全文获取类型
收费全文 | 105340篇 |
免费 | 841篇 |
国内免费 | 909篇 |
专业分类
107090篇 |
出版年
2024年 | 106篇 |
2023年 | 110篇 |
2022年 | 302篇 |
2021年 | 393篇 |
2020年 | 303篇 |
2019年 | 369篇 |
2018年 | 12135篇 |
2017年 | 10872篇 |
2016年 | 7807篇 |
2015年 | 1261篇 |
2014年 | 1073篇 |
2013年 | 1151篇 |
2012年 | 5236篇 |
2011年 | 13725篇 |
2010年 | 12556篇 |
2009年 | 8691篇 |
2008年 | 10447篇 |
2007年 | 11953篇 |
2006年 | 784篇 |
2005年 | 986篇 |
2004年 | 1464篇 |
2003年 | 1406篇 |
2002年 | 1089篇 |
2001年 | 508篇 |
2000年 | 369篇 |
1999年 | 230篇 |
1998年 | 102篇 |
1997年 | 85篇 |
1996年 | 64篇 |
1995年 | 62篇 |
1994年 | 65篇 |
1993年 | 73篇 |
1992年 | 101篇 |
1991年 | 112篇 |
1990年 | 62篇 |
1989年 | 55篇 |
1988年 | 52篇 |
1987年 | 37篇 |
1986年 | 27篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 34篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1977年 | 18篇 |
1975年 | 19篇 |
1972年 | 255篇 |
1971年 | 279篇 |
1970年 | 17篇 |
1962年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
861.
正Dear Editor,Gliomas are the most frequent primary tumors of the central nervous system,accounting for more than 60%of all brain tumors(Wang and Bettegowda,2015).Among them,glioblastoma multiforme(GBM)is the most common aggressive glioma,and the average survival rate remains low(Chen et al.,2015).The standard combination of surgery and radiotherapy or chemotherapy can only extend the progressionfree survival time for 12–18 months,with a high risk of recurrence(Li et al.,2008).In addition,the incidence of GBM 相似文献
862.
863.
Based on 16S rDNA analyses, the primary symbionts of sucking lice were found to form a polyphyletic assemblage of several
distant lineages that have arisen several times within Enterobacteriaceae and at least once within Legionellaceae. Another
independent lineage of endosymbiotic enterobacteria inhabits a sister group of the sucking lice, Rhynchophthirina. The inspection
of 16S rDNA supports the symbiotic nature of the investigated bacteria; they display a typical trait of degenerative processes,
an increased AT content (Adenine–Thymine content) in comparison with free-living bacteria. The calculation of divergence time
between the closest anopluran and rhynchophthirine symbionts further support their independent origin. The results shown here,
together with evidence from other groups, indicate that the significance of primary symbionts for blood-feeding insects should
be reconsidered. 相似文献
864.
Li Zhihui Zhu Peng Huang Hui Pan Ying Han Peng Cui Huanhuan Kang Zhijuan Xun Mai Zhang Yi Liu Saijun Wang Jian Wu Jing 《中国科学:生命科学英文版》2019,62(12):1572-1579
Alport syndrome(AS) is a hereditary progressive nephropathy characterized by hematuria, ultrastructural lesions of the glomerular basement membrane, ocular lesions and sensorineural hearing loss. Germline mutations of COL4 A5 are associated with X-linked AS with an extreme phenotypic heterogeneity. Here, we investigated a Chinese family with Alport syndrome. The proband was a 9-year-old boy with hematuria and proteinuria. Based on the test results of renal biopsy and immunofluorescence,the proband was initially diagnosed as Ig A nephropathy and the treatment was recommended accordingly. Meanwhile, we found that the treatment outcome was poor. Therefore, for proper clinical diagnosis and appropriate treatment, targeted exome-based next-generation sequencing has been undertaken. We identified a novel hemizygous single nucleotide deletion c.1902 del A in COL4 A5 gene. Segregation analysis identified that this novel mutation is co-segregated among the affected family members but absent in unaffected family members. The clinical diagnosis of the proband was revised as AS accompanied by Ig A nephropathy,which has been rarely reported. Our findings demonstrated the significance of the application of Genetic screening, expanded the mutation spectrum of COL4 A5 associated AS patients with atypical renal phenotypes and provided a good lesson to be learned from our detour during the diagnosis. 相似文献
865.
Árpád Kovács Judit Kalász Enikő T. Pásztor Attila Tóth Zoltán Papp Naranjan S. Dhalla Judit Barta 《Molecular and cellular biochemistry》2017,424(1-2):57-67
C1ql-like (C1QL)-1 and -4 proteins are encoded by homologous genes that are highly expressed in brain and adipose tissues. However, functional properties of C1QL proteins outside of the brain and adipocytes remain unknown. Here, we report that the globular domain of C1ql1/Ctrp14 and C1ql4/Ctrp11 proteins directly stimulate the angiogenesis of endothelial cells. In this study, soluble C1ql1/CTRP14 and C1ql4/Ctrp11 proteins, produced in prokaryote expression system, are co-cultured with human umbilical vein endothelium cells (HUVECs), which phenotype is identified with von Willebrand factor antibody. C1ql1/Ctrp14 and C1ql4/Ctrp11 promote the migration and capillary tube formation of HUVECs in a dose-dependent manner. During this process, phosphorylation of c-Raf, MEK1/2, ERK1/2, and p90RSK are activated by C1ql1/Ctrp14 and C1ql4/Ctrp11. MEK1/2 inhibitor, U0126, blocks C1ql1/Ctrp14-, and C1ql4/Ctrp11-induced capillary tube formation and cell migration. Moreover, the immunoreactivity of the receptor of C1QL1-C1QL4, brain-specific angiogenesis inhibitor 3 (BAI3), is detected in HUVECs, suggesting that BAI3 may mediate C1QL1/CTRP14- and C1QL4/CTRP11-induced angiogenesis. Meanwhile, C1ql1/Ctrp14 and C1ql4/Ctrp11 exposure also causes a stimulatory response of angiogenesis in chick yolk sac membrane. These data demonstrate that C1ql1/Ctrp14 and C1ql4/Ctrp11 stimulate the new blood vessel growth by activation of ERK1/2 signal pathway. The proangiogenic activity of C1ql1/Ctrp14 and C1ql4/Ctrp11 provides novel insights into the new opportunities for therapeutic intervention by targeting C1QLs in tumorigenesis, tissue regeneration, and recovery of ischemic heart disease. 相似文献
866.
