全文获取类型
收费全文 | 29598篇 |
免费 | 103篇 |
国内免费 | 282篇 |
专业分类
化学 | 10953篇 |
晶体学 | 280篇 |
力学 | 1390篇 |
综合类 | 12篇 |
数学 | 9183篇 |
物理学 | 8165篇 |
出版年
2018年 | 1203篇 |
2017年 | 1453篇 |
2016年 | 726篇 |
2015年 | 548篇 |
2014年 | 481篇 |
2013年 | 678篇 |
2012年 | 3127篇 |
2011年 | 2311篇 |
2010年 | 1807篇 |
2009年 | 1547篇 |
2008年 | 571篇 |
2007年 | 612篇 |
2006年 | 610篇 |
2005年 | 4444篇 |
2004年 | 3918篇 |
2003年 | 2309篇 |
2002年 | 494篇 |
2001年 | 290篇 |
2000年 | 99篇 |
1999年 | 192篇 |
1998年 | 127篇 |
1997年 | 87篇 |
1996年 | 56篇 |
1995年 | 61篇 |
1994年 | 61篇 |
1992年 | 175篇 |
1991年 | 174篇 |
1990年 | 145篇 |
1989年 | 119篇 |
1988年 | 117篇 |
1987年 | 81篇 |
1986年 | 54篇 |
1985年 | 44篇 |
1984年 | 41篇 |
1983年 | 43篇 |
1981年 | 40篇 |
1980年 | 36篇 |
1979年 | 38篇 |
1978年 | 43篇 |
1977年 | 37篇 |
1976年 | 98篇 |
1975年 | 53篇 |
1974年 | 55篇 |
1973年 | 77篇 |
1972年 | 52篇 |
1970年 | 50篇 |
1969年 | 38篇 |
1968年 | 39篇 |
1967年 | 36篇 |
1966年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
Jakob Woisetschl?ger Adam D. Wexler Gert Holler Mathias Eisenhut Karl Gatterer Elmar C. Fuchs 《Experiments in fluids》2012,52(1):193-205
When a high-voltage direct-current is applied to two beakers filled with polar liquid dielectrica like water or methanol,
a horizontal bridge forms between the two beakers. By repeating a version of Pellat’s experiment, it is shown that a horizontal
bridge is stable by the action of electrohydrodynamic pressure. Thus, the static and dynamic properties of the phenomenon
called a ‘floating water bridge’ can be explained by the gradient of Maxwell pressure, replenishing the liquid within the
bridge against any drainage mechanism. It is also shown that a number of liquids can form stable and long horizontal bridges.
The stability of such a connection, and the asymmetry in mass flow through such bridges caused by the formation of ion clouds
in the vicinity of the electrodes, is also discussed by two further experiments. 相似文献
902.
Marina Toši?Dragana S. Cvetkovi?-Ili? 《Applied mathematics and computation》2012,218(9):4651-4657
In this paper, we present some results relating different matrix partial orderings and the invertibility of a linear combination of EP matrices. 相似文献
903.
It is argued that awareness of the distinction between dynamical and variational symmetries is crucial to understanding the significance of Noether's 1918 work. Special attention is paid, by way of a number of striking examples, to Noether's first theorem, which establishes a correlation between dynamical symmetries and conservation principles. 相似文献
904.
Johisner Penagos‐Llanos Olimpo García‐Beltrn J. A. Caldern Edgar Nagles J. J. Hurtado 《Electroanalysis》2019,31(4):695-703
The detection of Allura red (AR) by electrochemical reduction using a different electrode from the conventional mercury electrode is presented. A carbon paste with cobalt (II, III) oxide composite electrode (CoOx/CPE) is reported for the first time for the detection of AR. Moreover, others dyes such as tartrazine (TZ), sunset yellow (SY), amaranth (AM), Ponceaut 4‐R (P‐4R), and Sudan (SD) as well as pharmaceutical agents such as paracetamol (PMC) that are present in samples that contained AR did not show a reduced signal between 0.0 and ?0.3 V, which is the potential range where AR reduction was observed. The surface electroactivity was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of CoOX increased the cathodic peak current for AR by more than 50 % and 65 % via CV and square wave voltammetry (SWV), respectively, compared with an unmodified carbon paste electrode. Under the optimal parameters, (pH=3.0, accumulation time (tACC)=60 s and accumulation potential (EACC)=0.50 V), the detection limit for AR was 0.05 μmol L?1. The new sensor was sensitive and stable for the detection of AR. Moreover, it was easily manufactured and very convenient for food samples such as soft and isotonic drinks as well as chili sauce. 相似文献
905.
