全文获取类型
收费全文 | 2744篇 |
免费 | 178篇 |
国内免费 | 3篇 |
专业分类
2925篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 31篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 55篇 |
2015年 | 100篇 |
2014年 | 92篇 |
2013年 | 148篇 |
2012年 | 211篇 |
2011年 | 201篇 |
2010年 | 125篇 |
2009年 | 105篇 |
2008年 | 152篇 |
2007年 | 193篇 |
2006年 | 160篇 |
2005年 | 143篇 |
2004年 | 158篇 |
2003年 | 169篇 |
2002年 | 146篇 |
2001年 | 22篇 |
2000年 | 12篇 |
1999年 | 30篇 |
1998年 | 32篇 |
1997年 | 32篇 |
1996年 | 25篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 27篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1977年 | 13篇 |
1975年 | 13篇 |
1974年 | 10篇 |
1969年 | 8篇 |
1968年 | 8篇 |
排序方式: 共有2925条查询结果,搜索用时 15 毫秒
51.
In crude extracts of the unicellular green alga Chlorella kessleri Fott et Novákóva grown in red light the activity of the glycolytic enzyme phosphofructokinase (PFK, EC 2.7.1.11) is about 40% higher compared to white light conditions giving the same dry matter production. Application of cycloheximide and density labelling with D2 O indicate that this increase depends on the de novo synthesis of the enzyme: Twelve h of illumination at a fluence rate of 7 × 1018 quanta m−2 s−1 (11.6 μmol m−2 s−1 ) suffice to saturate the effect. In autotrophically grown algae maximal increase in enzyme saturate the effect. In autotrophically grown algae maximal increase in enzyme activity is reached in light of 680 nm, while in 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU)-poisoned, glucose-fed cells, light of wavelengths around 727 nm is most effective. Involvement of a phytochrome-like photoreceptor is discussed. 相似文献
52.
Roel Hermsen Joep de Ligt Wim Spee Francis Blokzijl Sebastian Sch?fer Eleonora Adami Sander Boymans Stephen Flink Ruben van Boxtel Robin H van der Weide Tim Aitman Norbert Hübner Marieke Simonis Boris Tabakoff Victor Guryev Edwin Cuppen 《BMC genomics》2015,16(1)
Background
Since the completion of the rat reference genome in 2003, whole-genome sequencing data from more than 40 rat strains have become available. These data represent the broad range of strains that are used in rat research including commonly used substrains. Currently, this wealth of information cannot be used to its full extent, because the variety of different variant calling algorithms employed by different groups impairs comparison between strains. In addition, all rat whole genome sequencing studies to date used an outdated reference genome for analysis (RGSC3.4 released in 2004).Results
Here we present a comprehensive, multi-sample and uniformly called set of genetic variants in 40 rat strains, including 19 substrains. We reanalyzed all primary data using a recent version of the rat reference assembly (RGSC5.0 released in 2012) and identified over 12 million genomic variants (SNVs, indels and structural variants) among the 40 strains. 28,318 SNVs are specific to individual substrains, which may be explained by introgression from other unsequenced strains and ongoing evolution by genetic drift. Substrain SNVs may have a larger predicted functional impact compared to older shared SNVs.Conclusions
In summary we present a comprehensive catalog of uniformly analyzed genetic variants among 40 widely used rat inbred strains based on the RGSC5.0 assembly. This represents a valuable resource, which will facilitate rat functional genomic research. In line with previous observations, our genome-wide analyses do not show evidence for contribution of multiple ancestral founder rat subspecies to the currently used rat inbred strains, as is the case for mouse. In addition, we find that the degree of substrain variation is highly variable between strains, which is of importance for the correct interpretation of experimental data from different labs.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1594-1) contains supplementary material, which is available to authorized users. 相似文献53.
Robarge MJ Bom DC Tumey LN Varga N Gleason E Silver D Song J Murphy SM Ekema G Doucette C Hanniford D Palmer M Pawlowski G Danzig J Loftus M Hunady K Sherf BA Mays RW Stricker-Krongrad A Brunden KR Harrington JJ Bennani YL 《Bioorganic & medicinal chemistry letters》2005,15(6):1749-1753
The chemoattractant receptor-homologous molecule expressed on T(H)2 cells (CRTH-2), also found on eosinophils and basophils, is a prostaglandin D2 receptor involved in the recruitment of these cell types during an inflammatory response. In this report, we describe the synthesis and optimization of a ramatroban isostere that is a selective and potent antagonist of CRTH-2 which may be useful in the treatment of certain diseases. 相似文献
54.
Weidong He Luc Van Puyvelde Jan Bosselaers Norbert De Kimpe Marc Van Der Flaas Annemie Roymans 《Biofouling》2013,29(3):221-226
A screening of antifouling activity from plants extracts led to selection and further study of Maesa lanceolata Forssk. Two p‐benzoquinone compounds were isolated from the fruits and found to be active against Artemia salina. The anti‐crustacean activity of both p‐benzoquinones is reported for the first time. 相似文献
55.
56.
