全文获取类型
收费全文 | 546篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 323篇 |
晶体学 | 8篇 |
力学 | 14篇 |
数学 | 37篇 |
物理学 | 177篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 26篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 26篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 25篇 |
2013年 | 50篇 |
2012年 | 33篇 |
2011年 | 43篇 |
2010年 | 12篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 27篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 2篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有559条查询结果,搜索用时 31 毫秒
11.
N-Methylaminothioformyl-N'-phenylhydroxylamine forms a 1:2 (metal:ligand) greenish yellow complex with cobalt(II). This complex has maximum absorption at 470 nm with a molar absorptivity of 1.65 x 10(4) 1.mole(-1).cm(-1). Beer's law is obeyed over the concentration range 6 x 10(-6)-6 x 10(-5)M. The effect of diverse ions is described. 相似文献
12.
A versatile microfabricated platform for electrophoresis of double- and single-stranded DNA 总被引:1,自引:0,他引:1
We demonstrate a versatile microfabricated electrophoresis platform, incorporating arrays of integrated on-chip electrodes, heaters, and temperature sensors. This design allows a range of different sieving gels to be used within the same device to perform separations involving both single- and double-stranded DNA over distances on the order of 1 cm. We use this device to compare linear and cross-linked polyacrylamide, agarose, and thermo-reversible Pluronic-F127 gels on the basis of gel casting ease, reusability, and overall separation performance using a 100 base pair double-stranded DNA ladder as a standard sample. While cross-linked polyacrylamide matrices provide consistently high-quality separations in our system over a wide range of DNA fragment sizes, Pluronic gels also offer compelling advantages in terms of the ability to remove and reload the gel. Agarose gels offer good separation performance, however, additional care must be exercised to ensure consistent gel properties as a consequence of the need for elevated gel loading temperatures. We also demonstrate the use of denaturing cross-linked polyacrylamide gels at concentrations up to 19% to separate single-stranded DNA fragments ranging in size from 18 to 400 bases in length. Primers differing by 4 bases at a read length of 30 bases can be separated with a resolution of 0.9-1.0 in under 20 min. This level of performance is sufficient to conduct a variety of genotyping assays including the rapid detection of single nucleotide polymorphisms (SNPs) in a microfabricated platform. The ability to use a single microelectrophoresis system to satisfy a wide range of separation applications offers molecular biologists an unprecedented level of flexibility in a portable and inexpensive format. 相似文献
13.
Spectrophotometric Determination of Rhenium(IV) with Thiocyanate,TX-100 and N,N′-Diphenylbenzamidine
A spectrophotometric method to determine rhenium(IV) at trace level is based on the extraction of Re(IV)-SCN? complex in sulphuric acid media with N,N′-diphenylbenzamidine(DPBA) in presence of a non-ionic surfactant triton X-100 (TX-100) in chloroform. The complex shows maximum absorbance at 435 nm with amolar absorptivity value of 4.24 × 104 L mol?1 cm?1 at an acidity range 3.5-6.5 M H2SO4. The method followed Beer's Law for the system Re(IV)-SCN?(TX-100)-DPBA upto 4.0 μg Re(IV) mL?1. The detection limit of the method is 5 ppb. None of the tested foreign ions, except molybdenum(VI), interfere with the determination of rhenium. The interference due to molybdenum could effectively be removed by prior precipitation with oxine. The effect of various analytical parameters on the extraction of the metal are discussed. 相似文献
14.
A simple and sensitive field detection and spectrophotometric method for determination of copper described herewith is based on the formation of a red coloured species of copper(II) with 1-[pyridyl-(2)-azo]-naphthol-(2) (PAN), TX-100 and N,N'-diphenylbenzamidine (DPBA) at pH range 7.8-9.4. The red coloured Cu(II)-PAN-(TX-100)-DPBA complex in chloroform shows maximum absorbance at 520 nm with molar absorptivity value of 1.14x10(5) l mol(-1) cm(-1). The detection limit of the method is 2 ng ml(-1) organic phase. The system obeys Beer's law up to 0.6 mug Cu(II) ml(-1) in organic solution. Most of the common metal ions generally found associated with copper do not interfere. The repeatability of the method was checked by finding relative standard deviation (RSD) (n=10) value for solutions each containing 0.2 mug ml(-1) of Cu(II) and the RSD value of the method was found to be 1.5%. The validity of the method has been satisfactorily examined for the determination of copper in soil and airborne dust particulate samples. 相似文献
15.
