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   273篇
  免费   16篇
耳鼻咽喉   2篇
儿科学   23篇
妇产科学   4篇
基础医学   47篇
口腔科学   9篇
临床医学   31篇
内科学   29篇
神经病学   35篇
外科学   19篇
综合类   2篇
预防医学   45篇
眼科学   1篇
药学   42篇
  2022年   4篇
  2020年   7篇
  2019年   8篇
  2018年   7篇
  2017年   5篇
  2016年   8篇
  2015年   8篇
  2014年   12篇
  2013年   16篇
  2012年   16篇
  2011年   19篇
  2010年   10篇
  2009年   7篇
  2008年   14篇
  2007年   14篇
  2006年   9篇
  2005年   11篇
  2004年   12篇
  2003年   7篇
  2002年   5篇
  2001年   13篇
  2000年   6篇
  1999年   8篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1992年   3篇
  1991年   2篇
  1990年   4篇
  1989年   4篇
  1988年   4篇
  1987年   5篇
  1986年   1篇
  1985年   4篇
  1984年   6篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1975年   3篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1969年   1篇
  1942年   1篇
  1940年   1篇
  1939年   1篇
排序方式: 共有289条查询结果,搜索用时 0 毫秒
1.
Irradiation of a cytosolic fraction from vascular smooth muscle in the presence of [3H]felodipine resulted in the labelling of a protein with an apparent molecular weight of 62 kDa. The labelling was seen on UV-irradiation at 360 nm, but not at 254, 278 or at wavelengths above 410 nm. The photolabelling was enhanced in the absence of oxygen. In cytosolic fractions prepared from porcine liver, cardiac and skeletal muscle no photoaffinity labelling of proteins between 90 and 45 kDa could be demonstrated. The results suggest that felodipine is a photoaffinity ligand and that felodipine binds to a soluble protein present in vascular smooth muscle but not in the other tissues tested.  相似文献   
2.
We describe a fluorescence method for screening and quantifying urinary porphyrins. New and effective approaches are used to oxidize prophyrinogens, correct the baseline, and ensure that uroporphyrin (uro) and coproporphyrin (copro) are equally detected, mole for mole. No preliminary purification is required. A 45-microL aliquot of urine is oxidized with 3 mmol/L iodine in 3 mol/L HCl to convert porphyrinogens to porphyrins, and then decolorized with 5 mL of 0.45 mmol/L sodium thiosulfate. An excitation scan is done from 350 nm to 440 nm, monitoring emission at 650 nm. Total porphyrin content is determined at the isosbestic point for uro and copro, and the mole fractions of uro and copro are estimated from the wavelength of the signal maximum. There is no interference from protein, glucose, bilirubin, or hemoglobin in high concentration. The limit of detection is less than 30 nmol/L and linearity is maintained up to 3200 nmol/L. Recoveries and precision are excellent. This is a rapid, sensitive screen for porphyrinuria as well as an accurate and precise quantitative method. We compared the method with existing methods and discuss some shortcomings common to many of them.  相似文献   
3.
We studied domains in the human bladder that acted as receptors for Escherichia coli P, S, type 1, type 1C, and O75X fimbriae or adhesin and domains in the human kidneys that were receptors for E. coli type 1C fimbriae. Binding sites in frozen tissue sections were localized by direct staining with fluorochrome-labeled recombinant strains and by indirect immunofluorescence with the purified adhesins. In the bladder, the P and S fimbriae showed closely similar binding to the epithelial and muscular layers, and the S fimbriae also bound to the connective tissue elements. Type 1 fimbriae bound to vascular walls and to muscle cells, whereas the O75X adhesin bound avidly to connective tissue elements and to some extent to epithelial and muscle cells of the bladder. The type 1C fimbriae bound to distal tubules and collecting ducts of the kidney and to vascular endothelial cells in both the kidney and bladder. The binding of all adhesin types was inhibited by specific receptor analogs or Fab fragments. The results reveal a possible mechanism by which the type 1C fimbriae may help invasion of E. coli in the kidneys but do not support a pathogenetic role for type 1 fimbriae. Similar tissue specificity of P and S fimbriae in the human urinary tract indicates that the presence of binding sites on uroepithelia does not fully explain the virulence properties of P fimbriae in human urinary tract infections.  相似文献   
4.
