全文获取类型
收费全文 | 3469篇 |
免费 | 832篇 |
国内免费 | 689篇 |
专业分类
测绘学 | 125篇 |
大气科学 | 92篇 |
地球物理 | 162篇 |
地质学 | 1021篇 |
海洋学 | 3110篇 |
天文学 | 5篇 |
综合类 | 249篇 |
自然地理 | 226篇 |
出版年
2024年 | 53篇 |
2023年 | 130篇 |
2022年 | 193篇 |
2021年 | 211篇 |
2020年 | 232篇 |
2019年 | 223篇 |
2018年 | 171篇 |
2017年 | 174篇 |
2016年 | 195篇 |
2015年 | 161篇 |
2014年 | 233篇 |
2013年 | 256篇 |
2012年 | 237篇 |
2011年 | 242篇 |
2010年 | 195篇 |
2009年 | 225篇 |
2008年 | 157篇 |
2007年 | 183篇 |
2006年 | 195篇 |
2005年 | 192篇 |
2004年 | 163篇 |
2003年 | 167篇 |
2002年 | 139篇 |
2001年 | 95篇 |
2000年 | 112篇 |
1999年 | 89篇 |
1998年 | 49篇 |
1997年 | 48篇 |
1996年 | 48篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 31篇 |
1992年 | 30篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有4990条查询结果,搜索用时 15 毫秒
71.
晋江河口及泉州湾湿地生物分布特点 总被引:3,自引:0,他引:3
泉州湾受晋江河口径流影响很大,导致湿地生物的水平分布与盐度的分布紧密相关.大致分为湾外和外湾种、内湾低盐种、感潮河段咸淡水种.长腕和尚蟹、扁平蛛网海胆和文昌鱼仅分布在外湾或湾外的砂质海底.3种红树植物、互花米草、招潮蟹、弹涂鱼是内湾泥滩的优势种.咸水草是感潮河段咸淡水指标种.河蚬虽是淡水种,也分布在低盐河段. 相似文献
72.
73.
厦门东海域定置网渔获鱼类种类组成及其季节变化 总被引:7,自引:1,他引:7
2003年7月~2004年6月对厦门东部海域的定置网渔获鱼类进行采样分析.结果表明厦门东海域至少有鱼类242种,隶属于19个目81科145属,主要是沿岸近底层和底栖的小型鱼类.以鲈形目种类最多,共计127种,占总数的52.5%、经济种类有116种.主要优势种有:青鳞小沙丁鱼、孔鳞小沙丁鱼、斑鲦、马拉邦虫鳗、裸鳍虫鳗、中华须鳗、前鳞鲻、眶棘双边鱼、多鳞鳝、皮氏叫姑鱼、短棘银鲈、列牙垒幸4、黄斑蓝子鱼、褐蓝子鱼、锯塘鳢、锻虎鱼类、褐菖鲇、绿鳍鱼、鳄鲡、卵鳎、中华单角鲍等.渔获种类在秋季及冬初最多,夏季较多,而冬末和春初最少.渔获种类的季节变化比较明显,与海洋表层水温变化有关,种类的月更替率比较高. 相似文献
74.
烟台市污水处理深海排放工程设计方案研究与选择 总被引:2,自引:0,他引:2
沿海城市污水处理深海排放工程在我国起步较晚,烟台市污水处理深海排放工程我国目前规模最大的同类工程,且已进入施工阶段,本文详细阐述了该工程及水工设计方案,在我国城市污水2深海排放工程领域作了积极有益的探索。 相似文献
75.
刘剑华 《中国海洋大学学报(自然科学版)》1996,(1)
根据1957~1987年期间采自浙江和福建沿岸的仙菜科海藻标本,初步鉴定有7属14种。分两次报道,首先报道其中的5屑7种:复羽多孢藻Pleonosporiumvenustissimum、日本对丝藻Antithamnionnipponicum和卡洛绢丝藻Callithamnioncallophyllidicola为我国首次较全面描述和绘图记录;赫勒对丝藻Antithamnionhubbsii为浙、闽海域首次报道;而如下三个种纵胞藻Centrocerasclavulatum、日本凋毛藻Griffithsiajaponica和对公藻Antithammioncruciatum在浙、闽海区早有报道。 相似文献
76.
Abstract. The marine plant communities of the littoral zone in different biotopes of the Greek coasts were investigated in 1980-81. Seasonal distribution and variation of marine plant biomass were assessed. The communities of Cystoseira crinita and C. compressa were outstanding with maximum biomass during the summer months. Corallina officinalis and Pterocladia capillacea + Viva rigida communities predominated with maximum biomass in autumn and exhibited a decrease in winter, except in stressed biotopes. The species diversity and productivity of seaweeds along the Greek coasts are interpreted in relation to a number of environmental parameters. 相似文献
77.
The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers 总被引:5,自引:1,他引:5
Based on Iwan‘s wake oseillator model developed with the classical van der Pol equalion, the differential equation for the response of the vortex-induced vihration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the intermal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity. 相似文献
78.
The atomic force microscopy (AFM) is a recently developed, bench-top instrument that can image the surface structures of biological
specimens at high resolution with simultaneous measurement of their size. This paper describes the application of AFM to marine
bacteria. Both natural and cultured bacteria were retained on a filter or placed on glass, washed, air-dried and observed
by AFM. The instrumental condition, the choice of suitable filter, effect of fixation and filtration, comparison with epifluorescent
microscopic (EFM) count, and the size and shape of bacterial cells were investigated. An Isopore filter was best for concentration
and subsequent observation because of its surface flatness. Cross section images showed that both rod and coccoid cells were
flattened, the former usually having a two-humped shape. Bacterial cells were differentiated from non-living particles based
on their cross section shape and size. Bacterial counts by AFM and EFM showed good agreement. Although size measurement is
easily done by the instrument, AFM tends to overestimate the size of microspheres. More work is thus needed on the size measurement
of living organisms. Because AFM easily provides images of natural bacterial cells at high magnification, it can be used as
a new tool to study the fine structures of marine bacteria.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
80.
食用海藻对肠道菌群及肠道微环境影响的研究 总被引:2,自引:0,他引:2
综述了食用海藻对大鼠盲肠肠道菌群及肠道微环境的影响。大鼠喂食添加紫菜等 9种食用海藻的饲料后 ,均能对其盲肠微生物区系及代谢产物和血清脂质水平产生不同的影响 :使肠道中的双歧杆菌数量增加 ,p H值降低 ;抑制血清甘油三酯及血清游离脂肪酸含量。从而改善肠内的生态环境 相似文献