全文获取类型
收费全文 | 1579篇 |
免费 | 29篇 |
国内免费 | 6篇 |
专业分类
化学 | 982篇 |
晶体学 | 8篇 |
力学 | 60篇 |
数学 | 87篇 |
物理学 | 477篇 |
出版年
2020年 | 19篇 |
2019年 | 15篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 33篇 |
2013年 | 64篇 |
2012年 | 43篇 |
2011年 | 68篇 |
2010年 | 49篇 |
2009年 | 35篇 |
2008年 | 63篇 |
2007年 | 43篇 |
2006年 | 54篇 |
2005年 | 29篇 |
2004年 | 39篇 |
2003年 | 23篇 |
2002年 | 45篇 |
2001年 | 42篇 |
2000年 | 40篇 |
1999年 | 37篇 |
1998年 | 25篇 |
1997年 | 26篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 35篇 |
1992年 | 32篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 26篇 |
1988年 | 20篇 |
1987年 | 27篇 |
1986年 | 14篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 31篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 16篇 |
1976年 | 20篇 |
1975年 | 15篇 |
1974年 | 20篇 |
1973年 | 23篇 |
1970年 | 19篇 |
1969年 | 18篇 |
1968年 | 14篇 |
1967年 | 16篇 |
排序方式: 共有1614条查询结果,搜索用时 46 毫秒
111.
A treatment of sites appropriate to fluid percolation in bond controlled processes results in sensitivity of breakup of the defender to the degree of size-correlation for three-dimensional networks. In strongly correlated lattices network control of invasion yields to a statistical treatment as a result of improved accessibility. 相似文献
112.
113.
Wai Kuan Foong Angus R. Simpson Holger R. Maier Stephen Stolp 《Annals of Operations Research》2008,159(1):433-450
A number of algorithms have been developed for the optimization of power plant maintenance schedules. However, the true test
of such algorithms occurs when they are applied to real systems. In this paper, the application of an Ant Colony Optimization
formulation to a hydropower system is presented. The formulation is found to be effective in handling various constraints
commonly encountered in practice. Overall, the results obtained using the ACO formulation are better than those given by traditional
methods using engineering judgment, which indicates the potential of ACO in solving realistic power plant maintenance scheduling
problems. 相似文献
114.
Christian Otto Rupert Scheidl Franz Menzinger Ernst J. Maier Erwin Capek Otto Scheidl Christian W. Huck 《Chromatographia》2009,69(11-12):1181-1188
The first simultaneous quantification of neomycin and bacitracin using liquid chromatography evaporative light scattering detection as an alternative to MS detection and pre-/post-column derivatisation, respectively, was the aim of this study. The developed method was validated for two strength of neomycin and one strength of bacitracin in sterile pharmaceutical formulation and is a fast and efficient tool for content uniformity tests in quality control. With this method the separation of neomycin from sulfate and the base line separation of the four major components of bacitracin (bacitracin A, B1, B2 and B3) was achieved. These four components are responsible for 96% of the microbiological activity. A Phenomenex Synergi POLAR analytical column (250 mm × 4.6 mm, 4 μm I.D.) in combination with 0.5% perfluoropropionic acid and acetonitrile in gradient mode, the peaks of interest could be separated with high efficiency within 14 min. The calibration was performed using a second order regression with an R 2 = 0.9999 for neomycin (B and C) sulfate and R 2 = 0.9996 for bacitracin A, B1, B2 and B3. The results of the accuracy evaluation were 99.2 and 99.7%, respectively, for neomycin and 100.8% for bacitracin. Injection precision results are 0.4–1.5 RSD% recorded for six injections. The established method has a high potential for routine high-throughput analyses in the pharmaceutical industry. 相似文献
115.
O. N. Chaikovskaya I. V. Sokolova E. A. Karetnikova G. V. Maier 《Journal of Applied Spectroscopy》2008,75(2):261-267
We have used fluorescence spectroscopy to study photoinduced biodegradation of ortho-cresol, para-cresol and mixture of them
in water when excited by different UV radiation sources. We show that the efficiency of photolysis for both the individual
isomers and the mixture of cresols is higher for excitation by radiation at λ ∼ 222 nm. Pre-irradiation of aqueous cresol
solutions slows down subsequent biodegradation. Using a combination of UV irradiation and the strain Penicillium tardum H-2
for utilization of the cresol mixture led to complete degradation of para-cresol and partial degradation of ortho-cresol.
Spectral and chromatographic study of the qualitative composition of the metabolites formed during biodegradation of para-cresol
showed that preparatory metabolism of such compounds occurs both through oxidation of the methyl group with formation of 4-hydroxybenzoic
acid and through hydroxylation with formation of 4-methylcatechol.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 250–255, March–April, 2008. 相似文献
116.
117.
118.
H. Schmalfuß H. Werner G. Curli T. P. Hilditch H. E. Longenecker Fr. Kiermeier Fr. X. Maier C. I. Kruisheer P. C. den Herder G. Roeder B. Segal A. Romeo V. Crupi G. Dorta G. Lunde H. Kringstad E. Mathiesen A. Olsen F. N. Woodward S. R. Hoover S. Schmidt-Nielsen und J. Stone 《Fresenius' Journal of Analytical Chemistry》1941,121(1-2):55-59
Ohne Zusammenfassung 相似文献
119.
120.
Göbel MC Gregori G Guo X Maier J 《Physical chemistry chemical physics : PCCP》2010,12(42):14351-14361
Thin films of CeO(2) (both nominally pure and 10 mol% gadolinium-doped) grown via pulsed-laser deposition were studied. The electrical conductivity of the samples was measured as a function of thickness, temperature and oxygen partial pressure (pO(2)) using impedance spectroscopy. As expected, undoped CeO(2) exhibits electronic conductivity (with activation energy between 1.4 and 1.6 eV) whereas the highly doped samples are oxygen vacancy conductors (activation energy around 0.7 eV for epitaxial films). In order to investigate the influence of the nature of the substrate the thin films were grown on two different substrates, Al(2)O(3) (0001) and SiO(2) (0001), and compared. While the films grown on SiO(2) exhibit a microstructure characterized by columnar grains, the films grown on Al(2)O(3) are epitaxial. Notably, for films on both substrates the conductivity and activation energy vary with film thickness and exhibit remarkable differences when the films on different substrates are compared. In the case of the polycrystalline films (SiO(2) substrate), the space charge layer effects of the grain boundaries dominate over the substrate-film interface effect. In the case of the epitaxial films (Al(2)O(3) substrate), a small interface effect, probably due to a space charge layer or structural strain, is observed. 相似文献