全文获取类型
收费全文 | 15519篇 |
免费 | 574篇 |
国内免费 | 45篇 |
专业分类
化学 | 10553篇 |
晶体学 | 238篇 |
力学 | 498篇 |
综合类 | 1篇 |
数学 | 1187篇 |
物理学 | 3661篇 |
出版年
2024年 | 68篇 |
2023年 | 180篇 |
2022年 | 457篇 |
2021年 | 450篇 |
2020年 | 484篇 |
2019年 | 542篇 |
2018年 | 507篇 |
2017年 | 484篇 |
2016年 | 709篇 |
2015年 | 510篇 |
2014年 | 792篇 |
2013年 | 1326篇 |
2012年 | 1183篇 |
2011年 | 1206篇 |
2010年 | 811篇 |
2009年 | 628篇 |
2008年 | 751篇 |
2007年 | 759篇 |
2006年 | 598篇 |
2005年 | 516篇 |
2004年 | 398篇 |
2003年 | 338篇 |
2002年 | 271篇 |
2001年 | 166篇 |
2000年 | 141篇 |
1999年 | 108篇 |
1998年 | 77篇 |
1997年 | 106篇 |
1996年 | 102篇 |
1995年 | 75篇 |
1994年 | 74篇 |
1993年 | 99篇 |
1992年 | 100篇 |
1991年 | 81篇 |
1990年 | 73篇 |
1989年 | 73篇 |
1988年 | 53篇 |
1987年 | 49篇 |
1986年 | 42篇 |
1985年 | 63篇 |
1984年 | 64篇 |
1983年 | 53篇 |
1982年 | 49篇 |
1981年 | 37篇 |
1980年 | 45篇 |
1979年 | 64篇 |
1978年 | 49篇 |
1977年 | 53篇 |
1976年 | 42篇 |
1975年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
81.
We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics
expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not
change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction
significantly. 相似文献
82.
The high spin yrast states uptoJ=22+ in182,184,186Os are studied in a microscopic variational approach with number-conserved projected states. The energy spectra, quadrupole,
moments andB (E2) values are calculated by employing the Hamiltonian with quadrupole plus pairing interactions. The results of the calculations
are in fair agreement with the available experimental data. 相似文献
83.
Uma Basu Indira Addy Bidyut Kumar Datta 《International Journal of Theoretical Physics》1980,19(9):681-691
Recently Addy and Datta have obtained a linearized solution for isentropic motions of a perfect fluid by assigning Cauchy data on the hypersurfacex
4=0 and by imposing a restriction on the equation of state. In the present paper we pursue this study and discuss the problem of singularities from the standpoint of a local observer for which a singularity is defined as a state with an infinite proper rest mass density. It is shown that for a closed universe with any distribution of matter whatsoever there occurred a singularity in the past in the nonrotating parts of the universe and it must recur in the future. Furthermore, the collapse of a rotating fluid to a singularity seems inevitable when the relativistic equation of state is considered. 相似文献
84.
The high spin yrast states up toJ=20+ in184, 186Pt and190, 192, 194Pt are studied in a microscopic approach of variation with number-conserved projected states. The energy spectra, quadrupole
moments andB(E2) values are calculated by employing the Hamiltonian with quadrupole plus pairing interactions. The results of the calculations
are in fair agreement with the available experimental data. 相似文献
85.
Yi ZHU Kumar Shyam Chenlu HU Zixuan CHEN Yapeng ZHANG Fengyi ZHAO Xianglun WEI Limin DUAN Nu XU Hao QIU 《原子核物理评论》2021,38(4):416-422
低温高密核物质测量谱仪(CEE)是研究高重子数密度区核物质性质的重离子碰撞实验谱仪。使用了先进的 SAMPA 电子学读出芯片的时间投影室(TPC)是 CEE 最核心的探测器。在集团重建的过程中,同一排读出板的信号被首先重建成 2 维集团,然后根据 2 维集团的 ADC 加权平均位置重建击中点。当信号 ADC 随漂移时间变化呈峰-谷-峰结构时,一个集团可能被重建成两个或更多击中点,从而提高双径迹分辨能力。使用模拟信号的测试显示,该重建算法在$x/ y$ 方向可以达到0.100/0.043 cm的位置分辨能力和1.1/2.8 cm的双径迹分辨能力。 相似文献
86.
Jyoti Bhawan Singh Shakti Pratap Gupta Mohit Tripathi Sudhanshu Verma Alok Kumar Singh Devraj Yadav R. R. 《Acoustical Physics》2021,67(6):584-589
Acoustical Physics - We have estimated elastic, mechanical, thermal and ultrasonic properties, in high temperature regime, of cobalt nanowires (Co-NWs) having a hexagonal close-packed (HCP)... 相似文献
87.
