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   2431篇
  免费   109篇
  国内免费   9篇
耳鼻咽喉   52篇
儿科学   66篇
妇产科学   24篇
基础医学   297篇
口腔科学   173篇
临床医学   286篇
内科学   401篇
皮肤病学   15篇
神经病学   267篇
特种医学   87篇
外科学   282篇
综合类   10篇
一般理论   3篇
预防医学   177篇
眼科学   40篇
药学   297篇
肿瘤学   72篇
  2023年   13篇
  2022年   28篇
  2021年   40篇
  2020年   24篇
  2019年   34篇
  2018年   40篇
  2017年   48篇
  2016年   50篇
  2015年   49篇
  2014年   82篇
  2013年   152篇
  2012年   128篇
  2011年   150篇
  2010年   96篇
  2009年   99篇
  2008年   160篇
  2007年   168篇
  2006年   152篇
  2005年   168篇
  2004年   156篇
  2003年   145篇
  2002年   151篇
  2001年   32篇
  2000年   25篇
  1999年   29篇
  1998年   35篇
  1997年   21篇
  1996年   20篇
  1995年   16篇
  1994年   16篇
  1993年   17篇
  1992年   13篇
  1991年   17篇
  1990年   16篇
  1989年   14篇
  1988年   16篇
  1987年   11篇
  1986年   12篇
  1985年   10篇
  1984年   20篇
  1983年   7篇
  1982年   8篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   3篇
  1977年   15篇
  1976年   6篇
  1975年   3篇
  1973年   3篇
排序方式: 共有2549条查询结果,搜索用时 0 毫秒
1.
ObjectiveSpinal cord stimulation (SCS) is an effective treatment in failed back surgery syndrome (FBSS). We studied the effect of preimplantation opioid use on SCS outcome and the effect of SCS on opioid use during a two-year follow-up period.Materials and methodsThe study cohort included 211 consecutive FBSS patients who underwent an SCS trial from January 1997 to March 2014. Participants were divided into groups, which were as follows: 1) SCS trial only (n = 47), 2) successful SCS (implanted and in use throughout the two-year follow-up period, n = 131), and 3) unsuccessful SCS (implanted but later explanted or revised due to inadequate pain relief, n = 29). Patients who underwent explantation for other reasons (n = 4) were excluded. Opioid purchase data from January 1995 to March 2016 were retrieved from national registries.ResultsHigher preimplantation opioid doses associated with unsuccessful SCS (ROC: AUC = 0.66, p = 0.009), with 35 morphine milligram equivalents (MME)/day as the optimal cutoff value. All opioids were discontinued in 23% of patients with successful SCS, but in none of the patients with unsuccessful SCS (p = 0.004). Strong opioids were discontinued in 39% of patients with successful SCS, but in none of the patients with unsuccessful SCS (p = 0.04). Mean opioid dose escalated from 18 ± 4 MME/day to 36 ± 6 MME/day with successful SCS and from 22 ± 8 MME/day to 82 ± 21 MME/day with unsuccessful SCS (p < 0.001).ConclusionsHigher preimplantation opioid doses were associated with SCS failure, suggesting the need for opioid tapering before implantation. With continuous SCS therapy and no explantation or revision due to inadequate pain relief, 39% of FBSS patients discontinued strong opioids, and 23% discontinued all opioids. This indicates that SCS should be considered before detrimental dose escalation.  相似文献   
2.
