全文获取类型
收费全文 | 3585272篇 |
免费 | 264112篇 |
国内免费 | 8726篇 |
专业分类
耳鼻咽喉 | 48987篇 |
儿科学 | 118733篇 |
妇产科学 | 99873篇 |
基础医学 | 504089篇 |
口腔科学 | 102325篇 |
临床医学 | 325675篇 |
内科学 | 697870篇 |
皮肤病学 | 82703篇 |
神经病学 | 294087篇 |
特种医学 | 139546篇 |
外国民族医学 | 1129篇 |
外科学 | 536423篇 |
综合类 | 79400篇 |
现状与发展 | 6篇 |
一般理论 | 1407篇 |
预防医学 | 279353篇 |
眼科学 | 81925篇 |
药学 | 265413篇 |
10篇 | |
中国医学 | 6976篇 |
肿瘤学 | 192180篇 |
出版年
2018年 | 37687篇 |
2017年 | 29195篇 |
2016年 | 33568篇 |
2015年 | 38162篇 |
2014年 | 52502篇 |
2013年 | 79653篇 |
2012年 | 105882篇 |
2011年 | 111881篇 |
2010年 | 67277篇 |
2009年 | 64491篇 |
2008年 | 105318篇 |
2007年 | 111647篇 |
2006年 | 113502篇 |
2005年 | 109339篇 |
2004年 | 106148篇 |
2003年 | 102197篇 |
2002年 | 99087篇 |
2001年 | 167462篇 |
2000年 | 172139篇 |
1999年 | 145642篇 |
1998年 | 42074篇 |
1997年 | 37619篇 |
1996年 | 37614篇 |
1995年 | 36540篇 |
1994年 | 33813篇 |
1993年 | 31766篇 |
1992年 | 116068篇 |
1991年 | 112648篇 |
1990年 | 109382篇 |
1989年 | 105965篇 |
1988年 | 97703篇 |
1987年 | 95988篇 |
1986年 | 90799篇 |
1985年 | 87039篇 |
1984年 | 65169篇 |
1983年 | 55713篇 |
1982年 | 33010篇 |
1981年 | 29680篇 |
1979年 | 59720篇 |
1978年 | 41891篇 |
1977年 | 35578篇 |
1976年 | 33186篇 |
1975年 | 35382篇 |
1974年 | 42364篇 |
1973年 | 40412篇 |
1972年 | 37762篇 |
1971年 | 35277篇 |
1970年 | 32495篇 |
1969年 | 31078篇 |
1968年 | 28411篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Rats exposed on their first postnatal day to 100% nitrogen for 25 min developed hyperactivity and lower performance in passive avoidance task during development. Administration of MK-801 (0.5 mg/kg i.p.) 1 h before anoxia or (0.25 and 0.5 mg/kg) 1 h after completely reversed this behavioral impairment. Senescent rats (24-26 months) exposed to hypoxia (92% N2 + 8% O2) for 5 h failed in their performance in C.A.R., 30 days later. Pretreatment with MK-801 (1 mg/kg i.p.) completely reversed this impairment. These data suggest that activation of endogenous NMDA receptors produces different behavioral consequences in neonatal and senescent rats and that MK-801 administration close to exposure of animals to anoxia or hypoxia can prevent such damage, thus preventing behavioral impairments in postnatal as well as in senescent rats. 相似文献
992.
Z M Huang D Thewke Q Q Gong D Schlichter W D Wicks 《Brain research. Molecular brain research》1991,11(3-4):309-319
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences. 相似文献
993.
The diagnosis of albinism is indicated by the presence of visual pathway misrouting in which temporal retinal fibers erroneously decussate at the optic chiasm disrupting the normal topographical distribution of retinal geniculate-cortical projections. Detection of misrouted fibers is effected by non-invasive electrophysiological assessment of the topographical representation of the visual evoked potential (VEP) following full field monocular stimulation. By combining appropriate state defined neonatal recording procedures with the albino VEP test paradigm, the presence of aberrant optic pathway projections was detected in a five-day-old full-term infant. The electrophysiological signature pathognomonic to albinism was observed within a long (300 ms) latency window of an otherwise normal neonatal luminance flash response. The results of this study indicate that the VEP misrouting test can be extended to reliable albino diagnosis within the neonatal period. 相似文献
994.
Thirty outpatients with panic disorder (PD) were treated at an anxiety clinic using a symptom-focused approach. Thirteen (43%) had no history of major depressive disorder (MDD), 12 (40%) had a history of secondary MDD, and 5 (17%) had history of primary MDD. The outcome was equally good in patients with no history of MDD (77% had good or excellent outcomes) and patients with a history of secondary MDD (83% had good or excellent outcomes). Patients with a history of primary MDD had the worst outcomes. These findings agree with earlier studies showing that secondary MDD does not adversely affect prognosis of patients presenting for treatment of PD. 相似文献
995.
