全文获取类型
收费全文 | 2104篇 |
免费 | 421篇 |
国内免费 | 526篇 |
专业分类
化学 | 2086篇 |
晶体学 | 25篇 |
力学 | 10篇 |
综合类 | 11篇 |
数学 | 32篇 |
物理学 | 887篇 |
出版年
2024年 | 5篇 |
2023年 | 14篇 |
2022年 | 59篇 |
2021年 | 93篇 |
2020年 | 80篇 |
2019年 | 81篇 |
2018年 | 59篇 |
2017年 | 75篇 |
2016年 | 76篇 |
2015年 | 139篇 |
2014年 | 129篇 |
2013年 | 184篇 |
2012年 | 163篇 |
2011年 | 180篇 |
2010年 | 168篇 |
2009年 | 181篇 |
2008年 | 155篇 |
2007年 | 203篇 |
2006年 | 133篇 |
2005年 | 144篇 |
2004年 | 146篇 |
2003年 | 126篇 |
2002年 | 82篇 |
2001年 | 48篇 |
2000年 | 51篇 |
1999年 | 45篇 |
1998年 | 41篇 |
1997年 | 19篇 |
1996年 | 33篇 |
1995年 | 19篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有3051条查询结果,搜索用时 46 毫秒
131.
“活化分子”作为国内化学教育领域广为人知的科学概念,在各类相关化学教材中都有介绍。然而在国外多种经典化学教材中却完全没有“活化分子”的概念,反映出国内外化学教育领域对化学反应速率理论相关知识点的处理上存在明显的差异与分歧。通过溯源关键历史文献,回顾了“活化分子”概念的形成及其在化学反应速率理论发展过程中的角色演变,指出“活化分子”概念已经退出反应速率理论的舞台,在教材中应更多地呈现其在科学史方面的价值,而不是科学价值。 相似文献
132.
为了更精确地预言转动量子数J ≥ 100时双原子分子R支和Q支的振转跃迁谱线, 本文在考虑了转动能级展开式中高阶小项Hv的前提下重新推导出能更好地预言R支和Q支跃迁谱线的物理解析公式. 另一方面, 通过对差分收敛法计算过程的细致分析, 从物理误差的角度提出了一个在没有实验数据作为参照时仍然能有效收敛的重要物理判据. 应用这些新公式和新判据对TiF和CO分子R支振转跃迁谱线和TiF分子Q支振转跃迁谱线进行了研究. 结果表明: 包含高阶小项Hv的新公式的预言结果精度比原有不含Hv的公式的结果提高了一个数量级; 新判据的使用能更有效地减小预言谱线的可能误差, 提高预言结果精度. 最后通过与最小二乘法计算结果的对比, 进一步说明新公式和新判据在预言R支和Q支振转跃迁谱线数据方面的有效性和准确性. 相似文献
133.
Toshimitsu Yamazaki M.J.A. Yoshinori Akaishi 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2007,83(5):144-150
We have studied the structure of K−pp comprehensively by solving this threebody system in a variational method, starting from the Ansatz that the Λ(1405) resonance (≡Λ*) is a K−p bound state. The structure of K−pp reveals a molecular feature, namely, the K− in Λ* as an “atomic center” plays a key role in producing strong covalent bonding with the other proton. We point out that strongly bound nuclear systems are formed by “super strong” nuclear force due to migrating real bosonic particles a la Heitler-London-Heisenberg, whereas the normal nuclear force is caused by mediating virtual mesons. We have shown that the elementary process, p + p → K+ + Λ* + p, which occurs in a short impact parameter and with a large momentum transfer, leads to unusually large self-trapping of Λ* by the involved proton, since the Λ*-p system exists as a compact doorway state propagating to K−pp. 相似文献
134.
《印度化学会志》2021,98(2):100029
Alkaline phosphatase (ALP) is an important biomarker in clinical diagnostics, and the abnormal level of ALP enzyme in serum is closely related to various diseases such as bone metastases, bone or liver cancer, and extrahepatic biliary obstruction. Recognizing the location and expression level of ALP in live cells has a substantial importance in early-stage cancer diagnosis, as well as an important parameter for studying the recovery of the patients after liver transplantation. With the advent of the newer and advanced fluorescence imaging techniques, small-molecule fluorescent probes have become a very powerful tool for mapping the subtle changes in the enzyme expression level in living cells and tissues in real-time. In this account, we provide an overview of recent advances in small-molecule ALP fluorescent probes, mainly during the last few years, including the design strategies and applications for biological applications. 相似文献
135.
