全文获取类型
收费全文 | 845篇 |
免费 | 35篇 |
国内免费 | 1篇 |
专业分类
化学 | 564篇 |
晶体学 | 3篇 |
力学 | 20篇 |
数学 | 156篇 |
物理学 | 138篇 |
出版年
2023年 | 13篇 |
2022年 | 14篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 19篇 |
2014年 | 18篇 |
2013年 | 50篇 |
2012年 | 50篇 |
2011年 | 55篇 |
2010年 | 31篇 |
2009年 | 33篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 42篇 |
2005年 | 38篇 |
2004年 | 44篇 |
2003年 | 34篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 19篇 |
1995年 | 7篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1957年 | 3篇 |
1956年 | 3篇 |
排序方式: 共有881条查询结果,搜索用时 15 毫秒
181.
Pierre Braunstein Chantal Charles Richard D. Adams Ralph Layland 《Journal of Cluster Science》1996,7(2):145-154
The reaction of the siloxyl containing ferrate [Fe(CO)3(
1-dppm){Si(OMe)3}]–,1 (dppm = Ph2PCH2PPh2) with Sn(OAc)2(n-Bu)2 has yielded the new dimeric complex [Fe(CO)3(
1-dppm){µ-Sn(n-Bu)2}]2, 3 in 89% yield. Compound3 was characterized crystallographically and was found to be a centrosym-etrical molecule with a rhomboidal Fe2Sn2 cluster at the center. Each iron atom contains me
1-dppm ligand. Compound3 was found to react with [Pd(dmba) (µ-Cl)]2 (dmba=dimethylbenzylamine) to yield the new complexmer-[Fe(CO)3{Sn(n-Bu)2}(µ-dppm)Pd(dmba)Cl]2, 4 by attachment of a palla-dium grouping to each of the uncoordinated phosphorus atoms in 3. Crystal data for 3: space groupP
,a=11.399(2) Å, 6=15.98(3) Å, c=10.869(3) Å, =94.10(2)°.=100.56(2)°, =69.35(1)°,Z=2, 3533 reflections,R=0.034. 相似文献
182.
Hermann Schmid Günther Bauer Georg Prähauser 《Monatshefte für Chemie / Chemical Monthly》1967,98(1):165-168
The free enthalpy of activation, the enthalpy of activation and the entropy of activation of the deuterium ion catalysis of the mutarotation of α-glucose in deuterium oxide have been determined and compared with those of the deuterium oxide catalysis; furthermore they have been compared with the corresponding values of the hydrogen ion catalysis and of the water catalysis and the mechanism of activation of the studied catalysis has been elucidated. 相似文献
183.
184.
L. Jaroškoá L'. Fišera I. Matejková P. Ertl N. Prónayová 《Monatshefte für Chemie / Chemical Monthly》1994,125(12):1413-1425
Summary The stereoselectivity of the nitrone cycloaddition with 1-substituted 3,3-methylene-5,5-dimethyl-2-pyrrolidinones1 is discussed. C,N-Diarylnitrones give mixtures of diastereomeric spirocycloadducts3 and4, in which3 always dominates. In contrast, N-methylnitrones react under the formation of4 as major products. Cycloaddition of C-benzoyl nitrones7 with1 affords exclusively single isoxazolidines8. Semi-empirical quantum mechanical methods (AM1) were used to rationalize the regio- and stereoselectivity of the reactions.
Stereoselektivität der 1,3-dipolaren Cycloaddition von Nitronen an 1-substituierte 3,3-Methylen-5,5-dimethyl-2-pyrrolidinone
Zusammenfassung Die Stereoselektivität der Cycloaddition von Nitronen mit 1-substituierten 3,3-Methylen-5,5-dimethyl-pyrrolidinonen (1) wird diskutiert. C,N-Diarylnitrone ergeben Mischungen der diastereomeren Spirocycloaddukte3 und4, wobei3 immer überwiegt. Im Gegensatz dazu entsteht bei der Reaktion von N-Methylnitronen4 als Hauptprodukt. Die Cycloaddition von C-Benzoylnitronen (7) mit1 liefert ausschließlich Isoxazolidine vom Typ8. Zum besseren Verständnis der Regio- und Stereoselektivität der Reaktionen wurden semiempirische quantenmechanische Berechnungen (AM1) durchgeführt.相似文献
185.
