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   4445篇
  免费   414篇
  国内免费   61篇
  2023年   26篇
  2022年   24篇
  2021年   115篇
  2020年   61篇
  2019年   95篇
  2018年   107篇
  2017年   81篇
  2016年   131篇
  2015年   231篇
  2014年   243篇
  2013年   300篇
  2012年   388篇
  2011年   342篇
  2010年   201篇
  2009年   176篇
  2008年   238篇
  2007年   237篇
  2006年   225篇
  2005年   187篇
  2004年   166篇
  2003年   154篇
  2002年   143篇
  2001年   131篇
  2000年   98篇
  1999年   93篇
  1998年   33篇
  1997年   26篇
  1996年   37篇
  1995年   43篇
  1994年   37篇
  1993年   20篇
  1992年   48篇
  1991年   33篇
  1990年   42篇
  1989年   45篇
  1988年   33篇
  1987年   30篇
  1986年   33篇
  1985年   37篇
  1984年   21篇
  1983年   22篇
  1982年   12篇
  1980年   18篇
  1979年   24篇
  1976年   10篇
  1975年   16篇
  1974年   11篇
  1973年   11篇
  1970年   12篇
  1969年   13篇
排序方式: 共有4920条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
Weng  Shaoting  Zhao  Yitian  Yu  Changhong  Wang  Xiaofan  Xiao  Xuehan  Han  Liqiang  Zhang  Kunpeng  Wang  Jiang  Yang  Guoyu 《Biotechnology letters》2021,43(11):2111-2129
Biotechnology Letters - An ideal rAAV gene editing system not only effectively edits genes at specific site, but also prevents the spread of the virus from occurring off-target or carcinogenic...  相似文献   
6.
Hepatocellular carcinoma (HCC) is one of the major malignancies worldwide and is associated with poor prognosis due to the high incidences of metastasis and tumor recurrence. Our previous study showed that overexpression of p21-activated protein kinase 1 (PAK1) is frequently observed in HCC and is associated with a more aggressive tumor behavior, suggesting that PAK1 is a potential therapeutic target in HCC. In the current study, an allosteric small molecule PAK1 inhibitor, IPA-3, was evaluated for the potential in suppressing hepatocarcinogenesis. Consistent with other reports, inhibition of PAK1 activity was observed in several human HCC cell lines treated with various dosages of IPA-3. Using cell proliferation, colony formation and BrdU incorporation assays, we demonstrated that IPA-3 treatment significantly inhibited the growth of HCC cells. The mechanisms through which IPA-3 treatment suppresses HCC cell growth are enhancement of apoptosis and blockage of activation of NF-κB. Furthermore, our data suggested that IPA-3 not only inhibits the HCC cell growth, but also suppresses the metastatic potential of HCC cells. Nude mouse xenograft assay demonstrated that IPA-3 treatment significantly reduced the tumor growth rate and decreased tumor volume, indicating that IPA-3 can suppress the in vivo tumor growth of HCC cells. Taken together, our demonstration of the potential preclinical efficacy of IPA-3 in HCC provides the rationale for cancer therapy.  相似文献   
7.
8.
Lam , S. L. and A. C. Leopold . (Purdue U., Lafayette, Indiana.) Reversion from flowering to the vegetative state in Xanthium. Amer. Jour. Bot. 47(4): 256—259. Illus. 1960.–Plants of Xanthium pensylvanicum Wallr. which had been induced with short photoperiods were caused to revert to the vegetative state either by decapitation or by pinching and subsequent partial de-budding. The ability of induced plants to revert varies with the intensity of the inductive stimulus, and with the extent to which the plant is cut back. Four successive decapitation treatments caused complete reversion of almost all plants which had been given 7 inductive cycles. Reversion can be obtained after 3 inductive cycles even when all of the induced leaves remain on the plant. It is suggested that under the conditions of these experiments the synthesis of the flowering stimulus is stopped or the stimulus is immobilized in the leaves and made ineffective.  相似文献   
9.
Smooth-muscle myosin purified as described by Persechini & Hartshorne [(1983) Biochemistry 22, 470-476] contains trace amounts of calmodulin and myosin light-chain kinase, which can be removed by Ca2+-dependent hydrophobic-interaction chromatography followed by calmodulin-Sepharose affinity chromatography. The resultant column-purified myosin exhibits properties similar to those of the non-purified myosin, e.g. actin activation of the Mg2+-ATPase requires Ca2+/calmodulin-dependent phosphorylation of the two 20 kDa light chains. However, unlike the non-purified myosin, the column-purified myosin undergoes a time-dependent transition to a form which no longer requires phosphorylation for actin activation of the myosin Mg2+-ATPase. This transition is identified as a time-dependent change in conformation of the column-purified myosin from a 10 S to 6 S form and is caused by slow oxidation of the column-purified myosin, since it could be prevented by storage under N2 and reversed by 5 mM-dithiothreitol.  相似文献   
10.
Objectives: Myofibroblasts are a vital component of stroma of many malignant neoplasms, but it is not yet established whether stromal myofibroblasts also exist in benign tumours such as oncocytoma of the kidney. Materials and methods: Histomorphological and immunohistochemical analysis of 16 renal oncocytomas diagnosed at Chang Gung Memorial Hospital, Taiwan, has been performed. Results: Renal oncocytomas were composed of oncocytes, large cells with granular eosinophilic cytoplasm, arranged mostly in sheets, in tubulocystic or combined pattern. Few oncocytes appeared to be undergoing proliferation or apoptosis. MIB‐1 and active caspase 3 indices were low, but higher in tumour than in surrounding non‐tumour parenchyma (MIB‐1: 0.93 ± 0.09 versus 0.46 ± 0.07, P < 0.001 and active caspase 3: 0.76 ± 0.08 versus 0.41 ± 0.09, P < 0.001). Wnt/β‐catenin signalling was not implicated in this neoplasm, as there was no loss of E‐cadherin membranous localization or expression of intranuclear β‐catenin in the cells. Clumps of oncocytes were stained with periodic acid Schiff and had collagen I‐, collagen III‐ and fibronectin‐positive, but desmin‐ and human caldesmon‐negative stromas. Importantly, α‐smooth muscle actin (SMA)‐immunostaining established the myofibroblastic nature of many of the stromal cells. Some of the myofibroblasts were also positive for MIB‐1, indicating a proliferative role for them in the stroma. Conclusions: Renal oncocytomas were composed of two independent compartments: benign oncocytes and pronounced fibrotic stroma, which consisted of proliferating myofibroblasts (SMA‐ and MIB‐1‐positive) which were associated with excessive deposition of extracellular matrix (periodic acid Schiff‐component, collagen I‐, collagen III‐ and fibronectin‐positive, and desmin‐ and human caldesmon‐negative).  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