全文获取类型
收费全文 | 1899篇 |
免费 | 23篇 |
国内免费 | 3篇 |
专业分类
化学 | 1252篇 |
晶体学 | 5篇 |
力学 | 17篇 |
数学 | 189篇 |
物理学 | 462篇 |
出版年
2016年 | 27篇 |
2015年 | 17篇 |
2014年 | 22篇 |
2013年 | 42篇 |
2012年 | 56篇 |
2011年 | 51篇 |
2010年 | 39篇 |
2009年 | 28篇 |
2008年 | 37篇 |
2007年 | 46篇 |
2006年 | 44篇 |
2005年 | 48篇 |
2004年 | 47篇 |
2003年 | 27篇 |
2002年 | 31篇 |
2001年 | 43篇 |
2000年 | 37篇 |
1999年 | 28篇 |
1998年 | 30篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 26篇 |
1994年 | 24篇 |
1993年 | 34篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1982年 | 20篇 |
1980年 | 27篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 52篇 |
1976年 | 37篇 |
1975年 | 37篇 |
1974年 | 40篇 |
1973年 | 39篇 |
1972年 | 38篇 |
1971年 | 29篇 |
1970年 | 21篇 |
1969年 | 30篇 |
1968年 | 31篇 |
1967年 | 38篇 |
1966年 | 28篇 |
1933年 | 16篇 |
排序方式: 共有1925条查询结果,搜索用时 15 毫秒
121.
Martin Schmid Hans‐Peter Steinrück J. Michael Gottfried 《Surface and interface analysis : SIA》2014,46(8):505-511
Asymmetric peak profiles for the application in spectroscopy can be obtained in a simple way by substituting the usually constant full width at half maximum parameter in Pseudo‐Voigt functions with an energy‐dependent expression, for instance of sigmoidal shape. While this approach has been successfully applied to vibrational spectra, we find that the resulting curves are less suitable for least‐squares fits of X‐ray photoelectron spectroscopy (XPS) data. However, if one additionally allows a variable displacement of the sigmoidal step relative to the peak, excellent fitting results can be obtained. We demonstrate the applicability of our extended approach on several inherently asymmetric XPS lines, i.e. the C 1s signal of graphite and C2H2/Pd(100), the 3d5/2–3d3/2 doublet of palladium, and the 4f7/2–4f5/2 doublet of platinum. Comparison of the corresponding fit results with the results obtained by the application of more elaborate, theory‐based line profiles (Doniach‐?unji? and Mahan functions) shows that the modified Pseudo‐Voigt function gives practically identical results in terms of peak shape and area, while requiring much less computational effort since no convolution procedures are required for its calculation. Thus, this function is most suitable for application in one of the following situations: (i) the peak shape of a given signal is known but cannot be calculated with ease, and (ii) the theoretical peak shape is not (yet) known, however, one wants to perform a first quantitative screening of the data at issue. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
122.
123.
Nardana Sivendran Florian Belitz Daniel Sowa Prendes Dr. Ángel Manu Martínez Prof. Dr. Rochus Schmid Prof. Dr. Lukas J. Gooßen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202103669
Trihalide salts were found to efficiently promote photochemical dediazotizing halogenations of diazonium salts. In contrast to classical Sandmeyer reactions, no metal catalysts are required to achieve high yields and outstanding selectivities for halogenation over competing hydridodediazotization. Convenient protocols are disclosed for synthetically meaningful brominations, iodinations, and chlorinations of diversely functionalized derivatives. 相似文献
124.
S. Qi H. Behringer T. Raasch F. Schmid 《The European physical journal. Special topics》2016,225(8-9):1527-1549
We discuss in detail a recently proposed hybrid particle-continuum scheme for complex fluids and evaluate it at the example of a confined homopolymer solution in slit geometry. The hybrid scheme treats polymer chains near the impenetrable walls as particles keeping the configuration details, and chains in the bulk region as continuous density fields. Polymers can switch resolutions on the fly, controlled by an inhomogeneous tuning function. By properly choosing the tuning function, the representation of the system can be adjusted to reach an optimal balance between physical accuracy and computational efficiency. The hybrid simulation reproduces the results of a reference particle simulation and is significantly faster (about a factor of 3.5 in our application example). 相似文献
125.
