全文获取类型
收费全文 | 74049篇 |
免费 | 15956篇 |
国内免费 | 6224篇 |
专业分类
化学 | 67887篇 |
晶体学 | 808篇 |
力学 | 2869篇 |
综合类 | 284篇 |
数学 | 6649篇 |
物理学 | 17732篇 |
出版年
2024年 | 34篇 |
2023年 | 829篇 |
2022年 | 910篇 |
2021年 | 1465篇 |
2020年 | 2803篇 |
2019年 | 3990篇 |
2018年 | 2371篇 |
2017年 | 1867篇 |
2016年 | 5092篇 |
2015年 | 5232篇 |
2014年 | 5458篇 |
2013年 | 6824篇 |
2012年 | 6600篇 |
2011年 | 5878篇 |
2010年 | 5295篇 |
2009年 | 5206篇 |
2008年 | 4976篇 |
2007年 | 4170篇 |
2006年 | 3684篇 |
2005年 | 3491篇 |
2004年 | 2893篇 |
2003年 | 2490篇 |
2002年 | 3266篇 |
2001年 | 2253篇 |
2000年 | 2052篇 |
1999年 | 1298篇 |
1998年 | 806篇 |
1997年 | 752篇 |
1996年 | 693篇 |
1995年 | 567篇 |
1994年 | 489篇 |
1993年 | 370篇 |
1992年 | 366篇 |
1991年 | 336篇 |
1990年 | 263篇 |
1989年 | 213篇 |
1988年 | 150篇 |
1987年 | 149篇 |
1986年 | 139篇 |
1985年 | 134篇 |
1984年 | 76篇 |
1983年 | 65篇 |
1982年 | 56篇 |
1981年 | 38篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1974年 | 11篇 |
1936年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Nonlinear Dynamics - Oblique collisions are more likely to happen in the realistic translational joint with clearance, compared to the full front impacts. It can be a quite demanding task to... 相似文献
42.
Crystallography Reports - A cobalt coordination polymer, {[Co(L1)2(H2O)2] · (HCOO)2 · H2O}n, where L1 is a bis(4-(1H-imidazol-1-yl)phenyl)methanone, has been synthesized and characterized... 相似文献
43.
Sun Yuan Luo Shunlong Lei Xiangyun 《International Journal of Theoretical Physics》2021,60(9):3211-3224
International Journal of Theoretical Physics - Gram matrices arise naturally in the consideration of pair-wise overlap of a family of vectors or quantum pure states, and play an important role in... 相似文献
44.
45.
Si-Yang Feng Tao Zheng Ai-Jing Sun Zuo-Xiang Wang 《Molecular Crystals and Liquid Crystals》2019,692(1):43-52
AbstractComplexes of [CdL2(NO3)2]·1.5H2O and [Ag2(μ-L)2(NO3)2] were synthesized by the reactions of 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole (L) with Cd(NO3)2·4H2O and AgNO3, respectively. Their structures were determined by single crystal X-ray diffraction. The photophysical property and thermal stability were characterized by FT???IR, UV???Vis absorption, fluorescence, and thermogravimetric analysis (TGA). Both complexes belong to the triclinic system with space group p???1. The central metal of [CdL2(NO3)2]·1.5H2O has a distorted octahedral geometry [CdN4O2], while two central Ag(I) atoms of [Ag2(μ-L)2(NO3)2] exhibit distorted tetrahedral geometries [AgN3O]. 相似文献
46.
47.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
48.
当前锂离子动力电池电化学模型存在模型复杂、建模难度大、计算效率低、老化评估效果差的问题,本文提出一种考虑电池衰退老化的机理模型(ADME).本文首先通过有限差分法对伪二维(P2D)电化学模型进行离散降阶处理,得到简化伪二维(SP2D)模型.在SP2D模型的基础上,基于阴阳两极发生的副反应导致的衰退老化现象,提出一种考虑电池衰退老化的机理模型.其次,使用多变量偏差补偿最小二乘法实现模型参数辨识.最后通过动力电池衰退老化性能循环实验,对比分析了恒流、脉冲工况下SP2D模型和ADME模型的终端电压输出.结果表明:ADME模型较为简单、计算效率和估算精度高,可以有效评估电池容量老化衰退,得到理想的锂离子动力电池外特性曲线. 相似文献
49.
Mathematical Notes - Let $$\mathbb N$$ denote the set of all nonnegative integers, and let $$A\subseteq\mathbb N$$ . Let $$h,n\in\mathbb N$$ , $$h\ge 2$$ and $$r_h(A,n)=\#\{(a_1,\dots,a_h)\in... 相似文献
50.
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