全文获取类型
收费全文 | 4966篇 |
免费 | 293篇 |
国内免费 | 182篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 39篇 |
妇产科学 | 16篇 |
基础医学 | 568篇 |
口腔科学 | 64篇 |
临床医学 | 250篇 |
内科学 | 492篇 |
皮肤病学 | 225篇 |
神经病学 | 447篇 |
特种医学 | 83篇 |
外科学 | 159篇 |
综合类 | 448篇 |
现状与发展 | 1篇 |
预防医学 | 243篇 |
眼科学 | 72篇 |
药学 | 1742篇 |
1篇 | |
中国医学 | 437篇 |
肿瘤学 | 146篇 |
出版年
2024年 | 12篇 |
2023年 | 28篇 |
2022年 | 78篇 |
2021年 | 108篇 |
2020年 | 79篇 |
2019年 | 125篇 |
2018年 | 166篇 |
2017年 | 134篇 |
2016年 | 135篇 |
2015年 | 142篇 |
2014年 | 270篇 |
2013年 | 388篇 |
2012年 | 283篇 |
2011年 | 321篇 |
2010年 | 240篇 |
2009年 | 184篇 |
2008年 | 237篇 |
2007年 | 209篇 |
2006年 | 223篇 |
2005年 | 150篇 |
2004年 | 180篇 |
2003年 | 199篇 |
2002年 | 157篇 |
2001年 | 123篇 |
2000年 | 102篇 |
1999年 | 79篇 |
1998年 | 98篇 |
1997年 | 114篇 |
1996年 | 86篇 |
1995年 | 70篇 |
1994年 | 63篇 |
1993年 | 63篇 |
1992年 | 78篇 |
1991年 | 55篇 |
1990年 | 55篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 37篇 |
1985年 | 39篇 |
1984年 | 56篇 |
1983年 | 29篇 |
1982年 | 27篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1973年 | 5篇 |
排序方式: 共有5441条查询结果,搜索用时 15 毫秒
21.
22.
Using PC12 cells to study ethanol's effects on growth of neural processes, we found that ethanol enhances NGF- and basic FGF-induced neurite outgrowth. Chronic ethanol exposure selectively up-regulates δ and ε protein kinase C (PKC) and increases PKC-mediated phosphorylation in PC12 cells. Since PKC regulates differentiation, we investigated the role of PKC in enhancement of neurite outgrowth by ethanol. Like ethanol, 0.3–10 nM phorbol 12-myristate, 13-acetate (PMA) increased NGF-induced neurite outgrowth. However, higher concentrations did not, and immunoblot analysis demonstrated that 100 nM PMA markedly depleted cells of β, δ and ε PKC. PMA (100 nM) also down-regulated β, δ and ε PKC in ethanol-treated cells and completely prevented enhancement of neurite outgrowth by ethanol. In contrast, the cAMP analogue 8-bromoadenosine cAMP did not completely mimic the effectsof ethanol on neurite outgrowth, and ethanol was able to enhance neurite formation in mutant PC12 cells deficient in protein kinase A (PKA). These findings implicate β, δ or εPKC, but not PKA, in the neurite-promoting effects of ethanol and PMA. Since chronic ethanol exposure up-regulates δ and ε, but not βPKC, these findings suggest that δ or εPKC regulate neurite outgrowth. 相似文献
23.
7β-(6-取代-2-喹诺酮-3-乙酰氨基)头孢菌素的合成 总被引:1,自引:0,他引:1
以6-取代-2-喹诺酮-3-乙酸为侧链,用CDI法和潘化酯法与7-ADCA,7-ACA,7-ACT,和7-ACD缩合,合成了16个新的7β-(6-取代-2-喹诺酮-3-乙酰氨基)头孢菌素类化合物,通过溶媒转提,葡聚糖凝胶(Sephadex LH-20)柱层析及离心薄层层析分离精制,得到纯品。初步体外抑菌试验表明:新化合物对革兰氏阳性及某些阴性菌具有高度敏感性。大多数化合物对所试试验菌的抗菌活性与头孢唑啉和青霉素G钠相当,有些比它们还强。 相似文献
24.
Shimeru Kamihira Shigehiro Nakashima Shin Saitoh Michiko Kawamoto Yumiko Kawashima Mitoshi Shimamoto 《Cancer science》1993,84(8):834-837
A fully automated chemiluminescence immunoassay was developed for the detection of antibodies to HTLV-I. We used partially purified viral antigens coated on small polystyrene beads together with acridinium ester-labeled anti-human immunoglobulin G mouse immunoglobulin G in this method. A good agreement was observed between our proposed method, the indirect immunofluorescence assay, the particle-agglutination test and the enzyme immunoassay. This new method, which is simple, sensitive, specific and rapid, should be useful for mass screening of anti-HTLV-I antibodies. 相似文献
25.
26.
27.
