全文获取类型
收费全文 | 5801篇 |
免费 | 444篇 |
国内免费 | 2篇 |
专业分类
6247篇 |
出版年
2023年 | 17篇 |
2022年 | 38篇 |
2021年 | 68篇 |
2020年 | 50篇 |
2019年 | 51篇 |
2018年 | 79篇 |
2017年 | 70篇 |
2016年 | 117篇 |
2015年 | 185篇 |
2014年 | 260篇 |
2013年 | 341篇 |
2012年 | 348篇 |
2011年 | 384篇 |
2010年 | 261篇 |
2009年 | 252篇 |
2008年 | 342篇 |
2007年 | 366篇 |
2006年 | 341篇 |
2005年 | 346篇 |
2004年 | 305篇 |
2003年 | 287篇 |
2002年 | 304篇 |
2001年 | 68篇 |
2000年 | 57篇 |
1999年 | 81篇 |
1998年 | 109篇 |
1997年 | 86篇 |
1996年 | 74篇 |
1995年 | 58篇 |
1994年 | 63篇 |
1993年 | 66篇 |
1992年 | 49篇 |
1991年 | 56篇 |
1990年 | 40篇 |
1989年 | 58篇 |
1988年 | 45篇 |
1987年 | 31篇 |
1986年 | 42篇 |
1985年 | 34篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 52篇 |
1981年 | 33篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 23篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1974年 | 15篇 |
排序方式: 共有6247条查询结果,搜索用时 15 毫秒
61.
Itten René Hischier Roland Andrae Anders S. G. Bieser Jan C. T. Cabernard Livia Falke Annemarie Ferreboeuf Hugues Hilty Lorenz M. Keller Regula L. Lees-Perasso Etienne Preist Chris Stucki Matthias 《The International Journal of Life Cycle Assessment》2020,25(10):2093-2098
The International Journal of Life Cycle Assessment - 相似文献
62.
Daniel Kleine Jonas Chodorski Sayani Mitra Christin Schlegel Katharina Huttenlochner Christine Müller‐Renno Joydeep Mukherjee Christiane Ziegler Roland Ulber 《Engineering in Life Science》2019,19(7):513-521
Imaging of biofilms on opaque surfaces is a challenge presented to researchers especially considering pathogenic bacteria, as those typically grow on living tissue, such as mucosa and bone. However, they can also grow on surfaces used in industrial applications such as food production, acting as a hindrance to the process. Thus, it is important to understand bacteria better in the environment they actually have relevance in. Stainless steel and titanium substrata were line structured and dotted surface topographies for titanium substrata were prepared to analyze their effects on biofilm formation of a constitutively green fluorescent protein (GFP)‐expressing Escherichia coli strain. The strain was batch cultivated in a custom built flow cell initially for 18 h, followed by continuous cultivation for 6 h. Confocal laser scanning microscopy (CLSM) was used to determine the biofilm topography. Biofilm growth of E. coli GFPmut2 was not affected by the type of metal substrate used; rather, attachment and growth were influenced by variable shapes of the microstructured titanium surfaces. In this work, biofilm cultivation in flow cells was coupled with the most widely used biofilm analytical technique (CLSM) to study the time course of growth of a GFP‐expressing biofilm on metallic surfaces without intermittent sampling or disturbing the natural development of the biofilm. 相似文献
63.
64.
Roland Maly 《Molecular & general genetics : MGG》1958,89(5):692-696
Summary Experiments to raise the frequency of plastid-mutations inAntirrhinum majus have been ineffective when proplastids were X-rayed in egg-cells or were treated in meristems of growing plants by infiltration of three different chemicals.
Mit Unterstützung der Deutschen Forschungsgemeinschaft. 相似文献
Mit Unterstützung der Deutschen Forschungsgemeinschaft. 相似文献
65.
