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81.
Gerald Giester 《Monatshefte für Chemie / Chemical Monthly》1989,120(8-9):661-666
Summary Single crystal X-ray data of the hydrothermally grown new phase Li2Cu3(SeO3)2(SeO4)2 were measured with a four-circle diffractometer up to sin /=0.81 Å–1 [I2/a,Z=4,V=1175.5 Å3,a=16.293(6),b=5.007(2),c=14.448(6) Å, = 94.21(1)°]. The structure was determined by direct and Fourier methods and refined toR=0.034,R
w
=0.027 for 2 086 independent reflections.Cu(1)[4+1]O5 forms a tetragonal pyramid, Cu(2)[4 + 2]O6 is a strongly elongated octahedron. The Li atom is surrounded by four O atoms forming a distorted tetrahedron. Se(IV)O3 and Se(VI)O4 groups are in accordance to literature, mean Se-O bond lengths are 1.714 and 1.644 Å.
Die Kristallstruktur von Li2Cu3(SeO3)2(SeO4)2
Zusammenfassung Einkristall-Röntgendaten der hydrothermal gezüchteten neuen Phase Li2Cu3(SeO3)2(SeO4)2 wurden mit einem Vierkreisdiffraktometer im Bereich bis zu sin /=0.81 Å–1 gemessen [I2/a,Z=4,V=1175.5 Å3,a=16.293(6),b=5.007(2),c=14.448(6) Å, =94.21(1)°]. Die Kristallstruktur wurde mittels direkter und Fourier-Methoden bestimmt und für 2 086 unabhängige Reflexe zuR=0.034,R w =0.027 verfeinert.Cu(1)[4+1]O5 bildet eine tetragonale Pyramide, Cu(2)[4+2]O6 ist ein stark verlängertes Oktaeder. Das Li-Atom ist von vier O-Atomen in Gestalt eines verzerrten Tetraeders umgeben. Die Se(IV)O3-und Se(VI)O4-Gruppen entsprechen der Literatur, die mittleren Se-O-Abstände betragen 1.714 und 1.644 Å.相似文献
82.
Mohammad Reza Ganjali Morteza HosseiniFatemeh Basiripour Mehran JavanbakhtOmid Reza Hashemi Majid Faal RastegarMojtaba Shamsipur Gerald.W Buchanen 《Analytica chimica acta》2002,464(2):181-186
A novel selective membrane electrode for determination of ultra-trace amount of lead was prepared. The PVC membrane containing N,N′-dimethylcyanodiaza-18-cown-6 (DMCDA18C6) directly coated on a graphite electrode, exhibits a Nernstian response for Pb2+ ions over a very wide concentration range (from 1.0×10−2 to 1.0×10−7 M) with a limit of detection of 7.0×10−8 M (∼14.5 ppb). It has a fast response time of ∼10 s and can be used for at least 2 months without any major deviation in potential. The electrode revealed very good selectivity with respect to all common alkali, alkaline earth, transition and heavy metal ions. The proposed sensor was used as an indicator electrode in potentiometric titration of lead ions and in determination of lead in edible oil, human hair and water samples. The proposed sensor was found to be superior to the best Pb2+-selective electrodes reported in terms of detection limit and selectivity coefficient. 相似文献
83.
Gerald Giester 《Monatshefte für Chemie / Chemical Monthly》1992,123(11):957-963
Summary The crystal structure of the hydrothermally synthesized compound Fe(SeO2OH) (SeO4) · H2O was determined by single crystal diffraction methods:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 Å3;Z=4, space group P21/c,R=0.029,R
w=0.027 for 2430 independent reflections (sin /0.76 Å–1). Isolated FeO5(H2O)-octahedra share five corners with [SeO2OH] and [SeO4] groups to form sheets parallel to (100). These sheets are interconnected via hydrogen bonds only.
Die Kristallstruktur von Fe(SeO2OH)(SeO4)·H2O
Zusammenfassung Die Kristallstruktur der hydrothermal dargestellten Verbindung Fe(SeO2OH) (SeO4)·H2O wurde mittels Einkristallbeugungsmethoden bestimmt:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 Å3;Z=4, Raumgruppe P21/c,R=0.029,R w=0.027 für 2 430 unabhängige Reflexe (sin / 0.76 Å–1). Isolierte FeO5(H2O)-Oktaeder teilen fünf Ecken mit [SeO2OH]- und [SeO4]-Gruppen, wobei sie Schichten parallel (100) bilden. Diese Schichten sind nur über Wasserstoffbrücken miteinander verbunden.相似文献
84.