Bär H Mücke N Ringler P Müller SA Kreplak L Katus HA Aebi U Herrmann H 《Journal of molecular biology》2006,360(5):1031-1042
It has been documented that mutations in the human desmin gene lead to a severe type of myofibrillar myopathy, termed more specifically desminopathy, which affects cardiac and skeletal as well as smooth muscle. We showed recently that 14 recombinant versions of these disease-causing desmin variants, all involving single amino acid substitutions in the alpha-helical rod domain, interfere with in vitro filament formation at distinct stages of the assembly process. We now provide mechanistic details of how these mutations affect the filament assembly process by employing analytical ultracentrifugation, time-lapse electron microscopy of negatively stained and glycerol-sprayed/low-angle rotary metal-shadowed samples, quantitative scanning transmission electron microscopy, and viscometric studies. In particular, the soluble assembly intermediates of two of the mutated proteins exhibit unusually high s-values, compatible with octamers and other higher-order complexes. Moreover, several of the six filament-forming mutant variants deviated considerably from wild-type desmin with respect to their filament diameters and mass-per-length values. In the heteropolymeric situation with wild-type desmin, four of the mutant variants caused a pronounced "hyper-assembly", when assayed by viscometry. This indicates that the various mutations may cause abortion of filament formation by the mutant protein at distinct stages, and that some of them interfere severely with the assembly of wild-type desmin. Taken together, our findings provide novel insights into the basic intermediate filament assembly mechanisms and offer clues as to how amino acid changes within the desmin rod domain may interfere with the normal structural organization of the muscle cytoskeleton, eventually leading to desminopathy. 相似文献
57.
Norbert Madry Rainer Zocher Karola Grodzki Horst Kleinkauf 《Applied microbiology and biotechnology》1984,20(2):83-86
Summary The multifunctional enzyme enniatin synthetase was immobilized by adsorption to propyl agarose. The immobilized multienzyme retained 45% of the activity of the free enzyme; an operational half-life of about 15 h was estimated. Selective synthesis of several different enniatin homologues was achieved with propyl agarose-bound enniatin synthetase. In addition to enniatin A, B, and C formation, a selective synthesis of non-naturally occurring depsipeptides, containing norvaline, norleucine, or -aminobutyric acid as sole amino acid moieties, was observed. 相似文献
58.
59.
A mammary gland EST showing linkage disequilibrium to a milk production QTL on bovine Chromosome 14 总被引:10,自引:0,他引:10
Christian Looft Norbert Reinsch Christina Karall-Albrecht Sven Paul Maren Brink Hauke Thomsen Gudrun Brockmann Christa Kühn Manfred Schwerin Ernst Kalm 《Mammalian genome》2001,12(8):646-650
As part of a genome scan, ESTs derived from mammary gland tissue of a lactating cow were used as candidate genes for quantitative
trait loci (QTL), affecting milk production traits. Resource families were genotyped with 247 microsatellite markers and 4
polymorphic ESTs. It was shown by linkage analysis that one of these ESTs, KIEL_E8, mapped to the centromeric region of bovine
Chromosome (Chr) 14. Regression analysis revealed the presence of a QTL, with significant effect on milk production, in this
chromosome region, and analysis of variance showed no significant interaction of marker genotype and family. The estimated
significant differences between homozygous marker genotypes were 140 kg milk, −5.02 kg fat yield, and 2.58 kg protein yield
for the first 100 days of lactation. Thus, there was strong evidence for a complete or nearly complete linkage disequilibrium
between KIEL_E8 and the QTL. To identify the biological function of KIEL_E8, we extended the sequence for 869 bp by 5′-RACE.
A 560-bp fragment of this shows a 90.9% similarity to a gene encoding a cysteine- and histidine-rich cytoplasmic protein in
mouse. Although such a protein may have a regulatory function for lactation and a linkage disequilibrium between the EST marker
and the QTL has been observed, it remains to be elucidated whether they are identical or not. Nevertheless, KIEL_E8 will be
an efficient marker to perform marker-assisted selection in the Holstein-Friesian population.
Received 20 October 2000 / Accepted: 11 April 2001 相似文献
60.
Ernst Rüdin (1874–1952) was the founder of psychiatric genetics and was also a founder of the German racial hygiene movement. Throughout his long career he played a major role in promoting eugenic ideas and policies in Germany, including helping formulate the 1933 Nazi eugenic sterilization law and other governmental policies directed against the alleged carriers of genetic defects. In the 1940s Rüdin supported the killing of children and mental patients under a Nazi program euphemistically called “Euthanasia.” The authors document these crimes and discuss their implications, and also present translations of two publications Rüdin co-authored in 1938 showing his strong support for Hitler and his policies. The authors also document what they see as revisionist historical accounts by leading psychiatric genetic authors. They outline three categories of contemporary psychiatric genetic accounts of Rüdin and his work: (A) those who write about German psychiatric genetics in the Nazi period, but either fail to mention Rüdin at all, or cast him in a favorable light; (B) those who acknowledge that Rüdin helped promote eugenic sterilization and/or may have worked with the Nazis, but generally paint a positive picture of Rüdin’s research and fail to mention his participation in the “euthanasia” killing program; and (C) those who have written that Rüdin committed and supported unspeakable atrocities. The authors conclude by calling on the leaders of psychiatric genetics to produce a detailed and complete account of their field’s history, including all of the documented crimes committed by Rüdin and his associates. 相似文献