全文获取类型
收费全文 | 4452篇 |
免费 | 100篇 |
国内免费 | 17篇 |
专业分类
化学 | 3158篇 |
晶体学 | 45篇 |
力学 | 104篇 |
数学 | 196篇 |
物理学 | 1066篇 |
出版年
2022年 | 26篇 |
2021年 | 45篇 |
2020年 | 39篇 |
2019年 | 44篇 |
2018年 | 34篇 |
2017年 | 31篇 |
2016年 | 75篇 |
2015年 | 76篇 |
2014年 | 86篇 |
2013年 | 200篇 |
2012年 | 224篇 |
2011年 | 260篇 |
2010年 | 137篇 |
2009年 | 116篇 |
2008年 | 225篇 |
2007年 | 208篇 |
2006年 | 228篇 |
2005年 | 205篇 |
2004年 | 209篇 |
2003年 | 189篇 |
2002年 | 209篇 |
2001年 | 137篇 |
2000年 | 120篇 |
1999年 | 79篇 |
1998年 | 61篇 |
1997年 | 61篇 |
1996年 | 61篇 |
1995年 | 48篇 |
1994年 | 59篇 |
1993年 | 59篇 |
1992年 | 64篇 |
1991年 | 42篇 |
1990年 | 45篇 |
1989年 | 50篇 |
1988年 | 41篇 |
1987年 | 42篇 |
1986年 | 42篇 |
1985年 | 84篇 |
1984年 | 81篇 |
1983年 | 26篇 |
1982年 | 39篇 |
1981年 | 35篇 |
1980年 | 41篇 |
1979年 | 68篇 |
1978年 | 46篇 |
1977年 | 56篇 |
1976年 | 49篇 |
1975年 | 31篇 |
1974年 | 24篇 |
1973年 | 18篇 |
排序方式: 共有4569条查询结果,搜索用时 9 毫秒
991.
992.
993.
994.
When the photoscintillo-roentgenography is used for relating the scintigram of internal organs to the anatomic structures, this method is found to have some defects--the difference of magnification between the emission scan and the roentgenogram, the inaccuracy due to the geometric distortion of the X-ray image, the impossibility of the simultaneous photographing of the scan and the X-rays, etc. Then, to diminish the influence of these defects we improved on the photographic recording system of a dual-heal scanner, and made use of the transmission scanning method. That is, we combined the recording parts, Ch1 and Ch2, into one system, using Ch1 for the light source of transmission scan and Ch2 for that of emission scan. In this way, we managed to make the two incident rays from those light sources converge into a focus upon a film. Thus we could perform a simultaneous emission-transmission scanning, by moving, at the same time in the same direction, the scanning detector over the patient and the small radioactive source (241Am) under him. This method can be applied to any radioactive nuclide to be used in transmission scanning and emission scanning. As the result of applying this method clinically in our department, the method has proved to be very useful for anatomic localization. 相似文献
995.
996.
Ch. He E. Hamada T. Suzuki H. Kobayashi K. Kondo V. P. Shantarovich Y. Ito 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):431-435
A new pulsed mono-energetic slow positron beam as well as the conventional positron annihilation lifetime spectroscopy (PALS) have been applied to study the sub-surface and the bulk of epoxy polymer. Significant changes of o-Ps parameters were found at a short distance from the surface. The lifetime of o-Ps was observed to decrease with increasing the positron implantation depth, while its intensity increased. The temperature effect on o-Ps parameters at sub-surface was also investigated. The glass transition temperature for the sub-surface was lower than that for the bulk. Furthermore, the thermal expansion coefficient of the sub-surface was found smaller than that of the bulk. 相似文献
997.
C Danyoshi Y Terao K Achiwa H Okumura T Kurihara A Matsuura F Kobayashi 《Chemical & pharmaceutical bulletin》1989,37(7):1969-1970
Newly synthesized pyrrolidine derivatives inhibited rabbit platelet aggregation induced by platelet activating factor. 相似文献
998.
Two antibody method of aldosterone RIA kit was investigated. This kit was measured directly without extracting the aldosterone. On fundamental studies, stability of standard curve, reproductivity, recovery test and dilution test were obtained good results. On clinical studies, the diurnal variation of serum aldosterone concentration in normal child and adult was correlated well to that of concentration of cortisol and ACTH. The concentration of three hormones was the highest in the early morning and it was the lowest in midnight. 相似文献
999.
Abstract— The singlet oxygen mechanism was evaluated in terms of acridine orange-sensitized induction of gene conversion in Saccharomyces at 470 nm and by using a concentration dependent protective action of added N;. The singlet oxygen mechanism accounted for 96% of the total photodynamic efTect. This value is to be contrasted with 76% previously observed for 510 nm illumination. 相似文献
1000.