首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   109844篇
  免费   5583篇
  国内免费   66篇
林业   4642篇
农学   3198篇
基础科学   762篇
  12210篇
综合类   21123篇
农作物   4473篇
水产渔业   4781篇
畜牧兽医   56671篇
园艺   1229篇
植物保护   6404篇
  2018年   1250篇
  2017年   1405篇
  2016年   1348篇
  2015年   1132篇
  2014年   1330篇
  2013年   4100篇
  2012年   2674篇
  2011年   3319篇
  2010年   2161篇
  2009年   2150篇
  2008年   3373篇
  2007年   3097篇
  2006年   2938篇
  2005年   2805篇
  2004年   2885篇
  2003年   2815篇
  2002年   2753篇
  2001年   3412篇
  2000年   3438篇
  1999年   2573篇
  1998年   1111篇
  1997年   1136篇
  1995年   1292篇
  1994年   1202篇
  1993年   1170篇
  1992年   2460篇
  1991年   2634篇
  1990年   2542篇
  1989年   2601篇
  1988年   2352篇
  1987年   2437篇
  1986年   2560篇
  1985年   2469篇
  1984年   1992篇
  1983年   1824篇
  1982年   1192篇
  1981年   1152篇
  1980年   1050篇
  1979年   1827篇
  1978年   1476篇
  1977年   1204篇
  1976年   1166篇
  1975年   1226篇
  1974年   1590篇
  1973年   1667篇
  1972年   1648篇
  1971年   1564篇
  1970年   1462篇
  1969年   1301篇
  1967年   1117篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
1. The feeding value of new low β‐N‐oxalyl‐amino‐L‐alanine (BOAA) lines of Lathyrus sativus (lathyrus) and the benefits of dehulling the seed or of pre‐adapting chicks to lathyrus‐based diets were examined in several experiments.

2. Chicks fed on diets containing 400 g/kg of the low (1.3 g BOAA/kg seed) and medium (2.2 g BOAA/kg seed) BOAA lines did not differ (P>0.05) in weight gain (WG) or in apparent fat and protein digestibilities compared to birds fed on a wheat‐based diet.

3. Consumption of 600 g low BOAA lathyrus/kg diet caused a slight, but significant (P< 0.05), decrease in WG. Food efficiency decreased as the amount of dietary lathyrus was increased, suggesting that lathyrus may contain an antinutritive factor(s) other than BOAA.

4. Removal of the hull (70 g hull/kg seed) from the seed did not affect chick performance (P> 0.05).

5. Pre‐adapting chicks for 7 d to diets containing up to 600 g medium line lathyrus/kg diet did not reduce the detrimental effects of the lathyrus.

6. Although dehulling and pre‐adaptation of chicks to lathyrus were not beneficial, the low and medium lines of lathyrus tested show potential for use in chick diets up to at least 400 g lathyrus/kg diet.  相似文献   

152.
The experiment was conducted on 364 male Wistar rats of which 74 were included into the "zero" group and the remaining 290 were divided into 5 experimental groups, corresponding to the dietary protein levels of 4, 5, 10, 15 and 20%. The protein source in the diet was skim milk powder. The animals were fed individually and ad libitum. The experiment was performed between the 21 and 66 days of life of the rats and during this period, the animals in each group were successively killed to determine the nitrogen content in the body. Between the N content in the body and the body mass of rats from "zero" group, the relationship N0/W0 was determined. In each experimental group, two relationships were determined: --final nitrogen against final body mass--Nf/Wf --gain of nitrogen against gain of body mass--delta N/delta W. The derivatives of both functions were used for calculation of the daily gains of nitrogen (delta Nd) 1. According to the relationship Nf/Wf there was a similar significant increase of nitrogen content in the body in all groups with increasing the body mass, according to bc = 1.0413. The percentage of nitrogen in the body increased significantly only at dietary protein levels over 10%. 2. The rate of nitrogen gain in the gain of body mass according to delta N magnitude of was relatively constant in all groups (bc = 1). Thus, N-% in delta W was also relatively constant. N-% in the body gain increased significantly only at dietary protein levels over 10%. 3. Differences in the gains of nitrogen, as calculated by the derivative dNf/dWf and by d delta N/d delta W, showed in the first line in low-protein groups (on 4 and 5% protein) due to the error of estimation of the initial-N according to the equation N0 magnitude of W0. The mean relative error of estimation the initial-N was +/- 3% but in groups on 4 and 5% protein it charged the gain of N with 9-12% in spite of excluding from the relationship delta N magnitude of delta W rats with delta W less than 10 g. 4. Only when delta N greater than or equal to 1.3 g and delta W greater than or equal to 43, the error of estimation of delta N, did not exceed 3%.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
153.
154.
155.
156.
157.
Bacterial isolations were reviewed from equine trachea, guttural pouch, uterus, wounds, abscesses, blood, synovial fluid, and abdominal fluid submitted to the Clinical Bacteriology Laboratory of the School of Veterinary Medicine at the University of Montreal for aerobic bacterial culture from 1986 to 1988. Of the 733 samples submitted, 324 (44%) were positive for bacterial growth, and 233 antimicrobial sensitivity tests were performed. Seventy-six percent of all positive samples yielded one bacterial species and two were isolated from 22% of positive samples. Streptococcus zooepidemicus, Escherichia coli, and Actinobacillus spp. were isolated from 39%, 18%, and 15% of the samples, respectively.

Bacterial growth was most common from guttural pouches, wounds and abscesses, and transtracheal washes (TTW), but was less common from uterus, blood, abdominal fluid, and synovial fluids. Streptococcus zooepidemicus was the most common bacterium recovered from guttural pouches, TTW, uterus, and wounds and abscesses. Escherichia coli predominated in abdominal fluids, blood, and synovia. Bacterial sensitivities to common antimicrobials are presented.

  相似文献   
158.
Six Friesian calves from a pedigree herd died or were killed within 1 week of birth because of progressive central nervous disease in which the only consistent lesion was cerebral oedema. The cause was citrullinaemia, resulting from an autosomally inherited dysfunction of the urea cycle enzyme arginosuccinate synthetase. Citrullinaemia was diagnosed by demonstrating markedly elevated concentrations of citrulline in the blood of one calf and in the cerebral spinal fluid of another. One of two sires used in the herd was a heterozygous carrier of the disease. Heterozygocity was demonstrated using a polymerase chain reaction/restriction endonuclease test designed to detect the genetic mutation that causes citrullinaemia in cattle.  相似文献   
159.
160.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号