全文获取类型
收费全文 | 663535篇 |
免费 | 314980篇 |
国内免费 | 54904篇 |
专业分类
耳鼻咽喉 | 6827篇 |
儿科学 | 11330篇 |
妇产科学 | 4968篇 |
基础医学 | 113354篇 |
口腔科学 | 10781篇 |
临床医学 | 107314篇 |
内科学 | 127111篇 |
皮肤病学 | 9313篇 |
神经病学 | 32211篇 |
特种医学 | 25986篇 |
外国民族医学 | 6篇 |
外科学 | 76719篇 |
综合类 | 169990篇 |
现状与发展 | 106篇 |
一般理论 | 3篇 |
预防医学 | 90052篇 |
眼科学 | 23713篇 |
药学 | 107060篇 |
735篇 | |
中国医学 | 81977篇 |
肿瘤学 | 33863篇 |
出版年
2023年 | 7601篇 |
2022年 | 17269篇 |
2021年 | 20943篇 |
2020年 | 20374篇 |
2019年 | 18584篇 |
2018年 | 19590篇 |
2017年 | 23445篇 |
2016年 | 19229篇 |
2015年 | 27544篇 |
2014年 | 32588篇 |
2013年 | 38178篇 |
2012年 | 51174篇 |
2011年 | 55247篇 |
2010年 | 54125篇 |
2009年 | 58283篇 |
2008年 | 47123篇 |
2007年 | 42869篇 |
2006年 | 37900篇 |
2005年 | 31132篇 |
2004年 | 25765篇 |
2003年 | 22314篇 |
2002年 | 19717篇 |
2001年 | 20707篇 |
2000年 | 14048篇 |
1999年 | 14700篇 |
1998年 | 14264篇 |
1997年 | 14077篇 |
1996年 | 15170篇 |
1995年 | 15264篇 |
1994年 | 15008篇 |
1993年 | 13646篇 |
1992年 | 12841篇 |
1991年 | 12225篇 |
1990年 | 11187篇 |
1989年 | 11020篇 |
1988年 | 10577篇 |
1987年 | 9913篇 |
1986年 | 9434篇 |
1985年 | 8482篇 |
1984年 | 6546篇 |
1983年 | 6551篇 |
1982年 | 7608篇 |
1981年 | 7145篇 |
1980年 | 6809篇 |
1979年 | 6643篇 |
1978年 | 5820篇 |
1977年 | 6125篇 |
1976年 | 5753篇 |
1975年 | 5484篇 |
1974年 | 5034篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Biochemical, immunological, and immunocytochemical evidence for the association of chalcone synthase with endoplasmic reticulum membranes. 总被引:5,自引:0,他引:5
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G Hrazdina A M Zobel H C Hoch 《Proceedings of the National Academy of Sciences of the United States of America》1987,84(24):8966-8970
Chalcone synthase [naringenin-chalcone synthase; malonyl-CoA:4-coumaroyl-CoA malonyltransferase (cyclizing), E.C. 2.3.1.74], the key enzyme of flavonoid pathways that was believed to be soluble, has been localized on ribosome-bearing endoplasmic reticulum membranes in the epidermis of buckwheat (Fagopyrum esculentum M.) hypocotyls. Enzyme activity measurement and immunoblots of buckwheat hypocotyl homogenates that were fractionated on linear sucrose density gradients and developed with a specific chalcone synthase antibody and a 20-nm ImmunoGold conjugate showed the presence of chalcone synthase in fractions enriched in endoplasmic reticulum membranes. The presence of chalcone synthase on these membranes was not caused by nonspecific adsorption or entrapment of proteins. Immunocytochemical investigations with both a 5-nm and a 20-nm ImmunoGold conjugate showed that chalcone synthase was associated with the cytoplasmic face of rough (ribosome bearing) endoplasmic reticulum membranes. Plasma membrane, nucleus, plastids, mitochondria, golgi, and the tonoplast were not labeled. These data are consistent with our earlier described model suggesting that the synthesis of phenylpropanoids and flavonoids takes place partially or fully on membrane-associated enzyme complexes. 相似文献
992.
993.
994.
Physiological analysis of simple rapid movements in patients with cerebellar deficits. 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Journal of neurology, neurosurgery, and psychiatry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M Hallett A Berardelli J Matheson J Rothwell C D Marsden 《Journal of neurology, neurosurgery, and psychiatry》1991,54(2):124-133
Patients with cerebellar deficits made elbow flexion movements as rapidly as possible for three different angular distances. Electromyographic activity of biceps and triceps and the kinematics of the movements were analysed. Results were compared with those of normal subjects making both rapid and slow movements. In the patients, the first agonist burst of the biceps was frequently prolonged regardless of the distance or speed of the movement. The most striking kinematic abnormality was prolonged acceleration time. The pattern of acceleration time exceeding deceleration time was common in patients but uncommon in normal subjects. The best kinematic correlate of the duration of the first agonist burst was acceleration time. Altered production of appropriate acceleration may therefore be an important abnormality in cerebellar dysfunction for attempted rapid voluntary movements. 相似文献
995.