Chymases (EC 3.4.21.39) are mast cell serine proteinases that are variably expressed in different species and, in most cases, display either chymotryptic or elastolytic substrate specificity. Given that chymase inhibitors have emerged as potential therapeutic agents for treating various inflammatory, allergic, and cardiovascular disorders, it is important to understand interspecies differences of the enzymes as well as the behavior of inhibitors with them. We have expressed chymases from humans, macaques, dogs, sheep (MCP2 and MCP3), guinea pigs, and hamsters (HAM1 and HAM2) in baculovirus-infected insect cells. The enzymes were purified and characterized with kinetic constants by using chromogenic substrates. We evaluated in vitro the potency of five nonpeptide inhibitors, originally targeted against human chymase. The inhibitors exhibited remarkable cross-species variation of sensitivity, with the greatest potency observed against human and macaque chymases, with Ki values ranging from ∼0.4 to 72 nM. Compounds were 10-300-fold less potent, and in some instances ineffective, against chymases from the other species. The X-ray structure of one of the potent phosphinate inhibitors, JNJ-18054478, complexed with human chymase was solved at 1.8 Å resolution to further understand the binding mode. Subtle variations in the residues in the active site that are already known to influence chymase substrate specificity can also strongly affect the compound potency. The results are discussed in the context of selecting a suitable animal model to study compounds ultimately targeted for human chymase.  相似文献   
3.
4.
BACKGROUND: Atherosclerosis begins early in life. Infections might contribute to the pathogenesis of atherosclerosis. In this study, we investigated whether acute infections in children could alter the carotid wall morphology and the lipid profile. METHODS: Mean carotid intima-media thickness (IMT) was measured by high-resolution ultrasound in 28 hospitalised children (mean age: 5+/-2 years), who fulfilled the diagnostic criteria of acute infections (body temperature, >38 degrees C; C-reactive protein, >15mg/ml, and clinical), and in 20 age- and gender-matched controls. Antibodies against oxidised low-density lipoprotein (anti-oxLDL antibodies), as well as total and high-density lipoprotein cholesterol (HDL-C) were analysed in all children. The infection group was investigated both during the acute illness and 3 months after clinical recovery (post-infection). RESULTS: During the acute illness, the infection group had elevated anti-oxLDL antibodies and decreased HDL-C, as compared to those obtained at 3 months and in controls (p<0.05). These changes in the infection group were followed, at 3 months, by thickening of carotid intima-media. Those who received antibiotics during their acute illness had less carotid thickening than those who were not treated with antibiotics (p<0.05). CONCLUSION: Acute infections in children seem to be accompanied by enhanced oxidative modification of LDL and by decrease in HDL-C. These lipid changes may be followed by thickening of carotid artery intima-media. These findings suggest that, in childhood, acute infections could be associated with increased risk of atherosclerosis, and warrant further studies on this topic.  相似文献   
5.
6.
The aim of this study was to assess the periodontal treatment needs at under 20 yr of age in the affluent area of Espoo, Finland, offering comprehensive public dental health care, as compared to a less advantaged area in Chiangmai, Thailand. In Espoo, 50 girls and 50 boys were examined in each age group of 7, 12 and 17 yr. In Chiangmai equal numbers of girls and boys were examined to obtain a group of 89 subjects aged 18.5 + 0.6 yr. According to the Community Periodontal Index of Treatment Needs (CPITN) the need of scaling increased in Espoo from 6% of the 7-yr-olds to 39% of the 17-yr-olds. Moderate pocketing (4-5 mm) occurred in one subject at age 12 and in three subjects at age 17. In Chiangmai, deep pockets (6 mm and over) were recorded for 1%, moderate pockets for a total of 44%, and dental calculus as the highest treatment need indicator in the remaining 55%, indicating a need for professional treatment in 100% of the group examined. The mean number of sextants requiring scaling was 0.6 per person at age 17 in Espoo as compared to 4.5 at 18.5 yr of age in Chiangmai. Three or more healthy sextants per subject were recorded for 47% of the 17-yr-olds in Espoo and for only 6% of the 18.5-yr-olds in Chiangmai. It was concluded that already at young age vast differences occur between periodontal treatment needs in industrialized and developing countries.  相似文献   
7.
