全文获取类型
收费全文 | 569篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 301篇 |
晶体学 | 2篇 |
力学 | 12篇 |
数学 | 43篇 |
物理学 | 222篇 |
出版年
2022年 | 4篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2013年 | 28篇 |
2012年 | 27篇 |
2011年 | 30篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 18篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 18篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1969年 | 6篇 |
1968年 | 5篇 |
排序方式: 共有580条查询结果,搜索用时 15 毫秒
561.
562.
Three different analytical techniques were compared in a study of the role of trace elements in multiple sclerosis. Data for eight elements (Cd, Co, Cr, Cu, Mg, Mn, Pb, Zn) from neutron activation, flame atomic absorption and electrothermal atomic absorption methods were compared and evaluated statistically. No difference (probability less than 0.001) was observed in the elemental values obtained. Comparison of data between suitably different analytical methods gives increased confidence in the results obtained and is of particular value when standard reference materials are not available. 相似文献
563.
564.
P. Kleinheinz M.R. Maier R.M. Diamond F.S. Stephens R.K. Sheline 《Physics letters. [Part B]》1975,53(5):442-444
Half-life measurements show that the lowest high-j state in 141Ce, 143Nd, 145Sm, and 147Gd, earlier assigned as an h9/2 fragment, is an i13/2 single-neutron excitation which previously was thought to lie above 3 MeV in the N = 83 nuclei. 相似文献
565.
566.
Song XF Sosebee M Sotnikova N Souza M Stanton NR Steinbruck G Stephens RW Stevenson ML Stichelbaut F Stoker D Stolin V Stoyanova DA Strauss M Streets K Strovink M Stutte L Sznajder A Tamburello P Tarazi J Tartaglia M Thomas TL Thompson J Toback D Trippe TG Turcot AS Tuts PM 《Physical review letters》2000,84(2):222-227
We report a measurement of the W boson mass based on an integrated luminosity of 82 pb(-1) from p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded in 1994-1995 by the D0 detector at the Fermilab Tevatron. We identify W bosons by their decays to enu, where the electron is detected in the forward calorimeters. We extract the mass by fitting the transverse mass and the electron and neutrino transverse momentum spectra of 11 089 W boson candidates. We measure M(W) = 80.691+/-0.227 GeV. By combining this measurement with our previously published central calorimeter results from data taken in 1992-1993 and 1994-1995, we obtain M(W) = 80.482+/-0.091 GeV. 相似文献
567.
Smith RP Snihur R Snow GR Snow J Snyder S Solomon J Song XF Sosebee M Sotnikova N Souza M Stanton NR Steinbruck G Stephens RW Stevenson ML Stichelbaut F Stoker D Stolin V Stoyanova DA Strauss M Streets K Strovink M Sznajder A Tamburello P Tarazi J Tartaglia M Thomas TL 《Physical review letters》2000,84(24):5478-5483
This Letter describes a measurement of the muon cross section originating from b-quark decay in the forward rapidity range 2.4<| y(&mgr;)|<3.2 in p&pmacr; collisions at sqrt[s] = 1.8 TeV. The data used in this analysis were collected by the D0 experiment at the Fermilab Tevatron. We find that next-to-leading-order QCD calculations underestimate b-quark production by a factor of 4 in the forward rapidity region. 相似文献
568.
A new highly cytotoxic iridoid has very recently been isolated from Prismatomeris tetrandra and shown to have the structure 3, similar to that of the iridoid oruwacin, 2. We report the determination of the absolute configuration (AC) of the new iridoid, prismatomerin, using vibrational circular dichroism (VCD) spectroscopy. The VCD spectrum of the acetate derivative of 3, 4, is analyzed using the Stephens theory of VCD and density functional theory (DFT). The AC of the naturally occurring 3 is shown to be 1R,5S,8S,9S,10S, identical to that of the naturally occurring iridoid plumericin, 1, also determined using VCD spectroscopy. The [alpha]D values of the natural products 3 and 1 are negative and positive, respectively. Since the ACs of 3 and 1 are identical, it follows that the AC of 3 cannot be correctly determined by empirical comparison of the signs of the [alpha]D values of 3 and 1. 相似文献
569.
Stephens PJ Devlin FJ Gasparrini F Ciogli A Spinelli D Cosimelli B 《The Journal of organic chemistry》2007,72(13):4707-4715
The chiral oxadiazol-3-one 2 has recently been shown to exhibit myocardial calcium entry channel blocking activity, substantially higher than that of diltiazem. To determine the enantioselectivity of this activity, the enantiomers of 2 have been resolved using chiral chromatography. The absolute configuration (AC) of 2 has been determined by comparison of density functional theory (DFT) calculations of its vibrational circular dichroism (VCD) spectrum, electronic circular dichroism (ECD) spectrum, and optical rotation (OR) to experimental VCD, ECD, and OR data. All three chiroptical properties yield identical ACs; the AC of 2 is unambiguously determined to be S(+)/R(-). 相似文献
570.
Nicholas F. Stephens 《Journal of solid state chemistry》2007,180(1):260-264
An organically templated yttrium fluoride has been prepared hydrothermally and characterised by X-ray powder diffraction. The crystal structure of [C3N2H12]0.5[Y3F10] may be regarded as a ‘Super-Diamond’ framework, space group Fd, a=15.4817(1) Å, where each carbon atom site of the diamond structure is replaced by a polyhedral [Y6F8F24/2]2− unit. The basic framework type is isostructural with the known phase (H3O)[Yb3F10]·H2O. The novelty in the present case lies in the use of the organic structure-directing agent 1,3-diaminopropane. 相似文献