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991.
Y.Y. Sun I. Rusakova R.L. Meng Y. Cao P. Gautier-Picard C.W. Chu 《Physica C: Superconductivity and its Applications》1994,230(3-4):435-442
We have carried out a systematic structural, electric, and magnetic study on Y---Pd---B---C samples with different compositions with emphasis on the as-cast and annealed YPd5B3C0.3 which was first reported to superconduct at 23 K by Cava et al. We found that the tetragonal body-centered YPd2B2C with lattice parameters a=3.71 Å and c=10.81 Å is the phase responsible for the 23 K superconductivity and that YPd2B2C is metastable, which is consistent with the suggestion made by Cava et al. [1]: it is not stable at high temperatures nor stabilizable by Ni doping, although its isostructural compound, YNi2B2C, exists. Two new phases with Y:Pd ratios of 1:7 and 2:3, respectively, have also bee detected. 相似文献
992.
Daomin Cao Zhongyuan Liu Juncheng Wei 《Archive for Rational Mechanics and Analysis》2014,212(1):179-217
In this paper, we construct stationary classical solutions of the incompressible Euler equation approximating singular stationary solutions of this equation. This procedure is carried out by constructing solutions to the following elliptic problem $$\left\{\begin{array}{l@{\quad}l} -\varepsilon^2 \Delta u = \sum\limits_{i=1}^m \chi_{\Omega_i^{+}} \left(u - q - \frac{\kappa_i^{+}}{2\pi} {\rm ln} \frac{1}{\varepsilon}\right)_+^p\\ \quad - \sum_{j=1}^n \chi_{\Omega_j^{-}} \left(q - \frac{\kappa_j^{-}}{2\pi} {\rm \ln} \frac{1}{\varepsilon} - u\right)_+^p , \quad \quad x \in \Omega,\\ u = 0, \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad x \in \partial \Omega,\end{array}\right.$$ where p > 1, ${\Omega \subset \mathbb{R}^2}$ is a bounded domain, ${\Omega_i^{+}}$ and ${\Omega_j^{-}}$ are mutually disjoint subdomains of Ω and ${\chi_{\Omega_i^{+}} ({\rm resp}.\; \chi_{\Omega_j^{-}})}$ are characteristic functions of ${\Omega_i^{+}({\rm resp}. \;\Omega_j^{-}})$ , q is a harmonic function. We show that if Ω is a simply-connected smooth domain, then for any given C 1-stable critical point of Kirchhoff–Routh function ${\mathcal{W}\;(x_1^{+},\ldots, x_m^{+}, x_1^{-}, \ldots, x_n^{-})}$ with ${\kappa^{+}_i > 0\,(i = 1,\ldots, m)}$ and ${\kappa^{-}_j > 0\,(j = 1,\ldots,n)}$ , there is a stationary classical solution approximating stationary m + n points vortex solution of incompressible Euler equations with total vorticity ${\sum_{i=1}^m \kappa^{+}_i -\sum_{j=1}^n \kappa_j^{-}}$ . The case that n = 0 can be dealt with in the same way as well by taking each ${\Omega_j^{-}}$ as an empty set and set ${\chi_{\Omega_j^{-}} \equiv 0,\,\kappa^{-}_j=0}$ . 相似文献
993.
Predictionofthechemicalreactivityandquantitativecalculationofmolecularreactiondynamicshavebeenaninteresingsubjectintheoreticalchemistry.Inthefiftiesandsixties,basedonthesimplemolecularorbital(MO)approach,thefrontierorbitaltheoryproposedbyFukuietal.[1]and… 相似文献
994.
995.
996.
Cao Huaixin Zhang Chengyang Guo Zhihua 《International Journal of Theoretical Physics》2021,60(7):2558-2572
Importance of quantum entanglement has been demonstrated in various applications. Usually, separability of a bipartite state is defined by its algebraic structure, i.e. a convex combination of product states. But it seems to be hard to check separability (equivalently, entanglement) of a state from its algebraic structure. In this note, we give some characterizations of separability of bipartite states based on POVM measurements. For bipartite pure states, we prove the separability, Bell locality, unsteerability and classical correlation are the same. As a consequence, every entangled pure bipartite state is always Bell nonlocal, steerable and quantum correlated.
相似文献997.
