全文获取类型
收费全文 | 11833篇 |
免费 | 1136篇 |
国内免费 | 1418篇 |
专业分类
化学 | 2387篇 |
晶体学 | 20篇 |
力学 | 417篇 |
综合类 | 171篇 |
数学 | 3166篇 |
物理学 | 1509篇 |
综合类 | 6717篇 |
出版年
2024年 | 48篇 |
2023年 | 158篇 |
2022年 | 345篇 |
2021年 | 419篇 |
2020年 | 508篇 |
2019年 | 373篇 |
2018年 | 352篇 |
2017年 | 329篇 |
2016年 | 392篇 |
2015年 | 413篇 |
2014年 | 532篇 |
2013年 | 756篇 |
2012年 | 575篇 |
2011年 | 671篇 |
2010年 | 546篇 |
2009年 | 728篇 |
2008年 | 691篇 |
2007年 | 803篇 |
2006年 | 661篇 |
2005年 | 618篇 |
2004年 | 606篇 |
2003年 | 533篇 |
2002年 | 487篇 |
2001年 | 391篇 |
2000年 | 345篇 |
1999年 | 352篇 |
1998年 | 298篇 |
1997年 | 238篇 |
1996年 | 198篇 |
1995年 | 162篇 |
1994年 | 145篇 |
1993年 | 104篇 |
1992年 | 100篇 |
1991年 | 98篇 |
1990年 | 91篇 |
1989年 | 89篇 |
1988年 | 54篇 |
1987年 | 32篇 |
1986年 | 19篇 |
1985年 | 31篇 |
1984年 | 24篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1955年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
1.
中医古文献蕴藏着丰富的临床经验,是古代中医在行医过程中对临床诊疗的经验性总结,体现了中医学形成和发展的理论框架和思想基础.然而这些宝贵的临床经验不仅量大,而且分散在不同的文献中,使得中医从业者手工很难快速全面地获取它们,文献检索工具也只能提供文档级别的信息筛选,无法为这种细粒度的信息获取提供支持.此外,古汉语相对于现代汉语的不同特点也限制了主流文本分析工具的使用效果.为此本文提出面向临床经验获取的中医古文献信息抽取任务,用于识别古文献中描述临床经验的文本片段,手工标注了样本数据用于这种抽取模型的训练和测试,并设计了基于深度学习的序列标注器用于完成该任务.考虑到标注数据量小可能带来的过度拟合问题,本文引入对抗训练和虚拟对抗训练来增强模型的泛化能力.一系列充分的实验验证了模型的有效性,表明利用信息抽取技术从古文献获取中医临床经验具有可行性,为这一新的信息抽取任务提供了有希望的研究基线和可复用的标注数据集. 相似文献
2.
Dr. Yong-Sheng Wei Dr. Liming Sun Miao Wang Dr. Jinhua Hong Dr. Lianli Zou Hongwen Liu Dr. Yu Wang Dr. Mei Zhang Dr. Zheng Liu Prof. Yinwei Li Prof. Satoshi Horike Prof. Kazu Suenaga Prof. Qiang Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16147-16156
Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear-complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities. 相似文献
3.
4.
《自然科学进展(英文版)》2020,30(2):185-191
Metal-organic frameworks(MOFs) have been regarded as promising catalyst materials due to the richness of coordinately unsaturated metal sites on the surface,which can act as catalytic active centres.In this study,a hybrid MOF material composed of Fe-based MOF and Co-based MOF was prepared with the involvement of graphene oxide nanosheets as additive.It was demonstrated that the hybrid MOF materials showed much higher electro-catalytic activity towards oxygen evolution than the single-phase counterparts.To drive current density of 10 mA cm~(-2),the hybrid CoFe-based MOF only needed an over potential of 290 mV in 1 M KOH.The catalytic activity could sustain for a longer time with only slight current density decrease.During oxygen evolution operation,the MOF catalyst evolved into catalytic active species but kept well the microscale sheet-like structure.It is thus believed that this study will provide an avenue for the development of advanced electrocatalysts. 相似文献
5.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research. 相似文献
6.
In 1976 S. Hawking claimed that “Because part of the information about the state of the system is lost down the hole, the final situation is represented by a density matrix rather than a pure quantum state”. 1 This was the starting point of the popular “black hole (BH) information paradox”. 相似文献
7.
8.
利用φ混合序列矩不等式和截尾的处理方法,研究非同分布φ混合序列加权和强极限收敛性质的问题,得到了若干新结果,推广并改进了独立同分布情形下的相应结果. 相似文献
9.
10.
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