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71.
Suzuka Kinoshita Ryota Yamano Dr. Yu Shibata Yusuke Tanaka Kyoichi Hanada Dr. Takashi Matsumoto Prof. Dr. Kazunori Miyamoto Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Prof. Dr. Ken Tanaka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11113-11120
An S-shaped double helicene-like molecule (>99 % ee), possessing stable helical chirality, has been synthesized by the rhodium(I)/difluorphos complex-catalyzed highly diastereo- and enantioselective intramolecular double [2+2+2] cycloaddition of a 2-naphthol- and benzene-linked hexayne. The collision between two terminal naphthalene rings destabilizes the helical chirality of the S-shaped double helicene-like molecule, but the introduction of two additional fused benzene rings significantly increases the configurational stability. Thus, no epimerization and racemization were observed even at 100 °C. The enantiopure S-shaped double helicene-like molecule forms a trimer through the multiple C−H⋅⋅⋅π and C−H⋅⋅⋅O interactions in the solid-state. The trimers stack to form columnar packing structures, in which neighboring stacks have opposite dipole directions. The accumulation of helical structures in the same direction in the S-shaped double helicene-like molecule enhanced the chiroptical properties. 相似文献
72.
Masaki Kondo Junichiro Kanazawa Tomohiro Ichikawa Takumi Shimokawa Yuki Nagashima Kazunori Miyamoto Masanobu Uchiyama 《Angewandte Chemie (International ed. in English)》2020,59(5):1970-1974
The silaboration of [1.1.1]propellane enables direct introduction of B and Si functional groups onto the bicyclo[1.1.1]pentane (BCP) scaffold in high yield under mild, additive‐free conditions. The silaborated BCP can be obtained on a gram‐scale in a single step without the need for column‐chromatographic purification, and is storable and easy to handle, providing a versatile synthetic intermediate for BCP derivatives. We also describe various conversions of the C?B/C?Si bonds on the BCP scaffold, including development of a modified Suzuki–Miyaura cross‐coupling reaction at the highly sterically hindered bridgehead sp3 carbon center of the BCP skeleton using a combination of highly activated BCP boronic esters, copper(I) oxide, and a PdCl2(dppf) catalyst system. 相似文献
73.
Yuki Kataoka Naoya Kanbayashi Naoka Fujii Taka‐aki Okamura Takeharu Haino Kiyotaka Onitsuka 《Angewandte Chemie (International ed. in English)》2020,59(26):10286-10291
π‐Stacked polymers, which consist of layered π‐electron systems in a polymer, can be expected to be used in molecular electronic devices. However, the construction of a stable π‐stacked structure in a polymer is considerably challenging because it requires sophisticated designs and precise synthetic methods. Herein, we present a novel π‐stacked architecture based on poly(quinolylene‐2,3‐methylene) bearing alanine derivatives as the side chain, obtained through the living cyclo‐copolymerization of an o‐allenylaryl isocyanide. In the resulting polymer, the neighboring quinoline rings of the main chain form a layered structure with π–π interactions, which is stabilized by intramolecular hydrogen bonds. The vicinal quinoline units form two independent helices and the whole molecule is a twisted‐tape structure. This structure is established on the basis of UV/CD spectra, theoretical calculations, and atomic‐force microscopy. 相似文献
74.
Yulu Jiang Taro Ozaki Mei Harada Tadachika Miyasaka Hajime Sato Kazunori Miyamoto Junichiro Kanazawa Chengwei Liu Jun‐ichi Maruyama Masaatsu Adachi Atsuo Nakazaki Toshio Nishikawa Masanobu Uchiyama Atsushi Minami Hideaki Oikawa 《Angewandte Chemie (International ed. in English)》2020,59(41):17996-18002
Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome‐editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical‐induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue. 相似文献
75.
Yukio Nagasaki Kenji Kazama Eiichi Honzawa Masao Kato Kazunori Kataoka Teiji Tsuruta 《Macromolecular Symposia》1996,109(1):27-40
Reaction between dimethyldivinylsilane and 3,6-diazaoctane in the presence of 3-lithio-3,6-diazaoctane yields a new telechelic oligomer, poly(silamine), which consists of alternating 3,3-dimethyl-3-silapentane and N,N′-diethylethylenediamine units in the main chain. Poly(silamine) shows unique phase transition properties in response to the degree of protonation of amino groups in the polymer. Poly(silamine) also shows a strong interaction with several anions. Due to the interaction between poly(silamine) and anions along with the protonation of amino groups in the poly(silamine), the rubber elasticity of poly(silamine) is drastically changed. A discrete volume change can be observed when the environmental pH of the poly(silamine) gels is varied. This can be explained not only by a change in ionic osmotic pressure but also by a change in the rubber elasticity of the networks in the gel. 相似文献
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80.
Yoshiyuki Shirakawa Yusuke Hayashi Kazunori Kadota Hiroshi Mio Hiroto Ohtsuki Atsuko Shimosaka Jusuke Hidaka 《Journal of nanoparticle research》2008,10(4):577-584
In our previous paper, structural changes of selenium powders ground by a planetary ball mill at various rotational speeds
were investigated for the nanostructural modification of particles using mechanical grinding process. The experimental results
indicated that the amorphisation of Se by grinding accompanies lattice strain, and the lattice strain arises from impact energy
which is more than an energy related to intermolecular interaction. In this paper, molecular dynamics simulations of selenium
have been carried out under compressing conditions of various pressure strengths for obtaining information of the lattice
strain at atomic level. Then, dynamical behaviour of atomic configuration has been discussed in this process. The structural
disordering and formation of the structural defects were estimated by deviations of bond length and angle and the number of
created defects before and after compressing from simulated results. The disordering took place during compressing at various
pressure strengths, and the disordered atoms return to their initial positions at lower pressure. Stable disordered state
and defects after the compression can however remain by compression at more than a certain pressure strength mainly associated
with binding energy of selenium. 相似文献