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排序方式: 共有232条查询结果,搜索用时 15 毫秒
1.
Tuo Jiang Samuele Bordi Angus E. McMillan Kuang-Yen Chen Fumito Saito Paula L. Nichols Benedikt M. Wanner Jeffrey W. Bode 《Chemical science》2021,12(20):6977
The current laboratory practices of organic synthesis are labor intensive, impose safety and environmental hazards, and hamper the implementation of artificial intelligence guided drug discovery. Using a combination of reagent design, hardware engineering, and a simple operating system we provide an instrument capable of executing complex organic reactions with prepacked capsules. The machine conducts coupling reactions and delivers the purified products with minimal user involvement. Two desirable reaction classes – the synthesis of saturated N-heterocycles and reductive amination – were implemented, along with multi-step sequences that provide drug-like organic molecules in a fully automated manner. We envision that this system will serve as a console for developers to provide synthetic methods as integrated, user-friendly packages for conducting organic synthesis in a safe and convenient fashion.Using a combination of reagent design, hardware engineering, and a simple operating system we provide an instrument capable of executing complex organic reactions using prepacked capsules with minimal user involvement. 相似文献
2.
The unseeded non-hydrolytic sol-gel synthesis of ZrW2O8 and ZrMo2O8 produces trigonal ZrM2O8 (M = W, Mo) at 740 and 300–400°C, respectively. Cubic ZrW2O8 can be prepared using non-hydrolytic sol-gel methods by seeding with small amounts of preprepared cubic material, and the formation of the trigonal polymorph can be suppressed completely. Seeds with a small particle size are necessary for the preparation of cubic ZrW2O8. In contrast, seeding of ZrMo2O8 gels with either cubic ZrMo2O8 or cubic ZrW2O8 only lowers the temperature at which the trigonal phase crystallizes. 相似文献
3.
Shiow-Ching Chen Meei-Yun Shiue M.-H. Yang 《Analytical and bioanalytical chemistry》1997,357(8):1192-1197
A method is proposed which involves sample pretreatment followed by electrothermal atomic absorption spectrometry (ETAAS)
for determination of cadmium in human urine. A microwave digestion system was devised to accommodate double-closed vessels
for simultaneous digestion of batches of up to 24 urine samples in about 20 min. After digestion, matrix substances which
might interfere were removed using silica-immobilized 8-hydroxyquinoline (I-8HOQ) columns. The analyte adsorbed on the column
was then eluted with dilute nitric acid solution and determined by ETAAS using a fast temperature program. Neither ashing
steps in the furnace heating program nor use of matrix modifiers was necessary. The accuracy, precision, limit of detection,
and sample throughput of the method were evaluated. With meticulous control of systematic errors which may be introduced in
the pretreatment procedures, the present method can serve as a reference technique for the analysis of Cd in urine samples.
Received: 29 July 1996/Revised: 30 September 1996/Accepted: 13 October 1996 相似文献
4.
Shiow-Ching Chen Meei-Yun Shiue M.-H. Yang 《Fresenius' Journal of Analytical Chemistry》1997,357(8):1192-1197
A method is proposed which involves sample pretreatment followed by electrothermal atomic absorption spectrometry (ETAAS)
for determination of cadmium in human urine. A microwave digestion system was devised to accommodate double-closed vessels
for simultaneous digestion of batches of up to 24 urine samples in about 20 min. After digestion, matrix substances which
might interfere were removed using silica-immobilized 8-hydroxyquinoline (I-8HOQ) columns. The analyte adsorbed on the column
was then eluted with dilute nitric acid solution and determined by ETAAS using a fast temperature program. Neither ashing
steps in the furnace heating program nor use of matrix modifiers was necessary. The accuracy, precision, limit of detection,
and sample throughput of the method were evaluated. With meticulous control of systematic errors which may be introduced in
the pretreatment procedures, the present method can serve as a reference technique for the analysis of Cd in urine samples.
Received: 29 July 1996/Revised: 30 September 1996/Accepted: 13 October 1996 相似文献
5.
