全文获取类型
收费全文 | 4541篇 |
免费 | 323篇 |
国内免费 | 1篇 |
专业分类
4865篇 |
出版年
2023年 | 33篇 |
2022年 | 77篇 |
2021年 | 127篇 |
2020年 | 52篇 |
2019年 | 83篇 |
2018年 | 113篇 |
2017年 | 133篇 |
2016年 | 173篇 |
2015年 | 230篇 |
2014年 | 276篇 |
2013年 | 334篇 |
2012年 | 418篇 |
2011年 | 426篇 |
2010年 | 231篇 |
2009年 | 170篇 |
2008年 | 249篇 |
2007年 | 272篇 |
2006年 | 254篇 |
2005年 | 268篇 |
2004年 | 226篇 |
2003年 | 192篇 |
2002年 | 172篇 |
2001年 | 52篇 |
2000年 | 19篇 |
1999年 | 29篇 |
1998年 | 44篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有4865条查询结果,搜索用时 15 毫秒
31.
32.
Linda Munson Joanna E. Ellington Donald H. Schlafer 《In vitro cellular & developmental biology. Animal》1991,27(1):31-38
Summary Interactions between bovine trophoblastic cell vesicles and bovine endometrial epithelial cells were investigated by light
and electron microscopy and lectin histochemistry in a cell culture model of early blastocyst attachment. Primary lines of
bovine endometrial epithelial cells were polarized by subculturing on substrata and maintaining cultures at the air-medium
interface. Trophoblastic cell vesicles were obtained from elongated Day 14 blastocysts. In co-cultures, trophoblastic cell
vesicles adhered to endometrial epithelial cells through microvillus interdigitation and formation of primitive membrane junctional
complexes. After 3 d in co-culture, a multilayered cellular plaque formed at the trophoblastic cell-endometrial epithelial
cell interface. The type of cells contributing to this local proliferative response could not be identified specifically as
trophoblastic or endometrial cells, and areas of membrane fusion between cells were noted. Ultrastructural features of vesicle
adhesion in cultures were similar to features of conceptus attachment in vivo. Lectins bound to apical membranes of trophoblastic
cells and endometrial epithelial cells in all locations except contact sites between vesicles and endometrial cells. These
findings suggest that local cellular proliferation and membrane fusion between trophoblastic and endometrial epithelial cells
may be early events in conceptus implantation in the cow and these events can be reproduced in culture.
This work was supported by a grant from U.S. Department of Agriculture Animal Health and Disease Program, Washington, DC. 相似文献
33.
34.
Miruna Carmen Barbu Mat Harris Xueyi Shen Stolicyn Aleks Claire Green Carmen Amador Rosie Walker Stewart Morris Mark Adams Anca Sandu Christopher McNeil Gordon Waiter Kathryn Evans Archie Campbell Joanna Wardlaw Douglas Steele Alison Murray David Porteous Andrew McIntosh Heather Whalley 《Epigenetics》2022,17(10):1143
35.
Use of 16S rRNA Gene for Identification of a Broad Range of Clinically Relevant Bacterial Pathogens 总被引:1,自引:0,他引:1
Ramya Srinivasan Ulas Karaoz Marina Volegova Joanna MacKichan Midori Kato-Maeda Steve Miller Rohan Nadarajan Eoin L. Brodie Susan V. Lynch 《PloS one》2015,10(2)
According to World Health Organization statistics of 2011, infectious diseases remain in the top five causes of mortality worldwide. However, despite sophisticated research tools for microbial detection, rapid and accurate molecular diagnostics for identification of infection in humans have not been extensively adopted. Time-consuming culture-based methods remain to the forefront of clinical microbial detection. The 16S rRNA gene, a molecular marker for identification of bacterial species, is ubiquitous to members of this domain and, thanks to ever-expanding databases of sequence information, a useful tool for bacterial identification. In this study, we assembled an extensive repository of clinical isolates (n = 617), representing 30 medically important pathogenic species and originally identified using traditional culture-based or non-16S molecular methods. This strain repository was used to systematically evaluate the ability of 16S rRNA for species level identification. To enable the most accurate species level classification based on the paucity of sequence data accumulated in public databases, we built a Naïve Bayes classifier representing a diverse set of high-quality sequences from medically important bacterial organisms. We show that for species identification, a model-based approach is superior to an alignment based method. Overall, between 16S gene based and clinical identities, our study shows a genus-level concordance rate of 96% and a species-level concordance rate of 87.5%. We point to multiple cases of probable clinical misidentification with traditional culture based identification across a wide range of gram-negative rods and gram-positive cocci as well as common gram-negative cocci. 相似文献
36.
