全文获取类型
收费全文 | 6403篇 |
免费 | 598篇 |
国内免费 | 2篇 |
专业分类
7003篇 |
出版年
2024年 | 7篇 |
2023年 | 44篇 |
2022年 | 74篇 |
2021年 | 123篇 |
2020年 | 90篇 |
2019年 | 111篇 |
2018年 | 163篇 |
2017年 | 126篇 |
2016年 | 225篇 |
2015年 | 391篇 |
2014年 | 412篇 |
2013年 | 478篇 |
2012年 | 612篇 |
2011年 | 556篇 |
2010年 | 357篇 |
2009年 | 298篇 |
2008年 | 389篇 |
2007年 | 384篇 |
2006年 | 340篇 |
2005年 | 305篇 |
2004年 | 340篇 |
2003年 | 288篇 |
2002年 | 254篇 |
2001年 | 42篇 |
2000年 | 38篇 |
1999年 | 58篇 |
1998年 | 83篇 |
1997年 | 41篇 |
1996年 | 29篇 |
1995年 | 45篇 |
1994年 | 32篇 |
1993年 | 31篇 |
1992年 | 32篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1974年 | 9篇 |
排序方式: 共有7003条查询结果,搜索用时 0 毫秒
991.
992.
Christoph Kaleta Anna Göhler Stefan Schuster Knut Jahreis Reinhard Guthke Swetlana Nikolajewa 《BMC systems biology》2010,4(1):116
Background
Although Escherichia coli is one of the best studied model organisms, a comprehensive understanding of its gene regulation is not yet achieved. There exist many approaches to reconstruct regulatory interaction networks from gene expression experiments. Mutual information based approaches are most useful for large-scale network inference. 相似文献993.
Jasmin Hotzy Nicole Schneider Peter Kovermann Christoph Fahlke 《The Journal of biological chemistry》2013,288(51):36492-36501
Excitatory amino acid transporters (EAATs) are crucial for glutamate homeostasis in the mammalian central nervous system. They are not only secondary active glutamate transporters but also function as anion channels, and different EAATs vary considerably in glutamate transport rates and associated anion current amplitudes. A naturally occurring mutation, which was identified in a patient with episodic ataxia type 6 and that predicts the substitution of a highly conserved proline at position 290 by arginine (P290R), was recently shown to reduce glutamate uptake and to increase anion conduction by hEAAT1. We here used voltage clamp fluorometry to define how the homologous P259R mutation modifies the functional properties of hEAAT3. P259R inverts the voltage dependence, changes the sodium dependence, and alters the time dependence of hEAAT3 fluorescence signals. Kinetic analysis of fluorescence signals indicate that P259R decelerates a conformational change associated with sodium binding to the glutamate-free mutant transporters. This alteration in the glutamate uptake cycle accounts for the experimentally observed changes in glutamate transport and anion conduction by P259R hEAAT3. 相似文献
994.
Sophorolipid Production with High Yields on Whey Concentrate and Rapeseed Oil without Consumption of Lactose 总被引:1,自引:0,他引:1
Hans-J. Daniel Ralf T. Otto Matthias Reuss Christoph Syldatk 《Biotechnology letters》1998,20(8):805-807
Sophorolipids were produced by single-step batch cultivation of Candida bombicola ATCC 22214 on deproteinized whey concentrate and repeated feed of rapeseed oil. A mild sterilization method for whey was developed. High yields of 280 g dry sophorolipids l–1 were obtained from deproteinized whey concentrate containing 100 g lactose l–1 and 300 g rapeseed oil l–1. Surprisingly, the whey lactose was not consumed by the organism. Growth only on the oil was assumed and a high lipase activity of 24 U per g cell dry weight resulted. 相似文献
995.
996.
Ann-Catrin Fender Jasmin Mantilla-Contreras Christoph Leuschner 《Trees - Structure and Function》2011,25(5):847-857
Climatic change exposes temperate trees to the simultaneous alteration of various growth-relevant factors, among them increased
temperatures, extended growing season length and rising atmospheric [CO2], often in combination with more severe droughts and reduced air humidities in summer, and elevated atmospheric N deposition.
We conducted a multi-factorial climate chamber experiment to search for interactive effects of temperature (T), soil moisture (θ), water vapour saturation deficit (VPD) and N availability (N) on the growth of Fagus sylvatica saplings and for identifying the most relevant factors that control leaf area development and productivity under a future
warmer and drier climate with continuing high N deposition. For each of the four factors, two levels were simulated, reflecting
current and expected future conditions in Central European beech forests. All four factors (including VPD) had a significant
effect on productivity; several factors (e.g. T × VPD) interacted in a synergistic way. Productivity was most tightly correlated
with the number of leaves while leaf area was less influential and photosynthetic activity was of only minor importance. The
number of leaves produced was most tightly correlated with θ, N and VPD, while leaf area (leaf expansion) showed closest relation to temperature. We conclude that predictions about the
growth response of trees to climate change and altered atmospheric N deposition need to consider a multitude of environmental
factors and must account for positive and negative factor interactions. 相似文献
997.
