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   6903篇
  免费   668篇
  国内免费   2篇
  2022年   48篇
  2021年   99篇
  2020年   53篇
  2019年   75篇
  2018年   112篇
  2017年   90篇
  2016年   152篇
  2015年   251篇
  2014年   323篇
  2013年   351篇
  2012年   456篇
  2011年   425篇
  2010年   269篇
  2009年   224篇
  2008年   342篇
  2007年   383篇
  2006年   323篇
  2005年   341篇
  2004年   283篇
  2003年   302篇
  2002年   272篇
  2001年   125篇
  2000年   126篇
  1999年   112篇
  1998年   94篇
  1997年   75篇
  1996年   68篇
  1995年   52篇
  1994年   49篇
  1993年   51篇
  1992年   67篇
  1991年   76篇
  1990年   78篇
  1989年   67篇
  1988年   83篇
  1987年   67篇
  1986年   59篇
  1985年   74篇
  1984年   51篇
  1983年   38篇
  1982年   45篇
  1981年   45篇
  1980年   41篇
  1979年   48篇
  1978年   41篇
  1977年   59篇
  1976年   43篇
  1974年   49篇
  1973年   47篇
  1972年   40篇
排序方式: 共有7573条查询结果,搜索用时 31 毫秒
1.
Georg Söderbom 《Ethnos》2013,78(1-2):95-100
Current debates over the concept of culture are examined, especially with regard to the relationship of culture to bounded collectivities, human nature, and individuality; present‐day views are seen against the background of back‐and‐forth swings in the history of anthropological thought. Recent theorizing about cultural acquisition is also considered.  相似文献   
2.
The review focuses on the multiple separating regimes that offers the free flow electrophoresis technique: free flow zone electrophoresis, isoelectric focusing, isotachophoresis, free flow step electrophoresis. Also, the feasibility to apply either interval or continuous flow electrophoresis is evaluated. The free flow zone electrophoresis regime is generally selected for the separation of cells, organelles and membranes while the other regimes find their largest fields of applications in the purification of proteins and peptides. The latter regimes present the highest resolution efficiency. Therefore, a large part of this review is devoted to the applicabilities of these different regimes to the purification of organelles and membrane vesicles at the preparative scale. Recent developments, both in instrumentation and procedures, are described. The major achievements in plant membrane fractionation obtained with free flow electrophoresis are outlined. The related procedures are both analytical and preparative: they separate tonoplast and plasma membrane simultaneously from the same homogenate, they discriminate for one type of membrane vesicles of opposite orientation, and process large quantities of membrane material by reason of the continuous flow mode. Recent advances using electromigration techniques that permit confirmation of the dynamic state of membranes, characterisation of complex membrane-dependent functions and discovery of new membrane-localised activities are presented.  相似文献   
3.
4.
Georg Mosebach 《Planta》1945,34(2):249-292
Ohne ZusammenfassungMit 16 Textabbildungen.Vor seinem letzten Abschied legte mir mein Mann die Manuskripte zweier Arbeiten in die Hand mit der Bitte, wenn nötig, statt seiner für ihre Veröffentlichung zu sorgen. Die erste Arbeit (Über die Polarisierung derEquiselum-Spore durch das Licht, Planta 33, 1943) war so gut wie druckfertig und wurde von den Herren ProfessorenJ. Buder, Breslau, undL. Jost, Heidelberg, durchgesehen. Herr ProfessorBuder hatte auch die Freundlichkeit, die Korrekturen zu lesen. Die zweite, hier vorliegende Arbeit war vonGeorg Mosebach in dieser Fassung noch nicht für die Veröffentlichung bestimmt; trotzdem ist sie nun doch in der ursprünglichen Form erschienen — abgesehen von wenigen oder unbedeutenden Änderungen, die Herr ProfessorBuder und Herr ProfessorRuhland, Leipzig, die Güte hatten vorzunehmen. Herrn Professor Dr.J. Buder, Herrn Professor Dr.L. Jost und Herrn Professor Dr.W. Ruhland spreche ich auch an dieser Stelle meinen Dank aus für alle selbstlose Hilfe, die mir bei meiner Aufgabe zuteil wurde; für viele gute. Ratschläge und alle Mühe, die mit der Durchsicht einer Arbeit verbunden ist.Erna Mosebach, Dr. phil. nat.  相似文献   
5.
