全文获取类型
收费全文 | 654篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 374篇 |
晶体学 | 5篇 |
力学 | 25篇 |
数学 | 78篇 |
物理学 | 190篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 14篇 |
2015年 | 20篇 |
2014年 | 13篇 |
2013年 | 32篇 |
2012年 | 37篇 |
2011年 | 43篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 47篇 |
2006年 | 33篇 |
2005年 | 27篇 |
2004年 | 37篇 |
2003年 | 25篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1889年 | 2篇 |
排序方式: 共有672条查询结果,搜索用时 31 毫秒
141.
P. Costa Bizzarri C. Della Casa M. Fiorini W. Porzio 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):255-265
Oligomers containing thianthrene units in the chain are synthesized by AlCl3-catalyzed reaction of diphenylsulfide, thianthrene, poly(p-phenylene sulfide), and poly(m-phenylene disulfide) with sulfur at 80°C. The products are compared with that obtained by the reaction of diphenylsulfide with AlCl3 at 225°C. IR spectra and elemental analyses are consistent with cyclic chain structures and show a higher cyclization for CHCl3-insoluble fractions. X-ray diffraction analysis indicates the same structure for the samples obtained with the different methods of synthesis. A possible structural model is tentatively proposed. 相似文献
142.
F. Bella G. Della Monica A. Ermini V. Sgrigna R. Bella P. F. Biagi P. Mandjgaladze D. Zilpimiani 《Il Nuovo Cimento C》1989,12(2):251-259
Summary A new equipment able to reveal the electric component of electromagnetic emission and suitable for underground deployment
has been made. The system enables to measure the absolute value of integrated voltage of signals. Data are recorded by a solid-state
memory circuit. The system is performed as a plug-in modular design and it can be also used in diverse fields of application.
Riassunto è stata realizzata una nuova strumentazione per la rivelazione della componente elettrica delle emissioni elettromagnetiche in laboratori sotterranei. Il sistema è in grado di misurare i valori assoluti della tensione integrata dei segnali. I dati vengono registrati su un circuito di memoria a stato solido. Il sistema è stato realizzato con caratteristiche modulari e può essere utilizzato anche in altri campi di applicazione.
Резюме Сконструировано новое оборудование для регистрации электрической компоненты электромагнитных излучений в подземных лабораториях. Система позволяет измерять абсолютную величину суммарного напряжения сигналов. Данные регистрируются в схеме с твердотельной памятью. Предложенная система собрана на специальных сменных модулях и может быть использована для различным прикладных задач.相似文献
143.
F. Bella P. F. Biagi M. Caputo G. Della Monica A. Ermini W. Plastino V. Sgrigna D. Zilpimiani 《Il Nuovo Cimento C》1995,18(1):19-32
Summary Since 1988–89 equipment for detecting electric, magnetic and seismoacoustic signals has been running inside the Amare cave.
The Amare cave is placed on the southern slope of the Gran Sasso chain, that is one of the largest karst areas of the Italian
Apennines. In 1992, a similar equipment was installed inside the Cervo cave. This cave is located in another karst area of
the Central Apennines, at about 50 km southwestwards of the Amare cave. In both these measurements sites, the signals are
recorded every ten minutes in a digital form; the equipment is able to record signals, the frequency of which ranges from
some hundred Hz to some hundred kHz. The data collected up to now seem to identify two different states that we call ?quiet?
and ?perturbed? state. In the quiet state only electric and magnetic signals with the highest frequencies appear. These signals
are connected with radio broadcastings and with the general lightnings activity of the Earth. A perturbed state is characterized
by the sudden appearance of seismoacoustic signals coupled with electric and magnetic ones. This phenomenology is connected
with local processes. Rainfall, atmospheric-pressure variations and some thermal effects are responsible for these local processes.
A possible model is proposed to justify the observed phenomenology: micromovements of the limestone blocks that constitute
the roof of the caves are invoked for the production of seismoacoustic signals. The electrification generated by these movements
is invoked for the production of electric and magnetic signals. 相似文献
144.
145.
F. Brandi F. Della Valle A.M. De Riva P. Micossi F. Perrone C. Rizzo G. Ruoso G. Zavattini 《Applied physics. B, Lasers and optics》1997,65(3):351-355
-7 rad to 2×10-6 rad.
Received: 28 January 1997 相似文献
146.
C. Marinelli A. Burchianti A. Bogi F. Della Valle G. Bevilacqua E. Mariotti S. Veronesi L. Moi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(3):319-325
Simultaneous light-induced desorption of rubidium and cesium atoms has been observed in polydimethylsiloxane (PDMS) coated
Pyrex cells at room temperature and at low light intensity. The two alkali atoms show the same dynamics and the same dependence
on the desorbing light frequency. No competition in the free sites occupancy exists. An interpretation of the experimental
results in terms of non-resonant light scattering from the PDMS coating is discussed. 相似文献
147.
Giuseppe Della Gatta 《Thermochimica Acta》1985,96(2):349-363
Energy changes occurring during adsorption in gas-solid and solution-solid systems are considered in connection with measurement of the adsorption enthalpies. Some experimental apparatuses allowing determination both of heat evolved and adsorbed amounts are described, with special regard to those using heat-flow microcalorimeters. Calibration techniques and experimental data reliability are also discussed. 相似文献
148.
F Della Croce R Tadei P Baracco A Grosso 《The Journal of the Operational Research Society》1998,49(10):1101-1106
This paper deals with the single machine total tardiness problem. From Emmons’ basic dominance conditions a new partition theorem is derived which generalises Lawler’s decomposition rule and leads to a new double decomposition procedure. This procedure is embedded into a branch and bound method which applies a new lower bound based on due dates reassignment. The branch and bound method is tested on problems with size up to 150 jobs. 相似文献
149.
Della Wai-mei Sin Wai-hong Fung Ya-yin Choi Chi-ho Lam Yiu-chung Wong 《Microchemical Journal》2004,77(1):63-70
A high throughput thermal gravimetric method was developed to measure the carbonaceous aerosols and particulates collected on filters. Representative portions or the whole piece of a loaded or blank filter was sampled and conditioned at 105±5 °C for 4 h to drive away water moisture. The sample was then treated at 550±10 °C for 4 h. After each of the heat treatment steps, the sample was conditioned in a humidity and temperature-controlled cabinet for 12 h till constant weight. The weight of the filter before and after the heated treatment was measured and the weight difference between the treatment at 550 and 105 °C was calculated as the weight of the carbon containing substances (CCS). Reference chemical standards and certified reference materials SRM 1649a and 1650a were used to validate the method. CCS concentrations of real aerosol samples collected in the city of Hong Kong during the summer of 2001 were also measured, compared and correlated with the concentrations of total carbon (TC), elemental carbon (EC) and organic carbon (OC) of the samples determined using a thermal optical transmittance (TOT) method as specified in NIOSH method 5040. The weight of organic compounds in airborne particulate matters is usually estimated by multiplying the weight of TC, which is determined by thermal/thermal optical methods, by a factor of 1.2 or 1.4. To this end, a correction factor of approximately 1.6 was found to relate TC to the measured values of CCS in aerosol samples collected in the urban atmosphere of Hong Kong. The proposed procedure for measurement of CCS is simple, easy to follow and requires simple laboratory instrumentation. Typically, the analysis of more than 100 filter samples can be completed within three working days with minimal attention. 相似文献
150.