全文获取类型
收费全文 | 22972篇 |
免费 | 1889篇 |
国内免费 | 837篇 |
专业分类
耳鼻咽喉 | 91篇 |
儿科学 | 232篇 |
妇产科学 | 314篇 |
基础医学 | 1879篇 |
口腔科学 | 289篇 |
临床医学 | 1385篇 |
内科学 | 2305篇 |
皮肤病学 | 213篇 |
神经病学 | 871篇 |
特种医学 | 1322篇 |
外国民族医学 | 4篇 |
外科学 | 645篇 |
综合类 | 3694篇 |
预防医学 | 1490篇 |
眼科学 | 391篇 |
药学 | 6812篇 |
13篇 | |
中国医学 | 2272篇 |
肿瘤学 | 1476篇 |
出版年
2024年 | 53篇 |
2023年 | 288篇 |
2022年 | 810篇 |
2021年 | 990篇 |
2020年 | 746篇 |
2019年 | 641篇 |
2018年 | 593篇 |
2017年 | 694篇 |
2016年 | 752篇 |
2015年 | 826篇 |
2014年 | 1288篇 |
2013年 | 1383篇 |
2012年 | 1456篇 |
2011年 | 1487篇 |
2010年 | 1266篇 |
2009年 | 971篇 |
2008年 | 1124篇 |
2007年 | 1212篇 |
2006年 | 1037篇 |
2005年 | 948篇 |
2004年 | 823篇 |
2003年 | 740篇 |
2002年 | 615篇 |
2001年 | 544篇 |
2000年 | 504篇 |
1999年 | 374篇 |
1998年 | 314篇 |
1997年 | 305篇 |
1996年 | 243篇 |
1995年 | 223篇 |
1994年 | 234篇 |
1993年 | 166篇 |
1992年 | 197篇 |
1991年 | 247篇 |
1990年 | 224篇 |
1989年 | 148篇 |
1988年 | 163篇 |
1987年 | 129篇 |
1986年 | 112篇 |
1985年 | 170篇 |
1984年 | 168篇 |
1983年 | 141篇 |
1982年 | 96篇 |
1981年 | 68篇 |
1980年 | 59篇 |
1979年 | 47篇 |
1978年 | 30篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
化学药合成过程中水分残留不利于反应的进行,还影响药物及制剂的稳定性、理化性质、溶出及药理作用等,因此水分几乎是大多数药物合成中的必测项目,通过有效除水严格控制反应体系中水分的含量至关重要。本文综述了水分的存在形式,常见除水剂和脱水剂的种类、作用原理与除水能力,以及在药物合成的应用,为药物合成反应中水分的去除提供参考。 相似文献
12.
目的观察清热解毒液(中药制剂)雾化吸入对防治留置胃管致咽喉部疼痛、痰多等不适的效果。方法将80例需要留置胃管的胃肠减压的病人随机分为对照组和观察组各40例。对照组按常规的方法进行护理,观察组在常规护理的基础上加用20毫升清热解毒液雾化吸入,每日2次,持续到拔除胃管。结果观察组病人的咽喉部痰量明显比对照组少(χ2=9.0383,P<0.005);观察组病人咽喉部疼痛明显比对照组少而且轻(χ2=19.5267,P<0.005),时间还推后。结论清热解毒液雾化吸入能有效预防及减轻留置胃管致咽喉部的疼痛、咽燥、痰多等不适。 相似文献
13.
As a consequence of the time-varying magnetic field induced by eddy currents, frequency drifting occurs when the sampling window of localized spectroscopy continuously shifts. The frequency drifting and the concomitant phase variations can severely affect spectroscopy results when data are acquired with multiple echo times (TEs), such as in the measurement of glutamate (Glu) concentration using the TE-averaged method. Specifically, the averaged spectra are further broadened and distorted in the presence of residual eddy currents, and editing of the coupled spins of Glu C4 protons is affected, resulting in errors in the measured relative intensity ratio. Postacquisition correction using unsuppressed water as reference can effectively minimize this detrimental effect, as manifested by the significantly enhanced signal intensity. Also, it is demonstrated that the methyl signals of creatine (Cr) at 3.0 ppm and choline (Cho) at 3.2 ppm can be used as internal references in finding frequency and phase disparities between different TEs. 相似文献
14.
By substituting the saturated vapour phase tension of the pure normal hydrocarbons described by the Clausius-Clapeyron law into the accepted expression of the specific retention volume (Vg,T), a theoretically coherent and relatively simple mathematical evidence of the elution behaviour of the homologous members has been deduced. It gives exponential retention time dependence on carbon number for isothermal, and nearly equidistant (i.e., approximately linear retention-time dependence on carbon number) elution for linear temperature programmed gas chromatographic runs. The final equations are in close correlation with the experimental results. Special emphasis is placed on the fact that a good approximation—not strict physical laws—have been found. 相似文献
15.
16.
