全文获取类型
收费全文 | 2689篇 |
免费 | 209篇 |
国内免费 | 1篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 45篇 |
2020年 | 21篇 |
2019年 | 22篇 |
2018年 | 45篇 |
2017年 | 31篇 |
2016年 | 81篇 |
2015年 | 139篇 |
2014年 | 145篇 |
2013年 | 192篇 |
2012年 | 236篇 |
2011年 | 233篇 |
2010年 | 160篇 |
2009年 | 145篇 |
2008年 | 166篇 |
2007年 | 175篇 |
2006年 | 137篇 |
2005年 | 143篇 |
2004年 | 133篇 |
2003年 | 110篇 |
2002年 | 106篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 36篇 |
1997年 | 32篇 |
1996年 | 19篇 |
1995年 | 25篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 26篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1971年 | 5篇 |
排序方式: 共有2899条查询结果,搜索用时 359 毫秒
61.
João R. C. Ramos Alexander G. Rath Yvonne Genzel Volker Sandig Udo Reichl 《Biotechnology and bioengineering》2020,117(5):1533-1553
Mathematical modeling of animal cell growth and metabolism is essential for the understanding and improvement of the production of biopharmaceuticals. Models can explain the dynamic behavior of cell growth and product formation, support the identification of the most relevant parameters for process design, and significantly reduce the number of experiments to be performed for process optimization. Few dynamic models have been established that describe both extracellular and intracellular dynamics of growth and metabolism of animal cells. In this study, a model was developed, which comprises a set of 33 ordinary differential equations to describe batch cultivations of suspension AGE1.HN.AAT cells considered for the production of α1-antitrypsin. This model combines a segregated cell growth model with a structured model of intracellular metabolism. Overall, it considers the viable cell concentration, mean cell diameter, viable cell volume, concentration of extracellular substrates, and intracellular concentrations of key metabolites from the central carbon metabolism. Furthermore, the release of metabolic by-products such as lactate and ammonium was estimated directly from the intracellular reactions. Based on the same set of parameters, this model simulates well the dynamics of four independent batch cultivations. Analysis of the simulated intracellular rates revealed at least two distinct cellular physiological states. The first physiological state was characterized by a high glycolytic rate and high lactate production. Whereas the second state was characterized by efficient adenosine triphosphate production, a low glycolytic rate, and reactions of the TCA cycle running in the reverse direction from α-ketoglutarate to citrate. Finally, we show possible applications of the model for cell line engineering and media optimization with two case studies. 相似文献
62.
Shauna M. Collins Courtney E. Bakan Gina D. Swartzel Craig C. Hofmeister Yvonne A. Efebera Hakju Kwon Gary C. Starling David Ciarlariello Shakthi Bhaskar Edward L. Briercheck Tiffany Hughes Jianhua Yu Audie Rice Don M. Benson Jr. 《Cancer immunology, immunotherapy : CII》2013,62(12):1841-1849
Elotuzumab is a monoclonal antibody in development for multiple myeloma (MM) that targets CS1, a cell surface glycoprotein expressed on MM cells. In preclinical models, elotuzumab exerts anti-MM efficacy via natural killer (NK)-cell-mediated antibody-dependent cellular cytotoxicity (ADCC). CS1 is also expressed at lower levels on NK cells where it acts as an activating receptor. We hypothesized that elotuzumab may have additional mechanisms of action via ligation of CS1 on NK cells that complement ADCC activity. Herein, we show that elotuzumab appears to induce activation of NK cells by binding to NK cell CS1 which promotes cytotoxicity against CS1(+) MM cells but not against autologous CS1(+) NK cells. Elotuzumab may also promote CS1–CS1 interactions between NK cells and CS1(+) target cells to enhance cytotoxicity in a manner independent of ADCC. NK cell activation appears dependent on differential expression of the signaling intermediary EAT-2 which is present in NK cells but absent in primary, human MM cells. Taken together, these data suggest elotuzumab may enhance NK cell function directly and confer anti-MM efficacy by means beyond ADCC alone. 相似文献
63.
Arsenate is known to be accumulated by cultured astrocytes and to stimulate astrocytic glutathione export, but the arsenate uptake into astrocytes has not been characterized so far. To address this topic, we have exposed primary rat astrocyte cultures to arsenate and determined the cellular arsenic content by atomic absorption spectroscopy. Viable astrocytes accumulated arsenate in a time- and concentration-dependent manner. Their cellular arsenic content increased almost proportional with time for up to 60 min after application of arsenate. Analysis of the concentration-dependent increase in the specific arsenic content of the cells after 30 min of arsenate exposure revealed that cultured astrocytes take up arsenate with saturable kinetics by a transport process that has apparent KM- and Vmax-values of 1.7 ± 0.2 mM and 28 ± 4 nmol/(mg protein × 30 min), respectively. Arsenate uptake in viable astrocytes was strongly inhibited by the presence of phosphate or by lowering the incubation temperature to 4 °C and was completely abolished in a sodium ion-free medium. These results strongly suggest that the saturable temperature-dependent arsenate uptake into astrocytes is mediated by a sodium-dependent phosphate cotransporter. 相似文献
64.
65.
Eric Allan Wolfgang W. Weisser Markus Fischer Ernst-Detlef Schulze Alexandra Weigelt Christiane Roscher Jussi Baade Romain L. Barnard Holger Beßler Nina Buchmann Anne Ebeling Nico Eisenhauer Christof Engels Alexander J. F. Fergus Gerd Gleixner Marlén Gubsch Stefan Halle Alexandra M. Klein Ilona Kertscher Annely Kuu Markus Lange Xavier Le Roux Sebastian T. Meyer Varvara D. Migunova Alexandru Milcu Pascal A. Niklaus Yvonne Oelmann Esther Pašalić Jana S. Petermann Franck Poly Tanja Rottstock Alexander C. W. Sabais Christoph Scherber Michael Scherer-Lorenzen Stefan Scheu Sibylle Steinbeiss Guido Schwichtenberg Vicky Temperton Teja Tscharntke Winfried Voigt Wolfgang Wilcke Christian Wirth Bernhard Schmid 《Oecologia》2013,173(1):223-237
In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination. 相似文献
66.
