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   10360篇
  免费   825篇
  国内免费   3篇
  2023年   47篇
  2022年   119篇
  2021年   255篇
  2020年   159篇
  2019年   224篇
  2018年   254篇
  2017年   226篇
  2016年   363篇
  2015年   563篇
  2014年   566篇
  2013年   825篇
  2012年   911篇
  2011年   840篇
  2010年   525篇
  2009年   442篇
  2008年   637篇
  2007年   658篇
  2006年   573篇
  2005年   476篇
  2004年   438篇
  2003年   459篇
  2002年   405篇
  2001年   91篇
  2000年   53篇
  1999年   91篇
  1998年   99篇
  1997年   83篇
  1996年   67篇
  1995年   50篇
  1994年   65篇
  1993年   72篇
  1992年   48篇
  1991年   40篇
  1990年   33篇
  1989年   26篇
  1988年   32篇
  1987年   28篇
  1986年   28篇
  1985年   31篇
  1984年   28篇
  1983年   25篇
  1982年   22篇
  1981年   21篇
  1979年   15篇
  1978年   20篇
  1977年   13篇
  1976年   13篇
  1975年   13篇
  1973年   16篇
  1972年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The celiac disease (CD) is an inflammatory condition characterized by injury to the lining of the small-intestine on exposure to the gluten of wheat, barley and rye. The involvement of gluten in the CD syndrome has been studied in detail in bread wheat, where a set of “toxic” and “immunogenic” peptides has been defined. For wheat diploid species, information on CD epitopes is poor. In the present paper, we have adopted a genomic approach in order to understand the potential CD danger represented by storage proteins in diploid wheat and sequenced a sufficiently large number of cDNA clones related to storage protein genes of Triticum monococcum. Four bona fide toxic peptides and 13 immunogenic peptides were found. All the classes of storage proteins were shown to contain harmful sequences. The major conclusion is that einkorn has the full potential to induce the CD syndrome, as already evident for polyploid wheats. In addition, a complete overview of the storage protein gene arsenal in T. monococcum is provided, including a full-length HMW x-type sequence and two partial HMW y-type sequences. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
2.
3.
4.
5.
Approximately 10% of all cancers, but a higher proportion of sarcomas, use the recombination-based alternative lengthening of telomeres (ALT) to maintain telomeres. Two RecQ helicase genes, BLM and WRN, play important roles in homologous recombination repair and they have been implicated in telomeric recombination activity, but their precise roles in ALT are unclear. Using analysis of sequence variation present in human telomeres, we found that a WRN– ALT+ cell line lacks the class of complex telomere mutations attributed to inter-telomeric recombination in other ALT+ cell lines. This suggests that WRN facilitates inter-telomeric recombination when there are sequence differences between the donor and recipient molecules or that sister-telomere interactions are suppressed in the presence of WRN and this promotes inter-telomeric recombination. Depleting BLM in the WRN– ALT+ cell line increased the mutation frequency at telomeres and at the MS32 minisatellite, which is a marker of ALT. The absence of complex telomere mutations persisted in BLM-depleted clones, and there was a clear increase in sequence homogenization across the telomere and MS32 repeat arrays. These data indicate that BLM suppresses unequal sister chromatid interactions that result in excessive homogenization at MS32 and at telomeres in ALT+ cells.  相似文献   
6.
7.
Hierarchical down-modulation of hemopoietic growth factor receptors   总被引:31,自引:0,他引:31  
F Walker  N A Nicola  D Metcalf  A W Burgess 《Cell》1985,43(1):269-276
Granulocytes and macrophages can be produced in vitro when progenitor cells from mouse bone marrow are stimulated by any of four distinct colony stimulating factors, Multi-CSF (IL-3), GM-CSF, G-CSF, and M-CSF (CSF-1). At 0 degrees C the four CSFs do not cross-compete for binding to bone marrow cells, indicating that each has a specific cell surface receptor. However, at 21 degrees C or 37 degrees C, Multi-CSF inhibits binding of the other three CSFs and GM-CSF inhibits binding of G-CSF and M-CSF. Rather than competing directly for receptor binding, the binding of Multi-CSF, GM-CSF, or G-CSF to their own receptor induces the down-modulation (and thus activation) of other CSF receptors at 37 degrees C. The pattern and potency of down-modulation activity exhibited by each type of CSF parallels the pattern and potency of its biological activity. We propose a model in which the biological interactions of the four CSFs are explained by their ability to down-modulate and activate lineage-specific receptors.  相似文献   
8.
Loss of the survival motor neuron gene (SMN1) is responsible for spinal muscular atrophy (SMA), the most common inherited cause of infant mortality. Even though the SMA phenotype is traditionally considered as related to spinal motor neuron loss, it remains debated whether the specific targeting of motor neurons could represent the best therapeutic option for the disease. We here investigated, using stereological quantification methods, the spinal cord and cerebral motor cortex of ∆7 SMA mice during development, to verify extent and selectivity of motor neuron loss. We found progressive post-natal loss of spinal motor neurons, already at pre-symptomatic stages, and a higher vulnerability of motor neurons innervating proximal and axial muscles. Larger motor neurons decreased in the course of disease, either for selective loss or specific developmental impairment. We also found a selective reduction of layer V pyramidal neurons associated with layer V gliosis in the cerebral motor cortex. Our data indicate that in the ∆7 SMA model SMN loss is critical for the spinal cord, particularly for specific motor neuron pools. Neuronal loss, however, is not selective for lower motor neurons. These data further suggest that SMA pathogenesis is likely more complex than previously anticipated. The better knowledge of SMA models might be instrumental in shaping better therapeutic options for affected patients.  相似文献   
9.
10.
Riassunto Nella cornea del ratto, in tutta quella parte del parenchima che è al margine con la sclerotica, esistono due cospicue formazioni a plesso, una vascolare e l'altra nervosa, in stretto reciproco rapporto topografico e verosimilmente anche funzionale.Il plesso nervoso è formato da fibre di varia provenienza, mieliniche ed amieliniche, fra loro mescolate ed anastomizzate, soprattutto mediante la rete diffusa alla quale danno origine.È molto probabile che a queste due formazioni, vascolare e nervosa, non sia riservato il solo compito di assicurare la nutrizione della cornea; ma penso che esse non siano estranee al meccanismo regolatore dell'umore acqueo.
Zusammenfassung Der Verfasser hat mit der Bielschowsky-Grosschen Methode und vor allem mit der Schwarzreaktion von Golgi in Epymis norv. die angehäufte Zahl von Nerven studiert, die im Zusammenhang mit dem Hornhautrand stehen und von denen weder die Topographie noch ihre Bedeutung sonderlich bekannt war. Indem der Verfasser diese Methoden mit der Injektion des Blutgefäßsystems verband, hat er festgestellt, daß der plexiforme Nervenapparat enge topographische und funktionelle Beziehungen zu dem sich ringförmig in der gleichen Zone erstreckenden Gefäßplexus hat.Der Verfasser legt außerdem klar, daß dieser vasculonervöse Plexus zur Hornhaut und nicht zu anderen Bildungen gehört. Er schließt ferner, daß diesem angesichts seiner großen Entwicklung eine bemerkenswertere Aufgabe zukommt als jene, lediglich die Ernährung der Hornhaut zu sichern und daß er ein Teil des sinnreichen Regulationsmechanismus des Kammerwassers sei.
  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