首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   390041篇
  免费   282828篇
  国内免费   41053篇
耳鼻咽喉   3737篇
儿科学   7213篇
妇产科学   4738篇
基础医学   101621篇
口腔科学   6212篇
临床医学   72606篇
内科学   118320篇
皮肤病学   6578篇
神经病学   28887篇
特种医学   14743篇
外国民族医学   8篇
外科学   53488篇
综合类   73167篇
现状与发展   1篇
一般理论   26篇
预防医学   56872篇
眼科学   21220篇
药学   69344篇
  28篇
中国医学   53668篇
肿瘤学   21445篇
  2021年   5862篇
  2020年   7645篇
  2019年   15040篇
  2018年   17398篇
  2017年   16937篇
  2016年   14865篇
  2015年   15142篇
  2014年   15866篇
  2013年   16972篇
  2012年   19260篇
  2011年   24741篇
  2010年   23712篇
  2009年   29895篇
  2008年   18945篇
  2007年   15067篇
  2006年   14293篇
  2005年   15059篇
  2004年   21540篇
  2003年   19821篇
  2002年   18299篇
  2001年   17599篇
  2000年   11676篇
  1999年   17162篇
  1998年   16664篇
  1997年   16176篇
  1996年   16363篇
  1995年   16355篇
  1994年   16149篇
  1993年   15639篇
  1992年   14901篇
  1991年   13919篇
  1990年   12521篇
  1989年   12089篇
  1988年   11407篇
  1987年   10740篇
  1986年   10175篇
  1985年   8959篇
  1984年   6878篇
  1983年   6783篇
  1982年   7754篇
  1981年   7286篇
  1980年   6938篇
  1979年   6863篇
  1978年   5997篇
  1977年   6283篇
  1976年   5894篇
  1975年   5659篇
  1974年   5207篇
  1973年   4912篇
  1972年   4907篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
1. Bradykinin (100 nM) triggers release of nitric oxide and prostacyclin from both AG07680A and AG04762 bovine cultured aortic endothelial cells. The exposure of these cells to bradykinin is in each case associated with a striking rise in intracellular calcium ion concentration. 2. Exposure of AG07680A cells to 250 nM ionomycin was followed also by a significant release of prostacyclin, whereas 250 nM ionomycin had no capacity to stimulate release of prostacyclin from AG04762 cells. 3. There was a similar concentration-dependent increase in intracellular calcium ion concentration on exposure of AG07680A and AG04762 cells to ionomycin. 4. Exposure of AG04762 cells for 10 min to staurosporine produced a concentration-dependent inhibition (IC50 = 107 +/- 14 nM) in bradykinin-stimulated prostacyclin release. There was no similar inhibitory effect of staurosporine in AG07680A cells. 5. Bradykinin (10 nM) triggered release of nitric oxide from both AG07680A and AG04762 cells, and the effect was not inhibited by 500 nM staurosporine. There was a similar ionomycin-dependent release of nitric oxide from both cell types. 6. These results identify a common pathway for bradykinin-dependent nitric oxide release from both AG07680A and AG04762 cells, involving increases in intracellular calcium ion concentration. In contrast, the bradykinin-dependent release of prostacyclin may involve one of two pathways (involving an increase in intracellular calcium or activation of a staurosporine-sensitive kinase), and the two pathways are selectively exploited in AG07680A and AG04762 cells, respectively.  相似文献   
42.
43.
Summary Contradictory immunohistochemical data have been reported on the localization of N-acetylaspartylglutamate in the rat forebrain, using different carbodiimide fixation protocols and antibody purification methods. In one case, N-acetylaspartylglutamate immunoreactivity was observed in apparent interneurons throughout all allocortical and isocortical regions, suggesting possible colocalization with GABA. In another case, strong immunoreactivity was observed in numerous pyramidal cells in neocortex and hippocampus, suggesting colocalization with glutamate or aspartate. Reconciling these disparate findings is crucial to understanding the role of N-acetylaspartylglutamate in nervous system function. Antibodies to N-acetylaspartylglutamate and a structurally related molecule, N-acetylaspartate, were purified in stages, and their cross-reactivities with protein conjugates of N-acetylaspartylglutamate and N-acetylaspartate were monitored at each stage by solidphase immunoassay. Reduction of the cross-reactivity of the anti-N-acetylaspartylglutamate antibodies to N-acetylaspartateprotein conjugates to about 1% eliminated significant staining of most pyramidal neurons in the rat forebrain. Utilizing highly purified antibodies, the distributions of N-acetylaspartylglutamate and N-acetylaspartate were examined in several major telencephalic and diencephalic regions of the rat, and were found to be distinct. N-acetylaspartylglutamate-immunoreactivity was observed in specific neuronal populations, including many groups thought to use GABA as a neurotransmitter. Among these were the globus pallidus, ventral pallidum, entopeducular nucleus, thalamic reticular nucleus, and scattered non-pyramidal neurons in all layers of isocortex and allocortex. N-acetylaspartate-immunoreactivity was more broadly distributed than N-acetylaspartylglutamate-immunoreactivity in the rat forebrain, appearing strongest in many pyramidal neurons. Although N-acetylaspartate-immunoreactivity was found in most neurons, it exhibited a great range of intensities between different neuronal types.  相似文献   
44.
