全文获取类型
收费全文 | 8046篇 |
免费 | 546篇 |
国内免费 | 167篇 |
专业分类
耳鼻咽喉 | 37篇 |
儿科学 | 194篇 |
妇产科学 | 253篇 |
基础医学 | 1437篇 |
口腔科学 | 162篇 |
临床医学 | 374篇 |
内科学 | 1563篇 |
皮肤病学 | 88篇 |
神经病学 | 1005篇 |
特种医学 | 197篇 |
外科学 | 438篇 |
综合类 | 679篇 |
现状与发展 | 2篇 |
预防医学 | 1446篇 |
眼科学 | 104篇 |
药学 | 605篇 |
1篇 | |
中国医学 | 102篇 |
肿瘤学 | 72篇 |
出版年
2024年 | 6篇 |
2023年 | 97篇 |
2022年 | 103篇 |
2021年 | 447篇 |
2020年 | 322篇 |
2019年 | 227篇 |
2018年 | 233篇 |
2017年 | 198篇 |
2016年 | 230篇 |
2015年 | 286篇 |
2014年 | 404篇 |
2013年 | 540篇 |
2012年 | 419篇 |
2011年 | 409篇 |
2010年 | 358篇 |
2009年 | 375篇 |
2008年 | 347篇 |
2007年 | 374篇 |
2006年 | 308篇 |
2005年 | 289篇 |
2004年 | 325篇 |
2003年 | 279篇 |
2002年 | 251篇 |
2001年 | 168篇 |
2000年 | 123篇 |
1999年 | 134篇 |
1998年 | 140篇 |
1997年 | 138篇 |
1996年 | 119篇 |
1995年 | 99篇 |
1994年 | 83篇 |
1993年 | 102篇 |
1992年 | 83篇 |
1991年 | 77篇 |
1990年 | 79篇 |
1989年 | 55篇 |
1988年 | 55篇 |
1987年 | 39篇 |
1986年 | 60篇 |
1985年 | 60篇 |
1984年 | 58篇 |
1983年 | 34篇 |
1982年 | 49篇 |
1981年 | 39篇 |
1980年 | 33篇 |
1979年 | 23篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 17篇 |
1973年 | 5篇 |
排序方式: 共有8759条查询结果,搜索用时 296 毫秒
21.
Age-related Changes in Excitability and Recurrent Inhibition in the Rat CA1 Hippocampal Region 总被引:1,自引:0,他引:1
Costas Papatheodoropoulos George Kostopoulos 《The European journal of neuroscience》1996,8(3):510-520
In hippocampal slices from male Wistar rats aged 1–34 months, we recorded the synaptic field potential responses of the CA1 neurons to stimulation of Schaffer collaterals. Eight electrophysiological indexes were extracted from input/output curves and compared in 11 age groups from 1 to 30 months. Neuronal excitability presented a U-shaped curve of development with a minimum at ˜7–8 months of age. There was a significant continuous increase in neuronal excitability, i.e. a decrease in excitatory postsynaptic potential (EPSP) producing both the threshold and half-maximal population spike from middle age (8–10 months) to senescence (30 months). Synaptic efficiency also increased in old rats to reach a maximum during senescence, i.e. both the current for threshold EPSP and that for half-maximal EPSP reached a minimum in senescence, although the earlier developmental patterns of these two indexes were non-linear. The duration of the field EPSP elicited with maximal stimulation presented an abrupt decay after the first month. Aged animals presented a relatively small maximal population spike. Recurrent inhibition was most prominent on neuronal excitability rather than synaptic strength. Measured as the percentage change in the half-maximal EPSP and half-maximal population spike, recurrent inhibition was found to decrease during the first 7–10 months of life and remained small in later development. 相似文献
22.
This case report documents the first patient from main land China with an HTLV-1-associated myelopathy. The available epidemiological data suggest a low rate of HTLV 1 infection in China, although the surveys are comparatively small. Possible transmission routes and the risk of encountering the disease outside endemic areas are discussed. 相似文献
23.
Y. F. CHEUNG C. F. CHAN C. W. LEE Y. L. LAU 《Journal of paediatrics and child health》1994,30(2):173-175
An outbreak of Pneumocystis carinii pneumonia (PCP) in three patients within a 6 week period was reported. Two patients had acute lymphoblastic leukaemia and one had brain-stem glioma. They shared common features of immuno-suppression and absence of cotrimoxazole prophylaxis and had been nursed in the same room. The severity of PCP and its response to treatment may be related to the degree of immunosuppression. Because of the morbidity and mortality of PCP, chemoprophylaxis should be given to all at-risk cases. Furthermore, isolation of patients with PCP should be considered in view of increasing evidence of nosocomial transmission. 相似文献
24.