The juxtaglomerular apparatus fulfils several important regulatory functions in the kidney, such as tubuloglomerular feedback (TGF) control and control of renin release. The macula densa (MD) cells sense the fluid load by perceiving the distal NaCl concentration via a Na-K-2Cl cotransport system in the luminal cell membrane. It has been proposed that macula densa cell activation may involve changes in intracellular cytosolic free calcium concentration ([Ca2+]i), as one link in the chain of events activating TGF or releasing renin. We therefore investigated the changes in the intracellular calcium concentrations with fura-2, using a video system, in macula densa cells, and compared them with the changes in the corresponding concentrations in the ascending limb of the loop of Henle (c-TAL). The results show that our technique for analysing intracellular cytosolic free calcium in isolated perfused tubules is valid for this purpose, and the Kd value obtained was similar to that found by Grynkiewicz et al. (1985). The intracellular cytosolic free calcium concentration was about 90 nM both in the macula densa and c-TAL cells, and the macula densa cell intracellular cytosolic free calcium concentration increased by about 20 nM when the tubular lumen was perfused with Na and Cl at low concentrations. No significant changes were noted when furosemide was added to the perfusion solutions. We consider it hardly likely that this small change in intracellular cytosolic free calcium concentration can be entirely responsible for full activation of renin release or full inactivation of the TGF control mechanism. It would seem that the signal transmission from the macula densa cells could occur by other routes than through activation of intracellular cytosolic free calcium concentration.  相似文献   
5.
GAP-43 is normally produced by neurons during developmental growth and axonal regeneration, but it is also expressed in specific regions of the normal adult nervous system. We studied the protein expression of GAP-43 within the conus medullaris portion of the spinal cord in adult male rats. Immunohistochemistry for choline acetyltransferase (ChAT) was first performed to identify specific efferent autonomic and motor nuclei in lumbosacral segments of the spinal cord. Adjacent sections were then processed for GAP-43 immunoreactivity (IR). We show GAP-43 IR in the superficial portion of the dorsal horn, the intermediolateral nucleus, and the dorsal commissural tract. We also demonstrate a differential distribution of GAP-43 IR between different motor nuclei of the conus medullaris. Using densitometry, the most prominent GAP-43 IR was detected in the dorsolateral and dorsomedial motor nuclei, which represent the human Onufs nucleus homologue. Confocal microscopy of double immunofluorescent labeling for ChAT and GAP-43 demonstrate GAP-43 IR in the neuropil of the autonomic and motor nuclei, and many of the GAP-43 IR arbors are in close apposition with the efferent cholinergic neurons. We note that the efferent neurons of both the autonomic and somatic nuclei, which are ultimately responsible for the integrated normal control of the lower urinary tract, bowel and sexual functions, are heavily innervated by GAP-43 enriched projections. We speculate that these functionally related neurons retain a physiological GAP-43-associated synaptic plasticity throughout adult life.  相似文献   
6.
Recovery is a crucial concept in the mental health field. The research of recovery is split into the categories of personal, social and clinical recovery. The purpose of this study was to explore the fragmented concept of recovery in light of assertive community treatment (ACT) in Norway. The study has a mixed methods design with a pragmatic approach. The Questionnaire about the Process of Recovery and open‐ended questions posed to 70 participants from 12 ACT teams in Norway, gathered by the “Users interview users” method, are combined with interviews or focus groups with eight of these participants. Surprisingly those under a community treatment order (CTO) report the highest degree of personal recovery. The qualitative material shows that the service users interpreted the concept of recovery differently than researchers and professionals. The ACT service users highlighted three important elements: flexible treatment, medication and access to a car. They emphasized the necessity for basic needs to be met in order to experience a meaningful recovery process, and these basic needs may be of even greater importance to those under CTOs. Their experiences should imply a greater emphasis on securing basic needs such as secure housing, sounder finances and access to the normal benefits offered by society.  相似文献   
7.

