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   1450篇
  免费   182篇
  国内免费   22篇
耳鼻咽喉   4篇
儿科学   66篇
妇产科学   15篇
基础医学   184篇
口腔科学   46篇
临床医学   149篇
内科学   376篇
皮肤病学   29篇
神经病学   52篇
特种医学   228篇
外科学   103篇
综合类   63篇
一般理论   1篇
预防医学   153篇
眼科学   12篇
药学   109篇
中国医学   2篇
肿瘤学   62篇
  2022年   7篇
  2021年   11篇
  2020年   11篇
  2019年   15篇
  2018年   18篇
  2017年   17篇
  2016年   21篇
  2015年   22篇
  2014年   27篇
  2013年   32篇
  2012年   45篇
  2011年   58篇
  2010年   43篇
  2009年   41篇
  2008年   64篇
  2007年   39篇
  2006年   42篇
  2005年   40篇
  2004年   53篇
  2003年   32篇
  2002年   30篇
  2001年   40篇
  2000年   33篇
  1999年   27篇
  1998年   48篇
  1997年   51篇
  1996年   52篇
  1995年   45篇
  1994年   31篇
  1993年   38篇
  1992年   34篇
  1991年   31篇
  1990年   36篇
  1989年   39篇
  1988年   40篇
  1987年   64篇
  1986年   42篇
  1985年   36篇
  1984年   20篇
  1983年   29篇
  1982年   25篇
  1981年   33篇
  1980年   22篇
  1979年   16篇
  1978年   11篇
  1977年   15篇
  1976年   25篇
  1975年   18篇
  1974年   7篇
  1972年   8篇
排序方式: 共有1654条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE: To investigate patterns of drug use and injection-related risk behaviours among young Indo-Chinese injecting drug users (IDUs). METHOD: Cross-sectional survey. A structured questionnaire was administered to 184 Indo-Chinese IDUs aged 15 to 24 in Sydney and Melbourne. Participants were recruited using snowball sampling techniques; measures included patterns of heroin and other drug use, injection-related risk behaviours, perceived susceptibility to HIV and HCV infection and access to services. RESULTS: Despite perceived high availability of sterile injecting equipment, 36% had ever shared a needle and syringe and 22% had done so in the preceding month. Lifetime sharing was significantly associated with duration of injecting, history of incarceration and residence in Sydney. Sharing of injecting paraphernalia other than needles and syringes was also common, with young women and Sydney residents significantly more likely to report sharing equipment in the preceding month. CONCLUSIONS: Young Indo-Chinese IDUs are at high risk of infection with hepatitis C and other blood-borne viruses. Results indicate an urgent need for culturally appropriate and sustainable risk reduction programs which specifically target this population. Implications: Health services must respond swiftly to implement effective blood-borne virus prevention programs for young Indo-Chinese IDUs. Failure to do so may sustain the current epidemic of hepatitis C among IDUs.  相似文献   
92.
MUC1 expression in primary breast cancer: the effect of tamoxifen treatment   总被引:2,自引:0,他引:2  
This was a non-randomised single institution retrospective study. Forty-six banked frozen tumour specimens were obtained from a group of patients who had undergone 3 weeks of neoadjuvant treatment with tamoxifen between biopsy and surgery. Fifty-one comparison specimens were randomly selected from a group of concomitantly treated primary breast cancer patients who did not receive neoadjuvant tamoxifen. Specimen selection was not based on prognostic factors: hormone receptor status, patient age, or menopausal status. MUC1 expression and cell cycle distribution were assessed by flow cytometry. S-phase fraction of MUC1 positive and MUC1 negative cells were compared. A lower percentage of cells expressed MUC1 following 3-week tamoxifen treatment 18.2% versus 28.5% (p=0.03, Mann-Whitney) and lower levels of MUC1 expression were seen following tamoxifen treatment 31,519 molecules/cell versus 39,387 (p=0.04, Mann-Whitney). MUC1 positive cells, irrespective of treatment group, had a greater proportion of cells in S-phase of the cell cycle 27.9% versus 16.8% (p=0.0004, Mann-Whitney) and demonstrated more cases of aneuploidy 80.65% versus 42.6% (p<0.0001). MUC1 levels in primary tumours treated neoadjunctively with 3 weeks of tamoxifen were lower than a comparison group which did not receive tamoxifen. MUC1 should be explored further as an intermediate biomarker for assessment of treatment and prognosis.  相似文献   
93.
94.