【目的】研究拉米夫定对HBsAg阳性孕妇的乙肝病毒 (HBV)宫内阻断作用。【方法】拉米夫定组 43例 ,孕 2 8周起口服拉米夫定 ,每天 10 0mg至产后 30d。对照组 5 2例 ,未予用药。两组孕妇均于孕 2 8周、分娩前 ,其新生儿于生后 2 4h内免疫接种前抽静脉血检测HBsAg、HBeAg及HBV的定量。【结果】拉米夫定组孕妇HBV的DNA水平显著下降 (P <0 0 5 ) ,其新生儿宫内感染率 (16 3% )明显低于对照组 (32 7% ) ,P <0 0 5。两组孕妇及其新生儿未发现有不良反应。【结论】携带HBV孕妇产前服用拉米夫定可有效减少HBV宫内感染发生率。 相似文献
25.
Neuromuscular transmission as a function of motor unit size in patients with prior poliomyelitis. 总被引:2,自引:0,他引:2
We studied neuromuscular transmission in 16 patients with prior poliomyelitis by measuring single fiber electromyographic (SFEMG) jitter. This was compared with 3 indirect methods of assessing reinnervation: SFEMG fiber density, macro EMG, and the presence of fiber type grouping on muscle biopsy. In patients with acute poliomyelitis before the age of 10, there was a positive correlation between the extent of neuromuscular transmission impairment, demonstrated by increased SFEMG jitter, and the enlargement of the motor unit, as indicated by increased fiber density, increased macro EMG signals, and fiber type grouping on muscle biopsy. However, there was no correlation between any of these parameters and the presence or absence of new symptoms of weakness. These findings suggest that impaired neuromuscular transmission is most common in patients with prior poliomyelitis whose motor units have been maximally enlarged by axonal sprouting, but is independent of the presence or absence of new symptoms of weakness. 相似文献
26.
Gregory Carey 《Behavior genetics》1991,21(5):433-444
The evolutionary implications of the path-analysis model most often used in human behavior genetics are examined. With directional selection, a model of pure vertical environmental transmission does not respond in a fully adaptive fashion. Unless the coefficients of transmission are exactly 0.50, the population mean will not equilibrate at the selective optimum over time. If there is both genetic and vertical environmental transmission, then the population mean can equilibrate at the selective optimum. In the presence of genetic transmission, vertical environmental transmission increases population fitness and has a strong effect on the rapid movement of the mean toward the selective optimum. This raises the intriguing paradox of why empirical evidence suggests that vertical environmental transmission is usually small when it possesses such important fitness properties.This work was supported in part by Grant DA05131 from the National Institute on Drug Abuse. 相似文献
27.
28.
海岛纤恙螨经卵传递恙虫病立克次体的研究 总被引:1,自引:0,他引:1
1985年8月~1986年11月,作者以我国发现的恙螨新种海岛纤恙螨子代幼虫656只,分为21组,叮咬健康小鼠,从子1代到子4代幼虫叮咬过的小鼠中,连续分离出7株恙虫病立克次体,证明海岛纤恙螨能够经卵传递恙虫病立克次体至少4代.同时在该螨的卵、幼虫、若虫、成虫组织细胞内发现有恙虫病立克次体寄生,并发现有分裂增殖形态的立克次体,证明海岛纤恙螨各变态期内均保有恙虫病立克次体,这些立克次体能在恙螨体内大量增殖,连续传代.此项研究结果,对于确认海岛纤恙螨为浙江沿海地区恙虫病的传染媒介和宿主,提供了重要的科学依据. 相似文献
29.
从1985年4月到1986年4月对361名孕妇进行的乙型肝炎流行病学横断面研究以及196名产妇一年随访研究的结果表明,361例孕妇的HBsAg阳性率为2.5%,抗-HBs阳性率为23.8%,抗-HBc阳性率为22.1%,HBV总感染率为31.3%;抗-HBs阳性、抗-HBs和抗-HBc共存阳性者占总阳性者的76.1%,说明人群感染HBV后大多产生了免疫力.1986年4月复查了196例产妇,133名在1985年HBV标记阴性者中有6人获得了HBV标记,HBV新感染率为4.5%;1例为急性乙型肝炎病人,5例为亚临床感染.HBV新感染者的感染途径不明,但医源性传播不能排除.1986年检查的148对夫妇中,男性HBsAg阳性率是女性的3.1倍(6.1%对2.0%),男性单独抗-HBc阳性率是女性的2.3倍(6.1%对2.7%),抗-HBs、抗-HBs和抗-HBc共存以及HBV感染率男女性间都无显著差异. 相似文献
30.
The effects on endometrial morphology of a single, intramuscular dose of 100 mg of progesterone administered in the early luteal phase, between days LH + 1 and LH + 6, were studied in a group (n = 8) of normal, fertile subjects by morphometric techniques and transmission electron microscopy. While the dose of progesterone administered consistently resulted in an increase of salivary progesterone concentration to above the upper limit of the reference range, no significant effect on endometrial development was observed; in particular, endometrial development was not advanced. 相似文献