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41.
Jun?Keun?ChangEmail author Yun?Seok?Heo Hyunwoo?Bang Keunchang?Cho Seok?Chung Chanil?Chung Dong?Chul?Han 《Biotechnology and Bioprocess Engineering》2003,8(4):233-239
For the quantitative analysis of an unknown sample a calibration curve should be obtained, as analytical instruments give
relative, rather than absolute measurements. Therefore, researchers should make standard samples with various known concentrations,
measure each standard and the unknown sample, and then determine the concentration of the unknown by comparing the measured
value to those of the standards. These procedures are tedious and time-consuming. Therefore, we developed a polymer based
microfluidic device from polydimethylsiloxane, which integrates serial dilution and capillary electrophoresis functions in
a single device. The integrated microchip can provide a one-step analytical tool, and thus replace the complex experimental
procedures. Two plastic syringes, one containing a buffer solution and the other a standard solution, were connected to two
inlet holes on a microchip, and pushed by a hydrodynamic force. The standard sample is serially diluted to various concentrations
through the microfluidic networks. The diluted samples are sequentially introduced through microchannels by electro-osmotic
force, and their laser-induced fluorescence signals measured by capillary electrophoresis. We demonstrate the integrated microchip
performance by measuring the fluorescence signals of fluorescein at various concentrations. The calibration curve obtained
from the electropherograms showed the expected linearity. 相似文献
42.
Signaling proteins from the same family can have markedly different roles in a given cellular context. Here, we show that expression of one hundred constitutively active human small GTPases induced cell morphologies that fell into nine distinct classes. We developed an algorithm for pairs of classes that predicted amino acid positions that can be exchanged to create mutants with switched functionality. The algorithm was validated by creating switch-of-function mutants for Rac1, CDC42, H-Ras, RalA, Rap2B, and R-Ras3. Contrary to expectations, the relevant residues were mostly outside known interaction surfaces and were structurally far apart from each other. Our study shows that specificity in protein families can be explored by combining genome-wide experimental functional classification with the creation of switch-of-function mutants. 相似文献
43.
Testing the robustness of the new Haseman-Elston quantitative-trait loci-mapping procedure 下载免费PDF全文
Variance components (VC) techniques have emerged as among the more powerful methods for detection of quantitative-trait loci (QTL) in linkage analysis. Allison et al. found that, with particularly marked leptokurtosis in the phenotypic distribution and moderate-to-high residual sibling correlation, maximum likelihood (ML) VC methods may produce a severe excess of type I errors. The new Haseman-Elston (NHE) method is a least-squares-based VC method for mapping of QTL in sib pairs (Elston et al.). Using simulation, we investigate the robustness of the NHE to marked nonnormality, by means of the same distributions and worst-case conditions identified by Allison et al. for the ML approach (i.e., 100 pairs; high residual sibling correlation). Results showed that, when marked nonnormality is present, the NHE can be used without severe type I error-rate inflation, even at very small alpha levels. 相似文献
44.
S.-J. Heo K. Tatebayashi J. Kato H. Ikeda 《Molecular genetics and genomics : MGG》1998,257(2):149-156
The Saccharomyces cerevisiae gene RHC21 is a homologue of the fission yeast rad21 +gene, which affects the sensitivity of cells to γ-irradiation and is essential for cell growth in S. pombe. Disruption of the RHC21 gene showed that it is also essential in S. cerevisiae. To examine its function in cell growth further, we have isolated temperature-sensitive mutants for the RHC21 gene and characterized one of them, termed rhc21-sk16. When this mutant was incubated at 36°?C, the percentage of large-budded cells was increased. Most of the large-budded cells had aberrant nuclear structures, such as unequally extended nuclear DNA with incompletely elongated spindles across the mother-daughter neck or only in a mother cell. Furthermore, a circular minichromosome is more unstable in the mutant than in the wild-type, even at 25°?C. Flow cytometry showed that the bulk of DNA replication takes place normally at the restrictive temperature in the mutant. These results indicated that the RHC21 gene is required for proper segregation of the chromosomes. In addition, we found that the mutant is sensitive not only to UV radiation and γ-rays but also to the antimicrotubule agent nocodazole at 25°?C. This suggests that the RHC21 gene is involved in the microtubule function. We discuss how the RHC21 gene product may be involved in chromosome segregation and microtubule function. 相似文献
45.
46.
