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   526篇
  免费   33篇
  2021年   3篇
  2019年   1篇
  2018年   5篇
  2017年   5篇
  2016年   13篇
  2015年   10篇
  2014年   12篇
  2013年   30篇
  2012年   25篇
  2011年   26篇
  2010年   6篇
  2009年   17篇
  2008年   23篇
  2007年   21篇
  2006年   25篇
  2005年   20篇
  2004年   21篇
  2003年   19篇
  2002年   12篇
  2001年   28篇
  2000年   41篇
  1999年   23篇
  1998年   5篇
  1997年   13篇
  1996年   8篇
  1995年   9篇
  1994年   3篇
  1993年   4篇
  1992年   25篇
  1991年   11篇
  1990年   13篇
  1989年   11篇
  1988年   14篇
  1987年   6篇
  1986年   3篇
  1985年   8篇
  1984年   6篇
  1983年   3篇
  1980年   4篇
  1979年   4篇
  1978年   4篇
  1977年   5篇
  1976年   1篇
  1975年   1篇
  1972年   3篇
  1970年   2篇
  1969年   2篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有559条查询结果,搜索用时 15 毫秒
31.
VE-cadherin and claudin-5 are major components of adherens and tight junctions of vascular endothelial cells and a decrease in their expression and an increase in the tyrosine-phosphorylation of VE-cadherin are associated with an increase in endothelial paracellular permeability. To clarify the mechanism underlying the development of edema in nasal polyps, we studied these molecules in polyp microvessels. Normal inferior turbinate mucosal tissues and nasal polyps from patients treated with or without glucocorticoid were stained for VE-cadherin or claudin-5 and CD31 by a double-immunofluorescence method and the immunofluorescence intensities were graded 1–3 with increasing intensity. To correct for differences in fluorescence intensity attributable to a different endothelial area being exposed in a section or to the thickness of a section, the relative immunofluorescence intensity was estimated by dividing the grade of VE-cadherin or claudin-5 by that of CD31 in each microvessel. Tyrosine-phosphorylation of VE-cadherin was examined by Western blot analysis. The relative intensities of VE-cadherin and claudin-5 in the CD31-positive microvessels significantly decreased in the following order; inferior turbinate mucosa, treated polyps and untreated polyps. The ratio of tyrosine-phosphorylated VE-cadherin to VE-cadherin was significantly higher in untreated polyps than in the inferior turbinate mucosa and treated polyps, between which no significant difference in the ratio was seen. Thus, in nasal polyps, the barrier function of endothelial adherens and tight junctions is weakened, although glucocorticoid treatment improves this weakened barrier function.  相似文献   
32.
To elucidate the specific interactions between the peroxisome proliferator-activated receptor (PPARα) and ligand GW409544 (GW), we obtained the solvated structures of the PPARα+GW complexes for human, mouse and rat by classical molecular mechanics calculations, and investigated their electronic properties by ab initio fragment molecular orbital calculations. The results indicate that the positively charged amino acids (Lys and Arg) of PPARα make a major contribution to the binding between PPARα and GW. In addition, it was clarified that Ser280 and Tyr314 of human and rat PPARα have a large attractive interaction with GW, while Ser280, Tyr314 and His440 of mouse PPARα have large interaction. These results on the difference in specific interactions between human and mouse/rat PPARα will be useful for predicting the effects of new chemicals on the human body based on the biomedical studies for the experimental animals such as mouse and rat.  相似文献   
33.
Prostaglandins are biologically active substances used in a wide range of medical treatments. Prostaglandins have been supplied mainly by chemical synthesis; nevertheless, the high cost of prostaglandin production remains a factor. To lower the cost of prostaglandin production, we attempted to produce prostaglandins using a liverwort, Marchantia polymorpha L., which accumulates arachidonic acid, which is known as a substrate of prostaglandins. Here we report the first bioproduction of prostaglandins in plant species by introducing a cyclooxygenase gene from a red alga, Gracilaria vermiculophylla into the liverwort. The transgenic liverworts accumulated prostaglandin F, prostaglandin E2 and prostaglandin D2 which were not detected in the wild-type liverwort. Moreover, we succeeded in drastically increasing the bioproduction of prostaglandins using an in vitro reaction system with the extracts of transgenic liverworts.  相似文献   
34.
Recent studies have shown that Notch signaling is involved in many types of cancers, including oral squamous cell carcinomas (OSCCs). However, the role of Notch signaling in the tumor microenvironment is not yet fully understood. In this study, we investigated the roles of NOTCH3 signaling in cancer associated fibroblasts (CAFs) in OSCCs. Immunohistochemical study of 93 human tongue OSCC cases indicated that about one third of OSCCs showed NOTCH3 expression in CAFs, and that this expression significantly correlated with tumor-size. In vitro study showed that OSCC cell lines, especially HO1-N-1 cells stimulated NOTCH3 expression in normal human dermal fibroblasts (NHDFs) through direct cell-to-cell contact. Immunohistochemical and morphometric analysis using human OSCC samples demonstrated that NOTCH3 expression in CAFs significantly correlated with micro-vessel density in cancer stroma. In vitro angiogenesis assays involving co-culture of NHDFs with HO1-N-1 and human umbilical endothelial cells (HUVECs), and NOTCH3 knockdown in NHDFs using siRNA, demonstrated that HO1-N-1 cells significantly promoted tube formation dependent on NOTCH3-expression in NHDFs. Moreover, NOTCH3 expression in CAFs was related to poor prognosis of the OSCC patients. This work provides a new insight into the role of Notch signaling in CAFs associated with tumor angiogenesis and the possibility of NOTCH3-targeted molecular therapy in OSCCs.  相似文献   
35.
