全文获取类型
收费全文 | 235篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 177篇 |
晶体学 | 3篇 |
数学 | 14篇 |
物理学 | 57篇 |
出版年
2024年 | 6篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1957年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
51.
Bhavesh Babulal Gabani Suresh P. Sulochana Vinay Kiran Umesh Todmal Ramesh Mullangi 《Biomedical chromatography : BMC》2019,33(11)
A liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) method has been developed and validated for the quantification of tunicamycin in rat plasma as per regulatory guideline. Chromatography of tunicamycin and the IS in the processed plasma samples was achieved on an X‐Terra phenyl column using a binary gradient (mobile phase A, acetonitrile and mobile phase B, 5 mm ammonium formate) elution at a flow rate of 0.6 ml/min. LC–MS/MS was operated under the multiple reaction monitoring mode using the electrospray ionization technique in positive ion mode and the transitions of m/z 817.18 → 596.10, 831.43 → 610.10, 845.29 → 624.10, 859.23 → 638.10 and 309.24 → 163.20 were used to quantitate homologs A–D and the IS, respectively. The total chromatographic run time was 4.5 min. The correlation coefficient (r2) was >0.99 for all homologs with accuracy 90.7–107.4% and precision 0.74–15.1%. The recovery of homologs was 78.6–90.2%. No carryover was observed and the matrix effect was minimal. Tunicamycin four homologs were found to be stable on the bench‐top for 6 h, for up to three freeze–thaw cycles, in the injector for 24 h and for 1 month at ?80 ° C. The applicability of the validated method has been demonstrated in a rat pharmacokinetic study. 相似文献
52.
53.
In this work, we have made an effort to determine whether the effective atomic numbers of H-, C-, N- and O-based composite
materials would indeed remain a constant over the energy grid of 280–1200 keV wherein incoherent scattering dominates their
interaction with photons. For this purpose, the differential incoherent scattering cross-sections of Be, C, Mg, Al, Ca and
Ti were measured for three scattering angles 60°, 80° and 100° at 279.1, 661.6 and 1115.5 keV using which an expression for
the effective atomic number was derived. The differential incoherent scattering cross-sections of the composite materials
of interest measured at these three angles in the same set-up and substituted in this expression would yield their effective
atomic number at the three energies. Results obtained in this manner for bakelite, nylon, epoxy, teflon, perspex and some
sugars, fatty acids as well as amino acids agreed to within 2% of some of the other available values. It was also observed
that for each of these samples, Z
eff was almost a constant at the three energies which unambiguously justified the conclusions drawn by other authors earlier
[Manjunathaguru and Umesh, J. Phys. B: At. Mol. Opt. Phys.
39, 3969 (2006); Manohara et al,Nucl. Instrum. Methods
B266, 3906 (2008); Manohara et al Phys. Med. Biol.
53, M377 (2008)] based on total interaction cross-sections in the energy grid of interest. 相似文献
54.
Umesh Balakrishnan Nallamuthu Ananthi Sakthivel Tamil Selvan Ravindra Pal Dr. Katsuhiko Ariga Dr. Sivan Velmathi Dr. Ajayan Vinu Dr. 《化学:亚洲杂志》2010,5(4):897-903
The immobilization of chiral oxazaborolidine complex in the well‐ordered mesochannels of SBA‐15 is demonstrated by a postsynthetic approach using 3‐aminopropyltriethoxysilane as a reactive surface modifier. The immobilized catalysts are characterized by various techniques, such as XRD, nitrogen adsorption, HRSEM, UV/Vis diffuse reflectance spectroscopy, and FTIR spectroscopy. The catalysts are used for the enantioselective reduction of aromatic prochiral ketones. The activity of the chiral oxazaborolidine complex immobilized SBA‐15 catalysts is also compared with that of the pure chiral oxazaborolidine complex, which is a homogeneous catalyst. It is found that the activity of the chiral complex immobilized SBA‐15 heterogeneous catalyst is comparable with that of the homogeneous catalyst. 相似文献
55.
Two new methods based on FT–Raman spectroscopy, one simple, based on band intensity ratio, and the other using a partial least squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1,096 cm?1 bands. For calibration purposes, 80.5% crystalline and 120-min milled (0% crystalline) Whatman CC31 and six cellulose mixtures produced with crystallinities in the range 10.9–64% were used. When intensity ratios were plotted against crystallinities of the calibration set samples, the plot showed a linear correlation (coefficient of determination R 2 = 0.992). Average standard error calculated from replicate Raman acquisitions indicated that the cellulose Raman crystallinity model was reliable. Crystallinities of the cellulose mixtures samples were also calculated from X-ray diffractograms using the amorphous contribution subtraction (Segal) method and it was found that the Raman model was better. Additionally, using both Raman and X-ray techniques, sample crystallinities were determined from partially crystalline cellulose samples that were generated by grinding Whatman CC31 in a vibratory mill. The two techniques showed significant differences. In the second approach, successful Raman PLS regression models for crystallinity, covering the 0–80.5% range, were generated from the ten calibration set Raman spectra. Both univariate-Raman and WAXS determined crystallinities were used as references. The calibration models had strong relationships between determined and predicted crystallinity values (R 2 = 0.998 and 0.984, for univariate-Raman and WAXS referenced models, respectively). Compared to WAXS, univariate-Raman referenced model was found to be better (root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values of 6.1 and 7.9% vs. 1.8 and 3.3%, respectively). It was concluded that either of the two Raman methods could be used for cellulose I crystallinity determination in cellulose samples. 相似文献
56.
