全文获取类型
收费全文 | 12673篇 |
免费 | 1137篇 |
国内免费 | 742篇 |
出版年
2023年 | 262篇 |
2022年 | 241篇 |
2021年 | 516篇 |
2020年 | 517篇 |
2019年 | 810篇 |
2018年 | 651篇 |
2017年 | 425篇 |
2016年 | 434篇 |
2015年 | 621篇 |
2014年 | 770篇 |
2013年 | 1049篇 |
2012年 | 523篇 |
2011年 | 654篇 |
2010年 | 479篇 |
2009年 | 595篇 |
2008年 | 534篇 |
2007年 | 543篇 |
2006年 | 513篇 |
2005年 | 450篇 |
2004年 | 400篇 |
2003年 | 347篇 |
2002年 | 317篇 |
2001年 | 249篇 |
2000年 | 236篇 |
1999年 | 202篇 |
1998年 | 200篇 |
1997年 | 156篇 |
1996年 | 143篇 |
1995年 | 138篇 |
1994年 | 121篇 |
1993年 | 123篇 |
1992年 | 106篇 |
1991年 | 97篇 |
1990年 | 104篇 |
1989年 | 76篇 |
1988年 | 96篇 |
1987年 | 81篇 |
1986年 | 65篇 |
1985年 | 97篇 |
1984年 | 102篇 |
1983年 | 73篇 |
1982年 | 72篇 |
1981年 | 65篇 |
1980年 | 47篇 |
1979年 | 36篇 |
1978年 | 35篇 |
1977年 | 38篇 |
1975年 | 27篇 |
1974年 | 27篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 498 毫秒
991.
The lethal effect on human cancer cells was studied under three types of treatment: A) an ELF pulsed sinusoidal of 50 Hz electromagnetic field (PEMF) with amplitudes between 10 and 55 mT; B) the field and a cytostatic agent (actinomycin-C); and C) the field, the cytostatic agent, which has a photodynamic effect, and exposure to a halogen lamp. The results show a decreasing vitality of human K-562 and U-937 cancer cells in suspension with each additional treatment. Combination with other parameters as hyperthermia and/or hyperacidity could yield high killing rates by this noninvasive method. 相似文献
992.
Brocard JB Rintoul GL Reynolds IJ 《Biology of the cell / under the auspices of the European Cell Biology Organization》2003,95(5):239-242
Mitochondria are a node of integration for intracellular signaling pathways and their morphology changes seem to be tightly associated with their function. New data show that morphology is one of the parameters involved in mitochondria's choice between promoting cell death and protecting cells against general metabolic jeopardy. 相似文献
993.
Timoshenko AV Gorudko IV Maslakova OV André S Kuwabara I Liu FT Kaltner H Gabius HJ 《Molecular and cellular biochemistry》2003,250(1-2):139-149
Cell surface glycans present docking sites to endogenous lectins. With growing insight into the diversity of lectin families it becomes important to answer the question on the activity profiles of individual family members. Focusing on galectins (-galactoside-binding proteins without Ca2+-requirement sharing the jelly-roll-like folding pattern), this study was performed to assess the potency of proto-type galectins (galectins-1 and -7 and CG-16) and the chimera-type galectin-3 to elicit selected cell responses by carbohydrate-dependent surface binding and compare the results. The galectins, except for galectin-1, were found to enhance detergent (SDS)-induced hemolysis of human erythrocytes to different degrees. Their ability to confer increased membrane osmofragility thus differs. Aggregation of neutrophils, thymocytes and platelets was induced by the proto-type galectin-1 but not -7, by CG-16 and also galectin-3. Cell-type-specific quantitative differences and the importance of the fine-specificity of the galectin were clearly apparent. In order to detect cellular responses based on galectin binding and bridging of cells the formation of haptenic-sugar-resistant (HSR) intercellular contacts (an indicator of post-binding signaling) was monitored. It was elicited by CG-16 and galectin-1 but not galectin-3, revealing another level at which activities of individual galectins can differ. Acting as potent elicitor of neutrophil aggregation, CG-16-dependent post-binding effects were further analyzed. Carbohydrate-dependent binding to the neutrophils' surface led to a sustained increase of cytoplasmic Ca2+ concentration in a dose-dependent manner. The ability of CG-16 to activate H2O2 generation by human peripheral blood neutrophils was primed by the Ca2+-ionophor ionomycin and by cytochalasin B. In a general context, these results emphasize that – besides plant lectins as laboratory tools – animal lectins can trigger cell reaction cascades, implying potential in vivo relevance for the measured activities. Within the family of galectins, the activity profiles depend on the target cell type and the individual galectin. Notably, proto-type galectins do not necessarily share a uniform capacity as elicitor. 相似文献
994.
