全文获取类型
收费全文 | 10116篇 |
免费 | 970篇 |
国内免费 | 1706篇 |
专业分类
化学 | 2979篇 |
晶体学 | 138篇 |
力学 | 256篇 |
综合类 | 111篇 |
数学 | 739篇 |
物理学 | 2009篇 |
综合类 | 6560篇 |
出版年
2024年 | 27篇 |
2023年 | 111篇 |
2022年 | 265篇 |
2021年 | 351篇 |
2020年 | 283篇 |
2019年 | 263篇 |
2018年 | 231篇 |
2017年 | 326篇 |
2016年 | 290篇 |
2015年 | 433篇 |
2014年 | 549篇 |
2013年 | 662篇 |
2012年 | 708篇 |
2011年 | 734篇 |
2010年 | 702篇 |
2009年 | 800篇 |
2008年 | 908篇 |
2007年 | 864篇 |
2006年 | 809篇 |
2005年 | 632篇 |
2004年 | 493篇 |
2003年 | 331篇 |
2002年 | 372篇 |
2001年 | 335篇 |
2000年 | 382篇 |
1999年 | 201篇 |
1998年 | 115篇 |
1997年 | 88篇 |
1996年 | 84篇 |
1995年 | 92篇 |
1994年 | 66篇 |
1993年 | 55篇 |
1992年 | 38篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 32篇 |
1988年 | 19篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1965年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
ChuanChunZOU ShuJieHOU PingShengLEI XiaoTianLIANG 《中国化学快报》2003,14(4):361-364
Two spirostanol saponins(gracillin and dioscin)which have the typical sugar moieties were synthesized facilely by a general approach. 相似文献
162.
XRF分析铁矿粉的标准选择判据研究和应用 总被引:2,自引:0,他引:2
本文对XRF法分析铁矿的基体校正元素进行了研究,并建立了标准选择判据,编制的计算软件可以自动地从大量标样中选择适合该样品分析的标准。该法可用于粉末压片制样的分析,方法快速,准确度和精密度均符合生产要求。 相似文献
163.
X射线辐照前后,在BaF(Cl,Br):Sm^2+中以560nm的Nd:YAG脉冲光在液氮温度下进行了双光子烧孔实验和光激励发光实验,结果表明,Sm^2+掺杂的碱土金属氟卤化物光谱烧孔过程中伴随着光激励发光过程,这一过程直接影响光谱烧孔过程的进行。 相似文献
164.
165.
The sedimentation equilibrium of colloidal suspensions modeled by hard-core attractive Yukawa (HCAY) fluids in a planar pore is studied. The density profile of the HCAY fluid in a gravitational field and its distribution between the pore and uniform phases are investigated by a density functional theory (DFT) approach, which results from employing a recently proposed parameter-free version of the Lagrangian theorem-based density functional approximation (Zhou, S. Phys. Lett. A 2003, 319, 279) for hard-sphere fluids to the hard-core part of the HCAY fluid, and the second-order functional perturbation expansion approximation to the tail part as was done in a recent partitioned density functional approximation (Zhou, S. Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 2003, 68, 061201). The resultant DFT approach is, thus, the first adjustable parameter-free DFT for HCAY fluids. The validity of the present DFT for HCAY fluids of reduced range parameter z(red) = 1.8 under various external potentials is established in the first of the papers cited previously. The present DFT for HCAY fluids can predict the radial distribution function for the bulk HCAY fluid accurately in the colloidal limit (large value of z(red)), and in the hard-sphere limit, its prediction for the density profile of the hard-sphere fluid in a gravitational field is in very good agreement with the existing simulation data. The dependence of the density profile and distribution coefficient on the magnitude of the interparticle attraction, gravitational field, and degree of confinement is investigated in detail by the present DFT approach. Intuitive and qualitative analyses are also compared with the quantitative DFT calculational results. 相似文献
166.
Tingzhen Li Yong Yang Zhichao Tao Haijun Wan Xia An Chenghua Zhang Hongwei Xiang Yongwang Li 《天然气化学杂志》2007,16(4):354-362
The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor(CSTR)over a Fe-Mn catalyst.The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),Mφssbauer spectroscopy,and CO_2 temperature-programmed desorption(TPD).The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas,and decreased the catalyst surface basicity.At the same time,the addition of small amounts of sulfate improved the activities of Fischer- Tropseh synthesis(FTS)and water gas shift(WGS),shifted the product to light hydrocarbons(C_1-C_(11)) and suppressed the formation of heavy products(C_(12 )).Addition of SO_4~(2-)to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe,and S-05 catalyst gave the highest CO conversion(62.3%),and beyond this sulfur level the activity of the catalyst decreased. 相似文献
167.
168.
2002年中国颁布科普法后,2003至2011年出版的化学普及书籍种数总体呈上升趋势。出版地和出版社总体上较为分散,局部集中度高。主题上基础知识类化学普及书籍最多,科学文化类次之,实用知识类较少,化学前沿类最少。涉及科普的一般法律、法规和政策对化学普及书籍的创作影响甚微。只有与国家约束性社会发展指标相关,发生涉及公民生命安全的重大社会事件,针对特定人群的具体实施政策出台,科普法规和政策才对化学普及书籍的出版起到推动作用。 相似文献
169.
170.
ZHOU Yin-Zhuang② LI Jin-Fang TU Shu-Jie ZHANG Min 《结构化学》2005,24(10):1193-1197
1 INTRODUCTION The chemistry of copper compounds has been extensively investigated and the relationship be- tween structure and reactivity, ranging from indus- trial catalysis to biochemistry activity, is of major importance. For binuclear copper(II) complexes equa- torially bridged by pair of hydroxide[1] or alkoxide[2, 3] groups, satisfactory linear correlation is found be- tween the Cu–O–Cu bridging angle and spin coupling between the metal centers. However, for binuclear copper(I… 相似文献