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   2330篇
  免费   146篇
  国内免费   8篇
耳鼻咽喉   54篇
儿科学   28篇
妇产科学   58篇
基础医学   299篇
口腔科学   28篇
临床医学   237篇
内科学   491篇
皮肤病学   11篇
神经病学   183篇
特种医学   54篇
外科学   293篇
综合类   21篇
预防医学   271篇
眼科学   136篇
药学   221篇
中国医学   3篇
肿瘤学   96篇
  2022年   19篇
  2021年   57篇
  2020年   19篇
  2019年   47篇
  2018年   53篇
  2017年   33篇
  2016年   52篇
  2015年   41篇
  2014年   64篇
  2013年   113篇
  2012年   113篇
  2011年   142篇
  2010年   72篇
  2009年   76篇
  2008年   121篇
  2007年   136篇
  2006年   128篇
  2005年   131篇
  2004年   117篇
  2003年   133篇
  2002年   118篇
  2001年   30篇
  2000年   30篇
  1999年   30篇
  1998年   26篇
  1997年   39篇
  1996年   30篇
  1995年   22篇
  1994年   26篇
  1993年   22篇
  1992年   22篇
  1991年   17篇
  1990年   20篇
  1989年   18篇
  1988年   14篇
  1987年   19篇
  1986年   19篇
  1985年   11篇
  1984年   25篇
  1983年   12篇
  1982年   20篇
  1981年   21篇
  1980年   20篇
  1979年   15篇
  1978年   14篇
  1977年   15篇
  1976年   14篇
  1975年   28篇
  1968年   9篇
  1967年   9篇
排序方式: 共有2484条查询结果,搜索用时 31 毫秒
31.
Bowlby's attachment theory is a theory of psychopathology as well as a theory of normal development. It contains clear and specific propositions regarding the role of early experience in developmental psychopathology, the importance of ongoing context, and the nature of the developmental process underlying pathology. In particular, Bowlby argued that adaptation is always the joint product of developmental history and current circumstances (never either alone). Early experience does not cause later pathology in a linear way; yet, it has special significance due to the complex, systemic, transactional nature of development. Prior history is part of current context, playing a role in selection, engagement, and interpretation of subsequent experience and in the use of available environmental supports. Finally, except in very extreme cases, early anxious attachment is not viewed as psychopathology itself or as a direct cause of psychopathology but as an initiator of pathways probabilistically associated with later pathology.  相似文献   
32.

Purpose

Progressive motility (PM) and vitality are positively associated with fertilization ability of spermatozoa. Here, the effects of IGF-I and NGFβ on PM and vitality of human spermatozoa were investigated.

Methods

Forty-three volunteers gave semen samples after 2-3 days of sexual abstinence. Each sample was processed with density gradient centrifugation and sperm washing. The pellet was divided into 3 aliquots. An aliquot containing one million of progressively motile spermatozoa was incubated for an hour (37°C) in standard culture medium (control group), and two aliquots with the same number of progressively motile spermatozoa were incubated in medium supplemented with IGF-I or NGFβ. Two concentrations of IGF-I (100 ng/ml and 1000 ng/ml) and NGFβ (0,5 ng/ml and 5 ng/ml) were tested.

Results

Both growth factors significantly increased PM and vitality in comparison with control either at the low or the high concentration. IGF-I seemed to be more effective than NGFβ. The effects did not seem to be dose dependent with the exception of the effect of IGF-I on vitality.

