全文获取类型
收费全文 | 181790篇 |
免费 | 37366篇 |
国内免费 | 26377篇 |
专业分类
化学 | 119745篇 |
晶体学 | 2206篇 |
力学 | 12015篇 |
综合类 | 654篇 |
数学 | 21882篇 |
物理学 | 89031篇 |
出版年
2024年 | 749篇 |
2023年 | 2786篇 |
2022年 | 4403篇 |
2021年 | 4715篇 |
2020年 | 5154篇 |
2019年 | 5528篇 |
2018年 | 4901篇 |
2017年 | 5156篇 |
2016年 | 7279篇 |
2015年 | 7339篇 |
2014年 | 8289篇 |
2013年 | 11798篇 |
2012年 | 13562篇 |
2011年 | 15220篇 |
2010年 | 15321篇 |
2009年 | 15217篇 |
2008年 | 9749篇 |
2007年 | 8783篇 |
2006年 | 7969篇 |
2005年 | 7376篇 |
2004年 | 6927篇 |
2003年 | 5490篇 |
2002年 | 5059篇 |
2001年 | 5025篇 |
2000年 | 3970篇 |
1999年 | 4524篇 |
1998年 | 3874篇 |
1997年 | 3574篇 |
1996年 | 4042篇 |
1995年 | 4074篇 |
1994年 | 4082篇 |
1993年 | 3858篇 |
1992年 | 3374篇 |
1991年 | 2958篇 |
1990年 | 2461篇 |
1989年 | 2354篇 |
1988年 | 2244篇 |
1987年 | 1481篇 |
1986年 | 1534篇 |
1985年 | 1163篇 |
1984年 | 1210篇 |
1983年 | 503篇 |
1982年 | 1013篇 |
1981年 | 835篇 |
1980年 | 841篇 |
1979年 | 569篇 |
1978年 | 564篇 |
1977年 | 660篇 |
1976年 | 1077篇 |
1972年 | 549篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
We investigate low-temperature behaviors of a system with chirality-pair interaction on a one-dimensional lattice. In the course of the investigation, we evaluate asymptotic forms of the characteristic values of the integral equation satisfied by the Mathieu functions. It turns out that the low-temperature behavior of correlation length of the chirality-pair correlation function is different from the one for the Ising model of spin ±1 but akin to the one for the Ising model of infinite spin. 相似文献
112.
This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out. 相似文献
113.
B. Griepink E. A. Maier P. Quevauviller H. Muntau 《Fresenius' Journal of Analytical Chemistry》1991,339(9):599-603
Summary The Community Bureau of Reference (BCR) has undertaken the production of a wide range of certified reference materials (CRMs) for the improvement of accuracy and measurement harmony in various areas of concern at European Community level. This paper provides an overview of the sectors of the BCR-programme in the field of environment i.e. for water systems (water, sediment, biota), soil analysis (soil, fertiliser, waste), plant analysis (aquatic and terrestrial plants), analysis related to animals (e.g. muscle or liver) or man (e.g. industry and food). 相似文献
114.
115.
116.
The occurrence of charge on recoil56Mn produced by the (n,γ) reaction in polycrystalline potassium permanganate has been examined using the ‘charge plate technique’.
From considerations of capture gamma ray decay schemes and internal conversion it appears that, in a condensed medium, the
recoil atom develops charge after losing much of its initial kinetic energy which allows collection on charged electrodes.
Preliminary findings were presented at the International Symposium on Radiochemistry and Radiation Chemistry, RC-41 BARC,
Bombay, Feb. 4–6 (1991). 相似文献
117.
The Stokes motions of three-dimensional screw-sensed slender particles in a homogeneous shear field are investigated, including the effects of buoyancy. Conclusions are drawn about the possibility of achieving a separation of mixtures of right- and left-handed particles. The linearity of the Stokes equations allows complex flows to be solved by adding the effects of the several terms which describe the flow in which the particle is immersed. The homogeneous shear flow considered here consists of three such terms; solutions for a series of 12 unit motions are sufficient to determine the hydrodynamic resistance tensors. The forces and torques experienced by screw-sensed particles are calculated from these 51 resistance tensors, using slender-filament theory. The results allow an estimate of the range of buoyancy parameters for which gravitational sedimentation can be neglected. The fundamental component of the particle motion is a rotation, at approximately the same angular velocity as that of the fluid. Superimposed on this are variations, of large period, in the particle orientation. A phase plane analysis is used to find the terminal orientations. Very long calculation times are required for the phase portrait. An approximate method based on azimuthally-averaged equations is developed to avoid the requirements for long time integration. 相似文献
118.
Let M be a symplectic manifold with a Hamiltonian circle action with isolated fixed points. We prove that σ (M) = b0(M) − b2(M) + b4(M) − b6(M) + … where σ (M) is the signature of M and bi(M) is the ith Betti number of M. 相似文献
119.
P. J. Wagstaffe A. Boenke E. Schnug A. S. Lindsey 《Fresenius' Journal of Analytical Chemistry》1992,344(1-2):1-7
Summary The sulphur content of three rapeseed reference materials has been certified on the basis of measurements made by inductively
coupled plasma-optical emission spectroscopy, isotope-dilution mass spectrometry and ion chromatography. Their suitability
for the calibration of x-ray fluorescence spectrometers used for measuring sulphur in rapeseed samples was established. 相似文献
120.
The blends composed of polyamide 6 (PA6) and polyamide 66 (PA66) were obtained using two different preparation methods, one of which was the melt‐mixing through a twin‐screw extruder and the subsequent injection molding; and the other, the in situ blending through anionic polymerization of ε‐caprolactam in the presence of PA66. For the former, there existed a remarkable improvement in toughness but a drastic drop in strength and modulus; however, for the latter, a reverse but less significant trend of mechanical properties change appeared. Various characterizations were conducted, including the analyses of crystalline morphology, crystallographic form, and crystallization and melting behaviors using polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively; observation of morphology of fractured surface with scanning electron microscope (SEM); measurement of glass transition through dynamic mechanical analysis (DMA); and the intermolecular interaction as well as the interchange reaction between the two components by Fourier transform infrared spectrometry (FT‐IR) and 13C solution NMR. The presence and absence of interchange reaction was verified for the in situ and melt‐mixed blends, respectively. It is believed that the transreaction resulted in a drop in glass transition temperature (Tg) for the in situ blends, contrary to an increase of Tg with increasing PA66 content for the melt‐mixed ones. And the two kinds of fabrication methods led to significant differences in the crystallographic form, spherulite size and crystalline content and perfection as well. Accordingly, it is attempted to explain the reasons for the opposite trends of changes in the mechanical properties for these two blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1176–1186, 2007 相似文献