全文获取类型
收费全文 | 1429篇 |
免费 | 90篇 |
国内免费 | 2篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 38篇 |
2015年 | 49篇 |
2014年 | 62篇 |
2013年 | 83篇 |
2012年 | 115篇 |
2011年 | 109篇 |
2010年 | 69篇 |
2009年 | 52篇 |
2008年 | 87篇 |
2007年 | 81篇 |
2006年 | 91篇 |
2005年 | 87篇 |
2004年 | 98篇 |
2003年 | 73篇 |
2002年 | 56篇 |
2001年 | 7篇 |
1999年 | 15篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1971年 | 5篇 |
1962年 | 5篇 |
1935年 | 4篇 |
1912年 | 4篇 |
排序方式: 共有1521条查询结果,搜索用时 15 毫秒
41.
Heng Liang Tan Bao Zhu Tan Winfred Xi Tai Goh Simeon Cua Andre Choo 《Biotechnology and bioengineering》2019,116(11):2996-3005
This study describes the use of a previously reported chimerised monoclonal antibody (mAb), ch2448, to kill human embryonic stem cells (hESCs) in vivo and prevent or delay the formation of teratomas. ch2448 was raised against hESCs and was previously shown to effectively kill ovarian and breast cancer cells in vitro and in vivo. The antigen target was subsequently found to be Annexin A2, an oncofetal antigen expressed on both embryonic cells and cancer cells. Against cancer cells, ch2448 binds and kills via antibody-dependent cell-mediated cytotoxicity (ADCC) and/or antibody-drug conjugate (ADC) routes. Here, we investigate if the use of ch2448 can be extended to hESC. ch2448 was found to bind specifically to undifferentiated hESC but not differentiated progenitors. Similar to previous study using cancer cells, ch2448 kills hESC in vivo either indirectly by eliciting ADCC or directly as an ADC. The treatment with ch2448 post-transplantation eliminated the in vivo circulating undifferentiated cells and prevented or delayed the formation of teratomas. This surveillance role of ch2448 adds an additional layer of safeguard to enhance the safety and efficacious use of pluripotent stem cell-derived products in regenerative medicine. Thereby, translating the use of ch2448 in the treatment of cancers to a proof of concept study in hESC (or pluripotent stem cell [PSC]), we show that mAbs can also be used to eliminate teratoma forming cells in vivo during PSC-derived cell therapies. We propose to use this strategy to complement existing methods to eliminate teratoma-forming cells in vitro. Residual undifferentiated cells may escape in vitro removal methods and be introduced into patients together with the differentiated cells. 相似文献
42.
Fluid-phase and receptor-mediated endocytosis were studied in Freund's adjuvant elicited macrophages. These cells were found to bind and internalize significantly larger amounts of peroxidase-antiperoxidase (PAP) immune complex than resident macrophages. Similarly the rate of the fluid-phase uptake was higher in elicited cells. When studying the early steps of endocytotic processes, omega-shaped plasma membrane pits (d~90 nm) were found at the macrophage cell surface. Although occurring occasionally in resident cells, their number was highly increased after elicitation in 30% of the macrophage cell population. The different morphology of these cells coincided with a lower endocytotic activity and a very strong ecto Ca2+-ATPase reaction. The present findings indicate that the elicited macrophage population is heterogenous and consists of different subclasses. 相似文献
43.
Werner Baumgartner Friederike Saxe Agnes Weth David Hajas Darwin Sigumonrong Jens Emmerlich Martin Singheiser Wolfgang Bhme Jochen M. Schneider 《仿生工程学报(英文版)》2007,4(1)
The sandfish is a lizard having the remarkable ability to move in desert sand in a swimming-like fashion. The most out-standing adaptations to this mode of life are the low friction behaviour and the extensive abrasion resistance of the sandfish skin against sand, outperforming even steel. We investigated the topography, the composition and the mechanical properties of sandfish scales. These consist of glycosylated keratins with high amount of sulphur but no hard inorganic material, such as silicates or lime. Remarkably, atomic force microscopy shows an almost complete absence of attractive forces between the scale surface and a silicon tip, suggesting that this is responsible for the unusual tribological properties. The unusual glycosylation of the keratins was found to be absolutely necessary for the described phenomenon. The scales were dissolved and reconstituted on a polymer surface resulting in properties similar to the original scale. Thus, we provide a pathway towards exploitation of the reconstituted scale material for future engineering applications. 相似文献
44.
