全文获取类型
收费全文 | 12181篇 |
免费 | 736篇 |
国内免费 | 6篇 |
出版年
2023年 | 106篇 |
2022年 | 112篇 |
2021年 | 223篇 |
2020年 | 204篇 |
2019年 | 208篇 |
2018年 | 419篇 |
2017年 | 379篇 |
2016年 | 510篇 |
2015年 | 760篇 |
2014年 | 755篇 |
2013年 | 914篇 |
2012年 | 1091篇 |
2011年 | 946篇 |
2010年 | 618篇 |
2009年 | 419篇 |
2008年 | 740篇 |
2007年 | 662篇 |
2006年 | 610篇 |
2005年 | 530篇 |
2004年 | 459篇 |
2003年 | 412篇 |
2002年 | 385篇 |
2001年 | 172篇 |
2000年 | 159篇 |
1999年 | 111篇 |
1998年 | 82篇 |
1997年 | 41篇 |
1996年 | 59篇 |
1995年 | 58篇 |
1994年 | 33篇 |
1993年 | 42篇 |
1992年 | 74篇 |
1991年 | 59篇 |
1990年 | 52篇 |
1989年 | 38篇 |
1988年 | 41篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 49篇 |
1984年 | 37篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1981年 | 23篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 22篇 |
1977年 | 22篇 |
1975年 | 16篇 |
1974年 | 15篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
952.
Sahún I Gallego X Gratacòs M Murtra P Trullás R Maldonado R Estivill X Dierssen M 《Amino acids》2007,33(4):677-688
Summary. Sensitivity to pharmacological challenges has been reported in patients with panic disorder. We have previously validated
transgenic mice overexpressing the neurotrophin-3 (NT-3) receptor, TrkC (TgNTRK3), as an engineered murine model of panic
disorder. We could determine that TgNTRK3 mice presented increased cellularity in brain regions, such as the locus ceruleus,
that are important neural substrates for the expression of anxiety in severe anxiety states. Here, we investigated the sensitivity
to induce anxiety and panic-related symptoms by sodium lactate and the effects of various drugs (the α2-adrenoceptor antagonist,
yohimbine and the adenosine antagonist, caffeine), in TgNTRK3 mice. We found enhanced panicogenic sensitivity to sodium lactate
and an increased intensity and a differential pattern of Fos expression after the administration of yohimbine or caffeine
in TgNTRK3. Our findings validate the relevance of the NT-3/TrkC system to pathological anxiety and raise the possibility
that a specific set of fear-related pathways involved in the processing of anxiety-related information may be differentially
activated in panic disorder. 相似文献
953.
Mineralization process during acellular cementogenesis in rat molars: a histochemical and immunohistochemical study using fresh-frozen sections 总被引:2,自引:2,他引:0
Yamamoto T Domon T Takahashi S Anjuman KA Fukushima C Wakita M 《Histochemistry and cell biology》2007,127(3):303-311
This study was designed to detect tissue non-specific alkaline phosphatase (TNSALP) by Azo-dye staining, calcium by glyoxal
bis (2-hydroxyanil) (GBHA) staining, bone sialoprotein (BSP) and osteopontin (OPN) by immunoperoxidase staining in developing
rat molars, and also to discuss the mineralization process during acellular cementogenesis. To restrain a reduction in histochemical
and immunohistochemical reactions, fresh-frozen undemineralized sections were prepared. Where the epithelial sheath was intact,
TNSALP reaction was observed in the dental follicle, but not in the epithelial sheath. With the onset of dentin mineralization,
the BSP- and OPN-immunoreactive, initial cementum layer appeared. At this point, cementoblasts had shown intense TNSALP reaction
and GBHA reactive particles (=calcium-GBHA complex) appeared on the root surface. With further development, the reaction of
TNSALP and GBHA became weak on the root surface. Previous studies have shown that the initial cementum is fibril-poor and
that matrix vesicles and calciferous spherules appear on the root surface only during the initial cementogenesis. The findings
mentioned above suggest that: during the initial cementogenesis, cementoblasts release matrix vesicles which result in calciferous
spherules, corresponding to the GBHA reactive particles. The calciferous spherules trigger the mineralization of the initial
cementum. After principal fiber attachment, mineralization advances along collagen fibrils without matrix vesicles. 相似文献
954.
955.
