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排序方式: 共有262条查询结果,搜索用时 236 毫秒
1.
Maria C. Nieto Elizabeth S. Song Denise McKinney Minnie McMillan Robert S. Goodenow 《Immunogenetics》1989,30(5):361-369
We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association
of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2Ld molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural
alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the
helical region of the alpha-1 domain. H-2Ld class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase
of 34-1-2 cross-reactivity following exchange with human B2m. The H-2Ld hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2Ld molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant
from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human
B2m with H-2Ld can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association
of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability
of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor. 相似文献
2.
The development of mouse oocyte cortical reaction competence is accompanied by major changes in cortical vesicles and not cortical granule depth 总被引:3,自引:0,他引:3
The basis for the incompetence of the cortical reaction in germinal vesicle stage (GV) mouse oocytes was studied by evaluating cortical granules (CGs) and vesicles in GV and mature oocyte cortices. Dark and light CGs had a similar mean distance of 0.4-0.6 micron from the plasma membrane for GV and mature cortices. The cortex of mature oocytes had a large population of membrane-bounded, 0.1-1.0 micron (diameter) vesicles. More than three times as many vesicles were observed in the CG domains of mature oocytes as were observed in GV oocytes. This lack of cortical vesicles (with their potential to store calcium) and not CG depth may account for cortical reaction incompetence in GV oocytes. 相似文献
3.
4.
Functional antagonism between oncoprotein c-Jun and the glucocorticoid receptor 总被引:121,自引:0,他引:121
R Schüle P Rangarajan S Kliewer L J Ransone J Bolado N Yang I M Verma R M Evans 《Cell》1990,62(6):1217-1226
5.
Catarina E. Hioe Denise M. McKinney Jeffrey A. Frelinger Minnie McMillan 《Immunogenetics》1994,40(3):222-229
In order to investigate the role of residues inside and outside the peptide binding cleft of the L2 molecule in peptide presentation to cytotoxic T lymphocytes (CTL), we constructed a series of point mutations in the L
d
gene. We determined the effects of the mutations in the Ld molecule on the binding and recognition of an Ld-restricted CTL epitope derived from the nucleoprotein (NP) of the lymphocytic phoriomeningitis virus (LCMV). Each of the mutations within the Ld peptide binding cleft resulted in a complete loss of CTL recognition. Addition of the LCMV NP peptide to cells expressing these mutants did not increase surface Ld expression, suggesting that the mutations altered peptide binding. Mutations involving pockets D and E within the cleft affected LCMV peptide binding and recognition as drastically as those in pocket B, which was predicted to interact with a main anchor residue of the peptide. In striking contrast, the mutations located outside the cleft did not change either recognition or binding. These results demonstrate that the Ld residues in the peptide binding cleft are the main determinants dictating LCMV NP peptide binding, and that the residues in each of the pockets within the cleft play a role in this interaction. Surprisingly, one mutation outside the peptide binding cleft, T92S, abrogated CTL lysis of target cells treated with the LCMV NP peptide, but not virus-infected cells. These data show that this mutation selectively altered the presentation of the LCMV NP peptide introduced to the cell exogenously, but not endogenously. This implies that the pathway by which peptides associate with class I molecules within the cell differs from that of exogenous peptide binding. 相似文献
6.
Occurrence of a Lysogenic Streptomyces sp. on the Nodule Surface of Black Gram (Vigna mungo (L.) Hepper) 下载免费PDF全文
A lysogenic Streptomyces sp., strain NS.A4, which was isolated from the nodule surface of black gram (Vigna mungo (L.) Hepper), was found to inhibit rhizobia of fast-and slow-growing strains of cowpeas and soybeans. It exhibited plaques when there was a change in cultural conditions. Repeated culturing of the organism in nutrient agar and broth confirmed the infection of Streptomyces sp. strain NS.A4 by an actinophage. Addition of the culture filtrate of Streptomyces sp. strain NS.A4 to shaken broth cultures of three other Streptomyces spp. resulted in phage infection. 相似文献
7.
