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301.
D Tasdemir G C Mangalindan G P Concepción M K Harper C M Ireland 《Chemical & pharmaceutical bulletin》2001,49(12):1628-1630
A new purine 3,7-dimethylguanine (1) has been isolated from the marine sponge Zyzzya fuliginosa, along with the known metabolites, makaluvamines A, C, K (2--4), 4-hydroxyphenylacetic acid (5), methyl ester of 4-hydroxyphenylacetic acid (6), 4-hydroxyphenethyl alcohol (7), L-phenylalanine (8) and L-tryptophan (9). The structure of 3,7-dimethylguanine (1) was elucidated by analysis of 1D and 2D (one- and two-dimensional) NMR [HMQC (heteronuclear multiple quantum coherence), gHMBC (heteronuclear multiple bond connectivity), 1H-15N gHMBC] data, mass spectroscopy data, and by comparison with 3,7-dimethylisoguanine (10). 相似文献
302.
Andre H. St.Amant Fengying Huang Jia Lin Keith Rickert Vaheh Oganesyan Daniel Lemen Shenlan Mao Jay Harper Marcello Marelli Herren Wu Changshou Gao Javier ReaddeAlaniz R. James Christie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8577-8581
Here, we describe a diene‐containing noncanonical amino acid (ncAA) capable of undergoing fast and selective normal electron‐demand Diels–Alder (DA) reactions following its incorporation into antibodies. A cyclopentadiene derivative of lysine (CpHK) served as the reactive handle for DA transformations and the substrate for genetic incorporation. CpHK incorporated into antibodies with high efficiency and was available for maleimide conjugation or self‐reaction depending on position in the amino acid sequence. CpHK at position K274 reacted with the maleimide drug‐linker AZ1508 at a rate of ≈79 m ?1 s?1 to produce functional antibody–drug conjugates (ADCs) in a one‐step process. Incorporation of CpHK at position S239 resulted in dimerization, which covalently linked antibody heavy chains together. The diene ncAA described here is capable of producing therapeutic protein conjugates with clinically validated and widely available maleimide compounds, while also enabling proximity‐based stapling through a DA dimerization reaction. 相似文献
303.
P.E. Harper S.M. Gruner R.N.A.H. Lewis R.N. McElhaney 《The European physical journal. E, Soft matter》2000,2(3):229-245
This is the second of two papers dealing with the structure of lipid-water phases based on Infinite Periodic Minimal Surfaces
(IPMS). The first paper describes mathematical modeling of such phases. In this paper, a new reconstruction method, called
the methyl trough search, is described and used to solve the structures based on powder pattern X-ray diffraction data. Structures
are derived for both a single chain lipid-water system (mono-olein) and a diacyl phospholipid-water system (2-2 methyl butyl
16:0 phosphatidylcholine). The methyl trough search uses the low electron density of the lipid methyl tails to determine the
correct phasing for the electron density reconstruction. The data are consistent with a structure based on the IPMS D surface.
The results are compared to other methods used to solve the mono-olein structure; the structure of the diacyl lipid has never
before been solved. We discuss the subtleties involved in reconstruction of D surface based phases and the substantial artifacts
that arise in low-resolution reconstructions of hydrocarbon lipids lacking heavy-atom sites.
Received 15 January 1999 and Received in final form 20 October 1999 相似文献
304.
Jian Zhi Hu James K Harper Craig Taylor Ronald J Pugmire David M Grant 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,142(2):326
The spectral editing approach of Zilm and coworkers utilizes polarization, polarization inversion, and spin depolarization methods for enhancing or suppressing NMR spectral lines in solids. The proposed pulse sequences allow nonprotonated C, CH, CH2, and CH3 types of carbon resonances to be separated from one another and identified accordingly. The former method tentatively separates the nonprotonated C and CH3 peaks with a cutoff shift of 35 ppm. This shift is a reasonable demarcation shift for a preponderance of organic molecules, but exceptions do exist that could constitute a serious drawback in a few instances. The new approach separates the nonprotonated C and CH3 carbon peaks unequivocally using modified pulse sequences similar to those of Zilm. Further, both the CH only and CH2 only spectra, respectively, can be acquired directly from combining so called (+) and (−) sequences using different spectral delay periods and pulse parameters. The (+) and the (−) pulse sequences produce signals for the nonprotonated and methyl carbons that have essentially the same amplitude but opposite phases. These spectra, combined with the previously reported CH3 and nonprontonated C only spectra, offer a complete spectral editing technique for solid samples. Examples of these spectral editing methods are provided for 3-methylglutaric acid, fumaric acid monoethyl ester, and two complex natural products: methyl o-methylpodocarpate and 10-deacetylbaccatin III. 相似文献
305.
Zolot AM Harper WW Perkins BG Dagdigian PJ Nesbitt DJ 《The Journal of chemical physics》2006,125(2):21101
Exothermic reactive scattering of F atoms at the gas-liquid interface of a liquid hydrocarbon (squalane) surface has been studied under single collision conditions by shot noise limited high-resolution infrared absorption on the nascent HF(v,J) product. The nascent HF(v,J) vibrational distributions are inverted, indicating insufficient time for complete vibrational energy transfer into the surface liquid. The HF(v=2,J) rotational distributions are well fit with a two temperature Boltzmann analysis, with a near room temperature component (T(TD) approximately equal to 290 K) and a second much hotter scattering component (T(HDS) approximately equal to 1040 K). These data provide quantum state level support for microscopic branching in the atom abstraction dynamics corresponding to escape of nascent HF from the liquid surface on time scales both slow and fast with respect to rotational relaxation. 相似文献
306.
307.
308.
Sandoval IT Davis RA Bugni TS Concepcion GP Harper MK Ireland CM 《Natural product research》2004,18(1):89-93
Bioassay-guided fractionation of two Philippine sponges of the genus Petrosia has resulted in the isolation of the novel natural product cribrostatin 7 (1) and the known compounds renierone (2) and O-demethylrenierone (3). The structures of these isoquinoline quinones were determined by interpretation of spectroscopic data. Compounds 1, 2 and 3 were cytotoxic against the HCT 116 human colon carcinoma cell line with IC50 values of 45, 24 and 34 microg/mL, respectively. 相似文献
309.
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