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   13019篇
  免费   1379篇
  国内免费   43篇
耳鼻咽喉   159篇
儿科学   457篇
妇产科学   205篇
基础医学   2079篇
口腔科学   206篇
临床医学   1509篇
内科学   2386篇
皮肤病学   224篇
神经病学   1145篇
特种医学   611篇
外科学   1685篇
综合类   495篇
一般理论   9篇
预防医学   1272篇
眼科学   176篇
药学   915篇
中国医学   5篇
肿瘤学   903篇
  2021年   128篇
  2020年   108篇
  2019年   152篇
  2018年   203篇
  2017年   141篇
  2016年   153篇
  2015年   187篇
  2014年   254篇
  2013年   427篇
  2012年   532篇
  2011年   505篇
  2010年   308篇
  2009年   333篇
  2008年   500篇
  2007年   635篇
  2006年   569篇
  2005年   518篇
  2004年   461篇
  2003年   446篇
  2002年   459篇
  2001年   430篇
  2000年   407篇
  1999年   386篇
  1998年   247篇
  1997年   230篇
  1996年   212篇
  1995年   171篇
  1994年   189篇
  1993年   201篇
  1992年   322篇
  1991年   271篇
  1990年   276篇
  1989年   312篇
  1988年   252篇
  1987年   247篇
  1986年   221篇
  1985年   222篇
  1984年   194篇
  1983年   162篇
  1982年   121篇
  1981年   100篇
  1980年   116篇
  1979年   138篇
  1978年   122篇
  1977年   124篇
  1976年   131篇
  1975年   108篇
  1974年   107篇
  1972年   113篇
  1971年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Non‐alcoholic steatohepatitis (NASH) is a progressive form of non‐alcoholic fatty liver disease (NAFLD) and is a major cause of liver cirrhosis and hepatic failure. The methionine choline‐deficient diet (MCD) is a frequently used hepatotoxicity animal model of NASH that induces hepatic transaminase (ALT, AST) elevations and hepatobiliary histological changes similar to those observed in human NASH. Liver‐specific microRNA‐122 (miR‐122) has been shown as a key regulator of cholesterol and fatty acid metabolism in adult liver, and has recently been proposed as a sensitive and specific circulating biomarker of hepatic injury. The purpose of this study was to assess miR‐122 serum levels in mice receiving an MCD diet for 0, 3, 7, 14, 28 and 56 days and compare the performance vs. routine clinical chemistry when benchmarked against the histopathological liver findings. MiR‐122 levels were quantified in serum using RT‐qPCR. Both miR‐122 and ALT/AST levels were significantly elevated in serum at all timepoints. MiR‐122 levels increased on average by 40‐fold after 3 days of initiating the MCD diet, whereas ALT and AST changes were 4.8‐ and 3.3‐fold, respectively. In general, miR‐122 levels remained elevated across all time points, whereas the ALT/AST increases were less robust but correlated with the progressive severity of NASH as assessed by histopathology. In conclusion, serum levels of miR‐122 can potentially be used as a sensitive biomarker for the early detection of hepatotoxicity and can aid in monitoring the extent of NAFLD‐associated liver injury in mouse efficacy models. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
992.
The Internet is a powerful tool for accessing information about complex health topics. The purpose of this study was to evaluate breast cancer Internet sites using published criteria about website structure. Two searches were undertaken (November 1998 and June 1999) using the Yahoo search engine, providing a sample of 136 unique addresses. The results showed 1) owner's credentials were identified in 31.6% of sites, 2) financial charges were stated in 10.3% of sites, 3) less than 14.0% identified site creation date, 4) 33.1% identified content posting update, 5) 30.1% identified information sources, and 6) just under 88% of sites provided e-mail interactivity. The results indicate variability in breast cancer Internet sites with respect to framework criteria of accountability. We suggest that websites that lack fundamental indicators (such as dating and sources) do not provide the user with fundamental information that could enable informed decision making about site quality.  相似文献   
993.
994.
Dietary advanced glycation end-products (AGEs) form during heating and processing of food products and are widely prevalent in the modern Western diet. Recent systematic reviews indicate that consumption of dietary AGEs may promote inflammation, oxidative stress and insulin resistance. Experimental evidence indicates that dietary AGEs may also induce renal damage, however, this outcome has not been considered in previous systematic reviews. The purpose of this review was to examine the effect of consumption of a high AGE diet on biomarkers of chronic disease, including chronic kidney disease (CKD), in human randomized controlled trials (RCTs). Six databases (SCOPUS, CINHAL, EMBASE, Medline, Biological abstracts and Web of Science) were searched for randomised controlled dietary trials that compared high AGE intake to low AGE intake in adults with and without obesity, diabetes or CKD. Twelve dietary AGE interventions were identified with a total of 293 participants. A high AGE diet increased circulating tumour necrosis factor-alpha and AGEs in all populations. A high AGE diet increased 8-isoprostanes in healthy adults, and vascular cell adhesion molecule-1 (VCAM-1) in patients with diabetes. Markers of CKD were not widely assessed. The evidence presented indicates that a high AGE diet may contribute to risk factors associated with chronic disease, such as inflammation and oxidative stress, however, due to a lack of high quality randomised trials, more research is required.  相似文献   
995.
