全文获取类型
收费全文 | 102450篇 |
免费 | 1168篇 |
国内免费 | 451篇 |
专业分类
化学 | 31824篇 |
晶体学 | 903篇 |
力学 | 7046篇 |
数学 | 32965篇 |
物理学 | 17808篇 |
无线电 | 13523篇 |
出版年
2023年 | 185篇 |
2022年 | 228篇 |
2021年 | 404篇 |
2020年 | 331篇 |
2019年 | 380篇 |
2018年 | 12117篇 |
2017年 | 11710篇 |
2016年 | 7489篇 |
2015年 | 1351篇 |
2014年 | 971篇 |
2013年 | 1324篇 |
2012年 | 5216篇 |
2011年 | 12733篇 |
2010年 | 7542篇 |
2009年 | 7519篇 |
2008年 | 8140篇 |
2007年 | 10526篇 |
2006年 | 1065篇 |
2005年 | 2347篇 |
2004年 | 2414篇 |
2003年 | 2703篇 |
2002年 | 1608篇 |
2001年 | 636篇 |
2000年 | 654篇 |
1999年 | 428篇 |
1998年 | 379篇 |
1997年 | 331篇 |
1996年 | 372篇 |
1995年 | 256篇 |
1994年 | 200篇 |
1993年 | 177篇 |
1992年 | 144篇 |
1991年 | 140篇 |
1990年 | 123篇 |
1989年 | 116篇 |
1988年 | 114篇 |
1987年 | 84篇 |
1986年 | 74篇 |
1985年 | 83篇 |
1984年 | 71篇 |
1983年 | 66篇 |
1982年 | 66篇 |
1981年 | 59篇 |
1980年 | 62篇 |
1979年 | 62篇 |
1978年 | 53篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The coordination compound [Co(C10H7COO)2(H2O)3]2n
· 4nH2O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized
by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers
are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions.
The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can
be assigned to the intraligand electronic transfer. 相似文献
92.
Gil MC Lee MH Seo JI Choi YL Kim MK Jung KC Park SH Kim TJ 《Experimental & molecular medicine》2002,34(6):411-418
CD99 plays a critical role in the diapedesis of monocytes, T cell differentiation, and the transport of MHC molecules. Engagement of CD99 by agonistic monoclonal antibodies has been reported to trigger multifactorial events including T cell activation as well as cell-cell adhesion during hematopoietic cell differentiation. In this study, to identify the functional domains participating in the cellular events, we mapped the epitopes of CD99, which are recognized by two agonistic CD99 monoclonal antibodies, DN16 and YG32. Using recombinant fusion proteins of GST with whole or parts of CD99, we found that both antibodies interact with CD99 molecules independently of sugar moieties. DN16 mAb detected a linear epitope located in the amino terminal region of CD99 while YG32 mAb bound another linear epitope in the center of the extracellular domain. To confirm that the identified epitopes of CD99 are actually recognized by the two mAbs, we showed the presence of physical interaction between the mAbs and the fusion proteins or synthetic peptides containing the corresponding epitopes using surface plasmon resonance analyses. The dissociation constants of DN16 and YG32 mAbs for the antigen were calculated as 1.27 x 10(-7) and 7.08 x 10(-9) M, respectively. These studies will help understand the functional domains and the subsequent signaling mechanism of CD99. 相似文献
93.
S. V. Volkov S. V. Kutyakov A. N. Levov E. I. Polyakova Le Tuan An S. A. Soldatova P. B. Terentiev A. T. Soldatenkov 《Chemistry of Heterocyclic Compounds》2007,43(10):1260-1268
It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of
arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation
of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles
and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has
been studied.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007. 相似文献
94.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
95.
Computer-based atomistic simulation methods are applied to address quantitatively the defect energetics and crystal chemistry of lanthanum magnesium hexaaluminate (LMA). The tetrahedral site preference of Mg in the magnetoplumbite structure is determined by calculating lattice energies for different Mg ion distributions. It is revealed that the intrinsic and extrinsic disorders are much influenced by the distribution of Mg in the structure. Our calculations show that oxygen Frenkel disorder is the dominant defect mode to be expected, even though Schottky disorder may also exist. Several feasible defect processes in nonstoichiometric LMA are determined from the enthalpies of the quasi-chemical reactions for the processes with simple point defect energies. We have also modeled some defect complexes in the mirror plane regions. It is found that the Mg ions positioned in the tetrahedral sites suppress the formation of cation vacancies in the mirror plane, through hindering the relaxation of the 12kAl ions by which the vacancies are stabilized. In Mg-deficient nonstoichiometric LMA, however, it is expected that the defect complex [VLa+VAl+2(VAl+Ali)] will be formed in the interspinel layer. Our calculations also indicate that the OLadefect is improbable in LMA not only as a simple point defect but also as a member of a defect complex. 相似文献
96.
97.
98.
99.
100.
Robert W. Ashford Peter Connard Robert Daniel 《The Journal of the Operational Research Society》1992,43(5):519-531
The time-consuming process of solving large-scale Mixed Integer Programming problems using the branch-and-bound technique can be speeded up by introducing a degree of parallelism into the basic algorithm. This paper describes the development and implementation of a parallel branch-and-bound algorithm created by adapting a commercial MIP solver. Inherent in the design of this software are certain ad hoc methods, the use of which are necessary in the effective solution of real problems. The extent to which these ad hoc methods can successfully be transferred to a parallel environment, in this case an array of at most nine transputers, is discussed. Computational results on a variety of real integer programming problems are reported. 相似文献