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231.
Rhodium(III)‐Catalyzed Allylic C(sp3)–H Activation of Alkenyl Sulfonamides: Unexpected Formation of Azabicycles
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Dr. Alexis Archambeau Prof. Tomislav Rovis 《Angewandte Chemie (International ed. in English)》2015,54(45):13337-13340
Unsaturated N‐sulfonamides undergo a RhIII‐ catalyzed allylic C(sp3)? H activation followed by insertion with an exogenous internal alkyne. The reaction generates [3.3.0], [4.3.0], and [5.3.0] azabicyclic structures with excellent diastereoselectivity. Deuterium labeling experiments implicate a 1,3‐Rh shift as a key step in the mechanism. 相似文献
232.
233.
Paul A.W. van der Heide Valentina Spampinato Alexis Franquet Charlotte Zborowski Thierry Conard Jonathan Ludwig Kristof Paredis Wilfried Vandervorst Alexander Pirkl Ewald Niehuis 《Surface and interface analysis : SIA》2020,52(12):786-791
Secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) represent three surface analysis techniques heavily used in the complementary metal oxide semiconductor (CMOS) industry. The maturity of these techniques is demonstrated by (a) the diversity of lab-based instruments used in research and development (R&D) as well as to support fab-related issues and (b) the fact that highly automated platforms have now been or are being introduced into the fab for process control. Some recent developments of interest in the lab R&D space include the following: (a) the introduction of Orbitrap mass spectrometers into SIMS, (b) the introduction of higher energy monochromated photon sources into standalone lab-based XPS, and (c) the introduction of commercialized vacuum–scanning probe microscopy (SPM) platforms. The possibilities this opens are demonstrated through (a) SIMS analysis of organics from photoresist materials, (b) XPS subsurface analysis, ie, beyond the sputter front during depth profiling, and (c) SPM analysis of 2D material properties sensitive to the ambient environment, to mention a few. 相似文献
234.
In this article we present a Ladyženskaja–Prodi–Serrin Criteria for regularity of solutions for the Navier–Stokes equation
in three dimensions which incorporates weak L
p
norms in the space variables and log improvement in the time variable. 相似文献
235.
We define Hopf monads on an arbitrary monoidal category, extending the definition given in Bruguières and Virelizier (2007) [5] for monoidal categories with duals. A Hopf monad is a bimonad (or opmonoidal monad) whose fusion operators are invertible. This definition can be formulated in terms of Hopf adjunctions, which are comonoidal adjunctions with an invertibility condition. On a monoidal category with internal Homs, a Hopf monad is a bimonad admitting a left and a right antipode.Hopf monads generalize Hopf algebras to the non-braided setting. They also generalize Hopf algebroids (which are linear Hopf monads on a category of bimodules admitting a right adjoint). We show that any finite tensor category is the category of finite-dimensional modules over a Hopf algebroid.Any Hopf algebra in the center of a monoidal category C gives rise to a Hopf monad on C. The Hopf monads so obtained are exactly the augmented Hopf monads. More generally if a Hopf monad T is a retract of a Hopf monad P, then P is a cross product of T by a Hopf algebra of the center of the category of T-modules (generalizing the Radford–Majid bosonization of Hopf algebras).We show that the comonoidal comonad of a Hopf adjunction is canonically represented by a cocommutative central coalgebra. As a corollary, we obtain an extension of Sweedler?s Hopf module decomposition theorem to Hopf monads (in fact to the weaker notion of pre-Hopf monad). 相似文献
236.
Barrero AF Herrador MM Arteaga P Castillo A Arteaga AF 《Natural product communications》2011,6(4):439-442
An easy procedure to obtain extracts enriched in trixagol monomalonylesther (1) from aerial parts of the plant Belladia trixago chemotype Trix was developed. Preparation of (+)-dihydro-gamma-ionone (4) was carried out directly from the extracts with good yields by selective oxidation. Other interesting odorant products as alpha-ambrinol (5), ambraldehyde (6) and the tricyclic compound 7 were synthesized very efficiently using (4) as intermediate. 相似文献
237.
Rojas J Aparicio R Villasmil T Peña A Usubillaga A 《Natural product communications》2011,6(7):935-938
Kaurenic acid (1a) is a tetracyclic diterpene that has an exocyclic double bond at delta16. Isokaurenic acid (2a) has an endocyclic delta15double bond. This compound has been isolated from Espeletia tenore (Espeletinae), a resinous plant from the Venezuelan Andes, but its occurrence is rare. In order to obtain a larger amount of 2a, the isomerization of la, which is easily obtained from other Espeletinae, was tried. Kaurenic acid methyl ester (1b) was treated with dil. HCl in CH3Cl/EtOH, after 6 h under reflux a yield of 41.5% isokaurenic acid methyl ester (2b) was obtained but 35.7% 16alpha-ethoxy-kauran-19-oic acid methyl ester (3b) had formed as a byproduct. Treating 1b with CF3COOH in refluxing CH2Cl2 permitted to obtain a yield of 66.6% of 2b in 4 h and only traces of 16alpha-hydroxy-kauran-19-oic acid methyl ester (3a) as a byproduct. Both isomers were separated on a silica gel column impregnated with 20% AgNO3. Treating 2b with KOH in refluxing DMSO yielded pure isokaurenic acid, no back isomerization was observed. 相似文献
238.
This paper addresses multi-purpose machine configuration in an uncertain context through sensitivity analysis. The so-called configuration is the machine??s ability to process products, and the uncertain context is modelled as a demand variation affecting the forecast demand. Given a configuration, this work aims at assessing the completion time deviation when the workshop demand is subject to perturbation. Such quantitative information can be used in a robustness approach for selecting the most appropriate configuration. To do so, the configuration impact on the completion time value that can be reached by solving the attached scheduling problem is first investigated. Then, the completion time deviation is written as a piecewise linear function of the magnitude of demand variation. The proposed approach, which is based on the solution of a set of linear programs, is illustrated through a detailed example. It is shown to be polynomial, and fast enough for addressing real-world instances. Finally, how to compare two configurations on the basis of completion time deviation in an uncertain context is demonstrated. 相似文献
239.
Controlling fullerene addition sequences, regioselectivity and magic numbers via metal encapsulation
A systematic density functional study of chlorine addition to C(70) up to C(70)Cl(12) confirms experimental observations of regioselectivity and stability of C(70)Cl(10). We show that K@C(70) follows an alternative addition sequence with different isomers and magic numbers to C(70) such as KC(70)Cl(3). This prediction is important for controlling functionalisation behaviour via encapsulation and endofullerene purification. 相似文献
240.
Maether MP Bernat V Maturano M André-Barrès C Ladeira S Valentin A Vial H Payrastre C 《Organic & biomolecular chemistry》2011,9(21):7400-7410
Two series of streptocyanine dyes incorporating cyclic peroxide or 4-aminoquinoline moieties are prepared and X-ray diffraction structures for three compounds are determined. All hybrid dyes show good antiplasmodial activity (0.06 to 0.66 μM) and are not or are slightly cytotoxic, except 10a. 相似文献