全文获取类型
收费全文 | 943篇 |
免费 | 28篇 |
国内免费 | 5篇 |
专业分类
化学 | 793篇 |
晶体学 | 9篇 |
力学 | 6篇 |
数学 | 67篇 |
物理学 | 101篇 |
出版年
2023年 | 13篇 |
2022年 | 87篇 |
2021年 | 95篇 |
2020年 | 37篇 |
2019年 | 28篇 |
2018年 | 30篇 |
2017年 | 29篇 |
2016年 | 39篇 |
2015年 | 32篇 |
2014年 | 38篇 |
2013年 | 72篇 |
2012年 | 49篇 |
2011年 | 73篇 |
2010年 | 30篇 |
2009年 | 45篇 |
2008年 | 48篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1991年 | 6篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1960年 | 2篇 |
1943年 | 1篇 |
1941年 | 1篇 |
1935年 | 2篇 |
1930年 | 2篇 |
1929年 | 1篇 |
1922年 | 1篇 |
1918年 | 1篇 |
排序方式: 共有976条查询结果,搜索用时 0 毫秒
11.
D. KieΒling 《Colloid and polymer science》1961,176(2):119-128
Ohne Zusammenfassung
Herrn Prof. Dr.W. Holzmütter danke ich für sein stetes Interesse an dieser Arbeit und seine wertvollen Ratschl?ge. Au\erdem bin ich Herrn Dr.G. Geppert und seiner Mitarbeiterin, Frl.C. Roth, für die Unterstützung beim Aufnehmen der Ultrarotspektren zu Dank verpflichtet. Für die überlassung von Probematerial m?chte
ich folgenden Firmen danken: Eilenburger Celluloidwerk, Chemische Werke Buna, Badische Anilin- & Sodafabriken, Ludwigshafen,
Kalle & Co., Wiesbaden. 相似文献
12.
Korolczuk M Moroziewicz A Grabarczyk M 《Analytical and bioanalytical chemistry》2005,382(7):1678-1682
Procedures for trace cobalt determinations by adsorptive stripping voltammetry at in situ and ex situ plated bismuth film electrodes are presented. These exploit the enhancement of the cobalt peak obtained by using the Co(II)–dimethylglyoxime–cetyltrimethylammonium bromide–piperazine-N,N-bis(2-ethanesulfonic acid) system. The calibration graph for an accumulation time of 120 s was linear from 2 × 10–10 to 2 × 10–8 mol L–1. The relative standard deviation from five determinations of cobalt at a concentration of 5 × 10–9 mol L–1 was 5.2%. The detection limit for an accumulation time of 300 s was 1.8 × 10–11 mol L–1. The proposed procedure was applied to cobalt determination in certified reference materials and in tap and river water samples. 相似文献
13.
Aleksandra Gasperowicz Wodzimierz askawski 《Journal of polymer science. Part A, Polymer chemistry》1976,14(12):2875-2886
The grafting of styrene onto low molecular weight polybutadienes and butadiene–styrene co-polymers was studied. A mathematical method was used for the design of experiments and for the determination of the optimum grafting conditions with respect to the conversion of styrene and the efficiency of grafting. The reaction parameters were temperature (65–105°C), time (2–10 hr), concentration of the initiator, polymer to monomer ratio (10/90–90/10) and dilution by solvent (toluene). The optimum grafting conditions were chosen under which 50–60 wt-% of styrene was grafted onto backbone polymer at a high conversion of the monomer. It was found that the reactions producing graft copolymer prevailed over the styrene homopolymerization when the temperatures employed were lower (65–85°C), and the reaction time (8–10 hr), backbone polymer/monomer ratio, and the dilution by solvent were higher. The efficiency, density, and degree of grafting were found to increase with the increase in the molecular weight of the backbone polymer. The efficiencies and densities of grafting onto low molecular weight polybutedienes were higher than those of grafting onto low molecular weight butadiene–styrene copolymers. Grafting efficiencies and grafting densities were in the ranges 37.8–61.6 wt % and 0.06–0.26, respectively, in the studied range of number-average molecular weights (M?n = 2400–6000). 相似文献
14.
Dagmara Jacewicz Agnieszka Łapińska Aleksandra Dąbrowska Lech Chmurzyński 《Transition Metal Chemistry》2006,31(1):111-117
The kinetics of the reaction between gaseous CO2 and the cis-[Cr(phen)2(OH2)2]3+ ion leading to the formation of the carbonato complex ion, have been studied over the pH and temperature ranges: 3 < pH <
6 and 5 < T < 25 °C, respectively, at a constant ionic strength of 1 m (NaClO4). Investigations were carried out using the stopped-flow spectrophotometry technique in the UV–Vis range: 340–700 nm. The
major reactant species in the pH range studied was cis-[Cr(phen)2(OH)(OH2)]2+ ion, which underwent reaction with CO2 to form cis-[Cr(phen)2(OH2)(HCO3)]2+ ion. Subsequently, slower ring closure of the latter species to form the bidentate carbonato chelate was observed. The possible
mechanism has been discussed and the activation parameters ΔH† and ΔS† were also determined for the reaction studied. 相似文献
15.
