全文获取类型
收费全文 | 10078篇 |
免费 | 152篇 |
国内免费 | 38篇 |
专业分类
化学 | 5754篇 |
晶体学 | 85篇 |
力学 | 352篇 |
数学 | 1632篇 |
物理学 | 2445篇 |
出版年
2022年 | 95篇 |
2021年 | 111篇 |
2020年 | 122篇 |
2019年 | 123篇 |
2018年 | 117篇 |
2017年 | 102篇 |
2016年 | 178篇 |
2015年 | 159篇 |
2014年 | 165篇 |
2013年 | 566篇 |
2012年 | 353篇 |
2011年 | 438篇 |
2010年 | 318篇 |
2009年 | 272篇 |
2008年 | 397篇 |
2007年 | 357篇 |
2006年 | 348篇 |
2005年 | 317篇 |
2004年 | 336篇 |
2003年 | 271篇 |
2002年 | 273篇 |
2001年 | 187篇 |
2000年 | 178篇 |
1999年 | 144篇 |
1998年 | 114篇 |
1997年 | 131篇 |
1996年 | 161篇 |
1995年 | 120篇 |
1994年 | 122篇 |
1993年 | 152篇 |
1992年 | 154篇 |
1991年 | 158篇 |
1990年 | 116篇 |
1989年 | 119篇 |
1988年 | 131篇 |
1987年 | 180篇 |
1986年 | 148篇 |
1985年 | 196篇 |
1984年 | 184篇 |
1983年 | 144篇 |
1982年 | 166篇 |
1981年 | 176篇 |
1980年 | 171篇 |
1979年 | 170篇 |
1978年 | 164篇 |
1977年 | 162篇 |
1976年 | 141篇 |
1975年 | 158篇 |
1974年 | 126篇 |
1973年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
L. Viaene D. Meerschaut M. Van Der Auweraer F. C. De Schryver F. Wilkinson 《Research on Chemical Intermediates》1995,21(7):711-723
The absorption and fluorescence of 16-(1-pyrene)-hexadecanoicacid adsorbed on silica have been investigated. Time-resolved transient diffuse reflectance spectra were recorded following pulsed nanosecond laser excitation at 355 nm of pyrene, 1-methylpyrene and 16-(1-pyrene)-hexadecanoicacid adsorbed on silica. In addition to a rapidly decaying transient, absorbing at 420 nm assigned as the triplet state, and of the radical cation, absorbing at 460 nm, another long living transient species absorbing at 420 nm was observed for 16-(1-pyrene)-hexadecanoic acid. The decay is reversible but complete recovery takes several hours. Although no definitive assignment could be made for this transient several possibilities are discussed. The radical cations of the investigated molecules are formed by a biphotonic process. The non-exponential decay of the radical cations could be analyzed in the framework of a Gaussian distribution of free energy barriers. 相似文献
72.
Fumio Watari J. Van Landuyt P. Delavignette S. Amelinckx 《Journal of solid state chemistry》1979,29(1):137-150
A study by means of electron microscopy at high resolution has enabled the analysis of the microstructure of hematite as produced by dehydration from goethite. The apparently “polycrystalline” structure is found to consist of aggregates of well-oriented twin-related hematite crystals, separated by regularly spaced H(001) walls of voids resulting from the loss of water. The material is thus broken up into blocks with sizes smaller than 50 Å. The crystallography of the twinned structure can be analyzed by electron diffraction data and dark-field imaging. These aggregates of hematite crystals provide an ideal mosaic structure. In particular the effect of this mosaic structure on the individual reflections of the diffraction patterns has been analyzed and discussed. 相似文献
73.
The uptake of several actinides [U(VI), Th(IV), Am(III), Cm(III)] and fission products was investigated from nitric acid solutions by two novel extraction chromatographic sorbents containing 2-(2-hexyloxy-ethyl)-N,N'-dimethyl-N,N'-dioctyl-malonamide (DMDOHEMA) and N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), respectively. The kinetics of the uptake of actinides was studied. The sorption of metal ions fromz simulated Low Level Liquid Waste (LLLW) solutions was evaluated. The results of these experiments revealed that the actinides and lanthanides could be separated from the bulk of other fission products in simulated LLLW solutions on both sorbents.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
74.
Experimental investigations on binary liquid mixtures near the critical mixing point are presently leading to a controversy about the anomaly in the thermal conductivity. A photopyroelectric technique is used to determine the thermal conductivity and the effusivity of the binary liquid mixture n-butoxyethanol-water at its critical concentration near the critical mixing point. It is proven that, contrary to previous reports, there is no critical enhancement in the thermal conductivity. The specific heat capacity is calculated from these results and compared with the results from measurements performed by adiabatic scanning calorimetry. 相似文献
75.
J.C.M. De Wit W.H. Van Riemsdijk M.M. Nederlof D.G. Kinniburgh L.K. Koopal 《Analytica chimica acta》1990
Humic substances are characterized by a variable electric potential and by a variety of binding sites leading to chemical heterogeneity. Binding of ions to these substances is influenced by both factors. A methodology based on acid—base titrations at several salt levels is presented that allows for the assessment of an appropriate electrostatic double-layer model and the intrinsic proton affinity distribution. The double-layer model is used for the conversion of pH to pHS for each data point, where HS is the proton concentration in the diffuse layer near the binding site. It is shown that with an appropriate double-layer model the proton binding curves at different salt levels converge into one “master curve” when plotted as a function of pHS. The intrinsic proton affinity distribution can then be derived from the “master curve” using the LOGA method. A rigorous analysis of metal binding to humic substances is complex and in practice is not feasible. Under two different (simplifying) assumptions, namely fully coupled and uncoupled binding, it is shown how intrinsic metal ion affinity distributions can be obtained. Model calculations show that apparent metal ion affinity distributions do not resemble the intrinsic metal ion affinity distribution. 相似文献
76.
77.
78.
V. N. Fedoseyev Y. Jading O. C. Jonsson R. Kirchner K. -L. Kratz M. Krieg E. Kugler J. Lettry T. Mehren V. I. Mishin H. L. Ravn T. Rauscher F. Scheerer O. Tengblad P. Van Duppen A. Wöhr 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):9-10
The continuum part of the6Li (a,a)6Li (1.47–2.47 MeV) scattering data at Ea=50 MeV are extracted in two discretized bins. Coupled-channel calculations are carried out coupling the 1+ ground state of6Li with both the resonant, 3+
1 state, and two non-resonant continuum states. The discretized continuum of the6Li (p,p)6Li (1.75–3.25 MeV) scattering data at Ep=65 MeV are also analysed on the same footing. In both the cases the effect of coupling is found to be minimal. 相似文献
79.
80.