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   14693篇
  免费   1134篇
  国内免费   41篇
耳鼻咽喉   83篇
儿科学   406篇
妇产科学   201篇
基础医学   1957篇
口腔科学   284篇
临床医学   1551篇
内科学   2833篇
皮肤病学   157篇
神经病学   1449篇
特种医学   574篇
外科学   2006篇
综合类   146篇
一般理论   32篇
预防医学   1777篇
眼科学   243篇
药学   1052篇
中国医学   20篇
肿瘤学   1097篇
  2024年   11篇
  2023年   140篇
  2022年   214篇
  2021年   484篇
  2020年   292篇
  2019年   407篇
  2018年   466篇
  2017年   361篇
  2016年   386篇
  2015年   462篇
  2014年   558篇
  2013年   784篇
  2012年   1185篇
  2011年   1160篇
  2010年   717篇
  2009年   600篇
  2008年   1023篇
  2007年   985篇
  2006年   927篇
  2005年   914篇
  2004年   852篇
  2003年   795篇
  2002年   669篇
  2001年   169篇
  2000年   105篇
  1999年   113篇
  1998年   128篇
  1997年   114篇
  1996年   96篇
  1995年   71篇
  1994年   73篇
  1993年   54篇
  1992年   57篇
  1991年   52篇
  1990年   45篇
  1989年   32篇
  1988年   25篇
  1987年   31篇
  1986年   25篇
  1985年   28篇
  1984年   29篇
  1983年   22篇
  1982年   28篇
  1981年   21篇
  1980年   15篇
  1979年   24篇
  1978年   20篇
  1977年   14篇
  1974年   12篇
  1972年   11篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
Guidelines urge general practitioners (GPs) to discuss smoking with patients as frequently as possible. Using data collected before and after consultations, this study confirms that GPs are more likely to discuss smoking in the context of smoking-related problems. Encouraging GPs to make greater use of problem-orientated opportunities to discuss smoking may have more effect on rates of advice giving than urging them to advise all smokers.  相似文献   
52.
Extracellular superoxide dismutase (EC-SOD) controls the availability of extracellular superoxide (O 2 - ), which is important for a variety of physiological pathways, including the primary means of inactivating nitric oxide (NO). The role of EC-SOD in neurobehavioral function has been until now unexplored. In the current studies, the phenotypic expression of genotypic alterations of EC-SOD production in mice were characterized for spatial learning and memory. Dramatic impairments in spatial learning in the win-shift 8-arm radial maze were seen in both EC-SOD knockout mice and EC-SOD overexpressing mice. The EC-SOD overexpressing mice were further characterized as having significant deficits in a repeated acquisition task in the radial-arm maze, which permitted the dissociation of long and short-term learning. Long-term learning was significantly impaired by EC-SOD overexpression, whereas short-term learning was not significantly affected by EC-SOD overexpression. NO systems have been shown to be importantly involved in learning and memory. This may be important in the current studies because EC-SOD has primary control over the inactivation of NO. We found that EC-SOD overexpressing mice were resistant to the cognitive effects of L-NAME (NG-nitro-L-arginine methyl ester hydrochloride), an NO synthase inhibitor. Decreased NO catabolism in these mice may have served to counter the effects of NOS inhibition by L-NAME. The current finding that EC-SOD levels that were either higher or lower than controls impaired learning demonstrates that the proper control of brain extracellular (O 2 - ) may be more vital than merely reduction of brain extracelluar (O 2 - ) in maintaining adequate learning function.  相似文献   
53.
54.
This paper describes the outcomes of episodes of care for adults in public sector mental health services across Australia, with a view to informing the debate on service quality. Health of the Nation Outcome Scales (HoNOS) change scores and effect sizes were calculated for 14,659 acute inpatient episodes and 23,692 community episodes. The results showed that people in contact with public sector mental health services generally do get better, although the magnitude of improvement depends on the setting and episode type. This confirmatory finding is particularly positive, given current community concerns about the quality and effectiveness of mental health services.  相似文献   
55.
