全文获取类型
收费全文 | 8856篇 |
免费 | 795篇 |
国内免费 | 6篇 |
专业分类
9657篇 |
出版年
2022年 | 70篇 |
2021年 | 125篇 |
2020年 | 86篇 |
2019年 | 91篇 |
2018年 | 128篇 |
2017年 | 128篇 |
2016年 | 192篇 |
2015年 | 323篇 |
2014年 | 357篇 |
2013年 | 405篇 |
2012年 | 507篇 |
2011年 | 494篇 |
2010年 | 326篇 |
2009年 | 320篇 |
2008年 | 472篇 |
2007年 | 481篇 |
2006年 | 404篇 |
2005年 | 414篇 |
2004年 | 389篇 |
2003年 | 372篇 |
2002年 | 371篇 |
2001年 | 197篇 |
2000年 | 206篇 |
1999年 | 190篇 |
1998年 | 126篇 |
1997年 | 111篇 |
1996年 | 100篇 |
1995年 | 76篇 |
1994年 | 80篇 |
1993年 | 66篇 |
1992年 | 119篇 |
1991年 | 108篇 |
1990年 | 126篇 |
1989年 | 95篇 |
1988年 | 89篇 |
1987年 | 78篇 |
1986年 | 78篇 |
1985年 | 94篇 |
1984年 | 69篇 |
1983年 | 55篇 |
1982年 | 74篇 |
1981年 | 55篇 |
1980年 | 61篇 |
1979年 | 87篇 |
1978年 | 62篇 |
1977年 | 50篇 |
1975年 | 55篇 |
1974年 | 62篇 |
1973年 | 48篇 |
1968年 | 50篇 |
排序方式: 共有9657条查询结果,搜索用时 6 毫秒
1.
2.
3.
Cultured astrocytes from a syncytium after maturation 总被引:2,自引:0,他引:2
The formation of functional gap junctions between astrocytes was investigated during differentiation of these cells in culture. Precursor cells of GFA (glial fibrillary acidic) protein-positive astrocytes were cultured in a chemically defined medium as a homogeneous population. These cells were rarely coupled to one neighbour, as revealed by electrical and dye coupling and never formed a large syncytium, as investigated by injection and spread of Lucifer Yellow. Differentiation with respect to GFA protein accumulation can be induced in these cells by culturing in horse serum-containing medium. The formation of functional junctions developed within 2 weeks in about 20% of the cells. Coupled cells formed a large syncytium. When the astrocytes were co-cultured with primary cerebellar cells (consisting predominantly of small neurons) after the switch to serum-containing medium the percentage of coupled astrocytes increased to about 65%. Again the coupled cells formed a large syncytium. Since no physical contact was possible between the astrocyte cultures and the primary cerebellar cells the stimulation of coupling had to be signalized by soluble factor(s). 相似文献
4.
Synthesis of intrathecal interferon in systemic lupus erythematosus with neurological complications.
Intrathecal synthesis of interferon in the absence of viral or bacterial infection was detected during the occurrence of neurological complications in two patients with systemic lupus erythematosus. The interferons displayed characteristics similar to those observed in the sera of patients with the disease. No interferon inducing activity was detected in the cerebrospinal fluid or serum of the two patients. These observations support the hypothesis of a localised mechanism of interferon induction in systemic lupus erythematosus which includes the interaction of lymphocytes with damaged tissues. 相似文献
5.
6.
7.
Harald Tichy 《Journal of morphology》1987,193(2):159-171
On the antennal tip of Eurypauropus ornatus are 3 threadlike sensilla—the flagella, and a single spheroid sensillum—the globulus. Each of the 3 flagella is innervated by 2 groups of sensory cells. One group contains 4 cells, the other, 5. All cells of the “four group” and 3 of the “five group” are comprised of single cilia and unbranched dendrites which extend along the lumen of the flagellum. Two cells of the “five group” have double cilia and pairs of unbranched dendrites. One pair also enters the flagellum and the other pair terminates beneath the flagellar base to form a concentric array of lamellae. No pores are present in the cuticular wall. Eight sensory cells innervate the globulus. They are arranged in 3 groups, one triplet and 2 pairs, in addition to a single cell. The single cell contains a pair of cilia whose unbranched dendrites differentiate into tubular bodies that are inserted into the base of the globulus. Each of the other 7 sensory cells has a single cilium. Their unbranched dendrites penetrate into the globulus in 3 groups as described for the sensory cells. The dendrites in each group terminate in an individual pore channel at the globulus tip and completely fuse with the electron-dense material that plugs the pore channel. Based on structural similarities to sensilla having known functions, it is probable that the flagella and the globulus are chemoreceptors, the former responding to odors, the latter sensitive to substances in aqueous solution. 相似文献
8.
9.
10.
Chloragogen cells, subserving ion exchange and electron accepting functions, were studied in Tubifex tubifex after insecticide treatment. Chloragogen cells were strongly influenced by in vivo carbofuran poisoning. The first alterations in the chloragogen cells became activated, both the formation and release of the chloragosomes reached a high rate. The released chloragosomes were phagocytosed by the amoebocytes. At an advanced stage of the toxication a heavy loading of the apical cytoplasm of chloragogen cells with lipid droplets, finally degenerative changes both in the chloragogen cells and amoebocytes were observed. Possible mechanisms of the carbofuran toxication and of the protective function of chloragogen cells in T. tubifex are discussed. 相似文献