The liver is responsible for key metabolic functions, including control of normal homoeostasis in response to diet and xenobiotic metabolism/detoxification. We have shown previously that inactivation of the hepatic cytochrome P450 system through conditional deletion of POR (P450 oxidoreductase) induces hepatic steatosis, liver growth and P450 expression. We have exploited a new conditional model of POR deletion to investigate the mechanism underlying these changes. We demonstrate that P450 induction, liver growth and hepatic triacylglycerol (triglyceride) homoeostasis are intimately linked and provide evidence that the observed phenotypes result from hepatic accumulation of unsaturated fatty acids, which mediate these phenotypes by activation of the nuclear receptor CAR (constitutive androstane receptor) and, to a lesser degree, PXR (pregnane X receptor). To our knowledge this is the first direct evidence that P450s play a major role in controlling unsaturated fatty acid homoeostasis via CAR. The regulation of P450s involved in xenobiotic metabolism by this mechanism has potentially significant implications for individual responses to drugs and environmental chemicals. 相似文献
66.
Wenying Shou Ramzi Azzam Susan L Chen Michael J Huddleston Christopher Baskerville Harry Charbonneau Roland S Annan Steve A Carr Raymond J Deshaies 《BMC molecular biology》2002,3(1):3-14
Background
In S. cerevisiae, the mitotic exit network (MEN) proteins, including the Polo-like protein kinase Cdc5 and the protein phosphatase Cdc14, are required for exit from mitosis. In pre-anaphase cells, Cdc14 is sequestered to the nucleolus by Net1 as a part of the RENT complex. When cells are primed to exit mitosis, the RENT complex is disassembled and Cdc14 is released from the nucleolus. 相似文献67.
Whole‐cell biotransformation of oleanolic acid by free and immobilized cells of Nocardia iowensis: Characterization of new metabolites 下载免费PDF全文
Benjamin Ludwig Doris Geib Christiane Haas Juliane Steingroewer Thomas Bley Kai Muffler Roland Ulber 《Engineering in Life Science》2015,15(1):108-115
In this study, Nocardia iowensis was used to transform oleanolic acid (OA) into oleanane derivatives. The first derivative, which was found after 24 h of cultivation, was the known and already described OA methyl ester. After 1 week, two other derivatives (oleanonic acid methyl ester and an unknown metabolite) were identified as new products of a biotransformation by N. iowensis. These oleanane metabolites were characterized by HPLC, HPLC‐ESI‐MS, and HPLC‐1H NMR spectroscopy. The biotransformation was performed by suspended and immobilized cells (ICs) of N. iowensis. Cells immobilized in alginate beads were used in order to prepare a continuous process. The substrate uptake of free and ICs was similar, whereas the peak area of OA methyl ester of the ICs was only about 10% of the native cells. However, the final product (oleanonic acid methyl ester) concentrations were similar in both approaches, whereas the unknown metabolite 3 was only detected transiently in the medium of ICs. Based on these results, a new biosynthetic pathway for the biotechnological production of oleanonic acid methyl ester is proposed. 相似文献
68.
Eichinger Jonas F. Grill Maximilian J. Kermani Iman Davoodi Aydin Roland C. Wall Wolfgang A. Humphrey Jay D. Cyron Christian J. 《Biomechanics and modeling in mechanobiology》2021,20(5):1851-1870
Biomechanics and Modeling in Mechanobiology - Living soft tissues appear to promote the development and maintenance of a preferred mechanical state within a defined tolerance around a so-called set... 相似文献
69.
Sarah Matheisl Otto Berninghausen Thomas Becker Roland Beckmann 《Nucleic acids research》2015,43(18):8615-8626
In contrast to bacteria that have two release factors, RF1 and RF2, eukaryotes only possess one unrelated release factor eRF1, which recognizes all three stop codons of the mRNA and hydrolyses the peptidyl-tRNA bond. While the molecular basis for bacterial termination has been elucidated, high-resolution structures of eukaryotic termination complexes have been lacking. Here we present a 3.8 Å structure of a human translation termination complex with eRF1 decoding a UAA(A) stop codon. The complex was formed using the human cytomegalovirus (hCMV) stalling peptide, which perturbs the peptidyltransferase center (PTC) to silence the hydrolysis activity of eRF1. Moreover, unlike sense codons or bacterial stop codons, the UAA stop codon adopts a U-turn-like conformation within a pocket formed by eRF1 and the ribosome. Inducing the U-turn conformation for stop codon recognition rationalizes how decoding by eRF1 includes monitoring geometry in order to discriminate against sense codons. 相似文献
70.