全文获取类型
收费全文 | 1839篇 |
免费 | 82篇 |
国内免费 | 35篇 |
出版年
2023年 | 26篇 |
2022年 | 30篇 |
2021年 | 43篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 39篇 |
2017年 | 28篇 |
2016年 | 28篇 |
2015年 | 38篇 |
2014年 | 93篇 |
2013年 | 82篇 |
2012年 | 45篇 |
2011年 | 58篇 |
2010年 | 77篇 |
2009年 | 96篇 |
2008年 | 71篇 |
2007年 | 101篇 |
2006年 | 77篇 |
2005年 | 70篇 |
2004年 | 60篇 |
2003年 | 55篇 |
2002年 | 58篇 |
2001年 | 48篇 |
2000年 | 42篇 |
1999年 | 25篇 |
1998年 | 33篇 |
1997年 | 35篇 |
1996年 | 10篇 |
1995年 | 32篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 29篇 |
1991年 | 30篇 |
1990年 | 20篇 |
1989年 | 25篇 |
1988年 | 31篇 |
1987年 | 20篇 |
1986年 | 9篇 |
1985年 | 19篇 |
1984年 | 45篇 |
1983年 | 52篇 |
1982年 | 41篇 |
1981年 | 41篇 |
1980年 | 29篇 |
1979年 | 28篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有1956条查询结果,搜索用时 265 毫秒
31.
Adam Bertl 《The Journal of membrane biology》1989,109(1):9-19
Summary The membrane of mechanically prepared vesicles ofChara corallina has been investigated by patch-clamp techniques. This membrane consists of tonoplast as demonstrated by the measurement of ATP-driven currents directed into the vesicles as well as by the ATP-dependent accumulation of neutral red. Addition of 1mm ATP to the bath medium induced a membrane current of about 3.2 mA·m–2 creating a voltage across the tonoplast of about –7 mV (cytoplasmic side negative). On excised tonoplast patches, currents through single K+-selective channels have been investigated under various ionic conditions. The open-channel currents saturate at large voltage displacements from the equilibrium voltage for K+ with limiting currents of about +15 and –30 pA, respectively, as measured in symmetric 250mm KCl solutions. The channel is virtually impermeable to Na+ and Cl–. However, addition of Na+ decreases the K+ currents. TheI–V relationships of the open channel as measured at various K+ concentrations with or without Na+ added are described by a 6-state model, the 12 parameters of which are determined to fit the experimental data. 相似文献
32.
Summary In tip-growingChara rhizoids, the in-vivo saltatory movements of Golgi vesicles were recorded. The movements in radial direction back and forth between the ER aggregate and the plasma membrane occurred three times more often than movements passing the ER aggregate tangentially. The mean velocity of the class of Golgi vesicles observed (0.4–1 m in diameter) was approx. 0.3 m/s. Higher speed of 1–1.5 m/s occurred only in radial directions. Possibly, the ER aggregate is involved in guidance of the Golgi vesicles.Abbreviations DIC
differential interference contrast
- ER
endoplasmic reticulum
- OsFeCN
osmium tetroxide-potassium ferricyanide
Dedicated to the memory of Professor O. Kiermayer 相似文献
33.
Recent years have seen the convergence of both genetic and biochemical approaches in the study of protein translocation inE. coli. The powerful combination of these approaches is exemplified in the use of anin vitro protein synthesis-protein translocaltion system to analyze the role of genetically defined components of the protein translocation machinery. We describe in this review recent results focusing on the function of thesecA, secB, andsecY gene products and the demonstration of their requirement forin vitro protein translocation. The SecA protein was recently shown to possess ATPase activity and was proposed to be a component of the translocation ATPase. We present a speculative working model whereby the translocator complex is composed of the integral membrane proteins SecY, SecD, SecE, and SecF, forming an aqueous channel in the cytoplasmic membrane, and the tightly associated peripheral membrane protein SecA functioning as the catalytic subunit of the translocator or protein-ATPase. 相似文献
34.
Callus was induced from juice vesicles of satsuma mandarin on Murashige & Skoog medium supplemented with -naphthaleneacetic acid (NAA), kinetin (K) and gibberellin (GA). Adventitious embryoids arose from the callus tissue on the medium containing 1 mgl–1 NAA alone. The embryoids grew into embryos which resulted in a plantlet on medium containing 1 mgl–1 GA.Abbreviations GA
gibberellin
- K
kinetin
- NAA
-naphthaleneacetic acid 相似文献
35.
Summary A polyclonal antibody against -1,3-glucan, callose, extracted from the pollen tube wall ofCamellia japonica was raised in mice and, using it as a probe, the localization of callose in the germinated pollen was studied. By confocal laser scanning microscopy, callose was found in the tip region of the pollen tube and the tube wall; the immuno-fluorescence in the tube wall was less toward the base of the tube. In contrast, the tip region did not fluoresce although the whole of the tube wall did strongly with aniline blue, the specific dye for callose. Immuno-electron microscopy showed that callose was also found in Golgi vesicles which concentrated in the tip region of the pollen tube, the inner layer of the tube wall, callose plugs, and Golgi vesicles in the pollen grain. Immuno-gold labeling was often detected on the fibrous structures in Golgi vesicles and callose plugs. Based on these results, the participation of Golgi vesicles in the formation of the tube wall and callose plugs was discussed.Abbreviation TBS
Tris-buffered saline
- Tris
Tris(hydroxy-methyl)-aminomethane
- PBS
phosphate-buffered saline
- BSA
bovine serum albumin
- ELISA
enzyme-linked immunosorbent assay
- CLSM
confocal laser scanning microscopy
- DP
degree of polymerization 相似文献
36.
