全文获取类型
收费全文 | 348篇 |
免费 | 34篇 |
国内免费 | 56篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 13篇 |
地球物理 | 16篇 |
地质学 | 37篇 |
海洋学 | 216篇 |
综合类 | 52篇 |
自然地理 | 80篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 16篇 |
2020年 | 11篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 13篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 24篇 |
2013年 | 37篇 |
2012年 | 14篇 |
2011年 | 13篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 20篇 |
2007年 | 24篇 |
2006年 | 27篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 13篇 |
2002年 | 16篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有438条查询结果,搜索用时 187 毫秒
51.
Tetraploid induced by physical and chemical methods in Jinjiang oyster(Crassostrea rivularis) 总被引:1,自引:0,他引:1
Rong Shoubai Shi Shumei Mo Qirong Liu Shaeqiong Liang Ze Zhao Xiuzhu Tong Wangdong Li Shouwu Li Yimin 《海洋学报(英文版)》1994,13(2):275-283
TetraploidinducedbyphysicalandchemicalmethodsinJinjiangoyster(Crassostrearivularis)¥RongShoubai,ShiShumei,McQirong,LiuShaeqio... 相似文献
52.
雄性三倍体长牡蛎繁殖潜力的初步研究 总被引:1,自引:0,他引:1
国内外很多人做过三倍体长牡砺的诱导工作,但在三倍体性腺发育及配子活力方面的研究,目前仅见Allen等1986年和1990年对三倍体的海螂和长蛎异常配子的发生报道。Cox1996年研究了悉尼岩牡蛎三倍体性腺发育情况,姜卫国等对三倍体合浦珠母贝的生殖腺进行了观察,李霞[1]对三倍体长牡蛎的性腺发育做了较系统的分析和总结。作者用流式细胞仪对长牡蛎Crassostrea gigas二、三倍体的性腺细胞进行了初步分析,回答了三倍体长牡蛎生殖潜力及性比方面的一些问题,为进一步研究三倍体长牡蛎的生长、繁殖、杂… 相似文献
53.
Abstract. Boonea (= Odostomia) impressa is a common ectoparasite of oysters. In the laboratory, small oysters (Crassostrea virginica) parasitized by natural densities of B. impressa produced 75 % less new shell than unparasitized oysters. Shell deposition rates of previously parasitized oysters increased significantly after all B. impressa were removed. Thus, the decrease in growth rate, although significant, apparently was not permanent. B. impressa preferentially parasitized small, living oysters (≤2.5cm) in the field, even though a higher percentage of large, living oysters (>2.5cm) was available. The snails maintained an aggregated distribution on the oyster reef. The number of B. impressa per oyster clump was positively correlated with the number of living oysters per clump, however some clumps with few or no living oysters had many B. impressa. Thus, food availability only partially explained the pattern of distribution. B. impressa was very mobile. About 50 % of the population moved in one week. Reproduction occurred throughout the year with a peak period in May. Recruitment was greatest in July, however new recruits were observed throughout the year. The reduction in growth rate of parasitized oysters, the snaiľs propensity towards parasitizing small oysters and the snail's tendency to be contagiously distributed suggests that B. impressa potentially exerts a significant influence on the population structure and health of oyster populations. 相似文献
54.
利用琼胶作为唯一的碳源从青岛太平角海域的海水和红藻样品中筛选分离得到一株高产琼胶酶的海洋菌F-6,对其最适的产酶条件,利用琼胶酶分离条斑紫菜的原生质体和原生质体的培养进行研究。结果表明,通过单次单因子和正交实验确定琼胶降解菌株F-6最适产酶培养基配方为(W/V):琼胶0.7%;酵母粉0.3%;蛋白胨0.5%;NaCl2.0%;K2HPO40.1%;CaCl20.02%;MgSO4·7H2O0.05%;FeSO4·7H2O0.002%;起始pH=7.5,最适的发酵产酶条件为:26℃培养36h。经条件优化后,粗酶液的酶活高达631.6U/ml。发酵液经过6000g离心30min得到粗酶液,粗酶液经过8k分离膜超滤,加入1mol/L渗透剂,0.22μm滤膜过滤除菌后降解条斑紫菜组织块,成功地分离得到大量的紫菜原生质体,其产率为3×106个原生质体/g新鲜紫菜组织。原生质体经初步培养发育成愈伤组织,其成活率为60%。 相似文献
55.
A Santa Marta JG Ferreira GC Pitcher J Lencart e Silva 《African Journal of Marine Science》2020,42(2):151-166
The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes, simulating an annual mean phytoplankton biomass of 7.5 µg Chl a l–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y–1. The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers. 相似文献
56.
