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:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   12091篇
  免费   831篇
  国内免费   6篇
专业分类
林业   1605篇
农学   427篇
基础科学   42篇
  2656篇
综合类   747篇
农作物   497篇
水产渔业   788篇
畜牧兽医   4747篇
园艺   296篇
植物保护   1123篇
出版年
  2023年   101篇
  2022年   130篇
  2021年   235篇
  2020年   228篇
  2019年   154篇
  2018年   553篇
  2017年   533篇
  2016年   474篇
  2015年   385篇
  2014年   439篇
  2013年   672篇
  2012年   919篇
  2011年   836篇
  2010年   457篇
  2009年   351篇
  2008年   709篇
  2007年   674篇
  2006年   547篇
  2005年   574篇
  2004年   523篇
  2003年   480篇
  2002年   397篇
  2001年   285篇
  2000年   245篇
  1999年   220篇
  1998年   69篇
  1997年   59篇
  1996年   42篇
  1995年   63篇
  1994年   39篇
  1993年   36篇
  1992年   82篇
  1991年   68篇
  1990年   65篇
  1989年   56篇
  1988年   62篇
  1987年   52篇
  1986年   52篇
  1985年   57篇
  1984年   47篇
  1983年   38篇
  1979年   42篇
  1974年   29篇
  1973年   29篇
  1948年   32篇
  1942年   50篇
  1941年   32篇
  1940年   36篇
  1939年   45篇
  1935年   37篇
排序方式： 共有10000条查询结果，搜索用时 312 毫秒
31.
  相似文献   
32.
Fine needle aspiration biopsy is a fast and inexpensive technique well tolerated by animals. Its efficacy for the diagnosis of malignancy and determination of cellular origin was investigated for 97 malignant tumors and five benign lesions in 83 dogs and 19 cats. Histological examination of the lesions was performed in each case. Malignancy was detected by cytology in 69% of the malignant tumors. The cellular origin of the lesion was determined in 74% of the cases. Confirmation of malignancy and determination of cellular origin permitted an early diagnosis and prognosis. Since fine needle aspiration biopsy and cytology cannot definitely rule out malignancy, a surgical biopsy and histopathology should be done when malignancy is suspected clinically and not confirmed cytologically. Specimens of good quality, adequate collaboration between the cytologist and clinicians, and sufficient knowledge of pathology and cytology are basic requirements for obtaining good results with fine needle aspiration biopsy and cytology.  相似文献   
33.
A transitional cell carcinoma of the urinary bladder was found in a beluga whale stranded in the St. Lawrence middle estuary. Various organs of this animal were submitted to high resolution gas chromatography coupled with mass spectrometry analysis. High frequency of urinary bladder cancer in the human population of the same area and the presence of carcinogenic compounds in the marine environment of this animal are discussed.

Concurrent isolation of Edwardsiella tarda from various organs of this whale is also reported.

  相似文献   
34.
  相似文献   
35.
  相似文献   
36.
An in-office allergy screening kit was evaluated in 10 dogs that had no clinical signs of atopy but had various intestinal parasites. All 10 dogs had a positive reaction to the dust mite Dermatophagoïdes farinae, and four dogs had positive reactions to at least one other group of allergens. The kit as presently marketed gives numerous false positive results in parasitized nonatopic dogs.  相似文献   
37.
  相似文献   
38.
Two strains of bovine Theileria from northern Nigeria were shown to be identical to Theileria mutans in the indirect immunofluorescent antibody test. One of the strains was transmitted by the tick Amblyomma variegatum; large macroschizonts, typical for T mutans, could be demonstrated in infected cattle. It is concluded from these experiments and from the literature that there is reliable evidence so far for the occurrence in Nigeria of only two bovine Tehileria species, T mutans and T velifera.  相似文献   
39.

A toxic nephrosis in calves treated with a drug containing tetracycline degradation products  相似文献   

40.
1. An experiment was done under commercial conditions to investigate the physiological effects of isolating broody turkey hens, for 72 h, in sand and wire floored pens on the third, 10th and 16th weeks of production.

2. Hens identified as broody and removed from the flock had higher plasma prolactin concentrations than the laying hens at each of the three experimental stages.

3. Confinement in sand and wire floored pens, induced a decline in plasma prolactin concentrations. This decline probably impeded immediate development of broody behaviour. Alternately, levels of prolactin higher than those of laying hens were again measured 7 and 14 days after treatment during third week but not after the 10 th and 16th week of production.

4. Confinement did not induce consistent changes in luteinising hormone (LH) and progesterone concentrations from one period to an other.

5. An increase in the plasma concentration of D‐(/?)‐hydroxybutyrate was observed in the hens which had an egg present in the oviduct on day 2, 3 and/or 4 of the treatment. Subsequently, a decrease in ovulation rate was observed in the hens with higher concentrations of D‐(β)‐hydroxybutyrate while under treatment, during the 10th week of production.

6. These data confirm that the effectiveness of the traditional methods for broodiness prevention under commercial conditions is related to the induction of a decrease of prolactin.  相似文献   

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