全文获取类型
收费全文 | 345篇 |
免费 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 30篇 |
2014年 | 20篇 |
2013年 | 23篇 |
2012年 | 29篇 |
2011年 | 35篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 15篇 |
2007年 | 22篇 |
2006年 | 19篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1954年 | 2篇 |
1936年 | 1篇 |
1903年 | 1篇 |
1887年 | 1篇 |
排序方式: 共有380条查询结果,搜索用时 46 毫秒
91.
92.
93.
94.
Ngamkitidechakul C Warejcka DJ Burke JM O'Brien WJ Twining SS 《The Journal of biological chemistry》2003,278(34):31796-31806
Maspin, an ov-serpin, inhibits tumor invasion and induces cell adhesion to extracellular matrix molecules. Here, we use maspin/ovalbumin chimeric proteins and the maspin reactive site loop (RSL) peptide to characterize the role of the RSL in maspin-mediated functions. Replacement of the RSL plus the C-terminal region or the RSL alone of maspin with that of ovalbumin resulted in the loss of the stimulatory effect on adhesion of corneal stromal cells to type I collagen, fibronectin, and laminin and of mammary carcinoma MDA-MB-231 cells to fibronectin. Maspin with ovalbumin as the C-terminal region retained activity, suggesting the maspin C-terminal polypeptide is not required. An R340Q mutant retained full maspin activity; however, an R340A mutant lost activity. This indicates the arginine side chain at the putative P1 site forms a hydrogen bond and not an ionic bond. The RSL peptide (P10-P5', amino acids 330-345) alone induced cell-matrix adhesion of mammary carcinoma cells and corneal stromal cells and inhibited invasion of the carcinoma cells. Substitution of the RSL of ovalbumin with that of maspin converted inactive ovalbumin into a fully active molecule. Maspin bound specifically to the surface of the mammary carcinoma cells with a kd of 367 +/- 67 nM and 32.0 +/- 2.2 x 10(6) binding sites/cell. The maspin RSL peptide inhibited binding, suggesting the RSL is involved in maspin binding to cells. Sufficiency of the maspin RSL for activity suggests the mechanism by which maspin regulates cell-matrix adhesion and tumor cell invasion does not involve the serpin mechanism of protease inhibition. 相似文献
95.
Oxygen Requirement and Inhibition of C4
Photosynthesis
: An Analysis of C4 Plants Deficient in the
C3 and C4 Cycles 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jo?o P. Maroco Maurice S.B. Ku Peter J. Lea Louisa V. Dever Richard C. Leegood Robert T. Furbank Gerald E. Edwards 《Plant physiology》1998,116(2):823-832
The basis for O2 sensitivity of C4 photosynthesis was evaluated using a C4-cycle-limited mutant of Amaranthus edulis (a phosphoenolpyruvate carboxylase-deficient mutant), and a C3-cycle-limited transformant of Flaveria bidentis (an antisense ribulose-1,5-bisphosphate carboxylase/oxygenase [Rubisco] small subunit transformant). Data obtained with the C4-cycle-limited mutant showed that atmospheric levels of O2 (20 kPa) caused increased inhibition of photosynthesis as a result of higher levels of photorespiration. The optimal O2 partial pressure for photosynthesis was reduced from approximately 5 kPa O2 to 1 to 2 kPa O2, becoming similar to that of C3 plants. Therefore, the higher O2 requirement for optimal C4 photosynthesis is specifically associated with the C4 function. With the Rubisco-limited F. bidentis, there was less inhibition of photosynthesis by supraoptimal levels of O2 than in the wild type. When CO2 fixation by Rubisco is limited, an increase in the CO2 concentration in bundle-sheath cells via the C4 cycle may further reduce the oxygenase activity of Rubisco and decrease the inhibition of photosynthesis by high partial pressures of O2 while increasing CO2 leakage and overcycling of the C4 pathway. These results indicate that in C4 plants the investment in the C3 and C4 cycles must be balanced for maximum efficiency. 相似文献
96.
Louisa V. Dever Mark Pearson Robert J. Ireland Richard C. Leegood Peter J. Lea 《Planta》1998,206(4):649-656
A mutant of Amaranthus edulis (Speg.) lacking activity of the C4 leaf form of NAD-malic enzyme (ME; EC 1.1.1.39) has been isolated. Homozygous mutant (5% wild-type ME activity) and heterozygous
(50% wild-type ME activity) F2 plants were shown to contain both the α and β NAD-ME subunits in similar amounts to those detected in the wild-type leaves.
The rate of photosynthetic CO2 assimilation was reduced in the homozygous mutant to 5% of that observed for the wild-type leaves. Other C4 enzymes were not down-regulated in the mutant plants. There was little difference in photosynthetic rate of the heterozygous
plants compared to the wild-type, suggesting that NAD-ME exerts little control over the rate of C4 photosynthesis, and that in the wild-type the enzyme has a very low control coefficient. The activity loss in the heterozygote
may therefore be compensated by regulatory mechanisms that increase the activity of the enzyme in vivo. Data for bundle-sheath
strands indicated that although the homozygous mutants were able to oxidise malate via the Krebs cycle, they were unable to
convert malate to pyruvate and alanine via NAD-ME.
