全文获取类型
收费全文 | 359篇 |
免费 | 55篇 |
国内免费 | 67篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 55篇 |
地球物理 | 58篇 |
地质学 | 92篇 |
海洋学 | 147篇 |
综合类 | 48篇 |
自然地理 | 51篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 26篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 33篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 23篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 13篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 18篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有481条查询结果,搜索用时 62 毫秒
211.
蛋白质感染因子与水产养殖 总被引:2,自引:0,他引:2
介绍了蛋白质感染因子的概念、蛋白质感染因子复制机理假说及其证明、蛋白质感染因子多样性等内容,并讨论了水产养殖动物中存在蛋白质感染因子疾病的可能性。 相似文献
212.
本文报道应用有机碘防治养殖对虾疾病的试验。结果表明,15.0mg/dm3浓度的药液消毒可杀死水体中大量细菌,0.3mg/dm3浓度的药液对对虾的蜕壳有促进作用,按一定比例加工成配合饵料投喂对虾,在虾病狂发期可延长养殖时间。文章还对有机碘防治对虾疾病的有关机理进行了初步探讨。 相似文献
213.
本文报道了植物生长素Q.C.对海带苗的影响试验。结果表明,Q.C.对海带苗的细胞分裂具有明显的促进作用,从而加速了海带配子体的生长发育。其中以0.2×10^-^6(V/V)组的效果最明显,经处理3d后配子体大小达18-20μm,11d后达20-23μm,并已进入了性成熟期,♀体一级突起达22%,而对照组的大小为16-18μm,一级突起仅1%,用Q.C.处理配子体阶段转化而成的幼孢子体或幼孢子体阶段 相似文献
214.
215.
韩国林业局(Korean Forest Service,KFS)为了更好地贯彻韩国森林规划,通过使用各种森林数据库,包括森林类型地图和国家森林资源调查,建立了基于GIS的森林灾害管理系统.同时基于森林灾害数据库,建立了森林信息共享平台、森林信息共享门户,用于林业信息与林业专题图的共享.其针对韩国林业局的业务,还构建了森林灾害管理系统,包括森林灾害数据库管理系统、森林火灾管理系统、森林病虫害管理系统、山体滑坡管理系统.韩国森林灾害管理系统使用实地监测工具,预测与森林空间信息有关的森林灾害信息;通过监测防止森林灾害发生,在发生灾害时减少识别时间.通过森林灾害管理系统,可以链接各种政府机构和信息,以实现对火灾、山体滑坡、病虫害和森林生态系统的综合管理系统.通过提供空间information–based位置信息服务,韩国森林灾害管理系统还能给现场提供快速的响应. 相似文献
216.
The unknown aetiology of Chronic Kidney Disease (CKD) has attracted recent attention as a result of the increasing global prevalence and recent reviews of occupational and environmental exposure to nephrotoxins. The main focus of this research is to examine the potential relationship between environmental exposure to known nephrotoxins including arsenic, cadmium and lead and the potential health risk associated with the progressive dysfunction of the kidneys in renal impaired patients with CKD across Northern Ireland. In addition to these known nephrotoxins, co-abundance with several essential elements has been found to play a role as protecting mechanisms while others increase the uptake of nephrotoxic elements as a result of similar absorption mechanisms within the body. Key elements protecting the body from toxicity include selenium and zinc, whereas those which have been attributed to enhance the uptake of arsenic, cadmium and lead include iron and calcium. The compositional nature of the soil and stream geochemical data is explored to aid in the analysis of interactions between elements. Two approaches, one data-driven and the other knowledge-driven, are explored to investigate the associations between co-abundant elements. The bioaccessibility of these elements, which is the portion of the relevant toxin absorbed within the body, is also investigated to identify areas across Northern Ireland with an increased environmental hazard and potential health risk. The study uses a combination of datasets from the United Kingdom Renal Registry (UKRR) unknown aetiology subset, the soil and stream geochemical dataset from the Tellus Survey (GSNI) with the addition of a bioaccessibility subset. Findings suggest a relationship between the presence of elevated arsenic in stream waters and impaired renal function of the kidneys. Interactions between essential elements and potentially toxic elements could explain the regional variation of CKD of uncertain aetiology across Northern Ireland. 相似文献
217.
BM Macey KW Christison J de Goede L Hutchings CD van der Lingen 《African Journal of Marine Science》2016,38(2):269-273
Catches of South African sardine Sardinops sagax have declined in recent years from about 200 000 t harvested annually during the period 2002–2006 to less than 100 000 t. Consequently, some companies are now importing sardine from sources elsewhere in the world to meet local demand for canned sardine and bait. This importation has the potential for the introduction of sardine pathogens, in particular the pilchard herpesvirus (PHV), which could have a negative impact on the currently small South African sardine population. The aims of the current study were to determine whether PHV is present in the local sardine population and to assess the extent to which sardine is being imported into the country and whether imported fish are from countries where the virus is known to be endemic. Fish sampled from South Africa’s western (n = 150), southern (n = 182) and eastern (n = 96) putative stocks of S. sagax were analysed for the presence of PHV using real-time quantitative polymerase chain reaction (qPCR). The origin and amount of potentially infected material imported into South Africa during the period 2010–2014 was also assessed. None of the South African sardine collected during this study tested positive for PHV, suggesting that active PHV was not prevalent in the local population of S. sagax at the time of this study. Between 56 000 and 71 000 t of frozen sardine was imported annually into South Africa from countries where S. sagax occurs, including some from areas (Australia and New Zealand) where sardine infection by PHV is known to be endemic. Hence, it is plausible that the PHV pathogen, capable of perpetuating infections in local sardine populations, could be imported into South Africa along with the importation of frozen sardine. Should local sardine be naïve to the virus, as suggested by this study, then the population is at risk of infection and precautions against such must be taken. 相似文献
218.
闽粤地区鲍暴发性流行病的病因分析和流行病学研究 总被引:5,自引:1,他引:4
1999年以来,福建、广东两省养殖鲍已连续多年发生了暴发性流行病,死亡率可达100%。结合病理学分析与流行病学调查结果分析,认为球状病毒和弧茵并发感染是该暴发病流行的主要原因。电镜观察发现病鲍的肝细胞和肠上皮细胞内有大小约为130~150nm和50-70nm的2种球状病毒,前者数量较多,具外囊膜,后者的病毒颗粒裸露,未见外囊膜。感染造成了鲍的肝脏和肠等器官的细胞结构严重破坏。人工感染实验表明注射、混朱浸泡等方式均会昔擞感染。根据回归实验和流行特.最调查,结合胡疆巴湫果,该病多发生于23℃以下的水温期,主要是通过海水的流动和养殖水的交换和鲍的运销而传播,25℃以上水温未见该病暴发。 相似文献
219.
220.
大骨节病是一种影响因素复杂、病因一直未明的地方病,其学说众多。本文阐明了中国大骨节病地域分布与病情动态变化特征,重点论述了中国大骨节病自然环境与地质环境特征以及病因研究现状。针对多种病因学说,本文认为大骨节病病因是多因素复合作用的结果,硒缺乏是环境背景因素、环境中与人体有关的毒素是主控因素、常量与微量因素的比例失调是影响因素。病因研究中应注意宏观与微观相结合、地学与医学等多学科相结合。 相似文献