全文获取类型
收费全文 | 5516篇 |
免费 | 1014篇 |
国内免费 | 553篇 |
专业分类
化学 | 3576篇 |
晶体学 | 49篇 |
力学 | 243篇 |
综合类 | 31篇 |
数学 | 738篇 |
物理学 | 2446篇 |
出版年
2024年 | 3篇 |
2023年 | 126篇 |
2022年 | 105篇 |
2021年 | 170篇 |
2020年 | 224篇 |
2019年 | 192篇 |
2018年 | 179篇 |
2017年 | 171篇 |
2016年 | 282篇 |
2015年 | 237篇 |
2014年 | 306篇 |
2013年 | 375篇 |
2012年 | 474篇 |
2011年 | 549篇 |
2010年 | 338篇 |
2009年 | 328篇 |
2008年 | 356篇 |
2007年 | 329篇 |
2006年 | 315篇 |
2005年 | 262篇 |
2004年 | 193篇 |
2003年 | 169篇 |
2002年 | 195篇 |
2001年 | 147篇 |
2000年 | 121篇 |
1999年 | 154篇 |
1998年 | 127篇 |
1997年 | 108篇 |
1996年 | 103篇 |
1995年 | 71篇 |
1994年 | 52篇 |
1993年 | 51篇 |
1992年 | 47篇 |
1991年 | 57篇 |
1990年 | 31篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有7083条查询结果,搜索用时 15 毫秒
41.
42.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
43.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
44.
45.
Marcel Sickert Harald Weinstabl Brendan Peters Xiao Hou Mark Lautens 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(20):5247-5251
A palladium‐catalyzed intermolecular cross‐coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency. 相似文献
46.
Shaolei Ding Yingbo Shi Baochao Yang Min Hou Dr. Haibing He Prof. Dr. Shuanhu Gao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214873
We report herein the asymmetric total synthesis of periglaucines A–C, N,O-dimethyloxostephine and oxostephabenine. The key strategies used include: 1) a RhI-catalyzed regio- and diastereoselective Hayashi-Miyaura reaction to connect two necessary fragments; 2) an intramolecular photoenolization/Diels–Alder (PEDA) reaction to construct the highly functionalized tricyclic core skeleton bearing a quaternary center; 3) a bio-inspired intramolecular Michael addition and transannular acetalization to generate the aza[4.4.3]propellane and the tetrahydrofuran ring. 相似文献
47.
层状富锂材料具有超过250 mAh∙g−1的高可逆比容量,被认为是下一代高比能锂离子电池最具商业化前景的正极材料之一。然而,层状富锂材料在实际应用之前仍需解决诸多挑战,如高电压氧释放、层状到岩盐相的结构变化、过渡金属离子迁移等结构劣化,并由此带来了较低的初始库伦效率、电压/容量的衰减以及循环寿命的不足。针对以上问题,进行层状富锂材料改性无疑是一种行之有效的方法。本综述全面介绍了层状富锂材料的结构、组分以及电化学性能,在此基础上对材料改性策略进行了系统阐述,详细介绍了体相掺杂、表面包覆、缺陷设计、离子交换和微结构调控等一系列改性策略的现状以及发展趋势,最终提出了高容量和长循环层状富锂材料和高比能锂离子电池的设计思路。 相似文献
48.
Xingyue He Qing Wu Chen Hou Min Hu Qigang Wang Xia Wang 《Angewandte Chemie (International ed. in English)》2023,62(15):e202218766
Some cellular enzymatic pathways are located within a single organelle, while most others involve enzymes that are located within multiple compartmentalized cellular organelles to realize the efficient multi-step enzymatic process. Herein, bioinspired by enzyme-mediated biosynthesis and biochemical defense, a compartmented nanoreactor (Burr-NCs@GlSOD) was constructed through a self-confined catalysis strategy with burr defect-engineered molybdenum disulfide/Prussian blue analogues (MoS2/PBA) and an interfacial diffusion-controlled hydrogel network. The specific catalytic mechanism of the laccase-like superactivity induced hydrogelation and cascade enzyme catalytic therapy were explored. The confined hydrogelation strategy introduces a versatile means for nanointerface functionalization and provides insight into biological construction of simulated enzymes with comparable activity and also the specificity to natural enzymes. 相似文献
49.
Dr. Tingting Xu Dr. Xudong Hou Dr. Yi Han Dr. Haipeng Wei Dr. Zhengtao Li Prof. Dr. Chunyan Chi 《Angewandte Chemie (International ed. in English)》2023,62(38):e202304937
Polycyclic hydrocarbons consisting of two or more directly fused antiaromatic subunits are rare due to their high reactivity. However, it is important to understand how the interactions between the antiaromatic subunits influence the electronic properties of the fused structure. Herein, we present the synthesis of two fused indacene dimer isomers: s-indaceno[2,1-a]-s-indacene ( s -ID ) and as-indaceno[3,2-b]-as-indacene ( as -ID ), containing two fused antiaromatic s-indacene or as-indacene units, respectively. Their structures were confirmed by X-ray crystallographic analysis. 1H NMR/ESR measurements and DFT calculations revealed that both s -ID and as -ID have an open-shell singlet ground state. However, while localized antiaromaticity was observed in s -ID , as -ID showed weak global aromaticity. Moreover, as -ID exhibited a larger diradical character and a smaller singlet-triplet gap than s -ID . All the differences can be attributed to their distinct quinoidal substructures. 相似文献
50.
Dr. Ying-Jie Sun Wen-Da Chen Dr. Ji Liu Jun-Jin Li Yu Zhang Wei-Qi Cai Prof. Li Liu Xin-Jing Tang Jian Hou Prof. Ming Wang Prof. Liang Cheng 《Angewandte Chemie (International ed. in English)》2023,62(5):e202212413
The CRISPR/Cas system is one of the most powerful tools for gene editing. However, approaches for precise control of genome editing and regulatory events are still desirable. Here, we report the spatiotemporal and efficient control of CRISPR/Cas9- and Cas12a-mediated editing with conformationally restricted guide RNAs (gRNAs). This approach relied on only two or three pre-installed photo-labile substituents followed by an intramolecular cyclization, representing a robust synthetic method in comparison to the heavily modified linear gRNAs that often require extensive screening and time-consuming optimization. This tactic could direct the precise cleavage of the genes encoding green fluorescent protein (GFP) and the vascular endothelial growth factor A (VEGFA) protein within a predefined cutting region without notable editing leakage in live cells. We also achieved light-mediated myostatin (MSTN) gene editing in embryos, wherein a new bow-knot-type gRNA was constructed with excellent OFF/ON switch efficiency. Overall, our work provides a significant new strategy in CRISPR/Cas editing with modified circular gRNAs to precisely manipulate where and when genes are edited. 相似文献