全文获取类型
收费全文 | 1308篇 |
免费 | 46篇 |
国内免费 | 11篇 |
专业分类
化学 | 926篇 |
晶体学 | 9篇 |
力学 | 26篇 |
数学 | 232篇 |
物理学 | 172篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 52篇 |
2021年 | 75篇 |
2020年 | 36篇 |
2019年 | 43篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 71篇 |
2015年 | 43篇 |
2014年 | 55篇 |
2013年 | 85篇 |
2012年 | 99篇 |
2011年 | 80篇 |
2010年 | 60篇 |
2009年 | 74篇 |
2008年 | 93篇 |
2007年 | 97篇 |
2006年 | 94篇 |
2005年 | 66篇 |
2004年 | 42篇 |
2003年 | 24篇 |
2002年 | 36篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1365条查询结果,搜索用时 296 毫秒
931.
This paper provides several extensions of the notion of dimension of a simple game and proves the existence of a minimum subclass
of weighted games with the property that every simple game can be expressed as their intersection. Some further generalizations
lead to the new concept of codimension which is obtained by considering the union instead of the intersection as the basic
operation. 相似文献
932.
Dominika Borek Stephan L. Ginell Marcin Cymborowski Wladek Minor Zbyszek Otwinowski 《Journal of synchrotron radiation》2007,14(1):24-33
During diffraction experiments even cryo‐cooled protein crystals can be significantly damaged due to chemical and physical changes induced by absorbed X‐ray photons. The character and scale of the observed effects depend strongly on the temperature and the composition of crystals. The absorption of radiation energy results in incremental regular changes to the crystal structure, making its impact on the process of solving the structure strongly correlated with other experimental variables. An understanding of all the dependencies is still limited and does not allow for a precise prediction of the outcome of a particular diffraction experiment. Results are presented of diffraction experiments performed under different experimental conditions. The influence of temperature and crystal composition on different characteristics of radiation damage is analyzed. The observed effects are discussed in terms of their impact on data processing and phasing procedures. 相似文献
933.
Michal Chudy Ilona Grabowska Patrycja Ciosek Alicja Filipowicz-Szymanska Dorota Stadnik Iwona Wyzkiewicz Elzbieta Jedrych Marcin Juchniewicz Maciej Skolimowski Karina Ziolkowska Radoslaw Kwapiszewski 《Analytical and bioanalytical chemistry》2009,395(3):647-668
This article presents an overview of various miniaturized devices and technologies developed by our group. Innovative, fast and cheap procedures for the fabrication of laboratory microsystems based on commercially available materials are reported and compared with well-established microfabrication techniques. The modules fabricated and tested in our laboratory can be used independently or they can be set up in different configurations to form functional measurement systems. We also report further applications of the presented modules e.g. disposable poly(dimethylsiloxane) (PDMS) microcuvettes, fibre optic detectors, potentiometric sensors platforms, microreactors and capillary electrophoresis (CE) microchips as well as integrated microsystems e.g. double detection microanalytical systems, devices for studying enzymatic reactions and a microsystem for cell culture and lysis. 相似文献
934.
935.
We consider two classes of Jacobi matrix operators in l2 with zero diagonals and with weights of the form nα+cn for 0<α1 or of the form nα+cnnα−1 for α>1, where {cn} is periodic. We study spectral properties of these operators (especially for even periods), and we find asymptotics of some of their generalized eigensolutions. This analysis is based on some discrete versions of the Levinson theorem, which are also proved in the paper and may be of independent interest. 相似文献
936.
Two bent-core verdazyl radicals, 2[16] and 3[16], containing 6-thioxo and 6-oxo groups, respectively, were prepared and their physical properties were compared. Analysis of binary mixtures with bent-core mesogen 1[12] gave virtual N-I ([TNI]) and N-Ire ([TNIre]) transition temperatures. Results indicate that the thioxo derivative 2[16] has greater stabilising effect on the nematic phase than the 6-oxo analogue 3[16], presumably due to the higher dipole moment of the core (1.90 D vrs 0.83 D) despite the less favourable conformational properties. 相似文献
937.
Agnieszka Plis Janusz Lasek Agnieszka Skawińska Marcin Kopczyński 《Chemical Papers》2014,68(7):879-889
Posidonia oceanica (PO) is a marine plant endemic to the Mediterranean basin, forming extensive grasslands. Onshore residues represent a major environmental, economic, social and hygienic problem in all coastal zones of the Mediterranean basin due to the great disturbance they cause to bathers and beachfront populations. This work sought to evaluate the thermo-chemical properties of PO in pyrolysis and thermo-oxidative degradation processes. The investigations were carried out using a thermogravimetric analyser (TGA) coupled to a quadrupole mass spectrometer (MS) and an infrared spectrometer (FTIR). In addition, proximate, ultimate, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and biodegradability analyses were carried out on PO. The biodegradability analysis confirmed that residues of PO were a biodegradable material. Accordingly, the application of PO as a feedstock for combustion/co-combustion or biorefining is recommended. 相似文献
938.
The low-molecular weight poly(? -caprolactone) and polylactide were obtained by the polymerization of cyclic esters in the presence of amino acid initiators. The polymer structures were elucidated by means of MALDI TOF, NMR and IR studies. Effects of temperature, reaction time and initiator dosage on the polymerization process were examined. 相似文献
939.
We propose a new type of gauge-invariant expansion of the ionization probability amplitudes of atoms by short pulses of electromagnetic radiation. Contrary to previous gauge-invariant approaches to this problem it does not require different partitions of the total Hamiltonian depending on the choice of gauge. In a natural way the atomic potential is treated as perturbation acting on an electron interacting with strong pulse. Whereas this is a standard assumption of strong field approximation (SFA), we show that grouping consequently together all terms of the same order in the atomic potential results in the expansion of the amplitude which is gauge invariant order by order, and not only in the limit of infinite series. In this approach, which is illustrated by numerical examples, the “direct ionization” and “rescattering” contributions are different from those commonly used in SFA-calculations. 相似文献
940.
Błażej Gierczyk Marcin Kaźmierczak Łukasz Popenda Andrzej Sporzyński Grzegorz Schroeder Stefan Jurga 《Magnetic resonance in chemistry : MRC》2014,52(5):202-213
The paper presents results of a systematic NMR studies on fluorinated phenylboronic acids. All possible derivatives were studied. The experimental 1H, 13C, 19F, 11B, and 17O spectral data were compared with the results of theoretical calculations. The relation between the calculated natural bond orbital parameters and spectral data (chemical shifts and coupling constants) is discussed. The first examples of 10B/11B isotopic effect on the 19F spectra and 4JFO scalar coupling in organic compounds are reported. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献