全文获取类型
收费全文 | 3965篇 |
免费 | 203篇 |
国内免费 | 229篇 |
专业分类
4397篇 |
出版年
2024年 | 20篇 |
2023年 | 67篇 |
2022年 | 105篇 |
2021年 | 110篇 |
2020年 | 104篇 |
2019年 | 115篇 |
2018年 | 129篇 |
2017年 | 84篇 |
2016年 | 117篇 |
2015年 | 248篇 |
2014年 | 276篇 |
2013年 | 330篇 |
2012年 | 163篇 |
2011年 | 178篇 |
2010年 | 139篇 |
2009年 | 201篇 |
2008年 | 196篇 |
2007年 | 214篇 |
2006年 | 173篇 |
2005年 | 179篇 |
2004年 | 177篇 |
2003年 | 139篇 |
2002年 | 120篇 |
2001年 | 79篇 |
2000年 | 73篇 |
1999年 | 75篇 |
1998年 | 72篇 |
1997年 | 68篇 |
1996年 | 55篇 |
1995年 | 56篇 |
1994年 | 48篇 |
1993年 | 42篇 |
1992年 | 27篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 28篇 |
1988年 | 17篇 |
1987年 | 24篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有4397条查询结果,搜索用时 10 毫秒
991.
Lack of evidence to favor specific preventive interventions in psychosis: a network meta‐analysis 下载免费PDF全文
Cathy Davies Andrea Cipriani John P.A. Ioannidis Joaquim Radua Daniel Stahl Umberto Provenzani Philip McGuire Paolo Fusar‐Poli 《World psychiatry》2018,17(2):196-209
Preventing psychosis in patients at clinical high risk may be a promising avenue for pre‐emptively ameliorating outcomes of the most severe psychiatric disorder. However, information on how each preventive intervention fares against other currently available treatment options remains unavailable. The aim of the current study was to quantify the consistency and magnitude of effects of specific preventive interventions for psychosis, comparing different treatments in a network meta‐analysis. PsycINFO, Web of Science, Cochrane Central Register of Controlled Trials, and unpublished/grey literature were searched up to July 18, 2017, to identify randomized controlled trials conducted in individuals at clinical high risk for psychosis, comparing different types of intervention and reporting transition to psychosis. Two reviewers independently extracted data. Data were synthesized using network meta‐analyses. The primary outcome was transition to psychosis at different time points and the secondary outcome was treatment acceptability (dropout due to any cause). Effect sizes were reported as odds ratios and 95% confidence intervals (CIs). Sixteen studies (2,035 patients, 57% male, mean age 20.1 years) reported on risk of transition. The treatments tested were needs‐based interventions (NBI); omega‐3 + NBI; ziprasidone + NBI; olanzapine + NBI; aripiprazole + NBI; integrated psychological interventions; family therapy + NBI; D‐serine + NBI; cognitive behavioural therapy, French & Morrison protocol (CBT‐F) + NBI; CBT‐F + risperidone + NBI; and cognitive behavioural therapy, van der Gaag protocol (CBT‐V) + CBT‐F + NBI. The network meta‐analysis showed no evidence of significantly superior efficacy of any one intervention over the others at 6 and 12 months (insufficient data were available after 12 months). Similarly, there was no evidence for intervention differences in acceptability at either time point. Tests for inconsistency were non‐significant and sensitivity analyses controlling for different clustering of interventions and biases did not materially affect the interpretation of the results. In summary, this study indicates that, to date, there is no evidence that any specific intervention is particularly effective over the others in preventing transition to psychosis. Further experimental research is needed. 相似文献
992.
Furutani Y Umemoto T Murakami M Matsui T Funaba M 《Journal of cellular biochemistry》2011,112(2):614-624
The present study evaluated endogenous activities and the role of BMP and transforming growth factor-β (TGF-β), representative members of the TGF-β family, during myotube differentiation in C2C12 cells. Smad phosphorylation at the C-terminal serines was monitored, since TGF-β family members signal via the phosphorylation of Smads in a ligand-dependent manner. Expression of phosphorylated Smad1/5/8, which is an indicator of BMP activity, was higher before differentiation, and rapidly decreased after differentiation stimulation. Differentiation-related changes were consistent with those in the expression of Ids, well-known BMP-responsive genes. Treatment with inhibitors of BMP type I receptors or noggin in C2C12 myoblasts down-regulated the expression of myogenic regulatory factors, such as Myf5 and MyoD, leading to impaired myotube formation. Addition of BMP-2 during the myoblast phase also inhibited myotube differentiation through the down-regulation of Myf5 and MyoD. In contrast to endogenous BMP activity, the phosphorylation of Smad2, a TGF-β-responsive Smad, was higher 8-16 days after differentiation stimulation. A-83-01, an inhibitor of TGF-β type I receptor, increased the expression of Myf5 and MyoD, and enhanced myotube formation. The present results reveal that endogenous activities of the TGF-β family are changed during myogenesis in a pathway-specific manner, and that the activities are required for myogenesis. 相似文献
993.
Ngang Heok Tang Naoyuki Okada Chii Shyang Fong Kunio Arai Masamitsu Sato Takashi Toda 《FEBS letters》2014
The conserved TACC protein family localises to the centrosome (the spindle pole body, SPB in fungi) and mitotic spindles, thereby playing a crucial role in bipolar spindle assembly. However, it remains elusive how TACC proteins are recruited to the centrosome/SPB. Here, using fission yeast Alp7/TACC, we have determined clustered five amino acid residues within the TACC domain required for SPB localisation. Critically, these sequences are essential for the functions of Alp7, including proper spindle formation and mitotic progression. Moreover, we have identified pericentrin-like Pcp1 as a loading factor to the mitotic SPB, although Pcp1 is not a sole platform. 相似文献
994.
