全文获取类型
收费全文 | 6105篇 |
免费 | 1009篇 |
国内免费 | 521篇 |
专业分类
化学 | 2360篇 |
晶体学 | 78篇 |
力学 | 1163篇 |
综合类 | 149篇 |
数学 | 1201篇 |
物理学 | 2684篇 |
出版年
2024年 | 24篇 |
2023年 | 112篇 |
2022年 | 274篇 |
2021年 | 325篇 |
2020年 | 254篇 |
2019年 | 198篇 |
2018年 | 160篇 |
2017年 | 233篇 |
2016年 | 303篇 |
2015年 | 210篇 |
2014年 | 279篇 |
2013年 | 456篇 |
2012年 | 329篇 |
2011年 | 298篇 |
2010年 | 278篇 |
2009年 | 376篇 |
2008年 | 375篇 |
2007年 | 371篇 |
2006年 | 334篇 |
2005年 | 285篇 |
2004年 | 280篇 |
2003年 | 264篇 |
2002年 | 226篇 |
2001年 | 218篇 |
2000年 | 185篇 |
1999年 | 164篇 |
1998年 | 156篇 |
1997年 | 129篇 |
1996年 | 114篇 |
1995年 | 94篇 |
1994年 | 57篇 |
1993年 | 50篇 |
1992年 | 39篇 |
1991年 | 30篇 |
1990年 | 35篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1971年 | 5篇 |
1959年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有7635条查询结果,搜索用时 328 毫秒
91.
92.
93.
Simulation of aerated lagoon using artificial neural networks and multivariate regression techniques
Karla Patricia Oliveira-Esquerre Aline C. da Costa Roy Edward Bruns Milton Mori 《Applied biochemistry and biotechnology》2003,106(1-3):437-449
The aim of this study was to develop an empirical model that provides accurate predictions of the biochemical oxygen demand
of the output stream from the aerated lagoon at International Paper of Brazil, one of the major pulp and paper plants in Brazil.
Predictive models were calculated from functional link neural networks (FLNNs), multiple linear regression, principal components
regression, and partial least-squares regression (PLSR). Improvement in FLNN modeling capability was observed when the data
were preprocessed using the PLSR technique. PLSR also proved to be a powerful linear regression technique for this problem,
which presents operational data limitations. 相似文献
94.
There are many organic pollutants in the environment, such as polychlorinated biphenyl, polycyclic aromatic hydrocarbons, dichlorodiphenyl-trichloroethane (DDT), and polychlorinated naphthalene. These organic pollutants are persistent,liposoluble and easily cumulated in organism; consequently, the potential toxicity will be high. Risk assessment of industrial chemicals is currently carried out using scanty experimental data, because many of these chemicals have very little or no test data. S… 相似文献
95.
Chemical reactions occurring at the mineral–water interface are controlled by an interfacial layer, nanometers thick, whose properties may deviate from those of the respective bulk mineral and water phases. The molecular-scale structure of this interfacial layer, however, is poorly constrained, and correlations between macroscopic phenomena and molecular-scale processes remain speculative. The application of high-resolution X-ray scattering techniques has begun to provide substantial new insights into the molecular-scale structure of the mineral–water interface. In this review, we describe the characteristics of synchrotron-based X-ray scattering techniques that make them uniquely powerful probes of mineral–water interfacial structures and discuss the new insights that have been derived from their application. In particular, we focus on efforts to understand the structure and distribution of interfacial water as well as their dependence on substrate properties for major mineral classes including oxides, carbonates, sulfates, phosphates, silicates, halides and chromates. We compare these X-ray scattering results with those from other structural and spectroscopic techniques and integrate these to provide a conceptual framework upon which to base an understanding of the systematic variation of mineral–water interfacial structures. 相似文献
96.
