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   39602篇
  免费   126篇
  国内免费   157篇
系统科学   254篇
丛书文集   540篇
教育与普及   70篇
理论与方法论   155篇
现状及发展   16601篇
研究方法   1658篇
综合类   19795篇
自然研究   812篇
  2013年   377篇
  2012年   602篇
  2011年   1419篇
  2010年   266篇
  2008年   693篇
  2007年   888篇
  2006年   816篇
  2005年   833篇
  2004年   874篇
  2003年   763篇
  2002年   800篇
  2001年   1292篇
  2000年   1240篇
  1999年   772篇
  1992年   733篇
  1991年   562篇
  1990年   628篇
  1989年   613篇
  1988年   572篇
  1987年   572篇
  1986年   631篇
  1985年   780篇
  1984年   572篇
  1983年   507篇
  1982年   436篇
  1981年   440篇
  1980年   514篇
  1979年   1246篇
  1978年   956篇
  1977年   924篇
  1976年   754篇
  1975年   773篇
  1974年   1150篇
  1973年   931篇
  1972年   1003篇
  1971年   1129篇
  1970年   1523篇
  1969年   1149篇
  1968年   1070篇
  1967年   1025篇
  1966年   993篇
  1965年   709篇
  1964年   212篇
  1959年   370篇
  1958年   689篇
  1957年   474篇
  1956年   373篇
  1955年   352篇
  1954年   376篇
  1948年   258篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
721.
Interleukin (IL)-33 is a recently described pro-inflammatory cytokine. Here we demonstrate IL-33 as a regulator of functional osteoclasts (OCs) from human CD14+ monocytes. IL-33 stimulates formation of tartrate-resistant acid phosphatase (TRAP)+ multinuclear OCs from monocytes. This action was suppressed by anti-ST2 antibody, suggesting that IL-33 acts through its receptor ST2, but not by the receptor activator of NF-κB ligand (RANKL) decoy, osteoprotegerin, or anti-RANKL antibody. IL-33 stimulated activating phosphorylations of signaling molecules in monocytes that are critical for OC development. These included Syk, phospholipase Cγ2, Gab2, MAP kinases, TAK-1, and NF-κB. IL-33 also enhanced expression of OC differentiation factors including TNF-α receptor-associated factor 6 (TRAF6), nuclear factor of activated T cells cytoplasmic 1, c-Fos, c-Src, cathepsin K, and calcitonin receptor. IL-33 eventually induced bone resorption. This study suggests that the osteoclastogenic property of IL-33 is mediated through TRAF6 as well as the immunoreceptor tyrosine-based activation motif-dependent Syk/PLCγ pathway in human CD14+ monocytes.  相似文献   
722.
723.
Psoriatic arthritis (PsA) is an inflammatory joint disease that is distinct from other chronic arthritides and which is frequently accompanied by psoriasis vulgaris (PsV) and seronegativity for rheumatoid factor. We conducted a genome-wide association study in 609 German individuals with PsA (cases) and 990 controls with replication in 6 European cohorts including a total of 5,488 individuals. We replicated PsA associations at HLA-C and IL12B and identified a new association at TRAF3IP2 (rs13190932, P = 8.56 × 10?1?). TRAF3IP2 was also associated with PsV in a German cohort including 2,040 individuals (rs13190932, P = 1.95 × 10?3). Sequencing of the exons of TRAF3IP2 identified a coding variant (p.Asp10Asn, rs33980500) as the most significantly associated SNP (P = 1.13 × 10?2?, odds ratio = 1.95). Functional assays showed reduced binding of this TRAF3IP2 variant to TRAF6, suggesting altered modulation of immunoregulatory signals through altered TRAF interactions as a new and shared pathway for PsA and PsV.  相似文献   
724.
