全文获取类型
收费全文 | 967篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 547篇 |
晶体学 | 15篇 |
力学 | 11篇 |
数学 | 92篇 |
物理学 | 319篇 |
出版年
2021年 | 9篇 |
2019年 | 8篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 6篇 |
2013年 | 76篇 |
2012年 | 36篇 |
2011年 | 34篇 |
2010年 | 25篇 |
2009年 | 15篇 |
2008年 | 30篇 |
2007年 | 45篇 |
2006年 | 45篇 |
2005年 | 41篇 |
2004年 | 27篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 25篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 17篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 27篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 17篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1970年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有984条查询结果,搜索用时 15 毫秒
111.
Rebecca A.H. Butler Paul Helminger Ewa Bialkowska-Jaworska 《Journal of Molecular Spectroscopy》2007,244(2):113-116
The pure rotational spectrum of chlorine nitrate in its v6 = 1 excited vibrational state has been studied. A total of 2901 lines, with Ka extending to 33 in the 35Cl isotopologue and 30 in the 37Cl isotopologue, respectively, have been recorded and assigned. This analysis, along with our recently reported study of the ν5/ν6ν9 dyad and the improved energy levels of ν9 reported in this paper, should make possible accurate simulation of the corresponding ν6 band and its complex hot band structure near 435 cm−1. 相似文献
112.
C. Brihaye T. A. Butler F. F. Knapp Jr. 《Journal of Radioanalytical and Nuclear Chemistry》1986,102(2):399-411
An evaluation of adsorbents for potential use in the191Os/191mIr medical radionuclide generator was performed. The adsorbents included 39 inorganic materials broadly classified as oxides, antimonates, ferro-ferricyanides, phosphates, sulfides, and miscellaneous including activated carbon and the organic anion-exchanger AGMP-1. The uptake of191Os in oxidation states (VI) [potassium tetrachloroosmate], (IV) [potassium hexachloroosmate] and (III) [potassium hexathiocyanatoosmate] was measured. Adsorbents having a high191Os uptake were evaluated for191mIr elution yield using three physiologically compatible eluents. Only activated carbon and AGMP-1 adsorbents showed significant191mIr elution yields under the test conditions (10% and 37%, respectively). The results of these studies suggest that activated carbon may be a promising adsorbent for development of a new191Os/191mIr medical radionuclide generator. Activated carbon is a good candidate for further development since it is inert to the chemical and radiation effects which may effect an organic based ion exchange material such as AGMP-1.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc. 相似文献
113.
Butler J.M. Wharton C.B. Furukawa S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(3):490-496
The operation of a backward wave oscillator (BWO) is shown to be critically dependent on the energy of the slow space-charge wave of the electron beam. Experimental work parameterizing the dependence of microwave frequency on effective beam energy, γbeam, reveals that through an understanding of electron-beam dynamics, a BWO could be systematically tuned through a desired frequency range while maintaining a high power of a few hundred megawatts and narrow frequency bandwidth, which was 400 MHz. Through variation of γbeam, 1.2 to 1.5 for the experiment, the lack of scaling of peak microwave power with the kinetic energy of the electron beam for γbeam >1.32 was observed. This effect was previously found in numerical simulation. In order to explain this effect, the relationship of the beam current to the space-charge-limiting current for increasing γbeam is examined. Dramatic evidence of pulse shortening, a phenomenon known to relativistic oscillators, was also seen 相似文献
114.
The electrochemical and spectrophotometric characterization of the complex formed from samarium diiodide and 4 equiv of tripyrrolidinophosphoric acid triamide (TPPA) is presented. Kinetic studies indicate that the SmI(2)/TPPA complex possesses reactivity greater than the complex formed between samarium diiodide and 4 equiv of HMPA. Examples of the use of SmI(2)/TPPA in synthesis are presented. 相似文献
115.
