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141.
Hans Oberleithner Florian Lang Rainer Greger Hans Sporer 《Pflügers Archiv : European journal of physiology》1979,379(1):37-41
In previous studies it has been demonstrated that a decline of plasma calcium concentration accounts for the decrease of phosphate reabsorption in thyroparathyroidectomized (TPTX) rats undergoing phosphate loading.Microinfusion studies were performed in TPTX rats in order to discriminate between a systemic effect of calcium an a direct renal effect.Thyroparathyroidectomized animals were infused with a phosphate solution continuously. When plasma calcium concentration fell below 1.30 mmol/l, proximal convoluted tubules were microinfused with a phosphate tracer solution for 42 min. After 18 min a calcium chloride-containing solution was applied superficially (superfused) to the area of the microinfused tubule. This elevation of peritubular calcium concentration led to an immediate increase of phosphate reabsorption up to 12% of the microinfused phosphate load within 24 min.In another series of experiments, the calcium specific ionophore A 23187 — a substance which is known to increase intracellular calcium — was superfused on the microinfused tubule. This resulted again in an increase of fractional phosphate reabsorption of about 15% after 24 min. In contrast, when calcium chloride-free as well as ionophore-free solutions were superfused fractional phosphate reabsorption decreased (7%).From these data we conclude that 1. calcium has a direct renal effect on phosphate reabsorption in the absence of parathyroid hormone and 2. intracellular calcium appears to be a major parameter in the regulation of renal phosphate transport under these conditions.This study was supported by Dr. Legerlotz StiftungParts of this study were presented at the fall meeting of the Nephrologische Gesellschaft in Bonn, 1977 and at the spring meeting of the Deutsche Physiologische Gesellschaft in Göttingen, 1978 相似文献
142.
Wilfried Bieger Jörg Seybold Horst F. Kern 《Virchows Archiv : an international journal of pathology》1975,368(4):309-327
Summary The possible role of microtubules and microfilaments in the secretory process of the rat exocrine pancreas was analysed in vitro using isolated pancreatic lobules. Colchicine and vinblastine as microtubule inhibitors, hexylene glycol as a microtubule stabilizer, and cytochalasin B as a disruptive agent for microfilaments were used in increasing concentrations to test their effects on protein synthesis, intracellular transport, zymogen discharge, and cellular respiration.Colchicine only at 10–2 M concentrations inhibits protein synthesis, while vinblastine inhibits at 10–6 and 10–5 M by 20% and at 10–4 M by 55%. A similar inhibition is observed with 1.5% concentrations of hexylene glycol while cytochalasine B at 1,5 and 10 g/ml is without effect on protein synthesis. Colchicine and vinblastine have their major effects on intracellular transport both in secretion studies and cell fractionation experiments. Colchicine in concentrations between 10–3 to 10–5 M inhibits discharge of newly synthesized proteins by 50%, while vinblastine shows a dose-response relationship of 40% inhibition at 10–6 M to 90% at 10–4 M. Discharge of amylase is uniformly reduced by 30% by both colchicine and vinblastine in the whole dose range. The pronounced effect of colchicine and vinblastine is evident in cell fractionation studies: both drugs inhibit the disappearance of protein radioactivity from microsomes and its appearance in zymogen granules; similarly the peak radioactivity in smooth microsomes (Golgi) appears delayed. No differential effect on the secretory process was observed with 1.5% concentrations of hexylene glycol or cytochalasin B at 1.5 and 10 g/ml concentrations. A fines tructural analysis of microtubules and microfilaments in the exocrine pancreatic cell reveals their distribution in all parts of the cytoplasm and in relation to all cell organelles. Both systems (microtubules, microfilaments) seem to be connected, at least in certain areas of the cytoplasm and at the plasma membrane.The reduction of transport efficiency by microtubule inhibitors results in a deposition of secretory material in the cisternal space of the rough endoplasmatic reticulum, which leads to the formation of paracrystals. Colchicine at 10–3 M concentrations leads to an enlargement of condensing vacuoles in the Golgi complex.A short communication on the same subject was presented at a Symposion on Stimulus-Secretion-Coupling in the Gastro-intestinal Tract, Titisee (May 27–29, 1975).Supported by Deutsche Forschungsgemeinschaft (Ke 113/8). 相似文献
143.
