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   3995篇
  免费   212篇
  国内免费   235篇
  4442篇
  2024年   20篇
  2023年   67篇
  2022年   108篇
  2021年   112篇
  2020年   106篇
  2019年   120篇
  2018年   132篇
  2017年   85篇
  2016年   122篇
  2015年   250篇
  2014年   278篇
  2013年   332篇
  2012年   162篇
  2011年   178篇
  2010年   141篇
  2009年   203篇
  2008年   199篇
  2007年   216篇
  2006年   174篇
  2005年   181篇
  2004年   179篇
  2003年   138篇
  2002年   120篇
  2001年   84篇
  2000年   72篇
  1999年   75篇
  1998年   74篇
  1997年   68篇
  1996年   54篇
  1995年   55篇
  1994年   48篇
  1993年   44篇
  1992年   28篇
  1991年   30篇
  1990年   32篇
  1989年   28篇
  1988年   18篇
  1987年   22篇
  1986年   12篇
  1985年   9篇
  1984年   19篇
  1983年   12篇
  1982年   12篇
  1981年   5篇
  1980年   7篇
  1979年   4篇
  1978年   2篇
  1976年   2篇
  1974年   2篇
  1971年   1篇
排序方式: 共有4442条查询结果,搜索用时 15 毫秒
91.
The Bcl‐2 family modulates sensitivity to chemotherapy in many cancers, including melanoma, in which the RAS/BRAF/MEK/ERK pathway is constitutively activated. Mcl‐1, a major anti‐apoptotic protein in the Bcl‐2 family, is extensively expressed in melanoma and contributes to melanoma's well‐documented chemoresistance. Here, we provide the first evidence that Mcl‐1 phosphorylation at T163 by ERK1/2 and JNK is associated with the resistance of melanoma cell lines to the existing BH3 mimetics gossypol, S1 and ABT‐737, and a novel anti‐apoptotic mechanism of phosphorylated Mcl‐1 (pMcl‐1) is revealed. pMcl‐1 antagonized the known BH3 mimetics by sequestering pro‐apoptotic proteins that were released from Bcl‐2/Mcl‐1. Furthermore, an anthraquinone BH3 mimetic, compound 6, was identified to be the first small molecule to that induces endogenous apoptosis in melanoma cells by directly binding Bcl‐2, Mcl‐1, and pMcl‐1 and disrupting the heterodimers of these proteins. Although compound 6 induced upregulation of the pro‐apoptotic protein Noxa, its apoptotic induction was independent of Noxa. These data reveal the promising therapeutic potential of targeting pMcl‐1 to treat melanoma. Compound 6 is therefore a potent drug that targets pMcl‐1 in melanoma.  相似文献   
92.
93.
To characterize Fe homeostasis during the early stages of seed germination, a microarray analysis was performed. mRNAs extracted from fully mature seeds or seeds harvested 1–3 days after sowing were hybridized to a rice microarray containing approximately 22,000 cDNA oligo probes. Many Fe deficiency-inducible genes were strongly expressed throughout early seed germination. These results suggest that the demand for Fe is extremely high during germination. Under Fe-deficient conditions, rice produces and secretes a metal-cation chelator called deoxymugineic acid (DMA) to acquire Fe from the soil. In addition, DMA and its intermediate nicotianamine (NA) are thought to be involved in long distance Fe transport in rice. Using promoter-β-glucuronidase (GUS) analysis, we investigated the expression patterns during seed germination of the Fe deficiency-inducible genes OsNAS1, OsNAS2, OsNAS3, OsNAAT1, and OsDMAS1, which encode enzymes that participate in the biosynthesis of DMA, and the transporter genes OsYSL2 and OsIRT1, which are involved in Fe transport. All of these genes were expressed in germinating seeds prior to protrusion of the radicle. These results suggest that DMA and NA are produced and involved in Fe transport during germination. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
94.
This mother—daughter case study focuses on a key feature of discourse within a Mexican immigrant family that links oral traditions to resilience and motivation. I combine observations from a previous ethnographic study with recent follow-up interviews of a Mexican immigrant student building on a funds of knowledge framework and an ecological perspective. Expanding on current mother—daughter pedagogic theory, I map "dichos" as they are emblematic of cultural funds of knowledge and how they assume a relationship to resistance and academic attainment for a young Mexican immigrant. The findings challenge the notion that working-class Latino families do not care about the educational fortunes of their youth and lack knowledge and resources to guide their children academically.  相似文献   
95.
William Julius Wilson’s model of adult joblessness, community disorganization and their effects on youth problem behaviour de-emphasizes the range in children’s outcomes across socially disorganized communities, and says little about the factors that influence this variation. It also does not address the processes by which family structure and relationships affect the well-being of African-American and poor youth. My work is part of a larger research agenda that has begun to address these issues by focusing on the differential rates of sexual activity among youth living in disadvantaged environments, and developing models to explain this variation. This work suggests that units of socially cohesive, stable adults exist among the social networks of successful children and families in poor neighbourhoods. It also points to the existence and functioning of alternative two-parent family structures and offers hypotheses for how family environment interacts with neighbourhood context to influence youth behaviour.  相似文献   
96.
报道了秦岭蕨类植物新记录科——肠蕨科,其新记录种为川黔肠蕨,该科也是陕西省新记录。文中提供了形态描述和野外照片及植株局部照片,并对其生境特点进行了简要分析。凭证标本藏于陕西理工大学植物标本馆。  相似文献   
97.
98.
99.
100.
Approximately 1%–2% of cutaneous melanoma (CM) is classified as strongly familial. We sought to investigate unexplained CM predisposition in families negative for the known susceptibility genes using next‐generation sequencing of affected individuals. Segregation of germline variants of interest within families was assessed by Sanger sequencing. Several heterozygous variants in oculocutaneous albinism (OCA) genes: TYR, OCA2, TYRP1 and SLC45A2, were present in our CM cohort. OCA is a group of autosomal recessive genetic disorders, resulting in pigmentation defects of the eyes, hair and skin. Missense variants classified as pathogenic for OCA were present in multiple families and some fully segregated with CM. The functionally compromised TYR p.T373K variant was present in three unrelated families. In OCA2, known pathogenic variants: p.V443I and p.N489D, were present in three families and one family, respectively. We identified a likely pathogenic SLC45A2 frameshift variant that fully segregated with CM in a family of four cases. Another four‐case family harboured cosegregating variants (p.A24T and p.R153C) of uncertain functional significance in TYRP1. We conclude that rare, heterozygous variants in OCA genes confer moderate risk for CM.  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