全文获取类型
收费全文 | 1725篇 |
免费 | 140篇 |
国内免费 | 37篇 |
专业分类
耳鼻咽喉 | 53篇 |
儿科学 | 39篇 |
妇产科学 | 2篇 |
基础医学 | 372篇 |
口腔科学 | 22篇 |
临床医学 | 231篇 |
内科学 | 123篇 |
皮肤病学 | 9篇 |
神经病学 | 403篇 |
特种医学 | 27篇 |
外科学 | 51篇 |
综合类 | 91篇 |
预防医学 | 60篇 |
眼科学 | 55篇 |
药学 | 308篇 |
中国医学 | 36篇 |
肿瘤学 | 20篇 |
出版年
2023年 | 18篇 |
2022年 | 29篇 |
2021年 | 54篇 |
2020年 | 58篇 |
2019年 | 52篇 |
2018年 | 68篇 |
2017年 | 56篇 |
2016年 | 59篇 |
2015年 | 63篇 |
2014年 | 74篇 |
2013年 | 86篇 |
2012年 | 94篇 |
2011年 | 91篇 |
2010年 | 71篇 |
2009年 | 70篇 |
2008年 | 67篇 |
2007年 | 64篇 |
2006年 | 57篇 |
2005年 | 46篇 |
2004年 | 45篇 |
2003年 | 49篇 |
2002年 | 47篇 |
2001年 | 32篇 |
2000年 | 26篇 |
1999年 | 25篇 |
1998年 | 38篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 28篇 |
1994年 | 14篇 |
1993年 | 19篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 10篇 |
1986年 | 20篇 |
1985年 | 26篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 24篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有1902条查询结果,搜索用时 15 毫秒
1.
目的为抑制脑血栓形成,合成与TF基因启动子区切应力反应元件(SSRE)形成三链DNA的硫代磷酸酯寡核苷酸(TFO)。方法设计TFO序列14条,采用固相亚磷酰胺三酯固相法合成TFO。硫代磷酸酯修饰在TFO的3'末端进行。应用电泳迁移分析(EMSA)观察寡核苷酸和硫代脱氧寡核苷酸的亲和性。结果在设计合成的14条寡核苷酸中,与靶序列能形成三链DNA的TFO只有T21GTa、T14GTa和T15GTa,其Kd值分别为3.6×10-10、1.0×10-9和1.0×10-8(M),经硫代磷酸酯修饰后分别为:2.3×10-9、3.8×10-9和1.5×10-8。结论硫代磷酸酯修饰的T21GTa-ps、T14GTa-ps和T15GTa-ps能够与TF基因启动子SSRE的3个位点形成三链DNA。 相似文献
2.
Masaru Kato Rie Kobayashi Ikuo Watanabe 《Documenta ophthalmologica. Advances in ophthalmology》1993,84(1):71-81
An unusual form of scotopic electroretinogram with a bright white stimulus, which consisted of a rectangular a-wave of normal amplitude and a b-wave of supernormal amplitude, was recorded in three patients with cone dysfunction. In addition to poor visual acuity, abnormal color vision and reduced amplitude of the photopic electroretinogram, these patients showed a 2-log unit elevation of the dark-adaptation threshold. Funduscopic examination and fluorescein angiography revealed fine granular pigment disturbances at the mascula. The relationship between the response of the dark-adapted electroretinogram versus stimulus intensity was unique to these patients. The b-wave thresholds were elevated by 1 log unit. The b-waves were reduced in amplitude and markedly delayed in implicit time to dim stimuli, but supernormal in amplitude and normal in implicit time to bright stimuli.Abbreviations GMP
guanosine monophosphate 相似文献
3.
Identification of differentially expressed genes in omental adipose tissues of obese patients by suppression subtractive hybridization 总被引:1,自引:0,他引:1
Qiu J. Ni Y. H. Gong H. X. Fei L. Pan X. Q. Guo M. Chen R. H. Guo X. R. 《南京医科大学学报(自然科学版)》2007,27(5):427-427
To identify differentially expressed genes between obese individuals and normal control, we have undertaken suppression subtractive hybridization (SSH). Omental adipose tissues were obtained via abdominal surgery for appendicitis in both 13 obese subjects[BMI (body mass index) 〉 30 kg/m(2)] and 13 normal subjects (BMI 〉 18 and 〈 25 kg/m(2)). 相似文献
4.
5.
指数曲线电刺激对周围神经移植的组织学影响 总被引:1,自引:0,他引:1
目的 :研究指数曲线电刺激对周围神经移植修复后神经再生的影响。方法 :将 1 2 0只Wistar成年雄性大鼠制成坐骨神经移植模型 ,随机分为A组 (对照组 )、B组 (弥可保组 )、C组(指数曲线电刺激组 ) ,给予不同的治疗 ,在不同时段观察步态、毛发、展爪反射 ,测定SFI、神经传导速度、小腿三头肌湿重等指标。结果 :指数曲线电刺激有助于神经传导的恢复 ,减慢小腿三头肌失神经的废用 ,加快SFI及神经远段变性的恢复。结论 :指数曲线电刺激有利于神经再生。 相似文献
6.
