全文获取类型
收费全文 | 1836篇 |
免费 | 152篇 |
专业分类
1988篇 |
出版年
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 26篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 23篇 |
2017年 | 21篇 |
2016年 | 44篇 |
2015年 | 73篇 |
2014年 | 90篇 |
2013年 | 98篇 |
2012年 | 158篇 |
2011年 | 147篇 |
2010年 | 88篇 |
2009年 | 96篇 |
2008年 | 116篇 |
2007年 | 131篇 |
2006年 | 110篇 |
2005年 | 117篇 |
2004年 | 92篇 |
2003年 | 100篇 |
2002年 | 94篇 |
2001年 | 28篇 |
2000年 | 10篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 24篇 |
1996年 | 25篇 |
1995年 | 28篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 25篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1979年 | 6篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1966年 | 1篇 |
1964年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有1988条查询结果,搜索用时 15 毫秒
1.
2.
Selective distinction at equilibrium between the two alpha-neurotoxin binding sites of Torpedo acetylcholine receptor by microtitration 总被引:1,自引:0,他引:1
The binding of the monoiodinated alpha-neurotoxin I from Naja mossambica mossambica to the membrane-bound acetylcholine receptor from Torpedo marmorata was investigated using a new picomolar-sensitive microtitration assay. From equilibrium binding studies a non-linear Scatchard plot demonstrated two populations of binding sites characterized by the two dissociation constants Kd1 = 7 +/- 4 pM and Kd2 = 51 +/- 16 pM and having equal binding capacities. These two populations differed in their rate of dissociation (k-1.1 = 25 x 10(-6) s-1 and k-1.2 = 623 x 10(-6) s-1 respectively), but not in their rate of formation of the toxin-receptor complex (k + 1 = 11.7 x 10(6) M-1 s-1). From these rate constants the same two values of dissociation constant were deduced (Kd1 = 2 pM and Kd2 = 53 pM). All the specific binding was prevented by the cholinergic antagonists alpha-bungarotoxin and d-tubocurarine. In addition, a biphasic competition phenomenon allowed us to differentiate between two d-tubocurarine sites (Kda = 103 nM and Kdb = 13.7 microM respectively). Evidence is provided indicating that these two sites are shared by d-tubocurarine and alpha-neurotoxin I, with inverse affinities. Fairly conclusive agreement between our equilibrium, kinetic and competition data demonstrates that the two high-affinity binding sites for this short alpha-neurotoxin are selectively distinguishable. 相似文献
3.
4.
5.
Pascale Andre Christian Capo Anne Marie Benoliel Michel Buferne Pierre Bongrand 《Cell biochemistry and biophysics》1990,16(1-2):13-34
Fluorescent probes are widely used to study cell structure and function. However, few reports were devoted to a quantitative analysis of the intracellular distribution of fluorescent markers. In the present work, we describe the topographical changes of surface and cytoskeletal markers on individual cells subjected to adhesive or mechanical interaction. Conjugates were prepared with a cytotoxic T-lymphocyte clone and target cells. Specific antigens, membrane phospholipids, surface glycoconjugates, and polymerized actin were labeled with fluorescent antibodies or biochemical probes. The analysis of fluorescence distributions in conjugates demonstrated a selective reorganization of the plasma membrane with a gathering of some molecular species in the intercellular adhesion area. Furthermore, individual phagocytic cells were sucked into glass micropipets, then stained with fluorescent phallacidin to analyze the effect of mechanical efforts on the cytoskeleton organization. The concentration of polymerized actin was found to be similar in mechanicallyinduced protrusions and whole cells. It is concluded that adhesive interactions may result in marked cell polarization and formation of membrane zones with a particular biochemical composition. The submembranar cytoskeleton might play a role in this process. 相似文献
6.
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
7.
8.
Citrate metabolism was studied in non-growing cells of Leuconostoc mesenteroides subsp. mesenteroides and subsp. dextranicum with respect to energetics, formation of degradation products and stoichiometry. The use of selective ionophores and uncoupler showed that citrate utilization was coupled to the proton motive force generated by ATP hydrolysis. Differences in citrate metabolism observed in 20 Leuconostoc strains were related to strains but not to the species or subspecies studied. Citrate metabolism was stimulated by glucose up to a concentration of 25 mmol 1-1 and decreased at higher concentrations. The main degradation products resulting from the co-metabolism of citrate (10 mmol 1-1 ) and glucose (2 mmol 1-1 ) were acetate, lactate and pyruvate. Only four Leuconostoc strains produced low levels of acetoin and diacetyl. No strains produced ethanol or acetaldehyde. Citrate degradation ability was stable for at least 130 generations in 81% of the Leuconostoc strains. 相似文献
9.
Cucumber mosaic virus genome is encapsidated in alfalfa mosaic virus coat protein expressed in transgenic tobacco plants 总被引:1,自引:0,他引:1
The expression of viral coat protein (CP) in transgenic plants has been shown to be very effective in virus plant protection. However, the introduction of CP genes into plants presents the potential risk of the encapsidation of a superinfecting viral genome in the transgenic protein, an event which could change the epidemiology of the disease. To detect the potential heterologous encapsidation of the cucumber mosaic virus (CMV) genome by alfalfa mosaic virus (AIMV) CP expressed in transgenic tobacco plants, a system of immunocapture (IC) and amplification by polymerase chain reaction (PCR) was optimized. This provided high sensitivity and reliable selection of the heterologously encapsidated CMV genome in the presence of natural CMV particles. As little as 2 pg of virus could be detected by immunocapture/polymerase chain reaction (IC/PCR) technique. Evidence for heterologous encapsidation of the CMV genome was found in 11 of the 33 transgenic plants tested two weeks after CMV inoculation. This demonstrates a significant rate of heterologous encapsidation events between two unrelated viruses in transgenic plants. Since CP is involved in the interactions of the virus particle with its vector, the release in the field of such transgenic plants could alter the transmission properties of some important viruses. 相似文献
10.
Induction of phagocytic behaviour in human epithelial cells by Escherichia coli cytotoxic necrotizing factor type1 总被引:7,自引:0,他引:7
Loredana Falzano Carla Fiorentini Gianfranco Donelli Eric Michel Christine Kocks Pascale Cossart Lucien Cabanié Eric Oswald Patrice Boquet 《Molecular microbiology》1993,9(6):1247-1254
Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound reorganization of the actin cytoskeleton into prominent stress fibres and membrane ruffles. We report here that this process is associated with induction of phagocytic-like activity. CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system. Uptake of bacteria was similar to pathogen-induced phagocytosis, since L. innocua transformed with DNA coding for the pore-forming toxin listeriolysln O behaved, with respect to intracellular growth, like the invasive, pathogenic species L. monocytogenes. Our results raise the possibility that, in vivo, pathogenic CNF1 -producing E. coli may invade epithelia by this novel induced phagocytic-like mechanism. 相似文献