37.
38.
Perlińska-Lenart U Orlowski J Laudy AE Zdebska E Palamarczyk G Kruszewska JS 《Applied and environmental microbiology》2006,72(12):7778-7784
Expression of the Saccharomyces cerevisiae DPM1 gene (coding for dolichylphosphate mannose synthase) in Trichoderma reesei (Hypocrea jecorina) increases the intensity of protein glycosylation and secretion and causes ultrastructural changes in the fungal cell wall. In the present work, we undertook further biochemical and morphological characterization of the DPM1-expressing T. reesei strains. We established that the carbohydrate composition of the fungal cell wall was altered with an increased amount of N-acetylglucosamine, suggesting an increase in chitin content. Calcofluor white staining followed by fluorescence microscopy indicated changes in chitin distribution. Moreover, we also observed a decreased concentration of mannose and alkali-soluble beta-(1,6) glucan. A comparison of protein secretion from protoplasts with that from mycelia showed that the cell wall created a barrier for secretion in the DPM1 transformants. We also discuss the relationships between the observed changes in the cell wall, increased protein glycosylation, and the greater secretory capacity of T. reesei strains expressing the yeast DPM1 gene. 相似文献
39.
Boz.ena Zakry Rafal Milanowski Joanna Empel Piotr Borsuk Robert Gromadka Jan Kwiatowski 《Journal of phycology》2002,38(6):1190-1199
We investigated the similarity of a single Euglena myxocylindracea strain, isolated originally by Bold and MacEntee, to several Euglena geniculata strains on both morphological and DNA levels. We found the three DNA stretches, consisting of fragments coding for the parts of cytoplasmic and chloroplast small subunit rRNA, and the internal transcribed spacer (ITS2) of cytoplasmic rDNA, with the combined length of 4332 nucleotides, are identical in E. myxocylindracea and E. geniculata, strain SAG 1224‐4b. Morphological differences between E. myxocylindracea and any E. geniculata strain examined were well within the range of E. geniculata variability as well. The only difference behind the distinction of E. myxocylindracea from E. geniculata is the presence of the second chloroplast in the latter. However, we were able to induce the appearance of the second chloroplast in the cells of E. myxocylindracea and its disappearance in the cells of E. geniculata by changing the composition of the culture media. We therefore conclude that E. myxocylindracea Bold and MacEntee should be regarded as an environmental form of E. geniculata Dujardin. For the first time the morphology of E. geniculata chloroplasts was shown as revealed by confocal laser microscopy. 相似文献
40.
Josef Trögl Ivana Jirková Petra Zemánková Věra Pilařová Petra Dáňová Jana Pavlorková Pavel Kuráň Jan Popelka Lucie Křiklavová 《Folia microbiologica》2013,58(2):135-140
The content of phospholipid fatty acids (PLFA) was determined in samples of polyvinyl alcohol lenses (Lentikats Biocatalyst, LB) with encapsulated Paracoccus denitrificans withdrawn during long-term denitrification experiments. The total PLFA content correlated highly with specific denitrification activities of LB as well as biomass estimation based on image analyses of microscopic photos. The results confirmed the applicability of PLFA determination for estimation of the amount of living encapsulated microbial biomass during biotechnological applications. 相似文献