全文获取类型
收费全文 | 1107篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
化学 | 768篇 |
晶体学 | 1篇 |
力学 | 31篇 |
数学 | 207篇 |
物理学 | 150篇 |
出版年
2023年 | 7篇 |
2022年 | 24篇 |
2021年 | 26篇 |
2020年 | 24篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 12篇 |
2016年 | 47篇 |
2015年 | 25篇 |
2014年 | 41篇 |
2013年 | 62篇 |
2012年 | 87篇 |
2011年 | 87篇 |
2010年 | 56篇 |
2009年 | 35篇 |
2008年 | 70篇 |
2007年 | 55篇 |
2006年 | 45篇 |
2005年 | 56篇 |
2004年 | 48篇 |
2003年 | 36篇 |
2002年 | 44篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1967年 | 5篇 |
1870年 | 2篇 |
排序方式: 共有1157条查询结果,搜索用时 15 毫秒
41.
Dr. Emilio M. Pellegrino Prof. Luigi Cerruti Prof. Elena M. Ghibaudi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4330-4335
The present reflection on the development of research on carbon nanotubes (CNTs) stems from the publication of the report “Realizing the Promise of Carbon Nanotubes” by the US National Nanotechnology Initiative in 2015. The report is a critical assessment of the state‐of‐art of CNT research and highlights some unresolved issues related with this field. Starting from the results of this assessment, we carried out an analysis of the publications’ pool in CNTs and related domains, by exploiting bibliometric tools. We focused on the item of competition/collaboration between disciplines and nations, with the purpose of evaluating the position of chemistry (as a discipline) as well as the position of the main European countries and the European Union (EU) as a whole in the context of CNT research. The results of such analysis outline very clearly the interdisciplinary landscape wherein CNT research is situated and show the highly competitive place occupied by EU in the field. 相似文献
42.
Emilio J. González Patricia F. Requejo Ángeles Domínguez Eugénia A. Macedo 《Journal of solution chemistry》2013,42(4):746-763
In this study, densities and speeds of sound were measured over the whole composition range, at T = (298.15, 303.15 and 308.15) K and p = 0.1 MPa, for the binary systems of ethanol, or 1-propanol, or 2-propanol and 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, or 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide. The density and speed of sound data were used to calculate the corresponding excess molar volumes and excess molar isentropic compressions, which were fitted with the Redlich–Kister equation. From the obtained results, a discussion was carried out in terms of interactions and structure factors in these binary mixtures. 相似文献
43.
44.
45.
Among amino acids, arginine is important in human physiology because it plays an important role in cardiovascular and depression problems. In this paper the behavior of arginine as a ligand toward cadmium(II) [Cd(II)] in two different ionic media: 1.00 mol·dm?3 NaCl and NaClO4, is studied. Knowledge of the species formed between Cd(II) and arginine in a wide concentration range is useful also in biology. This system was investigated using two different methods in two ranges of hydrogen ion concentration. In acidic solutions, electromotive force measurements are performed using glass and Cd amalgam electrodes. In basic solutions, polarography was used and the shift of the half wave potential was measured as a function of the ligand concentration. The experimental data obtained in NaCl solutions are explained by assuming the formation of the species [CdL], [CdHL], [CdL2], [CdHL2] and [CdH2L2]. The data obtained in NaClO4 solutions are explained by assuming the formation of the species [CdL], [CdHL], and [CdH2L2]. In both cases the stability constants are reported. 相似文献
46.
Julia Vallejo Alejandro Pascual‐Álvarez Dr. Joan Cano Dr. Isabel Castro Prof. Dr. Miguel Julve Prof. Dr. Francesc Lloret Dr. J. Krzystek Prof. Dr. Giovanni De Munno Dr. Donatella Armentano Prof. Dr. Wolfgang Wernsdorfer Dr. Rafael Ruiz‐García Dr. Emilio Pardo 《Angewandte Chemie (International ed. in English)》2013,52(52):14075-14079
47.
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
48.
Munguia-Lopez Jose G. Juarez Rodrigo Muñoz-Sandoval Emilio Kalixto-Sanchez Marco A. Kinsella Joseph Matthew De Leon-Rodriguez Antonio 《Journal of nanoparticle research》2019,21(8):1-15
Journal of Nanoparticle Research - Workers are increasingly exposed to nanoparticles, mostly via inhalation. Respiratory protection is recommended as an additional control measure. Particulate... 相似文献
49.
Emilio Ignesti Roberto Buffa Lorenzo Fini Emiliano Sali Marco V. Tognetti Stefano Cavalieri 《Optics Communications》2012,285(6):1185-1189
We present an experimental and theoretical investigation, performed on hot sodium atoms in a ladder scheme, showing the control of the absorption and of the propagation velocity of a probe light pulse with a spectral bandwidth as large as 1.8 GHz. The predictions of the theoretical model compare favorably with the experimental results. 相似文献
50.
Emilio Carrizosa Amaya Nogales-Gómez Dolores Romero Morales 《Optimization Letters》2014,8(3):1125-1135
Recently, Support Vector Machines with the ramp loss (RLM) have attracted attention from the computational point of view. In this technical note, we propose two heuristics, the first one based on solving the continuous relaxation of a Mixed Integer Nonlinear formulation of the RLM and the second one based on the training of an SVM classifier on a reduced dataset identified by an integer linear problem. Our computational results illustrate the ability of our heuristics to handle datasets of much larger size than those previously addressed in the literature. 相似文献