全文获取类型
收费全文 | 9022篇 |
免费 | 1722篇 |
国内免费 | 452篇 |
专业分类
化学 | 6239篇 |
晶体学 | 183篇 |
力学 | 783篇 |
综合类 | 28篇 |
数学 | 624篇 |
物理学 | 3339篇 |
出版年
2024年 | 18篇 |
2023年 | 60篇 |
2022年 | 140篇 |
2021年 | 182篇 |
2020年 | 362篇 |
2019年 | 220篇 |
2018年 | 194篇 |
2017年 | 294篇 |
2016年 | 397篇 |
2015年 | 377篇 |
2014年 | 476篇 |
2013年 | 692篇 |
2012年 | 703篇 |
2011年 | 591篇 |
2010年 | 529篇 |
2009年 | 668篇 |
2008年 | 695篇 |
2007年 | 720篇 |
2006年 | 635篇 |
2005年 | 474篇 |
2004年 | 498篇 |
2003年 | 391篇 |
2002年 | 336篇 |
2001年 | 209篇 |
2000年 | 195篇 |
1999年 | 224篇 |
1998年 | 183篇 |
1997年 | 132篇 |
1996年 | 94篇 |
1995年 | 105篇 |
1994年 | 63篇 |
1993年 | 62篇 |
1992年 | 46篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 23篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
A. Konjhodzic A. Adamczyk F. Vagizov Z. Hasan E E. Alp W. Sturhahn Jiyong Zhao J J. Carroll 《Hyperfine Interactions》2006,170(1-3):83-89
With the decrease in size of devices, rapid characterization of nano-devices is an inevitable necessity. It is shown that Mössbauer spectroscopy using synchrotron radiation from the advanced photon source provides such a tool of investigation. Results are presented and compared for conventional Mössbauer and Nuclear Forward Scattering for 151Eu-doped magnesium sulfide as an example, especially at low concentrations. 相似文献
82.
Toshimi Shimizu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):5137-5152
Supramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self-assembly of unsymmetrical bolaamphiphilic monomers or glucopyranosylamide lipids, respectively. Time-resolved fluorescent measurement using 8-anilinonaphthalene-1-sulfonate (ANS) as a probe revealed that the water confined in a cardanyl-β-D -glucopyranoside lipid nanotube has relatively lower solvent polarity corresponding to that of propanol than bulk water. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube has been examined by filling the lyophilized LNTs with gold or silver nanoparticles, ferritin, or magnetic crystals. Filling the unsymmetrical bolaamphiphile nanotube possessing positively charged inner surfaces with negatively charged polymer beads or ferritin proved to be successful without depending on capillary action. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5137–5152, 2006 相似文献
83.
Kelly A. Burke Sona Sivakova Blayne M. McKenzie Patrick T. Mather Stuart J. Rowan 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):5049-5059
We report herein studies on the liquid crystalline behavior of a series of supramolecular materials that contain different ratios of two complementary symmetrically-substituted alkoxy-bis(phenylethynyl)benzene AA- and BB-type monomers. One monomer has thymine units placed at either end of the rigid mesogenic core, while the other has N6-(4-methoxybenzoyl)-adenine units placed on the ends. Differential scanning calorimetric and polarized optical microscopy studies have been carried out on these systems. These studies show that the material's behavior is strongly dependent on its thermal history. As a result, the materials can exhibit, on heating, either a liquid crystalline phase, a crystalline phase, or the coexistence of crystalline and liquid crystalline regions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5049–5059, 2006 相似文献
84.
I.IntroductionDuetospatia1andtemporalvariabilityoftheocean-acousticenvironment,especially,theeffectsofboundaryaswel1asmediumonpropagationofacousticwavesinshal1owwater,theacousticpropagationisextrcmelycomp1icatcd.Multipathtransmissionisthebasiccharacteris-hcsofunderwatersoundchannels.Undctcrminedmultipathstructurescangreatlylimittheperformanceofunderwateracousticdetcction.However,ifthemultipathcharacteristicsofacousticpropagationinunderwatcrsoundchanne1sareknown,spaee-timeresolutionandpro-cess… 相似文献
85.
We calculate the moments t
q
, whereq is not necessarily an integer, of the first passage time to trapping for a simple diffusion problem in one dimension. If a characteristic length of the system isL and t
q
~L
(q) asL, then we show that there is a phase transition atq=q
c
such that whenq<q
c
,(g)=0, and forq>q
c
, (q) is a linear function ofq. These analytical results can be used to explain results for large moments for diffusion on a hierarchic structure. We also show how to calculate noninteger moments in terms of characteristic functions. 相似文献
86.
介绍了核磁共振(NMR)波谱,尤其是核磁共振二维谱(2D NMR)在最近几年内的进展。内容包括怎样用NMR测定高聚物的序列分布、共聚物结构、聚合物的混溶性、聚合物液晶的取向度、分子量、短链度和长链支化度、凝聚态高聚物的多相结构等。 相似文献
87.
88.
Vasyl' I. Zaremba Dariusz Kaczorowski Galyna P. Nychyporuk Ute Ch. Rodewald Birgit Heying Rainer Pttgen 《无机化学与普通化学杂志》2006,632(6):975-980
New indides Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La3GeIn4 type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F2 values, 17 variables for Ce3Ge0.66In4.34 and I4/mmm, Sm11Ge4In6 type (ordered version of the Ho11Ge10 type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F2 values, 41 variables for Ce11Ge4.74In5.26. The Ce3Ge0.66In4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce11Ge4.74In5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce3+ ions. The compound Ce3GeIn4 remains paramagnetic down to 1.72 K, whereas Ce11Ge4In6 orders ferromagnetically at TC = 7.5 K. 相似文献
89.
90.
D. N. Dybtsev M. P. Yutkin E. V. Peresypkina A. V. Virovets Y. Hasegawa H. Nishihara V. P. Fedin 《Russian Chemical Bulletin》2007,56(9):1782-1786
The reaction of Co(NO3)2·6H2O with 1,3,5-benzenetricarboxylic acid (H3btc, trimesic acid) in DMF at 100 °C afforded the coordination polymer [Co3(dmf)6(btc)(Hbtc)(H2btc)]··9H2O (1) (dmf is N,N′-dimethylformamide, DMF). According to the X-ray diffraction study, the metal-organic coordination polymer is composed of
planar honeycomb (6,3) networks, in which the organic benzenetricarboxylate anions and the inorganic Co2+ cations play a role of three-connected nodes. Disordered water molecules are intercalated between the layers. A study of
the magnetic properties showed the presence of a weak antiferromagnetic coupling between the Co2+ ions (S = 3/2).
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1719–1723, September, 2007. 相似文献