全文获取类型
收费全文 | 10812篇 |
免费 | 2151篇 |
国内免费 | 2862篇 |
专业分类
测绘学 | 720篇 |
大气科学 | 2213篇 |
地球物理 | 2804篇 |
地质学 | 5624篇 |
海洋学 | 1736篇 |
天文学 | 279篇 |
综合类 | 1186篇 |
自然地理 | 1263篇 |
出版年
2024年 | 55篇 |
2023年 | 203篇 |
2022年 | 483篇 |
2021年 | 527篇 |
2020年 | 486篇 |
2019年 | 490篇 |
2018年 | 567篇 |
2017年 | 539篇 |
2016年 | 619篇 |
2015年 | 528篇 |
2014年 | 652篇 |
2013年 | 653篇 |
2012年 | 699篇 |
2011年 | 698篇 |
2010年 | 780篇 |
2009年 | 724篇 |
2008年 | 636篇 |
2007年 | 637篇 |
2006年 | 562篇 |
2005年 | 455篇 |
2004年 | 424篇 |
2003年 | 385篇 |
2002年 | 346篇 |
2001年 | 335篇 |
2000年 | 353篇 |
1999年 | 425篇 |
1998年 | 366篇 |
1997年 | 370篇 |
1996年 | 298篇 |
1995年 | 287篇 |
1994年 | 257篇 |
1993年 | 211篇 |
1992年 | 180篇 |
1991年 | 112篇 |
1990年 | 108篇 |
1989年 | 87篇 |
1988年 | 59篇 |
1987年 | 44篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1958年 | 5篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
The anodic stripping voltammetry with physically-coating mercury film electrode was used to investigate the complexing action
of trace heavy metals in seawater with organic ligands. The apparent copper complexing capacity of seawater was determined
by titrating the organic ligands in natural seawater with standard ionic copper solution. The complexing actions of copper
in seawater with humic acid (HA) or fulvic acid (FA) were investigated by titrating copper in seawater with HA or FA solution.
The equilibrium time, electrodeposition potential, and effect of pH etc. were investigated respectively. The results show
that the interaction of copper in seawater with organic matter is a fast process. At natural pH, HA or FA tend to act with
copper in seawater to form nonlabile complexes. During experimental electrode process, these complexes did not significantly
dissociate. The experimental results were calculated according to 1∶1 complex formation. 相似文献
24.
The accuracy of the AE index as a measure of the joule heat production rate is examined for a typical substorm event on 18 March 1978 by estimating the global joule heat production rate, as a function of time, using data obtained from the IMS six meridian chains. In spite of the fact that the AE index had had an initial slow growth which was followed by a rapid growth, the joule heat production rate attained a high level during the slow growth and thus their variations were considerably different from those of the AE index. Therefore, although the AE index is statistically linearly related to the global joule heat production rate, one should be cautious in assuming that details of time variations of the AE index during individual events represent those of the joule heat production rate. 相似文献
25.
严格论证了在对空间或地面目标的定位中,利用伪距测量观测模型的几何因子大于用台站间一次差分观测模型的几何因子.此外,台站间完全差分测量观测的定位精度优于不完全测量情形的定位精度.这些结果给人们在实际工作中采取何种定位方式提供了可靠的理论依据. 相似文献
26.
27.
科技进步是测绘事业发展的动力 ,讨论运用科技进步的评价指标 ,对测绘单位的科技进步速度和对经济增长的贡献等进行测算和分析 ,可以为测绘规划管理及决策提供参考。 相似文献
28.
THECONSTRUCTIONANDITSDEVELOPMENTOFTHEOVERSEASTRANSPORTSYSTEMINNORTHEASTCHINAGaoShali(高莎丽)(DepartmentofGeography,NortheastNorm... 相似文献
29.
The new polyenzyme method for making gravy from Harengula zunasi offal involves protein enzymolysis with flavorase after proper alkaline and neutral protease levels were established by orthogonal trials to select the best hydrolytic conditions for processing offal with alkaline and neutral protease. The conditions for the polyenzyme method were pH of 7.0, temperature of 50℃ , alkaline and neutral protease concentration of 1.5% respectively, hydrolysis time of 120 min, andflavorase concentration of 2.0% , for 60 min. The new gravy-making technology yields a nutritious and delicious gravy containing 40.3 % of total essential amino acids, with delicious amino acids Glu, Asp, Gly, Ala, Pro and Ser comprising 49.5% , total and amino nitrogen being respectively1.9 and 1.1 g/100 g (amino acid nitrogen being 61.0% of total nitrogen), The polyenzyme method was used to make 14.8% protein gravy from Harengula zunasi offal. In addition, in inorganic elements, the phosphorus content is the highest. 相似文献
30.
EFFECT OF SULPHATE-REDUCING BACTERIA ON ELECTRO-CHEMICAL CORROSION BEHAVIOR OF 16Mn STEEL IN SEA MUD
INTRODUCTIONItwasgenerallyconsideredpreviouslythatthecorrosionofsteelinseamudwasnotserious.However,itwaslaterfoundthatthecorrosionrateofsteelinsomeseamudwashigherthanthatinseawater(King,1980;Sehmide,1982;Guoetal.,1997;Hou,1998).Therearesomereportsthatthecorrosionr… 相似文献