全文获取类型
收费全文 | 5864篇 |
免费 | 511篇 |
国内免费 | 2篇 |
出版年
2022年 | 42篇 |
2021年 | 79篇 |
2020年 | 39篇 |
2019年 | 58篇 |
2018年 | 83篇 |
2017年 | 89篇 |
2016年 | 121篇 |
2015年 | 206篇 |
2014年 | 231篇 |
2013年 | 256篇 |
2012年 | 311篇 |
2011年 | 285篇 |
2010年 | 201篇 |
2009年 | 192篇 |
2008年 | 275篇 |
2007年 | 287篇 |
2006年 | 240篇 |
2005年 | 233篇 |
2004年 | 221篇 |
2003年 | 222篇 |
2002年 | 209篇 |
2001年 | 179篇 |
2000年 | 171篇 |
1999年 | 158篇 |
1998年 | 91篇 |
1997年 | 72篇 |
1996年 | 62篇 |
1995年 | 53篇 |
1994年 | 49篇 |
1993年 | 40篇 |
1992年 | 103篇 |
1991年 | 88篇 |
1990年 | 101篇 |
1989年 | 78篇 |
1988年 | 80篇 |
1987年 | 62篇 |
1986年 | 71篇 |
1985年 | 79篇 |
1984年 | 59篇 |
1983年 | 44篇 |
1982年 | 52篇 |
1980年 | 38篇 |
1979年 | 69篇 |
1978年 | 51篇 |
1977年 | 38篇 |
1975年 | 39篇 |
1974年 | 55篇 |
1973年 | 42篇 |
1969年 | 37篇 |
1968年 | 38篇 |
排序方式: 共有6377条查询结果,搜索用时 15 毫秒
1.
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
2.
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
3.
4.
Rita Padányi Yuning Xiong Géza Antalffy Krisztina Lór Katalin Pászty Emanuel E. Strehler ágnes Enyedi 《The Journal of biological chemistry》2010,285(41):31704-31712
The membrane localization of the plasma membrane Ca2+-ATPase isoform 2 (PMCA2) in polarized cells is determined by alternative splicing; the PMCA2w/b splice variant shows apical localization, whereas the PMCA2z/b and PMCA2x/b variants are mostly basolateral. We previously reported that PMCA2b interacts with the PDZ protein Na+/H+ exchanger regulatory factor 2 (NHERF2), but the role of this interaction for the specific membrane localization of PMCA2 is not known. Here we show that co-expression of NHERF2 greatly enhanced the apical localization of GFP-tagged PMCA2w/b in polarized Madin-Darby canine kidney cells. GFP-PMCA2z/b was also redirected to the apical membrane by NHERF2, whereas GFP-PMCA2x/b remained exclusively basolateral. In the presence of NHERF2, GFP-PMCA2w/b co-localized with the actin-binding protein ezrin even after disruption of the actin cytoskeleton by cytochalasin D or latrunculin B. Surface biotinylation and fluorescence recovery after photobleaching experiments demonstrated that NHERF2-mediated anchorage to the actin cytoskeleton reduced internalization and lateral mobility of the pump. Our results show that the specific interaction with NHERF2 enhances the apical concentration of PMCA2w/b by anchoring the pump to the apical membrane cytoskeleton. The data also suggest that the x/b splice form of PMCA2 contains a dominant lateral targeting signal, whereas the targeting and localization of the z/b form are more flexible and not fully determined by intrinsic sequence features. 相似文献
5.
6.
7.
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
8.
9.
John A. Nyakatura Vivian R. Allen Jonas Laustr?er Amir Andikfar Marek Danczak Hans-Jürgen Ullrich Werner Hufenbach Thomas Martens Martin S. Fischer 《PloS one》2015,10(9)
Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies. 相似文献
10.
Franz Peter Fischer Christina Miltz Ingrid Singer Geoffrey A. Manley 《Journal of morphology》1992,213(2):225-240
The starling cochlea was studied with TEM at four locations along the basilar papilla to investigate gradients in morphological features over the papilla's length and width. Hair cell shape changes continuously from neural to abneural and from basal to apical. Unlike the situation in mammals, there are no distinct populations of hair cells; the previously described types (tall hair cells and short hair cells) are merely extremes in a continuum. Contacts between THC are a normal feature. Except at the base of the papilla, SHC have very large cuticular plates, suggesting a micromechanical function for these cells. In contrast to the THC, the SHC normally completely lack afferent innervation; this indicates that their function is restricted to within the basilar papilla itself. © 1992 Wiley-Liss, Inc. 相似文献