Phage libraries displaying cDNA or random peptides have been used for profiling autoantibodies in cancer. The detection of
autoantibodies in human sera using phages displaying specific epitopes is usually performed by phage-immobilized ELISAs which
can detect specific antibodies without identification of whole antigens. However, these ELISAs can give feeble detection signals
that are indistinguishable from background signals which are caused by human sera. To improve the usefulness of phage ELISA
for human sera, the conditions for each step in phage ELISA were optimized. The antigenicity of phage antigens was maximal
when using coating buffer of neutral pH. By using protein-free blocking buffer and pre-adsorbing human sera with phage host
cell ER2738 extracts significantly decreased non-specific signals. Finally, when these conditions were applied to phage ELISA
using K10P1, the values of the negative controls were concentrated near cutoff values, which made the assay more reliable.
The optimized phage ELISA conditions described here would increase the efficacy of detection specific autoantibodies in human
sera. 相似文献
47.
Achene morphology of Saussurea species (Asteraceae,Cardueae) in Korea and its systematic implications 下载免费PDF全文
Balkrishna Ghimire Mi Jin Jeong Kyung Mee Lee Kweon Heo Cheul Ho Lee Gang Uk Suh 《Botanical journal of the Linnean Society. Linnean Society of London》2016,181(4):692-710
Achene size and shape, surface sculpturing, and pericarp and testa wall structure of 23 Korean Saussurea spp. were investigated using scanning electron microscopy (SEM) and light microscopy to evaluate the infrageneric relationships and assess their systematic significance. Achene size categories and thickness of the testa epidermis were distinguished using biometric measurements. Four basic types of surface pattern were observed: (1) lineate; (2) striate; (3) reticulate; and (4) colliculate. Saussurea rorinsanensis was found to have some unique achene characteristics, such as a fusiform achene, uniform pappus, presence of epidermal hairs and tangentially elongated, narrow testa epidermal cells. The characteristic achene features for species were found to be achene size and shape, hilum position, surface sculpture, pappus composition, morphology of the pericarp wall and thickness of the testa epidermis. Based on 16 morphological and achene characters, a cladistic analysis resolved three well‐supported clades, with S. eriophylla as the first‐branching taxon. Saussurea pulchella and S. japonica, both belonging to Saussurea subgenus Theodorea, were distant from each other in the 50% majority rule consensus tree and the character distribution cladogram. This cladistic analysis of achene morphology and anatomy should be regarded as giving us a tentative picture of the phylogenetics of Saussurea, and this study may serve as a reference for future hypotheses and studies on the characterization and classification of Saussurea spp. in Korea. 相似文献
48.
This study examined the effects of high glucose on cell proliferation and its related signal pathways using mouse embryonic stem (ES) cells. Here, we showed that high glucose level significantly increased [3H]thymidine incorporation, BrdU incorporation, the number of cells, [3H]leucine, and [3H]proline incorporation in a time-( >3 hr) and dose-(> 25 mM) dependent manner. Moreover, high glucose level increased the cellular reactive oxygen species (ROS), Akt, and mitogen-activated protein kinases (MAPKs) phosphorylation. Subsequently, these signaling molecules involved in high glucose-induced increase of [3H]thymidine incorporation. High glucose level also increased cyclin D1, cyclin E, cyclin-dependent kinase (CDK) 2, and CDK 4 protein levels, which is cell cycle regulatory proteins acting in G1-S phase of cell cycle. Inhibition of phosphatidylinositol 3-kinase (PI3-K) (LY 294002: PI3-kinase inhibitor, 10(-6) M), Akt (Akt inhibitor, 10(-5) M), and p44/42 MAPKs (PD 98059: MEK inhibitor, 10(-5) M) decreased these proteins. High glucose level phosphorylated the RB protein, which was decreased by inhibition of PI3-K and Akt. In conclusion, high glucose level stimulates mouse ES cell proliferation via the PI3-K/Akt and MAPKs pathways. 相似文献
49.
50.
Embryonic germ (EG) cells are undifferentiated stem cells isolated from cultured primordial germ cells (PGC). Porcine EG cell lines with capacities of both in vitro and in vivo differentiation have been established. Because EG cells can be cultured indefinitely in an undifferentiated state, they may be more suitable for nuclear donor cells in nuclear transfer (NT) than somatic cells that have limited lifespan in primary culture. Use of EG cells could be particularly advantageous to provide an inexhaustible source of transgenic cells for NT. In this study the efficiencies of transgenesis and NT using porcine fetal fibroblasts and EG cells were compared. The rate of development to the blastocyst stage was significantly higher in EG cell NT than somatic cell NT (94 of 518, 18.2% vs. 72 of 501, 14.4%). To investigate if EG cells can be used for transgenesis in pigs, green fluorescent protein (GFP) gene was introduced into porcine EG cells. Nuclear transfer embryos using transfected EG cells gave rise to blastocysts (29 of 137, 21.2%) expressing GFP based on observation under fluorescence microscope. The results obtained from the present study suggest that EG cell NT may have advantages over somatic cell NT, and transgenic pigs may be produced using EG cells. 相似文献