全文获取类型
收费全文 | 9289篇 |
免费 | 414篇 |
国内免费 | 269篇 |
专业分类
耳鼻咽喉 | 65篇 |
儿科学 | 122篇 |
妇产科学 | 67篇 |
基础医学 | 1617篇 |
口腔科学 | 622篇 |
临床医学 | 727篇 |
内科学 | 1020篇 |
皮肤病学 | 100篇 |
神经病学 | 533篇 |
特种医学 | 144篇 |
外科学 | 1068篇 |
综合类 | 732篇 |
现状与发展 | 1篇 |
预防医学 | 396篇 |
眼科学 | 53篇 |
药学 | 2155篇 |
4篇 | |
中国医学 | 315篇 |
肿瘤学 | 231篇 |
出版年
2023年 | 76篇 |
2022年 | 190篇 |
2021年 | 266篇 |
2020年 | 212篇 |
2019年 | 276篇 |
2018年 | 288篇 |
2017年 | 231篇 |
2016年 | 205篇 |
2015年 | 210篇 |
2014年 | 612篇 |
2013年 | 555篇 |
2012年 | 545篇 |
2011年 | 622篇 |
2010年 | 506篇 |
2009年 | 463篇 |
2008年 | 411篇 |
2007年 | 411篇 |
2006年 | 397篇 |
2005年 | 370篇 |
2004年 | 320篇 |
2003年 | 245篇 |
2002年 | 236篇 |
2001年 | 150篇 |
2000年 | 120篇 |
1999年 | 126篇 |
1998年 | 102篇 |
1997年 | 92篇 |
1996年 | 97篇 |
1995年 | 70篇 |
1994年 | 64篇 |
1993年 | 43篇 |
1992年 | 54篇 |
1991年 | 44篇 |
1990年 | 47篇 |
1989年 | 50篇 |
1988年 | 42篇 |
1987年 | 41篇 |
1986年 | 33篇 |
1985年 | 249篇 |
1984年 | 167篇 |
1983年 | 169篇 |
1982年 | 146篇 |
1981年 | 109篇 |
1980年 | 89篇 |
1979年 | 80篇 |
1978年 | 34篇 |
1977年 | 28篇 |
1976年 | 23篇 |
1975年 | 17篇 |
1973年 | 15篇 |
排序方式: 共有9972条查询结果,搜索用时 10 毫秒
101.
目的 采用廉价的CaCO_3和CaHPO_4·2H_2O作为原料,在激光的作用下通过反应制备HA生物陶瓷涂层。方法 利用X射线衍射仪和电子探针分析仪对涂层进行相分析、组织观察和成分分析。结果CaCO_3和CaHPO_4·2H_2O按20:80的质量比混合时,在功率为600W、扫描速度为3.5mm/s的激光作用下可一步合成钙磷生物陶瓷涂层。结论 在一定实验条件下,CaCO_3和CaHPO_4·2H_2O可合成组织致密、结合状态良好的钙磷生物陶瓷涂层。 相似文献
102.
Anselm Frick Ivan Durasin Mechtild Neuweg 《Pflügers Archiv : European journal of physiology》1986,406(4):387-391
Clearance experiments have been performed to study the effects of saline infusion on the reabsorption of inorganic sulfate (SO4) at endogenous levels. Adult female Sprague-Dawley rats on a standard diet were used. Both intact and thyroparathyroidectomized (TPTX) animals were infused with a 130 mmol/l sodium chloride solution at a low (0.15 ml/min) and a high (0.375 ml/min) rate. This increase of the infusion rate decreased the reabsorption of SO4 in both groups of animals significantly. The fractional excretion of SO4 in theintact rats increased from 9.9±5.6 to 18.4±3.6% (mean values±SD,p<0.001) and in theTPTX rats from 5.3±2.5 to 22.4±6.3% (p<0.001). It is concluded that endogenous parathyroid hormone has no major effect on the saline-induced inhibition of reabsorption of SO4.This work was supported by a grant from the Deutsche Forschungsgemeinschaft (Fr 239/9-1) 相似文献
103.
