全文获取类型
收费全文 | 14599篇 |
免费 | 266篇 |
国内免费 | 73篇 |
专业分类
化学 | 8288篇 |
晶体学 | 105篇 |
力学 | 503篇 |
数学 | 2004篇 |
物理学 | 4038篇 |
出版年
2022年 | 97篇 |
2021年 | 117篇 |
2020年 | 166篇 |
2019年 | 114篇 |
2018年 | 121篇 |
2017年 | 92篇 |
2016年 | 199篇 |
2015年 | 214篇 |
2014年 | 251篇 |
2013年 | 531篇 |
2012年 | 572篇 |
2011年 | 728篇 |
2010年 | 409篇 |
2009年 | 360篇 |
2008年 | 618篇 |
2007年 | 680篇 |
2006年 | 674篇 |
2005年 | 701篇 |
2004年 | 572篇 |
2003年 | 451篇 |
2002年 | 417篇 |
2001年 | 412篇 |
2000年 | 378篇 |
1999年 | 224篇 |
1998年 | 200篇 |
1997年 | 194篇 |
1996年 | 252篇 |
1995年 | 229篇 |
1994年 | 212篇 |
1993年 | 256篇 |
1992年 | 235篇 |
1991年 | 218篇 |
1990年 | 177篇 |
1989年 | 179篇 |
1988年 | 205篇 |
1987年 | 187篇 |
1986年 | 144篇 |
1985年 | 194篇 |
1984年 | 186篇 |
1983年 | 139篇 |
1982年 | 177篇 |
1981年 | 155篇 |
1980年 | 154篇 |
1979年 | 152篇 |
1978年 | 158篇 |
1977年 | 122篇 |
1976年 | 142篇 |
1975年 | 106篇 |
1974年 | 120篇 |
1973年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
B. J. A. Haring W. van Delft C. M. Bom 《Fresenius' Journal of Analytical Chemistry》1982,310(3-4):217-223
Summary A colorimetric field method for the determination of As and Sb was compared with atomic absorption (AA) techniques using both graphite furnace atomic absorption and the hydride generating technique with the heated quartz cell.During the intercomparison experiments the importance of the addition of KI before the addition of the NaBH4 reagent to the sample was clearly demonstrated. Compared with the colorimetric technique the AA hydride technique with the heated quartz cell was found to suffer from interferences by other hydride forming elements. Slow addition of NaBH4 (5 min in case of the colorimetric method) results in a longer reaction time giving a complete transformation of the hydride forming elements. The work also includes the optimization of various analytical parameters with respect to the hydride technique.
Bestimmung von Arsen und Antimon im Wasser und Boden durch Natriumborhydrid-Reduktion und Atomabsorptionsspektrometrie
Zusammenfassung Eine colorimetrische Feldmethode wird mit den Labormethoden der Atomabsorptionsspektrometrie verglichen, wobei sowohl auf die Quarzrohrmethode als auch die Graphitofenmethode eingegangen wird.Nachgewiesen wird, da\ den Proben Kaliumiodid zugesetzt werden mu\, um störende Einflüsse anderer Metalle auf die Reaktion von As und Sb mit NaBH4 zu verhindern. Im Vergleich zu der colorimetrischen Technik wurde bei der Hydridmethode, mit Atomisierung im hei\en Quarzrohr, eine störende Wirkung anderer hydridbildender Elemente festgestellt.Bei der colorimetrischen Methode lÄ\t sich dieser Störungseinflu\ durch langsame Zugabe von NaBH4 vermindern (5 min). Die Optimalisierung von Parametern bei der Hydridmethode zur Asund Sb-Bestimmung wird beschrieben.相似文献
962.
The problem of a particle moving in a two-valued random potential occurred in a recent paper by Pomeau. The exact time-dependent solution is here obtained for a quadratic potential by two different methods. The first method treats the problem as a stochastic differential equation and leads to the characteristic function of the probability distribution of the particle coordinate. In the second method the equation for the joint probability density of particle and potential is solved, which leads to the temporal Laplace transform of the distribution. The spectral properties of the evolution operator are examined. 相似文献
963.
G. A. Timmer F. Meurders P. J. Brussaard J. F. A. van Hienen 《Zeitschrift für Physik A Hadrons and Nuclei》1978,288(1):83-96
Electromagnetic transition rates and logft values were calculated for transitions between positive-parity states in theA=24?28 mass region. The wave functions used were taken from a previous paper. In general we found satisfactory agreement with experiment. In order to have a measure of the stability of the results against changes in the Hamiltonian a method was developed for assigning errors to calculated transition properties. The renormalized single-particle matrix elements of theE2 andM 1 transition operators were determined in a phenomenological way. To this end use was made of the errors just mentioned. It was found that good agreement was obtained with bare-nucleonM 1 singleparticle matrix elements and a state independent effective isoscalar charge for theE 2 operator. Predictions for static moments are given. 相似文献
964.
Summary An apparatus is described for the determination of hydrogen and deuterium in zircaloy by vacuum extraction at 1000–1100 C and mass spectrometry. The procedure is given in detail and items like blanks, sensitivity, reproducibility, and isotope effects are discussed.
Bestimmung von Wasserstoff und Deuterium in Zircaloy durch Vakuumextraktion und Massenspektrometrie
Zusammenfassung Eine apparative Anordnung zur H- und D-Bestimmung in Zircaloy durch Vakuumextraktion bei 1000–1100° C und anschließende massenspektrometrische Messung wird beschrieben. Blindwerte, Empfindlichkeit, Reproduzierbarkeit und Isotopeneffekte werden diskutiert.相似文献
965.
We report two-pulse photon echo decay and free induction decay measurements of iodine as a function of noble-gas pressure. The non-exponential behavior of the two-pulse photon echo decay which in contrast to the free induction decay shows a t3 dependence, is extensively discussed. A comparison with the results of the three-pulse stimulated echo measurements is made. The results are interpretated in terms of a quantum mechanical transport equation, and analytical expressions are derived for the three-pulse stimulated echo, two-pulse echo and free induction decay. 相似文献
966.
967.
The compound YNi3 () is ferromagnetic below Tc = 35 K. After hydrogen absorption it loses its ferromagnetic character and becomes Pauli paramagnetic. The composition of the ternary hydride is approximately YNi3H4. The lattice constants are , . 相似文献
968.
E. W. C. van Groesen 《Flow, Turbulence and Combustion》1981,37(1-2):53-65
969.
970.
J. van der Hurk Tj. Hollander C.Th.J. Alkemade 《Journal of Quantitative Spectroscopy & Radiative Transfer》1974,14(11):1167-1178
Experiments are described to yield more decisive information about the excitation energies of visible strontium monohydroxide bands appearing in flames. Excitation energy differences are derived directly from the ratio of thermal band intensities measured as a function of temperature. Absolute excitation energies are derived from the temperature dependence of the ratio of thermal band to strontium line intensity, while assuming a value for the dissociation energy of SrOH. Flames with temperatures ranging from 1907 to 2886 K were used. A level diagram is proposed for the strontium bands at 6060, 6470, 6690, and 6820 Å. From the results obtained, two conclusions may be drawn: (i) the bands considered are non-resonance bands and (ii) the uncertainty in the excitation energy as a result of the unknown molecular configuration is 0·25 eV. 相似文献