Brunstrom JM  Downes CR  Higgs S 《Appetite》2001,37(3):197-206
Flavour preference learning in 21 restrained and 21 unrestrained females was explored using an evaluative conditioning paradigm. Each participant was exposed to an adapted version of the procedure used by Johnsrude et al., (1999, Learning & Motivation30, 250-264). During conditioning, participants sampled 10 instances each of three novel flavours presented in a semi-randomized order. After sampling a flavour they were instructed to eat a sweet according to three different flavour-reinforcement contingencies. One flavour was accompanied by a sweet on 90% of trials and was presented alone on 10% of the trials, while the remaining flavours were rewarded at ratios 50% : 50% and 10% : 90%, respectively. The conditioning phase occurred in conjunction with a counting task requiring continuous use of working memory, and was immediately followed by the participants making hedonic ratings of each flavour. Very few participants showed awareness of the purpose of the experiment or the specific reward contingencies. Despite this, the ratings given by the unrestrained eaters were highly correlated with the reward ratio experienced during conditioning. In contrast, restrained eaters exhibited no evidence for evaluative learning. These findings may explain the equivocal nature of results from previous studies of positive flavour-flavour learning (FFL) and may offer a novel theoretical context within which to study dietary restraint.  相似文献   
95.
Innovative research relating oceans and human health is advancing our understanding of disease-causing organisms in coastal ecosystems. Novel techniques are elucidating the loading, transport and fate of pathogens in coastal ecosystems, and identifying sources of contamination. This research is facilitating improved risk assessments for seafood consumers and those who use the oceans for recreation. A number of challenges still remain and define future directions of research and public policy. Sample processing and molecular detection techniques need to be advanced to allow rapid and specific identification of microbes of public health concern from complex environmental samples. Water quality standards need to be updated to more accurately reflect health risks and to provide managers with improved tools for decision-making. Greater discrimination of virulent versus harmless microbes is needed to identify environmental reservoirs of pathogens and factors leading to human infections. Investigations must include examination of microbial community dynamics that may be important from a human health perspective. Further research is needed to evaluate the ecology of non-enteric water-transmitted diseases. Sentinels should also be established and monitored, providing early warning of dangers to ecosystem health. Taken together, this effort will provide more reliable information about public health risks associated with beaches and seafood consumption, and how human activities can affect their exposure to disease-causing organisms from the oceans.  相似文献   
96.
BACKGROUND: By 2016, the proportion of Canadians older than 65 years of age will increase to 16%, and there will be an increase in the absolute number of cases of cardiovascular disease in older Canadians. The Canadian Heart Health Surveys database provides information about this population upon which health policy related to cardiovascular disease can be based. This paper presents for the first time population-based data on the risk factors for cardiovascular disease in older Canadians. METHODS: Canadians from all 10 provinces participated in surveys of cardiovascular risk factors; health insurance registries were used as sampling frames. In each province, probability samples of 2200 adults 18 to 74 years old not living in institutions, on reserves or in military camps were asked to participate in interviews and to undergo testing at clinics for major risk factors for cardiovascular disease. RESULTS: A total of 2739 men (response rate 70%) and 2617 women (response rate 66%) aged 55 to 74 years participated in the survey and also provided follow-up clinical measurements at the clinic. Overall, 52% of participants were hypertensive, 26% had isolated systolic hypertension, and 30% had a total blood cholesterol level of 6.2 mmol/L or greater. Rates of current smoking were lower in women than men (17% v. 22%). Overall, 87% of men and 78% of women who were current smokers smoked at least 10 cigarettes per day. Only slightly more than half of participants exercised at least once a week for at least 15 minutes, and almost half had a body mass index of 27 or greater. In only 4% was no major risk factor for cardiovascular disease detected. INTERPRETATION: Significant numbers of older Canadians have one or more major risk factors for cardiovascular disease. Many of these risk factors are amenable to modification.  相似文献   
97.
磁共振胰胆管造影在阻塞性黄疸诊断中的应用   总被引:7,自引:2,他引:7  
目的 评价磁共振胰胆管造影 (MRCP)技术在阻塞性黄疸诊断中的临床应用价值。方法 采用GE超导0 .5T ,Vectra 2磁共振成像仪 ,快速自旋回波 (FSE)重T2 加权扫描及最大强度投影 (MIP)重建图像 ,对 48例阻塞性黄疸患者作MRCP检查 ,所有患者均经手术证实。结果 各种病变的MRCP图像均有其特征性表达 ,MRCP对阻塞性黄疸的定位准确率为 10 0 % ,定性准确率为 93 .8%。结论 MRCP对阻塞性黄疸的诊断是一种有效、安全、可靠的方法。  相似文献   
98.
99.
Mosquitoes infect human beings with arboviruses while taking a blood meal, inoculating virus with their saliva. Mosquito saliva contains compounds that counter host hemostatic, inflammatory, and immune responses. Modulation of these crucial defensive responses may facilitate virus infection. Using a murine model we explored the potential for mosquitoes to impact the course of West Nile virus (WNV) disease by determining whether differences in pathogenesis occurred in the presence or absence of mosquito saliva. Mice inoculated intradermally with 10(4) pfu of WNV subsequent to the feeding of mosquitoes developed more progressive infection, higher viremia, and accelerated neuroinvasion than the mice inoculated with WNV alone. At a lower dose of WNV (10(2) pfu), mice fed upon by mosquitoes had a lower survival rate. This study suggests that mosquito feeding and factors in mosquito saliva can potentiate WNV infection, and offers a possible mechanism for this effect via accelerated infection of the brain.  相似文献   
100.
Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.   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