Stefan Dix Paul Golz Jonas R. Schmid Prof. Dr. Sebastian Riedel Prof. Matthew N. Hopkinson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11554-11558
Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro- and medicinal chemistry. Radical C−H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing . OCF3 radical sources make them unsuitable for the large-scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF3OOCF3) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one-step synthesis of valuable pyridine derivatives, which have been previously prepared via multi-step approaches. 相似文献
126.
Günter Schmid 《Journal of Cluster Science》2014,25(1):29-49
The article is dealing with the dependency of physical and chemical properties on size and coating of gold nanoparticles (Au NPs) and their potential in medicine. Full-shell clusters of the type Au55(PR3)12Cl6 are in the focal point due to their special properties. They act as quantum dots at room temperature and their stability is based on the perfect cuboctahedral structure. The bioresponse of the 1.4 nm Au55 clusters is, compared with smaller and larger Au NPs, very special, indicated by high cytotoxicity. It is caused by oxidative stress in cells accompanied by direct interactions with DNA. Biodistribution in Wistar–Kyoto rats differs also characteristically from larger Au NPs. Larger Au NPs, intravenously injected, assemble almost quantitatively in the liver, whereas Au55 clusters distribute over numerous other organs. All comparisons have been carried out by Au species with identical ligand molecules in order to have the same conditions concerning surface behaviour. 相似文献
127.
Martin Rentschler Sirma Iglesias Marie-Ann Schmid Dr. Cunming Liu Dr. Stefanie Tschierlei Dr. Wolfgang Frey Dr. Xiaoyi Zhang Dr. Michael Karnahl Dr. Dooshaye Moonshiram 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9527-9536
A systematic series of four novel homo- and heteroleptic CuI photosensitizers based on tetradentate 1,10-phenanthroline ligands of the type X^N^N^X containing two additional donor moieties in the 2,9-position (X=SMe or OMe) were designed. Their solid-state structures were assessed by X-ray diffraction. Cyclic voltammetry, UV-vis absorption, emission and X-ray absorption spectroscopy were then used to determine their electrochemical, photophysical and structural features in solution. Following, time-resolved X-ray absorption spectroscopy in the picosecond time scale, coupled with time-dependent density functional theory calculations, provided in-depth information on the excited state electron configurations. For the first time, a significant shortening of the Cu−X distance and a change in the coordination mode to a pentacoordinated geometry is shown in the excited states of the two homoleptic complexes. These findings are important with respect to a precise understanding of the excited state structures and a further stabilization of this type of photosensitizers. 相似文献
128.
129.
Steffen Cychy Sebastian Lechler Zijian Huang Michael Braun Ann Cathrin Brix Peter Blümler Corina Andronescu Friederike Schmid Wolfgang Schuhmann Martin Muhler 《催化学报》2021,42(12):2206-2215
在碱性甘油电氧化反应中,利用电化学傅里叶变换衰减全反射谱红外光谱法,研究了薄膜流动池中滴注硼酸镍催化剂负载量对玻碳电极性能的影响.连续操作的径向流动池包括一个位于内反射元件上方50μm的钻孔电极,可实现红外光谱分析.这是在确定条件下对电催化剂进行简便和可重复筛选的一个适合的方法,同时还提供了对复杂反应(如甘油氧化)产物选择性的检测.通过对泵送电解液进行更耗时的定量高效液相色谱分析,结果表明,衰减全反射红外光谱法可快速鉴定产物.在层流条件下,水中使用0.1 M甘油和1 M KOH,流速为5μL min-1时,甘油转化率较高.转化率和选择性取决于催化剂的负载量,负载量又决定了催化剂层的厚度和粗糙度.由于在更粗糙的膜中停留时间更长有利于再吸附和C-C键断裂,因此当负载量最高达210μg cm-2时,甘油转化率为73%且甲酸选择性接近80%.当最低负载量为13μg cm-2时,甘油转化率达到63%,甲酸选择性降至60%,相应地,C2物种(如乙醇酸盐)选择性较高,为8%.因此,只有催化剂负载量较低时才能形成几微米厚度范围内的薄膜,此时才适合进行优质催化剂的筛选. 相似文献
130.