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   309篇
  免费   41篇
  国内免费   2篇
耳鼻咽喉   32篇
儿科学   6篇
妇产科学   1篇
基础医学   68篇
临床医学   25篇
内科学   63篇
皮肤病学   4篇
神经病学   31篇
特种医学   6篇
外科学   13篇
综合类   8篇
预防医学   22篇
眼科学   2篇
药学   60篇
肿瘤学   11篇
  2021年   5篇
  2019年   2篇
  2018年   2篇
  2017年   2篇
  2016年   5篇
  2015年   3篇
  2014年   6篇
  2013年   9篇
  2012年   10篇
  2011年   18篇
  2010年   5篇
  2009年   8篇
  2008年   14篇
  2007年   11篇
  2006年   21篇
  2005年   23篇
  2004年   11篇
  2003年   20篇
  2002年   18篇
  2001年   13篇
  2000年   13篇
  1999年   14篇
  1998年   5篇
  1997年   5篇
  1996年   2篇
  1995年   5篇
  1994年   1篇
  1993年   3篇
  1992年   10篇
  1991年   2篇
  1990年   5篇
  1989年   2篇
  1988年   10篇
  1987年   6篇
  1986年   9篇
  1985年   9篇
  1984年   4篇
  1983年   4篇
  1982年   2篇
  1981年   1篇
  1980年   8篇
  1979年   7篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1974年   1篇
  1972年   1篇
  1970年   2篇
  1969年   2篇
排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
2.
Depressed patients were interviewed at two different severity levels in the course of their illness about both problematic and neutral topics, and their speech behavior was analyzed in terms of speech activity and silences. Lowered speech activity and increased silences occurred at higher severity levels and also during problematic communication content, suggesting the mediation of cognitive factors as postulated by Beck's cognitive model of depression.  相似文献   
3.
The changes in serum trypsin concentration have been measured in 47 subjects for up to 2 hours after a Lundh meal. In 18 healthy controls, mean fasting trypsin concentration was 285 +/- 125 ng/ml (mean +/- 2 SD). The maximum increase after the Lundh meal (the trypsin response ratio) was 6.7 +/- 7.5%. Six patients with chronic renal failure had elevated fasting serum trypsin concentrations (range 460-1100 ng/ml) but trypsin response ratios fell within the control range. Of five patients with relapsing pancreatitis, two had raised and three normal or low fasting trypsins. After stimulation two had elevated trypsin response ratios; one of the two had evidence of main duct obstruction. Eleven out of 12 patients with chronic pancreatitis (with or without insufficiency) had low fasting trypsin concentrations (range 0-120 ng/ml) Seven of the 12 also had raised trypsin response ratios. In six patients with cancer of the pancreas, fasting trypsin was low in three, normal in two, and raised in one. Both patients with a normal fasting level had a raised trypsin response ratio. The combination of a single estimation of fasting serum trypsin concentration followed by serial measurements after a Lundh meal provides a useful screening test for chronic pancreatic disease.  相似文献   
4.
Classical swine fever virus (CSFV) is a noncytopathogenic (ncp) positive-sense RNA virus that replicates in myeloid cells including macrophages and dendritic cells (DC). The virus does not induce type I interferon (IFN-alpha/beta), which in macrophages has been related to the presence of the viral Npro gene. In the present work, the role of viral double-stranded (ds)RNA and Npro in the virus-host cell interaction has been analyzed. Higher levels of detectable dsRNA were produced by a genetically engineered cytopathogenic (cp) CSFV compared with ncp CSFV, and cp CSFV induced IFN-alpha/beta in PK-15 cells. With DC, there was only a small difference in the levels of dsRNA between the cp and ncp viruses, and no IFN-alpha/beta was produced. However, the cp virus induced a higher degree of DC maturation, in terms of CD80/86 and MHC II expression. Npro deletion mutants induced an increase in DC maturation and IFN-alpha/beta production-for both ncp and cp viruses-despite reduced replication efficiency in the DC. Deletion of Npro did not influence dsRNA levels, indicating that the interference was downstream of dsRNA turnover regulation. In conclusion, the capacity of CSFV to replicate in myeloid DC, and prevent IFN-alpha/beta induction and DC maturation, requires both regulated dsRNA levels and the presence of viral Npro.  相似文献   
5.
General models are developed for static and dynamic geometric and material passive responses. The models are applied to data obtained from the main pulmonary arteries of calves and dogs. The structural model predicts distortions by simultaneous stretching and bending in a concise manner. Parameters are obtained by a fiveelement material model. This latter predicts static and dynamic, nonlinear, frequency-dependent, viscoelastic responses observed in biomaterials over the entire strain range irrespective of the nature of loading. Validity and baseline parameter values are investigated for the inactivated state, developed by poisoning the smooth muscle with potassium cyanide. Complexities, related to nonlinear (strain-dependent) and colloidal (thixotropic) properties of tissues, are analyzed. These properties enter into functional responses in a complex manner that can modify substantially concepts of material components and vary appreciably between physiologic circumstances and laboratory evaluations. We propose that, in general, evaluations of material responses must account for these properties.  相似文献   
6.
7.
8.
This seventh best-practice review examines four series of common primary care questions in laboratory medicine: (1) blood count abnormalities 2; (2) cardiac troponins; (3) high-density lipoprotein cholesterol; and (4) viral diseases 2. The review is presented in a question-answer format, with authorship attributed for each question series. The recommendations are a précis of guidance found using a standardised literature search of national and international guidance notes, consensus statements, health policy documents and evidence-based medicine reviews, supplemented by Medline Embase searches to identify relevant primary research documents. The recommendations are not standards, but form a guide to be set in the clinical context. Most are consensus based rather than evidence based. They will be updated periodically to take account of new information.  相似文献   
9.
Two-dimensional covalent organic frameworks (2D-COFs) have been of increasing interest in the past decade due to their porous structures that ideally can be highly ordered. One of the most common routes to these polymers relies on Schiff-base chemistry, i.e., the condensation reaction between a carbonyl and an amine. In this report, we elaborate on the condensation of 3,6-dibromobenzene-1,2,4,5-tetraamine with hexaketocyclohexane (HKH) and the subsequent carbonylation of the resulting COF, along with the possibility that the condensation reaction on HKH can result in a trans configuration resulting in the formation of a disordered 2D-COF. This strategy enables modification of COFs via bromine substitution reactions to place functional groups within the pores of the materials. Ion-sieving measurements using membranes from this COF, reaction of small molecules with unreacted keto groups along with modeling studies indicate disorder in the COF polymerization process. We also present a Monte Carlo simulation that demonstrates the influence of even small amounts of disorder upon both the 2D and 3D structure of the resulting COF.  相似文献   
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