Photoirradiation of Os3(CO)10(C14H20) (1) in n-hexane produces the double-decker cluster [Os3(CO)9(C28H40)] [Os3(CO)10] (7), which can also be prepared from the reaction of Os3(CO)9(C28H40) (2) and Os3(CO)10(NCMe)2. Further reaction of 7 with Os3(CO)10(NCMe)2 affords the triple-decker cluster [Os3(CO)9(C28H40)][Os3(CO)10]2 (8). The bis(diyne) complex Os3(CO)8(C14H20)2 (3) reacts with Os3(CO)10(NCMe)2 sequentially to yield the double-decker cluster [Os3(CO)8(C14H20)2][Os3(CO)10] (4) and the triple-decker cluster [Os3(CO)8(C14H20)2][Os3(CO)10]2 (5). Treatment of 3 with Co2(CO)8 at room temperature leads to the mixed-metal triple-decker cluster [Os3(CO)8(C14H20)2][Co2(CO)6]2 (6), while the reaction of 2 and Co2(CO)8 produces [Os3(CO)9(C28H40)][Co2(CO)6]2 (9) and [Os2(CO)6(C28H40)][Co2(CO)6]2 (10). Compound 10, which involves cluster degradation from Os3 to Os2, has been structurally characterized by an X-ray diffraction study. 相似文献
6.
The electron impact mass spectra of eleven N-arylglycines and seven substituted aniline-N,N-diacetic acids were obtained under 70 eV and 14 eV ionization energies. The fragmentation patterns are similar to those of α-amino acids except for the degree of cleavage. The dehydration process of the diacetic acids may be considered as the characterestic process for this group of compounds. 相似文献
7.
From the hexane extractive of the wood of Pinus luchuensis Mayer, α-pinene, β-pinene, camphene, camphor, 4-terpineol, α-terpineol, carvacrol, tetracosanol, hexacosanol, octacosanol, β-sitosterol, stigmasterol, methyl dehydroabietate, pinosylvin monomethylether, pimaric acid, dehydroabietic acid and straight chain hydrocarbons C23-C35 were isolated. 相似文献
8.
Kim TH Moodycliffe AM Yarosh DB Norval M Kripke ML Ullrich SE 《Photochemistry and photobiology》2003,78(3):228-234
UV radiation suppresses the immune response, and UV-induced immune suppression contributes to UV-induced photocarcinogenesis. For UV-induced immune suppression to occur, electromagnetic energy (i.e. UV radiation) must be converted to a biological signal. Two photoreceptors have been identified in the skin that serves this purpose, epidermal DNA and trans-urocanic acid (UCA). Although compelling evidence exists to support a role for each pathway (UV-induced DNA damage or photoisomerization of UCA) in UV-induced immune suppression, it is not clear what determines which photoreceptor pathway is activated. To address this question, we injected UV-irradiated mice with a monoclonal antibody with specificity for cis-UCA or applied liposomes containing DNA repair enzymes to the skin of UV-irradiated mice. The effect that each had on UV-induced suppression of delayed-type hypersensitivity was measured. We asked whether the light source used (FS-40 sunlamps vs solar-simulated UV radiation) altered whichever pathway of immune suppression was activated. Different doses of UV radiation and the viability of the antigen were also considered. Neither the dose of UV nor the light source had any influence on determining which pathway was activated. Rather, we found that the viability of the antigen was the critical determinant. When live antigens were used, UV-induced immune suppression was blocked with monoclonal anti-cis-UCA but not with T4 endonuclease V-containing liposomes. The reverse was observed when formalin-fixed or killed antigens were used. Our findings indicate that antigen viability dictates which photoreceptor pathway predominates after UV exposure. 相似文献
9.
