全文获取类型
收费全文 | 3193篇 |
免费 | 423篇 |
国内免费 | 121篇 |
专业分类
化学 | 385篇 |
晶体学 | 3篇 |
力学 | 101篇 |
综合类 | 26篇 |
数学 | 1159篇 |
物理学 | 2063篇 |
出版年
2023年 | 25篇 |
2022年 | 64篇 |
2021年 | 64篇 |
2020年 | 61篇 |
2019年 | 73篇 |
2018年 | 57篇 |
2017年 | 92篇 |
2016年 | 93篇 |
2015年 | 89篇 |
2014年 | 185篇 |
2013年 | 210篇 |
2012年 | 153篇 |
2011年 | 217篇 |
2010年 | 148篇 |
2009年 | 172篇 |
2008年 | 235篇 |
2007年 | 244篇 |
2006年 | 187篇 |
2005年 | 151篇 |
2004年 | 128篇 |
2003年 | 129篇 |
2002年 | 127篇 |
2001年 | 100篇 |
2000年 | 95篇 |
1999年 | 92篇 |
1998年 | 106篇 |
1997年 | 49篇 |
1996年 | 56篇 |
1995年 | 30篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 10篇 |
排序方式: 共有3737条查询结果,搜索用时 15 毫秒
91.
T. Van Cauteren J. Ryckebusch B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):613-615
We present some of our results for the electromagnetic properties of excited Σ hyperons, computed within the framework of the Bonn constituent-quark model, which is based on the Bethe-Salpeter approach.
The seven parameters entering the model are fitted against the best-known baryon masses. Accordingly, the results for the
form factors and helicity amplitudes are genuine predictions. We compare with the scarce experimental data available and discuss
the processes in which Σ
*'s may play an important role. 相似文献
92.
I. K. Bensafa P. Achenbach M. Ases Antelo C. Ayerbe D. Baumann R. Böhm D. Bosnar E. Burtin X. Defaÿ N. D'Hose M. Ding M. O. Distler L. Doria H. Fonvieille J. M. Friedrich J. Friedrich J. García Llongo P. Janssens G. Jover Mañas M. Kohl G. Laveissière M. Lloyd M. Makek J. Marroncle H. Merkel P. Merle U. Müller L. Nungesser B. Pasquini R. Pérez Benito J. Pochodzalla M. Potokar G. Rosner S. Sánchez Majos M. Seimetz S. Širca T. Spitzenberg G. Tamas R. Van de Vyver L. Van Hoorebeke Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):69-75
The beam-helicity asymmetry has been measured simultaneously for the reactions
p→epγ and
p→epπ
0 in the Δ(1232)-resonance region at Q
2 = 0.35(GeV/c)2. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The
results are compared with calculations based on dispersion relations for virtual Compton scattering and with the MAID model
for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining
discrepancies may be ascribed to an imperfect parametrization of some γ
(*)
N→πN multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and π
0) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization. 相似文献
93.
Details of the reactive processes by which TiC and TiN microclusters are formed from precursor molecules in the gas phase are not clearly understood. We have performed ab initio calculations based on density functional theory methods in order to get some insight into the chemical reactions of precursor molecules. Using microcanonical molecular-dynamics we have simulated scattering processes between molecules consisting of the elements Ti, Cl, N and H. The simulations show that fluctuations of the kinetic energy can be large enough to break up bonds at moderate temperatures. 相似文献
94.
《Comptes Rendus Physique》2013,14(5):425-437
A multi-sensor test-bench for determining the SAR (specific absorption rate) due to wireless devices emitting in equivalent human tissues is presented. Real-time SAR assessment is proposed considering a spatially distributed multiprobe test-bench. In comparison with a multi-axial robot SAR system, the proposed one does not require any displacement, thus reducing drastically acquisition time, once parallel data acquisition and interpolation techniques are employed for accelerating measurements. 相似文献
95.
The effect of a thermal reservoir is investigated on a bipartite Gaussian state. We derive a pre-Lindblad master equation in the non-rotating wave approximation for the system. We then solve the master equation for a bipartite harmonic oscillator Hamiltonian with entangled initial state. We show that for strong damping the loss of entanglement is the same as for freely evolving particles. However, if the damping is small, the entanglement is shown to oscillate and eventually tend to a constant non-zero value. 相似文献
96.
介绍了EAST 装置上的384 道(极向24 道径向16 道)的外差混频式电子回旋辐射成像诊断系统及其在EAST 及其复杂的电磁环境中的运行情况。在低杂波电流驱动期间,高灵敏度的电子回旋辐射成像系统受到严重干扰以至于无法提供正确的实验数据。通过优化系统各模块的接地、外加多层铜网屏蔽等措施,使得ECEI 系统屏蔽效能与改善之前相比提高了40dB,基本保障了EAST 装置上电子回旋辐射成像诊断的正常工作。 相似文献
97.
Quantum Bayesian computation is an emerging field that levers the computational gains available from quantum computers. They promise to provide an exponential speed-up in Bayesian computation. Our article adds to the literature in three ways. First, we describe how quantum von Neumann measurement provides quantum versions of popular machine learning algorithms such as Markov chain Monte Carlo and deep learning that are fundamental to Bayesian learning. Second, we describe quantum data encoding methods needed to implement quantum machine learning including the counterparts to traditional feature extraction and kernel embeddings methods. Third, we show how quantum algorithms naturally calculate Bayesian quantities of interest such as posterior distributions and marginal likelihoods. Our goal then is to show how quantum algorithms solve statistical machine learning problems. On the theoretical side, we provide quantum versions of high dimensional regression, Gaussian processes and stochastic gradient descent. On the empirical side, we apply a quantum FFT algorithm to Chicago house price data. Finally, we conclude with directions for future research. 相似文献
98.
从交叉谱密度矩阵的传输公式出发,对多色矢量高斯-谢尔模型(GSM)光束的焦移和焦开关作了详细的研究.插入偏振片之前,多色矢量高斯-谢尔模型(GSM)光束通过硬边光阑透镜分离光学系统后,有焦移,但无焦开关;而插入偏振片之后,会出现焦开关.改变偏振片的旋转角度可以控制焦开关的特性. 相似文献
99.
Nonlinear systems with correlated stochastic parameters are approximated by simpler systems. This method is an extension of an earlier version of statistical replacement and statistical linearization. The extended method is applicable to systems with correlated fluctuations. We show how this general method reduces to the earlier methods in special cases. 相似文献
100.