Food reformulation is an important strategy to reduce the excess salt intake observed in remote Indigenous Australia. We aimed to examine whether 12.5% and 25% salt reduction in bread is detectable, and, if so, whether acceptability is changed, in a sample of adults living in a remote Indigenous community in the Northern Territory of Australia. Convenience samples were recruited for testing of reduced-salt (300 and 350 mg Na/100 g) versus Standard (~400 mg Na/100 g) white and wholemeal breads (n = 62 for white; n = 72 for wholemeal). Triangle testing was used to examine whether participants could detect a difference between the breads. Liking of each bread was also measured; standard consumer acceptability questionnaires were modified to maximise cultural appropriateness and understanding. Participants were unable to detect a difference between Standard and reduced-salt breads (all p values > 0.05 when analysed using binomial probability). Further, as expected, liking of the breads was not changed with salt reduction (all p values > 0.05 when analysed using ANOVA). Reducing salt in products commonly purchased in remote Indigenous communities has potential as an equitable, cost-effective and sustainable strategy to reduce population salt intake and reduce risk of chronic disease, without the barriers associated with strategies that require individual behaviour change.  相似文献   
996.
To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1. 96 +/- 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 +/- 7.7 vs. 109.4 +/- 8.4 nmol/L, P = 0.001) than in CAU girls, but 1, 25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls.  相似文献   
997.
The aims of the National Diet and Nutrition Survey series are summarized, and the new National Diet and Nutrition Survey of people aged 65 years and over is explored, with particular emphasis on micronutrient intakes and status indices. Mean nutrient intakes were generally satisfactory for most micronutrients, but intakes of vitamin D, Mg, K and Cu were low. Intakes of vitamin D were far below the reference nutrient intake for people aged 65 years and over, and there was also biochemical evidence of vitamin D deficiency, for 8% of free-living and 37% of institution participants, attributed partly to limited exposure to sunlight. A substantial proportion of people living in institutions had inadequate biochemical status indices, notably for vitamin C, Fe and folate. Relationships between intake and status were close for vitamins. Mineral intakes did not correlate well with currently used status indices. Some intakes and indices, especially those of vitamin C, carotenoids, Na and K, were strongly correlated with socio-economic status and with north-south gradients in Britain. Future research challenges should address the functional and health significance of low intakes and sub-optimal biochemical indices for certain micronutrients, especially for people living in institutions; the shortcomings of mineral status indices especially as indicators of mineral intake; the social and geographical inequalities of micronutrient intakes and status, and why micronutrient status deteriorates with increasing age. The answers to these questions will help to define the characteristics of nutritional risk for older people in Britain, and to clarify future needs for education and intervention.  相似文献   
998.
BACKGROUND: The UK Health and Safety Executive (HSE) conducted a study to examine the risk of spontaneous abortion (SAB) in British female semiconductor industry workers, following reports from the USA which suggested an association between risk of SAB and work in fabrication rooms and/or exposure to ethylene glycol ethers. METHODS: A nested case-control study based on 2,207 women who had worked at eight manufacturing sites during a 5-year retrospective time frame was established; 36 cases were matched with 80 controls. RESULTS: The overall SAB rate in the industry was 10.0%. (65 SABs/651 pregnancies) The crude odds ratio (OR) for fabrication work was 0.65 (95% CI 0.30-1.40). This was essentially unchanged after adjustment for a range of potential confounding factors in the first 3 months of pregnancy and was reduced to 0.58 (95% CI 0.26-1.30) after adjustment for smoking in the previous 12 months. There were no statistically significantly elevated ORs for any work group or any specific chemical or physical exposure in the industry. CONCLUSIONS: There is no evidence of an increased risk of SAB in the British semiconductor industry. Am. J. Ind. Med. 36:557-572, 1999. Published 1999 Wiley-Liss, Inc.  相似文献   
999.
SB-616234-A possesses high affinity for human 5-HT1B receptors stably expressed in Chinese hamster ovary (CHO) cells (pKi 8.3 ± 0.2), and is over 100-fold selective for a range of molecular targets except h5-HT1D receptors (pKi 6.6 ± 0.1). Similarly, affinity (pKi) for rat and guinea pig striatal 5-HT1B receptors is 9.2 ± 0.1. In [35S]-GTPγS binding studies in the human recombinant cell line, SB-616234-A acted as a high affinity antagonist with a pA2 value of 8.6 ± 0.2 whilst providing no evidence of agonist activity in this system. In [35S]-GTPγS binding studies in rat striatal membranes, SB-616234-A acted as a high affinity antagonist with an apparent pKB of 8.4 ± 0.5, again whilst providing no evidence of agonist activity in this system. SB-616234-A (1 μM) potentiated electrically stimulated [3H]-5-HT release from guinea pig and rat cortical slices (S2/S1 ratios of 1.8 and 1.6, respectively). SB-616234-A (0.3–30 mg kg−1 p.o.) caused a dose-dependent inhibition of ex vivo [3H]-GR125743 binding to rat striatal 5-HT1B receptors with an ED50 of 2.83 ± 0.39 mg kg−1 p.o. Taken together these data suggest that SB-616234-A is a potent and selective 5-HT1B autoreceptor antagonist that occupies central 5-HT1B receptors in vivo following oral administration.  相似文献   
1000.
Chronic fatigue syndrome (CFS) is a relatively new disease that is difficult to diagnose. It is also a contested disease immersed in dispute about whether it is a physical or psychiatric reality. Sufferers often claim to experience not only the physical challenges of the disease, and these can be extensive, but also, initially, the anomie of suffering from a condition whose very reality is debated both in the medical and in the wider communities. Theories of self in illness emphasize how people who are diagnosed as chronically ill work hard as they seek to maintain previous, or to develop supernormal, selves. Such goals are cast in a critical light by Foucault's notion of the technologies of self in the context of circulating neo-liberal discourses. As people with CFS, lacking an uncontested medical diagnosis, search for meaningful self-identities, they resist previously available discourses to take up an alternative discourse, one that we call radicalized selves. This paper raises questions about the constraints and liberties, power and powerlessness associated with a clear and undisputed medical diagnosis. It suggests a model of the self in chronic illness that considers not only changes in body and biography but also the availability of an uncontested diagnosis.  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