Cornelissen C Erker G Kehr G Fröhlich R 《Dalton transactions (Cambridge, England : 2003)》2004,(23):4059-4063
Treatment of the complexes [(C(5)H(4)PR(2))(2)Zr(CH(3))(2)](b: R = isopropyl; c: R = cyclohexyl) with the reagent HIr(CO)(PPh(3))(3) (2b) yield the heterobimetallic complexes [mu-C(5)H(4)PR(2))(2)(H(3)C-Zr-Ir(CO)(PPh(3)))] (4b, 4c) with evolution of methane. The reaction of the -PPh(2) substituted analogue with initially yields an intermediate [(H(3)C)(2)Zr(mu-C(5)H(4)PPh(2))(2)Ir(H)(CO)(PPh(3))] 5a, that still contains both methyl groups at zirconium and does not contain a metal-metal bond. At room temperature, the intermediate reacts further with methane formation to eventually yield the (Zr-Ir) complex 4a. The corresponding [mu-C(5)H(4)PR(2))(2)(H(3)C-Zr-Rh(CO)(PPh(3)))] complexes 3a (R = Ph) and 3b (R = isopropyl) react cleanly with isopropyl alcohol to liberate methane and yield the corresponding [mu-C(5)H(4)PR(2))(2)(Me(2)CHO-Zr-Rh(CO)(PPh(3)))] products (7a, 7b). Carefully monitoring the reaction of with Me(2)CHOH by NMR revealed that the Zr-Rh functionality is attacked first to give the intermediate [Me(Me(2)CHO)Zr([micro sign]-C(5)H(4)PR(2))(2)Rh(H)(CO)(PPh(3))] (6b). This intermediate then reacts further to cleave off methane and re-form the (Zr-Rh) metal-metal bond to yield the product 7b. The tetrametallic mu-oxo-(Zr-Rh) metallocene derivate 11a was obtained starting from the (Zr-Rh) complex 3a and it was characterized by X-ray diffraction. It may be that this reaction is also initiated by H-OH addition to the [Zr-Rh] metal-metal bond. 相似文献
85.
86.
Zusammenfassung Es wurde untersucht, warum Indol und viele seiner Derivate bei der Aminostickstoffbestimmung ein Gasvolumen liefern, obwohl sie keine primäre Aminogruppe besitzen. An Hand von präparativen Befunden wird gezeigt, daß die anomale Reaktion bei Indol in folgender Weise abläuft: Bei Einwirkung von salpetriger Säure bildet sich 3-Nitrosoindol, das sieh mit freiem Indol zu Indolrot polymerisiert. Gleichzeitig lagert sich die Nitrosogruppe zur Isonitrosogruppe um. Diese reagiert nun mit überschüssiger salpetriger Säure unter Entwicklung von Stickstoff und Distickstoffoxyd. Ist die Stellung 2 und 3 besetzt, so bleibt die anomale Gasentwicklung aus, da sich keine Isonitrosoverbindung bilden kann. Es wurde auch das Verhalten von 3-Methylindol und 3-Indolylessigsäure untersucht und die anomale Reaktion erörtert.
I: Anomalie der Isonitrosoverbindungen1; II: Anomalie der Verbindungen mit NH-CO-Gruppierung2; III: Anomalie der Verbindungen mit aktiven Methylengruppen3; IV: Anomalie von Glycin4; V: Anomalie der Phenole5. 相似文献
Summary A study was made to learn why indole and many of its derivatives deliver a gas volume during the determination of the amino nitrogen, even though they contain no primary amino group. On the basis of preparative findings, it was shown that in the case of indole the anomalous reaction proceeds in the following fashion. When the nitrous acid reacts, 3-nitrosoindole is formed, which then polymerizes with free indole to indole red. At the same time, the nitroso group rearranges into the isonitroso group. The latter reacts with excess nitrous acid with evolution of nitric oxide and nitrogen dioxide. If positions 2 and 3 are occupied, there is no anomalous generation of gas, because no isonitroso compound can form. The behavior of 3-methylindole and 3-indylacetic acid was also studied and the anomalous reaction noted.