The ontogeny of lymphocytes expressing J chain in the cytoplasm (J+) was studied in pig foetuses by the immunofluorescent technique. Peripheral blood lymphocytes were the first J+ cells in prenatal life. The spleen and lymph nodes contained J+ cells in the last days of gestation. J+ cells were found in the lamina propria of the gut and some glands of conventional but not of germ-free piglets. J chain was not detected on or in cell membranes at any developmental stage. 相似文献
104.
Francesco Tedesco Maria A. Villa Peter Densen Girolamo Sirchia 《Molecular immunology》1983,20(1):47-51
Structural and functional studies were performed on a dysfunctional C8 molecule present in the serum of two siblings and an unrelated individual. The C8 in these three sera exhibited a pattern of partial immunologic identity with C8 in normal serum but was devoid of functional activity. The C8 was immunoprecipitated from the three sera and from a control serum with an antihuman C8 antiserum and analyzed by SDS-PAGE using highly purified human C8 as a reference. A selective absence of a band of 62,000 mol. wt was observed in the immunoprecipitates from the sera containing dysfunctional C8. Experiments performed with the purified α-γ and γ subunits showed that the hemolytic activity of the C8 deficient sera could be reconstituted by the addition of the β chain but not the α-γ dimer. Binding of the dysfunctional C8 to C was excluded by the following observations: (1) EAC 1–7 treated with the C8 deficient sera and then washed could not be lysed after the addition of the β subunit and C9; and (2) the abnormal molecules did not interfere with the consumption of normal C8 by the soluble complex SC5b-7. 相似文献
105.
Nika Adham Laurence A. Borden Lee E. Schechter Eric L. Gustafson Tamara L. Cochran Pierrre J.-J. Vaysse Richard L. Weinshank Theresa A. Branchek 《Naunyn-Schmiedeberg's archives of pharmacology》1993,348(6):566-575
We recently described the cloning of a fifth member of the 5-hydroxytryptamine (5-HT)1 (serotonin1) receptor class that inhibits adenylyl cyclase, namely the human 5-HT1F receptor (Adham et al. 1993 a). In the present study we have examined in greater detail the functional coupling of the 5-HT1F receptor in two different cell lines, NIH-3T3 and LM(tk–) fibroblasts (receptor densities of 1.7 and 4.4 pmol/mg protein, respectively). The maximal inhibitory response elicited by 5-HT was significantly greater in NIH-3T3 as compared to LM(tk–) cells, whereas the EC50 values were comparable.To investigate the relationship between receptor occupancy and inhibition of cAMP accumulation mediated by 5-HT1F receptors in NIH-3T3 cells (and hence the degree of receptor reserve), we used the irreversible receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The half-maximal response required only about 10% receptor occupancy, consistent with a receptor reserve of 90% (88±2.1%, n = 4) for 5-HT-induced inhibition of FSCA. Despite the presence of such a high degree of receptor reserve, a range of intrinsic activities was displayed by structurally diverse classes of compounds. For example, sumatriptan and lysergol were as efficacious as 5-HT itself and thus acted as full agonists, whereas metergoline and 1-NP behaved as partial agonists and as shown previously (Adham et al. 1993a), methiothepin was a silent antagonist (Kb = 438 nM).We have also investigated activation of additional signal transduction pathways by the 5-HT1F receptor and found that the responses differ in the two cell lines with respect to stimulation of phospholipase C. For example, in NIH-3T3 cells no elevation of inositol phosphates (IP) of [Ca2+]i was observed even at very high agonist concentrations (100 M). In contrast, in LM(tk–) cells concentrations of 5-HT as low as 10 nM induced stimulation of IP and a rapid increase of [Ca2+]i. The 5-HT1F receptor failed to alter arachidonic acid release in either cell line.The maximal increase in IP accumulation in LM(tk–) cells was modest, averaging about 100% above basal. The increases of IP and [Ca2+]i required 5-HT concentrations less than one order of magnitude greater than those inhibiting FSCA (EC50 = 17, 55 and 8 nM, respectively), and both responses were blocked by 100 M methiothepin. All three responses (cAMP, IP, and [Ca2+]i) were sensitive to pertussis toxin pre-treatment, suggesting the involvement of Gi/Go protein(s) in these signal transduction pathways. [Ca2+]i was also elevated by sumatriptan, which may provide a mechanism by which this drug causes constriction of the vasculature. In conclusion, these data indicate that the human 5-HT1F receptor can couple to multiple effectors, and that this coupling is cell-type dependent.Abbreviations FSCA
forskolin-stimulated cAMP accumulation
- [Ca2+]
intracellular free calcium concentration
- AA
arachidonic acid
- EEDQ
N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline
- CHO
chinese hamster ovary cell
- LM(tk–)
mouse fibroblast cell
- Bmax
maximal binding site density
- Ki
apparent dissociation constant obtained from competition binding studies
- G protein
guanine nucleotide-binding protein
- HBS
HEPES-buffered saline
- IP
inositol phosphates
- IP3
inositol 1,4,5 trisphosphate
- PLC
phospholipase C
- Kb
antagonist dissociation constant
- Kd
equilibrium dissociation constant
- N-1F-6
stable NIH-3T3 cells expressing the cloned 5-HT1F receptor
- L-1F-3
stable LM(tk–) cells expressing the cloned 5-HT1F receptor
- PTX
pertussis toxin
- BSA
bovine serum albumin
- METH
methiothepin
- SUMA
sumatriptan
- 5-MeO-DMT
5-methoxy-N,N-dimethyltryptamine
- 1-NP
1-(1-napthyl)piperazine
- 5-CT
5-carboxyamidotryptamine
Correspondence to: N. Adham at the above address 相似文献
106.
