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   67181篇
  免费   3792篇
  国内免费   632篇
林业   3884篇
农学   3205篇
基础科学   854篇
  9219篇
综合类   8523篇
农作物   2512篇
水产渔业   3721篇
畜牧兽医   34854篇
园艺   897篇
植物保护   3936篇
  2021年   687篇
  2020年   705篇
  2019年   767篇
  2018年   1199篇
  2017年   1311篇
  2016年   1355篇
  2015年   1216篇
  2014年   1383篇
  2013年   2828篇
  2012年   2471篇
  2011年   2759篇
  2010年   1866篇
  2009年   1724篇
  2008年   2524篇
  2007年   2515篇
  2006年   2401篇
  2005年   2237篇
  2004年   1957篇
  2003年   1930篇
  2002年   1802篇
  2001年   2569篇
  2000年   2376篇
  1999年   1877篇
  1998年   819篇
  1997年   706篇
  1996年   692篇
  1995年   763篇
  1994年   668篇
  1993年   649篇
  1992年   1334篇
  1991年   1444篇
  1990年   1520篇
  1989年   1385篇
  1988年   1279篇
  1987年   1246篇
  1986年   1179篇
  1985年   1111篇
  1984年   926篇
  1983年   730篇
  1982年   527篇
  1979年   795篇
  1978年   617篇
  1976年   527篇
  1975年   503篇
  1974年   629篇
  1973年   606篇
  1972年   633篇
  1971年   602篇
  1970年   590篇
  1969年   540篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Identification of Histoplasma organisms in circulating eosinophils of a dog   总被引:1,自引:0,他引:1  
Disseminated histoplasmosis was diagnosed in a 10-year-old dog that had chronic diarrhea, weight loss, fever, and anemia. The diagnosis was based on detection of Histoplasma organisms in circulating neutrophils, monocytes, and eosinophils. The dog had severe histoplasmal fungemia, which may have been caused by treatment with prednisolone.  相似文献   
993.
Cell contents of foetal fluids obtained separately from amniotic and allantoic cavities of live cows by transvaginal amniocentesis and by aspiration from pregnant uteri immediately after slaughter were studied using Papanicolaou's staining procedure. The samples obtained belonged to cows which were between ten to 24 weeks of gestation. Cell scrapings from foetal and membranous surfaces normally in contact with the foetal fluids were also stained simultaneously with foetal fluid smears by Papanicolaou's method to determine the probable origin of the cells detected in the amniotic and allantoic cavities. The cell types were classified according to morphology and tinctorial patterns and their origin was deduced on the basis of similarity to cell scrapings from the surface layers of foetus and foetal cavities. The evaluation of foetal fluid cells revealed that a majority of cells are of foetal origin and that the cytological features of these cells may be useful in assessing the condition of the foetus.  相似文献   
994.
Water, Air, &; Soil Pollution - The bacterial communities in the intestinal tracts of earthworm were isolated by culture-dependent approaches. In total, 72 cultures were isolated and purified...  相似文献   
995.
The aim of the present study was to investigate the effects of fibroblast growth factor-10 (FGF-10) on the survival, activation (transition from primordial to primary follicles), and growth of goat preantral follicles cultured in vitro. Pieces of ovarian cortex were cultured for 1 and 7 d in the absence or presence of FGF-10 (0, 1, 10, 50, 100, and 200 ng/mL). Noncultured and cultured tissues were processed and analyzed by histology, transmission electron microscopy, and viability testing. Results showed that after 7 d, a greater percentage (79.9%) of morphologically normal follicles (containing an oocyte with regular shape and uniform cytoplasm, and organized layers of granulosa cells without a pyknotic nucleus) was observed when cultured with 50 ng/mL of FGF-10 when compared with other concentrations of FGF-10 (0 ng/mL, 67.3%; 1 ng/mL, 68.2%; 10 ng/mL, 63.3%; 100 ng/mL, 64.4%; 200 ng/mL, 52.7%). Ultrastructural analyses and viability testing using fluorescent markers confirmed the follicular integrity of FGF-10 (50 ng/mL)-treated fragments after 7 d of culture. After 7 d, all FGF-10 concentrations reduced the percentage of primordial follicles and increased the percentage of developing follicles. In the presence of 50 ng/mL of FGF-10, follicles increased in diameter after 7 d of culture when compared with other concentrations tested. In conclusion, this study demonstrates that FGF-10 maintains the morphological integrity of goat preantral follicles and stimulates the growth of activated follicles in culture. The culture conditions identified here contribute to the understanding of the factors involved in goat early follicular development.  相似文献   
996.
论"天人合一"与林业可持续发展   总被引:1,自引:0,他引:1  
在全球环境生态危机不断威胁人类生存的今天 ,人们在重新审视历史时发现 ,中国传统文化对人与自然的认识含有丰富的辩证哲理。与西方追求利益最大化的林业管理理念不同 ,中国古代的林业经营管理思想 ,是以“天人合一”思想为指导 ,实现经济、社会和环境的和谐可持续发展的“生生之道”。随着现代化建设与社会的进步 ,我国面临日益严峻的人口、资源、环境、粮食、能源等诸多问题 ,愈来愈倚赖于林业的可持续发展。可持续发展已成为维系人类生存的途径 ,对古代这一宝贵思想进行回顾与分析 ,可为当代林业的可持续发展提供有力的借鉴。  相似文献   
997.
998.
999.
影响饲料制粒的因素及其控制方法分析   总被引:4,自引:0,他引:4  
影响制粒的因素很多,有制粒机自身性能、待制粒原料理化性质、生产操作和工艺条件等。本文从饲料组分、物料理化性质、配方组成、压模和压辊等几个方面作了简要阐述,为提高饲料制粒效率,保证制粒质量提供参考。  相似文献   
1000.
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