Srigokul Upadhyayula Vicente Nu?ez Eli M. Espinoza Jillian M. Larsen Duoduo Bao Dewen Shi Jenny T. Mac Bahman Anvari Valentine I. Vullev 《Chemical science》2015,6(4):2237-2251
Cyanine dyes are broadly used for fluorescence imaging and other photonic applications. 3,3′-Diethylthiacyanine (THIA) is a cyanine dye composed of two identical aromatic heterocyclic moieties linked with a single methine, –CH. The torsional degrees of freedom around the methine bonds provide routes for non-radiative decay, responsible for the inherently low fluorescence quantum yields. Using transient absorption spectroscopy, we determined that upon photoexcitation, the excited state relaxes along two parallel pathways producing three excited-state transients that undergo internal conversion to the ground state. The media viscosity impedes the molecular modes of ring rotation and preferentially affects one of the pathways of non-radiative decay, exerting a dominant effect on the emission properties of THIA. Concurrently, the polarity affects the energy of the transients involved in the decay pathways and further modulates the kinetics of non-radiative deactivation. 相似文献
906.
A Collaboration M. Makek P. Achenbach C. Ayerbe Gayoso C. Barbieri J. C. Bernauer R. B?hm D. Bosnar A. Denig M. O. Distler I. Fri??i? C. Giusti H. Merkel U. Müller L. Nungesser J. Pochodzalla S. Sanches Majos B. S. Schlimme M. Schwamb Th. Walcher 《The European Physical Journal A - Hadrons and Nuclei》2016,52(9):298
907.
Xiao-Ying Yu Jennifer Yao Edgar C. Buck Zihua Zhu 《Surface and interface analysis : SIA》2020,52(7):454-459
Trace analysis of nuclear materials in solid particles collected in the environment or particles in liquid slurry generated in nuclear material manufacturing processes can pinpoint elemental, organic, and isotopic signatures of nuclear fuel cycle activities and processes. Such information can support nuclear safeguards programs by increasing our ability to detect undeclared nuclear materials, routine activities for safeguarding at declared facilities, and illicit activities. However, trace radioactive material analysis in liquids and slurries is challenging using bulk approaches. For example, one drawback of sensitive analysis such as inductively coupled plasma mass spectrometry (ICP-MS) is that sample is consumed or destroyed as a result of the technical approach. We developed a vacuum compatible microfluidic interface to enable surface analysis of liquids and solid–liquid interactions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this work, we illustrate the initial results from the analysis of liquid uranium oxide standard solutions using in situ liquid SIMS. Because the liquid SIMS analysis is almost nondestructive, the same sample can then be analyzed by other analytical techniques or saved for future reference. Consequently, multimodal analysis is possible. Our results demonstrate that in situ liquid SIMS can be used as a new approach to analyze radioactive materials in liquid and slurry forms of relevance to diverse applications. 相似文献
908.
We explore two- and three-state Markov models driven out of thermal equilibrium by non-potential forces, to demonstrate basic properties of the steady heat capacity based on the concept of quasistatic excess heat. It is shown that large enough driving forces can make the steady heat capacity negative. For both the low- and high-temperature regimes we propose an approximative thermodynamic scheme in terms of “dynamically renormalized” effective energy levels. 相似文献
909.
910.
Patrick Homenya Markus Messerschmidt Muhammad Nawaz Tahir Victor Martinez Yajun Cheng Jochen S. Gutmann Michael Klein Stefan Jung Morris Wolff Reza Saadat Driss Nariaki Roman Bo?a G?star Klingelh?fer Wolfgang Tremel Franz Renz 《Hyperfine Interactions》2012,205(1-3):63-67
The nonanuclear coordination compound [MoIV{(CN)FeIII(3-methyl-saldptn)}8]Cl4 exhibits multiple spin transitions (3-methyl-saldptn = N,N′-bis(3′′-methyl-2′′-hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. M?ssbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid. 相似文献