全文获取类型
收费全文 | 2057篇 |
免费 | 80篇 |
国内免费 | 3篇 |
专业分类
化学 | 1100篇 |
晶体学 | 34篇 |
力学 | 118篇 |
数学 | 504篇 |
物理学 | 384篇 |
出版年
2023年 | 20篇 |
2022年 | 25篇 |
2021年 | 24篇 |
2020年 | 58篇 |
2019年 | 69篇 |
2018年 | 75篇 |
2017年 | 64篇 |
2016年 | 123篇 |
2015年 | 79篇 |
2014年 | 97篇 |
2013年 | 357篇 |
2012年 | 96篇 |
2011年 | 103篇 |
2010年 | 93篇 |
2009年 | 82篇 |
2008年 | 69篇 |
2007年 | 68篇 |
2006年 | 76篇 |
2005年 | 38篇 |
2004年 | 46篇 |
2003年 | 24篇 |
2002年 | 32篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 26篇 |
1998年 | 23篇 |
1997年 | 30篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 10篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1927年 | 5篇 |
排序方式: 共有2140条查询结果,搜索用时 15 毫秒
51.
Kandaz Mehmet Çoruhlu Seher Zerrin Yilmaz İsmail Özkaya Ali Rıza 《Transition Metal Chemistry》2002,27(8):877-883
A new vic-dioxime, 13,14-bis-(hydroxyimino)-9,12,15,18-diazadithiaoctacosane, has been synthesized from 2-octylsulfanylaminobenzene and (E,E)-dichloroglyoxime. Mononuclear transition metal complexes of NiII, CuII, CoII and FeII have been prepared and were found to have a metal–ligand ratio of 1:2. The synthesis of di- and trinuclear complexes was achieved with UIVO2 and CuII depending on the stoichiometry of the reactants. The complexes were characterized by elemental analysis, 1H-n.m.r., u.v.–vis, i.r., f.a.b.-m.s. and by cyclic voltammetry. 相似文献
52.
H. C. Öttinger 《Colloid and polymer science》1987,265(2):101-105
The idea of consistently averaging the hydrodynamic interaction and its various consequences for Hookean dumbbells are reviewed. For long chains this idea can be used to generalize the Rouse-Zimm model for polymer solutions. Unlike the usual Rouse-Zimm model, the new model for steady shear flow predicts a nonzero second normal stress coefficient and shear rate dependent material functions. In the limit of long chains, the viscosity and the normal stress coefficients are universal functions of the reduced shear rate.This paper was presented at the Frühjahrstagung des Fachausschusses Polymerphysik der Deutschen Physikalischen Gesellschaft at Kaiserslautern (West Germany), March 12–14, 1986. 相似文献
53.
An approximate electron propagator method for predictive calculations of molecular electron affinities is proposed. The self-energy accounts for relaxation effects to all orders Additional correlation effects are treated using a diagonal approximation with shifted denominators. Applications to CN, NH2, and PH2 are reported. 相似文献
54.
(1R,2R)-1,2-bis-(5-amino-1,3,4-thiadiazole-2-yl)ethane-1,2-diol (L) has been prepared by the reaction of thiosemicarbazide with (2R,3R)-(+)-tartaric
acid (I) and phosphorous oxychloride, and its complexes with Co(II), Ni(II) and Cu(II) have been obtained. The structures
of the ligand and its complexes have been established by i. r., 1H- and 13C-n.m.r. spectra, u.v.–vis–nir spectroscopy, elemental analyses, T.g.-D.t.a. and magnetic susceptibility measurements. 相似文献
55.
Osman Dayan Muharrem Diner Bekir etinkaya Namk
zdemir Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):m346-m348
The title complex, di‐μ‐chloro‐bis[chloro(η6‐p‐cymene)ruthenium(II)]–9H‐carbazole (1/2), [Ru2Cl4(C10H14)2]·2C12H9N, is composed of one [RuCl2(η6‐p‐cymene)]2 and two 9H‐carbazole molecules. There are one‐half of a dinuclear complex and one 9H‐carbazole molecule per asymmetric unit. In the dinuclear complex, each of the two crystallographically equivalent Ru atoms is in a pseudo‐tetrahedral environment, coordinated by a terminal Cl atom, two bridging Cl atoms and the aromatic hydrocarbon, which is linked in a η6 manner; the Ru⋯Ru separation is 3.688 (3) Å. The title complex has a crystallographic centre of symmetry located at the mid‐point of the Ru⋯Ru line. Intermolecular N—H⋯Cl and π–π stacking interactions are observed. These interactions form a four‐pointed star‐shaped ring and one‐dimensional linear chains of edge‐fused rings running parallel to the [100] direction, which stabilize the crystal packing. 相似文献
56.
Hasan Kırmızıbekmez Yiğit İnan Rengin Reis Hande Sipahi Ahmet C. Gören Erdem Yeşilada 《Natural product research》2019,33(17):2541-2544
Phytochemical investigations on the EtOH extract of Clematis viticella led to the isolation of six flavonoid glycosides, isoorientin (1), isoorientin 3′-O-methyl ether (2), quercetin 7-O-α-L-rhamnopyranoside (3), quercetin 3,7-di-O-α-L-rhamnopyranoside (4), manghaslin (5) and chrysoeriol 7-O-β-D-glucopyranoside (6), one phenylethanol derivative, hydroxytyrosol (7), along with three phenolic acids, caffeic acid (8), (E)-p-coumaric acid (9) and p-hydroxybenzoic acid (10). The structures of the isolates were elucidated on the basis of NMR and HR-MS data. All compounds were isolated from C. viticella for the first time. Compounds 7 and 8 showed significant anti-inflammatory activity at 100 μM by reducing the release of NO in LPS-stimulated macrophages comparable to positive control indomethacin. Compounds 3 and 7 exhibited anti-inflammatory activity through lowering the levels of TNF-α while 1, 3 and 5 decreased the levels of neopterin better than the positive controls. 相似文献
57.
A. Ugur M. M. Saç G. Yener Ü. Altinbaş Y. Kurucu M. Bolca B. Özden 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):265-270
Vertical distributions of 137Cs and 210Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From 137Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t.ha-1.y-1 and from 79.9 to 3.5 t.ha-1.y-1, respectively. The 210Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region. 相似文献
58.
Rotation matrices were expressed in terms of Gaunt coefficients and complex spherical harmonics. The rotation matrices were calculated using two different ways. In the first, Gaunt coefficients and normalized complex spherical harmonics were directly calculated using binomial coefficients; in the second, Gaunt coefficients and complex spherical harmonics were recursively calculated. The methods were compared with respect to accuracy and computation time (CPU) for low and very high quantum numbers. 相似文献
59.
Hakki İsmail Erdoğan 《Journal of Geometry》1991,40(1-2):47-59
In this paper, the problem of determining the pencils of circles which form a hexagonal n-web in E2, is completely solved. It is well-known that n pencils of circles orthogonal to a fixed circle form a hexagonal n-web. Therefore, the main problem is the determination of all circle pencils which form a hexagonal n-web and which do not cut a fixed circle orthogonally. In this connection the following results have been obtained: The number of hexagonal 4-webs is six, whereas the number of hexagonal 5-webs is two.Finally, after having proved that the number of hexagonal 6-webs is one, it is shown that, for n7, there exist no circle pencils forming a hexagonal n-web without being orthogonal to a fixed circle. 相似文献
60.