全文获取类型
收费全文 | 21538篇 |
免费 | 2169篇 |
国内免费 | 2301篇 |
出版年
2024年 | 18篇 |
2023年 | 188篇 |
2022年 | 307篇 |
2021年 | 761篇 |
2020年 | 758篇 |
2019年 | 883篇 |
2018年 | 814篇 |
2017年 | 686篇 |
2016年 | 805篇 |
2015年 | 1273篇 |
2014年 | 1608篇 |
2013年 | 1747篇 |
2012年 | 2105篇 |
2011年 | 1956篇 |
2010年 | 1307篇 |
2009年 | 1163篇 |
2008年 | 1526篇 |
2007年 | 1290篇 |
2006年 | 1187篇 |
2005年 | 992篇 |
2004年 | 969篇 |
2003年 | 897篇 |
2002年 | 802篇 |
2001年 | 358篇 |
2000年 | 259篇 |
1999年 | 212篇 |
1998年 | 206篇 |
1997年 | 125篇 |
1996年 | 124篇 |
1995年 | 128篇 |
1994年 | 93篇 |
1993年 | 76篇 |
1992年 | 62篇 |
1991年 | 43篇 |
1990年 | 28篇 |
1989年 | 42篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 4篇 |
1977年 | 6篇 |
1971年 | 4篇 |
1967年 | 4篇 |
1965年 | 4篇 |
1963年 | 3篇 |
1962年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Morphology and Phylogeny of the Soil Ciliate Metopus yantaiensis n. sp. (Ciliophora,Metopida), with Identification of the Intracellular Bacteria 下载免费PDF全文
Atef Omar Qianqian Zhang Songbao Zou Jun Gong 《The Journal of eukaryotic microbiology》2017,64(6):792-805
The morphology and infraciliature of a new ciliate, Metopus yantaiensis n. sp., discovered in coastal soil of northern China, were investigated. It is distinguished from its congeners by a combination of the following features: nuclear apparatus situated in the preoral dome; 18–21 somatic ciliary rows, of which three extend onto the preoral dome (dome kineties); three to five distinctly elongated caudal cilia, and 21–29 adoral polykinetids. The 18S rRNA genes of this new species and two congeners, Metopus contortus and Metopus hasei, were sequenced and phylogenetically analyzed. The new species is more closely related to M. hasei and the clevelandellids than to other congeners; both the genus Metopus and the order Metopida are not monophyletic. In addition, the digestion‐resistant bacteria in the cytoplasm of M. yantaiensis were identified, using a 16S rRNA gene clone library, sequencing, and fluorescence in situ hybridization. The detected intracellular bacteria are affiliated with Sphingomonadales, Rhizobiales, Rickettsiales (Alphaproteobacteria), Pseudomonas (Gammaproteobacteria), Rhodocyclales (Betaproteobacteria), Clostridiales (Firmicutes), and Flavobacteriales (Bacteroidetes). 相似文献
2.
Single Cell Analysis Linking Ribosomal (r)DNA and rRNA Copy Numbers to Cell Size and Growth Rate Provides Insights into Molecular Protistan Ecology 下载免费PDF全文
Ribosomal (r)RNA and rDNA have been golden molecular markers in microbial ecology. However, it remains poorly understood how ribotype copy number (CN)‐based characteristics are linked with diversity, abundance, and activity of protist populations and communities observed at organismal levels. Here, we applied a single‐cell approach to quantify ribotype CNs in two ciliate species reared at different temperatures. We found that in actively growing cells, the per‐cell rDNA and rRNA CNs scaled with cell volume (CV) to 0.44 and 0.58 powers, respectively. The modeled rDNA and rRNA concentrations thus appear to be much higher in smaller than in larger cells. The observed rRNA:rDNA ratio scaled with CV0.14. The maximum growth rate could be well predicted by a combination of per‐cell ribotype CN and temperature. Our empirical data and modeling on single‐cell ribotype scaling are in agreement with both the metabolic theory of ecology and the growth rate hypothesis, providing a quantitative framework for linking cellular rDNA and rRNA CNs with body size, growth (activity), and biomass stoichiometry. This study also demonstrates that the expression rate of rRNA genes is constrained by cell size, and favors biomass rather than abundance‐based interpretation of quantitative ribotype data in population and community ecology of protists. 相似文献
3.
Single Cell Transcriptome Amplification with MALBAC 总被引:1,自引:0,他引:1
4.
5.
6.
7.
Abstract Clostridium perfringens alpha-toxin was produced in a protein-hyperproducing strain, Bacillus brevis 47, by cloning the gene into the constructed expression-secretion vector which has the multiple promoters and the signal peptide coding region of an outer cell wall protein gene. The amount of alpha-toxin produced by the B. brevis 47 transformant carrying the gene was approximately 10 times greater than that produced by a B. subtilis transformant carrying the toxin gene. Biological activities and the N-terminal amino acid sequence of the toxin secreted by the B. brevis 47 transformant were identical to those of wild-type alpha-toxin. 相似文献
8.
9.
Pasupathi Sundaramoorthy Jae Jun Sim Yeong-Su Jang Siddhartha Kumar Mishra Keun-Yeong Jeong Poonam Mander Oh Byung Chul Won-Sik Shim Seung Hyun Oh Ky-Youb Nam Hwan Mook Kim 《PloS one》2015,10(1)
Cancer cell motility is a key phenomenon regulating invasion and metastasis. Focal adhesion kinase (FAK) plays a major role in cellular adhesion and metastasis of various cancers. The relationship between dietary supplementation of calcium and colon cancer has been extensively investigated. However, the effect of calcium (Ca2+) supplementation on calpain-FAK-motility is not clearly understood. We sought to identify the mechanism of FAK cleavage through Ca2+ bound lactate (CaLa), its downstream signaling and role in the motility of human colon cancer cells. We found that treating HCT116 and HT-29 cells with CaLa immediately increased the intracellular Ca2+ (iCa2+) levels for a prolonged period of time. Ca2+ influx induced cleavage of FAK into an N-terminal FAK (FERM domain) in a dose-dependent manner. Phosphorylated FAK (p-FAK) was also cleaved in to its p-N-terminal FAK. CaLa increased colon cancer cells motility. Calpeptin, a calpain inhibitor, reversed the effects of CaLa on FAK and pFAK cleavage in both cancer cell lines. The cleaved FAK translocates into the nucleus and modulates p53 stability through MDM2-associated ubiquitination. CaLa-induced Ca2+ influx increased the motility of colon cancer cells was mediated by calpain activity through FAK and pFAK protein destabilization. In conclusion, these results suggest that careful consideration may be given in deciding dietary Ca2+ supplementation to patient undergoing treatment for metastatic cancer. 相似文献
10.
Janne Alahuhta Sarian Kosten Munemitsu Akasaka Dominique Auderset Mattia M. Azzella Rossano Bolpagni Claudia P. Bove Patricia A. Chambers Eglantine Chappuis John Clayton Mary de Winton Frauke Ecke Esperança Gacia Gana Gecheva Patrick Grillas Jennifer Hauxwell Seppo Hellsten Jan Hjort Mark V. Hoyer Christiane Ilg Agnieszka Kolada Minna Kuoppala Torben Lauridsen En Hua Li Balázs A. Lukács Marit Mjelde Alison Mikulyuk Roger P. Mormul Jun Nishihiro Beat Oertli Laila Rhazi Mouhssine Rhazi Laura Sass Christine Schranz Martin Søndergaard Takashi Yamanouchi Qing Yu Haijun Wang Nigel Willby Xiao Ke Zhang Jani Heino 《Journal of Biogeography》2017,44(8):1758-1769