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   761篇
  免费   33篇
  794篇
  2023年   2篇
  2022年   10篇
  2021年   18篇
  2020年   12篇
  2019年   16篇
  2018年   33篇
  2017年   17篇
  2016年   34篇
  2015年   50篇
  2014年   54篇
  2013年   69篇
  2012年   62篇
  2011年   62篇
  2010年   25篇
  2009年   32篇
  2008年   43篇
  2007年   52篇
  2006年   53篇
  2005年   36篇
  2004年   33篇
  2003年   24篇
  2002年   27篇
  2001年   3篇
  2000年   1篇
  1999年   1篇
  1998年   4篇
  1997年   4篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1992年   4篇
  1991年   2篇
  1989年   1篇
  1987年   1篇
  1982年   1篇
  1980年   1篇
排序方式: 共有794条查询结果,搜索用时 0 毫秒
71.
INTRODUCTION: The aim of the study was to determine the expression of selected adhesive molecules in papillary thyroid carcinoma. MATERIAL AND METHODS: 47 papillary thyroid carcinoma cases and 11 nonmalignant goiter cases were analyzed by immunohistochemistry. RESULTS: Galectin-3 (LGAL3) was a sensitive and specific marker, present in 91% of analyzed tumors and only in 5% of tumor margin. The presence of CA50 was 86% and 3% respectively with only 3% positive non-malignant cases. Cadherin E expression was noted in 91% of primary tumors, in 84% of the surrounding tissue and in 63% of non-malignant goiter. CD44 (DF1485) was observed in 89% of primary tumors and 48% of surrounding tissue; the reaction with BBA10 was more characteristic for metastases. CONCLUSIONS: Our study confirms the high diagnostic value of galectin-3 in papillary thyroid carcinoma and reveals the similar efficiency of CA50. CD44 (DF1485) expression in primary tumor is more intensive than in surrounding tissue, but the diagnostical inportance is not high because it is often observed in benign lesions. Using of BBA10 is more sensitive, but less specific. High expression of cadherin E in benign lesions impairs its diagnostical application in papillary thyroid cancer.  相似文献   
72.
73.
In between-subjects studies on two groups of women of the same age, we show that women assess male's facial attractiveness differently in the follicular (F) and luteal (L) phases. In the high conception risk phase (F), women tended to give higher scores to male faces than when they were in the luteal phase. During the five first days of the cycle, i.e. when the estrogen level is still low, women assessed men's facial attractiveness relatively highly. We suggest that it is progesterone in the luteal phase that is responsible for lower attractiveness assigned then to male faces. We also tested which anthropometric facial traits or indices influence male attractiveness. We found that assessments of attractiveness were correlated only with mouth height (positively) and the angle between the middle of the mouth and the middle of the eyes (negatively). The results are compared with those from other studies and discussed in the light of evolutionary biology.  相似文献   
74.
Many medicinal plants contain oleanane saponins in roots, however, only scarce data on their biosynthesis in this organ are available so far, including our previous results concerning Calendula officinalis plant. Thus, the purpose of the present work was to confirm the presumable biosynthetic pathway of oleanolic acid glycosides in roots of young C. officinalis plants. First of all, the effective method of isolation of protoplasts from C. officinalis roots was established. Then, isolated root protoplasts were supplied with radioactive precursors, [2-14C] mevalonate (MVA) and [3-3H] oleanolic acid (OL) and their transformations were studied with comparison to results obtained with excised roots. The penetration of both precursors into protoplasts was more rapid and effective than in the case of excised roots. The labeling of sterols and OL during the incubation with MVA showed that the isoprenoid pathway leading to triterpenoids was operative in excised roots as well as isolated root protoplasts. Moreover, the transformations of OL into two series of its glycosides, i.e. glucosides and glucuronides were investigated. It has been shown that both series of OL glycosides are synthesized in isolated root protoplasts in the same way as in excised roots of young marigold plants.  相似文献   
75.