Sang-Min Jang Christophe E. Redon Bhushan L. Thakur Meriam K. Bahta Mirit I. Aladjem 《Experimental & molecular medicine》2020,52(10):1637
The last decade has revealed new roles for Cullin-RING ubiquitin ligases (CRLs) in a myriad of cellular processes, including cell cycle progression. In addition to CRL1, also named SCF (SKP1-Cullin 1-F box protein), which has been known for decades as an important factor in the regulation of the cell cycle, it is now evident that all eight CRL family members are involved in the intricate cellular pathways driving cell cycle progression. In this review, we summarize the structure of CRLs and their functions in driving the cell cycle. We focus on how CRLs target key proteins for degradation or otherwise alter their functions to control the progression over the various cell cycle phases leading to cell division. We also summarize how CRLs and the anaphase-promoting complex/cyclosome (APC/C) ligase complex closely cooperate to govern efficient cell cycle progression.Subject terms: Drug development, Targeted therapies, Origin firing, Chromatin remodelling, Post-translational modifications 相似文献
16.
Ali G. Ozkabak Surya N. Thakur Lionel Goodman 《International journal of quantum chemistry》1991,39(3):411-422
C6H6 Raman scattering activities calculated from harmonic model ab initio Hartree–Fock 6–311 ++ G(d, p) polarizability derivatives (and harmonic force fields calculated at the same level) accurately simulate experiment (to within 1% for the a1g modes). Accurate predictions are also made for the e2g modes (to within 5% for ν7 and ν9, and more poorly for ν6 and ν8 [in Fermi resonance with ν6 + ν1]) and for the e1g out-of-plane mode, ν10. Only the ν6 in-plane CCC bending mode scattering activity is found to be anomalous. Systematic variation of the basis set indicates that the benzene scattering activities and depolarization ratios are strongly dependent on inclusion of both carbon and hydrogen atom diffuse functions in the basis set. Predictions are also made for 12C6D6 and for unmeasured intensities in 13C6H6. Measurements of a1g mode scattering activities in the latter molecule are predicted to be useful in testing the harmonic Hartree–Fock Raman intensity model. 相似文献
17.
R. T. Chitnis S. G. Talnikar V. A. Thakur A. H. Paranjape 《Journal of Radioanalytical and Nuclear Chemistry》1979,49(1):63-70
The method for plutonium determination based on secondary controlled-potential coulometry, as described by SHULTS, is applied
for analysis in the range of 0.1–5 mg plutonium. The method involves the oxidation of plutonium to Pu(VI) with perchloric
acid followed by its reduction by an internally generated ferrous mediator. This is a two step procedure, involving the reduction
of Pu(VI) and Fe(III) to a mixture of Pu(III) and Fe(II), followed by the oxidation of Pu(III) and Fe(II) to Pu(IV) and Fe(III),
respectively. The net results is the reduction of Pu(VI) to Pu(IV), measured as the difference between the currents consumed
during the reduction and oxidation steps. The original method of SHULTS involves 10–25 mg plutonium for each determination.
Since the present method is intended for the analysis of smaller amounts of plutonium, the oxidation procedure described in
the original version had to be modified. The method is found to work satisfactorily with a precision better than 0.1% at 5
mg level and 1.2% for 0.1 mg plutonium. 相似文献
18.
Prasad RL Prasad R Bhar GC Thakur SN 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(14):3093-3102
IR spectra in the 'Finger Print' spectral range has great importance in qualitative and quantitative analysis of explosives like trinitrotoluene (TNT) and cyclotrimethyltrinitramine (RDX). Highly resolved IR bands of these compounds have been recorded in the 9.6 and 10.6 microm regions of CO2 laser. TNT and RDX are large molecules each having 21 atoms and it is very difficult to assign the modes of vibrations by comparison with those in other molecules making the vibrational assignments of observed bands a difficult task. The ab initio quantum chemical calculation is used for determining the molecular geometries and modes of vibration of these molecules with a view to assign their normal modes in the high resolution vibrational photoacoustic spectra. These assignments are very reliable in view of the good agreement between the observed and calculated frequencies of deuterated TNT. 相似文献
19.
A new and efficient method for the rearrangement of oximes 1 has been achieved by a simple reaction of a ketoximes with bismuth trichloride under microwave irradiation in the solid state. 相似文献
20.