全文获取类型
收费全文 | 33407篇 |
免费 | 2343篇 |
国内免费 | 1038篇 |
专业分类
耳鼻咽喉 | 369篇 |
儿科学 | 416篇 |
妇产科学 | 372篇 |
基础医学 | 5175篇 |
口腔科学 | 505篇 |
临床医学 | 3439篇 |
内科学 | 5425篇 |
皮肤病学 | 804篇 |
神经病学 | 2397篇 |
特种医学 | 1607篇 |
外国民族医学 | 5篇 |
外科学 | 3808篇 |
综合类 | 2508篇 |
现状与发展 | 7篇 |
一般理论 | 9篇 |
预防医学 | 1842篇 |
眼科学 | 856篇 |
药学 | 3457篇 |
15篇 | |
中国医学 | 1065篇 |
肿瘤学 | 2707篇 |
出版年
2024年 | 60篇 |
2023年 | 414篇 |
2022年 | 1094篇 |
2021年 | 1511篇 |
2020年 | 862篇 |
2019年 | 947篇 |
2018年 | 1073篇 |
2017年 | 855篇 |
2016年 | 1095篇 |
2015年 | 1523篇 |
2014年 | 1837篇 |
2013年 | 1995篇 |
2012年 | 2844篇 |
2011年 | 2933篇 |
2010年 | 1715篇 |
2009年 | 1429篇 |
2008年 | 2002篇 |
2007年 | 1883篇 |
2006年 | 1684篇 |
2005年 | 1586篇 |
2004年 | 1245篇 |
2003年 | 1062篇 |
2002年 | 879篇 |
2001年 | 705篇 |
2000年 | 735篇 |
1999年 | 583篇 |
1998年 | 265篇 |
1997年 | 223篇 |
1996年 | 168篇 |
1995年 | 161篇 |
1994年 | 138篇 |
1993年 | 103篇 |
1992年 | 162篇 |
1991年 | 171篇 |
1990年 | 140篇 |
1989年 | 106篇 |
1988年 | 88篇 |
1987年 | 80篇 |
1986年 | 72篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 31篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
91.
In deep layers of the cat motor cortex, we have investigated the properties of neurons displaying trans-synaptically induced bursts. In in vivo experiments, extracellularly recorded burst neurons were separated into two subtypes based on their dependence on stimulation sites, the medullary pyramid or the ventrolateral (VL) thalamic nucleus, from which bursts of 10-20 spikes were triggered. The spike amplitude attenuation and frequency adaptation during a burst were more prominent in pyramid-dependent burst neurons than in VL-dependent burst neurons. Intracellular recordings in in vivo experiments revealed that pyramid-dependent bursts emerged from a long-lasting depolarization, while each spike during a VL-dependent burst was narrow in half-width and was followed by a fast AHP, similar to fast spiking neurons. In in vitro slice experiments, intracellular recordings were obtained from neurons that displayed a burst of attenuated spikes emerging from a long-lasting depolarization, and were also obtained from fast spiking neurons. They were morphologically recovered to be multipolar cells with sparsely spiny dendrites and local axonal networks, suggesting that they are inhibitory interneurons. The multipolar neurons displaying bursts of attenuated spikes may mediate the recurrent inhibition of pyramidal tract cells. 相似文献
92.
The present study examined the effects of nicotinamide on the D-amphetamine (AMPH)-induced dopamine (DA) depletion and energy metabolism change in the rat striatum. In chronic studies, co-administration of AMPH with desipramine, a drug that retards the metabolism of AMPH, (10 mg/kg, intraperitoneal [i.p.], respectively) caused a significant decrease of striatal DA content measured 7 days later. Pretreatment with nicotinamide (500 mg/kg, i.p.), the precursor molecule for the electron carrier molecule nicotinamide adenine dinucleotide (NAD), attenuated this effect of AMPH, whereas itself exerted no long-term effect on striatal DA content. In acute studies, a decrease in striatal adenosine triphospate/adenosine diphosphate (ATP/ADP) ratio was found 3 h after co-injection of AMPH and desipramine. However, nicotinamide pretreatment blocked the reduced striatal ATP/ADP ratio and resulted in a striking increase in striatal NAD content in AMPH-treated rats. Furthermore, nicotinamide was noted to increase striatal ATP/ADP ratio and NAD content in saline-treated rats. These findings suggest that nicotinamide protects against AMPH-induced DAergic neurotoxicity in the striatum of rats via energy supplement. 相似文献
93.