Mice lacking the 4th-group paralog Hoxd4 display malformations of the anterior vertebral column, but are viable and fertile. Here, we report that zebrafish embryos having decreased function of the orthologous hoxd4a gene manifest striking perturbations in vasculogenesis, angiogenesis and primitive and definitive hematopoiesis. These defects are preceded by reduced expression of the hemangioblast markers scl1, lmo2 and fli1 within the posterior lateral plate mesoderm (PLM) at 13 hours post fertilization (hpf). Epistasis analysis revealed that hoxd4a acts upstream of meis1.1 but downstream of cdx4 as early as the shield stage in ventral-most mesoderm fated to give rise to hemangioblasts, leading us to propose that loss of hoxd4a function disrupts hemangioblast specification. These findings place hoxd4a high in a genetic hierarchy directing hemangioblast formation downstream of cdx1/cdx4 and upstream of meis1.1. An additional consequence of impaired hoxd4a and meis1.1 expression is the deregulation of multiple Hox genes implicated in vasculogenesis and hematopoiesis which may further contribute to the defects described here. Our results add to evidence implicating key roles for Hox genes in their initial phase of expression early in gastrulation. 相似文献
998.
Natascha Verhagen Andy Wiranata Wijaya Attila Teleki Muhammad Fadhlullah Andreas Unsld Martin Schilling Christoph Heinrich Ralf Takors 《Engineering in Life Science》2020,20(9-10):384-394
Increasing markets for biopharmaceuticals, including monoclonal antibodies, have triggered a permanent need for bioprocess optimization. Biochemical engineering approaches often include the optimization of basal and feed media to improve productivities of Chinese hamster ovary (CHO) cell cultures. Often, l ‐tyrosine is added as dipeptide to deal with its poor solubility at neutral pH. Showcasing IgG1 production with CHO cells, we investigated the supplementation of three l ‐tyrosine (TYR, Y) containing dipeptides: glycyl‐l ‐tyrosine (GY), l ‐tyrosyl‐l ‐valine (YV), and l ‐prolyl‐l ‐tyrosine (PY). While GY and YV led to almost no phenotypic and metabolic differences compared to reference samples, PY significantly amplified TYR uptake thus maximizing related catabolic activity. Consequently, ATP formation was roughly four times higher upon PY application than in reference samples. 相似文献
999.
Christoph Keuschnig Markus Gorfer Guofen Li Daniel Mania Åsa Frostegård Lars Bakken Catherine Larose 《Environmental microbiology》2020,22(6):2182-2195
Fungal denitrification is claimed to produce non-negligible amounts of N2O in soils, but few tested species have shown significant activity. We hypothesized that denitrifying fungi would be found among those with assimilatory nitrate reductase, and tested 20 such batch cultures for their respiratory metabolism, including two positive controls, Fusarium oxysporum and Fusarium lichenicola, throughout the transition from oxic to anoxic conditions in media supplemented with . Enzymatic reduction of (NIR) and NO (NOR) was assessed by correcting measured NO- and N2O-kinetics for abiotic NO- and N2O-production (sterile controls). Significant anaerobic respiration was only confirmed for the positive controls and for two of three Fusarium solani cultures. The NO kinetics in six cultures showed NIR but not NOR activity, observed through the accumulation of NO. Others had NOR but not NIR activity, thus reducing abiotically produced NO to N2O. The presence of candidate genes (nirK and p450nor) was confirmed in the positive controls, but not in some of the NO or N2O accumulating cultures. Based on our results, we conclude that only the Fusarium cultures were able to sustain anaerobic respiration and produced low amounts of N2O as a response to an abiotic NO production from the medium. 相似文献
1000.
Kole T. Roybal Emily M. Mace Danielle J. Clark Alan D. Leard Andrew Herman Paul Verkade Jordan S. Orange Christoph Wülfing 《PloS one》2015,10(8)
Dynamic subcellular distributions of signaling system components are critical regulators of cellular signal transduction through their control of molecular interactions. Understanding how signaling activity depends on such distributions and the cellular structures driving them is required for comprehensive insight into signal transduction. In the activation of primary murine T cells by antigen presenting cells (APC) signaling intermediates associate with various subcellular structures, prominently a transient, wide, and actin-associated lamellum extending from an interdigitated T cell:APC interface several micrometers into the T cell. While actin dynamics are well established as general regulators of cellular organization, their role in controlling signaling organization in primary T cell:APC couples and the specific cellular structures driving it is unresolved. Using modest interference with actin dynamics with a low concentration of Jasplakinolide as corroborated by costimulation blockade we show that T cell actin preferentially controls lamellal signaling localization and activity leading downstream to calcium signaling. Lamellal localization repeatedly related to efficient T cell function. This suggests that the transient lamellal actin matrix regulates T cell signaling associations that facilitate T cell activation. 相似文献