全文获取类型
收费全文 | 57006篇 |
免费 | 7109篇 |
国内免费 | 5820篇 |
专业分类
化学 | 26340篇 |
晶体学 | 583篇 |
力学 | 2106篇 |
综合类 | 395篇 |
数学 | 3900篇 |
物理学 | 14171篇 |
综合类 | 22440篇 |
出版年
2024年 | 183篇 |
2023年 | 1022篇 |
2022年 | 1600篇 |
2021年 | 1866篇 |
2020年 | 1971篇 |
2019年 | 1730篇 |
2018年 | 1522篇 |
2017年 | 1559篇 |
2016年 | 2120篇 |
2015年 | 2346篇 |
2014年 | 3130篇 |
2013年 | 3693篇 |
2012年 | 4372篇 |
2011年 | 4531篇 |
2010年 | 3423篇 |
2009年 | 3455篇 |
2008年 | 3779篇 |
2007年 | 3511篇 |
2006年 | 3072篇 |
2005年 | 2481篇 |
2004年 | 1976篇 |
2003年 | 1539篇 |
2002年 | 1403篇 |
2001年 | 1260篇 |
2000年 | 1222篇 |
1999年 | 1563篇 |
1998年 | 1224篇 |
1997年 | 1200篇 |
1996年 | 1104篇 |
1995年 | 955篇 |
1994年 | 894篇 |
1993年 | 787篇 |
1992年 | 693篇 |
1991年 | 626篇 |
1990年 | 550篇 |
1989年 | 443篇 |
1988年 | 372篇 |
1987年 | 241篇 |
1986年 | 208篇 |
1985年 | 116篇 |
1984年 | 44篇 |
1983年 | 45篇 |
1982年 | 41篇 |
1981年 | 23篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1975年 | 2篇 |
1957年 | 9篇 |
1955年 | 4篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
351.
朱怀平 《南京师大学报(自然科学版)》1994,17(2):1-9,13
研究了临界情形的拟线性二阶方程组的狄利克雷问题,证明了狄利克雷问题解的存在唯一性,并给出解的渐近展开式及余项,估计式. 相似文献
352.
353.
本文利用变分方法推出了矩形管道中完全发展段层流流动的速度,继而讨论了矩形管道中的流量、沿程阻力系数和压力损失等。实验结果表明,本文的分析是可靠的。 相似文献
354.
The article referenced above was first published online on 7 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
355.
We reported controllable synthesis of ZnS nanocrystal-polymer transparent hybrids by using polymethylmethacrylate (PMMA) as
a polymer matrix. In a typical run, the appropriate amounts of zinc chloride (ZnCl2) and sodium sulfide (Na2S) in the presence of 2-mercaptoethanol (ME) as the organic ligand were well dispersed in H2O/dimethylformamide solution without any aggregation. In addition, the Mn-doped ZnS nanocrystals (NCs) were synthesized with
similar method. Then, ZnS-PMMA hybrids were obtained via free radical polymerization in situ by using ZnS NCs functionalized
with methacryloxypropyltrimethoxysilane (MPS). FT-IR characterization indicates the formation of robust bonding between ZnS
NCs and the organic ligand. The TEM images show that ZnS NCs are well dispersed in PMMA matrix, and particle size of as-prepared
ZnS NCs is about 2.6 nm, in agreement with the computing results of Brus’s model and Debye–Scherrer formula. The photoluminescence
measurements present that ZnS NCs, Mn-doped ZnS NCs, and ZnS/PMMA hybrid show good optical properties. 相似文献
356.
357.
Frame Wavelets with Compact Supports for L^2(R^n) 总被引:1,自引:0,他引:1
De Yun YANG King Wei ZHOU Zhu Zhi YUAN 《数学学报(英文版)》2007,23(2):349-356
The construction of frame wavelets with compact supports is a meaningful problem in wavelet analysis. In particular, it is a hard work to construct the frame wavelets with explicit analytic forms. For a given n × n real expansive matrix A, the frame-sets with respect to A are a family of sets in R^n. Based on the frame-sets, a class of high-dimensional frame wavelets with analytic forms are constructed, which can be non-bandlimited, or even compactly supported. As an application, the construction is illustrated by several examples, in which some new frame wavelets with compact supports are constructed. Moreover, since the main result of this paper is about general dilation matrices, in the examples we present a family of frame wavelets associated with some non-integer dilation matrices that is meaningful in computational geometry. 相似文献
358.
359.
Suoyuan Lian Lei Gao Zhenhui Kang Di Wu Yang Lan Lin Xu 《Solid State Communications》2004,132(6):375-378
Single-crystal magnetite nanowires with average diameter of ca. 20 nm and length of up to several micrometers were prepared by a simple alkaline surfactant-free hydrothermal process. The crystallinity, purity, morphology, and structural features of the as-prepared magnetite nanowires were investigated by powder X-ray diffraction, transmission electron microscopy (TEM) and selected area electron diffraction. The composition and length of nanowires depends on the pH, with higher pH favoring longer nanowires composed entirely of Fe3O4. A mechanism for nanowire growth is proposed. 相似文献
360.
Hydroxyapatite coating on porous silicon substrate obtained by precipitation process 总被引:2,自引:0,他引:2
Chen Shaoqiang Zhu Ziqiang Zhu Jianzhong Zhang Jian Shi Yanling Yu Ke Wang Weiming Wang Xiaohua Feng Xiao Luo Laiqiang Shao Li 《Applied Surface Science》2004,230(1-4):418-424
Hydroxyapatite Ca10(PO4)6(OH)2 (HAP) is known as a bioactive and biocompatible material, HAP coatings were used to improve the biocompatible of substrate by many researcher, In this work, HAP thin films on porous silicon (PS) substrates have been prepared by aqueous precipitation method with rapid thermal annealing (RTA) processes. The HAP films had been prepared under the annealing temperature ranging from 300 to 1000 °C. By the measurement of X-ray diffraction (XRD), it was found that for the crystallinity optimization, the heat-treatment at 850–950 °C for 1 h would be favorable. Atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements reveal a dense and smooth surface of the HAP film, and tightly adherence of the coating on porous silicon substrate after sintered. Thus, by this method, porous silicon could be increased its bioactivity and so that could be used in the biomedical area. 相似文献