全文获取类型
收费全文 | 156篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 113篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 26篇 |
物理学 | 18篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 15篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 9篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有160条查询结果,搜索用时 15 毫秒
151.
From the roots of Salvia thymoides Benth., three new rearranged icetexane diterpenoids (2-4) were isolated together with the previously described quinone tilifolidione (1). The proposed structures were established by extensive NMR analysis, including HMBC and HMQC pulse sequences. 相似文献
152.
González de la Huebra MJ Vincent U Bordin G Rodríguez AR 《Analytical and bioanalytical chemistry》2005,382(2):433-439
A high-performance liquid chromatography method coupled to coulometric detection has been applied for the determination, in a single run, of up to eight macrolide antibiotics (erythromycin [ERY], tylosin [TYL], tilmicosin [TILM], spiramycin 2 [SPI 2], spiramycin 3 [SPI 3], josamycin [JOS], kitasamycin [KIT], and rosamicin [ROS]) in spiked porcine and bovine urine. Quantification was performed using matrix-matched calibration with roxithromycin (ROX) as the internal standard. The detection limits for each drug were below 3.5 ng injected (equivalent to an initial concentration below 0.07 mg L–1) for porcine urine and below 5 ng injected (equivalent to an initial concentration below 0.10 mg L–1) for bovine urine. Recoveries from urine samples spiked at three different concentrations within the linear range were not significantly dependent on concentration. The entire procedure provides average macrolide recoveries ranging from 69.7 to 96.6% for bovine urine and from 75.5 and 96.1% for porcine urine. 相似文献
153.
A phase-stabilized femtosecond laser comb is directly used for high-resolution spectroscopy and absolute optical frequency measurements of one- and two-photon transitions in laser-cooled 87Rb atoms. Absolute atomic transition frequencies, such as the 5S1/2 F=2-->7S1/2 F"=2 two-photon resonance measured at 788,794 768,921 (44) kHz, are determined without a priori knowledge about their values. Detailed dynamics of population transfer driven by a sequence of pulses are uncovered and taken into account for the measurement of the 5P states via resonantly enhanced two-photon transitions. 相似文献
154.
In the present paper, we establish Chen inequalities for slant submanifolds in Sasakian space forms, by using subspaces orthogonal
to the Reeb vector field ξ. 相似文献
155.
In this paper we present Perov type fixed point theorems for contractive mappings in Gheorghiu’s sense on spaces endowed with a family of vector-valued pseudo-metrics. Applications to systems of integral equations are given to illustrate the theory. The examples also prove the advantage of using vector-alued pseudo-metrics and matrices that are convergent to zero, for the study of systems of equations. 相似文献
156.
We prove that every compact nilpotent ring R of characteristic p > 0 can be embedded in a ring of upper triangular matrices over a compact commutative ring. Furthermore, we prove that every
compact topologically nilpotent ring R of characteristic p > 0, is embedded in a ring of infinite triangular matrices over
\mathbbFpw(R)\mathbb{F}_{p}^{w(R)}. 相似文献
157.
Adela Nano Dr. Raymond Ziessel Patrycya Stachelek Prof. Dr. Anthony Harriman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13528-13537
A small series of donor–acceptor molecular dyads has been synthesized and fully characterized. In each case, the acceptor is a dicyanovinyl unit and the donor is a boron dipyrromethene (BODIPY) dye equipped with a single styryl arm bearing a terminal amino group. In the absence of the acceptor, the BODIPY‐based dyes are strongly fluorescent in the far‐red region and the relaxed excited‐singlet states possess significant charge‐transfer character. As such, the emission maxima depend on both the solvent polarity and temperature. With the corresponding push–pull molecules, there is a low‐energy charge‐transfer state that can be observed by both absorption and emission spectroscopy. Here, charge‐recombination fluorescence is weak and decays over a few hundred picoseconds or so to recover the ground state. Overall, these results permit evaluation of the factors affecting the probability of charge‐recombination fluorescence in push–pull dyes. The photophysical studies are supported by cyclic voltammetry and DFT calculations. 相似文献
158.
Pilar Bermejo-Barrera Antonio Moreda-Piñeiro Jorge Moreda-Piñeiro Adela Bermejo-Barrera 《Mikrochimica acta》1998,129(1-2):71-76
A simple and rapid method for the determination of traces of silver in human hair by slurry sampling and electrothermal atomic absorption spectrometry was optimized. Hair pulverization and the particle size reduction were achieved using a vibrational zirconia mill ball for 20 min. Palladium nitrate, magnesium nitrate and palladium-magnesium nitrate were investigated as chemical modifiers to thermally stabilize silver. Glycerol was used as wetting agent to stabilize the hair slurries. A limit of detection of 21.6 g kg–1 was obtained for the use of palladium nitrate as best chemical modifier. The repeatibility of the overall procedure (slurry preparation and atomic absorption spectrometric determination) corresponding to eleven measurements was 14.3%. Matrix effect was significant and so, the standard addition method was used to determine silver in hair samples from healthy people. The levels found varied between 0.10 and 1.62 mg kg–1. 相似文献
159.
Trefzer C Škovierová H Buroni S Bobovská A Nenci S Molteni E Pojer F Pasca MR Makarov V Cole ST Riccardi G Mikušová K Johnsson K 《Journal of the American Chemical Society》2012,134(2):912-915
Benzothiazinones (BTZs) are antituberculosis drug candidates with nanomolar bactericidal activity against tubercle bacilli. Here we demonstrate that BTZs are suicide substrates of the FAD-dependent decaprenylphosphoryl-β-D-ribofuranose 2'-oxidase DprE1, an enzyme involved in cell-wall biogenesis. BTZs are reduced by DprE1 to an electrophile, which then reacts in a near-quantitative manner with an active-site cysteine of DprE1, thus providing a rationale for the extraordinary potency of BTZs. Mutant DprE1 enzymes from BTZ-resistant strains reduce BTZs to inert metabolites while avoiding covalent inactivation. Our results explain the basis for drug sensitivity and resistance to an exceptionally potent class of antituberculosis agents. 相似文献
160.
Branka Andričić Tonka Kovačić Sanja Perinović Adela Grgić 《Macromolecular Symposia》2008,263(1):96-101
Summary: Thermal properties of nanocomposites prepared of poly(L-lactide) (PLLA) and CaCO3 applying differential scanning (DSC) calorimetry and thermogravimetry (TG) were studied. Nanocomposites were prepared by extrusion process at 170 °C. DSC measurements show that CaCO3 has no influence on glass transition and melting point of PLLA but lowers its cold crystallization temperature. There is no difference in glass transition temperature of PLLA before and after extrusion. High temperature thermal stability of the PLLA in the composites is poorer than neat PLLA. Kinetic parameters also indicate greater reactivity of the system upon CaCO3 addition. 相似文献