Fertilization results in cortical granule exocytosis, which is thought to be involved in modifications of the zona pellucida that constitute the zona pellucida block to polyspermy. A previous report demonstrated that a decrease in the number of Lens culinaris agglutinin-staining granules, which are likely to be cortical granules, occurred during in vivo mouse oocyte maturation with arrest at metaphase II, as well as the formation of a cortical granule-free domain in the area of the metaphase II spindle (T. Ducibella, E. Anderson, D.F. Albertini, J. Aalberg, and S. Rangarajan, 1988, Dev. Biol. 130, 184-197). We extend these observations by reporting here that germinal vesicle-intact oocytes matured in vitro to metaphase II in either the absence or the presence of serum develop a cortical granule-free domain and have reduced numbers of cortical granules when compared to germinal vesicle-intact oocytes; these changes are similar to those of oocytes matured in vivo. The reduction in the number of cortical granules requires germinal vesicle breakdown, since it is prevented by dibutyryl cAMP, which inhibits germinal vesicle breakdown in vitro. The ability of oocytes to respond to the calcium ionophore A23187 with a reduction in the number of cortical granules is also associated with meiotic maturation and develops between 7 and 12 hr after initiation of maturation. The maturation-associated reduction in the number of cortical granules is likely to represent cortical granule exocytosis, since this reduction is accompanied by the formation of a cortical granule-free domain and a conversion of ZP2 to ZP2f when the oocytes are matured in vitro in serum-free medium; this zona pellucida modification occurs following fertilization and is thought to be due to cortical granule exocytosis. In contrast, the loss of cortical granules and development of the cortical granule-free domain of oocytes matured in vitro in the presence of serum is not accompanied by the modification of ZP2. The inhibitory effect of serum on the ZP2 modification may afford in vivo a physiological mechanism to prevent a precocious modification of the zona pellucida that could result in a premature block to polyspermy and hence inhibit fertilization. 相似文献
8.
Minnie K. O''Farrell Dorothie Clingan Philip S. Rudland Luis Jimenez De Asua 《Experimental cell research》1979,118(2):311-321
The ability of prostaglandin F2α (PGF2α) and other prostaglandins to stimulate the initiation of DNA synthesis in quiescent cultures of various mouse fibroblastic cell types has been investigated. PGF2α was found to be more effective than the other prostaglandins. Most cell types, with the exception of BALB/c 3T3, responded to PGF2α. Addition of PGF2α in combination with insulin resulted in a synergistic increase in the proportion of cells synthesizing DNA. The effect of nutrients on the stimulation of the initiation of DNA synthesis has been examined in detail; it was found that Swiss 3T3 cells showed a requirement for hypoxanthine and vitamin B12 whereas Swiss 3T6 cells demonstrated a stringent requirement for vitamin B12 only. The effect of prostaglandin precursors, synthetic analogues of the prostaglandin endoperoxides and inhibitors of prostaglandin synthesis was also examined in two cell types. The effect of PGF2α was compared with that of two polypeptide growth factors, epidermal growth factor (EGF) and fibroblast growth factor (FGF) in Swiss 3T6 cells grown in 0.0025% (v/v) serum. In combination with insulin each of these three growth factors stimulated the initiation of DNA synthesis in approximately the same number of cells. 相似文献
9.
10.
Rama Natarajan Wei Bai Vaijayanthy Rangarajan Noe Gonzales Jia-li Gu Linda Lanting Jerry L. Nadler 《Journal of cellular physiology》1996,169(2):391-400
Platelet-derived growth factor BB (PDGF) is a potent mitogen and chemoattractant for vascular smooth muscle cells (VSMC). In the present study, we have examined the effects of PDGF on the 12-lipoxygenase (12-LO) pathway of arachidonate metabolism in porcine aortic VSMC (PVSMC). The rationale for this is previous studies showing that LO products have growth and chemotactic effects in VSMC and that another VSMC growth factor, angiotensin II, is a potent positive regulator of 12-LO activity and expression. We observed that PDGF causes a significant increase in the formation of the 12-LO product, 12-hydroxyeicosatetraenoic acid (12-HETE) in PVSMC. In addition, PDGF also markedly increased leukocyte-type 12-LO messenger RNA and protein expression. PDGF-induced PVSMC migration was inhibited significantly by two LO blockers but not by a cyclooxygenase blocker. Furthermore, although the proliferative effects of PDGF on PVSMC were not altered by cell culture under hyperglycemic conditions (25 mM glucose, HG), the chemotactic effects of PDGF as well as those of 10% fetal calf serum were significantly greater in cells cultured in HG as compared to normal glucose conditions (5.5 mM), thus indicating a potential new mechanism for the accelerated cardiovascular disease usually observed in diabetes. These results indicate a novel mechanism for the biological effects of PDGF in leading to cardiovascular disease. © 1996 Wiley-Liss, Inc. 相似文献