36.
ObjectivesTo assess the effects of urinary diversion on renal function, we retrospectively investigated renal function over 5 years after urinary diversion using a propensity score matching strategy.MethodsBetween May 1996 and November 2013, 345 consecutive adult patients underwent radical cystectomy and urinary diversion in our hospital; one hundred and fifteen patients with more than a 5-year follow-up were enrolled. Propensity scores were calculated using logistic analysis, and the data used in the analyses included age, gender, Eastern Cooperative Oncology Group Performance Status (ECOG-PS), clinical tumor stage, presence of cardiovascular disease; hypertension; and type 2 diabetes and preoperative eGFR at the initial visit. Multivariate logistic regression analysis was used to assess the risk factors for stage 3B chronic kidney disease (CKD) after the different types of urinary diversion.ResultsContinent and incontinent diversion were performed in 68 and 47 patients, respectively. The mean preoperative eGFR was significantly lower in the incontinent than in the continent group (P < 0.001). In propensity score-matched patients (n = 34 each), no significant differences were observed in pre- and postoperative eGFR and 5-year eGFR decrease rates between the groups. In the incontinent group, the number of postoperative stage 3B CKD patients was significantly increased than the continent group. Using multivariate analysis, independent risk factors significantly associated with stage 3B CKD at 5 years after surgery were older age, eGFR before surgery, incontinent diversion (cutaneous ureterostomy), and postoperative hydronephrosis.ConclusionsThe types of urinary diversion had no significant impact on renal function decline, whereas older age, preexisting impaired renal function, postoperative hydronephrosis, and cutaneous ureterostomy were independent risk factors for stage 3B CKD at 5 years after radical cystectomy.  相似文献   
37.
A cell line, designated NOCC, was established from the ascites of a patient with clear cell adenocarcinoma of the ovary. The cell line has been grown without interruption and continuously propagated by serial passaging (more than 76 times) over 7 years. The cells are spherical to polygonal-shaped, display neoplastic, and pleomorphic features, and grow in a jigsaw puzzle-like pattern while forming monolayers without contact inhibition. The cells proliferate rapidly, but are easily floated as a cell sheet. The population doubling time is about 29 h. The number of chromosomes ranges from 60 to 83. The modal number of chromosomes is 70–74 at the 30th passage. NOCC cells secreted 750.5 ng/ml of VEGF over 3 days of culture. Hypoxia inducible factor-1α (HIF-1α) is a primary regulator of VEGF under hypoxic conditions. NOCC cells were not sensitive to the anticancer drugs BEV, DOX, GEM, ETP, CDDP, or TXT. The graft of NOCC cells to a scid mouse displayed similar histological aspects to the original tumor. Both the NOCC cells and the graft of the NOCC cells gave a positive PAS reaction.  相似文献   
38.
Type V collagen selectively inhibits human endothelial cell proliferation   总被引:3,自引:0,他引:3  
Type V collagen from human placenta remarkably inhibited human umbilical vein endothelial cell (HUVEC) proliferation in a dose-dependent manner when coated on the culture dishes. Other types of collagen (I, III, IV) and fibronectin enhanced HUVEC proliferation under the same conditions. The inhibitory activity of type V collagen was seen not only when it was coated on the dishes, but also when it was directly added into cell culture. The attachment effect of type V collagen did not differ from that of type I collagen. The inhibitory activity is a phenomenon selective for endothelial cells, since type V collagen did not affect the proliferation of human umbilical vein smooth muscle cells, aortic smooth muscle cells, or nasal mucosa fibroblasts.  相似文献   
39.
1. Three perchloric acid-soluble fractions from ascites of three primary ovarian cancer patients were subjected to Sephacryl S-300 gel filtration, respectively, and three Fr. 1 which were eluted in the vicinity of void volume as minor fractions, were then separated by a systematic affinity chromatography using Vicia unijuga lectin-Sepharose CL-4B column and Arachis hypogaea lectin-Sepharose CL-4B column into three glycoproteins, blood group N antigen precursor glycoprotein with Thomsen-Friedenreich (T) activity, T-active glycoprotein and N antigen precursor glycoprotein, respectively. 2. These nine glycoproteins separated in yields of 0.1-1.3 mg per 100 ml of ascites, were demonstrated to be mucin-type glycoproteins with Mw of 1,791,000-4,921,000 and contained 33.8-56.1% carbohydrates.  相似文献   
40.
Globular tail of myosin-V is bound to vamp/synaptobrevin   总被引:1,自引:0,他引:1  
VAMP/synaptobrevin is one of a number of v-SNAREs involved in vesicular fusion events in neurons. In a previous report, VAMP was shown to form a complex with synaptophysin and myosin V, a motor protein based on the F-actin, and that myosin V was then released from the complex in a Ca(2+)-dependent manner. Here, we found that VAMP alone is bound to myosin V in a Ca(2+)-independent manner, and determined that the globular tail domain of myosin V is its binding site. The syntaxin-VAMP-myosin V formed in the presence of Ca(2+)/calmodulin (CaM). In the absence of CaM, only syntaxin-VAMP, or VAMP-myosin V complex was formed. Our results suggest that VAMP acts as a myosin V receptor on the vesicles and regulates formation of the complex.  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