Summary The rôle of several structural and functional factors and of concentration on the cross-reactions of 28 human plasma proteins with their homologues in animal blood was investigated. The Immunological Evolution Group (IEG) system was employed for this purpose as described earlier (Bauer, 1970 a). No interaction of structural factors was detected, while an influence of serum level of the different proteins could not be ruled out with certainty.At least in the case of the 4 immunoglobulins and the 3 complement factors, included in the IEG-system, protein function and evolution show some degree of correlation, indicating the influence of function on molecular evolution in the case of these plasma proteins.  相似文献   
6.

Backgound  

It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT).  相似文献   
7.
In this study, 18 partly commercially available samples of rock salt from Austria, Germany, Pakistan, Poland, Switzerland, and Ukraine were investigated with respect to their content of trace elements using instrumental neutron activation analysis. Elements detected were Al, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, La, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, and Zn, some of them only in individual cases. An estimation of the bioavailability of these trace elements was performed by dissolving an equivalent of the sodium chloride samples in diluted hydrochloric acid (simulating stomach acid), filtering off the insoluble components, and analyzing the evaporated filtrate. It could be shown that in most cases bioactive trace elements like Fe can be found in rock salt in the form of almost insoluble compounds and are therefore not significantly bioavailable, whereas thorium, for example, was partly bioavailable in two cases. A significant contribution to the recommended daily intake of metal trace elements by using rock salt for nutrition can be excluded.  相似文献   
8.
New World bats have recently been discovered to harbor influenza A virus (FLUAV)-related viruses, termed bat-associated influenza A-like viruses (batFLUAV). The internal proteins of batFLUAV are functional in mammalian cells. In contrast, no biological functionality could be demonstrated for the surface proteins, hemagglutinin (HA)-like (HAL) and neuraminidase (NA)-like (NAL), and these proteins need to be replaced by their human counterparts to allow spread of batFLUAV in human cells. Here, we employed rhabdoviral vectors to study the role of HAL and NAL in viral entry. Vectors pseudotyped with batFLUAV-HAL and -NAL were able to enter bat cells but not cells from other mammalian species. Host cell entry was mediated by HAL and was dependent on prior proteolytic activation of HAL and endosomal low pH. In contrast, sialic acids were dispensable for HAL-driven entry. Finally, the type II transmembrane serine protease TMPRSS2 was able to activate HAL for cell entry indicating that batFLUAV can utilize human proteases for HAL activation. Collectively, these results identify viral and cellular factors governing host cell entry driven by batFLUAV surface proteins. They suggest that the absence of a functional receptor precludes entry of batFLUAV into human cells while other prerequisites for entry, HAL activation and protonation, are met in target cells of human origin.  相似文献   
9.
The importance of functional parameters for evaluating the severity of low back pain is gaining clinical recognition, with evidence suggesting that the angular velocity of lordosis is critical for identification of musculoskeletal deficits. However, there is a lack of data regarding the range of functional kinematics (RoKs), particularly which include the changing shape and curvature of the spine. We address this deficit by characterising the angular velocity of lordosis throughout the thoracolumbar spine according to age and gender. The velocity of lumbar back shape changes was measured using Epionics SPINE during maximum flexion and extension activities in 429 asymptomatic volunteers. The difference between maximum positive and negative velocities represented the RoKs. The mean RoKs for flexion decreased with age; 114°/s (20–35 years), 100°/s (36–50 years) and 83°/s (51–75 years). For extension, the corresponding mean RoKs were 73°/s, 57°/s and 47°/s. ANCOVA analyses revealed that age and gender had the largest influence on the RoKs (p<0.05). The Epionics SPINE system allows the rapid assessment of functional kinematics in the lumbar spine. The results of this study now serve as normative data for comparison to patients with spinal pathology or after surgical treatment.  相似文献   
10.
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