碳氟链与碳氢链表面活性剂在固液界面上的吸附 总被引:1,自引:0,他引:1
全氟辛酸及其钠盐和十二烷基硫酸钠在R972上的吸附等温线均为S型或LS型,指示固液界面吸附过程中有表面疏水缔合物生成.碳氟表面活性剂的饱和吸附量显著高于碳氢表面活性剂的饱和吸附量.加电解质于液相使各体系吸附量上升.对于碳氟表面活性剂,甚至引起吸附等温线类型变化.例如,不加电解质时全氟辛酸在R972上的吸附等温线为S型,而加入HCl(c=0.05mol·dm-3)使吸附等混线变成LS型.全氟辛酸比全氟辛酸钠在R972上的吸附更强.几种表面活性剂在R972上的吸附均随温度升高而减少。应用两阶段吸附模型及通用吸附等温线公式可以很好地解释所得实验结果. 相似文献
97.
Zhengbin Zhang Liansheng Liu Hongbin Zhao Youjun Fu Fengyun Cheng Weihong Zhao 《中国科学B辑(英文版)》1997,40(4):353-364
A new method for the study of ternary surface complexes at liquid-solid interface, theE(%) -pH curve method, was proposed. Four types ofE(%)-pH curves, namely, phenomenon of left-right shifts of S-shaped curve, V-shaped curve, monodirection shift curve and X-shaped
curve, were discovered. Correspondingly, apart from type (I) ternary surface complex
and type (II) ternary surface complex
, a new type of ternary surface complex
was discovered.
Project supported by the National Natural Science Foundation of China and the Fund of Doctoral Degree’s Spot. 相似文献
98.
Direct CI mass spectrometry profiling of fatty acid methyl esters (FAMEs) from in situ thermal hydrolysis/methylation (THM) of whole bacterial cells with tetramethylammonium hydroxide (TMAH) has been demonstrated as a potential method for real time and fieldable detection/identification of microorganisms. Bacillus anthracis (Ames), Yersinia pestis (Nair. Kenya), Vibrio cholerae (E1 Tor), Brucella melitensis (Abortus wild) and Francisella tularensis (LVS vaccine) were profiled by this method during a 10-month period. Repeatability of the in situ FAME data was calculated using one-way analysis of variance (ANOVA) and a t-test. Artificial neural network (ANN) and multivariate statistics of the FAME profiles were also compared for bacterial identification/classification. Equivalent results were obtained with a multivariate rule building expert system (MuRES) and the ANN. However, the ANN analysis required much less computer time and was deemed the best choice for this application. In situ THM FAME profiles of the bacterial samples provided comparable results with those obtained from the Microbial Identification System (MIDI) (Newark, DE) wet chemistry-gas chromatographic based system. 相似文献
99.
Alexander S. Bondarenko Genady A. Ragoisha 《Journal of Solid State Electrochemistry》2005,9(12):845-849
Potentiodynamic electrochemical impedance spectroscopy provides extraction of potential-dependent space charge layer capacitance
from potentiodynamic impedance spectra of non-stationary semiconductor–electrolyte interface. The new technique has been applied
for acquisition of Mott-Schottky plots of cathodically treated TiO2 anodic films. Cathodic treatment in 1 M H2SO4 increases donor density and flat band potential of TiO2. Freshly doped films show hysteresis in the space charge layer capacitance in cyclic potential scans. The subsequent cycling
eliminates the hysteresis but preserves the greater part of the doping effect.
Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16 March 2005 相似文献
100.
MinNaYAO YaoQunLI 《中国化学快报》2004,15(1):109-111
Total imernal reflection fluorescence spectroscopy (TIRF) and synchronous scanning technique were combined to study the adsorption behavior of the meso-tetrakis (4-sulfonatophenyl)porphyrin (TPPS) at the glass-water interface without any surfactant. The pH dependence of synchronous fluorescence signal at the interface was analyzed. Both unprotonated (TPPS^4-) and diprotonated (H2TPPS^2-) forms of TPPS were observed at the interface. But the interface favored the adsorption of. The apparent estimated pKa2 value shifted from 5.00 in the bulk solution to 2.7 at the interface. STIRF provides a good technique to study multi-component systems at the interface. 相似文献