全文获取类型
收费全文 | 11245篇 |
免费 | 621篇 |
国内免费 | 413篇 |
专业分类
耳鼻咽喉 | 87篇 |
儿科学 | 108篇 |
妇产科学 | 58篇 |
基础医学 | 1896篇 |
口腔科学 | 184篇 |
临床医学 | 576篇 |
内科学 | 1980篇 |
皮肤病学 | 42篇 |
神经病学 | 1802篇 |
特种医学 | 178篇 |
外科学 | 607篇 |
综合类 | 1210篇 |
预防医学 | 368篇 |
眼科学 | 94篇 |
药学 | 2575篇 |
3篇 | |
中国医学 | 380篇 |
肿瘤学 | 131篇 |
出版年
2024年 | 16篇 |
2023年 | 91篇 |
2022年 | 170篇 |
2021年 | 295篇 |
2020年 | 195篇 |
2019年 | 200篇 |
2018年 | 198篇 |
2017年 | 226篇 |
2016年 | 271篇 |
2015年 | 321篇 |
2014年 | 493篇 |
2013年 | 694篇 |
2012年 | 554篇 |
2011年 | 648篇 |
2010年 | 576篇 |
2009年 | 577篇 |
2008年 | 629篇 |
2007年 | 639篇 |
2006年 | 484篇 |
2005年 | 483篇 |
2004年 | 471篇 |
2003年 | 448篇 |
2002年 | 324篇 |
2001年 | 301篇 |
2000年 | 270篇 |
1999年 | 259篇 |
1998年 | 290篇 |
1997年 | 301篇 |
1996年 | 233篇 |
1995年 | 184篇 |
1994年 | 205篇 |
1993年 | 167篇 |
1992年 | 167篇 |
1991年 | 152篇 |
1990年 | 110篇 |
1989年 | 122篇 |
1988年 | 94篇 |
1987年 | 99篇 |
1986年 | 89篇 |
1985年 | 68篇 |
1984年 | 42篇 |
1983年 | 36篇 |
1982年 | 29篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Human glioma cells obtained from established cell lines (Tp-276MG, Tp-301MG, Tp-378MG, Tp-483MG and U-251MG) were analyzed for the presence of ion channels with the tight-seal voltage clamp technique. The current-voltage relation revealed a marked inward rectification at hyperpolarizing voltages, due to the presence of inward rectifying K-channels in cells from all studied cell lines. These channels were conducting when the membrane potential was more negative than the K-equilibrium potential. The slope conductance for the inward K-currents (gKi) was affected both by [K+]i and [K+]0. gKi was proportional to [K+]0 raised to 0.35 or 0.50, of which the larger value was measured in the presence of low [K+]i (25mM). The rectification was not significantly different in cells perfused with Mg-free EDTA-buffered internal solution. Tl+ was 3.5 times more permaant than K+. gki was blocked by Cs+ (1 mM) in a voltage-dependent way (more effective in the hyperpolarized membrane), and by Na+ (154 mM) depending on voltage and time. From measurements of unitary current events in membrane patches (outside out or cell attached) the conductance of the single inward rectifying channel was estimated to be 27 ± 7 pS. This type of ion channel may be important for K-uptake by glial cells and hence for the K-homeostasis in the brain. 相似文献
42.
甲基黄酮醇胺盐酸盐对异丙肾上腺素正性频率作用的影响 总被引:2,自引:0,他引:2
本文比较了甲基黄酮醇胺盐酸盐(MFOA)、普萘洛尔(Pro)、维拉帕米(Ver)对异丙肾上腺素(Iso)所致兔离体右心房正性频率作用的影响。Pro使Iso累积浓度反应曲线平行右移,不抑制最大反应,属于典型的竞争性抑制剂,其pA2=8.43;MFOA和Ver使Iso量效曲线向下右移,抑制最大反应,为非竞争性拮抗。MFOA(2×10~(-5)M)和Ver(2×10~(-7)M)分别使最大反应下降19.28%和48.57%,其pD'2值分别为4.07±0.14、6.68±0.15。结果表明MFOA的作用不同于Pro,和Ver相似。 相似文献
43.
