全文获取类型
收费全文 | 13154篇 |
免费 | 2395篇 |
国内免费 | 3087篇 |
专业分类
化学 | 10711篇 |
晶体学 | 322篇 |
力学 | 703篇 |
综合类 | 286篇 |
数学 | 1869篇 |
物理学 | 4745篇 |
出版年
2024年 | 11篇 |
2023年 | 107篇 |
2022年 | 308篇 |
2021年 | 324篇 |
2020年 | 376篇 |
2019年 | 484篇 |
2018年 | 368篇 |
2017年 | 487篇 |
2016年 | 531篇 |
2015年 | 697篇 |
2014年 | 780篇 |
2013年 | 1034篇 |
2012年 | 1188篇 |
2011年 | 1195篇 |
2010年 | 1027篇 |
2009年 | 1061篇 |
2008年 | 1204篇 |
2007年 | 1086篇 |
2006年 | 959篇 |
2005年 | 889篇 |
2004年 | 714篇 |
2003年 | 522篇 |
2002年 | 617篇 |
2001年 | 554篇 |
2000年 | 428篇 |
1999年 | 281篇 |
1998年 | 212篇 |
1997年 | 168篇 |
1996年 | 148篇 |
1995年 | 120篇 |
1994年 | 130篇 |
1993年 | 100篇 |
1992年 | 93篇 |
1991年 | 70篇 |
1990年 | 82篇 |
1989年 | 55篇 |
1988年 | 59篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 29篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1971年 | 2篇 |
1936年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
1.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
2.
Li Quanxin Li Zheng He Cheng Sun Huilin Tan Shengheng Zhang Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2105-2115
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with... 相似文献
3.
In this article,we study the initial boundary value problem of coupled semi-linear degenerate parabolic equations with a singular potential term on manifolds with corner singularities.Firstly,we introduce the corner type weighted p-Sobolev spaces and the weighted corner type Sobolev inequality,the Poincare′inequality,and the Hardy inequality.Then,by using the potential well method and the inequality mentioned above,we obtain an existence theorem of global solutions with exponential decay and show the blow-up in finite time of solutions for both cases with low initial energy and critical initial energy.Significantly,the relation between the above two phenomena is derived as a sharp condition.Moreover,we show that the global existence also holds for the case of a potential well family. 相似文献
4.
5.
Over the past two decades, advanced materials with hollow interiors have received significant attention in materials research owing to their great application potential across a vast number of technological fields. Though with great difficulty, multi-shelled hollow metal–organic frameworks (MSHMs) have also been successfully synthesized in recent years. Herein, a rational shell-by-shell soft-templating protocol has been devised to fabricate highly uniform multi-shelled hollow cobalt-imidazole-based MOF (ZIF-67). For the first time, it has become possible to endow mesoporosity to this new type of functional material (i.e., mesoporous MOFs). When used as carrier materials in catalytic reactions, in principle, these mesoporous MSHMs with high surface area not only improve the dispersity of metal nanoparticles (NPs), but also efficiently facilitate the mass diffusion of the reactions, resulting in enhanced catalyst activity. Moreover, the obtained MSHMs/M nanocomposites serve as base-metal bifunctional catalysts for one-pot oxidation-Knoevenagel condensation cascade reaction, in which the MSHMs itself serves as a pristine active catalyst in addition to its role of catalyst support. The results demonstrate that excellent multifunctional catalysts can be achieved via preparing intrinsically microporous bulk MOFs into extrinsically mesoporous MSHMs which possess many structural merits that conventional bulk MOFs do not have. 相似文献
6.
针对传统红外图像增强算法中细节模糊及过度增强的问题,提出了一种基于Retinex理论与概率非局部均值相结合的红外图像增强方法.首先通过单尺度Retinex方法调整图像中过暗与过亮部分的灰度级;然后利用概率非局部均值对图像进行分解处理得到基本层与细节层,对基本层采用直方图均衡化拉伸对比度,对细节层采用非线性函数进行增强;最后,将不同层次的结果融合得到对比度与细节增强的红外图像.用该方法对多组不同场景的红外图像进行仿真实验,并将其与多种增强方法进行主、客观对比分析,结果表明所提方法在红外图像的细节及对比度增强方面都获得了更好的效果. 相似文献
7.
8.
9.
中国科学院近代物理研究所正在进行国际首台45 GHz全铌三锡超导离子源FECR(Fourth Electron Cyclotron Resonance)磁体的研制,该离子源磁体线圈由六个铌三锡超导六极线圈和四个铌三锡超导螺线管线圈组成。由于单根超导线绕制异形六极线圈(非标准鞍型)技术难度大,且铌三锡超导性能对应力敏感,为了测试单个铌三锡六极线圈性能能否达到设计指标,基于铝合金壳层结构和Bladder-Key精确预紧技术,设计了镜像磁场约束结构。本工作主要阐述了运用ANSYS参数化设计编程对镜像磁场结构进行优化设计的过程和优化后的镜像磁场结构,确定了室温预应力大小,并给出了线圈经过室温预紧、冷却降温和加电励磁后的最大等效应力。进一步结合实际六极线圈制作公差(±0.1 mm),分析和评估了公差对镜像磁场结构中六极线圈预应力施加的影响。 相似文献
10.
Bijian Lan Chunming Liu Xiang Yin Hua Zhang Wei Xu Zhongyi Hua 《Frontiers of Chemistry in China》2006,1(3):296-299
Organic materials of D-π-A type MR-X (MR-1: p-dimethylaminophenylethenetrica-rbonitrile and MR-2: p-diphenylaminophenylethene tricarbonitrile) were designed and synthesized. The device with a sandwich structure shows good
rectificative phenomena. The highest rectification ratio 10000 was achieved in device Cu/MR-1/Ag, and about 100 in other device
M/MR-X/M (M: Cu, Ag). It has been found that rectificative phenomena exist only in the atmosphere-liquid interface region
by means of liquid adsorption, and electric field could help form the oriented molecular film.
__________
Translated from Journal of Fudan University (Natural Science), 2005, 44(4) (in Chinese) 相似文献