全文获取类型
收费全文 | 4211篇 |
免费 | 160篇 |
国内免费 | 326篇 |
专业分类
化学 | 3606篇 |
晶体学 | 25篇 |
力学 | 17篇 |
综合类 | 10篇 |
数学 | 4篇 |
物理学 | 1035篇 |
出版年
2024年 | 8篇 |
2023年 | 81篇 |
2022年 | 46篇 |
2021年 | 66篇 |
2020年 | 80篇 |
2019年 | 83篇 |
2018年 | 59篇 |
2017年 | 64篇 |
2016年 | 116篇 |
2015年 | 93篇 |
2014年 | 107篇 |
2013年 | 297篇 |
2012年 | 324篇 |
2011年 | 279篇 |
2010年 | 195篇 |
2009年 | 245篇 |
2008年 | 248篇 |
2007年 | 258篇 |
2006年 | 278篇 |
2005年 | 232篇 |
2004年 | 201篇 |
2003年 | 214篇 |
2002年 | 126篇 |
2001年 | 103篇 |
2000年 | 90篇 |
1999年 | 79篇 |
1998年 | 100篇 |
1997年 | 75篇 |
1996年 | 68篇 |
1995年 | 68篇 |
1994年 | 60篇 |
1993年 | 60篇 |
1992年 | 35篇 |
1991年 | 51篇 |
1990年 | 40篇 |
1989年 | 34篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 14篇 |
1978年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 5篇 |
排序方式: 共有4697条查询结果,搜索用时 15 毫秒
31.
R. D. Rakhimov E. R. Milaeva O. V. Polyakova K. P. Butin 《Russian Chemical Bulletin》1994,43(2):289-292
A procedure for the alkylation of metallic mercury by (dimethylglyoximato)butylcobalt(III) electrochemically generated in the presence of butyl bromide is proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–312, February, 1994. 相似文献
32.
33.
Simple two-parameter Hückel and Pitzer equations were used for the calculation of the activity coefficients of aqueous hydrochloric acid at 25°C up to a molality of 2.0 mol-kg–1. The data obtained by Harned and Ehlers(12,13) from galvanic cells without liquid junction were used in the analysis and the parameters obtained were compared to those obtained from all reliable data presented in the literature for HCl at this temperature. A good agreement between the parameters was always observed. The activity coefficients obtained by the new equations were compared to those suggested by Robinson and Stokes,(8) Hamer and Wu,(1) and Pitzer and Mayorga,(9) and good agreement was also found. The data from the most important literature data sets for HCl were also predicted using the new activity coefficient equations, and the magnitude of the resulting errors was close to the precision of the measurements, the errors forming an almost random pattern for all data sets. 相似文献
34.
35.
Jordi Faraudo Alex Travesset 《Colloids and surfaces. A, Physicochemical and engineering aspects》2007,300(3):287-292
In this paper, we argue that many of the fascinating electrostatic effects that take place in amphiphilic systems are strongly related to the particular organization of the oxygen atoms within each individual molecule. In particular, we focus on two effects: charge inversion and dielectric overscreening. For that purpose, we present molecular dynamics simulations of phosphatidic acid (DMPA2−) in the presence of divalent counterions. Our results show that the many oxygens present in DMPA2− cooperatively create strong binding sites for counterions, which in some cases lead to charge inversion. We also present an analysis of the role of interfacial water and relate our analysis to the phenomenon of dielectric overscreening. Several experimental implications are discussed in the conclusions. 相似文献
36.
37.
根据CTP在离子交换树脂上的吸附容量和分离因数的大小,确定Duolite A-30树脂适合CTP与CDP,CMP之间的分离.对CTP在Duolite A-30树脂上的吸附动力学和热力学研究表明,在283.15K~303.15K之间,CTP的质量浓度在7.5g/L以上时,Duolite A-30树脂对CTP的吸附主要受颗粒扩散的控制,其有效扩散系数为D=3.47×10-7cm2/s,溶液的质量浓度≤1.0g/L时,CTP与Duolite A-30树脂之间的交换速率主要受液膜控制,其液膜扩散系数为Kf =4.112×10-4/s.同时测定了不同条件下三磷酸胞苷溶液在Duolite A-30树脂固定床离子交换柱中的穿透曲线,研究了进口浓度、进口流速、原料液温度、原料液的pH值及柱高对穿透曲线的影响.用二阶动力学推动力模型描述固定床动态过程,考察了轴向返混对穿透曲线的影响,并从穿透曲线回归得到总传质系数,模型计算值与实验数据符合良好. 相似文献
38.
Zhi-En Lin 《Journal of solid state chemistry》2006,179(3):723-728
A new layered cobalt-zinc phosphite, Co(H2O)4Zn4(HPO3)6·C2N2H10 has been synthesized in the presence of ethylenediamine as the structure-directing agent. The compound crystallizes in the monoclinic system, space group Cc (No. 9), a=18.2090(8), b=9.9264(7), c=15.4080(7) Å, β=114.098(4)°, V=2542.3(2) Å3, Z=4, R=0.0323, wR=0.0846. The structure consists of ZnO4 tetrahedra, CoO6 octahedra and HPO3 pseudopyramids through their vertices forming bimetallic phosphite layers parallel to the ab plane. Organic cations, which reside between the inorganic layers, are mobile and can be exchanged by NH4+ cations without the collapse of the framework. 相似文献
39.
用转换器和IBMPC/XT微机与Dionex2020i型离子色谱仪连接组成自动控制与数据处理系统,转换器由8031及8255等芯片组成,其功能是采集数据和转送数据,软件由汇编及C语言编制。这套新系统增加了注入/记录同步,分级梯度淋洗,自动连续进样等功能以及很强的数据处理能力。 相似文献
40.
The direct flow injection potentiometric (FIP) analysis of phosphate in hydroponic nutrient solution has been carried out using a cobalt-wire ion-selective electrode (ISE). Synthetic hydroponic nutrient solution, commercial hydroponic nutrient solution and working hydroponic farm nutrient solution were analysed for phosphate using the FIP technique. It is shown that FIP results compare favourably to standard methods of analysis such as spectrophotometry and indirect photometric ion-pair chromatography. Reproducible FIP response curves with a slope of −(47.57±0.03) mV per decade and intercept of −(169.7±0.1) mV were obtained for four separate calibrations in the concentration range 5.0×10−4–1.0×10−2 M H2PO4−. Anion corrections for interferences by Cl−, NO3− and SO42− were applied to all samples using the selectivity coefficients determined independently using a fixed interference method. Nevertheless, it was found that anion corrections were not necessary, as the deviations fell within the bounds of experimental error for the cobalt-wire ISE technique (i.e.±2–5% R.S.D.). The proposed FIP method enables the direct determination of phosphate in hydroponic nutrient solutions. 相似文献