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441.
Y. Nakata M. Tamaki T. Hashimoto 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):433-438
Red-thermoluminescence (RTL) dating was applied to quartz grains from a flat roof-tile of “Shin-Yakushiji” temple, Nara, built
in Japan, probably 1258 years ago. Based on overlapping patterns with other roof-tiles, one flat roof-tile was separated into
several zones. The equivalent doses were accurately evaluated to be 4.4–5.1 Gy for each zone. The evaluation of annual doses
has been done under the consideration of overlapped numbers of roof-tiles and soil layers under the roof-tiles. Evaluated
RTL ages were in good agreement with the construction date of the temple. The present evaluated age was the youngest one within
several ages we previously have been deduced from the RTL dating. 相似文献
442.
We developed an automatic kidney detection procedure designed to do away with extraneous margins such as the liver or spleen while leaving the kidney margins intact using Laplacian operations and concurrence calculations. We evaluated the detectability of kidneys using our procedures and found that the renal margins were successfully detected in 84 cases of 100 subjects (84%) including 176 kidneys out of a total of 198 kidneys (89%). It was shown that as the renal function decreased the detectability of the renal margin decreased. In eight cases (16 kidneys) out of 9 patients who later resultantly received hemodialysis even manual settings of the renal ROI were very difficult. After excluding these 8 cases the detectability was 92% for all the cases and 95% for the kidneys. It was our conclusion that this method is sufficient for clinical application. 相似文献
443.
[structure: see text] The total synthesis of acetogenin 1 reported for pyragonicin and its 10-epimer 32 is described. The common THP ring system was stereoselectively constructed through a SmI(2)-induced reductive cyclization of beta-alkoxy acrylate 5 followed by Mitsunobu inversion, and each chiral center at C-10 was created by Brown's asymmetric allylation. Compound 1 had spectroscopic data consistent with that of natural pyragonicin, but a different optical rotation. 相似文献
444.
Nagase T Nakata E Shinkai S Hamachi I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3660-3669
A new general method, post-photoaffinity-labeling modification (PPALM), for constructing fluorescent saccharide biosensors based on naturally occurring saccharide-binding proteins, lectins, is described in detail. An active-site-directed incorporation of a masked reactive site into a lectin was conducted by using a photoaffinity labeling technique followed by demasking and then chemical modification to yield a fluorescent lectin. Two photoaffinity labeling reagents were designed and synthesized in this study. The labeling reagent with a photoreactive site appended through a disulfide link to a mannoside unit was bound to the saccharide-binding pocket of the lectin concanavalin A (Con A). After light irradiation, the mannoside unit was cleaved by reduction. The unique thiol group thus produced was site-specifically modified with various fluorescent groups (dansyl, coumarin, or dimethylaminobenzoate derivatives) to afford fluorescent Con As. The labeling site was characterized by protease-catalyzed digestion followed by HPLC, MALDI-TOF MS, and tandem mass-mass spectrometry; these methods indicated that the photolabeling step is remarkably site specific. Strong fluorescence was observed in the engineered Con A with a fluorophore, and the emission changed sensitively upon saccharide complexation. The binding constants for various saccharides were determined by fluorescence titration and demonstrated that the binding selectivity and affinity of the engineered Con As are comparable to those of native Con A. The red shift of the emission maximum, the decrease in the fluorescence anisotropy of the dansyl unit, and the increase in the twisted intramolecular charge transfer emission caused by sugar binding to the engineered Con A explicitly indicate that the microenvironment of the appended fluorophores changes from a restricted and relatively hydrophobic environment into a rather freely mobile and hydrophilic environment. 相似文献
445.
The C-3 C-11 segment
of (+)-aplasmomycin was synthesized stereoselectively starting from (+)-pantolactone (
) and the C-3 C-17 segment
was synthesized via coupling of
and
. 相似文献
446.
Yoshiyuki Oishi Shoichi Nakata Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):933-938
New poly(ether sulfone)-polyimide block copolymers were synthesized from α,ω-diamineterminated poly(ether sulfone) oligomer, aromatic diamines, and aromatic tetracarboxylic dianhydrides by low-temperature solution polymerization and subsequent thermal imidization. The block copolymers were insoluble in organic solvents. The multiblock copolymers obtained by the two-pot method showed microphase separation, while the random block copolymers by the one-pot method had single phase morphology. The mechanical properties of the block copolymers were greatly improved by the introduction of polyimide into the poly(ether sulfone). © 1993 John Wiley & Sons, Inc. 相似文献
447.