94.
Hyperfibrinogenemia is an independent risk factor for atherosclerotic renal artery stenosis 总被引:2,自引:0,他引:2
Park JS Park JH Kang JY Yang WS Kim SB Park SW Park SJ 《American journal of nephrology》1999,19(6):649-654
It is important to identify patients at risk for atherosclerotic renal artery stenosis because renal artery stenosis is a progressive disease and a potentially correctable problem. To determine the risk factors for atherosclerotic renal artery stenosis, we performed renal arteriography at the time of cardiac catheterization in 270 patients (M:F, 193:77, mean age: 59 years) with clinical ischemic heart disease. Before the procedure, demographic data, medical history, physical findings and laboratory data were obtained. The degree of coronary artery stenosis and renal artery stenosis was quantified with automatic edge detection technique. Significant renal artery stenosis, defined as a narrowing of the diameter by more than 50%, was identified in 28 (10%) patients. Three patients (1%) had bilateral disease. Significant coronary artery disease, defined as a narrowing of the diameter by more than 50%, was present in 231 patients (85%). By univariate logistic regression analysis, older age (68 +/- 8 vs. 58 +/- 10 years), the presence of hypertension (61% vs. 38%), the extent of coronary artery disease, a high fibrinogen level (391 +/- 93 mg/dl vs. 335 +/- 109 mg/dl), a low albumin level (3.9 +/- 0.4 g/dl vs. 4.1 +/- 0.4 g/dl), and a low hemoglobin level (12.5 +/- 1.6 g/dl vs. 13.5 +/- 1.6 g/dl) were associated with the presence of renal artery stenosis (p < 0.05). Serum lipids, lipoprotein(a), creatinine, sex, smoking, or diabetes were not associated. By multivariate logistic regression analysis, older age (OR: 2.43 analyzed by 10 years increment, p = 0.0001), the presence of hypertension (OR: 2.68, p = 0.039) and a higher fibrinogen level (OR: 1.63 analyzed by 100 mg/dl increment, p = 0. 038) were significant risk factors of renal artery stenosis. Fibrinogen level was negatively correlated with albumin level (r = -0.18, p = 0.004). These results suggest that hyperfibrinogenemia as well as old age and hypertension are independent risk factors for atherosclerotic renal artery stenosis. Copyright Copyright 1999 S. Karger AG, Basel 相似文献
95.
(-)-Epiafzelechin: cyclooxygenase-1 inhibitor and anti-inflammatory agent from aerial parts of Celastrus orbiculatus. 总被引:1,自引:0,他引:1
K R Min B Y Hwang H S Lim B S Kang G J Oh J Lee S H Kang K S Lee J S Ro Y Kim 《Planta medica》1999,65(5):460-462
An inhibitor of cyclooxygenase (COX)-1 activity of prostaglandin H2 synthase was isolated from aerial parts of Celastrus orbiculatus Thunb. (Celastraceae), an oriental folk medicine for rheumatoid arthritis by activity-guided column chromatographic methods. The COX inhibitor was identified as (-)-epiafzelechin, a member of flavan-3-ols by the structural analysis with HR-EI-mass, 1H-NMR and 13C-NMR spectral data. The compound exhibited a dose-dependent inhibition on the COX activity with an IC50 value of 15 microM. (-)-Epiafzelechin exhibited about 3-fold weaker inhibitory potency on the enzyme activity than indomethacin as a positive control. (-)-Epiafzelechin exhibited significant anti-inflammatory activity on carrageenin-induced mouse paw edema when the compound (100 mg/kg) was orally administrated at 1 h before carrageenin treatment. 相似文献
96.