Rohlfs M 《Oecologia》2008,155(1):161-168
Although still underrepresented in ecological research, competitive interactions between distantly related organisms (so-called
“interkingdom competition”) are expected to be widespread in various ecosystems, with yet unknown consequences for, e.g. trophic
interactions. In the model host–parasitoid system Drosophila melanogaster–Asobara tabida, toxic filamentous fungi have been shown to be serious competitors that critically affect the density-dependent survival
of host Drosophila larvae. This study investigates the extent to which the competing mould Aspergillus niger affects key properties of the well-studied Drosophila–parasitoid system and how the host–parasitoid interaction influences the microbial competitor. In contrast to slightly positive
density-dependent host mortality under mould-free conditions, competing A. niger mediated a strong Allee effect for parasitised larvae, i.e. mortality decreased with increasing larval density. It was found
that the common toxic fungal metabolite kojic acid is not responsible for higher death rates in parasitised larvae. Single
parasitised Drosophila larvae were less harmful to fungal reproduction than unparasitised larvae, but this effect vanished with an increase in larval
density. As predicted from the negative effect of fungi on host survival and thus on parasitoid fitness at low larval densities,
A. tabida females spent less time foraging in fungus-infested patches. Interestingly, even though high host larval densities increased
host survival, parasitoids still reduced their search efforts in fungus-infested patches, indicating a benefit for host larvae
from feeding in the presence of noxious mould. Thus, this experimental study provides evidence of the potentially important
role of interkingdom competition in determining trophic interactions in saprophagous animal communities and the dynamics of
both host–parasitoid and microbial populations. 相似文献
867.
Jasper B. Green Ryan P. J. Lower J. Peter W. Young 《Journal of molecular evolution》2009,69(6):657-667
NfeD-like proteins are widely distributed throughout prokaryotes and are frequently associated with genes encoding stomatin-like
proteins (slipins). Here, we reveal that the NfeD family is ancient and comprises three major groups: NfeD1a, NfeD1b and truncated
NfeD1b. Members of each group are associated with one of four conserved gene partners, three of which have eukaryotic homologues
that are membrane raft associated, namely stomatin, paraslipin (previously SLP-2) and flotillin. The first NfeD group (NfeD1b),
comprises proteins of approximately 460-aa long that have three functional domains: an N-terminal protease, a middle membrane-spanning
region and a soluble C-terminal region rich in β-strands. The nfeD1b gene is adjacent to eoslipin in prokaryotic genomes except in Firmicutes and Deinococci, where yqfA replaces eoslipin. Proteins in the second major group (NfeD1a) are homologous to the C-terminus of NfeD1b which forms a β-barrel-like domain,
and their genes are associated with paraslipin. Using OrthoMCL clustering, we show that nfeD1b genes have become truncated on many independent occasions giving rise to the third major group. These short NfeD homologues
frequently remain associated with their ancestral gene neighbour, resembling NfeD1a in structure, yet are much more related
to full-length NfeD1b; we term these “truncated NfeD1b”. These conserved associations suggest that NfeD proteins are dependent
on gene partners for their function and that the site of interaction may lie within the C-terminal portion that is common
to all NfeD homologues. Although NfeD homologues are confined to prokaryotes, this conserved association could represent an
excellent system to study slipin and flotillin proteins. 相似文献
868.
Marieke van Eijk 《Culture, medicine and psychiatry》2017,41(4):590-608
What is a clinician to do when people needing medical care do not have access to consistent or sufficient health insurance coverage and cannot pay for care privately? Analyzing ethnographically how clinicians at a university-based transgender clinic in the United States responded to this challenge, I examine the U.S. health insurance system, insurance paperwork, and administrative procedures that shape transgender care delivery. To buffer the impact of the system’s failure to provide sufficient health insurance coverage for transgender care, clinicians blended administrative routines with psychological therapy, counseled people’s minds and finances, and leveraged the prestige of their clinic in attempts to create space for gender nonconforming embodiments in gender conservative insurance policies. My analysis demonstrates that in a market-based health insurance system with multiple payers and gender binary insurance rules, health care may be unaffordable, or remain financially challenging, even for transgender people with health insurance. Moreover, insurance carriers’ “reliance” on clinicians’ insurance-related labor is problematic as it exacerbates existing insurance barriers to the accessibility and affordability of transgender care and obscures the workings of a financial payment model that prioritizes economic expediency over gender nonconforming health. 相似文献
869.
870.