Concanamycin 4-B, a macrolide antibiotic with an 18-membered lactone ring, is known as a specific inhibitor of the vacuolar type of H+-ATPase, as is bafilomycin A1. The drug was tested for its effect on regulation of the vacuolar pH (pHv) of internodal cells of a fresh water characean alga, Chara corallina, under normal conditions and under salt stress. The pHv was measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH-sensitive glass microelectrode into the vacuole. Proton-pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4-B at 1 nM. Concanamycin 4-B at 1 μM significantly increased pHv while bafilomycin A1 was ineffective when applied at 1 μM. Concanamycin 4-B did not affect pHv when applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization. Concanamycin 4-B also inhibited pHv regulation under NaCl stress. When Chara cells were treated with 100 mM NaCl, pHv promptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4-B (1 μM), suggesting that the reacidification was achieved by the H+-ATPase of the tonoplast. 相似文献
37.
Abstract A dense population of the purple sulfur bacterium Amoebobacter purpureus in the chemocline of meromictic Mahoney Lake (British Columbia, Canada) underwent consistent changes in biomass over a two year study period. The integrated amount of bacteriochlorophyll reached maxima in August and declined markedly during early fall. Bacteriochlorophyll was only weakly correlated with the light intensity and water temperature in the chemocline. In the summer, bacterial photosynthesis was limited by sulfide availability. During this period the intracellular sulfur concentration of A. purpureus cells decreased. A minimum concentration was measured at the top of the bacterial layer in August, when specific photosynthetic rates of A. purpureus indicated that only 14% of the cells were photosynthetically active. With the exception of a time period between August and September, the specific growth rates calculated from CO2 fixation rates of A. purpureus were similar to growth rates calculated from actual biomass changes in the bacterial layer. Between August and September 86% of the A. purpureus biomass disappeared from the chemocline and were deposited on the littoral sediment of Mahoney Lake or degraded within the mixolimnion. This rise of cells to the lake surface was not mediated by an increase in the specific gas vesicle content which remained constant between April and November. The upwelling phenomenon was related to the low sulfur content of A. purpureus cells and a low resistance of surface water layers against vertical mixing by wind. 相似文献
38.
Jeremy E. Schonhorn Marianne Wessling-Resnick 《Molecular and cellular biochemistry》1994,135(2):159-169
The fungal metabolite brefeldin A (BFA) induces profound alterations in the morphology of intracellular organelles. Although BFA promotes the formation of extensive tubular endosomal domains, our understanding of the effects of the antibiotic on vesicle traffic events associated with endocytosis is limited. Thus, alterations in the transferrin (Tf) receptor's endocytic/recycling pathway upon treatment of human erythroleukemia K562 cells with BFA were studied as a pharmacological response. Treatment of K562 cells with BFA caused a down-regulation in the number of cell surface Tf receptors. This effect is highly reminiscent of the well-known action of phorbol 12-myristate 13-acetate (PMA) on Tf receptor traffic in K562 cells. However, our results demonstrate that these two agents down-regulate the Tf receptor via different mechanisms. The effects of BFA and PMA were additive when K562 cells were incubated with both together. Using the In/Sur method, the endocytic rate constant for Tf internalization was determined and PMA was found to greatly enhance ke, from 0.28 min–1 to 0.43 min–1, while BFA had little effect (Ke=0.20 min–1). In contrast, BFA-treatment alters the exocytic rate constant for return of internalized receptors to the cell surface, with the largest effect exerted on a slow-release, monensin-sensitive, compartment. The sum of the endocytic and exocytic kinetic data support a model in which BFA and PMA down-regulate the Tf receptor in K562 cells by mechanistically distinct actions, with BFA targeting exocytic monensin-sensitive intracellular compartments and PMA acting to exert a profound influence on elements of receptor internalization.Abbreviations BFA
brefeldin A
- ARF
ADP-ribosylation factor
- HRP
horseradish peroxidase
- Tf
transferrin
- PMA
phorbol 12-myristate 13-acetate
- DMSO
dimethyl sulfoxide
- PBS
phosphate-buffered saline
- HEPES
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- BSA
bovine serum albumin
- FITC-Tf
fluorescein isothiocyanate-labelled transferrin 相似文献
39.
We produced three monoclonal antibodies, SG1, SG2 and SG3, specific for human seminal -glutamyltransferase when characterized by enzyme-linked immunosorbent assay and immunoblotting. Seminal -glutamyltransferase was localized, by immunostaining, to the epithelial cells of the ductus epididymidis, seminal vesicle and prostate gland with SG1, those of the prostate gland with SG2, and those of the seminal vesicle with SG3. Rabbit polyclonal anti-seminal -glutamyltransferase serum reacted with the proximal convolution of the kidney and the bile capillaries of the liver, and with the epithelial cells of the reproductive organs. However, immunoreactivity was not observed in the kidney or liver with the monoclonal antibodies. Thus, these monoclonal antibodies are probably all specific to seminal -glutamyltransferase but recognize different epitopes. 相似文献
40.
Annexin-mediated secretory vesicle aggregation in plants 总被引:4,自引:0,他引:4
The mechanism by which membranes fuse during vesicle-mediated secretion is of considerable importance for plant cell growth, but remains unknown. We have identified Ca2+ -dependent phospholipid-binding proteins (annexins) from maize ( Zea mays ), that may play a part in this process. An assay for Ca2+ -dependent binding of annexins to liposomes, revealed that the maize proteins (p23, p33 and p35) and annexins from bovine lung, bind over a similar range of Ca2+ concentrations. Turbidity assays further revealed that both maize and bovine annexins induced liposome aggregation and that the plant annexins were also effective at aggregating plant secretory vesicles. This aggregation occurred at levels of free Ca2+ similar to that required for the binding of annexins p33 and p35. We discuss the significance of these results for the plant secretory apparatus. 相似文献