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   255篇
  免费   11篇
  国内免费   3篇
林业   35篇
农学   20篇
基础科学   3篇
  26篇
综合类   13篇
农作物   7篇
水产渔业   30篇
畜牧兽医   115篇
园艺   2篇
植物保护   18篇
  2023年   1篇
  2022年   4篇
  2021年   18篇
  2020年   7篇
  2019年   1篇
  2018年   11篇
  2017年   4篇
  2016年   9篇
  2015年   12篇
  2014年   21篇
  2013年   16篇
  2012年   15篇
  2011年   16篇
  2010年   7篇
  2009年   7篇
  2008年   20篇
  2007年   17篇
  2006年   18篇
  2005年   17篇
  2004年   11篇
  2003年   10篇
  2002年   10篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1985年   2篇
  1983年   1篇
  1978年   1篇
排序方式: 共有269条查询结果,搜索用时 15 毫秒
81.
The aim of the present study was to examine the production efficiency of cloned pigs by serial somatic cell nuclear transfer (SCNT) and to ascertain any changes in the telomere lengths of multiple generations of pigs. Using fetal fibroblasts as the starting nuclear donor cells, porcine salivary gland progenitor cells were collected from the resultant first-generation cloned pigs to successively produce second- and third-generation clones, with no significant differences in production efficiency, which ranged from 1.4% (2/140) to 3.3% (13/391) among the 3 generations. The average telomere lengths (terminal restriction fragment values) for the first, second and third generation clones were 16.3, 18.1 and 20.5 kb, respectively, and were comparable to those in age-matched controls. These findings suggest that third-generation cloned pigs can be produced by serial somatic cell cloning without compromising production efficiency and that the telomere lengths of cloned pigs from the first to third generations are normal.  相似文献   
82.
Serum alpha-fetoprotein (AFP) concentrations were measured before and after surgical removal of tumor masses in four dogs with hepatocellular carcinoma (HCC). Localization of AFP was also examined immunohistochemically in tumor tissues. In three cases, the serum AFP concentration was 10 to 20 times higher than that of normal dogs. One to two months after surgery, the serum AFP concentration had decreased to normal range. AFP was localized in the tumor tissues in these three cases. One case, which had a low serum AFP, did not show AFP localization in tumor tissue.  相似文献   
83.
Luteinizing hormone (LH)-stimulated steroidogenesis in luteal cells is known to be mediated through the activation of cyclic AMP (cAMP)-dependent protein kinase, and to be also modulated by calcium-dependent mechanisms. In the present study, we tested the hypothesis that LH stimulates progesterone (P4) production in bovine luteal cells through activation of phospholipase (PL) C by using a cell culture system. Bovine mid-luteal cells (Days 8-12 of the estrous cycle) were cultured for 24 h and then exposed to a PLC inhibitor (U-73122; 10 microM) with or without LH (10 ng/ml) for 4 h. U-73122 blocked LH-stimulated P4 production without affecting cAMP accumulation. Moreover, exposure of luteal cells to PLC increased P4 production in a dose-dependent manner. These results support the hypothesis that the luteotropic action of LH in bovine luteal cells is mediated not only by activation of adenylate cyclase but also by activation of PLC.  相似文献   
84.
85.
86.
87.
Oligodendroglioma is a rare tumor originating from oligodendrocytes found mainly in the cerebrum in aged rats. Only a few reports have shown spontaneous occurrence of this tumor in the spinal cord, and no report has mentioned its occurrence in young rats. We encountered a case of spontaneous oligodendroglioma in the lumbar portion of the spinal cord in a young (9 weeks old) female BrlHan:WIST@Jcl (GALAS) rat. Here we report the detailed histopathological and immunohistochemical characteristics of this case. No clinical signs, no gross lesions at necropsy, and no specific changes in hematology or blood biochemistry were observed. The tumor was located in the dorsal funiculus in the lumbar portion of the spinal cord and widely spread to the dorsal root nerve. The neoplastic cells showed a sheet-like growth pattern and had small round nuclei, clear cytoplasm and distinct cell borders that resulted in a honeycomb pattern. No mitotic figures or other histological lesions were observed. The neoplastic cells were positively stained for Olig2 and PCNA. The present case was considered to be a low-grade oligodendroglioma based on the histological and immunohistochemical features. To our knowledge, our case is considered to be extremely rare and the first report in a young rat.  相似文献   
88.
89.
90.
While embryo transfer (ET) is widely practiced, many of the transferred embryos fail to develop in cattle. To establish a more effective method for selecting bovine embryos for ET, here we quantified morphological parameters of living embryos using three-dimensional (3D) images non-invasively captured by optical coherence tomography (OCT). Seven Japanese Black embryos produced by in vitro fertilization that had reached the expanded blastocyst stage after 7 days of culture were transferred after imaged by OCT. Twenty-two parameters, including thickness and volumes of the inner cell mass, trophectoderm, and zona pellucida, and volumes of blastocoel and whole embryo, were quantified from 3D images. Four of the seven recipients became pregnant. We suggest that these 22 parameters can be potentially employed to evaluate the quality of bovine embryos before ET.  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