全文获取类型
收费全文 | 25286篇 |
免费 | 2578篇 |
国内免费 | 582篇 |
专业分类
耳鼻咽喉 | 260篇 |
儿科学 | 369篇 |
妇产科学 | 229篇 |
基础医学 | 2882篇 |
口腔科学 | 720篇 |
临床医学 | 2968篇 |
内科学 | 3099篇 |
皮肤病学 | 184篇 |
神经病学 | 1884篇 |
特种医学 | 1799篇 |
外国民族医学 | 5篇 |
外科学 | 2226篇 |
综合类 | 3149篇 |
现状与发展 | 1篇 |
一般理论 | 2篇 |
预防医学 | 2486篇 |
眼科学 | 500篇 |
药学 | 3201篇 |
36篇 | |
中国医学 | 1308篇 |
肿瘤学 | 1138篇 |
出版年
2024年 | 57篇 |
2023年 | 422篇 |
2022年 | 585篇 |
2021年 | 1223篇 |
2020年 | 1138篇 |
2019年 | 1037篇 |
2018年 | 1108篇 |
2017年 | 1051篇 |
2016年 | 950篇 |
2015年 | 987篇 |
2014年 | 1778篇 |
2013年 | 1784篇 |
2012年 | 1492篇 |
2011年 | 1617篇 |
2010年 | 1349篇 |
2009年 | 1159篇 |
2008年 | 1089篇 |
2007年 | 1146篇 |
2006年 | 1074篇 |
2005年 | 821篇 |
2004年 | 720篇 |
2003年 | 619篇 |
2002年 | 553篇 |
2001年 | 383篇 |
2000年 | 359篇 |
1999年 | 357篇 |
1998年 | 289篇 |
1997年 | 249篇 |
1996年 | 240篇 |
1995年 | 230篇 |
1994年 | 246篇 |
1993年 | 189篇 |
1992年 | 175篇 |
1991年 | 178篇 |
1990年 | 187篇 |
1989年 | 159篇 |
1988年 | 168篇 |
1987年 | 136篇 |
1986年 | 116篇 |
1985年 | 159篇 |
1984年 | 128篇 |
1983年 | 107篇 |
1982年 | 101篇 |
1981年 | 111篇 |
1980年 | 97篇 |
1979年 | 66篇 |
1978年 | 54篇 |
1977年 | 49篇 |
1976年 | 48篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
91.
T.G. van Kooten J.M. Schakenraad H.C. van der Mei A. Dekker C.J. Kirkpatrick H.J. Busscher 《Medical engineering & physics》1994,16(6):506-512
In this study, human umbilical vein and human saphenous vein endothelial cells were seeded on glass and exposed to fluid shear in a parallel-plate flow chamber. Cell retention, morphology and migration were studied as a function of shear stress and of adhesion time prior to exposure to shear. Three-hour and 24-h adhesion times gave rise to comparable cell retention values after 2 h of flow for both cell types. Cell retention decreased from 85 to 20% as shear stress increased from 88 to 264 dynes cm−2 (8.8 to 26 Pa). Mean spreading areas decreased after the onset of flow, but subsequently stabilized to plateau values, which were smaller at higher shear stresses. Shape factors increased faster to higher values as cells were exposed to higher shear stresses, without any obvious preference in orientation of the cells with respect to the direction of flow. Migration was unidirectional with flow and linear with time. Migration was faster for cells which had adhered for 24 h than for cells which had adhered for 3 h and was accompanied by the presence of fibrillar structures left behind on the surface upstream of migrating cells. It is concluded that after 3 h adhesion to glass, cells have adhered with an adhesion strength that does not substantially increase during the next 21 h. However, during this time changes in cell-substratum interactions seem to occur judging by the differences in, e.g., migration rates. 相似文献
92.
用机械分离法从豚鼠前庭感觉上皮中分离出不同种类的前庭感觉毛细胞(VHC)。VHC主要可分为Ⅰ型和Ⅱ型细胞。两种细胞形态虽有所差异,但一般均有四形或瓶形胞体,胞核位于细胞基部,胞颈和纤毛变化较大。细胞的活性可通过1%中性红染色鉴定,发现在室温下,1h内大约90%以上的分离VHC可维持其正常形态和活性。并参照对外毛细胞形态的研究提出活性VHC的鉴别标准。此项工作为进一步研究VHC的感觉机制和某些疾病的发生机理打下了基础。 相似文献
93.
94.