Eyeing endothelins: A cellular perspective 总被引:6,自引:0,他引:6
Prasanna G Narayan S Krishnamoorthy RR Yorio T 《Molecular and cellular biochemistry》2003,253(1-2):71-88
Endothelin is an endogenous vasoactive peptide that is considered among the most potent vasoconstrictor substances known. In addition to its vascular effects, endothelins and their receptors have been shown to be present in the eye and to have a number of ocular actions that may be important for ocular homeostasis, but, in excess can be a potential contributor to ocular neuropathy in glaucoma. The current review focuses on the cellular and molecular aspects of endothelins and its receptors in the eye with an emphasis on its relationship to ocular function and its potential role in the etiology of glaucoma pathophysiology. 相似文献
995.
Strniskova M Barancik M Neckar J Ravingerova T 《Molecular and cellular biochemistry》2003,249(1-2):59-65
Diabetes mellitus (DM) causes myocardial remodeling on the subcellular level and alterations in the function of the cell membranes ion transport systems resulting in contractile dysfunction. The present study was aimed to investigate the expression and activation of mitogen-activated protein kinases (MAPKs) and their possible role in the acute diabetic rat hearts. Rats were injected with single dose of streptozotocin (45 mg/kg, i.v.), and after 1 week the disease was manifested by hyperglycemia and cardiac dysfunction. The Langendorff-perfused hearts were subjected to ischemia (5 or 30 min occlusion of LAD coronary artery). The protein pattern in cytosolic fraction of the heart tissue was determined after electrophoretic separation. The levels and activation of MAPKs were determined by Western blot analysis using specific antibodies. No differences between the diabetics and controls in the level of ERKs were found at baseline. However, in DM samples ERKs phosphorylation was markedly increased, and further changes occurred during ischemia. Also content of phoshorylated c-Raf kinase (an upstream activator of ERKs) was slightly increased at baseline conditions in the diabetic samples. In contrast, no significant changes in the contents and phosphorylation of p38-MAPK were observed at baseline. But some differences in the p38-MAPK phosphorylation were found during ischemia.The results show that differential pattern of protein kinase cascades activation in the diabetic hearts might be account for the modulation of their response to ischemia. 相似文献
996.
The signaling adapter proteins FRS2 and FRS3 are implicated in the transmission of extracellular signals from nerve growth factor (NGF) or fibroblast growth factor (FGF) receptors to the Ras/mitogen-activated protein kinase signaling cascade. This study presents the genomic sequence and exon-intron organization of the mouse FRS2 and FRS3 loci as well as their evolutionary conservation with their human counterparts. Both FRS2 and FRS3 contain 5 coding exons spanning over 7 kb of genomic sequence with similar exon sizes and organization. Comparative genomic sequence analyses show a highly conserved genomic organization between mouse and human in both FRS2 and FRS3 genes. Non-coding sequences, highly conserved between mouse and human, were identified in the FRS3 introns that may potentially function as regulatory elements. To assay potential differences in their patterns of expression, RT-PCR analysis was used to assay FRS2 and FRS3 expression in the developing embryo and neural tube (NT) during the time of neurogenesis. 相似文献
997.
Interleukin-1 (IL-1) has been implicated in neuroimmune responses and has pleiotropic actions in the brain. Compelling evidence
has shown that IL-1 is a major mediator of inflammation and the progression of cell death in response to brain injury and
cerebral ischemia. Its expression is strongly increased in these pathological conditions, and central administration of exogenous
IL-1 significantly exacerbates ischemic brain damage. In contrast, inhibiting IL-1 actions (by intracerebroventricular [icv]
injection of IL-1ra, neutralizing antibody to IL-1 or caspase-1 inhibitor) significantly reduces ischemic brain damage. IL-1
acts by binding to the IL-1 type-1 receptor (IL-1RI), which is to date, the only known functional receptor for IL-1. However,
our recent investigations suggest that IL-1 can act independently of IL-1RI, raising the possibility that additional, as yet
undiscovered, receptor(s) for IL-1 exist in the brain. The recent characterization of putative, new IL-1 ligands and new IL-1
receptor-related molecules leads to the hypothesis that there might be alternative IL-1 signaling pathway(s) in the central
nervous system (CNS). 相似文献
998.
Zine A 《Molecular neurobiology》2003,27(2):223-237
Mechanosensory hair cells of the vertebrate cochlea offer an excellent developmental system to study cell-fate specification,
and to gain insight into the many human neurological deficits which result in a hearing loss, by affecting primarily the hair
cells. Therefore, there is great interest in studying the molecular mechanisms that regulate their specification and differentiation.
Recent studies, based mostly on loss-of-function experiments that target the role of Notch signaling and basic helix-loop-helix
genes in inner-ear development have indicated that they can regulate mechanosensory hair cell-fate specification and their
initial differentiation. 相似文献
999.
1000.