N-Bonded pentaamminecobalt(III) complexes of 2-cyanobenzamide, 2-cyanoacetamide, and fumaric, succinic, glutaric, and adipic amide-nitriles have been prepared. The kinetics of the base hydrolysis of (succinonitrile)pentaamminecobalt(III) have been measured: k(obsd) = k(OH) [OH(-)]; k(OH) = 1.23 x 10(3) {I = 1.00 M (NaCH(3)COO), 25 degrees C}. Amido-N-coordinated 2-cyanobenzamide cyclized in aqueous base, and it forms [(1-oxo-3-iminoisoindolino-endo-N)pentaamminecobalt(III). In aqueous acid it protonates on the exo-imine and solvolyzes (k(H) = 7.9 x 10(-)(5) s(-)(1)), forming the pentaammineaquacobalt(III) complex and 1-oxo-3-iminoisoindoline. In aqueous acid the amido-N complexes are protonated on the amide oxygen. The 2-cyanobenzamide species rearranges to form the nitrile-bonded linkage isomer in aqueous acid and also in Me(2)SO-d(6), while the succinic amide nitrile complex rearranges more slowly in aqueous acid to form solely the nitrile-bonded linkage isomer. The kinetics of the reaction were k(obsd) = f(k(H)[H(+)]/(K(a) + [H(+)])) where k(H) = 3.4 x 10(-)(4) M(-)(1) s(-)(1) and K(a) = 6.76 x 10(-)(2) M, pK(a) 1.2; pK(a) 1.3 (spectrophotometric) {I = 1.00 M (LiClO(4).3H(2)O), 25 degrees C}. In Me(2)SO-d(6) this amide-N complex reacts by three pathways: solvolysis, amide-N to -O isomerization, and amide-N to nitrile-bonded rearrangement (10%). The conjugate acid of the 2-cyanoacetamido-N complex reacted in both aqueous acid and acidified Me(2)SO-d(6) by solvolysis, amide N to O isomerization, and amide-N to nitrile-bonded rearrangement (17% in each solvent). The fumaric, glutaric, and adipic amide-nitrile complexes bonded through the amide nitrogen react only by solvolysis and amide-N to -O isomerization. Pentaamminecobalt(III) complexes of 2-cyanobenzamidine and succinic, glutaric, and adipic amidine-nitriles bonded through the amidine secondary nitrogen have been prepared. The 2-cyanobenzamidine complex undergoes rapid ligand cyclization to form the corresponding complex of 1,3-diiminoisoindoline bonded through the deprotonated endocyclic nitrogen. In aqueous acid the complex is protonated on one of the exo-imines, and this solvolyzes to form the pentaammineaquacobalt(III) complex and 1,3-diiminoisoindoline {k(H) = 1.7 x 10(-)(3) s(-)(1) (0.5 M HCl, 25 degrees C). Coordinated succinic amidine-nitrile also cyclizes in liquid ammonia to yield the complex of 2,5-diiminopyrrolidine bonded through the deprotonated endocyclic nitrogen. This is stable in aqueous base but solvolyzes rapidly (t(1/2) (s)) in aqueous acid to the aqua complex and succinimide; the latter is formed by hydrolysis of the free 2,5-diiminopyrrolidine. The dinuclear complex &mgr;-decaammine(succinonitrile)dicobalt(III) was synthesized; in aqueous base it forms &mgr;-(succinamido-N)decaamminecobalt(III). The dinuclear dinitrile complex reacts in liquid ammonia to form the corresponding succinic amidine-nitrile species which cyclizes rapidly to form &mgr;-decaammine(2,5-diiminopyrrolidino)cobalt(III) in which the ligand is bonded to cobalt(III) through the exo-imines. 相似文献
10.
Battersby BJ Lawrie GA Johnston AP Trau M 《Chemical communications (Cambridge, England)》2002,(14):1435-1441
The enormous amount of information generated through sequencing of the human genome has increased demands for more economical and flexible alternatives in genomics, proteomics and drug discovery. Many companies and institutions have recognised the potential of increasing the size and complexity of chemical libraries by producing large chemical libraries on colloidal support beads. Since colloid-based compounds in a suspension are randomly located, an encoding system such as optical barcoding is required to permit rapid elucidation of the compound structures. We describe in this article innovative methods for optical barcoding of colloids for use as support beads in both combinatorial and non-combinatorial libraries. We focus in particular on the difficult problem of barcoding extremely large libraries, which if solved, will transform the manner in which genomics, proteomics and drug discovery research is currently performed. 相似文献