O. G. Belokurov S. B. Golumb N. I. Nikitina 《Bulletin of experimental biology and medicine》1976,81(4):474-476
By means of a method of two-way perfusion of the isolated human placenta the transport of urea from the fetal to the maternal placental circulation and the transport of amino acids in the opposite direction were studied. Experiments showed that the method provides for sufficiently complete perfusion of the intervillous space and creates suitable conditions for the study of placental transport. If the amino nitrogen concentrations in the two circulatory systems are equal, its concentration in the fetal circulation rises in the course of the experiment. On the addition of an amino acid to the maternal circulation, this increase develops to a greater degree. The results of these experiments confirm the view that amino acids are secreted by trophoblast cells into the fetal circulation.Laboratory of Biochemistry, Institute of Obstetrics and Gynecology, Academy of Medical Sciences of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR M. A. Petrov-Maslakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 4, pp. 394–397, April, 1976 相似文献
144.
H. Baker R. F. Spencer 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1986,63(3):461-473
Summary The sensory neurons of the olfactory epithelium, as a consequence of their odor detection function, contact both the external environment and the central nervous system. The possibility that substances applied to the epithelium might reach the central nervous system was investigated by the intranasal application of peroxidase-conjugated wheat germ agglutinin (WGA-HRP). WGA-HRP was transported through olfactory receptor axons to the glomerulus of the olfactory bulb. Reaction product was localized electron microscopically to tubulovesicular profiles and dense bodies in sensory axons. Evidence of transneuronal transport was indicated by reaction product localized in dense bodies in dendrites postsynaptic to receptor cell axons. Periglomerular, tufted and mitral cells in the olfactory bulb also were transneuronally labeled. Anterograde transneuronal labeling occured in the olfactory tubercle, piriform cortex and surrounding the lateral olfactory tract. Retrograde transneuronal label was found in neurons of the basal forebrain with the largest number of perikarya in the lateral nucleus of the horizontal limb of the diagonal band, a major source of cholinergic afferents to the olfactory bulb. These data suggest that substances, specifically those which bind to receptors, are transported from the olfactory receptor neurons in the nasal epithelium to the brain. Thus, the olfactory system may provide a route of entry for exogenous substances to the basal forebrain.Abbreviations AC
anterior commissure
- CC
corpus callosum
- CI
internal capsule
- CP
caudate putamen
- DBB
diagonal band of Broca
- FX
fornix
- GP
globus pallidus
- IC
island of Callelae
- LV
lateral ventricle
- MS
medial septum
- OC
optic chiasm
- PIR
piriform cortex
- RF
rhinal fissure
- SON
supraoptic nucleus
- SCN
suprachiasmatic nucleus
- SM
stria medullaris
- ST
stria terminalis
- TOL
lateral olfactory tract
- TUO
olfactory tubercle
- III
third ventricle 相似文献
145.
目的:观察同型半胱氨酸(Hcy)对心肌线粒体电子漏及自由基生成的影响,以及观察牛磺酸的拮抗效应。方法: 分离大鼠心肌线粒体,超声波破碎线粒体制备亚线粒体,纯化制备猪心肌线粒体琥珀酸细胞色素C还原酶(SCR)重组体。分别用Hcy和/或牛磺酸共同孵育心肌线粒体、亚线粒体、SCR;用化学发光法测定H2O2- 及O2- 生成;并用滤膜抽滤法观察线粒体膜牛磺酸转运体的性质及Hcy对牛磺酸转运功能的影响。结果: Hcy呈浓度依赖性地刺激大鼠心肌线粒体、亚线粒体氧自由基生成及SCR电子漏增加,牛磺酸自身不影响心肌线粒体、亚线粒体及SCR氧自由基生成,但呈浓度依赖性地抑制Hcy诱导的线粒体、亚线粒体及呼吸链重组体氧自由基生成。线粒体膜上存在Na+依赖性的牛磺酸转运体,Hcy呈浓度依赖性地抑制牛磺酸转运体对牛磺酸的转运功能。结论: 牛磺酸抑制Hcy刺激的线粒体呼吸链电子漏增加及氧自由基生成。线粒体膜上存在Na+依赖性的牛磺酸转运体,Hcy抑制线粒体膜上牛磺酸转运体对牛磺酸的转运功能。 相似文献
146.
