全文获取类型
收费全文 | 11369篇 |
免费 | 645篇 |
国内免费 | 57篇 |
专业分类
化学 | 8225篇 |
晶体学 | 38篇 |
力学 | 292篇 |
数学 | 1858篇 |
物理学 | 1658篇 |
出版年
2023年 | 91篇 |
2022年 | 77篇 |
2021年 | 182篇 |
2020年 | 291篇 |
2019年 | 305篇 |
2018年 | 144篇 |
2017年 | 166篇 |
2016年 | 436篇 |
2015年 | 476篇 |
2014年 | 489篇 |
2013年 | 648篇 |
2012年 | 919篇 |
2011年 | 922篇 |
2010年 | 570篇 |
2009年 | 493篇 |
2008年 | 734篇 |
2007年 | 704篇 |
2006年 | 645篇 |
2005年 | 629篇 |
2004年 | 495篇 |
2003年 | 405篇 |
2002年 | 338篇 |
2001年 | 107篇 |
2000年 | 80篇 |
1999年 | 77篇 |
1998年 | 83篇 |
1997年 | 123篇 |
1996年 | 100篇 |
1995年 | 86篇 |
1994年 | 79篇 |
1993年 | 91篇 |
1992年 | 66篇 |
1991年 | 69篇 |
1990年 | 54篇 |
1989年 | 64篇 |
1988年 | 43篇 |
1987年 | 36篇 |
1986年 | 42篇 |
1985年 | 58篇 |
1984年 | 48篇 |
1983年 | 48篇 |
1982年 | 51篇 |
1981年 | 58篇 |
1980年 | 42篇 |
1979年 | 47篇 |
1978年 | 44篇 |
1977年 | 44篇 |
1976年 | 50篇 |
1975年 | 42篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Valentina Bleve Christian Schäfer Dr. Paola Franchi Dr. Serena Silvi Prof. Dr. Elisabetta Mezzina Prof. Dr. Alberto Credi Prof. Marco Lucarini 《ChemistryOpen》2015,4(1):2-21
An acid–base switchable molecular shuttle based on a [2]rotaxane, incorporating stable radical units in both the ring and dumbbell components, is reported. The [2]rotaxane comprises a dibenzo[24]crown-8 ring (DB24C8) interlocked with a dumbbell component that possesses a dialkylammonium (NH2+) and a 4,4′-bipyridinium (BPY2+) recognition site. Deprotonation of the rotaxane NH2+ centers effects a quantitative displacement of the DB24C8 macroring to the BPY2+ recognition site, a process that can be reversed by acid treatment. Interaction between stable 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radicals connected to the ring and dumbbell components could be switched between noncoupled (three-line electron paramagnetic resonance (EPR) spectrum) and coupled (five-line EPR spectrum) upon displacement of the spin-labelled DB24C8 macroring. The complete base- and acid-induced switching cycle of the EPR pattern was repeated six times without an appreciable loss of signal, highlighting the reversibility of the process. Hence, this molecular machine is capable of switching on/off magnetic interactions by chemically driven reversible mechanical effects. A system of this kind represents an initial step towards a new generation of nanoscale magnetic switches that may be of interest for a variety of applications. 相似文献
92.
Magdalena Graczyk-Zajac Maximilian Wimmer Yeping Xu Gerd Buntkowsky Christian Neumann Ralf Riedel 《Journal of Solid State Electrochemistry》2017,21(1):47-55
Within this work, we analyze the lithium storage sites within carbon/silicon carbonitride (SiCN) composites. Commercial carbons, HD3 (hard carbon) and LD1N and LD2N (soft carbons), of varying porosity are impregnated with polysilazane (HTT 1800) and pyrolysed at 1100 °C. It is found in the first part of this study (Graczyk-Zajac et al. J Solid State Electrochem 19:2763–2769, 2015) that the initial porosity of the carbon phase plays an important role in determining the lithium insertion capacity and rate capability of the composite material. By applying Raman spectroscopy and solid-state 7Li MAS NMR on pristine, lithiated, and delithiated samples, we investigate the lithium storage sites within the composite materials. By means of Raman spectroscopy, it has been found that lithium storage in hard carbon-derived composites occurs in a significant extent via adsorption-like process within unorganized carbon, whereas for the soft carbon composites, storage in turbostratic carbon is identified. 7Li solid-state NMR confirms these findings revealing that more than 33 % of lithium stored in HD3/SiCN is adsorbed in ionic form at the surface and in pores of the composite, while around 38 % is stored between carbon layers. LD1N and LD2N composites store more than 50 % of lithium in the intercalation-type sites. 相似文献
93.
