全文获取类型
收费全文 | 2843篇 |
免费 | 395篇 |
专业分类
3238篇 |
出版年
2023年 | 23篇 |
2022年 | 36篇 |
2021年 | 79篇 |
2020年 | 41篇 |
2019年 | 54篇 |
2018年 | 62篇 |
2017年 | 53篇 |
2016年 | 102篇 |
2015年 | 175篇 |
2014年 | 183篇 |
2013年 | 173篇 |
2012年 | 265篇 |
2011年 | 211篇 |
2010年 | 137篇 |
2009年 | 123篇 |
2008年 | 168篇 |
2007年 | 210篇 |
2006年 | 252篇 |
2005年 | 167篇 |
2004年 | 118篇 |
2003年 | 113篇 |
2002年 | 123篇 |
2001年 | 21篇 |
2000年 | 17篇 |
1999年 | 24篇 |
1998年 | 29篇 |
1997年 | 16篇 |
1996年 | 23篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1970年 | 4篇 |
1969年 | 7篇 |
1962年 | 5篇 |
排序方式: 共有3238条查询结果,搜索用时 15 毫秒
1.
2.
3.
Johannes Schwerk Mario K?ster Hansj?rg Hauser Manfred Rohde Marcus Fulde Mathias W. Hornef Tobias May 《PloS one》2013,8(8)
Cell lines derived from the small intestine that reflect authentic properties of the originating intestinal epithelium are of high value for studies on mucosal immunology and host microbial homeostasis. A novel immortalization procedure was applied to generate continuously proliferating cell lines from murine E19 embryonic small intestinal tissue. The obtained cell lines form a tight and polarized epithelial cell layer, display characteristic tight junction, microvilli and surface protein expression and generate increasing transepithelial electrical resistance during in vitro culture. Significant up-regulation of Cxcl2 and Cxcl5 chemokine expression upon exposure to defined microbial innate immune stimuli and endogenous cytokines is observed. Cell lines were also generated from a transgenic interferon reporter (Mx2-Luciferase) mouse, allowing reporter technology-based quantification of the cellular response to type I and III interferon. Thus, the newly created cell lines mimic properties of the natural epithelium and can be used for diverse studies including testing of the absorption of drug candidates. The reproducibility of the method to create such cell lines from wild type and transgenic mice provides a new tool to study molecular and cellular processes of the epithelial barrier. 相似文献
4.
P. Higgins R. J. Mathias 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(4):439-444
Summary Calli were initiated from immature embryos of nine lines of hexaploid wheat (Triticum aestivum L. em. Thell). These were the euploid lines Chinese Spring and Cappelle-Desprez, a line of Chinese Spring ditelocentric for the long arm of 4B, four substitution lines of Chinese Spring in which chromosome 4B has been replaced by its homologues from different wheat varieties and substituted into Chinese Spring and a substitution line of Besostaya I 4B into Cappelle-Desprez. The calli from these lines were found to differ in their growth rates and morphogenic and regenerative activities. The substitution of different 4B chromosomes into Chinese Spring significantly increased morphogenesis and shoot regeneration from callus. The potential for developing wheat lines with improved culture characteristics is discussed. 相似文献
5.
6.
Mathias R. Fibi Michael Bröker Rainer Schulz Roloff Johannsen Gerd Zettlmeissl 《Applied microbiology and biotechnology》1991,35(5):622-630
Summary Experiments were carried out to assess the survival of recombinant plasmid DNA during large-scale production of recombinant human erythropoietin (rhuEPO) in a fermentation pilot plant. The analyses revealed DNA-degrading activities in the fermentation broth and in the waste-water, leading to rapid destruction of plasmid DNA added to medium or waste-water. The capability of the plasmid-DNA-spiked samples to transform competent bacteria was drastically reduced. The DNA-degrading activity in the waste-waters could be blocked by addition of EDTA or by boiling, indicating the presence of DNA-degrading enzymes (DNases). No plasmid-specific DNA sequences were detected in waste-water samples by in-vitro amplification with Taqpolymerase. Genomic DNA preparations of cell debris collected from waste-water samples only contained degraded plasmid DNA. Furthermore, it was shown that intact plasmid DNA could be degraded to fragments of less than 1000 bp by incubation at 121°C for 20 min, leading to a decrease in the plasmid-specific transforming capacity by a factor of 103 per minute. Thus, DNA from the rhuEPO production pilot plant was efficiently inactivated at three different levels: (i) in the fermentation medium (DNase), (ii) in the waste-water container (DNase), and (iii) by heat inactivation for 20 min at 120°C. These results indicate that the probability of delivery of recombinant DNA into the environment is extremely low in such biotechnological production processes.