Kurata M 《Journal of anesthesia》1993,7(3):325-333
31P and 23Na nuclear magnetic resonance (NMR) spectroscopy was employed to study the dynamic changes in intracellular high-energy phosphates and sodium during 15min of forebrain ischemia and recirculation in in vivo rat brain. In the presence of the shift reagent Dysprosium triethylenetetramine-N,N,N,N,N,N-hexaacetic and [Dy(TTHA)], the sodium peak separated into two peaks, unshifted and shifted. During 15min of ischemia, the unshifted sodium peak decreased and the shifted sodium peak increased. With recirculation, the unshifted and the shifted sodium peaks returned to the preischemia level within 10min, but the shifted one increased during 30–60min. Intracellular high-energy phosphates and intracellular pH (pHi) decreased during 15min of ischemia and returned to the preischemia levels within 20min of recirculation. We conclude that the decrease in unshifted sodium peak during ischemia is due to the decrease in subarachnoid sodium and the cellular influx of interstitial sodium would be minimum. The increase in shifted sodium peak during ischemia is considered to be due to the dilatation of cerebral blood vessels and the increase in interstitial sodium which was transported from subarachnoid space.(Kurata M: 31P and 23Na nuclear magnetic resonance study on forebrain ischemia in rats with shift reagent Dy(TTHA). J Anesth 7: 325–333, 1993) 相似文献
107.
注射用克林霉素磷酸酯的稳定性研究 总被引:2,自引:0,他引:2
目的:对影响注射用克林霉素磷酸酯稳定性的各种因素进行考察,方法:采用高效液相色谱法测定注射用克林霉素磷酸酯的稳定性。结果:温度对本制剂稳定性有影响,对光稳定性较好。结论:本制剂应于凉暗干燥处贮存。 相似文献
108.
109.
国产磷酸克林霉素治疗细菌性感染安全性及有效性临床观察 总被引:2,自引:0,他引:2
磷酸克林霉素是克林霉素的酯化衍生物,供静脉用药。本品为林可霉素类抗菌素,主要用于治疗革兰氏阳性菌及厌氧菌感染。本项研究用国产磷酸克林霉素与进口磷酸克林霉素随机对照及开放治疗急性细菌性感染52例,两药均每日静点2次,每次300mg,疗程7~14天。随机对照试验中,20例国产磷酸克林霉素与20例进口磷酸克林霉素总有效率分别为75.0%与80.0%,细菌清除率分别为85.7%与93.8%,不良反应发性率 相似文献
110.
烟酰胺腺嘌呤二核苷酸磷酸氧化酶是心血管系统中活性氧(reactive oxygen species,ROS)的主要来源,它包
括7种亚型并分别表达在不同的心血管细胞及其细胞器中,参与调节细胞增殖、迁移、分化、凋亡、衰老和炎症反应
等多种活动,其衍生的ROS参与高血压、动脉粥样硬化、糖尿病血管病变、心肌梗死后心室重构等多种心血管疾病
的病理过程。 相似文献