Dr. Samuel M. Meier M. Sc. Dominique Kreutz Dr. Lilli Winter M. Sc. Matthias H. M. Klose M. Sc. Klaudia Cseh M. Sc. Tamara Weiss Dr. Andrea Bileck M. Sc. Beatrix Alte Dr. Johanna C. Mader M. Sc. Samir Jana Dr. Annesha Chatterjee Dr. Arindam Bhattacharyya Michaela Hejl Dr. Michael A. Jakupec Priv.-Doz. Dr. Petra Heffeter Prof. Dr. Walter Berger Prof. Dr. Christian G. Hartinger Prof. Dr. Bernhard K. Keppler Prof. Dr. Gerhard Wiche Prof. Dr. Christopher Gerner 《Angewandte Chemie (International ed. in English)》2017,56(28):8267-8271
Organometallic metal(arene) anticancer agents require ligand exchange for their anticancer activity and this is generally believed to confer low selectivity for potential cellular targets. However, using an integrated proteomics-based target-response profiling approach as a potent hypothesis-generating procedure, we found an unexpected target selectivity of a ruthenium(arene) pyridinecarbothioamide (plecstatin) for plectin, a scaffold protein and cytolinker, which was validated in a plectin knock-out model in vitro. Plectin targeting shows potential as a strategy to inhibit tumor invasiveness as shown in cultured tumor spheroids while oral administration of plecstatin-1 to mice reduces tumor growth more efficiently in the invasive B16 melanoma than in the CT26 colon tumor model. 相似文献
94.
Christian Döbler 《Journal of Theoretical Probability》2017,30(1):85-116
Distributional transformations characterized by equations relating expectations of test functions weighted by a given biasing function on the original distribution to expectations of the test function’s higher derivatives with respect to the transformed distribution play a great role in Stein’s method and were, in great generality, first considered by Goldstein and Reinert (J Theoret Probab 18(1):237–260, 2005. doi: 10.1007/s10959-004-2602-6). We prove two abstract existence and uniqueness results for such distributional transformations, generalizing their \(X-P\)-bias transformation. On the one hand, we show how one can abandon previously necessary orthogonality relations by subtracting an explicitly known polynomial depending on the test function from the test function itself. On the other hand, we prove that for a given nonnegative integer m, it is possible to obtain the expectation of the m-th derivative of the test function with respect to the transformed distribution in the defining equation, even though the biasing function may have \(k<m\) sign changes, if these two numbers have the same parity. We explain how these results can be used to guarantee the existence of two different generalizations of the zero-bias transformation by Goldstein and Reinert (Ann Appl Probab 7(4):935–952, 1997. doi: 10.1214/aoap/1043862419). Further applications include the derivation of Stein-type characterizations without needing to solve any Stein equation and the presentation of a general framework for estimating the distance from the distribution of a given real random variable X to that of a random variable Z, whose distribution is characterized by some mth-order linear differential operator. We also explain the fact that, in general, the biased distribution depends on the choice of the sign change points, if these are ambiguous. This new phenomenon does not appear in the framework from Goldstein and Reinert (2005). 相似文献
95.
