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991.
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Changes in cytosolic Ca2+ concentration ([Ca2+]i) following muscarinic receptor stimulation were studied with digital imaging microscopy in small clusters of Fura-2 loaded rat parotid acinar cells. In the absence of extracellular Ca2+, the increase in [Ca2+]i evoked by a high concentration (10 IM) of carbachol (CCh) was initiated in the apical pole of the acinar cells about 0.4 s after stimulation and then rapidly spread as a Ca2+ wave toward the basolateral region. The [Ca2+]i reached the maximum high level throughout the cells 1–2 s after stimulation. As Ca2+ was eliminated from the extracellular medium, the Ca2+ wave was a result of Ca2+ release from intracellular stores. The magnitude and velocity of the Ca2+ wave decreased with decreasing concentration of CCh, and the increase in [Ca2+]i induced by low CCh concentrations (≤ 0.5 μM) was always larger in the apical region of acinar cells than in the basal region. The Ca2+ wave was also observed in isolated single acinar cells, indicating that the maintenance of acinar structure is not essential for the development of the Ca2+ wave. Thapsigargin (ThG), an inhibitor of the endoplasmic reticulum Ca2+ pump, caused a slow and homogeneous increase in [Ca2+]i throughout the cells. Addition of ThG after CCh, or addition of CCh after ThG, did not stimulate further increases in [Ca2+]i suggesting that the inositol-1,4,5-trisphosphate (InsP3) and ThG-sensitive Ca2+ stores overlap in parotid acinar cells. The present study supports the hypothesis that formation of InsP3 is essential to trigger the Ca2+ wave and that the development of the Ca2+ wave may be attributed to regional differences in InsP3 sensitivity of Ca2+ stores. The agonist-induced Ca2+ wave is probably a general phenomenon in exocrine acinar cells. 相似文献
995.
A sustained increase of cytosolic Ca in γδ T cells triggered by co-stimulation via TCR/CD3 and LFA-1
N. Kobayashi K. Hiromatsu G. Matsuzaki M. Harada Y. Matsumoto K. Nomoto Y. Yoshikai 《Cell calcium》1997,22(6):421-430
We previously reported that co-stimulation with LFA-1 triggered apoptosis in γδ T cells but not in αβ T cells after TCR engagement. We extended our earlier study on TCR/LFA-1 triggered apoptosis to two autoreactive TCR γδ and TCR αβ T cell clones, which were derived from syngeneic mixed lymphocyte culture of BALB/c mice. A γδ T cell clone, KM1, expressed the Vγ4 and Vδ5 genes and CD4-CD8-CD45RB+ phenotype; and an αβ T cell clone, BASL1.1, expressed Vβ6 and CD4+CD8-CD45RB+. Both clones produced Th-1-type cytokines in response to syngeneic BALB/c stimulator cells. KM1 underwent apoptosis upon stimulation with immobilized anti-CD3/LFA-1 mAbs, whereas BASL1.1 could proliferate successfully in response to stimulation with the immobilized mAbs. BASL1.1 was able to down-regulate the increased cytosolic Ca2+ after the simultaneous stimulation, but KM1 exhibited a sustained increase of cytosolic Ca2+ after stimulation via CD3 and LFA-1. Similar results with respect to the kinetics of cytosolic Ca2+ were obtained with normal heterogeneous γδ and αβ T cell populations after co-stimulation via CD3 and LFA-1. Our results suggested that persistently high levels of cytosolic Ca2+ might be related to apoptosis in γδ T cell clone triggered by costimulation via CD3 and LFA-1. 相似文献
996.