P. Apicella Eric Legallet Elisabeth Trouche 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,116(3):456-466
In the primate striatum, the tonically discharging neurons respond to conditioned stimuli associated with reward. We investigated
whether these neurons respond to the reward itself and how changes in the behavioral context in which the reward is delivered
might influence their responsiveness. A total of 286 neurons in the caudate nucleus and putamen were studied in two awake
macaque monkeys while liquid reward was delivered in three behavioral situations: (1) an instrumental task, in which reward
was delivered upon execution of a visually triggered arm movement; (2) a classically conditioned task, in which reward was
delivered 1 s after a visual signal; (3) a free reward situation, in which reward was delivered at irregular time intervals
outside of any conditioning task. The monkeys′ uncertainty about the time at which reward will be delivered was assessed by
monitoring their mouth movements. A larger proportion of neurons responsive to reward was observed in the free reward situation
(86%) than in the classically conditioned (57%) and instrumental tasks (37%). Among the neurons tested in all situations (n = 78), 24% responded to reward regardless of the situation and 65% in only one or two situations. Responses selective for
one particular situation occurred exclusively in the free reward situation. When the reward was delivered immediately after
the visual signal in the classically conditioned task, most of the neurons reduced or completely lost their responses to reward,
and other neurons remained responsive. Conversely, neuronal responses invariably persisted when reward was delivered later
than 1 s after the visual signal. This is the first report that tonic striatal neurons might display responses directly to
primary rewards. The neuronal responses were strongly influenced by the behavioral context in which the animals received the
reward. An important factor appears to be the timing of reward. These neurons might therefore contribute to a general aspect
of behavioral reactivity of the subject to relevant stimuli.
Received: 16 September 1996 / Accepted: 1 April 1997 相似文献
7.
ADEL ISSA SOUSSOU MOHAMED GAMAL HELMY RAMEZ RAOUF GUINDY ENRICO MARIA GRECO 《Pacing and clinical electrophysiology : PACE》1992,15(11):1804-1808
The pocing rate response of a new acceleration driven pulse generator (SWING 100, SORIN BIOMEDICA) was compared with simultaneous normal sinus rhythm (NSR) during two different treadmill exercises. This pacemaker has a gravitational acceleration sensor able to discriminate between physical activities and vibrations. Six healthy volunteers (three male, three female; aged 21.7 ± 4,3 years), with the pacemaker strapped to their right infraclavicular area, performed each test three times with different rise response curve (RRC) each time: fast, normal, and slow. The fall response curve used was the same as the rising one during each test. Pacing rates were recorded using the VEGA analyzer (SORIN BIOMEDICA) and compared with simultaneous NSR recorded by a 7-channel ECG recorder (MINGOGRAF 7, SIEMENS), During all tests immediate (within seconds) rapid increase in pacemaker rate was seen up to about 60 seconds, then a slower increase followed thereafter. The mean correlation between pacing rates and NSR during the Bruce tests were 0.7941 ± 0.10, 0.8562 ± 0.14, and 0.8292 ± 0.07; during the discontinous tests 0.7292 ± 0.16, 0.7233 ± 0.10, and 0.7480 ± 0.11 for fast, normal, and slow RRC, respectively. Each 30 seconds, nonsignificant differences were present between pacing rate and NSR during all the discontinuous tests; similar responses were observed only during the first two stages of Bruce tests after which NSR was significantly higher than pacemaker rates. The speed of rise to upper rate was the main difference between the different programs (fast, normal, and slow). The discontinuous tests showed that the pacemaker responds more to speed than to grade. In conclusion, the Swing pacemaker is easy to use and program, fast, reliable, and is able to mimic the normal sinus behavior especially during discontinuous activities. 相似文献
8.
Joseph V. Hajnal Ralph Myers Angela Oatridge Jane E. Schwieso Ian R. Young Graeme M. Bydder 《Magnetic resonance in medicine》1994,31(3):283-291
To assess the effect of stimulus correlated motion on the appearance of functional magnetic resonance images, conventional visual and motor protocols were each performed by four normal volunteers and an image co-registration technique was used to retrospectively monitor subject motion. In three studies synthetic data sets were constructed from single baseline images using the positional information obtained from the co-registration procedure. Cumulative difference images were then created from both the synthetic and functional image sets. Stimulus correlated motion was detected in all eight studies and the synthetic cumulative difference images showed striking similarities to the equivalent functional images in each case. 相似文献
9.
Single neuron activity was recorded in the monkey anterior putamen to compare visuomotor-related responses during operant bar-press behavior with visual discrimination of objects. Of 615 neurons recorded 9.8% (
) responded to the presentation of food during forced delay of access to the bar. Of these 60 neurons, 38 were also tested with nonfood, and 19 of these responded to the nonfood objects regardless of the following movement. The amplitude of the visual-related responses of some differential neurons was graded for different objects to reflect the relative degree of preference for the food presented. However, these responses disappeared in reaction time tasks in which the bar could be accessed for pressing immediately upon presentation of an object. The visual response latency of differential neurons ranged from 50 to 700 ms (mean ± SD, 386 ±211 ms), which was longer than that of the nondifferential responses (207 ± 204 ms). These results suggest that anterior putamen neurons might participate in estimation of visual information that could be related to forecasting movement. 相似文献
10.
Gerard A. Riley 《Journal of developmental and physical disabilities》1998,10(2):153-165
The use of stimulus modifications in teaching involves altering the materials of a task in order to simplify its execution. Though their use in teaching stimulus discriminations to people with developmental disabilities has been extensively investigated, less attention has been given to their utilization in teaching response topography. This paper offers some general guidelines about their use for this purpose. In relation to their design, it is suggested that the aim should be to reduce the demands made by task components, to eliminate components, and/or to increase the attentional value of the discriminating features of the response topography. In relation to their application, guidelines are suggested about when they should be employed in conjunction with response prompts; when they should be used, either alone or in conjunction with response prompts, in preference to response prompts alone; whether one or a series of modifications is required; and at what point during teaching should probe trials on the unmodified task be introduced. 相似文献