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排序方式: 共有249条查询结果,搜索用时 15 毫秒
221.
Nouria A. Al-Awadi Mohamed H. Elnagdi Hanan A. Al-Awadhi Osman M. E. El-Dusouqui 《国际化学动力学杂志》1998,30(7):457-462
Six analogues and derivatives (1–6) of 3-phenylhydrazonopentane-2,4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s−1) and Ea (kJ mol−1) of the analogues (1–5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1) , 11.19 and 135.4 for 1-cyano-1-( -nitrophenylhydrazono)-propanone (2) , 10.68 and 144.9 for 1-cyano-1-( -methoxyphenylhydrazono)propanone (3) , 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4) , and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5) . The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s−1 and 143.3 kJ mol−1. The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 457–462, 1998 相似文献
222.
Mohammed I. El-Gamal Seyed-Omar Zaraei Moustafa M. Madkour Hanan S. Anbar 《Molecules (Basel, Switzerland)》2022,27(1)
Pyrazole has been recognized as a pharmacologically important privileged scaffold whose derivatives produce almost all types of pharmacological activities and have attracted much attention in the last decades. Of the various pyrazole derivatives reported as potential therapeutic agents, this article focuses on pyrazole-based kinase inhibitors. Pyrazole-possessing kinase inhibitors play a crucial role in various disease areas, especially in many cancer types such as lymphoma, breast cancer, melanoma, cervical cancer, and others in addition to inflammation and neurodegenerative disorders. In this article, we reviewed the structural and biological characteristics of the pyrazole derivatives recently reported as kinase inhibitors and classified them according to their target kinases in a chronological order. We reviewed the reports including pyrazole derivatives as kinase inhibitors published during the past decade (2011–2020). 相似文献
223.
GS Agarwal 《Pramana》1984,22(3-4):303-312
Nonlinear oscillator models are constructed to treat the bistability in situations involving elementary excitations in solids.
Such models are shown to be useful not only in describing single photon but also multiphoton bistability. The resulting bistability
both with and without cavity is considered. The two-photon excitonic bistability in CuCl is in detail. The effect of local
field corrections can also be incorporated, in a simple manner, in such models. 相似文献
224.
225.
The structures of the trinuclear gold(I), [Au(3)(2,6-Me(2)-form)(2)-(THT)Cl], the dinuclear [Au(2)(2,6-Me(2)-form)(2)], and the oxidative-addition product [Au(2)(2,6-Me(2)-form)(2)Cl(2)] formamidinate complexes are reported. The trinuclear complex is stable with gold-gold distances 3.01 and 3.55 A. The gold-gold distance in the dinuclear complex decreases upon oxidative-addition with halogens from 2.7 to 2.5 A, similar to observations made with the dithiolates and ylides. 相似文献
226.
Breuning E Hanan GS Romero-Salguero FJ Garcia AM Baxter PN Lehn JM Wegelius E Rissanen K Nierengarten H van Dorsselaer A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(15):3458-3466
The self-assembly of new multimetallic complexes of grid-type architecture is described. The binding of a set of tris-terdentate ligands, 1 a-1 d, based on terpyridine-like subunits, with different octahedrally coordinated metal ions leads to the formation of species whose structure depends strongly on the ligand, the metal ion, the counterion, the solvent, and the reaction conditions. Under suitable conditions, the [3 x 3] grid was obtained from the reaction of ligand 1 a with zinc tetrafluoroborate and from ligand 1 b with mercury triflate. The other ligands led to the formation of mainly one compound of composition [M(6)L(5)](12+), which has the structure of an incomplete [2 x 3] grid. The crystal structure of such a [2 x 3] grid, [Co(6)(1 d)(5)](12+), has been determined. In this complex, the three central pyrimidine-pyridine-pyrimidine non-coordinating sites adopt transoid NCbond;CN conformations. The much less stable cisoid conformations, the "pinching" of the coordination sites in the complex, the weaker donor strength of the central binding site, and the steric demand of the substituents are all factors contributing to the reluctance to produce the [3 x 3] structure. A subtle interplay between the nature of the metal, the steric demand of the ligand, the reaction conditions, and the type of counterion determine the product of self-assembly. The results obtained show that by tuning the parameters, complexes containing six or nine octahedrally coordinated metal ions in a well-defined grid-type arrangement are accessible. Both types of arrays, [2 x 3] and [3 x 3 ], are of interest as self-assembled inorganic architectures of well-defined structure and nuclearity that may be suitable prototypes for selective information storage media. 相似文献
227.
