全文获取类型
收费全文 | 123752篇 |
免费 | 7491篇 |
国内免费 | 13篇 |
专业分类
131256篇 |
出版年
2023年 | 737篇 |
2022年 | 720篇 |
2021年 | 1568篇 |
2020年 | 1429篇 |
2019年 | 1456篇 |
2018年 | 3414篇 |
2017年 | 3042篇 |
2016年 | 4124篇 |
2015年 | 5461篇 |
2014年 | 5586篇 |
2013年 | 7474篇 |
2012年 | 8786篇 |
2011年 | 7824篇 |
2010年 | 5049篇 |
2009年 | 3915篇 |
2008年 | 6348篇 |
2007年 | 6004篇 |
2006年 | 5750篇 |
2005年 | 4951篇 |
2004年 | 4868篇 |
2003年 | 4425篇 |
2002年 | 4039篇 |
2001年 | 2948篇 |
2000年 | 2839篇 |
1999年 | 2202篇 |
1998年 | 1022篇 |
1997年 | 730篇 |
1996年 | 779篇 |
1995年 | 689篇 |
1994年 | 644篇 |
1992年 | 1261篇 |
1991年 | 1132篇 |
1990年 | 1072篇 |
1989年 | 1156篇 |
1988年 | 980篇 |
1987年 | 950篇 |
1986年 | 893篇 |
1985年 | 936篇 |
1984年 | 830篇 |
1983年 | 689篇 |
1982年 | 585篇 |
1979年 | 776篇 |
1978年 | 607篇 |
1975年 | 682篇 |
1974年 | 738篇 |
1973年 | 722篇 |
1972年 | 652篇 |
1970年 | 622篇 |
1969年 | 681篇 |
1968年 | 651篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
A case of translocation D--,t(1p+) 总被引:1,自引:0,他引:1
994.
995.
996.
997.
998.
Summary Exponential phase cultures ofE. coli 15 T- cells growing on glucosemineral medium were supplemented with 2 mM l-cysteine-HCl. The optical density, acid soluble SH (AS-SH) as well as the DNA, RNA, and protein synthesis of the cultures were examined during this treatment and after return to normal growth conditions. Similarly, the survival of cells irradiated by a standard X-ray dose in cysteine-free buffer was measured.The development of radioresistance during the cysteine treatment as well as the loss of this acquired radioresistance after return to normal growth conditions could be divided into two phases: a) an instantaneous and b) a slow change of radioresistance. Phase a seems to be related to the changes occurring in the AS-SH content of the bacteria, while phase b is apparently dependent on the alterations in the synthesis of macromolecules.This work was partly presented at the 6th Annual Meeting of the European Society for Radiation Biology, Interlaken 1968. 相似文献
999.
Summary The authors studied the dependence between the ability of systems regulating the level of peripheral leucocytes to damp the fluctuations of this level, occurring under conditions of repeated stressing of the organism by non-specific stress factors (isolation, starvation, handling for blood withdrawal) and the tolerance of the organism to the action of ionizing radiation (summary exposure to X-rays leading to death at repeated irradiation). This regulatory ability was expressed with the aid of the slope (coefficientb) of regression between the leucocytary valuesx
i, fluctuating in time, and the subsequent differences
i
(
i
=x
i+1–x
i
). The highest tolerance to lethal action of radiation is correlated to such a regulatory behaviour of the organism at which the time necessary for adaptation of the system is shortest. The authors point out the suitability of the employed regulatory characteristic for the quantitative study of adaptability and resistance of the organism and its relatedness to the damping ratio, used in the automatic control theory. 相似文献
1000.
Summary The morphology of postnatal differentiation of the Golgi apparatus, the nucleus, the perikaryon, and the dendrites was studied in Purkinje cells of the rat cerebellum for 30 days after birth using histochemical, histological, and electron microscopic methods.The Golgi apparatus during differentiation undergoes morphological and positional changes. From the 1st to 7th postnatal day, the Golgi apparatus is found in a supranuclear position, and is connected with the axes of differentiating primary dendrites by beam-like processes. From days 8 to 11 this connection disappears, and most of the Golgi apparatus assumes a lateronuclear and infranuclear position. After the 11th or 12th day, the Golgi apparatus is found in perinuclear and peripheral cytoplasmic positions. The formation of granular endoplasmic reticulum occurs in the vicinity of the perinuclear Golgi apparatus. The differentiation of cell and nuclear forms requires approximately 20 days. The morphological changes of differentiation are discussed in relation to the participation of the Golgi apparatus in the differentiation of dendrites and in the formation of the granular endoplasmic reticulum. 相似文献