Aims/hypothesis

The aim of this multicohort study was to examine whether employees exposed to social stressors at work, such as workplace bullying and violence, have an increased risk of type 2 diabetes.

Methods

The study included 45,905 men and women (40–65 years of age and free of diabetes at baseline) from four studies in Sweden, Denmark and Finland. Workplace bullying and violence were self-reported at baseline. Incident diabetes was ascertained through national health and medication records and death registers. Marginal structural Cox models adjusted for age, sex, country of birth, marital status and educational level were used for the analyses.

Results

Nine per cent of the population reported being bullied at work and 12% were exposed to workplace violence or threats of violence. Bullied participants had a 1.46 (95% CI 1.23, 1.74) times higher risk of developing diabetes compared with non-bullied participants. Exposure to violence or threats of violence was also associated with a higher risk of diabetes (HR 1.26 [95% CI 1.02, 1.56]). The risk estimates attenuated slightly when taking BMI into account, especially for bullying. The results were similar for men and women, and were consistent across cohorts.

Conclusions/interpretation

We found a higher risk of incident type 2 diabetes among employees exposed to bullying or violence in the workplace. Further research is needed to determine whether policies to reduce bullying and violence at work may reduce the incidence of type 2 diabetes in working populations. Research on the mechanisms is also highly warranted.
  相似文献   
8.

Background

Coping has traditionally been measured with inventories containing many items meant to identify specific coping strategies. An alternative is to develop a shorter inventory that focusses on coping expectancies which may determine the extent to which an individual attempts to cope actively.

Purpose

This paper explores the usefulness and validity of a simplified seven-item questionnaire (Theoretically Originated Measure of the Cognitive Activation Theory of Stress, TOMCATS) for response outcome expectancies defined either as positive (“coping”), negative (“hopelessness”), or none (“helplessness”). The definitions are based on the Cognitive Activation Theory of Stress (CATS; Ursin and Eriksen, Psychoneuroendocrinology, 29(5):567–92, 2004). The questionnaire was tested in two different samples. First, the questionnaire was compared with a traditional test of coping and then tested for validity in relation to socioeconomic differences in self-reported health.

Methods

The first study was a comparison of the brief TOMCATS with a short version of the Utrecht Coping List (UCL; Eriksen et al., Scand J Psychol, 38(3):175–82, 1997). Both questionnaires were tested in a population of 1,704 Norwegian municipality workers. The second study was a cross-sectional analysis of TOMCATS, subjective and objective socioeconomic status, and health in a representative sample of the Swedish working population in 2003–2005 (N?=?11,441).

Results

In the first study, the coping item in the TOMCATS questionnaire showed an expected significant positive correlation with the UCL factors of instrumental mastery-oriented coping and negative correlations with passive and depressive scores. There were also the expected correlations for the helplessness and hopelessness scores, but there was no clear distinction between helplessness and hopelessness in the way they correlated with the UCL. In the second study, the coping item in TOMCATS and the three-item helplessness scores showed clear and monotonous gradients over a subjective socioeconomic status (SES) ladder. Positive response outcome expectancy (“coping”) was related to high subjective SES and no expectancy (“helplessness”) to low subjective SES. In a model including age and sex, TOMCATS scores explained more variance (r 2?=?0.16) in self-reported health than both subjective (r 2?=?0.08) and objective SES (r 2?=?0.02).

Conclusion

The brief TOMCATS questionnaire showed acceptable and significant correlations with a traditional coping questionnaire and is sensitive enough to register systematic differences in response outcome expectancies across the socioeconomic ladder. The results furthermore confirm that psychological and learning factors contribute to the socioeconomic gradient in health.  相似文献   
9.
10.
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