The widespread use and abuse of antibiotics as therapeutic agents has produced a major challenge for bacteria, leading to the selection and spread of antibiotic resistant variants. However, antibiotics do not seem to be mere selectors of these variants. Here we show that the fluoroquinolone antibiotic ciprofloxacin, an inhibitor of type II DNA topoisomerases, stimulates intrachromosomal recombination of DNA sequences. The stimulation of recombination between divergent sequences occurs via either the RecBCD or RecFOR pathways and is, surprisingly, independent of SOS induction. Additionally, this stimulation also occurs in a hyperrecombinogenic mismatch repair mutS mutant. It is worth noting that ciprofloxacin also stimulates the conjugational recombination of an antibiotic resistance gene. Finally, we demonstrate that Escherichia coli is able to recover from treatments with recombination-stimulating concentrations of the antibiotic. Thus, fluoroquinolones can increase genetic variation by the stimulation of the recombinogenic capability of treated bacteria (via an SOS-independent mechanism) and consequently may favour the acquisition, evolution and spread of antibiotic resistance determinants. 相似文献
956.
A new species of Neopetitia San Martín, 2003 is described from intertidal and shallow subtidal soft-bottom stations on the eastern and western coast of Tenerife, Canary
Islands. The new species is characterized by the presence in males of a modified acicular chaeta in chaetiger 11. A discussion
of known species of the genus is presented. 相似文献
957.
Blanco G Lemus JA Grande J Gangoso L Grande JM Donázar JA Arroyo B Frías O Hiraldo F 《Environmental microbiology》2007,9(7):1738-1749
The impact on wildlife health of the increase in the use of antimicrobial agents with the intensification of livestock production remains unknown. The composition, richness and prevalence of cloacal microflora as well as bacterial resistance to antibiotics in nestlings and full-grown Egyptian vultures Neophron percnopterus were assessed in four areas of Spain in which the degree of farming intensification differs. Differences in diet composition, especially the role of stabled livestock carrion, appear to govern the similarities of bacterial flora composition among continental populations, while the insular vulture population (Fuerteventura, Canary Islands) showed differences attributed to isolation. Evidence of a positive relationship between the consumption of stabled livestock carrion and bacterial resistance to multiple antibiotics was found. Bacterial resistance was high for semisynthetic penicillins and enrofloxacin, especially in the area with the most intensive stabled livestock production. The pattern of antibiotic resistance was similar for the different bacterial species within each area. Bacterial resistance to antibiotics may be determined by resistance of bacteria present in the livestock meat remains that constituted the food of this species, as indicated by the fact that resistance to each antibiotic was correlated in Escherichia coli isolated from swine carrion and Egyptian vulture nestlings. In addition, resistance in normal faecal bacteria (present in the microflora of both livestock and vultures) was higher than in Staphylococcus epidermidis, a species indicator of the transient flora acquired presumably through the consumption of wild rabbits. Potential negative effects of the use of antimicrobials in livestock farming included the direct ingestion of these drug residues and the effects of bacterial antibiotic resistance on the health of scavengers. 相似文献
958.
Background
Allosteric communications are vital for cellular signaling. Here we explore a relationship between protein architectural organization and shortcuts in signaling pathways. 相似文献959.
960.
Sylvia Kamphuis Kolbrún Hrafnkelsdóttir Mark R Klein Wilco de Jager Margje H Haverkamp Jolanda HM van Bilsen Salvatore Albani Wietse Kuis Marca HM Wauben Berent J Prakken 《Arthritis research & therapy》2007,8(6):R178
Juvenile idiopathic arthritis (JIA) is a heterogeneous autoimmune disease characterized by chronic joint inflammation. Knowing
which antigens drive the autoreactive T-cell response in JIA is crucial for the understanding of disease pathogenesis and
additionally may provide targets for antigen-specific immune therapy. In this study, we tested 9 self-peptides derived from
joint-related autoantigens for T-cell recognition (T-cell proliferative responses and cytokine production) in 36 JIA patients
and 15 healthy controls. Positive T-cell proliferative responses (stimulation index ≥2) to one or more peptides were detected
in peripheral blood mononuclear cells (PBMC) of 69% of JIA patients irrespective of major histocompatibility complex (MHC)
genotype. The peptides derived from aggrecan, fibrillin, and matrix metalloproteinase (MMP)-3 yielded the highest frequency
of T-cell proliferative responses in JIA patients. In both the oligoarticular and polyarticular subtypes of JIA, the aggrecan
peptide induced T-cell proliferative responses that were inversely related with disease duration. The fibrillin peptide, to
our knowledge, is the first identified autoantigen that is primarily recognized in polyarticular JIA patients. Finally, the
epitope derived from MMP-3 elicited immune responses in both subtypes of JIA and in healthy controls. Cytokine production
in short-term peptide-specific T-cell lines revealed production of interferon-γ (aggrecan/MMP-3) and interleukin (IL)-17 (aggrecan)
and inhibition of IL-10 production (aggrecan). Here, we have identified a triplet of self-epitopes, each with distinct patterns
of T-cell recognition in JIA patients. Additional experiments need to be performed to explore their qualities and role in
disease pathogenesis in further detail. 相似文献