J. Hirsch J. Leipziger U. Fröbe E. Schlatter 《Pflügers Archiv : European journal of physiology》1993,422(5):492-498
In the luminal membrane of rat cortical collecting duct (CCD) a big Ca2+-dependent and a small Ca2+-independent K+ channel have been described. Whereas the latter most likely is responsible for the K+ secretion in this nephron segment, the function of the large-conductance K+ channel is unknown. The regulation of this channel and its possible physiological role were examined with the conventional cell-free and the cell-attached nystatin patch-clamp techniques. Patch-clamp recordings were obtained from the luminal membrane of isolated perfused CCD segments and from freshly isolated CCD cells. Intracellular calcium was measured using the calcium-sensitive dye fura-2. The large-conductance K+ channel was strongly voltage- and calcium-dependent. At 3 mol/l cytosolic Ca2+ activity it was half-maximally activated. At 1 mmol/l it was neither regulated by cytosolic pH nor by ATP. At 1 mol/l Ca2+ activity the open probability (P
o) of this channel was pH-dependent. At pH 7.0 P
o was decreased to 4±2% (n=9) and at pH 8.5 it was increased to 425±52% (n=9) of the control. At this low Ca2+ activity the P
o of the channel was reduced by 1 mmol/l ATP to 8±4% (n=6). Cell swelling activated the large-conductance K+ channel (n=14) and hyperpolarized the membrane potential of the cells by 9±1 mV (n=23). Intracellular Ca2+ activity increased after hypotonic stress. This increase depended on the extracellular Ca2+ activity. A possible physiological function of the large-conductance K+ channel in rat CCD cells may be the reduction of the intracellular K+ concentration after cell swelling. Once this channel is activated by increases in the cytosolic Ca2+ activity it can be regulated by changes in cellular pH and ATP.Supported by DFG Schl 277/2-3 相似文献
147.
R. Stoll R. Kinne H. Murer H. Fleisch J. -P. Bonjour 《Pflügers Archiv : European journal of physiology》1979,380(1):47-52
In the present work we have investigated whether the changes in the renal handling of inorganic phosphate (Pi) induced by 1) dietary Pi, 2) removal of parathyroid glands and 3) 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], are associated with alterations in the Na-dependent Pi uptake by brush border membrane vesicles (BBMV) isolated from renal cortex. Shamoperated (SHAM) or thyroparathyroidectomized (TPTX) rats treated or not with 26 pmol/day of 1,25 (OH)2D3i.p. were fed low (0.2%) or high (1.2%)P diet for 7 days. The results showed that in SHAM, TPTX and TPTX+1,25 (OH)2D3 the Pi uptake by BBMV was greater after low than high Pi diet. It was greater in TPTX than in SHAM counterparts fed either diets. In TPTX fed low or high Pi diet 1,25 (OH)2D3 decreased the Pi uptake to the level observed in SHAM. A striking parallelism was found between variations in Pi uptake by BBMV and in the tubular Pi reabsorption of the whole kidney. The Na-dependent glucose, the mannitol uptake by BBMV, and the alkaline phosphatase activity in cortical homogenates and BBMV were not affected by the various treatments. Thus, dietary Pi, chronic TPTX and 1,25 (OH)2D3 appear to specifically affect the Na-dependent Pi transport system bound to the brush border membranes of renal cortical tubules. The alterations observed at this membrane level could account, at least in part, for the changes induced by these three factors on the overall tubular reabsorption of Pi. 相似文献
148.
H. Wald Michal Dranitzki-Elhalel R. Backenroth Mordecai M. Popovtzer 《Pflügers Archiv : European journal of physiology》1998,436(2):289-294
Vitamin D counters the phosphaturic action of parathyroid hormone (PTH) in rats in vivo. The present study was undertaken
to examine this interaction using monolayers of Opossum kidney (OK) cells. 32P uptake, cAMP generation, PTH/PTHrP receptor mRNA expression and intracellular Ca2+ [Ca2+]i were measured in (1) control cells, (2) cells exposed to PTH, (3) cells pretreated with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and (4) 1,25(OH)2D3-pretreated cells exposed to PTH. 32P uptakes were in (1) 5.00±0.20 (mean ±SE), in (2) 2.30±0.14 (P<0.001 versus group 1), in (3) 4.80±0.24 (P NS versus group 1) and in (4) 3.70±0.20 (P<0.001 versus group 2) nmol Pi/(mg·prot 10 mm). cAMP levels were in (1) 10±3, in (2) 210±8, in (3) 12±4, and in (4) 122±12 pmol cAMP/mg protein (P<0.001 versus group 2). PTH/PTHrP receptor mRNA expression was in relative units: (1) 100±0, (2) 99.5±6.2, (3) 68.7±2.6 (P<0.001 versus group 1), and (4) 34.8±3.3 (P<0.001 versus group 1). In groups 2 and 4 PTH induced equal transient increments in [Ca2+]i. These experiments demonstrate that the effect of vitamin D on phosphate transport is associated with a commensurate diminution
in PTH/PTHrP receptor gene expression and PTH-induced cAMP formation but not with Ca2+ transients. Vitamin D per se does not affect 32P uptake or cAMP generation while it slightly decreased PTH/PTHrP receptor gene expression. These observations demonstrate
that: (1) 1.25(OH)2D3 directly antagonizes the effects of PTH on 32P uptake in OK cells, (2) this effect is mediated via inhibition of PTH-induced activation of AC/cAMP system, (3) the diminution
in PTH-induced cAMP formation may stem at least in part from a decrease in the expression of PTH/PTHrP receptor mRNA.