Snezana S.?MiticEmail author Gordana Z.?Miletic Aleksandra N.?Pavlovic Snezana B.?Tosic 《Monatshefte für Chemie / Chemical Monthly》2004,135(8):927-936
Summary. A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of chromium (VI). The method is based on the catalytic effect of Cr(VI) on the reaction of sodium pyrogallol-5-sulphonate (PS) with hydrogen peroxide. The reaction is followed spectrophotometrically by tracing the oxidation product at 437nm within 1min after addition of H2O2. The optimum reaction conditions are PS (1.32·10–3mol·dm–3), H2O2 (0.32mol·dm–3), HClO4 (2.6·10–3mol·dm–3) at 25°C. Following this procedure, chromium (VI) can be determined with a linear calibration graph up to 0.25ng·cm–3 and a detection limit of 0.024ng·cm–3, based on the 3 criterion. The interference effect of several species was also investigated and it was found that the most common cations and anions do not interfere with the determination. The developed procedure was successfully applied to the determination of Cr(VI) and total Cr in river waters and total Cr in herbal samples. 相似文献
16.
Aleksandra Drzewiecka Krystyna Stepniak Anna Barcicka Anna E. Koziol 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(8):m346-m348
The asymmetric unit in the title compound, {[Cd2(C4H4O6)(SO4)(H2O)5]·3H2O}n, is composed of two cadmium cations, one (R,R)‐tartrate and one sulfate anion, five aqua ligands and three solvent water molecules. One of the cadmium ions is coordinated in an octahedral environment, whereas the second is surrounded by seven O atoms in a pentagonal–bipyramidal geometry. Both types of coordination polyhedra form two sets of perpendicular non‐intersecting polymeric chains. CdO6 octahedra share two corners, while CdO7 units are joined by a bridging carboxylate group. An extensive hydrogen‐bond pattern involving all of the OH groups contributes to the stabilization of the structure. 相似文献
17.
Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter
can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated
polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis
was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact
mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes
(ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times
and mass spectra.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
18.
Nesković OM Veljković MV Velicković SR Petkovska LT Perić-Grujić AA 《Rapid communications in mass spectrometry : RCM》2003,17(3):212-214
Ionization energies of hypervalent Li(2)F, Li(2)Cl and Na(2)Cl molecules detected by surface ionization electron impact neutralization mass spectrometry are reported. The ionization energies were 3.78 +/- 0.2 eV for Li(2)F, 4.93 +/- 0.2 eV for Li(2)Cl, and 4.21 +/- 0.2 eV for Na(2)Cl. The ionization energies (IE) agree with theoretical ionization energies calculated by ab initio methods, supporting the theoretical prediction that Li(2)F has a hyperlithiated configuration in which the odd electron delocalizes over the two lithiums and with photoionization measurement. The first ionization energy of Na(2)Cl was experimentally confirmed earlier and for Li(2)Cl as well.8 We have developed and used this new approach for the problem--in the present work ions were first formed by surface ionization, followed by electron attachment (neutralization). 相似文献
19.
Frontera A Saczewski F Gdaniec M Dziemidowicz-Borys E Kurland A Deyà PM Quiñonero D Garau C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6560-6567
Several structures of pi complexes of isocyanuric acid and of several thio derivatives with anions have been computed by using high level ab initio calculations. The nature of the complexes has been studied by means of the method of molecular interaction potential with polarization (MIPp) and Bader's theory of atoms-in-molecules. These molecules form favorable complexes with anions and can be used as binding units for building receptors for the molecular recognition of anions. In several cases, the anion-pi interaction has been demonstrated experimentally by means of X-ray crystallography. 相似文献
20.
Amber L. H. Gray Aleksandra Antevska Benjamin A. Link Bryan Bogin Susan J. Burke Samuel D. Dupuy J. Jason Collier Zachary A. Levine Michael D. Karlstad Thanh D. Do 《Chemical science》2021,12(16):5853
Despite being relatively benign and not an indicative signature of toxicity, fibril formation and fibrillar structures continue to be key factors in assessing the structure–function relationship in protein aggregation diseases. The inability to capture molecular cross-talk among key players at the tissue level before fibril formation greatly accounts for the missing link toward the development of an efficacious therapeutic intervention for Type II diabetes mellitus (T2DM). We show that human α-calcitonin gene-related peptide (α-CGRP) remodeled amylin fibrillization. Furthermore, while CGRP and/or amylin monomers reduce the secretion of both mouse Ins1 and Ins2 proteins, CGRP oligomers have a reverse effect on Ins1. Genetically reduced Ins2, the orthologous version of human insulin, has been shown to enhance insulin sensitivity and extend the life-span in old female mice. Beyond the mechanistic insights, our data suggest that CGRP regulates insulin secretion and lowers the risk of T2DM. Our result rationalizes how migraine might be protective against T2DM. We envision the new paradigm of CGRP : amylin interactions as a pivotal aspect for T2DM diagnostics and therapeutics. Maintaining a low level of amylin while increasing the level of CGRP could become a viable approach toward T2DM prevention and treatment.CGRP concentration is elevated in migraine conditions. The protective effect of migraine against type 2 diabetes is attributed to the ability of CGRP to remodel human amylin aggregation and to suppress the secretion of mouse insulin 2 (the orthologue of human insulin). 相似文献