全文获取类型
收费全文 | 37574篇 |
免费 | 1814篇 |
国内免费 | 4050篇 |
专业分类
林业 | 2385篇 |
农学 | 4442篇 |
基础科学 | 1849篇 |
4845篇 | |
综合类 | 16505篇 |
农作物 | 3131篇 |
水产渔业 | 2038篇 |
畜牧兽医 | 5855篇 |
园艺 | 1569篇 |
植物保护 | 819篇 |
出版年
2024年 | 333篇 |
2023年 | 832篇 |
2022年 | 1476篇 |
2021年 | 1748篇 |
2020年 | 1650篇 |
2019年 | 1837篇 |
2018年 | 1136篇 |
2017年 | 1768篇 |
2016年 | 2099篇 |
2015年 | 1698篇 |
2014年 | 2274篇 |
2013年 | 2320篇 |
2012年 | 2995篇 |
2011年 | 2978篇 |
2010年 | 2233篇 |
2009年 | 2206篇 |
2008年 | 1922篇 |
2007年 | 2071篇 |
2006年 | 1779篇 |
2005年 | 1444篇 |
2004年 | 1181篇 |
2003年 | 910篇 |
2002年 | 697篇 |
2001年 | 585篇 |
2000年 | 466篇 |
1999年 | 400篇 |
1998年 | 348篇 |
1997年 | 302篇 |
1996年 | 243篇 |
1995年 | 256篇 |
1994年 | 217篇 |
1993年 | 211篇 |
1992年 | 159篇 |
1991年 | 157篇 |
1990年 | 121篇 |
1989年 | 121篇 |
1988年 | 74篇 |
1987年 | 62篇 |
1986年 | 36篇 |
1985年 | 16篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1963年 | 6篇 |
1962年 | 3篇 |
1956年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
本文论述了在工程建设中钢筋混凝土质量优劣的重要性,并结合当前施工中存在的一些问题,探讨了该采取的方法,以达到控制工程质量的目的。 相似文献
3.
工科院校在强调专业教育的同时,没能同样重视审美教育。加强对工科院校大学生的审美教育,有助于培养正确的审美观,提高审美能力;有助于完善知识结构,提升人文精神;
有助于形成独立完善的人格,提升人格境界;有助于培养个性和谐、德智体美全而发展的高素质人才。 相似文献
4.
Χ灾绷吹矸酆康挠跋焓钦?,直接影响比间接影响大。Study on the correlation between rice quality and agronomic traits of quality riceNIE Cheng rong, WEN Yu hui, WANG Yun bo, CHEN Ming zhong,LI Mei, LIU Dao quan(Agronomy Department, Foshan University , Nanhai 528231,China)The correlative analy 相似文献
5.
6.
Cabot's tragopan Tragopan caboti is an endemic and endangered pheasant of the lower montane forests of southeastern China. The typical habitats of the tragopan have been seriously fragmented because of forest management for timber production and farmland reclamation in recent years. The effects of the fragment size and isolation on the distribution of the cabot's tragopan were studied in Wuyanling Natural Reserve. Thirty one habitat fragments (2.5-48.5 ha) surrounded by non-habitat sapling coniferous forests, in an intensively managed forested landscape, were surveyed over four seasons for the occurrence of cabot's tragopan. Five of the 31 fragments were occupied in all four seasons and nine were not occupied. Both landscape and habitat factors affected the occurrence of cabot's tragopan, with landscape factors having the greatest effect. Large and less isolated habitat fragments containing a larger amount of the tree Daphniphyllum macropodum were occupied significantly more often than small, isolated fragments. The appearance of cabot's tragopan in the habitat fragments was best explained by the size of the fragments, the distance to the nearest suitable habitat and the amount of macropdous daphniphyllum trees. Our results could be used to improve the management of the forests where Cabot's tragopan occurs in southeastern China. 相似文献
7.
Abstract – The different reproductive roles of the sexes can predict the direction and magnitude of sexual dimorphism of external and internal morphology. Males should have enlarged structures that enhance the acquisition of mating opportunities, whereas females are predicted to have enlarged organs that are associated with the production of eggs. We tested these predictions in male and female lake whitefish, a species in which both sexes have similar overall body size and shape. After controlling for body size, male lake whitefish had significantly longer jaws and pectoral and pelvic fins, larger hearts, and more muscle than females. Sexual dimorphism in relative muscle mass may be one of the most fundamental morphological differences between males and females. Females had relatively heavier livers than males. Because the liver is important for the breakdown of fats and vitellogenesis, selection should favour an enlarged liver in females for the processing of energy and the production of large numbers of eggs. 相似文献
8.
抓好公路施工管理与质量管理的体会 总被引:3,自引:0,他引:3
工程质量是企业素质的综合反映,是项目管理水平的重要标志。质量是企业的生命线。 相似文献
9.
A semi-energy method to analyse the buckling behaviour of edge-stiffened plates under combined compression and bending is presented in this paper, One unloaded edge of the plate is restrained elastically against rotation and the other is stiffened by a st 相似文献
10.