全文获取类型
收费全文 | 3168篇 |
免费 | 121篇 |
国内免费 | 32篇 |
专业分类
化学 | 2235篇 |
晶体学 | 20篇 |
力学 | 108篇 |
综合类 | 1篇 |
数学 | 491篇 |
物理学 | 466篇 |
出版年
2024年 | 17篇 |
2023年 | 40篇 |
2022年 | 285篇 |
2021年 | 199篇 |
2020年 | 126篇 |
2019年 | 98篇 |
2018年 | 103篇 |
2017年 | 90篇 |
2016年 | 168篇 |
2015年 | 100篇 |
2014年 | 111篇 |
2013年 | 250篇 |
2012年 | 194篇 |
2011年 | 197篇 |
2010年 | 126篇 |
2009年 | 103篇 |
2008年 | 152篇 |
2007年 | 128篇 |
2006年 | 119篇 |
2005年 | 104篇 |
2004年 | 82篇 |
2003年 | 78篇 |
2002年 | 60篇 |
2001年 | 33篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 22篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 25篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有3321条查询结果,搜索用时 15 毫秒
981.
982.
983.
984.
The goal of this note is to provide a new embedding theorem and to derive from this embedding the CLR-type inequality for a potential belonging to a proper subspace of integrable functions. 相似文献
985.
986.
Mohammed M. Kummali Gustavo A. Schwartz Angel Alegría Richard Arinero Juan Colmenero 《Journal of Polymer Science.Polymer Physics》2011,49(18):1332-1338
The effect of thermal treatment on the phase separation process of the components of a polymer blend was investigated using electrostatic force microscopy (EFM). EFM technique is an advance on conventional atomic force microscopy, which enables us to measure locally the dielectric properties of the samples under investigation providing compositional information. In this work, we studied the phase separation process of the polymer blend thin films made of polystyrene and poly(vinyl acetate) (PS/PVAc) (75/25 weight fraction). The samples were subjected to different thermal treatments. It was found that at low annealing temperature, PVAc forms many small islands within PS matrix. As the annealing temperature increases, the number of PVAc islands decreases with an increase in the size of the islands. These islands take spherical‐like shape when annealed at a temperature well above the glass transition temperatures of both the component polymers. Despite these morphological/topographical changes, EFM images evidence that there is no interdiffusion which was further confirmed by quantitatively measuring the value of the dielectric permittivity across the interphase. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1332–1338, 2011 相似文献
987.
Seraj Faiza Kanwal Khan Khalid Mohammed Khan Ajmal Ali Muhammad Khalil Ruqaiya Ul-Haq Zaheer Hameed Shehryar Taha Muhammad Salar Uzma Perveen Shahnaz 《Molecular diversity》2021,25(1):143-157
Molecular Diversity - Novel ibuprofen derivatives 1–19 including ibuprofen hydrazide 1, and substituted thiourea derivatives 2–19 were synthesized and characterized by EI-MS, FAB-MS,... 相似文献
988.
Jibon Rayhan Habib Bulbul Abdullah Al-Mamun Nahid Abdullah-Al Faragallah Osama S. Baz Mohammed Eid Mahmoud M. A. Rashed Ahmed Nabih Zaki 《Optical Review》2021,28(5):564-572
Optical Review - We present the modeling of a porous core dispersion flatten photonic crystal fiber (PCF) for the fruitful transmission of THz signals. The model comprises only rectangular holes in... 相似文献
989.
Mohammed Ali Sheikh Keiko Tsuha Xiaochun Wang Kenzaburo Sawano Sia Taema Imo Tamotsu Oomori 《International journal of environmental analytical chemistry》2013,93(12):847-861
The spatial and temporal behaviours of the organotin compounds (OTCs) (butyl- and phenyltin) were investigated in the Manko and Okukubi protected estuarine ecosystems on Okinawa Island, Japan from February to October 2006. Butyltin compounds (BTCs) were frequently detected in all seasons, while phenyltin (PhTs) were found in winter and early spring. In Manko estuary, the total mean concentrations of BTCs and PhTs were 22.78?±?30.85, (mean?±?SD, n?=?53) and 0.08?±?0.27?ng(Sn)?L?1, respectively. In Okukubi estuary, BTCs and PhTs were 12.58?±?23.96 and 0.47?±?1.67 (n?=?55) ng(Sn)?L?1, respectively. The Manko sediments can be classified as lightly contaminated, while the Okukubi sediments were uncontaminated with tributyltin (TBT). The mean levels of TBT shown in Manko estuary exceeded the threshold level and represent an ecotoxicological risk to sensitive aquatic life. Generally, the present study reports the occurrence and continuous input of OTCs in the protected estuaries, even 16 years after legal restriction of TBT usage in coastal waters was implemented by the Japanese Environmental Authorities. 相似文献
990.
Dr. Mehdi Almant Amira Mastouri Laura Gallego‐Yerga Prof. José Manuel García Fernandez Prof. Carmen Ortiz Mellet Prof. José Kovensky Dr. Sandrine Morandat Dr. Karim El Kirat Dr. Sébastien G. Gouin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):729-738
We designed a set of multi‐galactosides with valencies ranging from one to seven and different spacer‐arm lengths. The compounds display a high structural homology for a strict assessment of multivalent phenomena. The multimers were first evaluated by an enzyme‐linked lectin assay (ELLA) toward the peanut agglutinin (PNA). The binding affinity was shown to be dependent on the spacer‐arm length, and cluster effects were observed for the galactosides bearing the shortest and the longest linkers. The latter compounds were shown to be much more potent PNA cross‐linkers in a “sandwich assay”. Dynamic light scattering (DLS) experiments also revealed the formation of soluble aggregates between heptavalent derivatives with medium or long linkers and the labeled PNA. ELLA experiments performed with valency‐controlled clusters and labeled lectins are therefore not always devoid from aggregative processes. The precise nature of the multivalent interaction observed by ELLA for the compounds bearing the shortest linkers, which are unable to form PNA aggregates, was further investigated by atomic force microscopy (AFM). The galactosides were grafted onto the tip of a cantilever and the PNA lectin onto a gold surface. Similar unbinding forces were registered when the valency of the ligands was increased, thus showing that the multimers cannot interact more strongly with PNA. Multiple binding events to the PNA were also never observed, thus confirming that a chelate binding mode does not operate with the multivalent galactosides, probably because the linkers are too short. Altogether, these results suggest that the cluster effect that operates in ELLA with the multimers is not related to additional PNA stabilizations and can be ascribed to local concentration effects that favor a dynamic turnover of the tethered galactosides in the PNA binding sites. 相似文献