全文获取类型
收费全文 | 95992篇 |
免费 | 4761篇 |
国内免费 | 326篇 |
专业分类
林业 | 3935篇 |
农学 | 2916篇 |
基础科学 | 723篇 |
11222篇 | |
综合类 | 19479篇 |
农作物 | 3772篇 |
水产渔业 | 3941篇 |
畜牧兽医 | 48242篇 |
园艺 | 1048篇 |
植物保护 | 5801篇 |
出版年
2018年 | 1239篇 |
2017年 | 1310篇 |
2016年 | 1224篇 |
2015年 | 1029篇 |
2014年 | 1263篇 |
2013年 | 3520篇 |
2012年 | 2365篇 |
2011年 | 2793篇 |
2010年 | 1857篇 |
2009年 | 1882篇 |
2008年 | 2741篇 |
2007年 | 2576篇 |
2006年 | 2478篇 |
2005年 | 2315篇 |
2004年 | 2193篇 |
2003年 | 2288篇 |
2002年 | 2142篇 |
2001年 | 2561篇 |
2000年 | 2559篇 |
1999年 | 2007篇 |
1997年 | 910篇 |
1995年 | 947篇 |
1994年 | 876篇 |
1992年 | 1869篇 |
1991年 | 2065篇 |
1990年 | 2044篇 |
1989年 | 2100篇 |
1988年 | 1961篇 |
1987年 | 1869篇 |
1986年 | 1936篇 |
1985年 | 1847篇 |
1984年 | 1535篇 |
1983年 | 1337篇 |
1982年 | 941篇 |
1981年 | 969篇 |
1980年 | 894篇 |
1979年 | 1598篇 |
1978年 | 1290篇 |
1977年 | 1122篇 |
1976年 | 1097篇 |
1975年 | 1193篇 |
1974年 | 1509篇 |
1973年 | 1465篇 |
1972年 | 1488篇 |
1971年 | 1357篇 |
1970年 | 1330篇 |
1969年 | 1233篇 |
1968年 | 1030篇 |
1967年 | 1154篇 |
1966年 | 987篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, India, during the wet seasons of 1992 and 1993 to study the effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two levels of N (100 and 200 kg ha−1 ) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and green manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha−1 (72 kg N) green manure) and a no N control. Nitrogen application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha−1 and of single fertilizer N at 200 kg N ha−1 recorded the maximum N uptake, increased the yield attributes such as number of panicles per unit area, weight per panicle, number of total and filled grains per panicle and test weight. At 200 kg N ha−1 full substitution of N by green manure reduced the grain yield but only partial substitution of N by green manure resulted in almost similar yield as single fertilizer N. Thus 200 kg N ha−1 applied in equal proportions of fertilizer and green manure N can be recommended for medium duration rice cultivars. 相似文献
102.
There is only limited information on sheep interferon available. Recent publications have reported on: 1. an interferon (IFN) alpha subtype, which is secreted by the fetal trophectoderm into the lumen of the uterus between the 10th and 21st day of gestation. It was therefore named ovine trophoblast protein (oTP-1), and is responsible for signalling pregnancy to the ewe via high affinity receptors in the endometrium. It is thought that oTP-1 acts by directly influencing prostaglandin metabolism. 2. the role of lentivirus-induced interferon (LV-IFN) in the pathogenesis of Maedi/Visna. The results indicate that LV-IFN limits viral replication and therefore contributes to virus persistence and is also responsible for a chronic inflammatory process. 3. the mitogen- or antigen-dependent induction of ovine interferon gamma (IFN gamma) and its characterization. 相似文献
103.
D R Van Pelt W E Wingfield 《Journal of the American Veterinary Medical Association》1992,200(12):1938-1944
The goal of advanced life support in CPR must be to restore and maintain respiratory and hemodynamic effectiveness, and to correct the underlying dysrhythmia. Optimal basic life-support techniques must be continued to meet these goals. Many drugs have been suggested in the treatment of cardiac arrest, but unfortunately, drug effects are inconsistent and resuscitation rates remain low. Epinephrine, atropine, lidocaine, bretylium, and naloxone remain important drugs for consideration in CPR in most animals with cardiac arrest. The best chance of survival remains in early recognition of animals susceptible to arrest and in treatment of the underlying cause. 相似文献
104.
105.
106.
Sugar beet mash silage (BMS) was offered in amounts up to 35% of DM to dairy cows as a component of a total-mixed-ration (TMR). Barley and molasses in the control ration were replaced by BMS half in ration BMS 1/2 and in total in ration BMS 1/1 on the basis of the calculated contents of net energy for lactation. Two trials were carried out. In trial I each ration was tested on parameters of rumen fermentation and digestibility of crude nutrients using 4 Holstein cows with rumen fistula. Chewing activity was tested on 2 Holstein cows for each ration. With the BMS rations the ruminal NH3 concentration was lower and the drop in pH was less than in the control ration. The pattern of volatile fatty acids in the rumen fluid from the BMS groups tended towards more propionic and butyric acid. The feeding of BMS showed no negative impact on chewing and rumination. Energy digestibility raised significantly from 59.8% in the control ration to 72.6% in the BMS 1/1 ration. In trial II the same rations were fed in a change-overdesign to a herd of 24 Holstein cows to test feed intake and animal performance. The results showed no significant effects of BMS rations on DM intake and milk production. The results of both trials indicate that even high amounts of cereals can be replaced by BMS without negative effects on rumen fermentation, milk yield and milk composition with slight drop in fat content. For a better handling of BMS, it is of advantage to include it in a TMR. 相似文献
107.
108.
109.
Use of mibolerone in wolves and in three Panthera species 总被引:1,自引:0,他引:1
H M Gardner W D Hueston E F Donovan 《Journal of the American Veterinary Medical Association》1985,187(11):1193-1194
110.
1. Brown egg layers were fed diets differing in oil content, oil source and linoleic acid concentration and the effect on performance from 22 to 69 weeks of age was studied.
2. The birds responded with an increasing mean egg weight up to a linoleic acid intake of 2.75 g/bird d.
3. Increasing the intake of readily absorbable oil without increasing linoleic acid concentration did not increase mean egg weight. 相似文献