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191.
V. A. Belavin 《Theoretical and Mathematical Physics》2007,152(3):1275-1285
We present explicit recursion relations for the four-point superconformal block functions that are essentially particular
contributions of the given conformal class to the four-point correlation function. The approach is based on the analytic properties
of the superconformal blocks as functions of the conformal dimensions and the central charge of the superconformal algebra.
We compare the results with the explicit analytic expressions obtained for special parameter values corresponding to the truncated
operator product expansion. These recursion relations are an efficient tool for numerically studying the four-point correlation
function in superconformal field theory in the framework of the bootstrap approach, similar to that in the case of the purely
conformal symmetry.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 3, pp. 476–487, September, 2007. 相似文献
192.
193.
L.?Marié J.?Burguete F.?DaviaudEmail author J.?Léorat 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(4):469-485
A numerical study of the magnetic induction equation has
been performed on von Kármán type flows. These flows are
generated by two co-axial counter-rotating propellers in
cylindrical containers. Such devices are currently used in the
von Kármán sodium (VKS) experiment designed to study dynamo
action in an unconstrained flow. The mean velocity fields have
been measured for different configurations and are introduced in
a periodic cylindrical kinematic dynamo code. Depending on the
driving configuration, on the poloidal to toroidal flow ratio
and on the conductivity of boundaries, some flows are observed
to sustain growing magnetic fields for magnetic Reynolds numbers
accessible to a sodium experiment. The response of the flow to
an external magnetic field has also been studied: The results
are in excellent agreement with experimental results in the
single propeller case but can differ in the two propellers case. 相似文献
194.
Detecting pipe changes via acoustic matched field processing 总被引:1,自引:0,他引:1
Detecting pipe irregularities such as intrusions can be challenging. However, subtle changes can be identified in the complex acoustic fields measured over a range of frequencies and over a time interval given an “array” of receivers. In particular, for two receivers one can coherently process the signals via matched field processing (MFP) to infer whether or not there have been changes such as new intrusions relative to undisturbed fields measured earlier. There is no acoustic modelling of the fields required, only the simple linear processor is applied, and only test data (five scenarios) are used in this demonstration. A key advantage to using MFP plus two (or more) microphones is that absolute sound levels need not be carefully measured. 相似文献
195.
Magnetic field effect in conjunction with laser flash photolysis have been used for studying interactions of 9,10-anthraquinone and 2-methyl 1,4-naphthoquinone (menadione) with a DNA base, thymine (Thy) and its nucleoside, thymidine (dThd). Irrespective of medium Thy has been found to support both electron transfer (ET) and hydrogen abstraction with the quinones while dThd has exhibited a complete reluctance towards ET. This unique behavior of dThd has been attributed to a failure in attaining aromaticity by virtue of keto-enol tautomerism upon addition of a sugar moiety. Electron withdrawing effect of sugar unit is also considered responsible for reduction of ET from dThd. Again both Thy and dThd have exhibited hydrogen abstraction in homogeneous medium, which is normally unexpected. The above behaviors of the bases have been explained on the basis of their chemical structures. 相似文献
196.
解决声场参数同时具有模糊性和随机性的问题,实现模糊随机声场声压响应的预测,引入了信息熵理论,利用信息熵的等效转换,将模糊随机声场转化为纯随机声场或者纯模糊声场进行求解,推导了基于摄动法的二维随机声场和模糊声场的有限元计算公式。以模糊随机参数下的二维管道声场模型和某轿车二维声腔模型为例进行了数值计算,所得结果与蒙特卡洛法(Monte Carlo Method)所预测声压变化范围基本一致,同时,转化为纯随机声场和纯模糊声场所求得声压响应变化范围也基本一致,说明了本文方法计算结果的准确性。因此本文方法能很好地应用于模糊随机参数下二维声场的预测,具有重要的工程应用价值。 相似文献
197.
扫描透射电子显微术是目前应用最广泛的电子显微表征手段之一,具有分辨率高、对化学成分敏感和图像直观易解释等特点。其中高分辨扫描电子显微镜可以直接获得原子分辨率的Z 衬度像,结合X射线能谱(EDS)和电子能量损失谱(EELS),可在亚埃尺度上对材料的原子和电子结构进行分析。文章简述了扫描透射电子显微镜的基本原理及其应用现状,重点论述了高角环形暗场(HAADF)和环形明场(ABF)像的成像原理、特征和应用。此外,文中还对原子尺度分辨率的X射线能谱及电子能量损失谱元素分析方法进行了简述。 相似文献
198.
Magnetic metal and metal oxide nanoparticles capped with alkylamines have been synthesized and characterized by transmission
electron microscopy. X-ray diffraction, energy dispersive X-ray analysis and magnetization measurements. Core-shell Pd-Ni
particles with composition, Pd561Ni3000, (diameter ∼3.3 nm) are superparamagnetic at 5 K and organize themselves into two-dimensional crystalline arrays. Similar
arrays are obtained with Pd561Ni3000Pd1500 nanoparticles containing an additional Pd shell. Magnetic spinel particles of γ-Fe2O3, Fe3O4 and CoFe2O4 of average diameters in the 4–6 nm range coated with octylamine are all supermagnetic at room temperature and yield close-packed
disordered arrays. Relatively regular arrays are formed by dodecylaminecapped Fe3O4 nanoparticles (∼8.6 nm diameter) while well-ordered hexagonal arrays were obtained with octylamine-covered Co3O4 nanoparticles (∼4.2 nm diameter). 相似文献
199.
R. Lefort A. Hédoux Y. Guinet E. Cochin M. Descamps 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):519-525
The first analysis of rapid intramolecular motions of triphenyl phosphite by 2H NMR is presented. The fragile slowing down of the primary relaxation is followed by a solid-echo method. The occurrence
of a fast reorientation of the phenyl side groups is demonstrated in the supercooled liquid state, identified as a two-fold
flip on the basis of simple lineshape simulations. Coexistence of both static and motionally averaged components in “two phase”
spectra indicate a broad distribution of correlation times for this relaxation. This dynamical behavior is shown to persist
in the glacial phase.
Received 28 May 2002 / Received in final form 1st October 2002
Published online 31 December 2002 相似文献
200.
G. Gottstein D.A. Molodov E. Rabkin L.S. Shvindlerman I. Snapiro 《Interface Science》2002,10(4):279-285
The effect of an induced magnetic moment due to grain boundary motion in a magnetic field was studied theoretically in a microscopic and a mesoscopic approximation. It was found that the induced moment generates a drag force on the boundary, which depends on the orientation of the magnetic field with regard to the crystal axis, as observed experimentally. However, the magnitude of the theoretically predicted dependency is much smaller than experimentally observed and even opposite with regard to the orientation dependence. Therefore, the electromagnetic drag can be neglected in comparison with other driving forces for grain boundary motion, but the effect may play a role for fast moving dislocations in a magnetic field. 相似文献