45.
We report a prevalence study of the best visual acuity in the affected eye of 100 selected patients with herpetic keratitis seen during a two-year period. Sixty-two patients retained an acuity of 6/9 or better without requiring penetrating keratoplasty (PK). The prevalence of reduced visual acuity severe enough to warrant PK was 33%. Patients requiring PK for whom full clinical records were available suffered a mean of 6.8 episodes of keratitis. In this group of patients the vision of 18 fell from 6/6 to 6/60 over a mean period of 8.5 years. Once visual acuity was permanently reduced to 6/12, 78% of patients proceeded to lose vision to 6/60. Unilateral visual impairment occurs in at least a third of patients with severe herpetic keratitis. Once vision falls permanently to 6/12, the long-term prognosis for vision appears to be poor.  相似文献   
46.
47.
Zusammenfassung. Die Infektion mit dem humanen Immundefizienzvirus (HIV) betrifft nicht nur das Immunsystem des menschlichen Organismus, sondern schließt vielmehr eine Reihe weiterer Organsysteme mit ein. Es wird angenommen, dass bei 5-15% der HIV-positiven Patienten kardiale Manifestationen auftreten. Zu den häufigsten HIV-assoziierten kardialen Manifestationen gehören der Perikarderguss und die chronisch aktive, fokale oder diffuse Myokarditis. Endokardiale Manifestationen bei HIV-positiven Patienten treten in Form der infektiösen Endokarditis und der nichtbakteriellen thrombotischen Endokarditis auf. In der Regel weisen HIV-assoziierte kardiale Manifestationen einen langsam progredienten Krankheitsverlauf auf. Komplikationen sind Folge eines langfristig unentdeckten Fortschreitens der Erkrankung, aber auch schnell progredienter Verlaufsformen. Aufgrund der Vielzahl HIV-assoziierter kardialer Manifestationen und deren möglicher Komplikationen ist daher neben der Früherkennung ein effektives diagnostisches und therapeutisches Vorgehen erforderlich. Seit Einführung der Proteaseinhibitoren in den 90er Jahren und der Anwendung der hochaktiven antiretroviralen Kombinationstherapie (HAART) konnten sowohl Mortalität als auch Morbidität der HIV-Infektion deutlich gesenkt werden. Die Auswirkungen der HAART auf das kardiovaskuläre System sind bisher nur in Ansätzen bekannt. Als Nebenwirkungen wurden metabolische Veränderungen in Form von Hyperlipoproteinämie und Insulinresistenz bei einer Vielzahl HIV-positiver Patienten beobachtet. Es kann davon ausgegangen werden, dass durch den Anstieg der kardiovaskulären Risikofaktoren unter der HAART in den nächsten Jahren eine erhöhte Rate kardialer Erkrankungen bei HIV-positiven Patienten auftreten wird. In dem vorliegenden Übersichtsartikel wird ein Überblick über die häufigsten kardialen Erkrankungen bei HIV-Infektionen gegeben. Zusätzlich werden Vorschläge zu Diagnostik und Therapie unterbreitet und eine Einschätzung über Veränderungen der HIV-assoziierten kardialen Manifestationen nach Einführung der HAART vorgenommen. Abstract. The human immunodeficiency virus (HIV) does not only affect the immune system. Other organs including the cardiovascular system are influenced by the HIV as well. Most common HIV-associated cardiac manifestations are pericardial effusion and chronic active, focal or diffuse myocarditis. In addition to peri- and myocardial disease, endocardiac manifestations occur as infective endocarditis and nonbacterial thrombotic endocarditis in HIV-infected patients. Although most of the cardiac manifestations associated with HIV-infection exhibit a slow progression, rapid courses may lead to fatal complications. Early screening of HIV-infected patients will identify the potentially fatal complications of HIV disease and permit efficient treatment. The use of highly active antiretroviral therapy (HAART) significantly reduced the mortality and morbidity of HIV-infected patients. However, the impact that HAART will have on the incidence and prevalence of cardiac complications in HIV-infected patients is still unknown. It can be predicted, that the long-term viral infection and the increase of cardiovascular risk factors by HAART will probably lead to an increased prevalence of HIV-infected individuals with cardiac complications in the next decade. The present review describes the most frequent HIV-associated cardiac manifestations including diagnostic and therapeutic perspectives.  相似文献   
48.
49.
50.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号