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   818篇
  免费   55篇
  国内免费   38篇
耳鼻咽喉   1篇
儿科学   31篇
妇产科学   9篇
基础医学   104篇
口腔科学   13篇
临床医学   100篇
内科学   161篇
皮肤病学   93篇
神经病学   43篇
特种医学   109篇
外科学   60篇
综合类   25篇
一般理论   1篇
预防医学   55篇
眼科学   1篇
药学   77篇
中国医学   6篇
肿瘤学   22篇
  2023年   5篇
  2021年   11篇
  2020年   6篇
  2019年   7篇
  2018年   13篇
  2017年   5篇
  2015年   14篇
  2014年   17篇
  2013年   18篇
  2012年   24篇
  2011年   31篇
  2010年   23篇
  2009年   13篇
  2008年   33篇
  2007年   45篇
  2006年   20篇
  2005年   30篇
  2004年   35篇
  2003年   25篇
  2002年   29篇
  2001年   44篇
  2000年   29篇
  1999年   31篇
  1998年   24篇
  1997年   18篇
  1996年   12篇
  1995年   20篇
  1994年   20篇
  1993年   14篇
  1992年   22篇
  1991年   20篇
  1990年   23篇
  1989年   35篇
  1988年   18篇
  1987年   17篇
  1986年   16篇
  1985年   11篇
  1984年   9篇
  1983年   7篇
  1982年   8篇
  1981年   8篇
  1980年   6篇
  1976年   8篇
  1975年   4篇
  1974年   8篇
  1973年   8篇
  1972年   7篇
  1971年   13篇
  1970年   10篇
  1969年   8篇
排序方式: 共有911条查询结果,搜索用时 15 毫秒
1.
Scurvy is a nondiscriminatory disease process resulting from a nutritional deficiency of ascorbic acid (vitamin C). The severe vitamin deficiency produces a breakdown in the cellular structure of the body. This case report describes a middle-age woman with a history of edema, bruising of the lower extremities, anemia, and severe periodontal disease. Her presentation and medical history are classic for the signs of scurvy. Scurvy is now only uncommonly seen in developed countries, but there are still vulnerable populations whose nutritional status can lead to scurvy. The aim of this report is to help the clinician identify and treat scurvy, a disease that was once feared for its high mortality but is now easily treatable, even in cases that have progressed to multiple organ dysfunction and failure.  相似文献   
2.
Stent fracture is uncommon but may have consequences including restenosis. To date, stent fractures reported have been related to aggressive post dilation. We describe a case that involves fracture of a stent deployed to nominal pressure. Unlike most stent fractures reported that involve stent struts only our case demonstrated circumferential disruption with complete separation of the stent segments.  相似文献   
3.
Humoral control of water and electrolyte excretion during water restriction   总被引:1,自引:0,他引:1  
The goals of the present study were twofold: first, to assess the renal excretory and hormonal responses to chronic water restriction in dogs whose sodium retaining mechanisms had been stimulated through dietary sodium (Na+) deprivation; second, to determine the mediator(s) of the natriuresis which was observed with water restriction in these sodium deprived dogs. Three groups of dogs maintained on a low Na+ diet (5 mEq/day) for two weeks underwent a three day period of water restriction. In normal, intact dogs Group 1 (N = 5), water restriction resulted in a significant increase in Na+ excretion with a net cumulative loss of 26.3 +/- 2.6 mEq over three days. The natriuresis was associated with a significant increase in plasma vasopressin (PAVP) (1.7 to 10.2 pg/mliter) and a significant fall in plasma aldosterone (PALDO) from the levels observed with Na+ restriction alone (24.9 to 12.4 ng/dliter). The natriuresis could not be explained by decreases in food intake as determined by control studies in four dogs. Group 2 (N = 6) dogs had a decrease in PALDO with water restriction that was prevented by means of continuous i.v. aldosterone infusion (6.0 micrograms/kg/day). Dogs in this group failed to demonstrate a natriuresis during three days of water restriction, despite the fact that PAVP rose from 3.3 +/- 0.8 to a peak level of 14.95 +/- 1.9 pg/mliter. Group 3 (N = 6) dogs underwent selective neurohypophysectomy, thus preventing the rise in PAVP during three days of water restriction. In this group, PALDO also remained unchanged from the Na+ deprived level during water restriction, and no natriuresis was observed. We conclude: 1) that the natriuresis which occurs with water restriction is a potent physiological response that occurs even in the Na+ restricted state; and 2) this natriuresis can be explained by a fall in PALDO and not the rise in PAVP.  相似文献   
4.
FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.  相似文献   
5.
Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).  相似文献   
6.
It is argued that the prevalence of AIDS is substantially under-represented in existing national AIDS data. Thus although official statistics demonstrate significant recent shifts in transmission routes for HIV, health educators are faced with a problem because it is difficult to develop preventive strategies against a syndrome whose prevalence can only be estimated. Problems of the true extent of the prevalence of HIV are compounded when there is a lack of knowledge about the specifics of heterosexual behaviour. It is unwise to assume that the protective strategies developed by gay men in the face of HIV are routinely available for adoption by heterosexuals, who are characterised by social divisions of age, gender and relative amounts of social power. These concerns represent a problem for health educators. To date, sociological work may not have made the most effective contribution in its support of intervention strategies against HIV/AIDS. Examination of the empirical literature on lay concepts of health and illness reveals a pessimistic stance on the part of some researchers about the ability of individuals to modify behaviour. More positive readings of their own data are possible. The traditional concerns to emphasise the socio-economic determinants of health and behaviour, now also shared by some health educators, should not obscure a concern for the fate of individuals. The most effective contribution that health promotion may be able to make to the control of HIV in the heterosexual population is to assist in the development of strategies of empowerment and 'horizontal intervention'.  相似文献   
7.
General practitioner perceptions of low back pain patients   总被引:2,自引:0,他引:2  
  相似文献   
8.
There is some controversy about the role of long-term potentiation (LTP) in spatial learning. The authors have found that triggering generalized kindled seizures with stimulation of the perforant path disrupts spatial learning in the Morris water maze but that kindling per se does not affect spatial learning. It is suggested that abnormal electrical activity induced by high-frequency stimulation of the perforant path may have been responsible for the disruption of spatial learning previously attributed to LTP saturation.  相似文献   
9.
A reduction in interleukin-6 (IL-6) activity may contribute to the beneficial effects of hormone replacement therapy (HRT) on the menopausal decline in bone mineral density (BMD). We have examined this hypothesis using a genetic strategy. The –174C (rather than G) IL-6 gene variant is associated with lower IL-6 expression. As such, we might anticipate the C allele to be associated with a greater response to HRT. We have tested this hypothesis. Mean three-site [spine (L1-L4), neck of femur, and Wards triangle] BMD was measured in 65 women in a 1-year randomised controlled trial of HRT with 0.625 mg oestrogen/day and 0.15 mg norgestrel (n=30). Baseline BMD was genotype-independent for both the control and HRT group. In the control group, the percentage change in BMD after 1 year was similar between genotypes (P=0.45). In contrast, in the HRT group, the rise was genotype-dependent. Those homozygous for the G allele showed a 3.62 (2.14)% increase in BMD compared with 10.44 (4.68)% for the C-homozygous group. Heterozygotes had an intermediate BMD increase of 5.6 (2.82)% [P=0.006 (P value for interaction between HRT and genotype was 0.04)] Although the study was limited by its small sample size, these are the first data to demonstrate the importance of IL-6 genotype in determining response to oestrogen therapy, rather than its physiological withdrawal.  相似文献   
10.
Two major antigens of Bordetella pertussis, filamentous hemagglutinin (FHA) and pertussis toxin (PT), were efficiently purified from culture filtrate by exploiting their relative hydrophobicities and differences in affinity to sialic acid-containing protein. High yields of FHA (40 to 80 mg/liter) and PT (8 to 16 mg/liter) were first produced by growing the bacteria in the modified CL medium. The FHA and PT in the culture filtrate were adsorbed onto butyl-Sepharose by hydrophobic interaction at appropriately high ionic strength. Elution of the antigens was effected by decreasing their hydrophobicities with a buffer of low ionic strength. FHA was then separated from PT with an affinity column of fetuin-Sepharose. The fraction passing through the column contained purified FHA, and the fetuin-bound PT was eluted with buffered MgCl2. The FHA and PT purified by these steps were electrophoretically and serologically identical to the reference purified FHA and PT preparations. Approximately 16 to 32 mg of purified FHA and 4 to 8 mg of purified PT were obtained from 1 liter of culture filtrate. The described procedure for making FHA and PT antigens from B. pertussis for serologic and immunologic use is very simple, efficient, and reproducible.  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