Cua DJ Hutchins B LaFace DM Stohlman SA Coffman RL 《Journal of immunology (Baltimore, Md. : 1950)》2001,166(1):602-608
Multiple sclerosis, an inflammatory, demyelinating disease of the CNS currently lacks an effective therapy. We show here that CNS inflammation and clinical disease in experimental autoimmune encephalomyelitis, an experimental model of multiple sclerosis, could be prevented completely by a replication-defective adenovirus vector expressing the anti-inflammatory cytokine IL-10 (replication-deficient adenovirus expressing human IL-10), but only upon inoculation into the CNS where local infection and high IL-10 levels were achieved. High circulating levels of IL-10 produced by i. v. infection with replication-deficient adenovirus expressing human IL-10 was ineffective, although the immunological pathways for disease are initiated in the periphery in this disease model. In addition to this protective activity, intracranial injection of replication-deficient adenovirus expressing human IL-10 to mice with active disease blocked progression and accelerated disease remission. In a relapsing-remitting disease model, IL-10 gene transfer during remission prevented subsequent relapses. These data help explain the varying outcomes previously reported for systemic delivery of IL-10 in experimental autoimmune encephalomyelitis and show that, for optimum therapeutic activity, IL-10 must either access the CNS from the peripheral circulation or be delivered directly to it by strategies including the gene transfer described here. 相似文献
45.
Activation of regulatory cells suppresses experimental allergic encephalomyelitis via secretion of IL-10 总被引:6,自引:0,他引:6
Stohlman SA Pei L Cua DJ Li Z Hinton DR 《Journal of immunology (Baltimore, Md. : 1950)》1999,163(11):6338-6344
Suppression of CD4+ Th1 cell-mediated autoimmune disease via immune deviation is an attractive potential therapeutic approach. CD4+ Th2 T cells specific for myelin basic protein, induced by immunization of young adult male SJL mice, suppress or modify the progression of CNS autoimmune disease. This report demonstrates that activation of non-neuroantigen-specific Th2 cells is sufficient to suppress both clinical and histological experimental allergic encephalomyelitis (EAE). Th2 cells were obtained following immunization of male SJL mice with keyhole limpet hemocyanin. Transfer of these cells did not modify EAE, a model of human multiple sclerosis, in the absence of cognate Ag. Disease suppression was obtained following adoptive transfer and subcutaneous immunization. Suppression was not due to the deletion of myelin basic protein-specific T cells, but resulted from the presence of IL-10 as demonstrated by the inhibition of Th2-mediated EAE suppression via passive transfer with either anti-IL-10 or anti-IL-10R mAb. These data demonstrate that peripheral activation of a CD4+ Th2 population specific for an Ag not expressed in the CNS modifies CNS autoimmune disease via IL-10. These data suggest that either peripheral activation or direct administration of IL-10 may be of benefit in treating Th1-mediated autoimmune diseases. 相似文献
46.
