全文获取类型
收费全文 | 10103篇 |
免费 | 258篇 |
国内免费 | 21篇 |
专业分类
化学 | 6753篇 |
晶体学 | 60篇 |
力学 | 107篇 |
综合类 | 1篇 |
数学 | 1280篇 |
物理学 | 2181篇 |
出版年
2021年 | 72篇 |
2020年 | 111篇 |
2019年 | 90篇 |
2018年 | 69篇 |
2016年 | 156篇 |
2015年 | 165篇 |
2014年 | 186篇 |
2013年 | 297篇 |
2012年 | 379篇 |
2011年 | 441篇 |
2010年 | 290篇 |
2009年 | 266篇 |
2008年 | 420篇 |
2007年 | 387篇 |
2006年 | 410篇 |
2005年 | 366篇 |
2004年 | 375篇 |
2003年 | 306篇 |
2002年 | 272篇 |
2001年 | 200篇 |
2000年 | 170篇 |
1999年 | 160篇 |
1998年 | 142篇 |
1997年 | 144篇 |
1996年 | 166篇 |
1995年 | 159篇 |
1994年 | 171篇 |
1993年 | 157篇 |
1992年 | 173篇 |
1991年 | 142篇 |
1990年 | 115篇 |
1989年 | 108篇 |
1988年 | 119篇 |
1987年 | 122篇 |
1986年 | 123篇 |
1985年 | 148篇 |
1984年 | 153篇 |
1983年 | 100篇 |
1982年 | 140篇 |
1981年 | 146篇 |
1980年 | 125篇 |
1979年 | 118篇 |
1978年 | 129篇 |
1977年 | 96篇 |
1976年 | 110篇 |
1975年 | 100篇 |
1974年 | 72篇 |
1973年 | 113篇 |
1972年 | 59篇 |
1971年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Georg von Georgievics 《Monatshefte für Chemie / Chemical Monthly》1885,6(1):754-759
Ohne ZusammenfassungDiese Untersuchung ist vor mehr als Jahresfrist infolge Eintrittes in die chemische Praxis abgebrochen worden. Äussere Verhältnisse machen die Vollendung der begonnenen Versuche auch weiterhin unmöglich und sehe ich mich desshalb veranlasst, meine Beobachtungen zu veröffentlichen. 相似文献
14.
W. von Oertzen 《Acta Physica Hungarica A》2003,18(2-4):157-170
Nuclear clustering in N = Z nuclei has been studied for many decades. Of particular relevance are states close to the decay thresholds, as described by the Ikeda diagram. Recent interest has focused on loosely bound systems as observed with exotic nuclei. Extreme deformations are simultaneously observed. In the deformed shell model these are referred to as super- and hyper-deformation. Another feature related to clustering is the development of octupole deformations. A possible approach to describe these states is to use explicitly molecular concepts, with neutrons in covalent binding orbits. Examples for molecular structure in beryllium isotopes and in other neutron-rich light nuclei (carbon and neon) are now well established. The predicted chain states in the carbon isotopes are the first example of structures with an axis ratio of 3:1. A threshold diagram for molecular configurations in nuclei with clusters and covalent neutrons can be established. 相似文献
15.
Gottfried Mayer Vitali Vogel Bas G. G. Lohmeijer Jean‐Franois Gohy Jacomina A. Van Den Broek Winfried Haase Ulrich S. Schubert Dieter Schubert 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4458-4465
Micelles prepared from amphiphilic block copolymers in which a poly(styrene) segment is connected to a poly(ethylene oxide) block via a bis‐(2,2′:6′,2″‐terpyridine‐ruthenium) complex have been intensely studied. In most cases, the micelle populations were found to be strongly heterogeneous in size because of massive micelle/micelle aggregation. In the study reported in this article we tried to improve the homogeneity of the micelle population. The variant preparation procedure developed, which is described here, was used to prepare two “protomer”‐type micelles: PS20‐[Ru]‐PEO70 and PS20‐[Ru]‐PEO375. The dropwise addition of water to a solution of the compounds in dimethylformamide was replaced by the controlled addition of water by a syringe pump. The resulting micelles were characterized by sedimentation velocity and sedimentation equilibrium analyses in an analytical ultracentrifuge and by transmission electron microscopy of negatively stained samples. Sedimentation analysis showed virtually unimodal size distributions, in contrast to the findings on micelles prepared previously. PS20‐[Ru]‐PEO70 micelles were found to have an average molar mass of 318,000 g/mol (corresponding to 53 protomers per micelle, which is distinctly less than after micelle preparation by the standard method) and an average hydrodynamic diameter (dh) of 18 nm. For PS20‐[Ru]‐PEO375 micelles, the corresponding values were M = 603,000 g/mol (31 protomers per micelle) and dh = 34 nm. The latter particles were found to be identical to the “equilibrium” micelles prepared in pure water. Both micelle types had a very narrow molar mass distribution but a much broader distribution of s values and thus of hydrodynamic diameters. This indicates a conformational heterogeneity that is stable on the time scale of sedimentation velocity analysis. The findings from electron microscopy were in disagreement with those from the sedimentation analysis both in average micelle diameter and in the width of the distributions, apparently because of imperfections in the staining procedure. The preparation procedure described also may be useful in micelle formation from other types of protomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4458–4465, 2004 相似文献
16.
17.
18.
19.
W. von der Linden 《Applied Physics A: Materials Science & Processing》1995,60(2):155-165
The reconstruction of physical quantities from (computer-) experimental data is very often hampered by the presence of noise, insufficient information and above all by the ill-posed nature of the underlying inversion problem. It will be demonstrated that the maximum entropy concepts is particularly suited for this type of data-analysis problems. It is based on Bayesian statistics and provides a consistent probabilistic theory to obtain unbiased results, independent of any model assumptions. This is particularly desirable if there is no additional information to justify these hypotheses. If, on the other hand, additional prior knowledge is available, it can be effectively incorporated into the computation, leading to more stringent confidence intervals. 相似文献
20.