BACKGROUND: Herpesviruses are a significant cause of human morbidity. Traditional approaches to the identification of these viruses require infectious or at least antigenic virus. Multiplex PCR (mPCR) is capable of simultaneously amplifying a range of targets from a single preparation of nucleic acids and when combined with a suitable detection assay, it is capable of discriminating each of the amplicons. OBJECTIVES: Several methods have been described in the literature, however, they lack one or more significant design features required to suitably control a routinely applied nucleic acid amplification assay. We aimed to design a multiplex herpesvirus PCR that could co-amplify eight human herpesvirus targets plus an internal control (IC) molecule in a single tube. STUDY DESIGN: Primers were designed to target the DNA polymerase genes of each of the human herpesviruses. Synthetic controls were developed to act as templates for the evaluation of assay sensitivity and specificity and for development of an in-house competitive quantitative PCR. Amplicon was discriminated using a simplified enzyme linked amplicon hybridisation assay (ELAHA). RESULTS AND CONCLUSIONS: For routine diagnostic use we reduced the number of herpesviral targets from 8 to 6 in order to maintain adequate clinical sensitivity. The ELAHA proved more sensitive than agarose gel electrophoresis. Additionally, 36 cytomegalovirus positive patients were examined with an in-house quantitative PCR-ELAHA which was developed to confirm that that the mPCR's co-detection limit of 10(2) copy of synthetic template per millilitre was relevant for use in detecting virus from clinical samples. The mPCR-ELAHA was then applied to the screening of 174 patient specimens resulting in a specificity of 98% and a sensitivity of 93%. This preliminary study demonstrated that the mPCR-ELAHA was a complete approach to the detection of herpesviruses from a range of clinical samples and disease states.  相似文献   
56.
57.
Autocrine motility factor (AMF) is one of the motility cytokines regulating tumor cell migration, therefore identification of the signaling pathway coupled with it has critical importance. Previous studies revealed several elements of this pathway predominated by lipoxygenase-PKC activations but the role for tyrosine kinases remained questionable. Motility cytokines frequently have mitogenic effect as well, producing activation of overlapping signaling pathways therefore we have used B16a melanoma cells as models where AMF has exclusive motility effect. Our studies revealed that in B16a cells AMF initiated rapid (1–5 min) activation of the protein tyrosine kinase (PTK) cascade inducing phosphorylation of 179, 125, 95 and 40/37 kD proteins which was mediated by upstream cyclo- and lipoxygenases. The phosphorylated proteins were localized to the cortical actin-stress fiber attachment zones in situ by confocal microscopy. On the other hand, AMF receptor activation induced significant decrease in overall serine-phosphorylation level of cellular proteins accompanied by serine phosphorylation of 200, 90, 78 and 65 kd proteins. The decrease in serine phosphorylation was independent of PTKs, PKC as well as cyclo- and lipoxygenases. However, AMF induced robust translocation of PKCα to the stress fibers and cortical actin suggesting a critical role for this kinase in the generation of the motility signal. Based on the significant decrease in serine phosphorylation after AMF stimulus in B16a cells we postulated the involvement of putative serine/threonine phosphatase(s) upstream lipoxygenase and activation of the protein tyrosine kinase cascade downstream cyclo- and lipoxygenase(s) in the previously identified autocrine motility signal. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
58.
59.
We measured brain activity using magnetoencephalography in five participants during ongoing tasks that included prospective memory, retrospective memory, and oddball trials. Sources were identified in the hippocampal formation and posterior parietal and frontal lobes. Posterior parietal cortex activation had an earlier onset in the prospective memory condition than retrospective memory or oddball conditions, a higher level of theta activity in the retrospective condition, and higher levels of upper alpha in the prospective and oddball conditions. Activation of the hippocampal formation had a longer duration in the retrospective memory and prospective memory conditions than the oddball condition, but prominent alpha and theta band activity was present in all three conditions. We interpret the early (87 ms) onset of activity in parietal cortex as evidence for an initial noticing of appropriate conditions for a PM response. Hippocampal activity may reflect a subsequent memory search for the intended action.  相似文献   
60.
The B cell line 721.174 has lost the ability to present intracellular antigens to major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes (CTL). This phenotype results from a homozygous deletion in the MHC that includes the peptide transporter genes TAP1 and TAP2, and the proteasome subunits LMP2 and LMP7. Recent work has shown that such cells transfected with TAP genes load their class I molecules with endogenous peptides, and present several viral epitopes to class I-restricted CTL. These data implied that the LMP2 and LMP7 genes were not required for the presentation of most epitopes through class I molecules. By contrast, while confirming the previous reports, we have identified several epitopes that appear to require genes in the MHC in addition to the TAP for their presentation. Further analysis localizes the defect to proteolysis in the cytosol. In one case, presentation could be partially restored by re-expression of full-length LMP7. Control experiments with LMP7, from which the putative pro-region had been removed, failed to restore presentation, and this lack of effect correlated with failure of the shortened LMP7 to incorporate into the proteasome. These results suggest a role for LMP7 in the generation of a viral epitope, but leave open the possibility that additional genes within the .174 deletion are required for full restoration of antigen presentation.  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