全文获取类型
收费全文 | 10774篇 |
免费 | 2666篇 |
国内免费 | 3676篇 |
专业分类
测绘学 | 1237篇 |
大气科学 | 1770篇 |
地球物理 | 2312篇 |
地质学 | 6630篇 |
海洋学 | 2111篇 |
天文学 | 272篇 |
综合类 | 1092篇 |
自然地理 | 1692篇 |
出版年
2024年 | 64篇 |
2023年 | 230篇 |
2022年 | 638篇 |
2021年 | 753篇 |
2020年 | 593篇 |
2019年 | 788篇 |
2018年 | 769篇 |
2017年 | 673篇 |
2016年 | 661篇 |
2015年 | 707篇 |
2014年 | 705篇 |
2013年 | 803篇 |
2012年 | 851篇 |
2011年 | 961篇 |
2010年 | 880篇 |
2009年 | 828篇 |
2008年 | 726篇 |
2007年 | 684篇 |
2006年 | 646篇 |
2005年 | 582篇 |
2004年 | 433篇 |
2003年 | 307篇 |
2002年 | 346篇 |
2001年 | 296篇 |
2000年 | 329篇 |
1999年 | 310篇 |
1998年 | 182篇 |
1997年 | 210篇 |
1996年 | 178篇 |
1995年 | 172篇 |
1994年 | 140篇 |
1993年 | 171篇 |
1992年 | 108篇 |
1991年 | 81篇 |
1990年 | 64篇 |
1989年 | 49篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1958年 | 14篇 |
1957年 | 1篇 |
1954年 | 4篇 |
1947年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
61.
62.
In the present experiments, ethyl methanesulfonate (EMS) is used to treat blue-green alga Spirulina platensis. Results show that the chemical is a very effective mutagen on the species and some genetic changes, including morphological variation, different growth rate and greater resistance to low temperature, have been found, which may offer an efficient method for the strain breeding of Spirulina platensis. 相似文献
63.
The adsorption kinetics of Pb, Cu and Cd on hydrous ferrk oxide (HFO) has been approached in tthe simulated environmental conditions of the Changjiang Estuary. The forward adsorption rate constants of different systems under different temperatures have been determined, and the activation energies of the adsorption for Pb and Cu evaluated (Pb=7 kcal/mol, Cu= 11 kcal/mol). The results show that Pb and Cu are strongly adsorbed by HFO; the order of their adsorption rate is found to be Pb≥Cu≥Cd, which follows thte order of their theonody-namic equilibrium constants. It has been demonstrated that the surface exchange-adsorption is the determining step of the solid-liquid interface process. The field investigation results are theoretically explained by the kinetic mechanism. 相似文献
64.
北黄海沉积物——水界面反硝化速率及影响因素研究 总被引:4,自引:0,他引:4
探讨近海氮的循环机制,采用乙炔抑制法和现场静态箱法对北黄海夏季局部海域的反硝化速率进行了研究,该海域反硝化速率在2.5~5.8μmol/m2.h之间,平均4.85μmol/m2.h。影响其反硝化速率的主要因素为溶解氧,其次是温度。北黄海的反硝化速率低于珠江口和长江口海域。 相似文献
65.
以灰树花发酵菌丝体为原料,经过提取分离纯化得到1种水溶性多糖GF4F1,经高碘酸氧化、Smith降解、甲基化、红外光谱(IR)以及核磁共振波谱(NMR)等分析表明,该多糖是1种β-1, 3/1,6-葡聚糖,且小鼠体内实验结果表明其具有良好的抗肿瘤活性。在1mg/kg时,对小鼠抑制率为67.3%。 相似文献
66.
67.
68.
Li Yucheng He Ming Professor Dalian University of Technology Dalian Former master student Dalian University of Technology Dalian 《中国海洋工程》1994,(3)
-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice. 相似文献
69.
根据聚类方法,对闽南-台湾浅滩渔场变性水团进行划分,本海区共有6个变性水团。讨论各个变性水团在不同季节消长变化规律。 相似文献
70.
A study on zooplankton distribution patterns and indicator species in Kuroshio upstream area and adjacent East China Sea 总被引:3,自引:0,他引:3
On the basis of the data of zooplankton biomass and three major taxa—— Copepoda, Chaetognatha andSiphonophora of May-June 1986, July-August and December 1987, the distributional patterns and the indicator species of zooplankton in the Kuroshio and adjacent waters of the East China Sea are preliminarily studied. The results are as follows:The horizontal distribution of zooplankton biomass and the abundance of copepods, chaetognaths and siphonophores arecurred in the continent area northwest of Taiwan and the south-centre section of the East China Sea continent, which are the mix front of different waters. Zooplankton in the water area inside of Ryukyu Islands presented low abundance and high diversity. There are clear seasonal variations in zooplankton biomass and abundance in the study area. The strength or weakness of different water masses and fronts is the basic reason for the variations of zooplankton biomass and abundance.The species composition of zooplankton in the study area is complex and var 相似文献