全文获取类型
收费全文 | 7188篇 |
免费 | 1436篇 |
国内免费 | 784篇 |
专业分类
化学 | 5671篇 |
晶体学 | 37篇 |
力学 | 190篇 |
综合类 | 100篇 |
数学 | 1978篇 |
物理学 | 1432篇 |
出版年
2024年 | 14篇 |
2023年 | 114篇 |
2022年 | 144篇 |
2021年 | 287篇 |
2020年 | 414篇 |
2019年 | 304篇 |
2018年 | 318篇 |
2017年 | 265篇 |
2016年 | 422篇 |
2015年 | 414篇 |
2014年 | 484篇 |
2013年 | 768篇 |
2012年 | 460篇 |
2011年 | 438篇 |
2010年 | 400篇 |
2009年 | 404篇 |
2008年 | 491篇 |
2007年 | 433篇 |
2006年 | 357篇 |
2005年 | 353篇 |
2004年 | 296篇 |
2003年 | 269篇 |
2002年 | 218篇 |
2001年 | 176篇 |
2000年 | 192篇 |
1999年 | 186篇 |
1998年 | 120篇 |
1997年 | 132篇 |
1996年 | 112篇 |
1995年 | 92篇 |
1994年 | 53篇 |
1993年 | 41篇 |
1992年 | 43篇 |
1991年 | 33篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1972年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有9408条查询结果,搜索用时 31 毫秒
31.
该文给出了帐篷映射产生的迭代序列Cesaro平均收敛的条件.研究了它与实数二进展式度量性质之间的联系. 相似文献
32.
33.
Summary In this note we use Theorem 2.4 in<span lang=EN-US style='font-size:10.0pt;mso-ansi-language:EN-US'>[1]to give a very short
proof of a recent result due to M. Bognár (Theorem A in [3]). We also prove that Bognár's result is in fact equivalent to
the classical Hahn-Mazurkiewicz Theorem. Finally we give generalizations in the non-compact setting. 相似文献
34.
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
35.
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
36.
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
37.
38.
A closed microwave digestion method followed by inductively coupled plasma spectrometric (ICP-MS) analysis was evaluated for the determination of trace impurities in photoresist. To optimize the digestion procedure, several digestion parameters such as acid, heating temperature and heating time were evaluated. Besides, the digestion efficiency of used photoresist material and the recovery of analyte elements obtained by the use of gravimetric method and ICP-MS measurement, individually, were also compared to clarify the completeness of digestion. According to our experiments, the gravimetric method was found to be not so relevant to the completeness of digestion, because the remaining sample matrix could cause suppression effect in the subsequent ICP-MS measurement. In view of minimizing blank value and working time, a simple single-step heating program was proposed to mineralize 0.25 ml of photoresist material with 5 ml of nitric acid at 180 °C for 10 min. Based on the comparative study of the analytical results obtained by instrumental neutron activation analysis (INAA) and proposed method, the reliability of proposed method for the determination of trace metallic impurities in photoresist material has been confirmed. 相似文献
39.
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
40.