叶立勋 《中国海洋大学学报(自然科学版)》1990,(3)
介绍三种通过底栖动物群落结构的变化对有机物污染监测和评价的方法,并分别对澳大利亚塔斯马尼亚州Nubeena鳟鱼养殖场内由高密度网箱养鱼诱发的有机物污染进行了检测。结果表明:距网箱垂线0m处为严重污染区域,10m处为中度污染区域,30m为过渡类型,其有机物对该处底栖生物仍具有害影响,60m处为轻度有机物富集区,但该处有机物对底栖生物的总效应是有益的,60m以外为正常区域。本文还对三种方法的适用性进行了讨论。 相似文献
57.
Joana F.M.F. Cardoso Denis Langlet Jos F. Loff Ana R. Martins Johannes IJ. Witte Paulo T. Santos Henk W. van der Veer 《Journal of Sea Research》2007,57(4):303-315
The Pacific oyster Crassostrea gigas was introduced in Europe for commercial purposes in the mid 1960s. It was initially thought that low winter temperatures would restrain this species' reproduction and settlement; however, its present distribution in areas where no introduction has taken place suggests that natural invasion and expansion has occurred. Along the European coast, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Whether C. gigas will continue to further expand through northern waters will depend on its physiological performance. In this study, the performance of wild oyster populations has been studied in terms of growth and reproduction at three stations: La Rochelle (France; 46°N), Yerseke (Oosterschelde estuary, The Netherlands, 51°N), and Texel (Wadden Sea estuary, The Netherlands, 53°N). The French population had the lowest somatic-shell mass ratio and an increase in maximum shell length, somatic and gonadal mass was observed from France to the Netherlands. In addition, mean oocyte diameter decreased significantly from south to north. The combination of increasing gonadal mass and decreasing oocyte volume suggests an increasing reproductive output in terms of egg numbers from France to The Netherlands. Differences in temperature between locations will at least be partly responsible for the observed patterns; however, other environmental factors (such as food availability, predation pressure, sediment type and/or seston concentration) cannot be excluded. Since smaller eggs (oocytes) are thought to have a longer development time, the environmental conditions along the Dutch coast may result in increased larval dispersal and possibly in further population expansion. 相似文献
58.
几种海水贝类甲醛浸渍标本DNA的提取及rRNA基因ITS序列的扩增 总被引:8,自引:0,他引:8
从中国科学院海洋生物标本馆收藏的8种甲醛浸渍的海水贝类标本中提取DNA并对其rRNA编码基因的ITS序列进行特异性扩增,在牡蛎Crassostrea sp.、长肋日月贝Amussium pleurondectes (Linnaeus)、扇贝Volachlamys ringaporinug(Sowerby)与华贵栉孔扇贝Chlamys nobilis(Reeve)等4个物种的标本中成功获得扩增产物。利用图片分析软什得出牡蛎标本的ITS-1和ITS-2扩增片段分别为408bp和524bp,长肋日月贝标本分别521bp和537bp,而扇贝Volachlamys ringaporinug(Sowerby)与华贵栉孔扇贝标本只获得ITS-1扩增片段,长度均为545bp。 相似文献
59.
采用肾上腺素(EPI)和去甲肾上腺素(NE)诱导、颗粒固着基和先固着后脱基三种方法,对褶牡蛎的眼点幼虫进行处理,产生单体蛎苗。EPI和NE诱导的最适浓度为10~(-4)M,最适处理时间为3h,幼虫的不固着变态率分别达47.7%和46.6%。处理时间延长,变态率增加不明显。EPI和NE的诱导效果差别不明显,其诱导作用对稚贝的生长无明显副作用。颗粒固着基以贝壳粉为佳,最适颗粒的规格为幼虫的壳长。幼虫先固着后脱基而形成单体蛎苗,以可弯曲的灰色塑料板效果最好,固着的小贝可通过来回弯曲塑料板而从上面脱落下来,小贝长至1~2cm大小时,脱基最容易。 相似文献
60.
David K. A. Barnes 《Marine Ecology》2001,22(3):189-200
Abstract. The reef‐dwelling oyster Dendrostrea frons occupied only a small proportion of space in coral reefs of the Quirimba Archipelago, Mozambique, but supported a disproportionately high variety of taxa. Assemblages on primary (substratum), secondary (dead coral heads) and ephemeral secondary space (D. frons shells) of similar area were compared across 5 depths (5, 10, 15, 20 and 25 m) and at four taxonomic levels (species, genus, class and phylum). Differences between the taxonomic richness of each type of space differed with both taxonomic level considered and depth. Of the three categories of space considered, ephemeral secondary space had the most taxa at all levels with the maximum at 10 – 15 m. Despite being small in space and time, animal externa, such as shells of D. frons, may provide important niches for particular organisms at many taxonomic levels. 相似文献