培养Wistar大鼠乳鼠的心室肌细胞,向培养基中分别加入浓度为1.56μg/ml至50μg/ml的大豆皂甙,可使心肌细胞群落的自发性搏动呈剂量依赖性抑制。洗脱大豆皂甙或向培养基中再加入10μg/ml肾上腺素均能使自发性搏动恢复。向培养基中加入大豆皂甙5μg/ml使心肌细胞动作电位的波幅、波宽、超射、最大舒张电位、阈电位、最大除极速度等各电参数立即减小。Ca~(2+)80μg/ml能使动作电位的抑制逆转。上述结果表明大豆皂甙对培养的鼠心肌细胞具有钙通道阻滞用。 相似文献
44.
Voltage-Gated calcium channels and nonvoltage-gated calcium uptake pathways in the rat incisor odontoblast plasma membrane 总被引:4,自引:1,他引:3
Odontoblasts participate actively in the transport and accumulation of Ca2+ ions to the mineralization front during dentinogenesis. These cells are known to carry membrane-bound ATP-driven pumps and
Na+/Ca2+ antiports for Ca2+ extrusion, but little is known about Ca2+ influx mechanisms into these cells. It has been shown that the administration of Ca2+ channel blockers in vivo strongly impairs Ca2+ uptake in the mineral phase during dentinogenesis in the rat; the present in vitro study is aimed at further elucidating
odontoblast Ca2+ uptake mechanisms. Dissected rat incisor odontoblasts exhibited a pronounced fluorescence when incubated with a fluorescently-labeled
(STBodipy) dihydropyridine, which is specific for voltage-gated Ca2+ channels of the L-type, and this binding was competitively abolished by nifedipine. As assayed by fluorescence spectrometry,
odontoblast Ca2+ uptake was enhanced by the agonistic dihydropyridine BAYK-8644 (5 μM) as well as by plasma membrane depolarization in a high
K+ (120 mM) medium. The Ca2+ uptake after depolarization was impaired by nifedipine (5 μM). When treated with the Ca2+-ATPase inhibitor cyclopiazonic acid (CPA; 10 μM), a nonvoltage-gated uptake of 45Ca2+ was identified. This uptake was not influenced by nifedipine (20 μM) but was impaired by lanthanum ions (200 μM). A nonvoltage-gated
uptake of Mn2+ into CPA-treated cells could be traced using the fura-2 quenching technique. This CPA-induced Ca2+ flux was not caused by an alteration of the plasma membrane potential, as assayed with di-8-ANEPPS. The results demonstrate
that Ca2+ flux into dentinogenically active odontoblasts occurs through voltage-gated Ca2+ channels of the L-type and by nonvoltage-gated, agonist-sensitive Ca2+ uptake pathways.
Received: 6 November 1995 / Accepted: 21 February 1996 相似文献
45.
Angela Ameri 《Naunyn-Schmiedeberg's archives of pharmacology》1997,355(2):273-280
The effects of the Aconitum alkaloid 3-acetylaconitine on neuronal activity were investigated in the slice preparation and on cultivated neurons of rat
hippocampus by extracellular and patch-clamp recordings, respectively. 3-Acetylaconitine (0.01–1 μM) diminished the orthodromic
and antidromic population spike in a concentration-dependent manner. The inhibitory action of the drug was preceded by a transiently
enhanced excitability. The latency of onset of the inhibition was accelerated by increased stimulation frequency, whereas
recovery during washout of the alkaloid was accelerated by decreased stimulation frequency. Moreover, the inhibitory effect
of 3-acetylaconitine was evaluated in two different models of epileptiform activity induced either by blockade of GABA receptors
by bicuculline (10 μM) or by a nominal Mg2+-free bathing medium. In accordance with the activity-dependent mode of action, this compound abolished the synaptically evoked
population spikes in the presence of bicuculline or nominal Mg2+-free bathing medium, respectively. Whole-cell patch-clamp recordings revealed an interaction of 3-acetylaconitine with the
voltage-dependent sodium channel. At a concentration of 1 μM, 3-acetylaconitine did not affect the peak amplitude of the sodium
current, but shifted the current-voltage relationship in the hyperpolarized direction such that sodium currents were already
activated at the resting potential.
