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   17343篇
  免费   921篇
  国内免费   17篇
林业   878篇
农学   558篇
基础科学   124篇
  2551篇
综合类   2666篇
农作物   931篇
水产渔业   988篇
畜牧兽医   8414篇
园艺   228篇
植物保护   943篇
  2021年   164篇
  2020年   168篇
  2019年   189篇
  2018年   336篇
  2017年   385篇
  2016年   280篇
  2015年   211篇
  2014年   328篇
  2013年   695篇
  2012年   509篇
  2011年   648篇
  2010年   443篇
  2009年   426篇
  2008年   649篇
  2007年   565篇
  2006年   522篇
  2005年   467篇
  2004年   429篇
  2003年   440篇
  2002年   381篇
  2001年   492篇
  2000年   477篇
  1999年   373篇
  1998年   180篇
  1997年   202篇
  1996年   156篇
  1995年   192篇
  1993年   164篇
  1992年   280篇
  1991年   314篇
  1990年   307篇
  1989年   312篇
  1988年   289篇
  1987年   246篇
  1986年   295篇
  1985年   253篇
  1984年   209篇
  1983年   207篇
  1979年   250篇
  1978年   165篇
  1975年   171篇
  1974年   234篇
  1973年   215篇
  1972年   251篇
  1971年   230篇
  1970年   203篇
  1969年   192篇
  1968年   158篇
  1967年   160篇
  1966年   161篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
26.
This review describes the advantages and disadvantages of radiography, ultrasonography, and nuclear medicine in the 2 most frequent thyroid pathologies of the dog: acquired primary hypothyroidism and thyroid neoplasia. Ultrasonography and scintigraphy remain the 2 most indicated imaging modalities for these thyroid abnormalities. However, as in human medicine, computed tomography and magnetic resonance imaging also have potential indications. This is especially the case in the evaluation of the extent, local invasiveness, and local or distant metastases of thyroid neoplasia. Based on experience with different imaging modalities in people, we suggest future directions in the imaging of the canine thyroid gland.  相似文献   
27.
The surgical success of laparoscopic castration without orchidectomy results from avascular necrosis of the testes. However, failures and subsequent production of testosterone and stallion‐like behaviour have been previously identified. Laparoscopic castration without removal of the testes was performed in 32 horses with 2 normal descended scrotal testes between July 2006 and October 2012. The objectives of our study were to evaluate the success rate of laparoscopic castration without orchidectomy on descended testes in our population and assess complications and recovery time. Endocrine tests were performed after surgery and owners also asked to report on their horse's behaviour and ability to resume exercise. Castration was deemed successful if endocrine test results were in accordance with gelding values. Failed horses were castrated using a conventional technique and histology performed when possible. Basal testosterone levels decreased below 3 nmol/l after surgery in 30/32 cases. However, in 2 horses, stallion behaviour persisted and histological evaluation after inguinal castration showed residual viable tissue. Two horses maintained high testosterone levels after surgery associated with stallion‐like behaviour. Based on these results, 12.5% of horses (4/32 horses) failed to be considered a gelding based on either endocrine tests and/or histology. All horses, with one exception, were able to resume exercise less than a week after the procedure. Laparoscopic castration without orchidectomy appears to be a safe procedure. When assessing the success of laparoscopic castration, our total failure rate was 12.5% (4/32 horses) which is significantly higher than previously reported.  相似文献   
28.
29.
Three experiments have been conducted to study the effect of virginiamycin in young grazing-bulls (Experiment 1) and heifers (Experiments 2 and 3). Rotational grazing on permanent grassland was practised and animals were supplemented with 1 kg dried sugarbeet pulp per head daily. Control groups did not receive virginiamycin via the supplement, while it was incorporated at 120, 300 and 200 mg kg−1 for the treatment groups in Experiments 1 to 3 respectively.
Average daily liveweight gain was significantly increased from 0·59 to 0·72 kg in Experiment 1 and from 0·73 to 0·81 kg in Experiment 3, but was not affected in Experiment 2 (0·51 vs 0·55 kg). Virginiamycin also increased liveweight gain per ha by 12, 7 and 13%, respectively, for the three experiments. Grazed area per animal was not enlarged to the same extent as the calculated daily energy allowances, which may suggest an improved digestibility and/or rumen fermentation.  相似文献   
30.
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