全文获取类型
收费全文 | 6217篇 |
免费 | 492篇 |
国内免费 | 249篇 |
专业分类
化学 | 4267篇 |
晶体学 | 67篇 |
力学 | 200篇 |
综合类 | 18篇 |
数学 | 714篇 |
物理学 | 1692篇 |
出版年
2024年 | 9篇 |
2023年 | 67篇 |
2022年 | 89篇 |
2021年 | 158篇 |
2020年 | 154篇 |
2019年 | 166篇 |
2018年 | 118篇 |
2017年 | 119篇 |
2016年 | 212篇 |
2015年 | 190篇 |
2014年 | 259篇 |
2013年 | 398篇 |
2012年 | 476篇 |
2011年 | 549篇 |
2010年 | 323篇 |
2009年 | 271篇 |
2008年 | 411篇 |
2007年 | 330篇 |
2006年 | 358篇 |
2005年 | 300篇 |
2004年 | 272篇 |
2003年 | 185篇 |
2002年 | 194篇 |
2001年 | 147篇 |
2000年 | 124篇 |
1999年 | 114篇 |
1998年 | 72篇 |
1997年 | 87篇 |
1996年 | 66篇 |
1995年 | 71篇 |
1994年 | 57篇 |
1993年 | 68篇 |
1992年 | 71篇 |
1991年 | 60篇 |
1990年 | 55篇 |
1989年 | 37篇 |
1988年 | 28篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 36篇 |
1984年 | 37篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1974年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有6958条查询结果,搜索用时 15 毫秒
1.
miRNA (miR)-155 is a potential biomarker for breast cancers. We aimed at developing a nanosensor for miR-155 detection by integrating hybridization chain reaction (HCR) and silver nanoclusters (AgNCs). HCR serves as an enzyme-free and isothermal amplification method, whereas AgNCs provide a built-in fluorogenic detection probe that could simplify the downstream analysis. The two components were integrated by adding a nucleation sequence of AgNCs to the hairpin of HCR. The working principle was based on the influence of microenvironment towards the hosted AgNCs, whereby unfolding of hairpin upon HCR has manipulated the distance between the hosted AgNCs and cytosine-rich toehold region of hairpin. As such, the dominant emission of AgNCs changed from red to yellow in the absence and presence of miR-155, enabling a ratiometric measurement of miR with high sensitivity. The limit of detection (LOD) of our HCR-AgNCs nanosensor is 1.13 fM in buffered solution. We have also tested the assay in diluted serum samples, with comparable LOD of 1.58 fM obtained. This shows the great promise of our HCR-AgNCs nanosensor for clinical application. 相似文献
2.
3.
4.
5.
Sung Hwan Koo Dong Jun Li Taeyeong Yun Dong Sung Choi Kyung Eun Lee Gil Yong Lee Youngtak Oh Joonwon Lim Suchithra Padmajan Sasikala Ho Jin Lee In Ho Kim Hong Ju Jung Rishabh Jain Sang Ouk Kim 《Particle & Particle Systems Characterization》2019,36(7)
Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS2, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec?1 and a charge transfer resistance (Rct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer. 相似文献
6.
Sajeesh Kumar Madhurakkat Perikamana Sang Min Lee Jinkyu Lee Taufiq Ahmad Min Suk Lee Hee Seok Yang Heungsoo Shin 《Macromolecular bioscience》2019,19(4)
Plant derived flavonoids have not been well explored in tissue engineering applications due to difficulties in efficient formulations with biomaterials for controlled presentation. Here, the authors report that surface coating of epigallocatechin gallate (EGCG) on polymeric substrates including poly (L‐lactic acid) (PLLA) nanofibers can be performed via oxidative polymerization of EGCG in the presence of cations, enabling regulation of biological functions of multiple cell types implicated in bone regeneration. EGCG coating on the PLLA nanofiber promotes osteogenic differentiation of adipose‐derived stem cells (ADSCs) and is potent to suppress adipogenesis of ADSCs while significantly reduces osteoclastic maturation of murine macrophages. Moreover, EGCG coating serves as a protective layer for ADSCs against oxidative stress caused by hydrogen peroxide. Finally, the in vivo implantation of EGCG‐coated nanofibers into a mouse calvarial defect model significantly promotes the bone regeneration (61.52 ± 28.10%) as compared to defect (17.48 ± 11.07%). Collectively, the results suggest that EGCG coating is a simple bioinspired surface modification of polymeric biomaterials and importantly can thus serve as a promising interface for tuning activities of multiple cell types associated with bone fracture healing. 相似文献
7.
8.
GM(1,1)的周期修正模型及其在泉水流量预测中的应用 总被引:6,自引:2,他引:4
本文阐述了 GM( 1 ,1 )的残差周期修正模型 ,并将它应用于山西神头泉的流量预测中 ,建立了神头泉流量的 GM( 1 ,1 )周期修正模型 ,对其流量进行了预测 ,为神头泉域岩溶水资源开发利用和保护提供了科学依据 相似文献
9.
The natural modes of a discrete linear system are orthogonal with respect to the mass and stiffness matrices in a generalized sense. However, these modes are usually not orthogonal to each other in the ordinary sense. The purpose of this paper is to document a number of conditions under which the modes are also orthogonal in an ordinary fashion. 相似文献
10.
Mattias Edn Jekabs Grins Zhijian Shen Zheng Weng 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,169(2):1
Using enhancement of the 27Al central-transition magnetization by applying RAPT prior to 27Al → 29Si cross-polarization, we demonstrate fast acquisition of 29Si one-dimensional MAS and two-dimensional 27Al–29Si HETCOR spectra on a new sialon phase Ba2Al3Si9N13O5. 相似文献