Offprint requests to: M. R. Fibi 相似文献
7.
Steady-state current flow through gap junctions. Effects on intracellular ion concentrations and fluid movement. 总被引:1,自引:1,他引:0 下载免费PDF全文
Double voltage clamp studies were performed on gap junctions contained in septal membranes of the earthworm median giant axon. The gap junctions exhibited no conductance changes in response to voltages imposed across either the septal membrane or the plasma membrane. However, the trans-septal current displayed a slow (10 s) relaxation in response to transjunctional voltage steps. The experimental evidence suggests that this relaxation is a polarization of the septum due to local accumulation/depletion of permeant ions. A theoretical analysis of this observation suggests that the applied electric field causes accumulation of impermeant anions on one side of the junction and depletion on the other, which leads to a change in concentration of permeant ions to maintain macroscopic electroneutrality. The change in concentration of permeant ions generates a transjunctional equilibrium potential that opposes junctional current flow. These results indicate that currents flowing through gap junctions can have an influence on the distribution of intracellular ions. Moreover, the theoretical analysis suggests that such currents will be accompanied by significant intracellular and intercellular water flow. 相似文献
8.
The coupling of metabolic to secretory events in pancreatic islets. The possible role of glutathione reductase 总被引:1,自引:0,他引:1
W J Malaisse S P Dufrane P C Mathias A R Carpinelli F Malaisse-Lagae P Garcia-Morales I Valverde A Sener 《Biochimica et biophysica acta》1985,844(2):256-264
The participation of glutathione reductase in the process of nutrient-stimulated insulin release was investigated in rat pancreatic islets exposed to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU caused a time-and dose-related, irreversible inhibition of glutathione reductase activity. This coincided with a fall in both GSH/GSSG ratio and the thiol content of the islets. Pretreatment of the islets with BCNU inhibited the oxidation of glucose and its stimulant action upon both 45Ca net uptake and insulin release. Although BCNU (up to 0.5 mM) failed to affect the oxidation of L-leucine and L-glutamine, it also caused a dose-related inhibition of insulin release evoked by the combination of these two amino acids. The latter inhibition was apparently not fully accounted for by the modest to negligible effects of BCNU upon 45Ca uptake, 45Ca efflux, 86Rb efflux and cyclic AMP production. Since BCNU failed to inhibit insulin release evoked by the association of Ba2+ and theophylline, these results support the view that glutathione reductase participates in the coupling of metabolic to secretory events in the process of nutrient-stimulated insulin release. However, the precise modality of such a participation, for example the control of intracellular Ca2+ distribution, remains to be elucidated. 相似文献
9.
10.
R. J. Mathias K. Fukui C. N. Law 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(1):70-75
Summary Calli were initiated from immature embryos of eight lines of hexaploid wheat (Triticum aestivum L. em. Thell) with different cytoplasms, the euplasmic nuclear donor Chinese Spring and seven alloplasmic lines derived from wild relative species of the genera Triticum and Aegilops. The calli were found to differ in their initial growth rates, their sensitivity to 2,4-D and their ability to organise shoot primordia, demonstrating that the cytoplasm can significantly affect the behaviour of tissues in culture. The potential for improving the responses of tissues in culture by cytoplasmic changes is noted. 相似文献