自噬(autophagy)是一种进化保守的溶酶体依赖性分解代谢途径,是细胞维持自稳态的重要机制之一,并参与多种疾病的发生. Beclin-1作为自噬体成核的关键分子之一,是1个调节自噬的关键靶点. Beclin-1有1个BH3结构域,Bcl-2、Bcl-XL等可以通过这个BH3结构域与Beclin-1结合而影响其活性. 抗凋亡Bcl-2家族蛋白和Beclin-1的表达水平、磷酸化、分子的亚细胞定位以及BH3-only蛋白等,均可调节Beclin-1蛋白和Bcl-2家族蛋白结合水平,进而调控自噬的发生,并可能对细胞最终走向自噬还是凋亡起着关键作用. 相似文献
995.
Cichlid fishes of the east African Great Lakes represent a paradigm of adaptive radiation. We conducted a phylogenetic analysis of cichlids including pan-African and west African species by using insertion patterns of short interspersed elements (SINEs) at orthologous loci. The monophyly of the east African cichlids was consistently supported by seven independent insertions of SINE sequences that are uniquely shared by these species. In addition, data from four other loci indicated that the genera Tilapia (pan-African) and Steatocranus (west African) are the closest relatives to east African cichlids. However, relationships among Tilapia, Steatocranus, and the east African clade were ambiguous because of incongruencies among topologies suggested by insertion patterns of SINEs at six other loci. One plausible explanation for this phenomenon is incomplete lineage sorting of alleles containing or missing a SINE insertion at these loci during ancestral speciation. Such incomplete sorting may have taken place earlier than 14 MYA, followed by random and stochastic fixation of the alleles in subsequent lineages. These observations prompted us to consider the possibility that cichlid speciation occurred at an accelerated rate during this period when the African Great Lakes did not exist. The SINE method could be useful for detecting ancient exclusive speciation events that tend to remain hidden during conventional sequence analyses because of accumulated point mutations. 相似文献
996.
997.
998.
Juan David Bayona-Serrano Vincent Louis Viala Rhett M Rautsaw Tristan D Schramer Gesiele A Barros-Carvalho Milton Yutaka Nishiyama Jr Luciana A Freitas-de-Sousa Ana Maria Moura-da-Silva Christopher L Parkinson Felipe Gobbi Grazziotin Incio L M Junqueira-de-Azevedo 《Molecular biology and evolution》2020,37(12):3563
999.
M. Torki P. Mandaron F. Thomas F. Quigley R. Mache D. Falconet 《Molecular & general genetics : MGG》1999,261(6):948-952
By systematic sequencing of a flower bud cDNA library from Arabidopsis thaliana, we have identified four cDNAs encoding polygalacturonase. The corresponding genes, together with seven other A. thaliana genes present in the databases, form a small gene family. Sequence comparisons of the deduced polypeptides within the gene
family or with other plant polygalacturonases allow classification of the genes into different clades. Five polygalacturonases,
including all those isolated from the flower buds, are closely related to the enzyme in pollen. Of the six remaining polygalacturonases,
three are more closely related to the abscission-specific type of enzyme and two others to the fruit polygalacturonase. The
last one is more distantly related to the others and might correspond to a new type of polygalacturonase. Expression of the
different genes was analysed on Northern blots and by a PCR-based strategy. Results indicate that if, as expected, the cDNAs
isolated from the flower bud library are strongly expressed in pollen, other genes are expressed at a low level in young developing
tissues, such as in seedlings and roots, suggesting that they could be implicated in the cell wall modifications observed
during cell elongation and/or expansion which occur in these tissues.
Received: 7 December 1998 / Accepted: 1 April 1999 相似文献
1000.
Sen B 《Obesity (Silver Spring, Md.)》2006,14(12):2266-2276
Objective: To explore associations between overweight status and the frequency of family dinners (FFD) for adolescents and how those associations differ across race and ethnicity. Research Methods and Procedures: A sample of 5014 respondents between 12 and 15 years of age from the 1997 wave of the National Longitudinal Survey of Youth 1997 (NLSY97) was used. BMI was calculated using self‐reported height and weight; 13.3% of respondents qualified as overweight, 16.4% qualified as at‐risk‐of‐overweight, and 1.9% qualified as underweight. The remainder were normal weight. FFD was defined as the number of times respondents had dinner with their families in a typical week in the past year. Multinomial logistic regression models were estimated separately for non‐Hispanic whites vs. blacks and Hispanics for odds of belonging to the other weight categories compared with normal weight. A supplementary longitudinal analysis estimated the odds of change in overweight status between 1997 and 2000. Results: In 1997, the FFD distribution was as follows: 0, 8.3%; 1 or 2, 7.3%; 3 or 4, 13.4%; 5 or 6, 28.1%; 7, 42%. For whites, higher FFD was associated with reduced odds of being overweight in 1997, reduced odds of becoming overweight, and increased odds of ceasing to be overweight by 2000. No such associations were found for blacks and Hispanics. Discussion: Reasons for racial and ethnic differences in the relationship between FFD and overweight may include differences in the types and portions of food consumed at family meals. More research is needed to verify this. 相似文献