Hak Cheol Kwon Byeong Gon Lee Seung Hee Kim Chil Mann Jung Sung Youl Hong Jeung Whan Han Hyang Woo Lee Ok Pyo Zee Kang Ro Lee 《Archives of pharmacal research》1999,22(4):410-413
In bioassay-guided search for inducible nitric oxide synthase (iNOS) inhibitory compounds from higher plants of South Korea, two beta-carboline alkaloids, 4-methoxy-1-vinyl-beta-carboline (1) and 4,8-dimethoxy-l-vinyl-beta-carboline (2) have been isolated from the cortex of Melia azedarach var. japonica. The structures of these compounds were elucidated on the basis of spectroscopic data. Compounds 1 and 2 showed marked inhibitory activity of iNOS on LPS- and interferon-gamma-stimulated RAW 264.7 cells. 相似文献
97.
Won-Jea Cho Su-Jeong Yoo Byung-Ho Chung Bo-Gil Choi Seung Hoon Cheon Soon-Ho Whang Sin-Kyu Kim Boo-Hyon Kang Chong-Ock Lee 《Archives of pharmacal research》1996,19(4):321-325
Aiming at the development of anticancer agents by modification of phenolic benzo[c]phenanthridine alkaloid, additional hydroxyl group was put on C10 position of fagaridine (1) by a biomimetic synthetic procedure to afford 10-hydroxyfagaridine (12). All of the synthetic intermediates were also screenedin vitro antitumor activities against five different cell lines as well as12. Among them the representative cytotoxic results are shown as follows;p-quinone (11) [ED50 (A549=0.22 μg/ml), (HCT15=0.21 μg/ml), fagaridine (1) (HCT 15=0.41 μg/ml), olefin (6) (HCT 15=0.06 μg/ml), acetal (7) (SKMEL-2=0.07 μg/ml), dihydrofagaridne (10) (A549=0. 38 μg/ml), 10-hydroxyfagaridine (12) (A 549=0.45 μg/ml). From these observation three main remarks can be drawn; (i) the iminium part of benzo[c]phenanthridine is not essential for showing acitvities, (ii) the additional hydroxyl group did not contribute to enhance the cytotoxicity, (iii) the 3-arylisoquinolin-1(2H)-one derivatives were found to display significantin vitro antitumor activity. 相似文献
98.
College students' reports of their parents' handedness were compared with data provided by the parents themselves. The students' reports of their parents' writing hand were highly accurate, the reports of their parents' general handedness somewhat less so. For the latter measure, the students were asked, 'What is your mother's (father's) handedness?' and were given the choice 'left','either', 'right',and 'don't know'. Their answers were then compared with the investigators' classification based on the parents' answers to a 10-item hand-use questionnaire. For this measure, the accuracy of the students' reports was also found to be related to the students' own handedness. 相似文献
99.
We reported serial neuroradiological findings of a 20-year-old male with subacute sclerosing panencephalitis, who deteriorated from Jabbour stage 2 to stage 4 rapidly in spite of oral administration of inosine pranobex. At the stage 2, brain magnetic resonance imaging (MRI), computed tomography (CT) and [99mTc]-L, L-ethyl cysteinate dimer (99mTc-ECD) single photon emission computed tomography(SPECT) findings were normal. As the disease progressed, brain MRI and CT revealed diffuse cerebral white matter lesions as well as cerebral atrophy. 99mTc-ECD SPECT showed serially various perfusion of cerebrum. These findings in 99mTc-ECD SPECT may reflect the acute inflammatory process and consequent destruction of brain tissue. 相似文献
100.
目的 探讨胃肠术后 1号治疗急性弥漫性腹膜炎的疗效。方法 测定 2 0例急性弥漫性腹膜炎患者 (随机分为 2组 :对照组 10例 ,治疗组 10例 )血中乳酸、DAO水平。结果 急性弥漫性腹膜炎患者血中乳酸、DAO呈现不同程度升高 ,经治疗随病情好转 ,血中乳酸、DAO呈现不同程度下降 ,而治疗组血中乳酸、DAO下降幅度显著 ,优于对照组 (P <0 .0 5 )。结论 血中乳酸、DAO在急性弥漫性腹膜炎患者病理过程中起重要作用 ,可作为评估急性弥漫性腹膜炎患者严重程度的指标 ,胃肠术后 1号使乳酸、DAO水平下降 ,促进疾病恢复 相似文献