Models based on sparse graphs are of interest to many communities: they appear as basic models in combinatorics, probability theory, optimization, statistical physics, information theory, and more applied fields of social sciences and economics. Different notions of similarity (and hence convergence) of sparse graphs are of interest in different communities. In probability theory and combinatorics, the notion of Benjamini‐Schramm convergence, also known as left‐convergence, is used quite frequently. Statistical physicists are interested in the the existence of the thermodynamic limit of free energies, which leads naturally to the notion of right‐convergence. Combinatorial optimization problems naturally lead to so‐called partition convergence, which relates to the convergence of optimal values of a variety of constraint satisfaction problems. The relationship between these different notions of similarity and convergence is, however, poorly understood. In this paper we introduce a new notion of convergence of sparse graphs, which we call Large Deviations or LD‐convergence, and which is based on the theory of large deviations. The notion is introduced by “decorating” the nodes of the graph with random uniform i.i.d. weights and constructing corresponding random measures on and . A graph sequence is defined to be converging if the corresponding sequence of random measures satisfies the Large Deviations Principle with respect to the topology of weak convergence on bounded measures on . The corresponding large deviations rate function can be interpreted as the limit object of the sparse graph sequence. In particular, we can express the limiting free energies in terms of this limit object. We then establish that LD‐convergence implies the other three notions of convergence discussed above, and at the same time establish several previously unknown relationships between the other notions of convergence. In particular, we show that partition‐convergence does not imply left‐ or right‐convergence, and that right‐convergence does not imply partition‐convergence. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 51, 52–89, 2017 相似文献
96.
Our work presents extensions of multi layered composite sphere models known from the literature to temperature-dependent elastic effects accompanied by curing. In particular, volumetric effective properties are obtained by homogenization for a representative unit cell (micro-RVE) on the heterogeneous microscale for thermo-chemo-mechanical coupling within linear elasticity. To this end, an analytical solution for an n-layered composite sphere model is derived. In a numerical study for a (3)-phase matrix it is demonstrated that the effective elastic and thermal properties lie within Voigt and Reuss bounds, whilst for the chemical part of the model an analogous result is obtained for the effective strains. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
Christian?H.?Wei?Email authorView authors OrcID profile 《Methodology and Computing in Applied Probability》2017,19(3):997-1007
We analyze the eigenstructure of count-data Markov chains. Our main focus is on so-called CLAR(1) models, which are characterized by having a linear conditional mean, and also on the case of a finite range, where the second largest eigenvalue determines the speed of convergence of the forecasting distributions. We derive a lower bound for the second largest eigenvalue, which often (but not always) even equals this eigenvalue. This becomes clear by deriving the complete set of eigenvalues for several specific cases of CLAR(1) models. 相似文献
98.
Christian Seifert 《PAMM》2017,17(1):861-862
We generalise the notion of band-dominated operators originally introduced for the space ℓp(ℤn) to the setup of metric measure spaces and show various algebraic properties of this space of operators. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
99.
Dr. Shi Tang Dr. Zhi Wang Yanzi Xu Huili Ma Dr. Jia Wang Dr. Christian Larsen Prof. Dongfeng Dang Prof. Ergang Wang Prof. Ludvig Edman 《Angewandte Chemie (International ed. in English)》2023,62(23):e202302874
The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation. 相似文献
100.
Dr. Maximilian Muhr Hao Liang Dr. Lars Allmendinger Raphael Bühler Fabrizio E. Napoli Dr. Dardan Ukaj Dr. Mirza Cokoja Dr. Christian Jandl Dr. Samia Kahlal Prof. Dr. Jean-Yves Saillard Dr. Christian Gemel Prof. Dr. Roland A. Fischer 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308790
The bimetallic, decanuclear Ni3Ga7-cluster of the formula [Ni3(GaTMP)3(μ2-GaTMP)3(μ3-GaTMP)] ( 1 , TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2 . Low-temperature 2D NMR experiments at −80 °C show that 2 consist of a mixture of a di- ( 2Di ), tetra- ( 2Tetra ) and hexahydride species ( 2Hexa ). The structures of 2Di and 2Tetra are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis. 相似文献