Résumé Les auteurs ont recherché pourquoi l'indol et nombre de ses dérivés donnent lieu à un dégagement gazeux lors de la détermination de l'azote aminé bien qu'ils ne contiennent aucun groupement aminé primaire. Des constatations effectuées au cours de travaux de chimie préparative ont montré que la réaction anormale de l'indol a le cours suivant: lors de l'action de l'acide nitreux il se forme du nitroso-3 indol qui en présence d'indol libre se polymerise en rouge d'indol. Simultanément le groupement nitrosé se transpose en groupement isonitrosé. Ce dernier réagit alors avec l'acide nitreux en excès en donnant lieu à un dégagement d'azote et de protoxyde d'azote. Si les positions 2 et 3 sont occupées il ne se produit pas de dégagement gazeux anormal car la combinaison isonitrosée ne peut se former. Les auteurs ont également examiné le comportement du méthyl-3 indol et de l'acide indoyl-3 acétique et discuté leurs réactions anormales.
I: Anomalie der Isonitrosoverbindungen1; II: Anomalie der Verbindungen mit NH-CO-Gruppierung2; III: Anomalie der Verbindungen mit aktiven Methylengruppen3; IV: Anomalie von Glycin4; V: Anomalie der Phenole5. 相似文献
87.
88.
Dale Spangler Ian Henderson Williams Gerald M. Maggiora 《Journal of computational chemistry》1983,4(4):524-541
Quantum mechanical calculations of the geometric, energetic, electronic, and vibrational features of a transition structure for gas-phase water–formaldehyde addition (FW1?) are described, and a new transition-structure search algorithm is presented. Basis-set-dependent effects are assessed by comparisons of computed properties obtained from self-consistent field (SCF) molecular orbital (MO) calculations with STO-3G, 4-31G, and 6-31G** basis sets in the absence of electron correlation. The results obtained suggest that STO-3G-level calculations may be sufficiently reliable for the prediction of the transition structure of FW1? and for the transition structures of related carbonyl addition reactions. Moreover, the calculated activation energy for formation of FW1? from water and formaldehyde (?44 kcal mol?1) is very similar in all three basis sets. However, the energy of formaldehyde hydration predicted by STO-3G (? ?45 kcal mol?1) is about three times larger than that predicted by the other two basis sets, with the activation energy for dihydroxymethane dehydration also being too large in STO-3G. Calculated force constants in all three basis sets are generally too large, leading to vibrational frequencies that are also too large. However, uniformly scaled force constants (in internal coordinates) give much better agreement with experimental frequencies, scaled 4-31G force constants being slightly superior to scaled STO-3G force constants. 相似文献
89.
In this paper, work on a new model,an augmented ribbon model, for describing a number of features of primary, secondary, and super-secondary protein structure in a qualitative but mathematically rigorous way is discussed. The structural features that can be treated by the model include connectivity, directionality, chirality, orientation, and proximity which, in many cases, are difficult to deal with using more traditional structural representations (e.g. wireframe, ball-and-stick, or space-filling CPK). In practice, the information encoded in the augmented ribbon model is represented by a labelled, directed graph (digraph) which provides an efficient means for storing and analyzing the information on computers. This opens the way to computer-based analyses of proteins and for the application of similarity methods that have been shown to be quite useful in treating small molecules. 相似文献
90.
Rouhalla Bagheri Khirud B. Chakraborty Gerald Scott 《Journal of polymer science. Part A, Polymer chemistry》1984,22(7):1573-1578
When 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (HTMPO) is processed in polypropylene in a closed mixer, almost 50% is converted to other products during the first few minutes whilst the applied torque in the mixer is high. There is associated formation of unsaturation and this fact, in conjunction with the almost complete regeneration of nitroxyl within five minutes, suggests that the corresponding hydroxylamine (HTMPOH), which can be qualitatively identified, is the major transformation product. A study of the UV stability of PP films fabricated from polymer processed for varying times shows that UV stability is related to the quantity of the redox couple (HTMPO + HTMPOH) remaining in the polymer. This is considerably reduced by severe processing. The redox capable has almost no thermal antioxidant (oven aging) activity. 相似文献