Application of capillary electrophoresis (CE) as a high-resolution separation technique in metalloproteomics research is critically
reviewed. The focus is on the requirements and challenges involved in coupling CE to sensitive element and molecule-specific
detection techniques such as inductively coupled plasma mass spectrometry (ICP–MS) or electrospray ionisation mass spectrometry
(ESI–MS). The complementary application of both detection techniques to the structural and functional characterisation of
metal-binding proteins and their structural metal-binding moieties is emphasised. Beneficial aspects and limitations of mass
spectrometry hyphenated to CE are discussed, on the basis of the literature published in this field over the last decade.
Recent metalloproteomics applications of CE are reviewed to demonstrate its potential and limitations in modern biochemical
speciation analysis and to indicate future directions of this technique. 相似文献
186.
Goudreau N Brochu C Cameron DR Duceppe JS Faucher AM Ferland JM Grand-Maître C Poirier M Simoneau B Tsantrizos YS 《The Journal of organic chemistry》2004,69(19):6185-6201
The virally encoded NS3 protease is essential to the life cycle of the hepatitis C virus (HCV), an important human pathogen causing chronic hepatitis, cirrhosis of the liver, and hepatocellular carcinoma. The design and synthesis of 15-membered ring beta-strand mimics which are capable of inhibiting the interactions between the HCV NS3 protease enzyme and its polyprotein substrate will be described. The binding interactions between a macrocyclic ligand and the enzyme were explored by NMR and molecular dynamics, and a model of the ligand/enzyme complex was developed. 相似文献
187.
Friedbert Prüfer 《Annals of Global Analysis and Geometry》1985,3(2):129-154
In this paper we study some relations between the spectrum and the lengths of the closed geodesics of a Riemannian manifold of positive constant sectional curvature 1. Our topic is the development of a Poisson formula for such space forms. Further we obtain explicit results for the lengths of the closed geodesics. We conclude the paper with a result concerning the singular support of the distribution
, where the sum runs through all spec(M). 相似文献
188.
Comparative Analysis of Conjugated Alkynyl Chromophore–Triazacyclononane Ligands for Sensitized Emission of Europium and Terbium 下载免费PDF全文
Marine Soulié Frédéric Latzko Emmanuel Bourrier Dr. Virginie Placide Dr. Stephen J. Butler Dr. Robert Pal Dr. James W. Walton Dr. Patrice L. Baldeck Dr. Boris Le Guennic Dr. Chantal Andraud Dr. Jurriaan M. Zwier Dr. Laurent Lamarque Prof. David Parker Dr. Olivier Maury 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8636-8646
A series of europium and terbium complexes based on a functionalized triazacyclononane carboxylate or phosphinate macrocyclic ligand is described. The influence of the anionic group, that is, carboxylate, methylphosphinate, or phenylphosphinate, on the photophysical properties was studied and rationalized on the basis of DFT calculated structures. The nature, number, and position of electron‐donating or electron‐withdrawing aryl substituents were varied systematically within the same phenylethynyl scaffold in order to optimize the brightness of the corresponding europium complexes and investigate their two‐photon absorption properties. Finally, the europium complexes were examined in cell‐imaging applications, and selected terbium complexes were studied as potential oxygen sensors. 相似文献
189.
Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium 下载免费PDF全文
Dr. Justin N. Cross Dr. Joseph A. Macor Dr. Jeffery A. Bertke Dr. Maryline G. Ferrier Dr. Gregory S. Girolami Dr. Stosh A. Kozimor Joel R. Maassen Dr. Brian L. Scott Dr. David K. Shuh Dr. Benjamin W. Stein Prof. Dr. S. Chantal E. Stieber 《Angewandte Chemie (International ed. in English)》2016,55(41):12755-12759
Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear‐fuel cycles. Herein, we describe the preparation of (NBu4)Am[S2P(tBu2C12H6)]4 and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., NdIII) and an isoelectronic one (EuIII). The results include the first measurement of an Am?S bond length, with a mean value of 2.921(9) Å, by single‐crystal X‐ray diffraction. Comparison with the EuIII and NdIII complexes revealed subtle electronic differences between the complexes of AmIII and the lanthanides. 相似文献
190.
Touahir L Galopin E Boukherroub R Gouget-Laemmel AC Chazalviel JN Ozanam F Saison O Akjouj A Pennec Y Djafari-Rouhani B Szunerits S 《The Analyst》2011,136(9):1859-1866
The use of an amorphous silicon-carbon alloy overcoating on silver nanostructures in a localized surface plasmon resonance (LSPR) sensing platform allows for decreasing the detection limit by an order of magnitude as compared to sensors based on gold nanostructures deposited on glass. In addition, silver based multilayer structures show a distinct plasmonic behaviour as compared to gold based nanostructures, which provides the sensor with an increased short-range sensitivity and a decreased long-range sensitivity. 相似文献