全文获取类型
收费全文 | 1720篇 |
免费 | 144篇 |
国内免费 | 1篇 |
出版年
2023年 | 14篇 |
2022年 | 27篇 |
2021年 | 46篇 |
2020年 | 28篇 |
2019年 | 30篇 |
2018年 | 38篇 |
2017年 | 37篇 |
2016年 | 46篇 |
2015年 | 83篇 |
2014年 | 92篇 |
2013年 | 120篇 |
2012年 | 141篇 |
2011年 | 159篇 |
2010年 | 77篇 |
2009年 | 79篇 |
2008年 | 88篇 |
2007年 | 97篇 |
2006年 | 65篇 |
2005年 | 89篇 |
2004年 | 62篇 |
2003年 | 55篇 |
2002年 | 67篇 |
2001年 | 28篇 |
2000年 | 22篇 |
1999年 | 26篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1979年 | 6篇 |
1977年 | 6篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 8篇 |
1970年 | 4篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1966年 | 4篇 |
1965年 | 7篇 |
排序方式: 共有1865条查询结果,搜索用时 31 毫秒
11.
12.
13.
Acid-soluble nucleotides of pinto bean leaves at different stages of development 总被引:4,自引:3,他引:1
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)
Acid-soluble nucleotides of unifoliate leaves of Pinto bean plants (Phaseolus vulgaris L.) were determined at young, mature, and senescent stages of development. At least 25 components could be distinguished on the basis of inorganic phosphorus determinations and 37 or more fractions on the basis of 32P labeling, with adenosine di- and triphosphates accounting for 60% of the total moles of nucleotide. The total nucleotide P and inorganic P, on a fresh weight basis, decreased about 44% between each stage of leaf development, but decrements in the levels of individual nucleotides varied from this over-all pattern. 相似文献
14.
Summary In the brain of the cockroach Periplaneta americana, the beta lobes of the corpora pedunculata respond with an intense positive reaction to a specific fluorescence histochemical method for catecholamines. The fluorescence reaction disappears completely after prolonged treatment of the cockroaches with reserpine. An ultrastructural examination of the beta lobes in formaldehyde-glutaraldehyde-osmium fixed preparations reveals the presence of two types of fibres: 1) Fibres and nerve endings containing small clear vesicles and sligthly larger vesicles with a semi-dense content. The appearance and size distribution of these vesicles ist not affected by treatment with reserpine. 2) Fibres containing larger and denser vesicles, but practically no clear vesicles. The size distribution of these dense vesicles is only slightly affected by treatment of the cockroaches with reserpine.If brain slices are incubated in a medium containing noradrenaline or -methyl-noradrenaline and fixed in permanganate, small vesicles with electron-dense central cores show up, similar to those which have been described in vertebrate adrenergic nerve fibres (small granular vesicles). They are confined to one of the two types of fibres (a and b) visible in these preparations, namely to type b, whose correspondence with type 2 fibres of formaldehyde-glutaraldehyde-osmium fixed preparations is discussed.The authors wish to thank Mr. E. Chessa and Mr. F. Piccirilli for technical assistance in photography. 相似文献
15.
The metabolism of glucose 1-phosphate and glucose 6-phosphate and their influence on the metabolism of glucose in rat-diaphragm muscle 总被引:6,自引:4,他引:2
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
16.
Glucose transport in lysosomal membrane vesicles. Kinetic demonstration of a carrier for neutral hexoses 总被引:3,自引:0,他引:3
Lysosomal membrane vesicles isolated from rat liver were exploited to analyze the mechanism of glucose transport across the lysosomal membrane. Uptake kinetics of [14C]D-glucose showed a concentration-dependent saturable process, typical of carrier-mediated facilitated transport, with a Kt of about 75 mM. Uptake was unaffected by Na+ and K+ ions, membrane potentials, and proton gradients but showed an acidic pH optimum. Lowering the pH from 7.4 to 5.5 had no effect on the affinity of the carrier for the substrate but increased the maximum rate of transport about 3-fold. As inferred from the linearity of Scatchard plots, a single transport mechanism could account for the uptake of glucose under all conditions tested. As indicated by the transstimulation properties of the carrier, other neutral monohexoses, including D-galactose, D-mannose, D- and L-fucose were transported by this carrier. The transport rates and affinities of these sugars, measured by the use of their radiolabeled counterparts, were in the same range as those for D-glucose. Pentoses, sialic acid, and other acidic monosaccharides including their lactones, aminosugars, N-acetyl-hexosamines, and most L-stereoisomers, particularly those not present in mammalian tissues, were not transported by this carrier. Glucose uptake and transstimulation were inhibited by cytochalasin B and phloretin. The biochemical properties of this transporter differentiate it from other well-characterized lysosomal sugar carriers, including those for sialic acid and N-acetylhexosamines. The acidic pH optimum of this glucose transporter is a unique feature not shared with any other known glucose carrier and is consistent with its lysosomal origin. 相似文献
17.
