全文获取类型
收费全文 | 347篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
化学 | 225篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 7篇 |
物理学 | 110篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有355条查询结果,搜索用时 15 毫秒
11.
Reversed-phase HPLC separation of complex mixtures of trace metals as dibenzyldithiocarbamate chelates 总被引:1,自引:0,他引:1
The dibenzyldithiocarbamate chelates of Cd(II), Pb(II), Bi(III), Hg(II), Ni(II), Cu(II), As(III), Fe(III), Co(III) and In(III) are separated by reversed-phase HPLC in isocratic conditions. The procedure is simple, rapid, and gives satisfactory separations with high efficiency and sensitivity at mobile phase compositions very rich in organic modifier (85-88% CH(3)CN). The detection limits range from 1.4 to 14 mug/1. The elution order is correlated with the ability of the central metal atom to affect the electronic distribution of the ligand, which has readily polarizable donor atoms. Infrared spectroscopy data corroborate this assumption. 相似文献
12.
US Environmental Protection Agency Method 300.0 specifies the use of an IonPac AS4A anion-exchange column with a carbonate-hydrogencarbonate eluent and suppressed conductivity detection for the determination of inorganic anions in environmental waters by ion chromatography. Hydroxide eluents have not typically been used for the routine analysis of common inorganic anions due to the lack of an appropriate hydroxide selective column and the difficulty in preparing contaminant free hydroxide eluents. The use of ion chromatography with a hydroxide-selective IonPac AS17 column, automated eluent generation and potassium hydroxide gradient represents a new approach to the routine determination of inorganic anions in environmental waters. This new approach, which is a modification of Method 300.0, allows equivalent method performance with improved linearity, precision, and method detection limits. The AS17 column provides superior retention of fluoride from the column void volume and improved resolution from small organic acids, such as formate and acetate, compared to the AS4A column. Quantitative recoveries were obtained for all the common inorganic anions spiked into typical environmental waters using this new approach, and the Performance Based Measurement System Tier 1 method validation quality control acceptance criteria are well within the acceptable ranges defined by Method 300.0. In addition, the EG40 eluent generator eliminates the need to manually prepare eluents, increasing the level of automation and ease-of-use of the ion chromatography system. 相似文献
13.
R. Albrecht T. C. Awes P. Beckmann F. Berger D. Bock R. Bock G. Claesson G. Clewing L. Dragon A. Eklund R. L. Ferguson A. Franz S. Garpman R. Glasow H. Å. Gustafsson H. H. Gutbrod G. Hölker J. Idh P. Jacobs K. H. Kampert B. W. Kolb P. Kristiansson H. Löhner I. Lund F. E. Obenshain A. Oskarsson I. Otterlund T. Peitzmann F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo S. Saini H. R. Schmidt S. P. Sørensen K. Steffens D. Stüken E. Stenlund M. Tincknell G. R. Young 《Zeitschrift fur Physik C Particles and Fields》1991,51(1):1-10
The production of direct photons has been investigated in reactions ofp and16O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and 0 spectra have been measured in the pseudorapidity range 1.52.1 for the transverse momentum region 0.4 GeV/cp
T
2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of 0 and mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed. 相似文献
14.
15.
16.
17.
C. Baiocchi D. Giacosa G. Saini P. Cavalli N. Omenetto R. Passarella 《International journal of environmental analytical chemistry》2013,93(1-4):211-218
Abstract Measurements of thallium levels in Antarctic snow samples collected in an area surrounding the Italian Station at Terra Nova Bay in different campaigns have been performed without preconcentration by means of Laser Induced Atomic Fluorescence Spectroscopy (LIAF) as well as by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR ICP-MS). The data obtained by both methods compare favourably and are of the order of tenths of pg/g. The data is discussed taking into account the effect of the marine aerosol and the crustal contribution to the thallium content in samples. 相似文献
18.
Kapil Mohan Saini Rakesh K. Saunthwal Sushmita Akhilesh K. Verma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1017-1021
Transition-metal-free regioselective synthesis of functionalized amino-indenones by the reaction of ortho-alkynylaldehydes with a broad range of primary amines by intramolecular cyclization has been described. The designed reaction proceeds through KOH-mediated Prins-type cyclization and DMSO-promoted oxidation of the cyclopent-2-en-1-one system. The proposed mechanism and role of solvent were well supported by control experiments. For the first time, we have disclosed the reverse reactivity of (2-alkynyl)-arylaldimines in a super basic system. 相似文献
19.
Narayanan Balaji Bhavesh Babulal Gabani Umesh Todmal Suresh P. Sulochana Neeraj Kumar Saini Rajesh Chandran Ramesh Mullangi 《Biomedical chromatography : BMC》2019,33(3)
We developed and validated a simple, sensitive, selective and reliable LC–ESI‐MS/MS method for direct quantitation of dropropizine enantiomers namely levodropropizine (LDP) and dextrodropropizine (DDP) in rat plasma without the need for derivatization as per regulatory guidelines. Dropropizine enantiomers and carbamazepine (internal standard) were extracted from 50 μL rat plasma using ethyl acetate. LDP and DDP resolved with good baseline separation (Rs = 4.45) on a Chiralpak IG‐3 column. The mobile phase consisted of methanol with 0.05% diethylamine pumped at a flow rate of 0.5 mL/min. Detection and quantitation were done in multiple reaction monitoring mode following the transitions m/z 237 → 160 and 237 → 194 for dropropizine enantiomers and the internal standard, respectively, in the positive ionization mode. The proposed method provided accurate and reproducible results over the linearity range of 3.23–2022 ng/mL for each enantiomer. The intra‐ and inter‐day precisions were in the ranges of 3.38–13.6 and 5.11–13.8 for LDP and 4.19–11.8 and 8.89–10.1 for DDP. Both LDP and DDP were found to be stable under different stability conditions. The method was successfully used in a stereoselective pharmacokinetic study of dropropizine enantiomers in rats following oral administration of racemate dropropizine at 100 mg/kg. The pharmacokinetic results indicate that the disposition of dropropizine enantiomers is not stereoselective and chiral inversion does not occur in rats. 相似文献
20.