Agnes Van den Pol-van Dasselaar Marinus L. van Beusichem Oene Oenema 《Biogeochemistry》1999,44(2):205-220
The area of wet grasslands on peat soil in the Netherlands is slowly increasing at the expense of drained, agriculturally used grasslands. This study aimed (i) to assess the contribution of wet grasslands on peat soil to methane (CH4) emissions, and (ii) to explain differences among sites and between years in order to improve our understanding of controlling factors. For these purposes, a field study was conducted in the period 1994–1996 in the nature preserve Nieuwkoopse Plassen, which is a former peat mining and agricultural area. Net CH4 emissions were measured weekly to monthly with vented closed flux chambers at three representative sites, and at ditches near these sites. Three-years average of CH4 emissions was 7.9 g CH4 m–2 yr–1 for Drie Berken Zudde, 13.3 for Koole, and 20.4 for Brampjesgat. Ditches near the sites emitted 4.2–22.5 g CH4 m–2 yr–1. The time-course of CH4 emissions for all experimental sites and years was fit with a multiple linear regression model with ground water level and soil temperature as independent variables. Lowering or raising the ground water level by 5 cm could decrease or increase CH4 emissions by 30–50%. Therefore, ground water level management of these grasslands should be done with care. 相似文献
47.
48.
Polymorphic membrane protein (Pmp)21 otherwise known as PmpD is the longest of 21 Pmps expressed by Chlamydophila pneumoniae. Recent bioinformatical analyses annotated PmpD as belonging to a family of exported Gram-negative bacterial proteins designated autotransporters. This prediction, however, was never experimentally supported, nor was the function of PmpD known. Here, using 1D and 2D PAGE we demonstrate that PmpD is processed into two parts, N-terminal (N-pmpD), middle (M-pmpD) and presumably third, C-terminal part (C-pmpD). Based on localization of the external part on the outer membrane as shown by immunofluorescence, immuno-electron microscopy and immunoblotting combined with trypsinization, we demonstrate that N-pmpD translocates to the surface of bacteria where it non-covalently binds other components of the outer membrane. We propose that N-pmpD functions as an adhesin, as antibodies raised against N-pmpD blocked chlamydial infectivity in the epithelial cells. In addition, recombinant N-pmpD activated human monocytes in vitro by upregulating their metabolic activity and by stimulating IL-8 release in a dose-dependent manner. These results demonstrate that N-PmpD is an autotransporter component of chlamydial outer membrane, important for bacterial invasion and host inflammation. 相似文献
49.
Essential role of Mia40 in import and assembly of mitochondrial intermembrane space proteins 总被引:11,自引:0,他引:11
Chacinska A Pfannschmidt S Wiedemann N Kozjak V Sanjuán Szklarz LK Schulze-Specking A Truscott KN Guiard B Meisinger C Pfanner N 《The EMBO journal》2004,23(19):3735-3746
Mitochondria import nuclear-encoded precursor proteins to four different subcompartments. Specific import machineries have been identified that direct the precursor proteins to the mitochondrial outer membrane, inner membrane or matrix, respectively. However, a machinery dedicated to the import of mitochondrial intermembrane space (IMS) proteins has not been found so far. We have identified the essential IMS protein Mia40 (encoded by the Saccharomyces cerevisiae open reading frame YKL195w). Mitochondria with a mutant form of Mia40 are selectively inhibited in the import of several small IMS proteins, including the essential proteins Tim9 and Tim10. The import of proteins to the other mitochondrial subcompartments does not depend on functional Mia40. The binding of small Tim proteins to Mia40 is crucial for their transport across the outer membrane and represents an initial step in their assembly into IMS complexes. We conclude that Mia40 is a central component of the protein import and assembly machinery of the mitochondrial IMS. 相似文献
50.
Current methods for aligning biological sequences are based on dynamic programming algorithms. If large numbers of sequences or a number of long sequences are to be aligned, the required computations are expensive in memory and central processing unit (CPU) time. In an attempt to bring the tools of large-scale linear programming (LP) methods to bear on this problem, we formulate the alignment process as a controlled Markov chain and construct a suggested alignment based on policies that minimise the expected total cost of the alignment. We discuss the LP associated with the total expected discounted cost and show the results of a solution of the problem based on a primal-dual interior point method. Model parameters, estimated from aligned sequences, along with cost function parameters are used to construct the objective and constraint conditions of the LP problem. This article concludes with a discussion of some alignments obtained from the LP solutions of problems with various cost function parameter values. 相似文献