全文获取类型
收费全文 | 9547篇 |
免费 | 969篇 |
国内免费 | 905篇 |
专业分类
化学 | 1467篇 |
晶体学 | 60篇 |
力学 | 552篇 |
综合类 | 111篇 |
数学 | 2143篇 |
物理学 | 2523篇 |
综合类 | 4565篇 |
出版年
2024年 | 25篇 |
2023年 | 92篇 |
2022年 | 169篇 |
2021年 | 173篇 |
2020年 | 215篇 |
2019年 | 212篇 |
2018年 | 208篇 |
2017年 | 259篇 |
2016年 | 318篇 |
2015年 | 312篇 |
2014年 | 439篇 |
2013年 | 642篇 |
2012年 | 531篇 |
2011年 | 590篇 |
2010年 | 466篇 |
2009年 | 547篇 |
2008年 | 570篇 |
2007年 | 680篇 |
2006年 | 626篇 |
2005年 | 484篇 |
2004年 | 448篇 |
2003年 | 405篇 |
2002年 | 378篇 |
2001年 | 315篇 |
2000年 | 351篇 |
1999年 | 293篇 |
1998年 | 246篇 |
1997年 | 218篇 |
1996年 | 191篇 |
1995年 | 171篇 |
1994年 | 127篇 |
1993年 | 120篇 |
1992年 | 105篇 |
1991年 | 104篇 |
1990年 | 82篇 |
1989年 | 76篇 |
1988年 | 77篇 |
1987年 | 38篇 |
1986年 | 33篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1957年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
41.
Adhesion of zein to solid substrates has been studied using surface energy profiles as indices and by adhesion mapping using
atomic force microscopy (AFM). Different plasticizers like glycerol and sorbitol have been used to form mixed films with zein
and properties of these films are studied using surface energy profiles. Comparison of the results from the different mixed
samples with those from the pure zein films showed that force mapping could identify areas rich in protein. The adhesion maps
produced were deconvoluted from sample topography and contrasted with the data obtained from contact angle measurements. A
comparison of the two methods shows that the extent of contact angle hysteresis is indicative of both hydrophobicity of the
surface as well as the force of adhesion. Mechanical properties and microstructure of zein films prepared by casting from
solutions and using Langmuir-Blodgett film technique have been investigated. Pure zein seemed brittle and exhibited an essentially
linear relationship between stress and strain. Films with plasticizer were tougher than these films. In general, mixed films
showed better mechanical properties than pure films and had higher ultimate tensile strength and increased per cent elongation.
Further, the mixed films of zein showed a higher force of adhesion compared to the pure films. 相似文献
42.
A planar map is a 2-cell embedding of a connected planar graph, loops and parallel edges allowed, on the sphere. A plane map is a planar map with a distinguished outside (“infinite”) face. An unrooted map is an equivalence class of maps under orientation-preserving homeomorphism, and a rooted map is a map with a distinguished oriented edge. Previously we obtained formulae for the number of unrooted planar n-edge maps of various classes, including all maps, non-separable maps, eulerian maps and loopless maps. In this article, using the same technique we obtain closed formulae for counting unrooted plane maps of all these classes and their duals. The corresponding formulae for rooted maps are known to be all sum-free; the formulae that we obtain for unrooted maps contain only a sum over the divisors of n. We count also unrooted two-vertex plane maps. 相似文献
43.
We propose iteration methods for solving the Dirichlet problem in domains with involved geometry. Such problems arise in relation to the problem of optimizing quantum dot and antidot infrared detectors. We estimate the deviation of an approximate solution from the exact solution. 相似文献
44.
Let X be a metric space, B the σ-algebra of Borel subsets of X, and μ a probability measure on (X,B). In this note, for a measure-preserving map T (respectively a measure-preserving semi-flow φ) on (X,B,μ), we prove that if suppμ=X, and T (respectively φ) is weak-mixing, then T (respectively φ) has sensitive dependence. 相似文献
45.
46.
47.
Benson真有效意义下集值优化的广义最优性条件 总被引:12,自引:0,他引:12
本文引入了关于集值映射的α-阶Clarke切导数、α-阶邻接切导数及α-阶 伴随切导数的概念,借此建立了约束向量集值优化Benson真有效解导数型的Kuhn- Tucker条件. 相似文献
48.
49.
Nicholas Buchdahl 《Annals of Global Analysis and Geometry》2003,23(2):189-204
The classical conjectures of Weil on K3 surfaces – that the set of suchsurfaces is connected; that a version of the Torelli theorem holds; thateach such surface is Kähler; and that the period map issurjective – are reconsidered in the light of a generalisation of theNakai–Moishezon criterion, and short proofs of all the conjectures aregiven. Most of the proofs apply equally or with minor variation tocomplex 2-tori, the only other compact Kähler surfaces with trivialcanonical bundle. 相似文献
50.
舒惠霞 《陕西理工学院学报(自然科学版)》2003,19(1):48-48
针对光栅衍射实验中出现的操作问题,简述了仪器调节不满足计算公式成立的条件时,引起的测量误差,并给出了正确的做法。 相似文献