全文获取类型
收费全文 | 79082篇 |
免费 | 6089篇 |
国内免费 | 9409篇 |
专业分类
化学 | 39032篇 |
晶体学 | 338篇 |
力学 | 6509篇 |
综合类 | 1320篇 |
数学 | 25021篇 |
物理学 | 22360篇 |
出版年
2024年 | 116篇 |
2023年 | 731篇 |
2022年 | 1478篇 |
2021年 | 1677篇 |
2020年 | 1850篇 |
2019年 | 2026篇 |
2018年 | 1678篇 |
2017年 | 1906篇 |
2016年 | 2223篇 |
2015年 | 2079篇 |
2014年 | 2913篇 |
2013年 | 5413篇 |
2012年 | 3405篇 |
2011年 | 3674篇 |
2010年 | 3194篇 |
2009年 | 4296篇 |
2008年 | 4812篇 |
2007年 | 5042篇 |
2006年 | 4727篇 |
2005年 | 4020篇 |
2004年 | 3732篇 |
2003年 | 3805篇 |
2002年 | 3454篇 |
2001年 | 2835篇 |
2000年 | 2773篇 |
1999年 | 2462篇 |
1998年 | 2265篇 |
1997年 | 1887篇 |
1996年 | 1690篇 |
1995年 | 1542篇 |
1994年 | 1406篇 |
1993年 | 1205篇 |
1992年 | 1159篇 |
1991年 | 890篇 |
1990年 | 743篇 |
1989年 | 627篇 |
1988年 | 576篇 |
1987年 | 439篇 |
1986年 | 386篇 |
1985年 | 443篇 |
1984年 | 437篇 |
1983年 | 217篇 |
1982年 | 343篇 |
1981年 | 403篇 |
1980年 | 306篇 |
1979年 | 292篇 |
1978年 | 222篇 |
1977年 | 207篇 |
1976年 | 154篇 |
1974年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
John A. McNaney Franz M. Zimmerman Howard K. Zimmerman 《Monatshefte für Chemie / Chemical Monthly》1984,115(8-9):1039-1045
The solubilities of potassium acetate and benzoate in aqueous 1,4-dioxane at a temperature of 85°C are reported together with a quasi-thermodynamic general treatment of the experimental results.This brief contribution is a second report upon the results of systematic solubility measurements, commenced with Ref.1, which have been performed by Dr.John A. McNaney during his abruptly truncated lifetime. 相似文献
992.
993.
Immobilized sulfhydryl groups were prepared by partial thiolation of NH2-glass beads. The microenvironment of the immobilized SH groups was varied by different chemical modifications of neighboring
NH2 groups. Introduction of a strong charge in the surroundings of immobilized sulfhydryls results in their dramatic stabilization
against autooxidation. This effect is due to the salting of O2 from the surface microlayer of the thiolated beads. 相似文献
994.
The Randić index of an organic molecule whose molecular graph is G is the sum of the weights (d(u)d(v))−1/2 of all edges uv of G, where d(u) and d(v) are the degrees of the vertices u and v in G. We give a sharp lower bound on the Randić index of conjugated trees (trees with a perfect matching) in terms of the number
of vertices. A sharp lower bound on the Randić index of trees with a given size of matching is also given
Mei Lu: Partially supported by NNSFC (No. 60172005)
Lian-zhu Zhang: Partially supported by NNSFC (No. 10271105)
Feng Tian: Partially supported by NNSFC (No. 10431020) 相似文献
995.
Hydrofluoric acid, added to seawater, can assist in the removal of chloride in the drying step by precipitating fluoride salts, thus suppressing the chloride interference effects induced on the atomization signals of Cu and Mn. By adding HF to seawater before the analysis, MgF2 and CaF2 are precipitated at the bottom of the sampling flask, without precipitating Cu and Mn, and are consequently not introduced into the graphite furnace. Because sodium salts are eliminated at the pretreatment step, the whole seawater matrix is eliminated before the atomization of Cu or Mn. Therefore, the analyzed volume of seawater can be increased by using the multi-injection procedure without degradation of the limit of detection and risks of spectral interferences. The limit of detection obtained for Cu and Mn are 0.05 and 0.01 μg L−1, respectively, for a 50 μL analyzed seawater volume. 相似文献
996.
Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e. in “industry”. The ensuing developments of FIA, encompassing sequential injection analysis (SIA) and bead injection lab-on-valve (BI-LOV), are described and their individual features discussed. Finally, some recent results of the activities from the author’s own research group are briefly mentioned. 相似文献
997.
998.
Hilary E. Kent Terence H. Lilley Peter J. Milburn Michael Bloemendal Gus Somsen 《Journal of solution chemistry》1985,14(2):101-115
Enthalpies of dilution of the N-acetyl amides of glycine, L-alanine, L-valine, L-leucine, and L-phenylalanine, dissolved in N,N-dimethylformamide (DMF) as a solvent have been measured at 25°C. The results obtained have been analyzed to give the enthalpic interaction (or virial) coefficients of the solutes and these are compared with information previously obtained in aqueous systems. There are marked differences in the interaction properties in the two solvents and, while the additivity approach of Savage and Wood is applicable to the solutes in water it is not suitable for representing the interactions in DMF. A correlation is presented between the enthalpic second virial coefficients in DMF and the propensity of side-chains to be in proximity in globular proteins. 相似文献
999.
Information content of data and variables and types of weighting in least-squares regression methods
Algorithms are given for evaluating the relative amount of useful information related to a particular parameter which is carried by individual data points and intervals of the variables. The algorithms provide an efficient means of using the information contained in a set of data. Applications to the optimization of weighting in regression methods are described. Several informational and combined informational-statistical types of weighting are studied as a means of improving the accuracy and precision of the parameters obtained by non-linear regression. 相似文献
1000.
In the process of bulk photopolymerization of styrene initiated by AIBN decomposition polyvinyl benzophenone (PVB) can supply an effective cage for triplet-triplet energy transfer between PVB macromolecules and small molecules of AIBN to influence the molecular weight of polystyrene in weak magnetic field (less than 0.035T), that was different from the case of polyvinyl naphthalene (PVN) which supplied cages for this system only in the stronger magnetic field (more than 0.2 T) studies. It was found that in the same conditions, PVN could exert more tremendous influences on the bulk photopolymerizatiou system of styrene than PVB because in the stronger magnetic field the triplet PVN had much longer life time than PVB. 相似文献