Burn injury causes an immunosuppression associated with suppressed adaptive immune function. Dendritic cells (DCs) are APCs for which signaling via their Toll-like receptors (TLRs) induces their maturation and activation, which is essential for the adaptive immune response. In this study, we examined if burn injury alters the TLR activity of splenic DCs. After injury, we noticed that DC functions were impaired, characterized by a suppressed capacity to prime naive T cells when triggering the TLR4 signaling cascade using specific ligands (LPS or rHSP60). The observed perturbations on LPS-primed DCs isolated from burned mice exhibited significantly diminished IL-12p40 production and enhanced IL-10 secretion-associated impairment in mitogen-activated protein kinase activation. Interestingly, we observed a decrease of TLR4/MD-2 expression on the CD8α+ DC subset that persisted following LPS stimulation. The altered TLR4 expression on LPS-stimulated CD8α+ DCs was associated with reduced capacity to produce IL-12 after stimulation. Our results suggested that TLR4 reactivity on DCs, especially CD8α+ DCs, is disturbed after burn injury.  相似文献   
725.
The young Hermann Helmholtz, in an 1838 letter home, declared that he always appreciated music much more when he played it for himself. Though a frequent concert-goer, and celebrated for his highly influential 1863 work on the physiological basis of music theory, Die Lehre von den Tonempfindungen, it is likely that Helmholtz's enduring engagement with music began with his initial, personal experience of playing music for himself. I develop this idea, shifting the discussion of Helmholtz's work on sound sensation back to its origins, and examine the role of his material interaction with musical instruments and music itself. In his sound sensation studies, Helmholtz understood sound as an external, physical object. But Helmholtz also conceived of sound in musical terms. Further, Helmholtz's particular musical tastes as well as his deeply personal interaction with musical instruments allowed him to reconcile his conception of sound as physical object with his conception of sound as music. Helmholtz's physiological theory of sound sensation was both the product of and constitutive of how he heard and created sound. I argue that Helmholtz himself was the embodied reconciliation of his physiological theory of sound sensation and his belief that musical aesthetics were historically and culturally contingent.  相似文献   
726.
727.
In 1639–1640 Benedetto Castelli (1577–1643) wrote a treatise on the loadstone which is quite unlike any of its contemporaries. In it are the origins of the notion of elementary magnets sharing a common alignment, the idea that all materials are magnetic in different ways, and the first intimation of the conception of magnetic domains. Castelli did not publish his treatise. Nevertheless his work was noted during his life-time, and may have exerted an influence on the development of magnetic theory in the 17th century. The treatise was published in 1883. Since then, however, it has either been neglected or not appreciated. It deserves being rescued from the neglect of more than three centuries.  相似文献   
728.
729.
We present an analysis, and first full English translation, of a paper by Kant entitled ‘Über die Vulcane im Monde’ (1785). Kant became interested in the question of whether the mountains of the Moon were extinct volcanoes. Stimulated by the work of Herschel, Aepinus, and others, he considered the appearance of the Moon's surface and the possibility of lunar vulcanism. From this, he was led to consider the structures of mountain ranges on the Earth, which he decided were non-volcanic in origin, being produced by eruptions of vapours from the interior of the Earth soon after it formed from an original ‘chaos’. Kant developed his ideas in such a way as to yield a characteristic eighteenth-century ‘theory of the Earth’. We argue that the empirical base of his theory was provided by knowledge of the mountain ranges of Bohemia and Moravia. Analogies based on observations of the Moon further assisted in the construction of the theory. But the reasoning ran in two directions: what was seen on the Moon was construed in terms of what Kant knew of the Earth's topography; and the Earth's topography was presumed to be analogous to that of the Moon, for both the Earth and the Moon (and indeed all heavenly bodies) supposedly had essentially similar origins. Kant's ideas of 1785 are related to his earlier writings of 1754, 1755, and 1756, and also to the lectures on physical geography that he presented at Königsberg.  相似文献   
730.
As the most famous woman scientist of the twentieth century, there has been no shortage of books and articles on the life and career of Marie Curie (1867–1934). Her role as a director of a laboratory-based research school in the new scientific field of radioactivity, a field which embraced both chemistry and physics, however, has never been examined. In recent years, there has been a growing interest in the question of research schools, and Morrell, Ravetz, Geison, and Klosterman, amongst others, have written on this subject. Using, in part, the methodology of Morrell, this paper investigates the role of Marie Curie as a school director in the Paris Faculty in the years 1907–14, examining the work and characteristics of her school and assessing her effectiveness as a director.  相似文献   
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