In this study, certain 3‐substituted styrylquinoxalin‐2(1H)‐ones ( 2a‐d ) and their 2‐chloro ( 3a‐d ) and 2‐piperazinyl derivatives ( 4a‐g ) were synthesized from 3‐methylquinoxalin‐2(1H)‐one ( 1 ). In addition, a series of 1‐alkyl‐3‐substituted styrylquinoxalin‐2(1H)‐ones ( 5a‐d ) was also prepared. Moreover, 3‐(N2‐arylidenehydrazinocarbonyl)quinoxalin‐2(1H)‐ones ( 8a‐c ) as well as their cyclized oxadiazolinyl derivatives ( 9a‐c ) were prepared from 3‐hydrazinocarbonylquinoxalin‐2(1H)‐one ( 7 ). Furthermore, 3‐(5‐substituted thio‐1,3,4‐oxadiazol‐2‐yl)quinoxalin‐2(1H)‐ones ( 11a‐c ) and ( 12a‐c ) were obtained from the intermediate compound ( 10 ) ‐ previously obtained via cyclization of ( 7 ) with CS2. Likewise, 3‐(5‐oxo‐4,5‐dihydro‐(1,3,4‐oxadiazol‐2‐yl)quinoxalin‐2(1H)‐one ( 13 ), 3‐[5‐(4‐nitrophenyl)‐1,3,4‐oxadiazol‐2‐yl]‐quinoxalin‐2(1H)‐one ( 14 ) and its 2‐chloro derivative ( 15 ) were prepared from 3‐hydrazinocarbonylquinoxalin‐2(1H)‐one ( 7 ). Some of these derivatives were evaluated for antimicrobial activity in vitro and some of the tested compounds showed antibacterial or antifungal activity. 相似文献
228.
Chen J Mohamed AA Abdou HE Bauer JA Fackler JP Bruce AE Bruce MR 《Chemical communications (Cambridge, England)》2005,(12):1575-1577
The structure of a novel metallamacrocyclic phosphine gold(I) thiolate cluster, [Au9(mu-dppm)4(mu-p-tc)6](PF6)3, where dppm = bis(diphenylphosphine)methane and p-tc = p-thiocresolate, is reported and shows AuAu attractions of approximately 3.0 A and gold(I) atoms linked to thiolate and phosphine ligands in distorted trigonal and nearly linear geometries. 相似文献
229.
Zaghal Mukarram H. Abu-Obeid Mona A. Atfah Mohammad A. El-Qisairi Arab K. Qaseer Hanan A. Ali Basem F. 《Transition Metal Chemistry》2001,26(4-5):517-522
3,6-Bis(2-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III) chloride and bromide (prepared in situ) to give cis-[Rh(n-dppn)2Cl2]PF6·xH2O (n = 5, 6, 7, 8) and cis-[Rh(n-dppn)2Br2]Br·xH2O (n = 5, 7) complexes, which have been characterized by elemental analyses, conductivity measurements, i.r., electronic and 1H- and 13C-n.m.r. spectra. 相似文献
230.
M. S. Abdelmonem A. A. Naqvi Hanan Al-Ghamdi Ghada Al-Misned 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):131-137
Performance of a 241Am-Be neutron source-based and 2.8 MeV neutrons-based moisture measurement setups have been compared using Monte Carlo simulation.
In the setup fast neutrons transmitted through the sample were detected by a fast neutron detector, which was placed behind
a massive long double truncated collimator. The setup geometry was optimized to detect maximum effect of 1–7 wt.% moisture
on the neutron intensity transmitted through the sample. The yield of neutrons transmitted through concrete, coal, wood and
soil samples containing 1–7 wt.% moisture was calculated for 2.8 MeV neutrons and neutrons from an 241Am-Be source. The slopes of the fast neutron intensities transmitted through the samples vs. their moisture contents are very
sensitive to the neutron energy and the sample composition. Higher slopes have been observed for the samples with larger bulk
density. The slopes of fast neutron yield show dependence on the incident neutron energy. Larger slopes have been observed
for neutrons with samller energy. Due to the overall large slopes of the transmitted intensity data of the samples for 2.8
MeV neutrons, it is expected to achieve better sensitivity in moisture measurements for a 2.8 MeV neutrons based moisture
setup. 相似文献