全文获取类型
收费全文 | 1506篇 |
免费 | 81篇 |
国内免费 | 1篇 |
专业分类
化学 | 1317篇 |
晶体学 | 3篇 |
力学 | 11篇 |
数学 | 118篇 |
物理学 | 139篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 37篇 |
2019年 | 32篇 |
2018年 | 18篇 |
2017年 | 5篇 |
2016年 | 56篇 |
2015年 | 54篇 |
2014年 | 46篇 |
2013年 | 66篇 |
2012年 | 93篇 |
2011年 | 134篇 |
2010年 | 70篇 |
2009年 | 80篇 |
2008年 | 86篇 |
2007年 | 91篇 |
2006年 | 84篇 |
2005年 | 71篇 |
2004年 | 71篇 |
2003年 | 61篇 |
2002年 | 60篇 |
2001年 | 27篇 |
2000年 | 21篇 |
1999年 | 25篇 |
1998年 | 26篇 |
1997年 | 23篇 |
1996年 | 21篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1932年 | 2篇 |
1891年 | 2篇 |
排序方式: 共有1588条查询结果,搜索用时 644 毫秒
41.
The convergent syntheses of 3-deazapurine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides, including 3-deaza-2′-deoxyadenosine ( 1a ) and 3-deaza-2′,3′-dideoxyadenosine ( 1b ) is described. The 4-chloro-lH-imidazo[4,5-c]pyridinyl anion derived from 5 was reacted with either 2′-deoxyhalogenose 6 or 2′,3′-dideoxyhalogenose 10 yielding two regioisomeric (N1 and N3) glycosylation products. They were deprotected and converted into 4-substituted imidazo[4,5-c]pyridine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides. Compounds 1a and 1b proved to be more stable against proton-catalyzed N-glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase. 相似文献
42.
Sabine Beernaerts Marie Gerard Philippe Debongnie Jean-Paul Barthelemy Luc Pussemier Alfred Copin 《International journal of environmental analytical chemistry》2013,93(6):469-480
A monitoring study was carried out in 1998-1999 on a medium-sized (c. 4580 km2) watershed of the Dyle (or Dijle) river in central Belgium, composed of both rural and urbanized areas. This watershed may be considered as representative of a large part of the country. Samples were taken each month from seven sites along the course of the river, plus one from its major affluent the Demer. The eight molecules monitored were the main herbicides used on the major crops in the area, plus some used in nonagricultural sectors. The concentrations found were mostly in the 0-3 μg/L range, with some peaks between 3 and 14 μg/L. The averages over all spring and summer samples analyzed ranged from 0.14 (bentazone) to 1.54 μg/L (diuron). Time and space specific patterns could be observed. 相似文献
43.
44.
45.
The (mixed finite element) discretization of the linearized Navier–Stokes equations leads to a linear system of equations of saddle point type. The iterative solution of this linear system requires the construction of suitable preconditioners, especially in the case of high Reynolds numbers. In the past, a stabilizing approach has been suggested which does not change the exact solution but influences the accuracy of the discrete solution as well as the effectiveness of iterative solvers. This stabilization technique can be performed on the continuous side before the discretization, where it is known as ‘grad‐div’ (GD) stabilization, as well as on the discrete side where it is known as an ‘augmented Lagrangian’ (AL) technique (and does not change the discrete solution). In this paper, we study the applicability of ??‐LU factorizations to solve the arising subproblems in the different variants of stabilized saddle point systems. We consider both the saddle point systems that arise from the stabilization in the continuous as well as on the discrete setting. Recently, a modified AL preconditioner has been proposed for the system resulting from the discrete stabilization. We provide a straightforward generalization of this approach to the GD stabilization. We conclude the paper with numerical tests for a variety of problems to illustrate the behavior of the considered preconditioners as well as the suitability of ??‐LU factorization in the preconditioners. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
46.
Analyse von Protease‐Inhibitor‐Interaktionen unter Nutzung evolvierbarer tricyclischer Microviridine
47.
Myriam Drouin Dr. Parvesh Wadhwani Dr. Stephan L. Grage Dr. Jochen Bürck Dr. Johannes Reichert Sébastien Tremblay Marie Sabine Mayer Christian Diel Alexander Staub Prof. Jean-François Paquin Prof. Dr. Anne S. Ulrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1511-1517
Solid-state 19F NMR is a powerful method to study the interactions of biologically active peptides with membranes. So far, in labelled peptides, the 19F-reporter group has always been installed on the side chain of an amino acid. Given the fact that monofluoroalkenes are non-hydrolyzable peptide bond mimics, we have synthesized a monofluoroalkene-based dipeptide isostere, Val-Ψ[(Z)-CF=CH]-Gly, and inserted it in the sequence of two well-studied antimicrobial peptides: PGLa and (KIGAKI)3 are representatives of an α-helix and a β-sheet. The conformations and biological activities of these labeled peptides were studied to assess the suitability of monofluoroalkenes for 19F NMR structure analysis. 相似文献
48.
Mandana Amiri Zahra Tofighi Ali Khodayari Abolfazl Bezaatpour Shabnam Sohrabnezhad Vladyslav Mishyn Rabah Boukherroub Sabine Szunerits 《应用有机金属化学》2020,34(10):e5871
We report a Cu-based metal–organic framework (MOF) decorated by CuO nanostructures as an efficient catalyst for the oxygen evolution reaction (OER). MIL-53(Cu) was synthesized by a hydrothermal approach using 1,4-bezenedicarboxylic acid as organic precursor and further annealed at 300°C to form CuO nanostructures on its surface. The produced electrocatalyst, CuO@MIL-53(Cu), was characterized using various techniques. Under alkaline conditions, the developed electrocatalyst exhibited an overpotential of 801 and 336 mV versus RHE at 10 and 1 mA cm−2, respectively. The reproducibility of the catalytic performance was validated using several electrodes. It was confirmed that the CuO hair-like nanostructures grown on MIL-53(Cu) using thermal treatment exhibit high OER activity, good kinetics and durability. CuO@MIL-53(Cu) is an economic noble-metal-free OER electrocatalyst. It has potential for application as anode material for sustainable energy technologies like batteries, fuel cells and water electrolysis. 相似文献
49.
50.
Sabine Kopec Emilio Martínez-Núñez Juan Soto Daniel Peláez 《International journal of quantum chemistry》2019,119(21):e26008
We present a generalization of the transition state search using chemical dynamics simulations (TSSCDS) methodology (discussed in a previous study) which allows the topographical characterization of intermolecular potential energy surfaces (IPES) for non-covalently bound complexes (vdW-TSSCDS). Starting from a single random input geometry, we show that vdW-TSSCDS is able to globally and automatically locate stationary points of an IPES, even in limiting cases such as extremely flat regions or nontrivial topologies (eg, bifurcation points). The basic idea is the expression of the connectivity matrix in block structure, where diagonal blocks correspond to the isolated fragments and off-diagonal blocks provide the intermolecular connectivity. To this end, we introduce a new definition of bound or not, in a non-covalent sense, utilizing an extra set of van der Waals distances, which encompasses all kinds of non-covalent distances. To discuss the use of the vdW-TSSCDS method, we present a series of 2-body van der Waals systems, namely, Ar-Benzene (3D), N2-Benzene (6D) and H2O-Benzene (9D). Finally, we further illustrate its capabilities by presenting some applications for n-body problems (n > 2), (H2O)2-Benzene (12D) and (H2O)3-Benzene (21D), as well as to a reactive, fully-flexible, system (Benzene-NO2)+ (39D) in which the simultaneous breaking/formation of both covalent and non-covalent interactions takes place. 相似文献