全文获取类型
收费全文 | 296篇 |
免费 | 1篇 |
专业分类
化学 | 105篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 57篇 |
物理学 | 124篇 |
出版年
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1930年 | 1篇 |
1914年 | 2篇 |
排序方式: 共有297条查询结果,搜索用时 15 毫秒
261.
262.
The vibration spectra of and -phase PdH(D)x have been measured by neutron inelastic scattering. From a detailed analysis of the spectra, we conclude that the potentials for hydrogen and deuterium are very similar and strongly anharmonic. The results show definitively that anharmonicity is the principal contribution to the anomalous isotope dependence of the superconducting transition temperature in PdH(D). 相似文献
263.
The in situ oxidation-Wittig reaction, followed by subsequent hydrolysis, has been applied to the conversion of primary alcohols into alpha,beta-unsaturated aldehydes. This conversion, which proceeds via the intermediacy of the homologated unsaturated dioxolanes, gives good to excellent yields with a range of benzylic alcohols and heterocyclic methanols. 相似文献
264.
The artificial electron donor system, phenazine methosulfate (PMS)-ascorbate, inhibited active transort of solutes in Pseudomonas aeruginosa irrespective of whether the active transport systems were shock sensitive or shock resistant. N,N,N',N'-tetramethylphenylenediamine could be substituted for PMS but a higher concentration was required. PMS-ascorbate also inhibited active transport in several other bacterial species with the exception of Escherichia coli and of a nonpigmented strain of Serratia marcescens. PMS-ascorbate previously has been shown to energize active transport in isolated membrane vesicles, even those prepared from the same bacterial species in whose intact cells active transport was inhibited. The apparent Km of glucose active transport in untreated cells of P. aeruginosa was 40 micron while the Km of glucose transport in cells incubated with PMS-ascorbate was 25 mM, and PMS-ascorbate had no effect on efflux of accumulated glucose. These results strongly suggested that facilitated diffusion resulted upon exposure of the cells to PMS- ascorbate. Thus, PMS-ascorbate appeared to have an uncoupler-like effect on cells of P. aeruginosa. The experimental data also pointed out that there are fundamental differences between the response of intact cells and membrane vesicles to exogenous electron donors. 相似文献
265.
Array biosensor for detection of toxins 总被引:8,自引:0,他引:8
Ligler FS Taitt CR Shriver-Lake LC Sapsford KE Shubin Y Golden JP 《Analytical and bioanalytical chemistry》2003,377(3):469-477
The array biosensor is capable of detecting multiple targets rapidly and simultaneously on the surface of a single waveguide. Sandwich and competitive fluoroimmunoassays have been developed to detect high and low molecular weight toxins, respectively, in complex samples. Recognition molecules (usually antibodies) were first immobilized in specific locations on the waveguide and the resultant patterned array was used to interrogate up to 12 different samples for the presence of multiple different analytes. Upon binding of a fluorescent analyte or fluorescent immunocomplex, the pattern of fluorescent spots was detected using a CCD camera. Automated image analysis was used to determine a mean fluorescence value for each assay spot and to subtract the local background signal. The location of the spot and its mean fluorescence value were used to determine the toxin identity and concentration. Toxins were measured in clinical fluids, environmental samples and foods, with minimal sample preparation. Results are shown for rapid analyses of staphylococcal enterotoxin B, ricin, cholera toxin, botulinum toxoids, trinitrotoluene, and the mycotoxin fumonisin. Toxins were detected at levels as low as 0.5 ng mL–1. 相似文献
266.
A high pressure UV-visible spectrophotometer was used to determine the dissociation constant of boric acid using an indicator technique. The measurements were made at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. Extrapolation to I=0 gave a thermodynamic dissociation constant of 5.16×10–10 at 1 atm. The pressure dependence yielded a partial molal volume change of –28.9 and –31.8 cm3-mol–1 and a compressibility change of –3.1 and –4.8×10–3 cm3-mol–1-atm–1 for the dissociation at I=0.1 and 1.0m, respectively. The association constant for the formation of the sodium borate ion pair was determined by comparing the acid constants in tetramethylammonium chloride to those in sodium chloride solutions. Extrapolation to I=0 yielded a KA for [NaB(OH)4] of 0.64 at 1 atm. The pressure dependence of KA gave
and
for the formation of the ion pair. 相似文献
267.
Excitation of iodine fluorescence with a single mode tunable dye laser allows extensive observation of features from vibrationally and rotationally transferred states populated through collisions. We have measured the circular polarisation of these features and observe a very high degree of polarisation following both vibrational and rotational energy transfer: thus transitions from states following ΔJ′ = 60 and Δν′ = 1, ΔJ′ = 60 are still highly polarized. This implies strong conservation of MJ throughout energetic inelastic collisions. 相似文献
268.
P. A. Baedecker J. J. Rowe E. Steinnes 《Journal of Radioanalytical and Nuclear Chemistry》1977,40(1-2):115-146
The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution
coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S.
standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been
evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach
is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use
of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. 相似文献
269.
Novotný O Sivaraman B Rebrion-Rowe C Travers D Biennier L Mitchell JB Rowe BR 《The Journal of chemical physics》2005,123(10):104303
A new technique, flowing afterglow with photoions (FIAPI), has been developed to measure the rate coefficient for the recombination of complex ions, and, in particular, polycyclic aromatic hydrocarbon (PAH) cations with electrons. The method is based on the flowing afterglow Langmuir probe - mass spectrometer apparatus at the University of Rennes I. A helium plasma is generated by a microwave discharge in a He buffer gas and downstream, a small amount of argon gas is injected to destroy any helium metastables. A very small amount of neutral PAH molecules is added to the afterglow plasma by evaporation from a plate coated with the PAH to be studied. PAH ions are then produced by photoionization of the parent molecule using a pulsed UV laser (157 nm). The laser beam is oriented along the flow tube and so a constant spatial concentration of photoions is obtained. The electron concentration along the flow tube is measured by means of a movable Langmuir probe. Ion concentration decay in time is measured at a fixed position using a quadrupole mass spectrometer which is triggered by the laser pulse. The recombination of anthracene and pyrene cations has been studied using this technique and we have found a recombination rate of (2.4 +/- 0.8) x 10(-6) cm(3) s(-1) for anthracene and (4.1 +/- 1.2) x 10(-6) cm(3) s(-1) for pyrene. 相似文献
270.
Kanda S Olsen SL Ueno K Kirk P Cheng CP Ye MH Abashian A Gotow K Haim D Mattson ME Piilonen L Sterner KL Choi SK Lusin S Rosenfeld C Wilson S Zheng LY Fry CA Tanaka R Chinitz LM Ko W Lander RL Rowe J Smith JR Stuart D Abe K Breedon RE Fujii Y Kurihara Y Liu F Maki A Nozaki T Omori T Sagawa H Sakai Y Sasaki T Sugimoto Y Takaiwa Y Terada S Kajino F Aso T Miyano K Miyata H Ohkubo K Oyoshi M Shirai M Takashimizu N Yamashita Y Schnetzer S Vinson J Walker RC Bodek A Kim BJ Kumita T Velissaris C 《Physical review D: Particles and fields》1995,52(9):4872-4876