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   8432篇
  免费   444篇
  国内免费   12篇
林业   608篇
农学   258篇
基础科学   60篇
  1653篇
综合类   1109篇
农作物   312篇
水产渔业   499篇
畜牧兽医   3556篇
园艺   239篇
植物保护   594篇
  2023年   42篇
  2022年   67篇
  2021年   144篇
  2020年   173篇
  2019年   183篇
  2018年   153篇
  2017年   176篇
  2016年   185篇
  2015年   139篇
  2014年   220篇
  2013年   408篇
  2012年   476篇
  2011年   582篇
  2010年   356篇
  2009年   299篇
  2008年   505篇
  2007年   507篇
  2006年   513篇
  2005年   506篇
  2004年   482篇
  2003年   452篇
  2002年   430篇
  2001年   126篇
  2000年   122篇
  1999年   122篇
  1998年   88篇
  1997年   74篇
  1996年   69篇
  1995年   58篇
  1994年   43篇
  1993年   63篇
  1992年   69篇
  1991年   65篇
  1990年   77篇
  1989年   76篇
  1988年   66篇
  1987年   48篇
  1986年   30篇
  1985年   49篇
  1984年   36篇
  1983年   52篇
  1982年   31篇
  1981年   26篇
  1980年   31篇
  1979年   40篇
  1978年   31篇
  1977年   32篇
  1974年   31篇
  1973年   32篇
  1972年   28篇
排序方式: 共有8888条查询结果,搜索用时 15 毫秒
11.
Monorchidism in the horse   总被引:1,自引:0,他引:1  
Six horses with monorchidism, identified at surgery for cryptorchidectomy, are reported. All six presented with a single scrotal testis. Following surgical removal of one testis, they were either hormonally, anatomically or behaviourally determined to be geldings. Three other horses reported in the literature are reviewed. Of these nine cases of monorchidism, eight were thought to be caused by testicular degeneration and one by testicular agenesis. The vaginal process was present in all of the former and absent in the latter. The left side was involved in five of these eight horses. In seven, the epididymis was absent and, in the remaining two, only the epididymal tail was present. The condition was thought to be congenital in the six horses in this series. A surgical approach to identify accurately monorchid horses is described.  相似文献   
12.
13.
The computer-assisted, kinetics-based enzyme-linked immunosorbent assay for coronavirus antibodies in cats was calibrated to the conventional indirect immunofluorescence assay by linear regression analysis and computerized interpolation (generation of "immunofluorescence assay-equivalent" titers). Procedures were developed for normalization and standardization of kinetics-based enzyme-linked immunosorbent assay results through incorporation of five different control sera of predetermined ("expected") titer in daily runs. When used with such sera and with computer assistance, the kinetics-based enzyme-linked immunosorbent assay minimized both within-run and between-run variability while allowing also for efficient data reduction and statistical analysis and reporting of results.  相似文献   
14.
15.
16.
The cause of a streak disease of pearl millet (Pennisetum glaucum), originating from Nigeria, has been attributed to a geminivirus belonging to the African streak virus cluster. A full-length, infectious clone of the virus was obtained which was transmissible by the vectorCicadulina mbila (Naudé). Analysis of the complete nucleotide sequence of the coat protein gene of this virus shows it to be most closely related to sugarcane streak virus. The possible evolutionary implications of this finding are discussed.  相似文献   
17.
In order to characterise and classify an unknown maize-infecting potyvirus isolated from fields in northeast Spain, the entire coat protein gene and the C-terminal twothirds of the large nuclear inclusion protein (NIb) gene were cloned and sequenced. Protein sequencing enabled the cleavage site between the two proteins to be deduced and also revealed that on storage the viral coat protein undergoes a specific degradation in which the N-terminal 39 amino acids are removed. Comparison of the nucleotide sequence of the 3 non-coding region of the viral RNA and the predicted amino acid sequence of the coat protein with the equivalent regions of other members of the potyvirus group revealed that the Spanish virus is closely related to maize dwarf mosaic virus strain A.  相似文献   
18.
19.
A 10-year-old neutered female cat had chylothorax, precaval syndrome, and a mediastinal granuloma resulting from infection with Cryptococcus neoformans. Diagnosis of a chylous effusion was made by cytologic examination of pleural fluid and by finding higher triglyceride levels in the effusion than in serum (825 vs. 64 mg/dl, respectively). Postmortem examination revealed cryptococcal organisms in the mediastinal granuloma, lungs, cerebral meninges, and connective tissues adjacent to the thyroid gland. Chylous effusion in a cat associated with cryptococcosis has not been reported previously. Cryptococcosis should be included in the differential diagnosis in chylous effusions in cats.  相似文献   
20.
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