Even though the roles of different known or suggested prognostic factors in laryngeal cancer have been studied in detail, clinical stage at time of diagnosis and anatomic subsite of the tumour remain the only practical predictors of clinical outcome and offer the only guidelines in the planning of treatment. In this study, the relative roles of known demographic and clinical prognostic factors, in addition to four histopathological factors, were evaluated in a sample of 100 laryngeal carcinoma patients with multivariate analysis using the Cox regression model. In addition to advanced stage (stage III-IV) (relative hazard of death (HR) 8.9, p=0.01) and supraglottic disease (HR 5.6, p=0.02), high apoptotic index (HR 11.1, p=0.05) was significantly associated with poor survival. Cell proliferation, p53 and angiogenesis did not significantly affect the prognosis. In the future, high degree of apoptosis could be used to identify patients with poor prognosis in laryngeal cancer.  相似文献   
8.
We investigated muscle strength, aerobic power, and occupational and leisure-time physical loading as predictors of back pain in a 5-year follow-up study. A cohort of 456 adults aged 25, 35, 45 and 55 years, free of back pain, participated in measurements of anthropometric characteristics, aerobic power and muscle strength characteristics at baseline. The subjects' levels and types of physical activity and occupational physical loading were also determined. At 5 years after the baseline examinations 356 of these subjects (78.1 %) were reached by mail, and 262 of them (73.6%) properly completed and returned a questionnaire including a detailed back pain history for the 5 years following the baseline measurements. Of this number 56 subjects (21 %) who reported back pain ( > 30 on a scale from 0 to 100) and functional impairment during the 5-year follow-up composed the marked back pain group. Other subjects (n = 71, 27%) noting lesser symptoms were included in the mild back pain group; 135 subjects (52%) reported having had no back pain. The subjects with marked back pain were on average taller than the subjects without back pain, while no such difference was found in body mass. Heavy occupational musculoskeletal loading (P = 0.005) and high general occupational physical demands (P = 0.036) predicted future back pain. Leisuretime physical activity, aerobic power or muscle strength characteristics were not predictive of future back pain.  相似文献   
9.
Dendritic cells (DCs) are the most efficient antigen-presenting cells and thus, have a major role in regulating host immune responses. In the present study, we have analyzed the ability of Gram-positive, pathogenic Streptococcus pyogenes and nonpathogenic Lactobacillus rhamnosus to induce the maturation of human monocyte-derived DCs. Stimulation of DCs with S. pyogenes resulted in strong expression of DC costimulatory molecules CD80, CD83, and CD86 accompanied with a T helper cell type 1 (Th1) cytokine and chemokine response. S. pyogenes also induced interleukin (IL)-2 and IL-12 production at mRNA and protein levels. In addition, IL-23 and IL-27 subunits p40, p19, p28, and EBI3 were induced at mRNA level. In contrast, L. rhamnosus-stimulated DCs showed only moderate expression of costimulatory molecules and produced low levels of cytokines and chemokines. Furthermore, no production of IL-2 or IL-12 family cytokines was detected. Bacteria-induced DC maturation and especially cytokine and chemokine production were reduced when bacteria were heat-inactivated. Our results show that human monocyte-derived DCs respond differently to different Gram-positive bacteria. Although pathogenic S. pyogenes induced a strong Th1-type response, stimulation with nonpathogenic L. rhamnosus resulted in development of semi-mature DCs characterized by moderate expression of costimulatory molecules and low cytokine production.  相似文献   
10.
Recent studies reported differential information in human magnetocardiogram and in electrocardiogram. Vortex currents have been discussed as a possible source of this divergence. With the help of physical phantom experiments, we quantified the influence of active vortex currents on the strength of electric and magnetic signals, and we tested the ability of standard source localization algorithms to reconstruct vortex currents. The active vortex currents were modeled by a set of twelve single current dipoles arranged in a circle and mounted inside a phantom that resembles a human torso. Magnetic and electric data were recorded simultaneously while the dipoles were switched on stepwise one after the other. The magnetic signal strength increased continuously for an increasing number of dipoles switched on. The electric signal strength increased up to a semicircle and decreased thereafter. Source reconstruction with unconstrained focal source models performed well for a single dipole only (less than 3-mm localization error). Minimum norm source reconstruction yielded reasonable results only for a few of the dipole configurations. In conclusion active vortex currents might explain, at least in part, the difference between magnetically and electrically acquired data, but improved source models are required for their reconstruction.  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