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41.
42.
Walter J. Gutjahr Stefan Katzensteiner Peter Reiter Christian Stummer Michaela Denk 《Central European Journal of Operations Research》2008,16(3):281-306
This paper presents a new model for project portfolio selection, paying specific attention to competence development. The
model seeks to maximize a weighted average of economic gains from projects and strategic gains from the increment of desirable
competencies. As a sub-problem, scheduling and staff assignment for a candidate set of selected projects must also be optimized.
We provide a nonlinear mixed-integer program formulation for the overall problem, and then propose heuristic solution techniques
composed of (1) a greedy heuristic for the scheduling and staff assignment part, and (2) two (alternative) metaheuristics
for the project selection part. The paper outlines experimental results on a real-world application provided by the E-Commerce
Competence Center Austria and, for a slightly simplified instance, presents comparisons with the exact solution computed by
CPLEX. 相似文献
43.
Michaela Wilhelm Eva Berssen Rainer Koch Henry Strasdeit 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1097-1108
Summary. Lipoyl imidazolide reacts with aza-15-crown-5 (1,4,7,10-tetraoxa-13-azacyclopentadecane) or aza-18-crown-6 (1,4,7,10,13-pentaoxa-16-azacyclooctadecane)
to afford new N-lipoylated azacrown compounds in good yields. These compounds can be transformed into 1,3-dithiols and amines by reduction
with complex hydrides of the disulfide and/or amide group of the lipoyl chain. The new pendant-arm macrocycles react as heteroditopic
ligands by forming dithiolate and disulfide complexes with the ‘soft’ metal ions Ni2+ and Pd2+, respectively, and an amine complex with the ‘hard’ Li+ ion. Semiempirical and DFT calculations on the complexation of a lithium ion give a most favourable structure in which the
azacrown and two solvent molecules are in contact with the metal but not the pendant arm.
Received January 29, 2002; accepted (revised) March 25, 2002 相似文献
44.
Susanne Schmidt Michaela Zietz Monika Schreiner Sascha Rohn Lothar W. Kroh Angelika Krumbein 《Rapid communications in mass spectrometry : RCM》2010,24(14):2009-2022
Kale is a member of the Brassicaceae family and has a complex profile of flavonoid glycosides. Therefore, kale is a suitable matrix to discuss in a comprehensive study the different fragmentation patterns of flavonoid glycosides. The wide variety of glycosylation and acylation patterns determines the health‐promoting effects of these glycosides. The aim of this study is to investigate the naturally occurring flavonoids in kale. A total of 71 flavonoid glycosides of quercetin, kaempferol and isorhamnetin were identified using a high‐performance liquid chromatography diode‐array detection/electrospray ionization multi‐stage mass spectrometry (HPLC‐DAD/ESI‐MSn) method. Of these 71 flavonol glycosides, 27 were non‐acylated, 30 were monoacylated and 14 were diacylated. Non‐acylated flavonol glycosides were present as mono‐, di‐, tri‐ and tetraglycosides. This is the first time that the occurrence of four different fragmentation patterns of non‐acylated flavonol triglycosides has been reported in one matrix simultaneously. In addition, 44 flavonol glycosides were acylated with p‐coumaric, caffeic, ferulic, hydroxyferulic or sinapic acid. While monoacylated glycosides existed as di‐, tri‐ and tetraglycosides, diacylated glycosides occurred as tetra‐ and pentaglycosides. To the best of our knowledge, 28 compounds in kale are reported here for the first time. These include three acylated isorhamnetin glycosides (isorhamnetin‐3‐O‐sinapoyl‐sophoroside‐7‐O‐D‐glucoside, isorhamnetin‐3‐O‐feruloyl‐sophoroside‐7‐O‐diglucoside and isorhamnetin‐3‐O‐disinapoyl‐triglucoside‐7‐O‐diglucoside) and seven non‐acylated isorhamnetin glycosides. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
45.
