouse K R Mittal C Bean-Knudsen S L Nelson L D Kintner J R Turk M A Turk T P Brown D P Shaw 《Journal of veterinary diagnostic investigation》1989,1(1):16-19
The antimicrobial susceptibility of 73 Actinobacillus (Haemophilus) pleuropneumoniae isolates from swine in Missouri was determined with a microdilution minimal inhibitory concentration test system. Serotyping was accomplished by means of co-agglutination. Serotype 1 (39/73) and serotype 5 (30/73) were commonly found, whereas serotype 7 (4/73) was infrequently encountered. Most isolates (MIC90) were found susceptible to ampicillin (amoxicillin), cephalothin, penicillin, erythromycin, gentamicin, and kanamycin. Marked resistance was found with oxytetracycline, tylosin, and sulfadimethoxine. The data indicate that use of ampicillin (amoxicillin) or penicillin may correlate well with the favorable outcome of treatment. 相似文献
995.
996.
H Ohashi S Komori S C Kwon T Unno 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(1):17-28
Effects of neurotensin (NT) applied via the blood vessel on the responses to stimulation of Remak's nerve (RNS) were investigated in the chicken isolated and perfused rectums. NT (5 ng-2 micrograms/ml) produced a concentration-dependent inhibition of the constituent contraction but not relaxation of the responses to RNS. In addition, high concentrations of NT (over 80 ng/ml) produced a contraction of the rectal muscle. Propranolol, a beta-adrenoceptor blocking agent, and guanethidine, an adrenergic neurone blocking agent, were able to reduce the inhibitory effect of NT on the response to RNS while potentiating the contractile effect of NT on the rectal muscle. NT (0.1 and 1 microgram/ml), like norepinephrine, decreased the flow rate of perfusate from the isolated rectum which was perfused at a constant pressure. Guanethidine enhanced norepinephrine-induced vasoconstriction, and phentolamine, an alpha-adrenoceptor blocking agent, plus propranolol was able to abolish it. Either of these prior applications resulted in a small but significant reduction of NT-induced vasoconstriction. These findings suggest that NT in plasma may function as a circulating hormone to exhibit an inhibitory action on the excitatory neural input to the rectum in the chicken, and that catecholamine release from adrenergic nerve terminals by NT may account for some but not all of the activity. 相似文献
997.
Clinical and laboratory findings in cats infected with feline immunodeficiency virus 总被引:9,自引:0,他引:9
C D Hopper A H Sparkes T J Gruffydd-Jones S M Crispin P Muir D A Harbour C R Stokes 《The Veterinary record》1989,125(13):341-346
Thirty-two cats referred to the Feline Studies Centre between June 1987 and October 1988, and 14 in-contact cats, were found to be infected with feline immunodeficiency virus. Most of the 46 cats were non-pedigree and free ranging; 27 were male (19 neutered) and 19 were female (18 neutered). Their ages ranged from one to 17 years and the average age was 5.8 years. The most common clinical signs were lethargy, inappetence, weight loss, pyrexia and lymphadenopathy; most cases had multiple abnormalities. Other common signs were gingivitis, diarrhoea, rhinitis and ocular discharge. Eight cats had neoplasia. The commonest haematological abnormalities were anaemia, neutropenia, lymphopenia and monocytosis. Eight cats had lymphocytosis; seven of these were in a single house-hold. Several cats had high serum globulin levels and half of those tested had high IgG levels. Seven cats had no detectable antibody to feline immunodeficiency virus even though the virus was cultured from the peripheral blood lymphocytes. During follow-up for up to 60 weeks one cat died and 23 were destroyed on humane grounds. 相似文献
998.
Two groups of parasite-free calves, one of which had been treated with four doses of a homoeopathic oral vaccine for parasitic bronchitis due to Dictyocaulus viviparus and the other with a placebo, were infected at the rate of 25 infective larvae/kg bodyweight 18 days after the final dose. Both groups became severely affected by parasitic bronchitis, with clinical signs starting 13 days after infection. There were no discernible differences between the treated and control groups in their manifestations of resistance to D viviparus or their clinical responses to the disease produced. 相似文献
999.
R. A. Read W. T. Reynolds D. J. Griffiths † J. S. Reilly 《Australian veterinary journal》1982,58(6):269-271
SUMMARY A case of vaginal prolapse in a South Australian Sea Lion is described. Conservative treatment proved unsuccessful, and an ovariohysterectomy was performed. Problems concerning anaesthesia, surgery and post-operative management of this marine species are discussed. 相似文献
1000.
Benefits of feeding pharmacological concentrations of zinc (Zn) provided by Zn oxide (ZnO) to 21-d conventionally weaned pigs in the nursery have been documented; however, several management questions remain. We conducted two experiments to evaluate the effect on growth from feeding 3,000 ppm Zn as ZnO during different weeks of the nursery period. In Exp. 1 (n = 138, 11.5 d of age, 3.8 kg BW) and Exp. 2 (n = 246, 24.5 d of age, 7.2 kg BW), pigs were fed either basal diets containing 100 ppm supplemental Zn (adequate) or the same diet with an additional 3,000 ppm Zn (high) supplied as ZnO. Pigs were fed four or two dietary phases in Exp. 1 and 2, respectively, that changed in dietary ingredients and nutrient content (lysine and crude protein) to meet the changing physiological needs of the pigs for the 28-d nursery period. Dietary Zn treatments were 1) adequate Zn fed wk 1 to 4, 2) high Zn fed wk 1, 3) high Zn fed wk 2, 4) high Zn fed wk 1 and 2, 5) high Zn fed wk 2 and 3, and 6) high Zn fed wk 1 to 4. In Exp. 1 and 2, pigs fed high Zn for wk 1 and 2 or the entire 28-d nursery period had the greatest (P < .05) ADG. During any week, pigs fed high Zn had greater concentrations of hepatic metallothionein and Zn in plasma, liver, and kidney than those pigs fed adequate Zn (P < .05). In summary, both early- and traditionally weaned pigs need to be fed pharmacological concentrations of Zn provided as ZnO for a minimum of 2 wk immediately after weaning to enhance growth. 相似文献