Matsumoto M 《Biophysical chemistry》1996,58(1-2):173-183
The time-dependent rotational diffusion equation for rigid macromolecules in solution has been approximately solved for two cases in order to extend the electric birefringence technique to streaming-electric birefringence. One is for the initial period through the application of a rectangular electric pulse to the solution immersed in a low shear flow. The purpose of this is expansion of the distribution function into a function series made by the product of the powers of reduced time (= Thetat) and hydrodynamic field alpha (= G Theta , G: velocity gradient, Theta: rotary diffusion constant) and a surface harmonic P(i)(j)cos jphi. The solution for the build-up process at arbitrary electric field strength is found, but is limited to low hydrodynamic fields. The other is for the response when an alternating electric field is applied to the solution in a shear flow. Here, instead of reduced time, the maximum electric field E(0) is chosen as a parameter for the expansion. The expressions for the intensity of the transmitted light through crossed Nicols are derived in two optical systems where the polarizer is set at an angle of 45 degrees and 0 degrees to the direction of the electric field. The results in the former case show that we can determine four parameters, the ratio of velocity gradient to rotary diffusion constant, the axial ratio of a particle, the anisotropy of electric polarizability, and the optical anisotropy factor, from four values observed in two optical systems, namely, two light intensities before applying an electric field and two initial slopes of the build-up after applying an electric field. On the other hand, when a low alternating electric field with extremely high frequency is applied, the build-up of the light intensity in the former case is the same as that of electric birefringence for pure induced dipole orientation. The build-up for the latter optical system is the same as the expression for pure induced dipole orientation of Eq. (38) shown in a previous work. 相似文献
997.
H. Aizawa H. Inoue K. Matsumoto H. Koto H. Nakano N. Hara 《Prostaglandins, leukotrienes, and essential fatty acids》1996,55(6):437-440
Although the bronchoconstriction induced by leukotriene D4 (LTD4) has been reported to be partly mediated by thromboxane A2 (TXA2) in the guinea-pig airway, it is not known which part of the airway is susceptible to TXA2. In order to determine the role of TXA2 in the central and peripheral airways, we compared the effect of a TXA2 antagonist on tracheal strips to its effect on parenchymal strips of guinea-pigs. Tracheal and parenchymal strips were mounted in a 3.5 ml organ bath filled with Krebs-Henseleit solution aerated with 95% O2, 5% CO2 and kept at 37°C. After equilibration for 60 min in Krebs solution, the strip was contracted by exposure to 10−5 M of acetylcholine (ACh). Sixty minutes after ACh was eliminated, the concentration-response curve to LTD4 (10−9 M–10−7 M) was obtained, and the LTD4-induced contractions were expressed as the percent of the contraction evoked by 10−5 M of ACh. We measured the contractile response to LTD4 in the presence or absence of the TXA2 antagonist, BAY u3405 (10−8 M–10−6 M). In the tracheal strips, BAY u3405 had no effect on the LTD4-induced contraction. However, in parenchymal strips, BAY u3405 significantly suppressed the contractile response to LTD4. These results suggest that in the central airway LTD4 contracts smooth muscle directly, but that in the peripheral airway LTD4 induces smooth muscle contraction both directly and indirectly, via TXA2. 相似文献
998.
Using the ant-derived probe (pMY7), we performed DNA fingerprinting in monogynous and polygynous sibling ant speciesCamponotus nawai andCamponotus yamaokai. In monogynousC. nawai, band-sharing probabilities were low between unrelated individuals (mean 0.09), but those and relatedness estimates were
consistently high between workers of the same nest (mean 0.85 and 0.74–0.83, respectively), suggesting that the queen mated
once and nestmate workers are super-sisters. It also suggested monoandry: that is, that all nestmate workers shared most of
the bands which were considered to have derived from a male. In polygynousC. yamaokai, band-sharing probabilities were low between queens of different populations (mean 0.13), moderate between queens of different
nests in the same population (mean 0.25), but very high between queens of the same nest (within-nest means were 0.84–0.96).
These results suggest that nestmate queens are genetically closely related with each other. Relatedness estimates between
colony members sometimes reached 1. This might result from successive intranidal mating (inbreeding or large Wahlund effect)
and adoption of new queens into the natal nests. 相似文献
999.
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