全文获取类型
收费全文 | 417篇 |
免费 | 25篇 |
专业分类
442篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 63篇 |
2012年 | 24篇 |
2011年 | 25篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 19篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 17篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有442条查询结果,搜索用时 15 毫秒
1.
Chromosomal behavior in starfish (Asterina pectinifera) zygotes under the effect of aphidicolin, an inhibitor of DNA polymerase 总被引:3,自引:0,他引:3
When calf thymus histones were labeled fluorescently and microinjected into oocytes of the starfish, Asterina pectinifera, the labeled histones visualized chromosomes during maturation division and cleavage. In doing so, we confirmed the previously reported phenomenon that chromosomes became incompetent at the first cleavage in the aphidicolin-treated egg, although cleavage itself took place. Moreover, we found that chromosomes were aligned at the equator of the metaphase spindle of the first cleavage and that they did not separate into two groups at all, but made a lump in the middle of the spindle. Chromosomes finally entered one blastomere, although they did not participate in the following karyokinesis. DNA and microtubules were examined by cytochemistry and immunofluorescence in order to investigate the relation between chromosome movement and the microtubular cytoskeleton. The mitotic apparatus developed and grew in the aphidicolin-treated cells in the same manner as those in normal cells without normal chromatin condensation or chromosome movement during the first cleavage. However, the mitotic apparatus consisted of two asters without the spindle formed at subsequent cleavages. Electron microscopic study revealed that chromosomes did not condense normally and kinetochores were not detected during the first cleavage. These results indicate that the dynamic changes in microtubular structures during mitosis have poor relation with the chromosome behavior such as prophase chromosome condensation and anaphase chromosome movement. 相似文献
2.
3.
Makoto Matsuoka Junko Kyozuka Ko Shimamoto Yuriko Kano-Murakami 《The Plant journal : for cell and molecular biology》1994,6(3):311-319
C4 plants have two carboxylases which function in photosynthesis. One, phosphoenolpyruvate carboxylase (PEPC) is localized in mesophyll cells, and the other, ribulose bisphosphate carboxylase (RuBPC) is found in bundle sheath cells. In contrast, C3 plants have only one photosynthetic carboxylase, RuBPC, which is localized in mesophyll cells. The expression of PEPC in C3 mesophyll cells is quite low relative to PEPC expression in C4 mesophyll cells. Two chimeric genes have been constructed consisting of the structural gene encoding β-glucuronidase (GUS) controlled by two promoters from C4 (maize) photosynthetic genes: (i) the PEPC gene (pepc) and (ii) the small subunit of RuBPC (rbcS). These constructs were introduced into a C3 cereal, rice. Both chimeric genes were expressed almost exclusively in mesophyll cells in the leaf blades and leaf sheaths at high levels, and no or very little activity was observed in other cells. The expression of both genes was also regulated by light. These observations indicate that the regulation systems which direct cell-specific and light-inducible expression of pepc and rbcS in C4 plants are also present in C3 plants. Nevertheless, expression of endogenous pepc in C3 plants is very low in C3 mesophyll cells, and the cell specificity of rbcS expression in C3 plants differs from that in C4 plants. Rice nuclear extracts were assayed for DNA-binding protein(s) which interact with a cis-regulatory element in the pepc promoter. Gel-retardation assays indicate that a nuclear protein with similar DNA-binding specificity to a maize nuclear protein is present in rice. The possibility that differences in pepc expression in a C3 plant (rice) and C4 plant (maize) may be the result of changes in cis-acting elements between pepc in rice and maize is discussed. It also appears that differences in the cellular localization of rbcS expression are probably due to changes in a trans-acting factor(s) required for rbcS expression. 相似文献
4.
In Saccharomyces cerevisiae, there are two isoenzymes of fumarate reductase (FRDS1 and FRDS2), encoded by the FRDS and OSM1 genes, respectively. Simultaneous disruption of these two genes results in a growth defect of the yeast under anaerobic conditions, while disruption of the OSM1 gene causes slow growth. However, the metabolic role of these isoenzymes has been unclear until now. In the present study, we found that the anaerobic growth of the strain disrupted for both the FRDS and OSM1 genes was fully restored by adding the oxidized form of methylene blue or phenazine methosulfate, which non-enzymatically oxidize cellular NADH to NAD(+). When methylene blue was added at growth-limiting concentrations, growth was completely arrested after exhaustion of oxidized methylene blue. In the double-disrupted strain, the accumulation of succinate in the supernatant was markedly decreased during anaerobic growth in the presence of methylene blue. These results suggest that fumarate reductase isoenzymes are required for the reoxidation of intracellular NADH under anaerobic conditions, but not aerobic conditions. 相似文献
5.
