全文获取类型
收费全文 | 1148篇 |
免费 | 44篇 |
国内免费 | 1篇 |
专业分类
化学 | 840篇 |
晶体学 | 10篇 |
力学 | 36篇 |
数学 | 156篇 |
物理学 | 151篇 |
出版年
2023年 | 9篇 |
2022年 | 14篇 |
2021年 | 15篇 |
2020年 | 39篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 27篇 |
2015年 | 32篇 |
2014年 | 19篇 |
2013年 | 52篇 |
2012年 | 58篇 |
2011年 | 76篇 |
2010年 | 34篇 |
2009年 | 47篇 |
2008年 | 68篇 |
2007年 | 61篇 |
2006年 | 48篇 |
2005年 | 64篇 |
2004年 | 51篇 |
2003年 | 42篇 |
2002年 | 42篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 24篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1193条查询结果,搜索用时 171 毫秒
131.
Peter J. Cameron 《Mathematische Zeitschrift》1977,157(2):101-119
132.
We give some new representations of the partial geometry pg(6, 6, 2), which was constructed by van Lint and Schrijver, show a connection with a strongly regular graph based on the ternary Golay code, and determine the automorphism group of the geometry. 相似文献
133.
Nucleophilic displacement of halide from 2-halo 1,4-quinones occurs at the carbon or at the carbon vicinal to it depending on the nature of the nucleophile and the solvent. 相似文献
134.
The construction and convergence of high-order product integration methods for the second-kind Abel equation are discussed and the results of De Hoog and Weiss are generalised. Backward difference methods are introduced, and numerical results are presented which verify the theoretical rates of convergence. 相似文献
135.
Analysis of the CHS and CHCl multiplets in the 13C NMR spectra of modified polymers indicates that the addition of benzenesulphenyl chloride to cis-1,4-polybutadiene is not wholly random. The analysis of the methylene resonances was inconclusive because of peak overlap and other uncertainties. The conclusion that the partially saturated polymers have some blocky character is in general agreement with earlier results on the physical properties of the adducts and on the kinetics of the addition reaction. 相似文献
136.
To help understand which tissue parameters best account for the water proton NMR relaxation times, the longitudinal relaxation time (T2), the transverse relaxation time (T2), and the water content of 16 tissues from normal adult rats were measured at 10.7 MHz and 29°C. Regression analyses between the above and other tissue parameters were performed. These other tissue parameters included: the amounts of various organic and inorganic components, protein synthetic rate, oxygen consumption rate, and morphological composition. In addition, the differences in T1, T2, and water content values between normal liver and malignant tumor (Morris #7777 a transplantable hepatoma) were studied to help understand how a disease state can be detected and characterized by NMR spectroscopy. The results of this study and information from the literature allow the following generalizations to be made about tissue T1 and T2 values: (1) Each normal tissue has rather consistent and characteristic T1 and T2 relaxation times which are always shorter than the T1 and T2 of bulk water; (2) tissues with higher water content tend to have longer T1 relaxation times; (3) tissue T2 values are not, however, as well correlated with water content as T1 values; (4) tissues with shorter T1 values have higher calculated hydration fractions, greater amounts of rough endoplasmic reticulum, and a greater rate of protein synthetic activity; (5) tissues with higher lipid content, associated with intracellular non-membrane bounded lipid droplets, tend to have longer T2 values; (6) tissues with greater overall surface area, whether in the form of cellular membranes or intracellular or extracellular fibrillar macromolecules, tend to have shorter T2 values; (7) the differences between T1 and T2 values between tumor and normal tissues correlated with differences in the volume fraction (amounts) of extracellular fluid volumes and in the amounts of membrane and fibrillar surface area in the cells. The above generalizations should be useful in predicting T1 and T2 changes associated with specific tissue pathologies. 相似文献
137.
138.
139.
140.
A. T. Bullock G. G. Cameron P. M. Smith 《Journal of Polymer Science.Polymer Physics》1973,11(7):1263-1269
Shape changes in the electron spin resonance spectrum of spin-labeled polystyrene have been studied as a function of temperature in the range 77–340°K. Rotational correlation times have been calculated by using recent theories of slow-motional effects on ESR spectra. Three models were used, namely, Brownian, moderate jump diffusion, and large jump diffusion. The moderate jump model gave correlation times in good accord with those found by other techniques for the δ relaxation in polystyrene. The relaxation was found to be independent of molecular weight. 相似文献