目的:研究水杨醛-N′-(2-呋喃硫羰基)腙铜配合物(CSFC)在兔体内的药物动力学。方法:10只家兔静脉注射CSFC5mg·kg-1,用反相HPLC法测定血清药物浓度。结果:CSFC的血药浓度-时间曲线符合二室开放模型,主要药动学参数为:T12α=3.4±1.7min,T12β=65.5±14.6min,K12=0.1183±0.0669min-1,K21=0.0228±0.0065min-1,K10=0.1202±0.0407min-1,V0=0.305±0.184L·kg-1,CL=1.896±0.470L·kg-1·h-1,AUC=170.1±57.0mg·min-1·L-1。结论:CSFC在兔体内分布迅速而广泛,消除也较快。家兔静注5mg·kg-1,可维持抗结核杆菌有效血浓度6h。 相似文献
17.
Carlo Bertucci Enrico Domenici Piero Salvadori 《Journal of pharmaceutical and biomedical analysis》1990,8(8-12):843-846
The application of a circular dichroism (c.d.) detection system in HPLC using a chiral stationary phase is presented. The simultaneous measurement of the absorbance and c.d. signal allows the evaluation of the anisotropy factor (g = Δ/) and thus the determination of the enantiomeric excess (e.e.) of the eluates. When this detection system is used in preparative chiral chromatography the collection of the enantiomeric fractions can be readily optimized. 相似文献
18.
The present study examined the influences of dopamine (DA) receptor stimulation on enkephalin (Met5-enkephalin; ME) and tachykinin (substance P; SP) systems of basal ganglia of Sprague-Dawley rats, lesioned as neonates with 6-hydroxydopamine (6-OHDA). It has been proposed that the neonatal 6-OHDA-lesioned rat could serve as a model for the DA deficiency and self-injurious behavior (SIB) observed in the childhood neurological disorder. Lesch-Nyhan syndrome. In agreement with earlier work, the present study found that the neonatal 6-OHDA treatment at 3 days of age, reduced DA and caused an increase in ME and a decrease in SP content in the striatum and substantia nigra, when tested as adults. Administration of the DA precursor, L-dihydroxyphenylalanine (L-DOPA), to lesioned animals, induced SIB; increased DA and DOPAC levels; produced a greater decrease (-64%) in SP levels in the striatum and substantia nigra than was observed with lesion alone (-28%). The L-DOPA-induced decrease in SP levels and the SIB observed in the lesioned animals were blocked by pretreatment with the D1 receptor antagonist, SCH-23390. Moreover, administration of the D1 receptor agonist, SKF-38393, but not the D2 agonist, LY-171555, to lesioned animals mimicked the L-DOPA responses in all respects, except that the agonists did not alter DA or DOPAC levels. None of the DA agonists or antagonists treatments affected lesion-induced increase in ME levels in the striatum. These results indicate for the first time, that SIB precipitated by DA agonists in neonatal dopaminergic denervated animals, is associated with a marked and selective decrease in SP in the striatonigral SP neurons. This process has two components: (a) a retarded development of the SP system due to neonatal dopaminergic denervation: and (b) a depletion of the remaining SP, presumably by enhanced release due to D1 DA receptor-mediated activation of striatonigral SP neurons. 相似文献
19.
Depressed levels of circulating menaquinones in patients with osteoporotic fractures of the spine and femoral neck 总被引:3,自引:0,他引:3
S.J. Hodges M.J. Pilkington T.C.B. Stamp A. Catterall M.J. Shearer L. Bitensky J. Chayen 《BONE》1991,12(6):387-389
Vitamin K1 functions in the conversion of glutamate residues, present in certain bone peptides, into the putatively active γ-carboxyglutamate form. We have shown previously that the circulating levels of vitamin K1 are depressed in osteoporotic patients. However, it is known that menaquinones (vitamin K2:MK) may be more effective than vitamin K1 in this conversion of the inactive to active form of glutamate residues. A procedure for measuring such menaquinones has now demonstrated a marked deficiency of MK-7 and MK-8 in patients with osteoporotic fractures. It is suggested that estimates of circulating levels of K1, MK-7, and MK-8 might provide a biochemical risk marker of osteoporotic fractures. 相似文献
20.
大鼠脑组织单胺类递质及其代谢产物的检测方法研究 总被引:13,自引:0,他引:13
目的 :研究大鼠脑组织中单胺类递质及其代谢产物的高效液相反相离子对色谱测定法。方法 :采用LiChrosorbC18,10 μm色谱柱 ,流动相为甲醇 :水 (4 0 :60 ) ,含 0 .0 2 8g LEDTANa2 ,0 .15g LSDS ,0 .2ml LH2 SO4(pH 2 .5~ 3 ) ,荧光检测波长 :λEX=2 85 ,λEM=3 3 3。结果 :对 87只大鼠脑组织中 4种单胺类递质及其代谢产物的含量进行了同时测定 ,高香草酸 (HVA) 2 .5 0~ 40 .0 μg ml、去甲肾上腺素 (NE) 0 .0 1~ 0 .5 0 μg ml、多巴胺 (DA)0 .0 5~ 1.0 0 μg ml、5 羟色胺 (5 HT) 0 .0 2 5~ 0 .5 0 μg ml,峰面积与其含量呈良好的线性关系。 结论 :该法操作简便、快速、准确 ,为组织中单胺类递质及其代谢产物检测的一种理想方法 ,并适用于临床相关研究。 相似文献