全文获取类型
收费全文 | 1993篇 |
免费 | 105篇 |
国内免费 | 28篇 |
专业分类
化学 | 1527篇 |
晶体学 | 11篇 |
力学 | 51篇 |
数学 | 161篇 |
物理学 | 376篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 93篇 |
2020年 | 58篇 |
2019年 | 67篇 |
2018年 | 67篇 |
2017年 | 46篇 |
2016年 | 91篇 |
2015年 | 82篇 |
2014年 | 101篇 |
2013年 | 197篇 |
2012年 | 111篇 |
2011年 | 119篇 |
2010年 | 93篇 |
2009年 | 94篇 |
2008年 | 99篇 |
2007年 | 98篇 |
2006年 | 78篇 |
2005年 | 79篇 |
2004年 | 76篇 |
2003年 | 47篇 |
2002年 | 48篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 28篇 |
1998年 | 17篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1985年 | 19篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 13篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1962年 | 5篇 |
1959年 | 9篇 |
排序方式: 共有2126条查询结果,搜索用时 15 毫秒
51.
I. V. Amirkhanov A. S. Khalil I. Sarkhadov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(4):711-718
Numerical simulation of the thermal processes occurring in indium phosphide under the action of a heavy gold ion with the energy E 0 = 200 MeV is carried out. The problem is solved taking into account phase transitions of the melting and evaporation types. Numerical studies are carried out on the basis of a modified thermal-peak model and the obtained results are analyzed. 相似文献
52.
I. Spǎnulescu I. Dima Mohamed Ismail Abd El-Ati N. Bǎlţǎţeanu Talal Khalass 《辐射效应与固体损伤》2013,168(3-4):299-303
The influence of 8 MeV electrons on the crystalline structure of HgTe and Hg1-xCdxTe thin films was studied. HgTe and Hg1-xCdxTe layers were obtained by thermal evaporation and condensation in vacuum on optically flat silica glass substrates heated at different temperatures. One finds that the results of irradiation of HgTe and Hg1-xCdxTe thin films with 8 MeV electrons depend on the preparation conditions of the samples, and therefore on the level of perfection of the crystalline structure and the quantity of nonstoichiometric atoms. 相似文献
53.
54.
55.
56.
We study the entanglement between a pair of two-level atoms simultaneously interacting via a singlemode thermal field. The Hamiltonian also describes a two-photon process. The entanglement between a nonlinear atom-field interacting system is also studied using atomic and field entropy changes. We use concurrence to detect the sudden death phenomenon. Furthermore, we discuss the relationship between entropy changes and concurrence entanglement. Our results show that the behavior of the entropy change is in agreement with the behavior of the concurrence when we measure the entanglement between the two-subsystem structure. 相似文献
57.
Residual determination and risk assessment of buprofezin in plum (Prunus domestica) grown in open‐field conditions following the application of three different formulations 下载免费PDF全文
Md. Humayun Kabir A.M. Abd El‐Aty Sung‐Woo Kim Han Sol Lee Md. Musfiqur Rahman Young‐Jun Lee Hyung Suk Chung Truong Lieu Jeong‐Heui Choi Ho‐Chul Shin Geon‐Jae Im Su Myeong Hong Jae‐Han Shim 《Biomedical chromatography : BMC》2016,30(11):1721-1727
This study was conducted to characterize the residual level and perform a risk assessment on buprofezin formulated as an emulsifiable concentrate, wettable powder, and suspension concentrate over various treatment schedules in plum (Prunus domestica). The samples were extracted with an AOAC quick, easy, cheap, effective, rugged, and safe, ‘QuEChERS’, method after major modifications. As intrinsic interferences were observed in blank plum samples following dispersive‐solid phase extraction (consisting of primary secondary amine and C18 sorbents), amino cartridges were used for solid‐phase extraction. Analysis was carried out using liquid chromatography with diode array detection and confirmed by liquid chromatography–tandem mass spectrometry. The method showed excellent linearity with determination coefficient (R2 = 1) and satisfactory recoveries (at two spiking levels, 0.5 and 2.5 mg/kg) between 90.98 and 94.74% with relative standard deviation (RSD) ≤8%. The limit of quantification (0.05 mg/kg) was considerably lower than the maximum residue limit (2 mg/kg) set by the Codex Alimentarius. Absolute residue levels for emulsifiable concentrates were highest, perhaps owing to the dilution rate and adjuvant. Notably, all formulation residues were lower than the maximum residue limit, and safety data proved that the fruits are safe for consumers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
58.
The adsorption of Cu(II) and Cr(III) ions by pure clay mineral, vermiculite, was examined in aqueous solution with respect
to the adsorbent dose, initial metal ion concentration, pH, and contact time. The studies showed that vermiculite can be used
as an adsorbent material for the moderate removal of Cr(III) and Cu(II) from aqueous solutions. Lagergren first-order, pseudo-second-order,
and intraparticle diffusion models were used to describe the kinetic data. The kinetics of adsorption indicates that the process
fitted well the intraparticle diffusion model. 相似文献
59.
Zal U��yun Wan Mahmood Che Abd Rahim Mohamed Zaharudin Ahmad Abdul Kadir Ishak 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(1):255-260
A total of eight sediment cores with 50 cm length were taken in the Sabah and Sarawak coastal waters using a gravity corer in 2004 to estimate sedimentation rates using four mathematical models of CIC, Shukla-CIC, CRS and ADE. The average of sedimentation rate ranged from 0.24 to 0.48 cm year?1, which is calculated based on the vertical profile of 210Pbex in sediment core. The finding also showed that the sedimentation rates derived from four models were generally shown in good agreement with similar or comparable value at some stations. However, based on statistical analysis of paired sample t-test indicated that CIC model was the most accurate, reliable and suitable technique to determine the sedimentation rate in the coastal area. 相似文献
60.
John W. CranMarie E. Krafft Kimberly A. SeibertThomas F.N. Haxell James A. WrightChitaru Hirosawa Khalil A. Abboud 《Tetrahedron》2011,67(51):9922-9943
From the initial development of a homologous Morita-Baylis-Hillman reaction utilizing epoxides as electrophiles, the method was expanded to enable the exclusively organocatalyzed intramolecular allylation of enones and to develop the intramolecular MBH-type alkylation of activated alkenes. We successfully utilized both enones and unsaturated thioesters as the activated alkene component. This work, carried out using stoichiometric amounts of the trialkylphosphine, gave an array of functionalized five- and six-membered carbocycles in high yields. With the cycloalkylation of enones and thioesters, conditions that allowed the use of substoichometric amounts of the phosphine catalyst were developed. As a result both five- and six-membered rings can be formed efficiently with little to no loss in yield upon comparison to yields obtained when stoichiometric amounts of trialkylphosphines were employed. We isolated, for the first time, an MBH-type intermediate exhibiting unprecedented trans geometry of the phosphonium salt and acyl group. 相似文献