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During acclimatization to the hypoxia of altitude, the cerebral circulation is exposed to arterial hypoxia and hypocapnia, two stimuli with opposing influences on cerebral blood flow (CBF). In order to understand the resultant changes in CBF, this study examined the responses of CBF during a period of constant mild hypoxia both with and without concomitant regulation of arterial P(CO2). Nine subjects were each exposed to two protocols in a purpose-built chamber: (1) 48 h of isocapnic hypoxia (Protocol I), where end-tidal P(O2) (P(ET,O2)) was held at 60 Torr and end-tidal P(CO2) (P(ET,CO2)) at the subject's resting value prior to experimentation; and (2) 48 h of poikilocapnic hypoxia (Protocol P), where P(ET,O2) was held at 60 Torr and P(ET,CO2) was uncontrolled. Transcranial Doppler ultrasound was used to assess CBF. At 24 h intervals during and after the hypoxic exposure CBF was measured and the sensitivity of CBF to acute variations in P(O2) and P(CO2) was determined. During Protocol P, P(ET,CO2) decreased by 13% (P < 0.001) and CBF decreased by 6% (P < 0.05), whereas during Protocol I, P(ET,CO2) and CBF remained unchanged. The sensitivity of CBF to acute variations in P(O2) and P(CO2) increased by 103% (P < 0.001) and 28% (P < 0.01), respectively, over the 48 h period of hypoxia. These changes did not differ between protocols. In conclusion, CBF decreases during mild poikilocapnic hypoxia, indicating that there is a predominant effect on CBF of the associated arterial hypocapnia. This fall occurs despite increases in the sensitivity of CBF to acute variations in P(O2)/P(CO2) arising directly from the hypoxic exposure. 相似文献
324.
Palermo GD; Avrech OM; Colombero LT; Wu H; Wolny YM; Fissore RA; Rosenwaks Z 《Molecular human reproduction》1997,3(4):367-374
Among the possible mechanisms of oocyte activation after sperm penetration,
it appears most likely that a protein released by the spermatozoon elicits
a calcium elevation in the ooplasm. To further test this idea, cytosolic
factors obtained from human spermatozoa by two different methods,
freezing-thawing and sonication, were injected into mouse oocytes following
which intracellular calcium release was measured. Of a total of 42 mouse
oocytes, a pattern of calcium oscillations was observed in nine out of 16
oocytes injected with sonicated fraction, in all of eight oocytes with the
frozen-thawed fraction and in none of 18 control oocytes. Injection of the
frozen- thawed fraction also produced regular calcium oscillations in all
of five in-vitro matured human oocytes. To assess the putative factor's
ability to support fertilization, human oocytes that were not activated by
prior intracytoplasmic injection of spermatozoa (ICSI) and round spermatids
were reinjected with the frozen-thawed sperm fraction. Of 23 human oocytes
which remained unfertilized after ICSI, 19 became activated after injection
with sperm cytosolic factor; eight showed two pronuclei, three one
pronucleus and eight showed three or more pronuclei. Of 11 oocytes
unfertilized after prior round spermatid injection, two developed two
pronuclei, four developed one pronucleus and two had three or more
pronuclei. Cytogenetic analysis by fluorescence in-situ hybridization
confirmed the existence of a male pronucleus in eight out of nine such
zygotes displaying two or more pronuclei. Thus, human sperm extracts
activated mouse and human oocytes after injection, as judged by calcium
flux patterns in conjunction with male pronucleus formation.
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Office blood pressure (BP) measurements by sphygmomanometer are not necessarily representative of patient''s usual blood pressure. In contrast, ambulatory blood pressure measurements (ABPM) represent a large number of readings and may reflect the actual BP status of an individual. In this study, 150 individuals were studied in 2 groups. 110 patients (group A) had stage I & II, hypertension based on casual BP readings. 26 (23.6%) of them were found to be normontensive as per existing ABPM standard. There were 40 patients with poorly controlled hypertension on multiple drugs (group B). The trough/peak ratio of > 50% was seen in 12.5% of these patients at start of study. This increased to 84.8% after modification of drugs as per the profile on ABPM, thus indicating usefulness in achieving a smoother control.Key Words: Ambulatory blood pressure, White coat hypertension 相似文献
328.
Gooding GA; Berger MS; Linkowski GD; Dillon WP; Weinstein PR; Boggan JE 《Radiology》1986,160(1):272-273
To determine the effect of transducer frequency, we used intraoperative spinal ultrasound to study 15 patients. All patients but one had spinal stenosis and/or disk disease affecting the cervical cord (n = 5), the thoracic cord (n = 1), or the lumbosacral area (n = 8). One patient had an arteriovenous malformation of the cervical cord. Both 5-MHz and 10-MHz transducers were used in one patient; a transducer with the option of 3.5, 5, or 7.5 MHz was used in ten; and a 10-MHz transducer was used in four. We found that, intraoperatively, 10-MHz transducers currently produce the most detailed images of the spine. 相似文献
329.
Precipitating stimuli were investigated in a 24-year-old woman with primary reading epilepsy. Reading material was presented on a microcomputer video display monitor under controlled conditions while the patient underwent EEG radiotelemetry/video monitoring. We examined the relative contribution of the following variables utilizing a factorial design: eye movements, reading aloud versus reading silently, linguistic complexity, and concentrations. None of these factors acted solely as the critical stimulus in provoking seizures. Seizures were most readily elicited when the patient read aloud, using material of medium or high linguistic complexity with the usual scanning eye movements for reading. 相似文献