全文获取类型
收费全文 | 2914篇 |
免费 | 120篇 |
国内免费 | 19篇 |
专业分类
化学 | 2083篇 |
晶体学 | 15篇 |
力学 | 61篇 |
数学 | 322篇 |
物理学 | 572篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 49篇 |
2020年 | 35篇 |
2019年 | 51篇 |
2018年 | 34篇 |
2017年 | 34篇 |
2016年 | 74篇 |
2015年 | 77篇 |
2014年 | 83篇 |
2013年 | 164篇 |
2012年 | 171篇 |
2011年 | 182篇 |
2010年 | 116篇 |
2009年 | 114篇 |
2008年 | 180篇 |
2007年 | 161篇 |
2006年 | 138篇 |
2005年 | 147篇 |
2004年 | 133篇 |
2003年 | 93篇 |
2002年 | 108篇 |
2001年 | 55篇 |
2000年 | 78篇 |
1999年 | 32篇 |
1998年 | 46篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 43篇 |
1994年 | 37篇 |
1993年 | 35篇 |
1992年 | 37篇 |
1991年 | 39篇 |
1990年 | 36篇 |
1989年 | 25篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 31篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 9篇 |
排序方式: 共有3053条查询结果,搜索用时 15 毫秒
11.
12.
J. M. P. Garcia H. F. M. Filho L. V. Zuquette 《Journal of Thermal Analysis and Calorimetry》2007,89(2):385-388
Angra dos Reis/Itaguai region of the state of Rio de Janeiro, Brazil, is a very problematic area due to the instability of
slope and landslides, due to geological and geomorphological conditions and to the significant and continuous human occupation
over favorable areas is prone to the triggering of landslides. The samples were analyzed by thermogravimetry (TG), derivative
thermogravimetry (DTG) and differential thermal analysis (DTA). This paper analyzes and characterizes the clay minerals and
presence of water, gravitational mass movements’ sites and compares it with sites where gravitational mass movements do not
occur. Indeed, this analysis also attempts to verify the presence of minerals. 相似文献
13.
M. Garcia Ramirez J. Y. Cavaill A. Dufresne P. Tkly 《Journal of Polymer Science.Polymer Physics》1995,33(15):2109-2124
Blends of the natural polymer cellulose with a synthetic polymer, polyamide 66, are studied in order to determine if the expected strong interaction between them, due to hydrogen bonds, could improve their mechanical properties such as strength and elongation at break. In a previous work {Part I, J. Polym. Sci. Polym. Phys., 32 , 1437 (1994)}, the preparation technique and the characterization of cellulose-polyamide 66 (PA66) blends were described in detail. Several samples in the composition range between 0 to 70 wt % of PA66 were carefully dried and examined using dynamic mechanical and tensile tests. Based on previous work a new percolation model has been developed. It takes both linear and nonlinear mechanical behaviors into account and allows for the effect of adhesion between material domains. From comparison between experimental and predicted data, it is concluded that a partial miscibility between the amorphous phases of cellulose and PA66 exists and is responsible for a strong adhesion at their interface. Solid-state 13C nuclear magnetic resonance has also been used to study these samples and supports the existence of strong interactions between both homopolymers. © 1995 John Wiley & Sons, Inc. 相似文献
14.
Sonia M. F. Garcia 《Numerical Methods for Partial Differential Equations》1994,10(2):149-169
This article treats mixed finite-element methods for second-order quasilinear parabolic equations. A fully discrete scheme is presented and L2-error estimates are established. The convergence of both the function value and the flux is demonstrated. In a previous paper, Part I the author introduced powerful numerical methods for dealing with parabolic problems. The technique used here is an extension of the continuous-time results for the discrete-time case. © 1994 John Wiley & Sons, Inc. 相似文献
15.
Angel L. Esteban Maria P. Galache Francisco Mora Ernesto Diez Jesus San Fabian 《Journal of computational chemistry》1989,10(7):887-895
An equation is formulated on the basis of theoretical INDO/FPT calculations which describes the angular dependence of the propanic long-range coupling constant 4JMeH in substituted HCCCH3 fragments. This equation is a truncated Fourier series in the torsion angle ?, HCCMe, which takes into account the dependence of the Fourier coefficients on the bond angle θ, CCMe. The substituent effects are assumed to be additive. Some parameters in the equation may be obtained from the 4JMeH couplings in propane and neopentane derivatives. The calculated effect upon 4JMeH of changes in the bond angle θ is significant and it seems to be in part the cause of some effects which have been attributed to conformational dependence. 相似文献
16.
17.
Nanoscale organization of the pathogen receptor DC-SIGN mapped by single-molecule high-resolution fluorescence microscopy. 总被引:3,自引:0,他引:3
Bärbel I. de Bakker Dr. Frank de Lange Dr. Alessandra Cambi Dr. Jeroen P. Korterik Erik M. H. P. van Dijk Dr. Niek F. van Hulst Prof. Carl G. Figdor Prof. Maria F. Garcia‐Parajo Prof. 《Chemphyschem》2007,8(10):1473-1480
DC-SIGN, a C-type lectin exclusively expressed on dendritic cells (DCs), plays an important role in pathogen recognition by binding with high affinity to a large variety of microorganisms. Recent experimental evidence points to a direct relation between the function of DC-SIGN as a viral receptor and its spatial arrangement on the plasma membrane. We have investigated the nanoscale organization of fluorescently labeled DC-SIGN on intact isolated DCs by means of near-field scanning optical microscopy (NSOM) combined with single-molecule detection. Fluorescence spots of different intensity and size have been directly visualized by optical means with a spatial resolution of less than 100 nm. Intensity- and size-distribution histograms of the DC-SIGN fluorescent spots confirm that approximately 80 % of the receptors are organized in nanosized domains randomly distributed on the cell membrane. Intensity-size correlation analysis revealed remarkable heterogeneity in the molecular packing density of the domains. Furthermore, we have mapped the intermolecular organization within a dense cluster by means of sequential NSOM imaging combined with discrete single-molecule photobleaching. In this way we have determined the spatial coordinates of 13 different individual dyes, with a localization accuracy of 6 nm. Our experimental observations are all consistent with an arrangement of DC-SIGN designed to maximize its chances of binding to a wide range of microorganisms. Our data also illustrate the potential of NSOM as an ultrasensitive, high-resolution technique to probe nanometer-scale organization of molecules on the cell membrane. 相似文献
18.
N-Alkyl-N-nitrosoamides, RCON(NO)R′, react with primary aliphatic amines (NH2R″), in refluxing dichloromethane or at room temperature, to give RCONHR″ in 65–98% yields. 相似文献
19.
20.
R. C. Heaton W. A. Taylor D. R. Phillips Sr. D. J. Jamriska J. B. Garcia 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(2):271-277
Zinc oxide targets irradiated with high energy protons at the Los Alamos Meson Physics Facility (LAMPF) contain a number of radioactive spallation products in quantities large enough to warrant recovery. This paper describes methods for recovering7Be,46Sc, and48V from such targets and offers suggestions on possible ways to recover additional isotopes. The proposed methods are based on traditional precipitation and ion exchange techniques, are readily adaptable to hot cell use, and produce no hazardous waste components. The products are obtained in moderate to high yields and have excellent radionuclidic purity. 相似文献