Received: 2 December 1997 / Received after revision: 19 January 1998 / Accepted: 28 January 1998 相似文献
149.
E. Dietrichs 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1981,44(3):235-242
Summary The cerebellar parafloccular corticonuclear and nucleocortical connections were studied in the cat by means of anterograde and retrograde transport of horseradish peroxidase.Previous investigations have given evidence that the cortex of the paraflocculus can be subdivided into three zones. These zones are recognized as C2, D1 and D2. The material presented is compatible with the findings from previous reports with other methods that each of these zones sends its Purkinje axons to separate regions within the cerebellar nuclei. These terminal fields are the lateral part of nucleus interpositus posterior (the alleged nuclear zone C2) and the dentate nucleus and its transition area with nucleus interpositus anterior (the supposed nuclear D zones). The parafloccular corticonuclear fibres appear to terminate along a continuous mediolateral band extending from the NL through the NL-NIA transition area into the lateral NIP. This observation is in concordance with our previous findings concerning the termination of the cerebellar corticonuclear fibres (Dietrichs and Walberg 1979, 1980; Dietrichs 1981). Within the NL and NL-NIA transition area the Purkinje axons from the ventral paraflocculus terminate ventral to those from the dorsal paraflocculus.The nucleocortical projection shows the same zonal arrangement as the corticonuclear connection, indicating the presence of a corticonuclear-nucleocortical reciprocity.The findings are discussed with reference to previous studies on the parafloccular corticonuclear and nucleocortical connections, and some comments are made concerning the cerebellar zonal subdivision of this cortical area. 相似文献
150.
R. Nitschke J. Leipziger R. Greger 《Pflügers Archiv : European journal of physiology》1993,423(3-4):274-279
Cell swelling induced by hypotonic solution led to an osmolality-dependent increase in intracellular Ca2+ activity ([Ca2+]i) in HT29 cells. At moderate reductions in osmolality from 290 to 240 or 225 mosmol/l in most cases only a small monophasic increase of [Ca2+]i to a stable plateau of 10–20 nmol/l above resting [Ca2+]i was observed. Lower osmolalities resulted in a triphasic increase of [Ca2+]i to a peak value. In a first phase after the volume change, lasting 20–40 s, [Ca2+]i increased slowly by about 30 nmol/l. Thereafter [Ca2+]i increased more rapidly within 20–30 s to a peak value. This peak was 189±45 nmol/l (190 mosmol/l, n=9) and 243±41 nmol/l (160 mosmol/l, n=20) above resting [Ca2+]i. The peak was then followed by a decline of [Ca2+]i over the next 2–3 min to a stable plateau value of 28±6 (n=6) and 32±11 nmol/l (n=11) above resting [Ca2+]i at 190 and 160 mosmol/l, respectively. The plateau lasted as long as the hypotonic solution was present. Under Ca2+-free bath conditions the peak value for the cell-swelling-induced [Ca2+]i transient was reached significantly later (60–100 s, compared to 40–60 s under control conditions). The peak values under Ca2+-free conditions were not significantly lower. This indicates that the [Ca2+]i peak was mostly of intracellular origin. No [Ca2+]i plateau phase was observed under Ca2+-free bath conditions. With the use of the fura-2-Mn 2+ quenching technique an increased Ca2+ influx induced by hypotonic cell swelling was shown (160 mosmol/l; n=4). This influx started immediately after or simultaneously with the cell swelling and preceded the [Ca2+]i peak for more than 50 s.This study was supported by DFG grant Gr 480/10. 相似文献