Abdullateef O. Balogun Shuib Basri Luiz Fernando Capretz Saipunidzam Mahamad Abdullahi A. Imam Malek A. Almomani Victor E. Adeyemo Ganesh Kumar 《Entropy (Basel, Switzerland)》2021,23(10)
Feature selection is known to be an applicable solution to address the problem of high dimensionality in software defect prediction (SDP). However, choosing an appropriate filter feature selection (FFS) method that will generate and guarantee optimal features in SDP is an open research issue, known as the filter rank selection problem. As a solution, the combination of multiple filter methods can alleviate the filter rank selection problem. In this study, a novel adaptive rank aggregation-based ensemble multi-filter feature selection (AREMFFS) method is proposed to resolve high dimensionality and filter rank selection problems in SDP. Specifically, the proposed AREMFFS method is based on assessing and combining the strengths of individual FFS methods by aggregating multiple rank lists in the generation and subsequent selection of top-ranked features to be used in the SDP process. The efficacy of the proposed AREMFFS method is evaluated with decision tree (DT) and naïve Bayes (NB) models on defect datasets from different repositories with diverse defect granularities. Findings from the experimental results indicated the superiority of AREMFFS over other baseline FFS methods that were evaluated, existing rank aggregation based multi-filter FS methods, and variants of AREMFFS as developed in this study. That is, the proposed AREMFFS method not only had a superior effect on prediction performances of SDP models but also outperformed baseline FS methods and existing rank aggregation based multi-filter FS methods. Therefore, this study recommends the combination of multiple FFS methods to utilize the strength of respective FFS methods and take advantage of filter–filter relationships in selecting optimal features for SDP processes. 相似文献
88.
Birendra Kumar Deepti Tikariha Kallol K. Ghosh Nadia Barbero Pierluigi Quagliotto 《Journal of Physical Organic Chemistry》2013,26(8):626-631
Kinetic study has been performed to understand the reactivity of novel cationic gemini surfactants viz. alkanediyl‐α,ω‐bis(hydroxyethylmethylhexadecylammonium bromide) C16‐s‐C16 MEA, 2Br? (where s = 4, 6) in the cleavage of p‐nitrophenyl benzoate (PNPB). Novel cationic gemini C16‐s‐C16 MEA, 2Br? surfactants are efficient in promoting PNPB cleavage in presence of butane 2,3‐dione monoximate and N‐phenylbenzohydroxamate ions. Model calculation revealed that the higher catalytic effect of ethanol moiety of gemini surfactants (C16H33N+ C2H4OH CH3 (CH2)S N+ C2H4OH CH3C16H33, 2Br?, s = 4, 6) is due to their higher binding capacity toward substrate. This is in line with finding that binding constants for novel series of cationic gemini surfactants are higher than conventional cationic gemini (C16H33N+(CH3)2(CH2)SN+(CH3)2C16H33, 2Br?, s = 10, 12), cetyldimethylethanolammonium bromide and zwitterionic surfactants, i.e. CnH2n+1N+Me2 (CH2)3 SO3? (n = 10; SB3‐10). The fitting of kinetic data was analyzed by the pseudophase model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
89.
Sunil K. Singhal Veeresh Kumar K. Stalin Amit Choudhary Satish Teotia Gade B. Reddy Rakesh B. Mathur Surinder P. Singh Renu Pasricha 《Particle & Particle Systems Characterization》2013,30(5):445-452
Synergetic cooperation of individual components of the nanocomposites (NCs) is responsible for their novel properties that lead to various technological applications. A simple chemical process depicting the deposition of functionalized gold nanoparticles on the surface of boron nitride nanosheets (BNNSs) in solution is reported. The structure, chemical composition, and optical properties of nanosheets are systematically studied. The deposition of Au nanoparticles on BNNS (BNNSAu) results in plasmonic band modulation, thus altering the optoelectronic properties of BNNSs. The intense surface plasmon absorption band of BNNSAu is narrowed and red‐shifted relative to the absorption band of as synthesized monometallic BNNSs. The observations reflect the strong interfacial interaction between BNNS and Au nanoparticles. This approach constitutes a basis for a simple process leading to the preparation of functionalized BNNSs and their utilization as nanoscale templates for assembly and integration with other nanoscale materials for futuristic optoelectronic devices. 相似文献
90.
P. Kumar 《辐射效应与固体损伤》2013,168(4):258-264
The formation of nano-size hillocks and simple and complex craters was observed as a result of ion–surface collisions with a lithium niobate single crystal on proton implantation. The low-energy ion implantation process is considered as a controllable and versatile tool for surface and near-surface modifications down to an atomic scale as an alternative to the swift heavy ion irradiation effect. Lithium niobate samples implanted by proton ions with a low energy of 120 keV at various fluences (1015 and 1016 protons/cm2) were studied using atomic force microscopy (AFM). The images of surface modification appear as simple and complex crater formation in the case of incident ions at normal to the surface. Varying the angle of incidence to θ=30° with respect to the normal to the surface, hillocks and multi-hillocks were observed. The complex craters with central uplifted, cone-shaped hillocks with a height of up to 4.3 nm are surrounded by low-height (1 nm) rims. The hillock height varies from a few nanometers to 16 nm with the basal diameter from 200 to 340 nm depending on the ion implantation conditions. The complex crater and hillock formation on the lithium niobate sample surface at the collision spot with the impact of incident angle is discussed. 相似文献