全文获取类型
收费全文 | 7054篇 |
免费 | 977篇 |
国内免费 | 982篇 |
专业分类
化学 | 3247篇 |
晶体学 | 39篇 |
力学 | 238篇 |
综合类 | 29篇 |
数学 | 2954篇 |
物理学 | 2506篇 |
出版年
2024年 | 4篇 |
2023年 | 228篇 |
2022年 | 180篇 |
2021年 | 227篇 |
2020年 | 326篇 |
2019年 | 213篇 |
2018年 | 245篇 |
2017年 | 245篇 |
2016年 | 289篇 |
2015年 | 288篇 |
2014年 | 468篇 |
2013年 | 551篇 |
2012年 | 623篇 |
2011年 | 625篇 |
2010年 | 583篇 |
2009年 | 577篇 |
2008年 | 553篇 |
2007年 | 552篇 |
2006年 | 455篇 |
2005年 | 299篇 |
2004年 | 201篇 |
2003年 | 181篇 |
2002年 | 154篇 |
2001年 | 186篇 |
2000年 | 115篇 |
1999年 | 125篇 |
1998年 | 99篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 31篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 41篇 |
1991年 | 38篇 |
1990年 | 36篇 |
1989年 | 26篇 |
1988年 | 27篇 |
1987年 | 27篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1959年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有9013条查询结果,搜索用时 46 毫秒
21.
《Journal of Functional Analysis》2019,276(12):3832-3857
We give an estimate for sums appearing in the Nyman–Beurling criterion for the Riemann Hypothesis. These sums contain the Möbius function and are related to the imaginary part of the Estermann zeta function. The estimate is remarkably sharp in comparison to other sums containing the Möbius function. The bound is smaller than the trivial bound – essentially the number of terms – by a fixed power of that number. The exponent is made explicit. The methods intensively use tools from the theory of continued fractions and from the theory of Fourier series. 相似文献
22.
23.
Nonlinear Dynamics - Darboux and Bäcklund transformations on integrable couplings are formulated and generalized. The generalization of the theory pertains to spectral problems where the... 相似文献
24.
Jian-Ping Li Lian-Zhong Deng Ye Zheng Peng-Peng Ding Tian-Qing Jia Zhen-Rong Sun Jian-Rong Qiu Shi-An Zhang 《Frontiers of Physics》2020,15(2):22603-68
The spectral phase of the femtosecond laser field is an important parameter that affects the up-conversion(UC)luminescence efficiency of dopant lanthanide ions.In this work,we report an experi-mental study on controlling the UC lmiiinescence efficiency in Sm^3+:NaYF4 glass by 800-nm femtosec-ond laser pulse shaping using spectral phase modulation.The optimal phase control strategy efficiently enhances or suppresses the UC luminescence intensity.Based on the laser-power dependence of the UC luminescence intensity and its comparison with the luminescence spectrum under direct 266-nm fem-tosecond lciser irradiation,we propose herein an excitation model combining non-resonant two-photon absorption with resonance-media ted three-photon absorption to explain the experimental observations. 相似文献
25.
《中国化学快报》2020,31(8):2155-2158
Detection of trace-level hydrogen sulfide (H2S) gas is of great importance whether in industrial production or disease diagnosis. This research presents a novel H2S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H2S in real-time. The sensor consists of two integrated resonant microcantilever sensors with different functions. One cantilever sensor can identify H2S by outputting positive frequency shift signals, while the other cantilever sensor will detect H2S as a normally used cantilever sensor with negative frequency shifts. Combined the two cantilever sensors, the proposed gas sensor can distinguish H2S from a variety of common gases, and the detection limit to H2S of the sensor is as sensitive as below 1 ppb. 相似文献
26.
The friction at the liquid-solid interfaces is widely involved in various phenomena ranging from nanometer to micrometer scales. By the molecular dynamic(MD)simulation, the friction properties of liquid-solid interfaces at the molecular level are calculated via the Green-Kubo relation. It is found that the system size will influence the value of the friction coefficient, especially for the solid surfaces with the larger polar charge. The value of the friction coefficient decreases with the increase in the system size and converges at large system sizes. The large polar charge will lead to a significant friction coefficient. However, the diffusion of water molecules on this surface is almost a constant, indicating that the diffusion coefficient seems to be independent of the system size and polar charge. This work provides insights for the selection of the system size in modeling the frictional properties of hydrophobic/hydrophilic surfaces. 相似文献
27.
Inside Back Cover: Stepwise Assembly of MII7 Clusters Revealed by Mass Spectrometry,EXAFS, and Crystallography (Chem. Eur. J. 51/2016) 下载免费PDF全文
28.
29.
Quantum networks strongly depend on the efficient interactions between flying photonic quantum bits and local long-lived atomic matter nodes. To achieve the efficient quantum interfaces between polarization-encoding photons and spin-encoding atoms, polarization-entangled paired photons with a bandwidth narrower than the natural linewidth of the atoms are highly required. In this paper, we review the generation of subnatural-linewidth polarization-entangled paired photons through spontaneous four-wave mixing with cold atoms, which is very suitable for the application of quantum networks. 相似文献
30.
In the presence of the inexpensive and non‐toxic polymethylhydrosiloxane, the combination of copper(II) acetate and a chiral diphosphine displayed high catalytic efficiency in the asymmetric hydrosilylation of a series of aromatic ketones in air atmosphere and at room temperature. (R)‐1‐Arylethanols were obtained with up to 99% yield and 93% enantiomeric excess. Meanwhile, the electron effect and steric hindrance of substituents on the aromatic ring had an interesting influence on both the yields and enantioselectivities. Furthermore, a possible mechanism was presented to explain the influence of some key factors on the reaction. 相似文献