Reactive molecular dynamics (MD) simulation is performed using a reactive force field (ReaxFF). To this end, we developed a new method to optimize the ReaxFF parameters based on a machine learning approach. This approach combines the k-nearest neighbor and random forest regressor algorithm to efficiently locate several possible ReaxFF parameter sets. As a pilot test of the developed approach, the optimized ReaxFF parameter set was applied to perform chemical vapor deposition (CVD) of an α-Al2O3 crystal. The crystal structure of α-Al2O3 was reasonably reproduced even at a relatively high temperature (2000 K). The reactive MD simulation suggests that the (110) surface grows faster than the (0001) surface, indicating that the developed parameter optimization technique could be used for understanding the chemical reaction in the CVD process. © 2019 Wiley Periodicals, Inc. 相似文献
448.
S. Ueda K. Kondo J. Inaba H. Kutsukake K. Nakata 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):261-273
Summary In
order to evaluate the transport of 3H and 137Cs
radionuclides in semi-closed brackish Lake Obuchi, Japan, bordered by nuclear
fuel cycling facilities, a 3D-lower-trophic eco-hydrodynamic model has been
developed and validated. In a short-term prediction, 3H and 137Cs
activity levels in water should be in an agreement with field measurements. It
became clear that the results depended on the mixing of fresh water and
seawater in the model. Moreover, a short-term simulation estimated that most 3H
and 137Cs flowed to the ocean rather than remaining in the lake.
Based on calculations over the past 50 years, a peak of 137Cs in
sediment was in 1963, when the maximum 137Cs fallout was observed.
The calculation showed a rapid decrease after that peak, however, the field
measurement data gradually declined. This suggested that the process by which 137Cs
accumulated from the watershed to the lake was actually slower in the field
than in the model calculations. The model may be successfully applied to a
variety of different environmental situations as a generic tool for evaluating
the concentration and migration of 3H and 137Cs in a
brackish lake.</p>
</p> 相似文献
449.
Yoshiyuki Oishi Shoichi Nakata Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1111-1117
New poly(ether sulfone)–aramid block copolymers were synthesized from an α, ω-diamineterminated poly(ether sulfone) oligomer, aromatic diamines, and aromatic dicarboxylic acid chlorides by the low-temperature solution polycondensation in N-methyl-2-pyrrolidone. By the introduction of aramid into the poly(ether sulfone), the glass transition temperatures of the block copolymers rose and the mechanical properties were significantly improved. Microphase separation, which often takes place in many block copolymers, did not occur in the present block copolymers. © 1993 John Wiley & Sons, Inc. 相似文献
450.
Eiji Nakata Hisaaki Hirose Khongorzul Gerelbaatar Jan Vincent V. Arafiles Zhengxiao Zhang Shiroh Futaki Takashi Morii 《Chemical science》2021,12(23):8231
Realtime monitoring of the cellular environment, such as the intracellular pH, in a defined cellular space provides a comprehensive understanding of the dynamics processes in a living cell. Considering the limitation of spatial resolution in conventional microscopy measurements, multiple types of fluorophores assembled within that space would behave as a single fluorescent probe molecule. Such a character of microscopic measurements enables a much more flexible combinatorial design strategy in developing fluorescent probes for given targets. Nanomaterials with sizes smaller than the microscopy spatial resolution provide a scaffold to assemble several types of fluorophores with a variety of optical characteristics, therefore providing a convenient strategy for designing fluorescent pH sensors. In this study, fluorescein (CF) and tetramethylrhodamine (CR) were assembled on a DNA nanostructure with controlling the number of each type of fluorophore. By taking advantage of the different responses of CF and CR emissions to the pH environment, an appropriate assembly of both CF and CR on DNA origami enabled a controlled intensity of fluorescence emission and ratiometric pH monitoring within the space defined by DNA origami. The CF and CR-assembled DNA origami was successfully applied for monitoring the intracellular pH changes.A combinatorial assembly of two types of intensity-based fluorophores on a DNA nanostructure provided a ratiometric pH probe with high emission intensity for monitoring intracellular pH changes. 相似文献