目的探讨首次自杀未遂者和重复自杀未遂者的区别.方法检查126名因自杀未遂而入院的患者,分为首次自杀未遂组和重复自杀未遂组,获得有关的临床资料并进行自杀意图及自杀企图冲动性和致死性的测定,将有关项目作对比分析.结果有51(40.5%)名重复自杀未遂者,与首次自杀未遂者比较,重复自杀未遂者已婚居多、文化程度较低、缺乏固定的经济收入、有较多的既往精神科治疗史、常饮酒、企图自杀前与他人交流少,自杀意图较低,冲动性较高(P均<0.05).结论对伴有某些危险因素的自杀未遂者应积极进行医学干预,以期减少自杀行为的再次发生. 相似文献
95.
Bennet Givens 《Psychopharmacology》1997,129(2):135-140
Acute exposure to ethanol produces deficits in sustained attention in humans, but these attentional deficits have not been
modeled in animals. In this study, an operant task was used to investigate the effects of low and moderate doses of ethanol
on sustained attention in rats. Performance on a two-choice reaction time task over a 1-h session was assessed immediately
following administration of ethanol (0.0, 0.5, 0.75, 1.0 and 1.5 g/kg IP). Each rat was required to respond to a light stimulus
of variable duration (20, 100, and 500 ms) occurring at one of two locations. Under control and saline conditions, increases
in stimulus length systematically increased choice accuracy and decreased reaction time. Ethanol produced a dose-dependent
decrease in choice accuracy that interacted with time, with an initial impairment that was stimulus length-dependent followed
by a general vigilance decrement. The data demonstrate that ethanol impaired the ability of rats to direct and sustain attention
to brief, infrequent stimuli, and provide a model for further investigations into the underlying neurobiological mechanisms
for ethanol-induced attentional deficits.
Received: 19 March 1996 / Final version: 30 August 1996 相似文献
96.
用统计学方法对14年来(1977~1990年)我校6746名新生(13492只眼)的视力状况进行分析。结果表明;新生正常视力逐年减少,视力不良率相应上升(P<0.001)。城市学生的视力比农村学生差,男生的视力优于女生(P<0.001)。17~19岁组的视力明显低于其他年龄组(P<0.001)。高考分数线升高与正常视力者减少呈明显负相关;而与视力不良者增加呈正相关(P<0.001,<0.05)。本文认为近距离用眼持续时间过长及环境视域小等是引起视力不良的主要原因。 相似文献
97.
This study describes a method for determining the number of radiographic rooms devoted to emergency radiology that would be
required to keep mean patient waiting time at a desired level.
A desired mean waiting time for patients must be determined. In our setting, a mean waiting time of 8 minutes resulted in
few complaints. The waiting time then sets the required utilization rate of available capacity. Daily and hourly volume and
variability in volume of examinations were measured over a 3-month period. This represents the demand. The needed number of
rooms is determined by comparing demand with effective available capacity for different numbers of rooms.
To maintain an 8-minute mean waiting time, 50% utilization of capacity is required. Mean demand on Sundays is 176 examinations.
Five rooms are required, since this gives a 180-examination effective capacity.
Using waiting time as the primary decision criterion for making capacity decisions in emergency radiology has several advantages:
the method is easy to use, volume variability is taken into account, and the focus is on service to patients. 相似文献
98.
2,4-二氯胺基酚(DCAP)是83—1除草剂在哺乳动物体内的主要代谢产物。本研究以三种染毒计划观察了DCAP诱发V79细胞的染色体畸变。结果表明:DCAP是一种染色体损伤剂,诱发的畸变主要为染色单体断裂和交换;3h染毒和染毒后培养17h诱发的染色体畸变率最高,20h染毒观察不到染色体畸变,说明以高浓度短期染毒对高细胞毒性化合物的细胞遗传毒性研究可能是较好的染毒方案。 相似文献
99.
蔡金梅 《中国医学文摘:老年医学》2003,(3)
目的:评估全肠外营养(TPN)对老年晚期消化系统恶性肿瘤病人生存期的影响。方法:回顾性分析121例老年晚期消化系统恶性肿瘤病人TPN治疗后的生存期。结果:TPN治疗后,患者生存期不同程度延长,为9~126天,平均68.1天,多数在两月左右。结论:TPN可延长老年晚期消化系统恶性肿瘤病人的生存期。 相似文献
100.
The effects of acute blood volume reduction induced by haemodialysison diastolic time intervals were studied in 19 patients by echo-and phonocardiography. Haemodialysis significantly decreasedleft ventricular diameters. The isovolumic relaxation time wasprolonged and negatively correlated with left ventricular enddiastolic dimensions. To study the effect of load reductionon left ventricular filling time, cardiac cycles with the sameRR interval, before and after haemodialysis, were compared.At any given RR interval dialysis resulted in a significantprolongation of the filling time. This study shows that diastolictime intervals are dependent on left ventricular loading conditions,and this effect should be considered when these time intervalsare evaluated in the clinical setting. 相似文献