全文获取类型
收费全文 | 5186篇 |
免费 | 625篇 |
国内免费 | 1篇 |
专业分类
5812篇 |
出版年
2021年 | 51篇 |
2018年 | 62篇 |
2017年 | 51篇 |
2016年 | 92篇 |
2015年 | 156篇 |
2014年 | 157篇 |
2013年 | 202篇 |
2012年 | 223篇 |
2011年 | 237篇 |
2010年 | 149篇 |
2009年 | 129篇 |
2008年 | 185篇 |
2007年 | 163篇 |
2006年 | 183篇 |
2005年 | 155篇 |
2004年 | 151篇 |
2003年 | 124篇 |
2002年 | 184篇 |
2001年 | 170篇 |
2000年 | 159篇 |
1999年 | 148篇 |
1998年 | 68篇 |
1997年 | 45篇 |
1996年 | 62篇 |
1995年 | 82篇 |
1994年 | 59篇 |
1993年 | 72篇 |
1992年 | 134篇 |
1991年 | 117篇 |
1990年 | 137篇 |
1989年 | 98篇 |
1988年 | 119篇 |
1987年 | 109篇 |
1986年 | 91篇 |
1985年 | 100篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 76篇 |
1981年 | 73篇 |
1980年 | 67篇 |
1979年 | 95篇 |
1978年 | 91篇 |
1977年 | 67篇 |
1976年 | 64篇 |
1975年 | 56篇 |
1973年 | 49篇 |
1972年 | 58篇 |
1971年 | 50篇 |
1968年 | 40篇 |
1967年 | 43篇 |
排序方式: 共有5812条查询结果,搜索用时 6 毫秒
951.
Relative and absolute changes in skin collagen mass in the rat 总被引:1,自引:0,他引:1
952.
953.
954.
Comparison of Antistreptolysin O Latex Screening Test with the Antistreptolysin O Hemolytic Test 总被引:1,自引:0,他引:1 下载免费PDF全文
This report describes a comparison of the Behringwerke antistreptolysin O (ASO) latex screening test with the ASO hemolytic test. Agreement between the two tests was poor when Difco streptolysin O (SLO) reagent was employed in the hemolytic test; approximately 34% of the sera with ASO titers in the normal range of the hemolytic test gave false-positive latex test reactions. However, the percentage of false-positive latex test reactions was only 5% when Behringwerke SLO reagent was used in the hemolytic test. An assay of the Difco and Behringwerke SLO reagents against an ASO standard indicated that the Difco SLO reagent was more potent than the Behringwerke SLO reagent. The lack of agreement between the Behringwerke latex test and the hemolytic test using Difco SLO reagent is attributed to the potency of the SLO reagents. 相似文献
955.
Spectral quality influence of light during development of Arabidopsis thaliana plants in regulating seed germination 总被引:1,自引:0,他引:1
During development of Arabidopsis thaliana plants, the spectralquality of light can influence the phytochrome controlled germinationof the progeny. Plants grown under light rich in far red energiesproduce light requiring seed that contain phytochrome in thered absorbing or inactive form. Plants grown under light deficientin far red energies produce dark germinating seed that containphytochrome converted mainly to the far red absorbing or activeform. These responses are determined locally within the developingseed without influence from the vegetative portion of the plant.The developing seed is sensitive to spectral changes throughoutembryogenesis until the seed begins to dehydrate just beforefull maturation. At that point the phytochrome is stabilizedin the form photoinduced before dehydration. In relation tothe induction of phytochrome controlled germination responses,the developing seed appears to act independently of the parentplant. (Received April 16, 1974; ) 相似文献
956.
N E Morton D Klein I E Hussels P Dodinval A Todorov R Lew S Yee 《American journal of human genetics》1973,25(4):347-361
957.
Near-ultraviolet and visible radiations increased the duration of the mitotic cycle in excised pea root meristems primarily by lengthening the duration of the pre-DNA synthetic period (G1). All radiations tested shortened the duration of the post-DNA synthetic period (G2). The most pronounced effects were exhibited by green radiation, which lengthened the duration of the cell cycle, G1, DNA synthesis (S), and mitosis (M), and shortened the duration of G2. Progression of cells arrested by starvation in G1 and G2 into DNA synthesis and mitosis was also affected by light treatments. Green radiation appeared to arrest a group of cells in DNA synthesis as well as in G1 and G2. Meristems receiving green and near-ultraviolet radiations exhibited the most rapid progression of G1 cells through S and G2. 相似文献
958.
R. E. Bensinger D. C. Klein Joan L. Weller W. Lovenberg 《Journal of neurochemistry》1974,23(1):111-117
Abstract— A new method is described for the analysis of total tryptophan hydroxylation by intact tissue in culture. This method differs from classical measurements of tryptophan hydroxylase because it allows the detection of changes in tryptophan hydroxylation due to alterations in tryptophan transport, cofactor regeneration and protein synthesis. The rat pineal gland was studied. It was found to hydroxylate tryptophan linearly for a 48-h period. A direct proportional relationship between the concentration of tryptophan in the culture medium and the amount of tryptophan hydroxylated persists between 0.05 and 0.5 m m . As the medium concn of tryptophan is increased above 0.5 m m the amount of tryptophan hydroxylated decreases. Tryptophan hydroxylation is substantially inhibited by 1 m m p-chlorophenylalanine and 0.03 m m cycloheximide. No difference in the total amount of tryptophan hydroxylated was detected between male and female rat pineal glands, between chronically denervated and normal rat pineal glands, or between control glands and glands treated with 0.1-0.001 m m norepinephrine, 0.01 m m isoproterenol, or 0.01 m m mescaline. 相似文献
959.
M. E. Stoeckel H. D. Dellmann A. Porte M. J. Klein F. Stutinsky 《Cell and tissue research》1973,136(1):97-110
Summary In the mouse, the rostral zone of the pars intermedia is almost exclusively composed of typical corticotrophic cells. They are located around and even within the neural stalk, at the level of transition between stalk and neural lobe. In the rat, the corticotrophic cells of the rostral zone are found in scattered islets among the MSH producing cells, and also in the neural lobe. In both the rat and mouse, these cells are in direct contact with various types of nerve terminals. Synaptoid contacts with aminergic and neurosecretory nerve fibers are observed. Furthermore they are also closely related to the hypophysial portal vessels. Following adrenalectomy, the cells located in the neurohypophysis always react more intensely than tose in the rostral zone. The functional significance of these corticotrophic cells which are subject to both humoral and neural regulation remains as yet hypothetical. Their participation in neurogenic stress response seems probable. 相似文献
960.