J. Duteil FA Rambert AM Pointeau P. Mangiameli and E. Assous 《Fundamental & clinical pharmacology》1991,5(8):695-708
The potential antidepressant effect of flerobuterol (dl-(fluoro-2 phenyl)-1 t-butylamino-2 ethanol), a new drug related to beta-adrenoceptor agonists, was evaluated and compared with imipramine and salbutamol using classical psychopharmacological tests in mice. Like imipramine and salbutamol, flerobuterol (0.5-32 mg kg-1, ip) fully prevented apomorphine (16 mg kg-1, sc)- and partly reversed reserpine- and oxotremorine-induced hypothermia. At higher doses (16-32 mg kg-1), flerobuterol enhanced the toxic effects of yohimbine. Unlike imipramine, flerobuterol and salbutamol did not reduce immobility duration in the behavioural despair test. Salbutamol and flerobuterol decreased locomotor activity. Flerobuterol did not induce mydriasis, did not prevent oxotremorine-induced tremors or salivary and lacrimal gland secretion and did not reduce reserpine-induced palpebral ptosis. Propranolol (8 mg kg-1, ip) but not alpha-methyl-paratyrosine (75 mg kg-1, ip) prevented the flerobuterol-induced antagonism of apomorphine-induced hypothermia. Our results suggest that flerobuterol demonstrates potential antidepressant activity, which could be related to beta-adrenoceptor activation in mice. 相似文献
996.
A single myocardial stretch or decreased systolic fiber shortening stimulates the expression of heat shock protein 70 in the isolated, erythrocyte-perfused rabbit heart. 总被引:9,自引:3,他引:6
下载免费PDF全文
![点击此处可从《The Journal of clinical investigation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A A Knowlton F R Eberli P Brecher G M Romo A Owen C S Apstein 《The Journal of clinical investigation》1991,88(6):2018-2025
The regulation of heat shock protein 70 (HSP 70) expression was examined in the isolated, red blood cell-perfused rabbit heart by Northern and Western blot analysis. In the isovolumic (balloon in left ventricle), isolated perfused heart, HSP 70 mRNA was increased threefold after 30 min and sevenfold at 2 and 4 h compared to normal, nonperfused hearts. To further elucidate the etiology of the increase in HSP 70 mRNA, the effects of decreased systolic shortening (isovolumic heart) and of a single ventricular stretch were examined. Perfusion without the application of a stretch or the presence of a balloon resulted in no increase in HSP 70 mRNA; while a single stretch resulted in a threefold increase in HSP 70 mRNA. These changes were accompanied by an increase in HSP 70 protein by Western blot analysis. To elucidate the signalling mechanism mediating the increase in HSP 70, hearts were perfused with H7, a protein kinase C inhibitor. H7 did not prevent the induction of HSP 70. These results indicate that initiation of expression of myocardial HSP 70 can be stimulated by a single myocardial stretch or by prevention of systolic shortening. These mechanisms may contribute to the rapid expression of HSP 70 after coronary occlusion when dyskinesis, reduced systolic shortening, and increased diastolic segment length all occur. 相似文献
997.
经腹及经阴道B超监测卵泡发育的评估 总被引:3,自引:0,他引:3
应用经腹及经阴道B超对68名不孕症妇女,139个月经周期进行卵泡发育及排卵监测。卵泡检出率TAUS为90.6%,TVUS为98.0%,显著高于前者,P<0.05。成熟卵泡特征影象(卵丘等)在TVUS显象率较高。TVUS监测卵泡发育更实用可靠。 相似文献
998.
原位杂交法检测BP1基因在乳腺癌组织中表达 总被引:3,自引:0,他引:3
目的探讨BP1同源盒基因在乳腺癌中的表达及其与临床病理指标的关系。方法收集165例乳腺癌临床和病理资料,采用原位杂交法检测BP1的表达,同时用二步法进行ER、p53、PCNA、bcl2、cerbB2免疫组化染色。结果BP1基因表达率为67.88%,免疫组化:ER70.30%、p5349.09%、PCNA74.55%、bcl253.33%、cerbB275.52%。BP1与bcl2具有相关性(P<0.01),且均与ER相关(P<0.05),与p53呈负相关(P<0.05)。BP1与PCNA、cerbB2、患者年龄、组织学类型、淋巴结转移等无相关性。结论BP1可能通过某种非依赖p53基因调控机制,与bcl2、ER协同抑制肿瘤细胞的凋亡而参与乳腺癌的发生。 相似文献
999.
1000.