Norbert T. Sandor Attila Brassai Attila Pliskas Balazs Lendvai 《Brain research bulletin》1995,36(5):483-486
The effect of the nitric oxide synthase inhibitor N-nitro-
-arginine methyl ester (L-NAME) on the basal and stimulation-evoked release of dopamine (DA) and acetylcholine (ACh) was investigated in rat striatum. The experiments were carried out in isolated superfused striatal slices, loaded with either [3H]-dopamine or [3H]-choline.We have found that L-NAME reduced the elecrical field stimulation-evoked release of DA, while its enantiomer N-nitro-D-arginine methyl ester (D-NAME) was ineffective. In the presence of the nitric oxide (NO) precursor
-arginine L-NAME failed to influence DA release. Furthermore, treatment with the N-methyl-
-aspartate (NMDA) receptor antagonist MK-801 completely reversed the effect of L-NAME on striatal DA release. In contrast, L-NAME had no effect on either the basal or the stimulation-evoked ACh release in any experimental conditions studied.Our data indicate that endogenously produced NO is involved in the modulation of striatal DA, but not in ACh release. Furthermore, it seems likely that the modulatory effect of NO is linked to activation of presynaptic NMDA receptors located on the striatal dopaminergic nerve terminals. 相似文献
28.
In order to find out anti-platelet activating factor (PAF) from natural resources, Korean medicinal plants used for the treatments
of peripheral circulation disorders were tested for their possible protective effects on PAF-induced anaphylactic shock. From
the above screening, the methanol extract ofGentiana scabra showed a potent antagonistic activity against PAF. Water suspension of the extract was partitioned with CH2Cl2 and EtOAc, successively. The EtOAc fraction which showed the highest activity was chromatographed on silica gel to yield
6 fractions. From the fraction which showed higher PAF-antagonistic activity than the other fractions, compound1 was isolated by recrystallization. On the basis of spectral data, compound1 was identified as 2-hydroxy-3-methoxybenzoic acid glucose ester. The compound prevented the mice from the PAF-induced death
at a dose of 300 μg/mouse. 相似文献
29.
H. Kushida T. Hiramoto H. Satoh M. Endoh 《Naunyn-Schmiedeberg's archives of pharmacology》1988,337(2):169-176
Summary The phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) was used to examine the hypothesis that phosphoinositide turnover is involved in the regulation of myocardial contractility mediated by stimulation of alpha-adrenoceptors in the mammalian cardiac muscle. Exposure of the isolated rabbit papillary muscle electrically driven at a rate of 1 Hz at a temperature of 37°C to TPA in concentrations of 10–1000 nmol/l for 30 min did not affect the basal force of contraction. The concentration-response curve for the positive inotropic effect of (–)-phenylephrine mediated by stimulation of alpha-adrenoceptors in the presence of (±)-bupranolol (100 nmol/1) was shifted to the right and downward by TPA in concentrations of 30–1000 nmol/l, while the effect of (–)-phenylephrine mediated by stimulation of beta-adrenoceptors in the presence of prazosin (100 nmol/l) was not decreased, but slightly enhanced by exposure of the muscle to relatively low concentrations of TPA (10–100 nmol/l). Incubation of the membrane fraction isolated from the rabbit ventricular muscle with TPA in vitro under the same condition as employed in the physiological experiments decreased the specific binding of [3H]prazosin but not that of [3H]CGP-12177, while the non-tumor promoting phorbol ester, PDD, was ineffective. These results indicate that activation of protein kinase C by TPA does not mimic the positive inotropic effect of catecholamines mediated by activation of myocardial alpha-adrenoceptors. on the other hand, the specific interaction of alpha-adrenoceptor-mediated processes with TPA in the rabbit papillary muscle is in line with the view that the facilitation of phosphoinositide turnover and subsequent activation of protein kinase C may play a certain role in the coupling of alpha-adrenoceptor occupation by agonists to the process leading to the positive inotropic action.
Send offprint requests to M. Endoh 相似文献
30.
Rosenberg Leonard S. Hostetler Cheryl K. Wagenknecht Dietmar M. Aunet Diane A. 《Pharmaceutical research》1988,5(8):514-517
Esmolol hydrochloride degrades in aqueous solutions by the hydrolysis of a labile aliphatic carboxy-ester group. The products are methanol and ASL-8123. The resulting aliphatic carboxylic acid moiety (ASL-8123) has a pK of 4.80, which is within 1 pH unit of the pH of the formulation. ASL-8123 therefore acts as a secondary buffer and minimizes the change in pH due to degradation. Equations are presented to calculate the change in the pH when the primary degradation product acts as a secondary buffer. This information can be used in the development of a parenteral product to predict, a priori, the concentration of buffer necessary for optimal pH maintenance. This knowledge can reduce the number of formulation screens required to determine the necessary buffer capacity for optimal drug stability. 相似文献