全文获取类型
收费全文 | 10110篇 |
免费 | 1391篇 |
国内免费 | 856篇 |
专业分类
化学 | 2483篇 |
晶体学 | 92篇 |
力学 | 1598篇 |
综合类 | 224篇 |
数学 | 3503篇 |
物理学 | 4457篇 |
出版年
2024年 | 17篇 |
2023年 | 88篇 |
2022年 | 212篇 |
2021年 | 272篇 |
2020年 | 275篇 |
2019年 | 267篇 |
2018年 | 266篇 |
2017年 | 364篇 |
2016年 | 423篇 |
2015年 | 303篇 |
2014年 | 515篇 |
2013年 | 777篇 |
2012年 | 549篇 |
2011年 | 562篇 |
2010年 | 519篇 |
2009年 | 612篇 |
2008年 | 671篇 |
2007年 | 614篇 |
2006年 | 615篇 |
2005年 | 532篇 |
2004年 | 498篇 |
2003年 | 420篇 |
2002年 | 403篇 |
2001年 | 370篇 |
2000年 | 305篇 |
1999年 | 286篇 |
1998年 | 244篇 |
1997年 | 202篇 |
1996年 | 200篇 |
1995年 | 162篇 |
1994年 | 127篇 |
1993年 | 97篇 |
1992年 | 91篇 |
1991年 | 73篇 |
1990年 | 70篇 |
1989年 | 69篇 |
1988年 | 47篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 23篇 |
1984年 | 31篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 29篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
HOU Zhao-Yu GUO Ai-Qiang 《理论物理通讯》2007,47(4):690-694
We modify the square of virtual photon four-momentum by using nuclear binding energy formula, and calculate the effect of nuclear binding energy to K factor and Compton subprocess and annihilate subprocess in A-A collision Drell-Yan process. The outcome indicates that the effect of nuclear binding energy to K factor is obvious in little x region and it would disappear gradually as x increases. 相似文献
102.
The shock structure problem is one of the classical problems of fluid mechanics and at least for non-reacting dilute gases it has been considered essentially solved. Here we present a few recent findings, to show that this is not the case. There are still new physical effects to be discovered provided that the numerical technique is general enough to not rule them out a priori. While the results have been obtained for dense fluids, some of the effects might also be observable for shocks in dilute gases. 相似文献
103.
本文得到复流形局部q-凸楔形上(r,s)型微分形式的带权的同伦公式和(r,s)型的方程的带权的连续解,并给出(r,s)型微分形式的不含边界积分的新的带权的同伦公式和(r,s)型的方程的新的带权的连续解.这些新的带权公式尤其适用于具有非光滑边界的局部q-凸楔形,这时不但可以避免边界积分的复杂估计,而且积分密度也不必在边界有定义,只要在区域上有定义就行.其次,引进权因子,带权的积分公式在应用上(比如在函数的插值方面)具有更大的灵活性. 相似文献
104.
Heat Kernel Asymptotics of Zaremba Boundary Value Problem 总被引:1,自引:0,他引:1
The Zaremba boundary-value problem is a boundary value problem for Laplace-type second-order partial differential operators
acting on smooth sections of a vector bundle over a smooth compact Riemannian manifold with smooth boundary but with discontinuous
boundary conditions, which include Dirichlet boundary conditions on one part of the boundary and Neumann boundary conditions
on another part of the boundary. We study the heat kernel asymptotics of Zaremba boundary value problem. The construction
of the asymptotic solution of the heat equation is described in detail and the heat kernel is computed explicitly in the leading
approximation. Some of the first nontrivial coefficients of the heat kernel asymptotic expansion are computed explicitly.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
105.
Formulas for calculating the spectral characteristics of waveguide arrays, which are incorporated into waveguide spectrum analyzers based on planar waveguides, channel waveguides, and fiber optical waveguides, are derived taking into account the contribution of both the waveguide dispersion and the material dispersion to the dispersion factor. These formulas are used to study the dependence of the dispersion factor on the waveguide-system parameters for specific models of waveguide arrays. It is shown that consideration of contributions of the waveguide dispersion and material dispersion can affect profoundly the spectral characteristics of waveguide arrays. 相似文献
106.
基于Karhunen-Loève变换和小波谱特征矢量量化的三维谱像数据压缩 总被引:1,自引:1,他引:0
提出了基于Karhunen Lo埁ve变换的小波谱特征矢量量化三维谱像数据压缩方法耍幔颍瑁酰睿澹?Lo埁ve变换 /小波变换 /小波谱特征矢量量化方法应用了Karhunen Lo埁ve变换的消除谱相关性优良性能 ,应用二维小波变换消除空间相关性 ,在小波变换域内应用二维集分割嵌入块编码和一维谱特征矢量量化对三维谱像数据压缩 ,获得较高的压缩性能。实验结果表明 :Karhunen Lo埁ve变换 /小波变换 /小波谱特征矢量量化编码比Karhunen Lo埁ve变换 /小波变换 /改进对块零树编码和Karhunen Lo埁ve变换 /小波变换 /快速矢量量化编码方法在同样压缩比条件下 ,峰值信噪比提高 2dB和 1dB以上 ,而速度提高了 1.5和 8倍 ,整体压缩性能有较大的提高 相似文献
107.
《Magnetic resonance in chemistry : MRC》2003,41(8):599-602
Gradient‐enhanced pulse schemes are presented for the detection of quaternary and methylene carbons. The new pulse schemes permit the detection of quaternary and methylene (—CH2) carbons or CH2 carbons alone from a single experiment. Efficient suppression of CH and CH3 carbons in all the pulse schemes is achieved by creating their antiphase magnetization and then dephasing using gradients. In the pulse schemes for detection of only CH2 carbons, the quaternary carbons are also suppressed either by dephasing using gradients or by rendering them unobservable by retaining in longitudinal order. The experimental results of the gradient pulse schemes are demonstrated on cholesteryl acetate and cyclosporin A. These one‐dimensional techniques, because of their simplicity and the ease of performing the experiments, can be important for routine chemical applications. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
108.
Tohru OishiHiroshi Tsuchikawa Michio Murata Manabu YoshidaMasaaki Morisawa 《Tetrahedron letters》2003,44(34):6387-6389
A chemoattractant candidate named sperm-activating and attracting factor (SAAF) from the eggs of ascidian Ciona intestinalis, was synthesized from chenodeoxycholic acid in 16 steps. The present synthesis led to the unambiguous structure determination of SAAF to be (3R,4R,7R,25S)-3,4,7,26-tetrahydroxycholestane-3,26-disulfate. The synthetic pure specimen was also used to confirm the dual sperm-activating and attracting activity. 相似文献
109.
110.
Elastic electron scattering on the exotic light nucleus28S is investigated in the plane wave Born approximation. The variation of the squared form factors of28S with momentum transfer is compared with that of32S. It is found that the behavior of the form factors near the second minimum (with a moderate momentum transfer) is sensitive
to the alteration of the charge density distribution of halo protons in28S. This indicates that elastic electron scattering can be a good probe of the structure of proton-halo nuclei. 相似文献