Jayaprakash KN Peng CG Butler D Varghese JP Maier MA Rajeev KG Manoharan M 《Organic letters》2010,12(23):5410-5413
Novel non-nucleoside alkyne monomers compatible with oligonucleotide synthesis were designed, synthesized, and efficiently incorporated into RNA and RNA analogues during solid-phase synthesis. These modifications allowed site-specific conjugation of ligands to the RNA oligonucleotides through copper-assisted (CuAAC) and copper-free strain-promoted azide-alkyne cycloaddition (SPAAC) reactions. The SPAAC click reactions of cyclooctyne-oligonucleotides with various classes of azido-functionalized ligands in solution phase and on solid phase were efficient and quantitative and occurred under mild reaction conditions. The SPAAC reaction provides a method for the synthesis of oligonucleotide-ligand conjugates uncontaminated with copper ions. 相似文献
116.
Steiniger D Lu G Butler J Phillips E Fintschenko Y 《Journal of AOAC International》2010,93(4):1169-1179
The pesticide residues in exported and imported tea products must not exceed the maximum residue limits (MRLs) regulated by the import countries. Tea is a complex matrix that obfuscates the determination of pesticide residues. Many available methods for multiresidue pesticide analysis of tea are time-consuming and require many cleanup steps. The objective of this study was to develop a simple multiresidue method by using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and ion-trap GC/MS/MS, which can identify, confirm, and quantify pesticides in complex matrixes. A tea product was homogenized with water, and the pesticides were extracted with acetonitrile containing 1% acetic acid. The extract was subjected to centrifugation, initial cleanup with dispersive SPE (dSPE), solvent exchange, and final cleanup with dSPE. Diethyl-d10-parathion and triphenyl phosphate were used as the internal standard and surrogate, respectively. The final extract was injected into an ITQ 700 gas chromatograph/mass spectrometer. Quantitation of individual pesticides was based on matrix-matched calibration curves with a correlation coefficient of > 0.9930 for the 22 pesticides selected for the study. The recoveries of the 22 pesticides ranged from 78 to 115%, except those for diazinon (130%) and malathion (122%), with an average RSD of 8.7%. The LOD values of all of the pesticides, except for terbufos, were below the MRLs set by the European Union and Japan. 相似文献
117.
Andresen GB Ashkezari MD Baquero-Ruiz M Bertsche W Bowe PD Butler E Carpenter PT Cesar CL Chapman S Charlton M Fajans J Friesen T Fujiwara MC Gill DR Hangst JS Hardy WN Hayden ME Humphries AJ Hurt JL Hydomako R Jonsell S Madsen N Menary S Nolan P Olchanski K Olin A Povilus A Pusa P Robicheaux F Sarid E Silveira DM So C Storey JW Thompson RI van der Werf DP Wurtele JS Yamazaki Y;ALPHA Collaboration 《Physical review letters》2011,106(2):025002
We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. 相似文献
118.
Seongsin M.Kim William Baughman David S.Wilbert Lee Butler Michael Bolus Soner Balci Patrick Kung 《中国光学快报(英文版)》2011,(11):46-49
We demonstrate two distinct emerging terahertz (THz) biomedical imaging techniques.One is based on the use of a new single frequency THz quantum cascade laser and the other is based on broadband THz time domain spectrocopy.The first method is employed to derive a metastasis lung tissue imaging at 3.7 THz with clear contrast between cancerous and healthy areas.The second approach is used to study an osseous tissue under several imaging modalities and achieve full THz spectroscopic imaging based on the freque... 相似文献
119.
With the advance of atomic absorption spectroscopy and the degree of automation obtained in instruments today, the preparation of calibration curves and the ensuing calculations are, apart from the sample preparation in certain cases, the most time consuming part of an atomic absorption analysis. It is usually at this stage that errors are introduced, either as a result of miscalculation or of the operator's personal bias. Both these factors can be overcome by using a programmable desk calculating system, and would be of special importance to laboratories where routine analyses are conducted. It is also of use in cases where elements are only determined periodically. 相似文献
120.
We introduce a class of set-functions on the set of natural numbers, which are called super-measures. Super-measures are then
utilized to characterize a certain class of topological measures (previously called quasi-measures, see below) which arises
naturally. The members of this class of topological measures are called finitely defined, and are shown to be dense in the
set of all topological measures.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献