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1.
2.
Roberta Colombo Raffaella Cerana Piera Lado Antonio Peres 《The Journal of membrane biology》1988,103(3):227-236
Summary The patch-clamp technique in whole-cell configuration was used to study the electrical properties of the tonoplast in isolated vacuoles fromAcer pseudoplatanus cultured cells. In symmetrical KCl or K2 malate solutions, voltage- and time-dependent inward currents were elicited by hyperpolarizing the tonoplast (inside negative), while in the positive range of potential the conductance was very small. The specific conductance of the tonoplast at –100 mV, in 100mm symmetrical KCl was about 160 S/cm2. The reversal potentials (E
rev) of the current, measured in symmetrical or asymmetrical ion concentrations (cation, anion or both) were very close to the values of the K+ equilibrium potential. Experiments performed in symmetrical or asymmetrical NaCl indicate that Na+ too can flow through the channels. NeitherE
rev nor amplitude and kinetics of the current changed by replacing NaCl with KCl in the external solution. These results indicate the presence of hyperpolarization-activated channels in tonoplasts, which are permeable to K+ as well as to Na+. Anions such as Cl– or malate seem to contribute little to the channel current. 相似文献
3.
A Peres F P Nestel T A Seemayer W S Lapp 《Journal of immunology (Baltimore, Md. : 1950)》1986,137(11):3420-3427
We previously demonstrated that treatment of (C57BL/6 X A)F1 (F1) recipient mice with polyinosinic:polycytidylic acid (pI:C) before injection with 30 X 10(6) C57BL/6 (B6) lymphocytes prevents both the immunosuppression and pathologic lesions typical of graft-vs-host (GVH) reactions. We now report the further characterization of this phenomenon. Donor spleen and lymph node cells were labeled with fluorescein in vitro and injected into pI:C-treated or untreated mice. Two days later, recipient splenocytes were analyzed for the presence of fluorescein-labeled donor cells by flow microfluorometry. Treatment of F1 mice with pI:C resulted in a sharp reduction in the recovery of labeled B6 but not A strain parental cells. Treatment with pI:C had no effect when syngeneic recipients were used, or when F1 cells were injected into A, B6, or F1 recipients. These results suggest that pI:C treatment induces rejection of B6 but not A or F1 lymphocytes by F1 hybrid mice at least as early as 2 days after donor cell transfer. As F1 cells are not rejected by either parent, rejection does not seem to be directed against classical alloantigens. These observations are compatible with the previously described model of hybrid resistance (HR) against bone marrow grafts. The rapidity of rejection strongly suggested that natural cytotoxic mechanisms were involved, thus, natural killer (NK) cell and macrophage (M phi) cytotoxic activities were tested throughout the time when the parental cell graft was being rejected. Over this period, pI:C treatment increased cytotoxic activity against the NK-sensitive target cell line YAC-1 but had no effect on spontaneous M phi tumoricidal activity against the L5178Y and MDAY-D2 cell lines. The results suggest that NK cells, but not M phi, may be involved in the elimination of B6 parental cells by the pI:C-treated F1 mice. NK cells have been demonstrated to be radioresistant; thus, as a test of our hypothesis, we examined the effects of irradiation on the capacity of pI:C treated F1 mice to reject B6 lymphocytes. The results show that this capacity was not blocked by 750 cGy, a dose of radiation that abrogates most T and B cell functions. Furthermore, rejection of parental cells could be prevented by treatment of recipient F1 mice with antibodies to asialo GM1, a treatment that suppresses NK activity. These data demonstrate that pI:C-mediated protection from GVH-induced changes is due to increased rejection of grafted B6 parental cells by F1 NK cells, a phenomenon very similar, if not identical, to HR to bone marrow grafts. 相似文献
4.
Demonstration of a beta-casomorphin immunoreactive material in the plasma of newborn calves after milk intake 总被引:1,自引:0,他引:1
Martin Umbach Hansjörg Teschemacher Karina Praetorius Richard Hirschhäuser Hartwig Bostedt 《Regulatory peptides》1985,12(3):223-230
Blood was collected from newborn calves before and after their first milk intake after birth; extracts of plasma were assayed by radioimmunoassay for the presence of beta-casomorphin-7 immunoreactive materials. No beta-casomorphin immunoreactivity was found in samples collected before milk ingestion; however, in samples collected after milk ingestion a beta-casomorphin-7 immunoreactive material was detected. Chromatographic characterization showed that this material was not identical with beta-casomorphin-7 but might rather represent a precursor thereof. The material proved resistant to enzymatic attack during a 30-min incubation period at 37 degrees C in the plasma of newborn calves, whereas beta-casomorphin-7 was degraded under these conditions. A physiological significance of beta-casomorphin-7 eventually cleaved from such a precursor material at any site in the newborn mammal is suggested. 相似文献
5.