Peter D. Le Roux David S. Jardine Paul M. Kanev John D. Loeser 《Child's nervous system》1991,7(1):34-39
We reviewed the results of all pediatric patients undergoing intracranial pressure (ICP) monitoring in a 2-year period at our institution. The outcome of patients suffering hypoxia or ischemic injuries (HII) is compared to those suffering non-hypoxic or non-ischemic injuries (NHII). Thirty-four patients had ICP monitors placed during the study period. Inconplete patient information led to the exclusion of 5 patients. An additional 5 patients were excluded because no measures to control ICP were taken after the monitor was placed. Twenty-four patients required treatment for raised ICP (hyperventilation, 24; mannitol, 19; barbiturate coma, 6). Admission Glasgow Coma Score in patients suffering HII (median score 5) and NHII (median score 6) were not significantly different (Mann-Whitney U Test). Only 2 of 8 patients with HII were near-drowning vietims. The remaining 6 had HII from other causes (5 survivors of various forms of asphyxia and 1 of cardiac arrest). All 8 patients had poor outcomes (1 severely disabled; 7 died). The 16 patients with NHII had a variety of diagnoses (6 trauma, 5 encephalitis, 4 bacterial meningitis, 1 diabetic ketoacidosis). Among these, 6 had good outcomes and 10 poor outcomes (2 severely disabled, 2 vegetative, and 6 died). The difference in outcome between patients with NHII and HII is significant at P=0.059 (Fischer Exact test). Patients with NHII may benefit from ICP monitoring. Patients with HII from near-drowning and other causes did not appear to benefit from ICP monitoring and interventions directed at controlling ICP. 相似文献
996.
In vivo microdialysis coupled with HPLC and radioimmuno-assay techniques were used to analyze dopamine (DA) and neurotensin (NT) in prefrontal cortical extracellular fluid following electrical stimulation of mesocortical axons. The release (overflow into the extracellular fluid) of both DA and NT increased with increasing number of impulses and with frequency. At the lowest frequency tested (2.5 Hz), DA release was significantly increased, while there was no significant increase in the release of NT. As the frequency of stimulation was increased from 2.5 to 20 Hz, the ratio of extracellular DA:NT decreased exponentially. Stimulation in a burst pattern produced greater release of both DA and NT than tonic stimulation when the number of impulses per second and the total number of impulses were held constant. Furthermore, blockade of DA autoreceptors with sulpiride stereoselectively increased the release of DA while decreasing the release of NT. These data suggest that the release of coexistent molecules (DA and NT) from mesocortical neurons can be influenced by physiological and pharmacological factors such that under certain conditions simultaneous or differential release may occur. 相似文献
997.
The effects of hyponatraemia and subarachnoid haemorrhage on the cerebral vasomotor responses of the rabbit 总被引:1,自引:0,他引:1
R J Nelson S Perry A C Burns J Roberts J D Pickard 《Journal of cerebral blood flow and metabolism》1991,11(4):661-666
Impairment of cerebral autoregulation and development of hyponatraemia are both implicated in the pathogenesis of delayed cerebral ischaemia and infarction following subarachnoid haemorrhage (SAH) but the pathophysiology and interactions involved are not fully understood. We have studied the effects of hyponatraemia and SAH on the cerebral vasomotor responses of the rabbit. Cerebrovascular reactivity to hypercapnia and cerebral autoregulation to trimetaphan-induced hypotension were determined in normal and hyponatraemic rabbits before and 6 days after experimental SAH produced by two intracisternal injections of autologous blood. Hyponatraemia (mean plasma sodium of 119 mM) was induced gradually over 48 h by administration of Desmopressin and intraperitoneal 5% dextrose. Sham animals received normal saline. The cerebrovascular reactivity (% change +/- SD in cortical CBF/mm Hg PaCO2, measured by hydrogen clearance) of hyponatraemic (4.8 +/- 3.0%) and SAH (1.3 +/- 2.0%) animals was significantly less (p less than 0.05) than control (11.6 +/- 4.0%) and sham (8 +/- 2.0%) animals, whereas the reactivity of hyponatraemic-SAH animals was preserved (9.8 +/- 6.0%). Hyponatraemia and SAH alone each significantly impaired CBF autoregulation but their combined effects were not additive. Systemic hyponatraemia impairs normal cerebral vasomotor responses but does not augment the effects of experimental SAH in the rabbit. 相似文献
998.
B A Davis D A Durden R L O'Reilly 《Progress in neuro-psychopharmacology & biological psychiatry》1991,15(4):503-512
1. The plasma concentrations of unconjugated phenylacetic acid and m-hydroxyphenylacetic acid are lower in male than in female subjects. 2. The plasma concentrations of unconjugated phenylacetic acid and mandelic acid decrease with increasing weight and height for all subjects combined. The same relationships apply for both males and females but are significant only for males. 3. Homovanillic and vanillylmandelic acid concentrations in plasma increase with age. 4. The importance of using age, sex, weight and height matched groups in studies involving the plasma concentrations of some of the trace amine metabolites in psychiatric disorders has been demonstrated. This is particularly the case for phenylacetic acid, the major metabolite of phenylethylamine which is now thought to be a neuromodulator of catecholaminergic neurotransmission. 相似文献
999.
Tumors arising from the sciatic nerve are a rare occurrence. A case is described of such a tumor developing as a large painless mass in the posterior right midthigh. The preoperative diagnosis was easily achieved by means of ultrasonography and computed tomography. Excision of the tumor, with preservation of the involved nerve, was performed. Microscopic examination showed a neurofibroma with however some features of a schwannoma. Problems of histological diagnosis and treatment are emphasized. 相似文献
1000.