将四针状纳米ZnO作为吸收剂、环氧树脂为粘结剂制备成吸波涂层,分析了吸波涂层中的四针状纳米氧化锌含量及涂层厚度对吸波性能的影响,当涂层厚度为15mm时,吸收主要集中在15—18GHz波段;当涂层厚度增加到35mm后,样品的吸波性能提高明显,特别在6—11GHz之间的吸波性能提高显著,样品反射率小于-5dB的频率宽度达到136GHz(44—18GHz),其吸波性能相比较微米级ZnO有显著提高. 最后对四针状纳米氧化锌的吸波机理进行了讨论. 所研究的涂层在电磁波屏蔽方面具有较大的应用价值.
关键词:
四针状纳米ZnO
吸波性能
反射率
吸波机理 相似文献
998.
999.
Approach to the study of flavone di‐C‐glycosides by high performance liquid chromatography‐tandem ion trap mass spectrometry and its application to characterization of flavonoid composition in Viola yedoensis 下载免费PDF全文
Jie Cao Chengle Yin Yan Qin Zhihong Cheng Daofeng Chen 《Journal of mass spectrometry : JMS》2014,49(10):1010-1024
The mass spectrometric (MS) analysis of flavone di‐C‐glycosides has been a difficult task due to pure standards being unavailable commercially and to that the reported relative intensities of some diagnostic ions varied with MS instruments. In this study, five flavone di‐C‐glycoside standards from Viola yedoensis have been systematically studied by high performance liquid chromatography‐electrospray ionization‐tandem ion trap mass spectrometry (HPLC‐ESI‐IT‐MSn) in the negative ion mode to analyze their fragmentation patterns. A new MS2 and MS3 hierarchical fragmentation for the identification of the sugar nature (hexoses or pentoses) at C‐6 and C‐8 is presented based on previously established rules of fragmentation. Here, for the first time, we report that the MS2 and MS3 structure‐diagnostic fragments about the glycosylation types and positions are highly dependent on the configuration of the sugars at C‐6 and C‐8. The base peak (0,2X10,2X2? ion) in MS3 spectra of di‐C‐glycosides could be used as a diagnostic ion for flavone aglycones. These newly proposed fragmentation behaviors have been successfully applied to the characterization of flavone di‐C‐glycosides found in V. yedoensis. A total of 35 flavonoid glycosides, including 1 flavone mono‐C‐hexoside, 2 flavone 6,8‐di‐C‐hexosides, 11 flavone 6,8‐di‐C‐pentosides, 13 flavone 6,8‐C‐hexosyl‐C‐pentosides, 5 acetylated flavone C‐glycosides and 3 flavonol O‐glycosides, were identified or tentatively identified on the base of their UV profiles, MS and MSn (n = 5) data, or by comparing with reference substances. Among these, the acetylated flavone C‐glycosides were reported from V. yedoensis for the first time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
Dong Cao Huogao Huang Ming Hu Lin Cui Fanglan Geng Ziyu Rao Hongyun Niu Yaqi Cai Yuehui Kang 《Analytica chimica acta》2015
Natural organic matter (NOM) is a complex and non-uniform mixture of organic compounds which plays an important role in environmental processes. Due to the complexity, it is challenging to obtain fully detailed structural information about NOM. Although Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has been demonstrated to be a powerful tool for providing molecular information about NOM, multiple ionization methods are needed for comprehensive characterization of NOM at the molecular level considering the ionizing selectivity of different ionization methods. This paper reports the first use of matrix assisted laser desorption/ionization (MALDI) method coupled with FT-ICR-MS for molecular characterization of NOM within a mass range of 200–800 Da. The mass spectral data obtained by MALDI were systematically compared with data generated by electrospray ionization (ESI). It showed that complementary molecular information about NOM which could not be detected by ESI, were provided by MALDI. More unsaturated and aromatic constituents of NOM with lower O/C ratio (O/C ratio < 0.5) were preferentially ionized in MALDI negative mode, whereas more polar constituents of NOM with higher O/C ratio were preferentially ionized in ESI negative mode. Molecular anions of NOM appearing at even m/z in MALDI negative ion mode were detected. The results show that NOM molecules with aromatic structures, moderate O/C ratio (0.7 > O/C ratio > 0.25) and lower H/C ratio were liable to form molecular anions at even m/z, whereas those with higher H/C ratio are more likely to form deprotonated ions at odd m/z. It is speculated that almost half of the NOM molecules identified by MALDI may be aromatic or condensed aromatic compounds with special groups which are liable to absorb electron from other molecules to generate free radical anions during MALDI ionization. 相似文献