《中国化学快报》2021,32(8):2369-2379
Living-cell imaging demands high specificity,sensitivity,and minimal background interference to the targets of interest.However,developing a desirable imaging probe that can possess all the above features is still challenging.The bioorthogonal surface-enhanced Raman scattering(SERS) imaging has been recently emerged through utilizing Raman reporters with characteristic peaks in Raman-silent region of cells(1800-2800 cm~(-1)),which opens a revolutionary avenue for living-cell imaging with multiplexing capability.In this review,we focus on the recent advances in the technology development and the biological and biomedical applications of the living-cell bioorthogonal SERS imaging technique.After introduction of fundamental principles for bioorthogonal tag or label,we present applications for visualization of various intracellular components and environment including proteins,nucleic acids,lipids,pH and hypoxia,even for cancer diagnosis in tissue samples.Then,various bioorthogonal SERS imaging-guided thera py strategies have been discussed such as photothera py and surge ry.In conclusion,this strategy has great potential to be a flexible and robust tool for visualization detection and diseases diagnosis. 相似文献
136.
137.
By using first-principles calculations, we have systematically investigated the structural and electronic properties of an infinite linear monatomic Cu chain with an adsorbed CO molecule. We find that the bridge geometry is energeticabsally favored not only when the Cu–Cu bond below the molecule is unstretched, but also for a wide range of dCu–Cu up to about 4.20 Å, while the substitutional geometry is favored only in the hyperstretched situation dCu–Cu>4.80 Å. Charge density differences point out the electron transfer is from the Cu atoms to the adsorbed CO molecule. The binding mechanism of CO to Cu chain can be described by the Blyholder’s model, in terms of σ-donation of electron density from the nonbonding CO-5σ orbital into empty metal orbitals and π-backdonation from the occupied metal d orbitals to empty CO-2π⁎ orbital. The donation/backdonation process leads to the formation of bonding/antibonding pairs, 5σb/5σa and 2πb⁎/2πa⁎, with the 5σa lying above Ef and the 2πb⁎ below Ef. 相似文献
138.
Dr. Zhihai Li Dr. Manuel Smeu Sepideh Afsari Dr. Yangjun Xing Prof. Mark A. Ratner Prof. Eric Borguet 《Angewandte Chemie (International ed. in English)》2014,53(4):1098-1102
Sensors play a significant role in the detection of toxic species and explosives, and in the remote control of chemical processes. In this work, we report a single‐molecule‐based pH switch/sensor that exploits the sensitivity of dye molecules to environmental pH to build metal–molecule–metal (m‐M‐m) devices using the scanning tunneling microscopy (STM) break junction technique. Dyes undergo pH‐induced electronic modulation due to reversible structural transformation between a conjugated and a nonconjugated form, resulting in a change in the HOMO–LUMO gap. The dye‐mediated m‐M‐m devices react to environmental pH with a high on/off ratio (≈100:1) of device conductivity. Density functional theory (DFT) calculations, carried out under the non‐equilibrium Green’s function (NEGF) framework, model charge transport through these molecules in the two possible forms and confirm that the HOMO–LUMO gap of dyes is nearly twice as large in the nonconjugated form as in the conjugated form. 相似文献
139.
The Activation of Sulfur Hexafluoride at Highly Reduced Low‐Coordinate Nickel Dinitrogen Complexes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dipl.‐Chem. Patrick Holze Dipl.‐Chem. Bettina Horn Prof. Dr. Christian Limberg Dipl.‐Chem. Corinna Matlachowski Dr. Stefan Mebs 《Angewandte Chemie (International ed. in English)》2014,53(10):2750-2753
The greenhouse gas sulfur hexafluoride is the common standard example in the literature of a very inert inorganic small molecule that is even stable against O2 in an electric discharge. However, a reduced β‐diketiminate nickel species proved to be capable of converting SF6 into sulfide and fluoride compounds at ambient standard conditions. The fluoride product complex features an unprecedented [NiF]+ unit, where the Ni atom is only three‐coordinate, while the sulfide product exhibits a rare almost linear [Ni(μ‐S)Ni]2+ moiety. The reaction was monitored applying 1H NMR, IR and EPR spectroscopic techniques resulting in the identification of an intermediate nickel complex that gave insight into the mechanism of the eight‐electron reduction of SF6. 相似文献
140.
Conrad A. P. Goodwin Dr. Floriana Tuna Prof. Eric J. L. McInnes Prof. Stephen T. Liddle Dr. Jonathan McMaster Dr. Inigo J. Vitorica‐Yrezabal Dr. David P. Mills 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14579-14583
We report the synthesis and characterization of the uranium(III) triamide complex [UIII(N**)3] [ 1 , N**=N(SiMe2tBu)2?]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three‐coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [UIII(N**)3] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [UIII(N“)3] (N”=N(SiMe3)2?), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [UIII(N“)3], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of UIII single‐molecule magnets. 相似文献