Lipocalins are a widely distributed group of proteins whose common feature is the presence of six-or eight-stranded beta-barrel in their tertiary structure and highly conservative motifs short conserved region, (SCR) in their amino acid sequences. The presence of three SCRs is typical for kernel lipocalins, while outlier lipocalins have only one or two such regions. Owing to their ability to bind and transport small, hydrophobic molecules, lipocalins participate in the distribution of such substances. However, the physiological significance of lipocalins is not limited to transfer processes. They play an important role in the regulation of immunological and developmental processes, and are also involved in the reactions of organisms to various stress factors and in the pathways of signal transduction. Of special interest is the enzymatic activity found in a few members of the lipocalin family, as well as the interaction with natural membranes, both directly with lipids and through membrane-localized protein receptors.  相似文献   
76.
77.
Klebsiella pneumoniae 287-w carries three small narrow host range (NHR) plasmids (pIGMS31, pIGMS32, and pIGRK), which could be maintained in several closely related species of Gammaproteobacteria, but not in Alphaproteobacteria. The plasmids contain different mobilization systems (MOB), whose activity in Escherichia coli was demonstrated in the presence of the helper transfer system originating from plasmid RK2. The MOBs of pIGMS31 and pIGMS32 are highly conserved in many bacterial plasmids (members of the MOB family), while the predicted MOB of pIGRK has a unique structure, encoding a protein similar to phage-related integrases. The MOBs of pIGMS31 and pIGMS32 enabled the transfer of heterologous replicons from E. coli into both gammaproteobacterial and alphaproteobacterial hosts, which suggests that these NHR plasmids contain broad host range MOB systems. Such plasmids therefore represent efficient carrier molecules, which may act as natural suicide vectors promoting the spread of diverse genetic information (including other types of mobile elements, e.g. resistance transposons) among evolutionarily distinct bacterial species. Thus, mobilizable NHR plasmids may play a much more important role in horizontal gene transfer than previously thought.  相似文献   
78.
In this work, the behavior of the neurohypophyseal hormones and their selected analogs was studied in the presence of membrane models in an attempt to correlate their activities with a distinct behavior at a level of peptide-lipid interactions. The influence of the peptides studied on the lipid acyl chain order was determined using FTIR spectroscopy. Conformational changes in the peptides upon binding to liposomes were examined using CD spectra. Attempts were also made to determine the binding parameters of the peptides to lipids using isothermal titration calorimetry (ITC). The results show unambiguously that the neurohyphophyseal hormone-like peptides interact with lipids, being a model of a eukaryotic cell membrane. Moreover, hydrophobic interactions between the peptides and liposomes are likely to determine the overall conformation of the peptide, especially below the temperature of the main phase transition (T(m)). Thus, the bulky and hydrophobic nature of the residues incorporated into the N-terminal part of neurohyphophyseal hormones is an important factor for both restriction of peptide mobility and the interaction of the analog with biomembrane. In turn, above T(m), the electrostatic interactions become also relevant for the conformation of the acyclic tail of the AVP-like peptides.  相似文献   
79.
As guinea fowl age, their body weights and length of the esophagus and crop increased significantly, and relative length (cm x 100 g b.w(-1)) of the small intestine, caeca and total intestine decreased significantly (P < or = 0.05) in males and females. In addition, 52-week-old males had a significantly higher percentage length of rectum and heart weight, and females a significantly higher gizzard weight compared to 13-week-old birds. Compared to females, adult males differed significantly (P < or = 0.05) in the length of caeca and also in the proportion of the gizzard, proventriculus, heart and liver in total weight.  相似文献   
80.
Cancer appears in the new form of cell life as a direct consequence of self-organising pre-cancer cells (dissipathogenic systems), whose further existence is disabled by extreme impairment of their metabolism. Life itself is the highest value, since instead of necrosis or apoptosis, the cellular system in an unfavourable environment can change its genetic identity provided that the improvement in its own metabolism leads to increased chaos by higher dissipation of matter and energy in its environment. Prolongation of human life has resulted by a longer period of old age which is favourable for self-organisation of dissipative neoplastic cells. Modern medicine has explained the relation of the cervical cancer to preterm births and to inadequate use of oral contraceptives and/or replacement, instead of supplementary, neurohormonal therapy. Therefore, as early as in the period of pregnancy reproductive cells should be protected due to their prime importance in the intergenerational passage of life. Disturbance of systemic autoregulation causes development of dissipathogenic state of cells. A single zygote, whose environment is also important for the future development of the next two generations that are initiated with its formation, defines the unique identity of each person, whose life is determined by free will and neoplasms.  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