Umesh N. Tripathi Ghanshyam Srivastava Ram C. Mehrotra 《Transition Metal Chemistry》1994,19(6):564-566
Summary Solids of the stoichiometric formulae [Fe{S2P(OPr-n)2}3] and [Fe{S2PO2G}3] (G = —CH2CMe2CH2—, CMe2–CMe2— or —CH2CH2CHMe—) are precipitated from the reactions of FeCl3 with ammonium dithiophosphates in water. Soluble complexes of the type [Fe{S2PO2G}2], formed by the reactions of FeCl2 with NH4[{S2PO2G}] in MeOH, can be extracted with benzene. Adducts of the types [Fe{S2PO2G}2L] and [Fe{S2PO2G}2(PPh3)2] are formed by the reaction of [Fe{S2PO2G}2] with L (L = 2,2-bipyridyl or 1,10-phenanthroline) and PPh3, respectively. All the compounds have been characterized by i.r. and u.v.-vis. spectroscopy and magnetic studies.This paper is dedicated to the late Dr. G. Srivastava, Associate Professor, Department of Chemistry, Rajasthan University, Jaipur. 相似文献
57.
Nehete UN Roesky HW Zhu H Nembenna S Schmidt HG Noltemeyer M Bogdanov D Samwer K 《Inorganic chemistry》2005,44(20):7243-7248
The cobalt(II) and iron(II) siloxane compounds were prepared by the reaction of lipophilic N-bonded silanetriol 1 with metal silylamides M[N(SiMe3)2]2 (M = Co (2), Fe (3)) in a 1:1 and 3:4 molar ratio, respectively. A plot of 1/chi versus temperature in the range of 2-300 K indicates the paramagnetic behavior of 2 and 3. The composition and molecular structures of 2 and 3 were fully determined by IR, elemental analysis, and X-ray crystal structural analyses. Compound 2 possesses a pseudo-4-fold (S4) symmetry, whereas 3 reveals an inversion center. Compound 2 represents a tetracobalt(II) drum while 3 exhibits an octairon(II) cage containing siloxane ligands. 相似文献
58.
Annigeri Satish M. Naik Anil D. Gangadharmath Umesh B. Revankar Vidyanand K. Mahale Vinayak B. 《Transition Metal Chemistry》2002,27(3):316-320
Four binuclear transition metal(II) complexes: [Co2L(-Cl)Cl2] · 2H2O, [Ni2L(-Cl)Cl2(H2O)2] · 2H2O, [Cu2L(-Cl)Cl2] · 2H2O and [Zn2L(-Cl)Cl2] · 2H2O, where LH is the binucleating ligand 2,6-diformyl-4-methylphenol bis(2-hydrazino benzothiazole), were prepared. Based on the i.r. spectra, elemental analysis, conductivity measurements and thermal analysis, we propose that these complexes contain an endogenous phenoxide bridge and an exogenous chloride bridge. Magnetic and spectral data supports the existence of a weak antiferromagnetic interaction between the metal ions, and octahedral for NiII and a square pyramidal environment for remaining complexes. The compounds show significant growth inhibitory activity against the fungi, Aspergillus niger and Candida albicans, as compared to antibacterial activity against Bacillus cirroflagellosus and Pseudomonas auregenosa. 相似文献
59.
K.P. Gopinathan Nair Channe Gowda J.Shylaja Kumari S.J. Anasuya T.K. Umesh Ramakrishna Gowda 《Radiation Physics and Chemistry》1994,43(6):581-584
Total attenuation cross sections for several amino acids have been measured for Ba133 photons in a narrow beam good geometry setup, using a hyper pure germanium detector. These values are compared with the values calculated using the mixture rule based on the data of Hubbell for the individual elements and found to be in good agreement. 相似文献
60.
Bianchi .Type-I Massive String Magnetized Barotropic Perfect Fluid Cosmological Model in General Relativity
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
BALI Raj PAREEK Umesh Kumar PRADHAN Anirudh 《中国物理快报》2007,24(8):2455-2458
Bianchi type-I massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel is investigated. To obtain the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced Mong the x-axis with infinite electrical conduictivity. The behaviour of the model in the presence and absence of magnetic field together with other physical aspects is further discussed. 相似文献