全文获取类型
收费全文 | 73303篇 |
免费 | 4133篇 |
国内免费 | 32篇 |
专业分类
林业 | 3175篇 |
农学 | 2397篇 |
基础科学 | 466篇 |
8668篇 | |
综合类 | 12016篇 |
农作物 | 2818篇 |
水产渔业 | 3523篇 |
畜牧兽医 | 38602篇 |
园艺 | 835篇 |
植物保护 | 4968篇 |
出版年
2018年 | 966篇 |
2017年 | 1074篇 |
2016年 | 1000篇 |
2015年 | 845篇 |
2014年 | 1047篇 |
2013年 | 2745篇 |
2012年 | 1944篇 |
2011年 | 2267篇 |
2010年 | 1533篇 |
2009年 | 1559篇 |
2008年 | 2322篇 |
2007年 | 2221篇 |
2006年 | 2035篇 |
2005年 | 1972篇 |
2004年 | 1847篇 |
2003年 | 1989篇 |
2002年 | 1806篇 |
2001年 | 2240篇 |
2000年 | 2191篇 |
1999年 | 1748篇 |
1998年 | 714篇 |
1997年 | 776篇 |
1996年 | 685篇 |
1995年 | 865篇 |
1994年 | 734篇 |
1993年 | 734篇 |
1992年 | 1493篇 |
1991年 | 1635篇 |
1990年 | 1602篇 |
1989年 | 1606篇 |
1988年 | 1495篇 |
1987年 | 1458篇 |
1986年 | 1536篇 |
1985年 | 1449篇 |
1984年 | 1271篇 |
1983年 | 1063篇 |
1982年 | 748篇 |
1979年 | 1171篇 |
1978年 | 887篇 |
1977年 | 840篇 |
1976年 | 799篇 |
1975年 | 829篇 |
1974年 | 1030篇 |
1973年 | 1070篇 |
1972年 | 1018篇 |
1971年 | 951篇 |
1970年 | 927篇 |
1969年 | 899篇 |
1968年 | 754篇 |
1967年 | 844篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
- An enzymatic ‘reaction rate’ micro-method for the rapid routine estimation of D-B-hydroxybutyrate (D-B-HOB) in ruminant plasma, using an I.L. Multistat III centrifugal analyzer, is described.
- Reaction conditions were optimized to give a linear response for plasma D-B-HOB concentrations between 100 and 2500 μmoles per litre, at 30°C and pH 9.0.
- For the standardized method the within-run and between-run coefficients of variation for deproteinised ovine plasma were consistently less than 3.5%.
- There was good agreement between plasma concentrations obtained by the present method and both original U.V. end-point technique (r=0.927b=0.950) and a colorimetric end-point procedure (r=0.937. b=0.879).
- Utreated ovine and bovine plasma consistently exhibited high ‘blank’ activity and this was directly correlated with plasma lactate dehydrogenase (LDH) activity in both species (r=0.971; p<0.001 and r=0.949; p<0.001 respectively). The distribution of LDH activity in man was similar to sheep but, contrastingly, non-specific interference was extremely low in human plasma and unrelated to LDH. Horse, chicken and rat had negligible ‘blank” activity and comparatively low LDH levels. In both cattle and sheep non-specific interference was abolished by perchloric acid precipitation. In the sheep subtraction of ‘blank’ activity gave D-H-HOB concentrations for untreated plasma comparable to those in deproteinised samples. However, in the bovine, D-B-HOB levels remained significantly (t=6.44; p<0.001) higher even after ‘blank’ correlation. In contrast to man and other non-ruminants, perchloric acid precipitation is essential in ruminants to avoid false overestimation of plasma D-B-HOB levels.
- Plasma with EDTA as anticoagulant and serum gave concentrations of D-B-HOB approximately 60% lower, than samples containing heparin or oxalate/fluoride. However, heparin was associated with much higher (up to 50%) non-specific NAD rduction than oxalate/fluoride.
- High levels of acetoacetate (400–1000 μmoles per litre) reduced the recovery of D-B-HOB from ovine plasma by less than 10%. This effect was negated by the inclusion of hydrazine hydrates in the reaction mixture. Perchlorate ion concentrations above 25 μmoles per litre per test dramatically inhibited the assay in ovine plasma, and therefore precipitation conditions must be carefully controlled.
- Plasma with oxalate/fluoride as anticoagulant showed the greatest stability in storage; 24 hours at room temperature, one week at +4°C and at least one month at ?20°C.
102.
Cysts found in the liver of a horse which had never been out of New Zealand were used to infect two dogs which were slaughtered 35 days after infection. Large numbers of Echinococcus granulosus were recovered. These cestodes were compared with mature dog-sheep cestodes, using light and scanning electron microscopy and identified as the dog-horse strain of E.granulosus. 相似文献
103.
Ginder GD 《Science (New York, N.Y.)》1985,228(4701):865-866
104.
105.
Wobeser G Gajadhar AA Hunt HM 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(8):241-244
Infection with Fascioloides magna, the large American liver fluke, was diagnosed in two moose (Alces alces) and six wapiti (Cervus elaphus) from central Saskatchewan. This is believed to be the first record of the parasite in the province. Fecal samples collected from wild wapiti at five sites in the commercial forest zone in Saskatchewan contained eggs believed to be those of F. magna. Trematode eggs were not found in feces from five captive herds of wapiti in the province, nor in samples from wild wapiti in Moose Mountain Provincial Park. Operculate eggs were found in feces of wild wapiti from Cypress Hills, but these were believed to be from trematodes other than F. magna. The distribution and significance of F. magna in Canada, based partially on responses to a mail questionnaire, are reviewed. 相似文献
106.
Harasen GL 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(6):193-194
Two cases of noninfectious, nonerosive arthritis are presented. The diagnostic features, clinical course and treatment are reviewed. Potential etiologies are discussed in the light of relatively little current material on this subject in the veterinary literature. 相似文献
107.
Blue MG 《New Zealand veterinary journal》1985,33(1-2):17-19
A developmental anomaly, resulting from partial segmental aplasia of the Mullerian ducts, was present in a Clydesdale mare. She had complete double cervices and a divided uterine body. In this mare, bilateral pregnancies were destroyed in sequence by squeezing them per rectum 25 and 29 days after insemination. 相似文献
108.
Ten out of eleven subcutaneous abscesses in cats harboured anaerobic bacteria. Seven of the ten abscesses contained a mixture of obligate anaerobes and facultative anaerobes or microaerophilic bacteria. All of the anaerobic isolates were sensitive to the antibiotic metronidazole, but were resistant to streptomycin. Three isolates from one abscess were resistant to penicillin and ampicillin. Clinical resolution of subcutaneous abscesses was poor when procaine penicillin was used alone as treatment. 相似文献
109.
110.