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921.
Disulfide cross-linked oligonucleotides for connecting two DNA double helixes have been designed, synthesized, and characterized. Employing these cross-linked oligonucleotides, two double helixes can be arranged side by side, and the orientations can be controlled both in parallel and antiparallel ways by addition of a specific complementary DNA strand. 相似文献
922.
Tao J Morikawa T Ando S Matsuda H Yoshikawa M 《Chemical & pharmaceutical bulletin》2003,51(6):654-662
Three new arborinane-type triterpene glycosides, rubianosides II, III, and IV, a new arborinane-type triterpene, rubianol-g, and a new anthraquinone, rubianthraquinone, were isolated from a Chinese natural medicine, the roots of Rubia yunnanensis. The structures of the new constituents including their absolute configurations were determined on the basis of chemical and physicochemical evidence. The inhibitory effects of the isolated constituents on nitric oxide production in lipopolysaccharide-activated macrophages were examined. Among them, a cyclic peptide constituent, RA-XII and its aglycon, RA-V (deoxybouvadin), potently inhibited overproduction of nitric oxide and induction of inducible nitric oxide synthase. In addition, an anthraquinone constituent, 2-methyl-1,3,6-trihydroxy-9,10-anthraquinone, was found to show inhibitory effects on the release of beta-hexosaminidase in RBL-2H3 cells. 相似文献
923.
Ordered mesoporous phosphosilicate glass electrolyte film exhibiting low area specific resistivity (ASR) compared with those of Nafion has been synthesized using non-ionic surfactant as the structure-directing agent. 相似文献
924.
Catalytic reactions in two liquid phases containing ionic liquids (ILs), in which organic reactions proceed in the ILs phase and products are extracted to the other liquid phase, are efficient and environmentally benign. This short review briefly reports the development of catalytic application in biphasic systems containing ILs in the last two years. Recent progress for the functionalization of ILs themselves and combinations of homogeneous and heterogeneous catalysts with ILs are described. Prospects and future challenges are also addressed. 相似文献
925.
Design and Synthesis of a Berberine Dimer: A Fluorescent Ligand with High Affinity towards G‐Quadruplexes 下载免费PDF全文
926.
In Vivo Spectrum of UVC‐induced Mutation in Mouse Skin Epidermis May Reflect the Cytosine Deamination Propensity of Cyclobutane Pyrimidine Dimers 下载免费PDF全文
Hironobu Ikehata Toshio Mori Masayuki Yamamoto 《Photochemistry and photobiology》2015,91(6):1488-1496
Although ultraviolet radiation (UVR) has a genotoxicity for inducing skin cancers, the skin may tolerate UVC component because the epidermal layer prevents this short wavelength range from passing through. Here, UVC genotoxicity for mouse skin was evaluated in terms of DNA damage formation and mutagenicity. UVC induced UVR photolesions and mutations remarkably in the epidermis but poorly in the dermis, confirming the barrier ability of the epidermis against shorter UVR wavelengths. Moreover, the epidermis itself responded to UVC mutagenicity with mutation induction suppression, which suppressed the mutant frequencies to a remarkably low, constant level regardless of UVC dose. The mutation spectrum observed in UVC‐exposed epidermis showed a predominance of UV‐signature mutation, which occurred frequently in 5′‐TCG‐3′, 5′‐TCA‐3′ and 5′‐CCA‐3′ contexts. Especially, for the former two contexts, the mutations recurred at several sites with more remarkable recurrences at the 5′‐TCG‐3′ sites. Comparison of the UVC mutation spectrum with those observed in longer UVR wavelength ranges led us to a mechanism that explains why the sequence context preference of UV‐signature mutation changes according to the wavelength, which is based on the difference in the mCpG preference of cyclobutane pyrimidine dimer (CPD) formation among UVR ranges and the sequence context‐dependent cytosine deamination propensity of CPD. 相似文献
927.
Minoru Ozeki Honoka Egawa Toshiki Takano Hideki Mizutani Narumi Yasuda Kenji Arimitsu Tetsuya Kajimoto Shinzo Hosoi Hiroki Iwasaki Naoto Kojima Manabu Node Masayuki Yamashita 《Tetrahedron》2017,73(15):2014-2021
A practical method for the synthesis of chiral β2,3-amino esters having various substituents was developed, which is characterized by an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. We found that a highly face-selective protonation occurred by the quick addition of water to the enolate intermediate derived from the Michael addition reaction to afford N-protected β2,3-amino esters in moderate to excellent yields. This finding was made possible by the facile preparation of geometrically pure trisubstituted (E)-α,β-unsaturated esters, which was established recently by our group. The subsequent deprotection of the amino group in the Michael adduct by using N-iodosuccinimide (NIS) efficiently provided β2,3-amino esters having various substituents. 相似文献
928.
Takuya Matsumoto Naoto Kojima Akinobu Akatsuka Takao Yamori Shingo Dan Hiroki Iwasaki Masayuki Yamashita 《Tetrahedron》2017,73(17):2359-2366
The convergent synthesis of thiophene-3-carboxamide analogues of annonaceous acetogenins was accomplished through the asymmetric alkynylation of a 2-formyl THF ring fragment with an alkyne having a thiophene ring as the key step. Eight stereoisomers of the THF ring moiety were synthesized by this convergent route and their antiproliferative activities against 39 human cancer cell lines were evaluated. It was revealed that derivatives having the threo configuration between C17–C18 positions showed more potent activities than the corresponding erythro ones. 相似文献
929.
Dr. Chengjun Pan Chunhui Zhao Prof. Dr. Masayuki Takeuchi Dr. Kazunori Sugiyasu 《化学:亚洲杂志》2015,10(9):1820-1835
Conjugated polymers (CPs) are often referred to as molecular wires because of their quasi one‐dimensional electronic wavefunctions delocalized along the polymer chains. However, in the solid state, CPs tend to self‐assemble through π‐stacking, which greatly attenuates the one‐dimensional nature. By molecular design, CPs can be molecularly insulated just like electric power cords, resulting in so‐called “insulated” molecular wires (IMWs). In this Focus Review, we will discuss their unique photophysical, electronic, and mechanical properties which originate from the absence of π‐stacking. 相似文献
930.
Dr. Ayuko Meguro Yudai Motoyoshi Kazuya Teramoto Shota Ueda Yusuke Totsuka Yumi Ando Dr. Takeo Tomita Dr. Seung‐Young Kim Dr. Tomoyuki Kimura Dr. Masayuki Igarashi Dr. Ryuichi Sawa Prof. Dr. Tetsuro Shinada Prof. Dr. Makoto Nishiyama Prof. Dr. Tomohisa Kuzuyama 《Angewandte Chemie (International ed. in English)》2015,54(14):4353-4356
Terpene cyclization reactions are fascinating owing to the precise control of connectivity and stereochemistry during the catalytic process. Cyclooctat‐9‐en‐7‐ol synthase (CotB2) synthesizes an unusual 5‐8‐5 fused‐ring structure with six chiral centers from the universal diterpene precursor, the achiral C20 geranylgeranyl diphosphate substrate. An unusual new mechanism for the exquisite CotB2‐catalyzed cyclization that involves a carbon–carbon backbone rearrangement and three long‐range hydride shifts is proposed, based on a powerful combination of in vivo studies using uniformly 13C‐labeled glucose and in vitro reactions of regiospecifically deuterium‐substituted geranylgeranyl diphosphate substrates. This study shows that CotB2 elegantly demonstrates the synthetic virtuosity and stereochemical control that evolution has conferred on terpene synthases. 相似文献