Analysis of lumped and distributed elements models of cut muscle fibers in vaseline or sucrose gap preparations
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A general method of finding the time course and the steady state distribution of potential in Vaseline or sucrose gap preparations is given by making use of the linear cable equation. The general solution has been found analytically in terms of its Laplace transform and then numerically inverted. Two particular experimental situations, namely the single gap and the double gap preparations, have been analyzed. The results have been compared with the solutions of the commonly used lumped elements models. While for the double gap no large errors are introduced by the lumped model, for the single gap there are significant differences. The dependence of the voltage distribution on various electrical and geometrical parameters has been examined. It is suggested that the proposed mathematical treatment might be used by experimenters as a reference to assess the validity of simplified lumped models. 相似文献
6.
Cytosolic calcium and membrane conductance in response to platelet-derived growth factor and bradykinin stimulation in single human fibroblasts 总被引:1,自引:0,他引:1
Bradykinin (BK) and platelet-derived growth factor (PDGF) act as mitogens and stimulate phosphatidylinositol (PI) turnover in human fibroblasts. By coupling whole-cell electrophysiological measurements with cytosolic Ca2+ determinations using fura-2 microfluorimetry, we have studied the changes in cytosolic calcium and in membrane conductance in single cells following stimulation with BK or PDGF. Both agonists produce variable patterns of response which include: single transient, sustained pulsations, damped oscillations, no response. In all cases, there is a very good temporal correlation between increases in intracellular Ca2+ and membrane current. The cytosolic calcium elevation appears to be insensitive to membrane potential changes, indicating that Ca2+ is released from an intracellular source. The Ca2(+)-activated current is not blocked by 1 microM apamin or by 0.5 mM (+)-tubocurarine; it is instead strongly reduced by 5 mM tetraethylammonium (TEA). We can conclude that BK and PDGF induce very similar early responses in human fibroblasts, and that the variable pattern of response does not depend on the particular mitogen used. The membrane currents are due to a kind of Ca2(+)-activated K+ channels which, according to their voltage-dependence and specific blockers, belong to the "maxi K+" class. 相似文献
7.
The effect of the addition of oleuropein (OLP) and NaCl on the growth and the DL-lactic acid production of Lactobacillus plantarum DSM 10492 has been investigated by using an unconventional medium. The growth of L. plantarum was not inhibited by the addition of increasing amounts of untreated OLP in the presence or absence of glucose. However,
bacterial cells grew in quantity slightly with OLP alone. The increased addition of NaCl was associated with a delay in growth.
Moreover, there was no growth with 8% NaCl. The addition of both NaCl and OLP resulted in growth inhibition, and the survival
of cells decreased strongly. The main fermentation product was DL-lactic acid, but acetic acid was also detected after a prolonged incubation. L. plantarum produced DL-lactic acid in the presence of OLP alone but its formation decreased with increasing levels of OLP. On the other hand, heat-treated
OLP had a bactericidal effect.
Received: 16 October 1995/Received last revision: 5 February 1996/Accepted: 12 February 1996 相似文献
8.
9.
Ion balance in tomato cultivars differing in salt tolerance. I. Sodium and potassium accumulation and fluxes under moderate salinity 总被引:1,自引:0,他引:1
The magnitude of sodium and potassium fluxes in Lycopersicon escutentum cuhivars Ace and Edkawi (Edkawi is considered more sait-tolerant I was evaluated in planls grown for 10 days in aerated Hoagland solution with the addition of 25 or 100 mM NaCl. Ion accumulatiun in different plant pans, ion concentration in xylem exudate. transpiration and membrane leakiness were measured. Both cultivars responded very similarly to these levels of salinity in terms of growth. No conspicuous differences in membrane leakiness were observed. Net uprake rates were calculated from ion contents data. Potassium uptake rates were lower in salinized planls than in controls, especially in cv. Aee. Potassium/sodium selectivity ratios were much higher in Edkawi than in Ace. and higher in shoot uptake rates than in xy lem exudate. This indicates that Edakw i has a higher capacity to retain potassium under salinity, a character which could contribute to its salt-tolerance. 相似文献
10.
Karina Reiter Christoph Plutzar Dietmar Moser Philipp Semenchuk Karl-Heinz Erb Franz Essl Andreas Gattringer Helmut Haberl Fridolin Krausmann Bernd Lenzner Johannes Wessely Sarah Matej Robin Pouteau Stefan Dullinger 《Global Ecology and Biogeography》2023,32(6):855-866