全文获取类型
收费全文 | 1813篇 |
免费 | 47篇 |
国内免费 | 14篇 |
专业分类
化学 | 1134篇 |
晶体学 | 4篇 |
力学 | 51篇 |
数学 | 421篇 |
物理学 | 264篇 |
出版年
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 40篇 |
2020年 | 32篇 |
2019年 | 29篇 |
2018年 | 22篇 |
2017年 | 18篇 |
2016年 | 63篇 |
2015年 | 38篇 |
2014年 | 36篇 |
2013年 | 89篇 |
2012年 | 85篇 |
2011年 | 138篇 |
2010年 | 68篇 |
2009年 | 63篇 |
2008年 | 115篇 |
2007年 | 111篇 |
2006年 | 93篇 |
2005年 | 70篇 |
2004年 | 62篇 |
2003年 | 51篇 |
2002年 | 43篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 20篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 24篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1970年 | 8篇 |
排序方式: 共有1874条查询结果,搜索用时 15 毫秒
1.
2.
Gabor Schmera Adi Bulsara David Pierson Frank Moss Enrico Di Cera 《Journal of statistical physics》1993,71(5-6):1179-1190
We consider the class of experiments which can be characterized by a Fokker-PIanck dynamics corresponding to the overdamped motion of a state point in a suitable stochastic potential. We assume that the general form of the potential is known (or can be guessed with reasonable accuracy), but that its parameters are to be determined experimentally by measurements made with a noisy instrument. This possible method for determining the potential parameters, which exploits the system's own internal stochastic motion in order to explore rapidly its available parameter space, is substantially more efficient than traditional methods involving time averages of single point measurements, and yet does not appear to have been previously considered. The method could be important when, for example, the experiment must be completed in a limited time owing either to the expense of the experimental materials or to the temporary stationarity of the preparation, situations which are commonly encountered in experimental biochemistry and biology. 相似文献
3.
4.
Giovanni Tartarini Alessandra Lena Davide Passaro Lorenzo Rosa Stefano Selleri Pier Faccin Enrico Maria Fabbri 《Optical and Quantum Electronics》2006,38(9-11):869-876
A comprehensive numerical tool has been developed for the evaluation of the performances of Radio over Fiber (RoF) links intended for wireless signal distribution.At the transmitter end an appropriate set of rate equations allows to model the optical source as a solitary laser or as an appropriately injection locked laser. The optical channel is modeled putting into account the combined effect of fiber dispersion, laser source non ideal performances (e.g. non-linear effects, frequency chirp), and quadratic detection of the receiving photodiode. The simulation model developed can be a useful tool at the design stage allowing a preliminary evaluation of the characteristics of real RoF links. 相似文献
5.
Technical cellulose-2.5-acetates (CA 2.5) were characterized regarding their carbohydrate composition in comparison to the raw material. The association of the CA 2.5 samples in acetone was studied by size exclusion chromatography (SEC) using various acetone grades and styrene divinylbenzene copolymer columns. In HPLC grade acetone with and without addition of 1% water up to three different pre-humps eluted in front of the main fraction of the polymer. The evaluation of the main peak by light scattering measurements resulted in high molar masses indicating that for these technical CA 2.5 samples even the main fraction is not dissolved without association. No pre-humps or association phenomena were observed after addition of 1 ppm LiBr to HPLC grade acetone or with p.a. grade acetone. In addition pre-hump enriched and pre-hump free fractions were isolated by fractionated precipitation. The carbohydrate composition of these fractions was determined and correlated with their association pattern in SEC investigations. 相似文献
6.
7.
Maria Benedetta Fadda Nicoletta Curreli Raffaello Pompei Antonio Rescigno Augusto Rinaldi Enrico Sanjust 《Applied biochemistry and biotechnology》1994,44(3):263-270
A highly active thermostable β-glucosidase was purified to homogeneity from a strain ofTrichoderma sp. The enzyme was an extracellular glycoprotein and showed hydrolytic activity toward several β-glucosides.
Cellobiose was found to be the substrate of choice for this enzyme. This finding could suggest future technological applications
of the purified protein. 相似文献
8.
A simple yet accurate method for calculating electrostatic potentials using the boundary element continuum dielectric method is presented. It is shown that the limiting factor in accuracy is not the evaluation of integrals involving the interaction between boundary elements but rather a proper estimation of the self-polarization of a patch upon itself. We derive a sum rule that allows us to calculate this important self-polarization term in a self-consistent and simple way. Intricate integration schemes used in previous treatments are consequently rendered unnecessary while concurrently achieving at least comparable accuracy over earlier methods. In some model systems for which analytic solutions are available, the computed surface polarization charge and reaction field energy are correct to better than six significant figures. An application of the method to the calculation of hydration free energies is presented. Good agreement with experimental values is obtained. 相似文献
9.
10.
Fabio Fantozzi Sauro Filippeschi Enrico Maria Latrofa 《Superlattices and Microstructures》2004,35(3-6):339
Upward and downward two-phase heat and mass transfer has been considered in the present paper. The heat and mass transfer with the condenser located below the evaporator has been obtained by inserting an accumulator tank in the liquid line of a loop thermosyphon and enforcing a pressure pulsation. In previous papers these heat transfer devices have been called pulsated two phase thermosyphons (PTPT). A mini PTPT has been experimentally investigated. It has shown a stable periodic heat transfer regime weakly influenced by the position of the condenser with respect to the evaporator. In contrast a classical loop mini thermosyphon (diameter of connecting pipes 4 mm) did not achieve a stable functioning for the investigated level differences between evaporator and condenser lower than 0.37 m. The present study shows that the functioning of a PTPT device does not directly depend on the level difference or the presence of noncondensable gas. In order to obtain a natural circulation in mini or micro loops, a periodically operating heat transfer regime should therefore be considered. 相似文献