Conclusions

The enhancement of PM and vitality of human spermatozoa by IGF-I and NGFβ opens new ways for the improvement of sperm processing. Further research is needed to determine the most effective concentrations.
  相似文献   
33.
34.
Computerization of the medical record allows the unique capability to provide differential access to various components of the record by users outsid of the immediate provider/patient health care setting Guidelines for designers, programmers, and users of computerizeid medical records have been defined in order to clarify which data elements or categories are appropriate for communication to various parties involved in utilizing patients information.  相似文献   
35.
36.
Compound A (3-[2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]naphthyrindin-2-yl)propyl]-imidazolidin-1-yl]-3(S)-(6-methoxy-pyridin-3-yl)-propionic acid), a potent and selective antagonist of integrin alpha(v)beta(3) receptor, is under development for treatment of osteoporosis. This study describes metabolism and excretion of A in vivo in rats, dogs, and monkeys, and metabolism of A in vitro in primary hepatocytes from rats, dogs, monkeys, and humans. In all three animal species studied, A was primarily excreted as unchanged drug and, to a lesser degree, as phase I and phase II metabolites. Major biotransformation pathways of A included glucuronidation/glucosylation on the carboxylic group to form acyl-linked glucuronides/glucosides; and oxidation on the tetrahydronaphthyridine moiety to generate a carbinolamine and its further metabolized products. Minor pathways involved O-demethylation and hydroxylations on the alkyl chain. Only in rats, a glutathione adduct of A was also observed, and its formation is proposed to be via an iminium intermediate on the tetrahydronaphthyridine ring. Similar metabolic pathways were observed in the incubates of hepatocytes from the corresponding animals as well as from humans. CYP 3A and 2D subfamilies were capable of metabolizing A to its oxidative products. Overall, these in vitro and in vivo findings should provide useful insight on possible biotransformation pathways of A in humans.  相似文献   
37.
A 39-year-old female previously treated with shock wave lithotripsy developed extensive ureteral stricture disease. After 2 unsuccessful attempts at retrograde balloon dilatation, she was evaluated at our center for further management. Successful reconstruction was performed with laparoscopic-assisted vesicocalicostomy.  相似文献   
38.
The purpose of this article is to review recent dental literature dealing with the association between occlusal factors and functional disturbances of the masticatory system. There has been much controversy among various authors about the role of occlusion in mandibular dysfunction.

Studies on the number of teeth and the state of the dentition have shown no distinct patterns in patients with mandibular dysfunction. This can probably be explained by the existence of a wide range of individual adaptability to occlusal conditions. In most studies only weak correlations, if any, have been found between occlusal interferences and mandibular dysfunction. This article reviews clinical, electromyographic, experimental, and epidemiologic studies for such possible consequences.

The findings of our study lend support to the idea that the etiology of mandibular dysfunction is multifactorial. Occlusal factors generally seem to be of minor importance. It is thus probable that extensive occlusal rehabilitation is not necessary, at least in the initial phase, for treatment of mandibular dysfunction.  相似文献   
39.
Previous research has identified two subgroups of patients with Alzheimer's disease (AD) based on performance discrepancies on semantic and visual-constructional measures: Left AD (LAD) and Right AD (RAD). In this study, verbal fluency performances (Animal Fluency [AF] and Letter Fluency [FAS]) of these two subgroups were examined. It was hypothesized that LAD patients would perform worse on AF compared to FAS, due to an underlying breakdown of left-hemisphere semantic networks. On the other hand, the RAD group, which theoretically has a relatively preserved semantic system, yet difficulties retrieving overlearned information, was not expected to differ on the two fluency tasks. These predictions were based on the notion that the AF task requires intact retrieval and semantic processes, whereas the FAS task is reliant on retrieval processes alone. Patients were classified into subgroups on the basis of performance discrepancies on the Boston Naming Test (BNT) and Copy tasks: LAD (BNT<Copy); RAD (BNT>Copy). A split-plot ANOVA using demographically corrected standard T-scores revealed a significant main effect for fluency task, and a significant subgroup×fluency task interaction. LAD patients performed poorer on AF compared to FAS; there was no fluency task difference for the RAD group. Analysis of within-subcategory response clustering on AF revealed more instances of serial subclass exemplar responses by RAD members. These results support the loss theory in explaining the semantic deficit of LAD, and suggest that retrieval difficulties underlie the fluency problems of RAD.  相似文献   
40.
Calcium ions (Ca2+) are indispensable for the physiology of organisms and the molecular regulation of cells. We observed that CGK733, a synthetic chemical substance, induced non-apoptotic cell death and stimulated reversible calcium sequestration by vesicles in pancreatic cancer cells. The endoplasmic reticulum (ER) stress eukaryotic translation initiation factor 2-alpha kinase 3/C/EBP homologous protein (PERK/CHOP) signaling pathway was shown to be activated by treatment with CGK733. Ionomycin, an ER stress drug and calcium ionophore, can activate PERK/CHOP signaling and accelerate CGK733-induced calcium sequestration. Knockdown of CHOP diminished CGK733-induced vesicular calcium sequestration, but had no effects on the cell death. Proteomic analysis demonstrated that the ER-located calcium-binding proteins, calumenin and protein S100-A11, were altered in CGK733-treated cells compared to non-treated controls. Our study reveals that CGK733-induced intracellular calcium sequestration is correlated with the PERK/CHOP signaling pathway and may also be involved in the dysregulations of calcium-binding proteins.  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