全文获取类型
收费全文 | 24510篇 |
免费 | 253篇 |
国内免费 | 25篇 |
专业分类
化学 | 21315篇 |
晶体学 | 73篇 |
力学 | 129篇 |
数学 | 1567篇 |
物理学 | 1704篇 |
出版年
2014年 | 197篇 |
2013年 | 346篇 |
2012年 | 394篇 |
2011年 | 438篇 |
2010年 | 270篇 |
2009年 | 285篇 |
2008年 | 392篇 |
2007年 | 339篇 |
2006年 | 365篇 |
2005年 | 335篇 |
2004年 | 337篇 |
2003年 | 266篇 |
2002年 | 244篇 |
1988年 | 187篇 |
1987年 | 237篇 |
1986年 | 218篇 |
1985年 | 320篇 |
1984年 | 330篇 |
1982年 | 258篇 |
1981年 | 237篇 |
1980年 | 433篇 |
1979年 | 357篇 |
1978年 | 1155篇 |
1977年 | 889篇 |
1976年 | 327篇 |
1975年 | 207篇 |
1974年 | 170篇 |
1973年 | 207篇 |
1972年 | 176篇 |
1970年 | 185篇 |
1968年 | 229篇 |
1967年 | 204篇 |
1966年 | 267篇 |
1965年 | 271篇 |
1964年 | 245篇 |
1963年 | 190篇 |
1962年 | 363篇 |
1961年 | 183篇 |
1960年 | 229篇 |
1959年 | 217篇 |
1958年 | 214篇 |
1956年 | 246篇 |
1955年 | 229篇 |
1938年 | 175篇 |
1937年 | 235篇 |
1936年 | 220篇 |
1935年 | 237篇 |
1934年 | 189篇 |
1933年 | 262篇 |
1930年 | 221篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
We investigate congruence classes and direct congruence classes of m-tuples in the complex projective space ℂP
n
. For direct congruence one allows only isometries which are induced by linear (instead of semilinear) mappings. We establish
a canonical bijection between the set of direct congruence classes of m-tuples of points in ℂP
n
and the set of equivalence classes of positive semidefinite Hermitean m×m-matrices of rank at most n+1 with 1's on the diagonal. As a corollary we get that the direct congruence class of an m-tuple is uniquely determined by the direct congruence classes of all of its triangles, provided that no pair of points of
the m-tuple has distance π/2. Examples show that the situation changes drastically if one replaces direct congruence classes by
congruence classes or if distances π/2 are allowed. Finally we do the same
kind of investigation also for the complex hyperbolic space ℂH
n
. Most of the results are completely analogous, however, there are also some interesting differences.
Received: 15 January 1996 相似文献
2.
3.
Wolfram Bremser Roland Becker Heinrich Kipphardt Petra Lehnik-Habrink Ulrich Panne Antje Töpfer 《Accreditation and quality assurance》2006,11(10):489-495
ISO Guide 35 deals with RM stability issues and scrutinizes the evaluation of stability testing results under the assumption that either there is no trend at all (a rather rare situation), or any observed deterministic change is insignificant and thus can be neglected. However, market demands for reliable reference materials are obviously not limited to stable or at least seemingly stable materials. In many analytical applications, analytes and measurands under consideration are known, or at least suspected, to be unstable on time scales that may vary widely from measurand to measurand. The Federal Institute for Materials Research and Testing (BAM) has developed (and successfully uses) an integrated approach in its certification practice. The approach is based on an initial stability study and subsequent post-certification monitoring. Data evaluation is model-based and takes advantage of all information collected in the stability testing scheme(s). It thus allows one to deal with any kind of instability observed, to assess limiting time intervals at any stress condition in the range tested, to estimate a final expiry date for materials with detected instabilities or the maximum admissible re-testing interval for seemingly stable materials, and to assess maximum admissible stress loads during delivery of the material to the customer. The article describes (and exemplifies) typical study layout, the model selection, and the integrated data assessment. 相似文献
4.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
5.
Michel Weber 《Transactions of the American Mathematical Society》2006,358(2):911-936
We apply a majorizing measure theorem of Talagrand to obtain uniform bounds for sums of random variables satisfying increment conditions of the type considered in Gál-Koksma Theorems. We give some applications.
6.
O. Kortner M.P. Locher V.E. Markushin P. Weber O. Wigger 《The European Physical Journal C - Particles and Fields》2002,25(3):353-360
We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small
invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant
masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while
the stochastic HBT mechanism is not supported by the present findings.
Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002 相似文献
7.
Ohne Zusammenfassung 相似文献
8.
Ohne Zusammenfassung 相似文献
9.
Ohne Zusammenfassung 相似文献
10.
E. Ritsert und W. Lenz 《Fresenius' Journal of Analytical Chemistry》1889,28(1):749-750
Ohne Zusammenfassung 相似文献