Two Eucalyptus homologues of the Arabidopsis floral homeotic gene AP1 (EAP1 and EAP2/) show 60–65% homology to AP1. EAP1 and EAP2 are expressed predominantly in flower buds. EAP2 produces two different polypeptides arising from differential splicing at an intron, the shorter EAP2 protein diverging from the longer sequence after amino acid 197 and having a translation stop after residue 206. This truncated protein includes both MADS- and K-box amino acid sequences. Ectopic expression of the EAP1 or either of the two EAP2 polypeptides in Arabidopsis driven by the 35S promoter produces effects similar to the corresponding AP1 construct, causing plants to flower earlier, have shorter bolts and resemble the terminal flower mutant (tfl). 相似文献
6.
Transmembrane mucins Hkr1 and Msb2 are putative osmosensors in the SHO1 branch of yeast HOG pathway 总被引:3,自引:0,他引:3
Tatebayashi K Tanaka K Yang HY Yamamoto K Matsushita Y Tomida T Imai M Saito H 《The EMBO journal》2007,26(15):3521-3533
To cope with life-threatening high osmolarity, yeast activates the high-osmolarity glycerol (HOG) signaling pathway, whose core element is the Hog1 MAP kinase cascade. Activated Hog1 regulates the cell cycle, protein translation, and gene expression. Upstream of the HOG pathway are functionally redundant SLN1 and SHO1 signaling branches. However, neither the osmosensor nor the signal generator of the SHO1 branch has been clearly defined. Here, we show that the mucin-like transmembrane proteins Hkr1 and Msb2 are the potential osmosensors for the SHO1 branch. Hyperactive forms of Hkr1 and Msb2 can activate the HOG pathway only in the presence of Sho1, whereas a hyperactive Sho1 mutant activates the HOG pathway in the absence of both Hkr1 and Msb2, indicating that Hkr1 and Msb2 are the most upstream elements known so far in the SHO1 branch. Hkr1 and Msb2 individually form a complex with Sho1, and, upon high external osmolarity stress, appear to induce Sho1 to generate an intracellular signal. Furthermore, Msb2, but not Hkr1, can also generate an intracellular signal in a Sho1-independent manner. 相似文献
7.
Kobayashi T Amemiya K Takeuchi K Tsujioka T Tominaga K Hirabayashi M Ishikawa H Fukui Y Hochi S 《Zygote (Cambridge, England)》2006,14(1):45-51
Using an interspecies microinsemination assay with bovine oocytes, it was examined whether centrosomes of Antarctic minke whale spermatozoa function as the microtubule-organizing centre (MTOC). Bull and rat spermatozoa were used as positive and negative controls, respectively. Vitrified-warmed bovine mature oocytes were subjected to immunostaining against alpha-tubulin 4-6 h after intracytoplasmic injection (ICSI) of 5 mM dithiothreitol-treated spermatozoa. Aster formation occurred from whale spermatozoa (33%) and bull spermatozoa (33%), but very little from rat spermatozoa (3%). Activation treatment for the microinseminated oocytes with 7% ethanol + 2 mM 6-dimethylaminopurine resulted in a similar proportion of oocytes forming a whale sperm aster (35% vs 27% in the non-treated group; 4 h after ICSI) but a significantly larger aster (ratio of aster diameter to oocyte diameter, 0.57 vs 0.30 in the non-treated group). These results indicate that the centrosome introduced into bovine oocytes by whale spermatozoa contributes to the MTOC and that assembly of the microtubule network is promoted by oocyte activation. 相似文献
8.
The late-third-instar labial disc is comprised of two disc-proper cell layers, one representing mainly the ventral half of the anterior compartment (L-layer) and the other, the dorsal half of the anterior compartment and most, if not all, of the posterior compartment (M-layer). In the L-layer, Distal-less represses homothorax whereas no Distal-less-dependent homothorax repression occurs in the M-layer where Distal-less is coexpressed with homothorax. In wild-type labial discs, clawless, one of the two homeobox genes expressed in distal cells receiving maximum (Decapentaplegic+Wingless) signaling activity in leg and antennal discs, is specifically repressed by proboscipedia. A fate map, inferred from data on basic patterning gene expression in larval and pupal stages and mutant phenotypes, indicates the inner surface of the labial palpus, which includes the pseudotracheal region, to be a derivative of the distal portion of the M-layer expressing wingless, patched, Distal-less and homothorax. The outer surface of the labial palpus with more than 30 taste bristles derives from an L-layer area consisting of dorsal portions of the anterior and posterior compartments, each expressing Distal-less. Our analysis also indicates that, in adults and pupae, the anterior-posterior boundary, dividing roughly equally the outer surface of the distiproboscis, runs along the outer circumference of the inner surface of distiproboscis. 相似文献
9.
10.