Platinum is emitted to environment by automobile catalytic converters (ACCs), hospitals, noble metal refineries, and other industries. Due to abrasion of ACCs platinum leaves the cars with the exhaust fumes and can thus be found in urban and rural atmospheres. To study the exposure to this element its concentration in urine is determined. Urine represents an often used specimen for monitoring studies, as it plays an important role in the elimination of various substances from the body and in addition it can be collected easily. It is supposed that the Pt-intake depends on the physical activity of a person, i.e. the amount of air inhaled and food consumed. Therefore subjects without and with one or two hip-endoprostheses were selected for this monitoring study. The medians obtained for the Pt-concentration of the urine-samples of these three groups were 3.7 µg/g, 3.3 µg/g and 1.9 µg/g for persons with no, one and two prostheses, respectively. Applying a Mann-Whitney-U-test on these data leads to a p-value of 0.051 comparing the groups with n = 0 and n = 2, and a p-value of 0.052 for n = 1 and n = 2 (n = number of prostheses). 相似文献
46.
47.
Andrea Retzbach Joachim Marschall Marion Rahnke Lukas Otto Michaela Maier 《Journal of nanoparticle research》2011,13(12):6231-6244
In this article, we report data from an online questionnaire study with 587 respondents, representative for the adult U.S.
population in terms of age, gender, and level of education. The aim of this study was to assess how interest in science and
knowledge as well as beliefs about science are associated with risk and benefit perceptions of nanotechnology. The findings
suggest that the U.S. public is still rather unfamiliar with nanotechnology. Those who have some knowledge mainly have gotten
it from TV and the Internet. The content of current media reports is perceived as fairly positive. Knowledge of scientific
methods is unrelated to benefit and risk perceptions, at least when other predictors are controlled. In contrast, positive
beliefs about science (e.g., its impact on economy or health) and more sophisticated epistemological beliefs about the nature
of scientific knowledge are moderately linked to more positive perceptions of nanotechnology. The only exception is the perception
of scientific uncertainty: This is associated with less positive evaluations. Finally, higher engagement with science is associated
with higher risk perceptions. These findings show that laypersons who are engaged with science and who are aware of the inherent
uncertainty of scientific evidence might perceive nanotechnology in a somewhat more differentiated way, contrary to how it
is portrayed in the media today. 相似文献
48.
Benjamin J. Bythell Michaela Knapp-Mohammady Béla Paizs Alex G. Harrison 《Journal of the American Society for Mass Spectrometry》2010,21(8):1352-1363
The MSn spectra of the [M + H]+ and b 5 peaks derived from the peptides HAAAAA, AHAAAA, AAHAAA, AAAHAA, and AAAAHA have been measured, as have the spectra of the b 4 ions derived from the first four peptides. The MS2 spectra of the [M + H]+ ions show a substantial series of bn ions with enhanced cleavage at the amide bond C-terminal to His and substantial cleavage at the amide bond N-terminal to His (when there are at least two residues N-terminal to the His residue). There is compelling experimental and theoretical evidence for formation of nondirect sequence ions via cyclization/reopening chemistry in the CID spectra of the b tons when the His residue is near the C-terminus. The experimental evidence is less clear for ions when the His residue is near the N-terminus, although this may be due to the use of multiple alanine residues in the peptide making identifying scrambled peaks more difficult. The product ion mass spectra of the b 4 and b 5 ions from these isomeric peptides with cyclically permuted amino acid sequences are similar, but also show clear differences. This indicates less active cyclization/reopening followed by fragmentation of common structures for b n ions containing His than for sequences of solely aliphatic residues. Despite more energetically favorable cyclization barriers for the b 5 structures, the b 4 ions experimental data show more clear evidence of cyclization and sequence scrambling before fragmentation. For both b 4 and b 5 the energetically most favored structure is a macrocyclic isomer protonated at the His side chain. 相似文献
49.
50.