全文获取类型
收费全文 | 77174篇 |
免费 | 5857篇 |
国内免费 | 6646篇 |
专业分类
化学 | 69487篇 |
晶体学 | 857篇 |
力学 | 2886篇 |
综合类 | 383篇 |
数学 | 3703篇 |
物理学 | 12361篇 |
出版年
2024年 | 132篇 |
2023年 | 831篇 |
2022年 | 1918篇 |
2021年 | 1659篇 |
2020年 | 2232篇 |
2019年 | 2117篇 |
2018年 | 2038篇 |
2017年 | 2635篇 |
2016年 | 3127篇 |
2015年 | 2723篇 |
2014年 | 2956篇 |
2013年 | 5623篇 |
2012年 | 4542篇 |
2011年 | 4470篇 |
2010年 | 3762篇 |
2009年 | 4716篇 |
2008年 | 4063篇 |
2007年 | 4452篇 |
2006年 | 3916篇 |
2005年 | 3639篇 |
2004年 | 3392篇 |
2003年 | 2778篇 |
2002年 | 2779篇 |
2001年 | 1917篇 |
2000年 | 1774篇 |
1999年 | 1595篇 |
1998年 | 1395篇 |
1997年 | 1289篇 |
1996年 | 1322篇 |
1995年 | 1295篇 |
1994年 | 1129篇 |
1993年 | 877篇 |
1992年 | 785篇 |
1991年 | 718篇 |
1990年 | 553篇 |
1989年 | 520篇 |
1988年 | 564篇 |
1987年 | 519篇 |
1986年 | 396篇 |
1985年 | 382篇 |
1984年 | 384篇 |
1983年 | 184篇 |
1982年 | 342篇 |
1981年 | 293篇 |
1980年 | 271篇 |
1979年 | 261篇 |
1978年 | 123篇 |
1977年 | 74篇 |
1976年 | 72篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
231.
X.F. Hu 《Applied Surface Science》2006,252(13):4625-4627
The synthetic antiferromagnets (SAF) have been used in spin-valve sensor in data storage industry [1]. We report a new hard/Ru/soft sandwich structure (SHBL) fabricated by pulsed lased deposition to replace current single layer structure for information recording application. SHBL consists of two magnetic layers separated by thin nonmagnetic layers, typically with Ru layers of 0.7-1.2 nm, through which antiferromagnetic coupling is induced. Varying the relative thickness of the magnetic layers, the spacer layers, and the type of magnetic materials can alter magnetic properties of CoCrPt/Ru/CoFe superlattice. The coercivity Hc and grain size of magnetic layer is also dependent on the laser fluence. High laser fluence results in both small grain size and high Hc. The observed phenomena are related to high quenching and deposition rates during PLD at high fluence, resulting in more pronounced phase segregation. 相似文献
232.
This paper is based on the M. Sc. thesis written by the third author under the supervision of the first two authors. It was submitted to the University of Baghdad in 1986. 相似文献
233.
相型同步启动时间的M/M/c排队系统 总被引:4,自引:0,他引:4
本文研究带有同步启动时间的M/M/c系统,其中启动时间是相型变量,给出了稳态和等待时间分布等结果。 相似文献
234.
Yamada Kaoru Matsutani Shigeaki Uchiyama Akira Takahashi Toshio 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(1):49-54
Analyses of crown ether complexes of alkali metal ions and characterization of the complexes formed inm-nitrobenzyl alcohol have been carried out by fast atom bombardment (FAB) mass spectrometry. By using m-nitrobenzyl alcohol as a matrix for measurements, the stoichiometry of the complexes was assessed on the basis of the observed FAB peaks. In addition, the formation of crown ether-alkali metal complexes at a 2 : 1 molar ratio was enhanced by increasing the ionic radius of the metal ion in agreement with previous observations. On these grounds, FAB mass spectrometry may provide a rapid means for investigation of the complexation behavior of crown ethers and the stoichiometry of the complexes. 相似文献
235.
M. Froese C. Champagne J. R. Crespo López-Urrutia S. Epp G. Gwinner A. Lapierre J. Pfister G. Sikler J. Ullrich J. Dilling 《Hyperfine Interactions》2006,173(1-3):85-92
The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and,
hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap
(EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding
the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased
inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities
are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies
of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration
within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and
injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN
EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear
Physics in Heidelberg, Germany. 相似文献
236.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(13):3419-3419
237.
238.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
239.
V. E. Kirichenko E. P. Promyshlennikova K. I. Pashkevich 《Russian Chemical Bulletin》1994,43(5):812-815
The dependence of the variations in the differential molar free energy of sorption of polyfluorocarboxamides RFC(O)NR2 (RF = CF3(CF2)
i
,i=0 to 5, R=H or Me) on capillary columns on the molecular structure of the amides, the temperature of analysis, and the nature of the stationary phases (OV-101, XE-60, and PEG-40M) were investigated by GLC. The peculiarities of the variation of the sorption characteristics of amides in XE-60 and PEG-40M polar phases, which cause the inversion of the order of retention of the members of pseudohomologous series, were found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 868–871, May, 1994.We are grateful to R. V. Golovnya and D. N. Grigor'eva (Institute of Food Substances of the RAS, Moscow) for their participation in the discussion of the results obtained. 相似文献
240.
Flaked capillary columns with an OV-101/CE-Na{in3}PO{in4} hydrophobic-hydrophilic sorbent have been suggested. This sorbent provides for the analysis of polar and nonpolar substances, including amines and aminoalcohols, in aqueous and organic solvents. The efficiency of new columns was demonstrated for the analysis of 25 organic substances of various classes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2169–2173, December, 1994.The work was financially supported by the Russian Foundation for Basic Research, Project No. 93-03-4969. 相似文献