全文获取类型
收费全文 | 194209篇 |
免费 | 3108篇 |
国内免费 | 865篇 |
专业分类
化学 | 107413篇 |
晶体学 | 2649篇 |
力学 | 7993篇 |
综合类 | 11篇 |
数学 | 22014篇 |
物理学 | 58102篇 |
出版年
2021年 | 1464篇 |
2020年 | 1506篇 |
2019年 | 1568篇 |
2018年 | 1576篇 |
2017年 | 1618篇 |
2016年 | 3106篇 |
2015年 | 2592篇 |
2014年 | 3258篇 |
2013年 | 9084篇 |
2012年 | 7658篇 |
2011年 | 9525篇 |
2010年 | 5904篇 |
2009年 | 6019篇 |
2008年 | 8720篇 |
2007年 | 8619篇 |
2006年 | 8232篇 |
2005年 | 7674篇 |
2004年 | 6785篇 |
2003年 | 5833篇 |
2002年 | 5608篇 |
2001年 | 6442篇 |
2000年 | 4948篇 |
1999年 | 3796篇 |
1998年 | 2897篇 |
1997年 | 2883篇 |
1996年 | 2873篇 |
1995年 | 2497篇 |
1994年 | 2410篇 |
1993年 | 2253篇 |
1992年 | 2561篇 |
1991年 | 2482篇 |
1990年 | 2189篇 |
1989年 | 2140篇 |
1988年 | 2153篇 |
1987年 | 2107篇 |
1986年 | 2007篇 |
1985年 | 2918篇 |
1984年 | 2920篇 |
1983年 | 2324篇 |
1982年 | 2512篇 |
1981年 | 2380篇 |
1980年 | 2335篇 |
1979年 | 2257篇 |
1978年 | 2314篇 |
1977年 | 2273篇 |
1976年 | 2194篇 |
1975年 | 2173篇 |
1974年 | 2068篇 |
1973年 | 2168篇 |
1972年 | 1231篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation 总被引:2,自引:0,他引:2
The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's(1) equations as well as the Chen and Evans(2) model were used to correlate the new data. Results are reported and compared to literature data and correlations. 相似文献
993.
G. Teowee J. M. Boulton C. D. Baertlein R. K. Wade D. R. Uhlmann 《Journal of Sol-Gel Science and Technology》1994,2(1-3):623-626
A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model. 相似文献
994.
A. Cerdán Vidal A. R. Maurí Aucejo M. Llobat Estellés C. Pascual Martí J. Simeón Martí 《Fresenius' Journal of Analytical Chemistry》1994,350(12):706-711
The possibility of identification of substances which have similar spectral behaviour by means of Apparent Content Curves has been studied. This study is carried out with absorption, excitation and emission spectra of several amphetamines of widespread pharmaceutical use. Results obtained show that amphetamine, phenylpropanolamine, pseudoephedrine, phenylephrine, epinephrine, dopamine and methoxyamphetamine can be identified with a probability of >95%. 相似文献
995.
J.-J. Sauvain L. F. de Alencastro J. Tarradellas R. Camenzind G. Karlaganis C. Vuilleumier 《Fresenius' Journal of Analytical Chemistry》1994,350(7-9):555-562
The analysis of PCB in transformer oils has been achieved with three HRGC/ECD based methods, proposed by the International Electrotechnical Commission (IEC/TC 10), by the Comité Européen de Normalisation (CEN/TC 19/WG 22) and by the Deutsches Institut für Normung (DIN 51 527). The same clean-up, described in the CEN/TC 19/WG 22, has been used for all the samples, allowing a comparison of the quantification procedure only. The total chlorine content has also been determined with X-ray fluorescence. These different methods of quantification are compared and their application for legislative purposes is discussed.Dedicated to Professor Dr Dieter Klockow on the occasion of his 60th birthday 相似文献
996.
In this paper we show that the director profile of a low pre-tilt surface stabilized ferroelectric liquid crystal passes through quasi-static stressed states during domain switching under direct drive conditions. Using polarized stroboscopic microscopy, we have observed two quasi-static transmission levels during a domain switching transition from dark to light. This is a result of the directors reorienting into stressed profiles both before and after the chevron interface has switched. By modelling the interaction between the elastic forces and the torque from the applied field, we have determined these voltage dependent director profiles and, by calculating their corresponding transmissivities, have shown very good agreement with the experimentally observed values. 相似文献
997.
By means of high pressure differential thermal analysis we measured the pressure/temperature phase diagrams of several nematic compounds with different molecular structures. Using pressures up to about 500 M Pa we found strongly nonlinear clearing curves. This behaviour is interpreted as changes from 'weak' intermolecular potentials to 'hard' potentials, or using thermodynarmic arguments, strong pressure dependence of the volume discontinuity at the clearing transitions. 相似文献
998.
In order to obtain a continuous source of mitotic metaphases, gill tissue of Aphaius fasciatus (Pisces, Cyprinodontiformes) has been successfully employed. Results gathered after exposure of fish to R2SnClpenG, R3SnClpenGNa, to the parents R2SnCl2, R3SnCl and to penGNa (penGNa = penicillinGNa; R = methyl, butyl and phenyl) suggest that both the parent organotin (IV) chloride and organotin (IV) chloropenG derivatives are toxic while penGNa exerts no significant toxic activity. Essentially, all of the chromosome abnormalities are classifiable as irregularly staining of chromosomes, breakages, side-arm bridges or pseudochiasmata. 相似文献
999.
Please forward books for review to the book review editor: Magdolna Hargittai, Structural Chemistry Research Group of the Hungarian Academy of Sciences, Eötvös University, H-1431 Budapest, Pf. 117, Hungary 相似文献
1000.
Carbon fibers were coated in situ with a thin film of polyhexamethylene adipamide by an interfacial polycondensation technique. The modified fibers were used for the preparation of epoxy-based unidirectional composites. Specimens of these materials were immersed in water until equilibrium conditions were attained. The weight gain at equilibrium was determined as a function of the immersion temperature, the fiber volume fraction and the polyamide content deposited on the fibers. Water penetration in specimens made with uncoated carbon fibers increases when the volume fraction decreases. Introduction of the polyamide interlayer initially increases the water absorption, but reduces it at higher immersion temperatures and/or higher polyamide contents. The treated specimens were subjected to the short beam test to determine the interlaminar shear strength (ILSS). The data show that the ILSS decreases with water penetration but increases when the immersion temperature increases from 40 to 70°C. The overall performance encountered is discussed in terms of the possible roles of the polyamide interphase while taking into account mechanisms concerned with matrix plasticization, interphase degradation and residual stress relaxation. 相似文献