Received: 2 April 1998 / Accepted: 7 May 1998 相似文献
97.
K Okuda P R Christadoss S Twining M Z Atassi C S David 《Journal of immunology (Baltimore, Md. : 1950)》1978,121(3):866-868
Studies on the genetic control of immune response to sperm whale myoglobin were initiated. As demonstrated in this paper, the T lymphocyte proliferative response to whale myoglobin is under H-2-linked Ir gene control. Mice of H-2d, H-2f, and H-2s haplotypes were high responders to the myoglobin, whereas haplotypes H-2b, H-2k, H-2p, H-2q, and H-2r were low responders. The Ir gene(s) was localized between H-2K and H2D regions, since the recombinant strain A.TL (KsIkSkDd) was a low responder and A.TH (KsIsSsDd) was a high responder. Further studies with recombinant strains revealed that the expression of the high-responder I-Ad or Ias alleles was sufficient to give a good response, since strains D2.GD (d d b b b b b b) and B10.HTT (s s s s k k k d) were high responders. The expression of the I-Cd allele in strains B10.A (k k k k k d d d) and B10.A(5R) (b b b k k d d d) also gave high response, and thus suggested a second Ir gene, derived from the H-2d haplotype. The finding that expression of the I-Cs allele in B10.S(8R) (k k ? ? s s s s) did not result in high response suggests the lack of the second Ir gene in the high-responder H-2s haplotype. 相似文献
98.
Daniel Bronder Anthony Tighe Darawalee Wangsa Dali Zong Thomas J. Meyer Ren Wardenaar Paul Minshall Daniela Hirsch Kerstin Heselmeyer-Haddad Louisa Nelson Diana Spierings Joanne C. McGrail Maggie Cam Andr Nussenzweig Floris Foijer Thomas Ried Stephen S. Taylor 《Disease models & mechanisms》2021,14(11)
99.
Sajad Sofi Louisa Williamson Gabrielle L. Turvey Charlotte Scoynes Claire Hirst Jonathan Godwin Neil Brockdorff Justin Ainscough Dawn Coverley 《The Journal of cell biology》2022,221(4)
CIZ1 forms large assemblies at the inactive X chromosome (Xi) in female fibroblasts in an Xist lncRNA-dependent manner and is required for accurate maintenance of polycomb targets genome-wide. Here we address requirements for assembly formation and show that CIZ1 undergoes two direct interactions with Xist, via independent N- and C-terminal domains. Interaction with Xist, assembly at Xi, and complexity of self-assemblies formed in vitro are modulated by two alternatively spliced glutamine-rich prion-like domains (PLD1 and 2). PLD2 is dispensable for accumulation at existing CIZ1–Xi assemblies in wild-type cells but is required in CIZ1-null cells where targeting, assembly, and enrichment for H3K27me3 and H2AK119ub occur de novo. In contrast, PLD1 is required for both de novo assembly and accumulation at preexisting assemblies and, in vitro, drives formation of a stable fibrillar network. Together they impart affinity for RNA and a complex relationship with repeat E of Xist. These data show that alternative splicing of two PLDs modulates CIZ1’s ability to build large RNA–protein assemblies. 相似文献
100.
Insulin has been shown to acutely regulate hepatic apolipoprotein B (apoB) secretion at both translational and post-translational levels; however, mechanisms of apoB mRNA translational control are largely unknown. Recent studies of apoB untranslated regions (UTRs) revealed a potentially important role for cis-trans interactions at the 5' and 3' UTRs. In the present paper, deletion constructs of the UTR regions of apoB revealed that the 5' UTR was necessary and sufficient for insulin to inhibit synthesis of apoB15. Metabolic radiolabeling and in vitro translation experiments in the presence of protease inhibitors confirmed that the effect of insulin on the apoB 5' UTR was translational in nature. Using the nondenaturing electrophoretic mobility shift assay (EMSA), protein-RNA complexes were detected binding to the apoB 5' and 3' UTRs. Denaturing EMSA identified a 110-kDa protein interacting at the 5' UTR. Nondenaturing EMSA determined that insulin altered binding of large protein complexes to the 5' UTR. Binding specificity was determined by competition with both specific and nonspecific competitors. Insulin treatment decreased binding of the 110-kDa protein to the 5' UTR as visualized by EMSA. Absence of insulin increased binding of this trans-acting factor to the 5' UTR by 2-fold. Analysis of the 3' UTR showed no significant insulin-mediated changes in binding of trans-acting factors. We thus propose the existence of a novel RNA-binding insulin-sensitive factor that binds to the 5' UTR and may regulate apoB mRNA translation. Perturbations in hepatic insulin signaling as observed in insulin-resistant states may alter cis-trans interactions at the 5' UTR, leading to alterations in the rate of apoB mRNA translation, thus contributing to apoB-lipoprotein overproduction. 相似文献