Sabine Kölle Fred Sinowatz Gudrun Boie Ines Totzauer Werner Amselgruber Johnna Plendl 《The Histochemical journal》1996,28(6):441-447
Summary The mRNA of the zona pellucida glycoprotein ZP3 was localized in frozen sections of pig ovaries, isolated oocytes and early embryos byin situ hybridization using biotinylated oligonucleotide probes. In follicles, the distribution of mRNA for ZP3 was correlated with the developmental stage: in primordial and primary follicles, the mRNA was shown to be predominantly localized in the oocyte. In secondary follicles, mRNA was found in both the oocyte and follicle cells. In tertiary and preovulatory follicles, the follicle cells showed distinct staining, whereas the oocyte was labelled weakly. In the early embryo, i.e. 2 days after fertilization, mRNA for ZP3 could not be demonstrated. Our results suggest that, in the pig, the zona pellucida protein ZP3 is synthesized by the oocyte and the follicle cells in sequence. After fertilization, synthesis of ZP3 is terminated. 相似文献
18.
Vaccine-induced neutralizing antibodies directed in part to the simian immunodeficiency virus (SIV) V2 domain were unable to protect rhesus monkeys from SIV experimental challenge. 总被引:6,自引:6,他引:0
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K Schlienger D C Montefiori M Mancini Y Rivire P Tiollais M L Michel 《Journal of virology》1994,68(10):6578-6588
The potential of the simian immunodeficiency virus (SIV) variable 2 (V2) domain as an effective region to boost SIV-neutralizing antibodies and to protect against live SIV challenge was tested in rhesus macaques. In this study, two rhesus macaques were primed with vaccinia virus recombinants expressing the surface glycoprotein gp140 of SIVmac and were given booster injections with the SIVmac V2 domain presented by a highly immunogenic carrier, the hepatitis B surface antigen (HBsAg). The two vaccinated macaques exhibited SIV-neutralizing antibodies after primer injections that were enhanced by the V2/HBsAg injections. Part of these SIV-neutralizing antibodies were directed specifically to the V2 region, as shown by neutralization-blocking experiments. However, despite having consistent SIV-neutralizing antibody titers, animals were not protected against homologous challenge with BK28, the molecular clone of SIVmac251. No SIV envelope-specific cellular cytotoxic response was detected throughout the immunization protocol, suggesting that neutralizing antibodies directed to SIV envelope gp140 and especially to the V2 domain were unable on their own to protect against SIV challenge. Furthermore, the vaccinees seemed to have higher viral loads than control animals after challenge, raising the question of whether neutralizing antibodies induced by vaccination and directed to the SIV envelope selected viral escape mutants, as shown previously in SIV-infected macaques. This mechanism is certainly worthy of intensive investigation and raises some concern for SIV envelope-targeted immunization. 相似文献
19.
Surface distribution and partition during freeze-fracture of CD8 antigens on human lymphocytes and on epithelial transfected cells 总被引:1,自引:0,他引:1
P. Mancini M. R. Torrisi L. V. Lotti M. C. Pascale S. Bonatti 《Histochemistry and cell biology》1994,102(1):51-57
Freeze-fracture immunocytochemistry was used to analyse the surface distribution, redistribution induced by antibodies, and partition during freeze-fracture, of CD8 molecules on human T lymphocytes and rat epithelial transfected (FRT-U10) cells. Immunogold labelling of CD8 antigens was uniform over the unfractured cell surfaces of both lymphocytes and epithelial transfected cells. After freeze-fracture, the gold particles were associated with the exoplasmic outer leaflets of the plasma membranes in both cell types. In lymphocytes, incubation with antibodies at 37° C up to 20 min induced patching and capping of the antigens on the unfractured cell surface. After fracture, the patched molecules appeared associated with the protoplasmic inner leaflet of the plasma membranes. Parallel antibody-treatment at 37° C of FRT-U10 cells induced clustering of CD8 molecules but failed to cause further aggregation in larger patches or in caps. After freeze-fracture, the immunola-belling was clustered, but associated with the exoplasmic outer leaflet of the plasma membranes as in untreated cells. The different redistribution induced by antibodies and the different behaviour on fracture of the redistributed molecules in the two cell types may be regulated by CD8 interaction with the cytoskeleton. 相似文献
20.
Anna Rita Migliaccio Giovanni Migliaccio Giancarlo Mancini Mariusz Ratajczak Alan M. Gewirtz John W. Adamson 《Journal of cellular physiology》1993,157(1):158-163
The murine white (W) spotting locus is the site of the c-kit gene and encodes a tyrosine kinase receptor while the complementary Steel (Sl) iocus encodes its ligand. Mutations at either locus have profound effects on hematopoiesis, particularly erythroid and mast cell proliferation. We added c-kit antisense oligonucleotides to long-term suspension cultures of enriched human umbilical cord progenitor cells. This resulted in the suppression of c-kit gene expression and the preferential suppression of the generation of erythroid burst-forming cells (BFU-E) which extended over the life of the culture (3 weeks). The results provide an in vitro model of the “W phenotype” in human hematopoiesis and confirm the importance of c-kit gene function in early erythropoiesis. Because the generation of BFU-E was suppressed even after c-kit gene expression had recovered, this gene product may be critical to the erythroid commitment process. © 1993 Wiley-Liss, Inc. 相似文献