Received: 22 July 1996 / Accepted: 14 October 1996 相似文献
46.
吡那地尔对体外培养大鼠大脑皮层神经细胞缺氧缺糖损伤的保护作用 总被引:1,自引:0,他引:1
目的 :探讨ATP敏感性K+ 通道 (KATP)开放剂吡那地尔 (pinacidil,Pin)对缺氧缺糖再复氧损伤大鼠大脑皮层神经细胞的保护作用。方法 :体外培养大鼠大脑皮层神经细胞 ,细胞培养至 10d ,建立神经细胞缺氧缺糖损伤模型 ,观察Pin及KATP阻断剂格列苯脲对缺氧缺糖不同时间 ,再复氧 2 4h后细胞死亡率、丙二醛 (MDA)含量、超氧化物歧化酶 (SOD)活力的影响。结果 :缺氧缺糖、再复氧后大鼠的神经细胞死亡率均显著升高、MDA生成增多、SOD的活力下降 ,Pin干预后 ,细胞死亡率下降、MDA生成减少、SOD的活力升高 ;格列苯脲能拮抗Pin这种保护作用。结论 :Pin对缺氧缺糖损伤神经细胞具有保护作用 ,并与拮抗氧自由基有关 相似文献
47.
Joel A. Black Ruth Westenbroek Bruce R. Ransom William A. Catterall Stephen G. Waxman 《Glia》1994,12(3):219-227
The expression of sodium channel α-subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immunocytochemical methods with antibodies generated against conserved and subtype-specific sequences of the sodium channel. In adult rat spinal cord, astrocytes within the dorsal and ventral funiculi were immunolabelled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within these spinal cord white matter tracts were immunostained with antibody SP11-II, which recognizes sodium channel type II. Antibodies SP11-I and SP32-III, which are directed against subtype-specific sequences in sodium channel types I and III, respectively, did not label astrocytes in the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detectable labelling of cells within the optic nerve was observed with antibodies SP11-I, SP11-II, and SP32-III. These observations demonstrate that sodium channel II is expressed by astrocytes in spinal cord white matter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes. 相似文献
48.
L.I. Daikhin M. Urbakh 《Journal of electroanalytical chemistry (Lausanne, Switzerland)》2003,560(1):59-67
We develop a theory of the double layer at electrolyte–electrolyte interfaces taking in to account the microscopic structure of the interfacial region. This includes a “mixed boundary layer” where the overlapping of two space-charge regions occurs, and the effects of ion association and adsorption at the interface. Theoretical results are in good agreement with experimental data obtained for various organic solvents and electrolytes. The theory suggests a framework for the treatment of the capacitance data and establishes a relationship between experimental results and the microscopic structure of interfaces between two immiscible electrolyte solutions (ITIES). 相似文献
49.
刺五加叶皂甙单体Sb对培养大鼠心肌细胞动作电位的影响 总被引:1,自引:0,他引:1
本研究中所用的刺五加叶皂甙单体Sb(50、200μg/mL),使培养的wistar大鼠心肌细胞动作电位的波幅、波宽、阈电位、最大舒张电位、超射、最大除极速度及复极(10%、50%、90%)水平的动作电位波宽一致减小。Ca2+80μg/mL能使之反转,Sb作用与尼莫地平作用相似。上述结果表明Sb具有钙通道阻滞作用。 相似文献
50.
用低蛋白饮食方法建立豚鼠胆色素结石模型,共设对照、致石、维生素C修复、丹参修复和对照修复等5组,规定时间内处死动物,用放射免疫、固相酶联免疫、生物化学等方法检测肝细胞内环—磷酸腺甙(cAMP)、环—磷酸鸟嘌呤(cGMP)、钙调素(CaM)、钙,三磷酸腺甙酶(Ca2+-ATPase)、磷酸化酶a等水平。致石组豚鼠肝脏细胞内cAMP和磷酸化酶a升高,而cGMP,CaM和Ca2+-ATPase下降,表明肝细胞钙稳态呈失调状态。维生素C和丹参可调整肝细胞的上述改变,说明维生素C和丹参具有维持肝细胞钙稳态的作用。 相似文献