David E. Saslowsky Yvonne M. te Welscher Daniel J.-F. Chinnapen Jessica S. Wagner Joy Wan Eli Kern Wayne I. Lencer 《The Journal of biological chemistry》2013,288(36):25804-25809
Cholera toxin causes diarrheal disease by binding ganglioside GM1 on the apical membrane of polarized intestinal epithelial cells and trafficking retrograde through sorting endosomes, the trans-Golgi network (TGN), and into the endoplasmic reticulum. A fraction of toxin also moves from endosomes across the cell to the basolateral plasma membrane by transcytosis, thus breeching the intestinal barrier. Here we find that sorting of cholera toxin into this transcytotic pathway bypasses retrograde transport to the TGN. We also find that GM1 sphingolipids can traffic from apical to basolateral membranes by transcytosis in the absence of toxin binding but only if the GM1 species contain cis-unsaturated or short acyl chains in the ceramide domain. We found previously that the same GM1 species are needed to efficiently traffic retrograde into the TGN and endoplasmic reticulum and into the recycling endosome, implicating a shared mechanism of action for sorting by lipid shape among these pathways. 相似文献
67.
Andreas M. Roeder Yvonne Roettger Anne Stündel Richard Dodel Armin Geyer 《The Journal of biological chemistry》2013,288(38):27638-27645
Covalently linked carboxyl-terminal segments of the β-amyloid peptide (Aβ) were tested for their qualification as minimal conformational epitopes of the naturally occurring human autoantibodies against β-amyloid (nAbs-Aβ). nAbs-Aβ specifically recognize the toxic oligomers of Aβ and not the monomeric or the fibrillar forms of Aβ. The synthetic dimers of Aβ(28–40) described herein mimic the toxic Aβ oligomers but are not kinetic intermediates with uncertain compositions. CD spectra identified a surprisingly rich conformational behavior of selected miniamyloids. We observed a highly cooperative conformational transition of β-sheet to α-helix upon the addition of the helix enforcing co-solvent hexafluoroisopropanol. The CD curves of dimer 9 resembled, in a completely reversible manner, the CD spectra measured during the irreversible fibrillation of the parent Aβ(1–40). Synthetic peptide epitopes with high affinities for nAbs-Aβ are needed to identify the physiological roles of nAbs-Aβ and are promising epitopes for vaccination experiments. 相似文献
68.
Tsutomu Akama Charlotte Virtucio Chen Dong Richard Kimura Yong-Kang Zhang James A. Nieman Rashmi Sharma Xiaosong Lu Marcelo Sales Rajeshwar Singh Anne Wu Xiao-Qing Fan Liang Liu Jacob J. Plattner Kurt Jarnagin Yvonne R. Freund 《Bioorganic & medicinal chemistry letters》2013,23(6):1680-1683
A series of novel 6-(aminomethylphenoxy)benzoxaborole analogs was synthesized for the investigation of the structure–activity relationship of the inhibition of TNF-alpha, IL-1beta, and IL-6, from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compounds 9d and 9e showed potent activity against all three cytokines with IC50 values between 33 and 83 nM. Chloro substituted analog 9e (AN3485) is considered to be a promising lead for novel anti-inflammatory agent with a favorable pharmacokinetic profile. 相似文献
69.
Tsutomu Akama Chen Dong Charlotte Virtucio Yvonne R. Freund Daitao Chen Matthew D. Orr Robert T. Jacobs Yong-Kang Zhang Vincent Hernandez Yang Liu Anne Wu Wei Bu Liang Liu Kurt Jarnagin Jacob J. Plattner 《Bioorganic & medicinal chemistry letters》2013,23(21):5870-5873
Structure–activity relationships of 6-(benzoylamino)benzoxaborole analogs were investigated for the inhibition of TNF-α, IL-1β, and IL-6 from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compound 1q showed potent activity against all three cytokines with IC50 values between 0.19 and 0.50 μM, inhibited LPS-induced TNF-α and IL-6 elevation in mice and improved collagen-induced arthritis in mice. Compound 1q (AN4161) is considered to be a promising lead for novel anti-inflammatory agent with an excellent pharmacokinetic profile. 相似文献
70.
The molecular integrity of the active site of phytases from fungi is critical for maintaining phytase function as efficient catalytic
machines. In this study, the molecular dynamics (MD) of two monomers of phytase B from Aspergillus niger, the disulfide intact
monomer (NAP) and a monomer with broken disulfide bonds (RAP), were simulated to explore the conformational basis of the
loss of catalytic activity when disulfide bonds are broken. The simulations indicated that the overall secondary and tertiary
structures of the two monomers were nearly identical but differed in some crucial secondary–structural elements in the vicinity of
the disulfide bonds and catalytic site. Disulfide bonds stabilize the β-sheet that contains residue Arg66 of the active site and
destabilize the α-helix that contains the catalytic residue Asp319. This stabilization and destabilization lead to changes in the shape
of the active–site pocket. Functionally important hydrogen bonds and atomic fluctuations in the catalytic pocket change during the
RAP simulation. None of the disulfide bonds are in or near the catalytic pocket but are most likely essential for maintaining the
native conformation of the catalytic site.