全文获取类型
收费全文 | 7573篇 |
免费 | 63篇 |
国内免费 | 14篇 |
专业分类
林业 | 727篇 |
农学 | 235篇 |
基础科学 | 49篇 |
935篇 | |
综合类 | 340篇 |
农作物 | 511篇 |
水产渔业 | 475篇 |
畜牧兽医 | 3666篇 |
园艺 | 198篇 |
植物保护 | 514篇 |
出版年
2020年 | 18篇 |
2019年 | 17篇 |
2018年 | 128篇 |
2017年 | 187篇 |
2016年 | 175篇 |
2015年 | 234篇 |
2014年 | 205篇 |
2013年 | 158篇 |
2012年 | 451篇 |
2011年 | 305篇 |
2010年 | 119篇 |
2009年 | 75篇 |
2008年 | 73篇 |
2007年 | 45篇 |
2006年 | 43篇 |
2005年 | 776篇 |
2004年 | 656篇 |
2003年 | 447篇 |
2002年 | 115篇 |
2001年 | 138篇 |
2000年 | 32篇 |
1999年 | 148篇 |
1992年 | 118篇 |
1991年 | 145篇 |
1990年 | 168篇 |
1989年 | 147篇 |
1988年 | 171篇 |
1987年 | 114篇 |
1986年 | 143篇 |
1985年 | 118篇 |
1984年 | 91篇 |
1983年 | 81篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 24篇 |
1979年 | 133篇 |
1978年 | 96篇 |
1977年 | 91篇 |
1976年 | 77篇 |
1975年 | 137篇 |
1974年 | 129篇 |
1973年 | 116篇 |
1972年 | 138篇 |
1971年 | 119篇 |
1970年 | 89篇 |
1969年 | 102篇 |
1968年 | 113篇 |
1967年 | 125篇 |
1966年 | 102篇 |
1965年 | 70篇 |
排序方式: 共有7650条查询结果,搜索用时 15 毫秒
71.
Jo?o A T Pigatto José L Laus Jaime M Santos Cristine Cerva Luciana S Cunha Valéria Ruoppolo Paulo S M Barros 《Journal of zoo and wildlife medicine》2005,36(4):702-705
The corneal endothelium is essential for the maintenance of the corneal transparency. The aim of this study was to examine the morphology of the endothelial surface and perform morphometric analysis of the normal corneal endothelial cells of the Magellanic penguin (Spheniscus magellanicus) using scanning electron microscopy. The present work demonstrates that the corneal endothelium of the Magellanic penguin is similar to those described in other vertebrates. 相似文献
72.
73.
74.
Regulation by gonadal steroids of estrogen and progesterone receptors along the reproductive tract in female lambs. 总被引:2,自引:0,他引:2
A Meikle EG Garófalo M Rodríguez-Pi?ón C Tasende L Sahlin 《Acta veterinaria Scandinavica》2001,42(1):161-169
The regulation of estrogen and progesterone receptor (ER, PR) expression by estradiol (E2) and progesterone (P4) in the oviduct, uterus and cervix of female lambs was studied. The animals received three intramuscular injections of E2, P4 or vehicle with an interval of 24 h and they were slaugthered 24 h after the third injection. Determinations of ER and PR were performed by binding assays and mRNAs of ER alpha and PR by solution hybridization. High levels of ER and PR in both cervix and oviduct were found in the female lamb, differing from other mammalian species. No significant effects by either E2 or P4 treatment on ER and PR levels in the cervix and oviduct could be observed. E2 treatment increased the mRNA levels of ERa and PR more than 3-fold in the cervix, while P4 treatment increased the mRNA levels of ERa and PR in the uterus. The results show differential effects of gonadal steroids on sex steroid receptor expression along the reproductive tract in female lambs, suggesting that steroid target tissues can modulate responses to the same circulating levels of steroid hormones. 相似文献
75.
W Erhardt C Ring H Kraft A Schmid H M Weinmann R Ebert B Schl?ger M Schindele R Heinze N Lomholt 《DTW. Deutsche tier?rztliche Wochenschrift》1989,96(3):92-99
For investigations of CO2-stunning of feeder- and slaughter-pigs parameters of behaviour, blood-gas-analyses and electroencephalograms were chosen. The following results were obtained: 1. Blood-gas-analyses proved that the CO2-stunning does not produce unconsciousness due to a lack of oxygen. 2. The criterias of general anaesthesia: unconsciousness, muscle-relaxation and analgesia with total reversibility could be confirmed. 3. The violent convulsive symptoms were evaluated as reactions identical with the stage II of GUEDEL's scheme of anaesthesia. 4. Muscular agitation, which sometimes appeared a few seconds before the stage of excitation, was judged to belong either to the start of the excitation phase or to the end of Guedel's stage of analgesia, during which the sensitivity is decreased. Neither study of behavior nor objective measurements showed, during the first 10 to 20 seconds of exposure to the CO2, any sign of pain or suffering related to the Act for Prevention of Cruelty to Animals, and accordingly such suffering should not be ascribed to the CO2 stunning method. 相似文献
76.
77.
78.
79.
80.