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   32491篇
  免费   3094篇
  国内免费   52篇
耳鼻咽喉   368篇
儿科学   1116篇
妇产科学   877篇
基础医学   4395篇
口腔科学   464篇
临床医学   4135篇
内科学   5985篇
皮肤病学   517篇
神经病学   3583篇
特种医学   761篇
外国民族医学   1篇
外科学   3575篇
综合类   491篇
现状与发展   1篇
一般理论   29篇
预防医学   4266篇
眼科学   406篇
药学   2494篇
  1篇
中国医学   36篇
肿瘤学   2136篇
  2023年   294篇
  2022年   450篇
  2021年   1005篇
  2020年   622篇
  2019年   898篇
  2018年   1034篇
  2017年   748篇
  2016年   849篇
  2015年   861篇
  2014年   1096篇
  2013年   1592篇
  2012年   2331篇
  2011年   2343篇
  2010年   1189篇
  2009年   1089篇
  2008年   1759篇
  2007年   1844篇
  2006年   1670篇
  2005年   1557篇
  2004年   1466篇
  2003年   1276篇
  2002年   1254篇
  2001年   586篇
  2000年   509篇
  1999年   489篇
  1998年   294篇
  1997年   274篇
  1996年   228篇
  1995年   230篇
  1994年   192篇
  1993年   182篇
  1992年   436篇
  1991年   358篇
  1990年   316篇
  1989年   315篇
  1988年   350篇
  1987年   310篇
  1986年   284篇
  1985年   226篇
  1984年   283篇
  1983年   202篇
  1982年   170篇
  1981年   141篇
  1980年   128篇
  1979年   201篇
  1978年   132篇
  1976年   137篇
  1975年   141篇
  1974年   123篇
  1972年   114篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Gangliocytic paragangliomas are rare tumors that almost exclusively occur within the second portion of the duodenum. Although these tumors generally have a benign clinical course, they have the potential to recur or metastasize to regional lymph nodes. The case report presented here describes a 57-year-old female patient with melena, progressive asthenia, anemia, and a mass in the second-third portion of the duodenum that was treated by local excision. The patient was diagnosed with a friable bleeding tumor. The histologic analysis showed that the tumor was a 4 cm gangliocytic paraganglioma without a malignant cell pattern. In the absence of local invasion or distant metastasis, endoscopic resection represents a feasible, curative therapy. Although endoscopic polypectomy is currently considered the treatment of choice, it is not recommended if the size of the tumor is > 3 cm and/or there is active or recent bleeding. Patients diagnosed with a gangliocytic paraganglioma should be closely followed-up for possible local recurrence.  相似文献   
2.
In the USA, the Black Church is among the most important institutions in the Black community, offering numerous spiritual, social and health benefits. Yet, the presence of homonegativity in many Black Churches may mitigate those effects for gay Black youth. This research examines the role of the Church in the lives of gay and bisexual Black youth to understand how they reconcile any tension between their religious and sexual identities. Through interviews with pastors of Black churches (n = 21) and young Black men who have sex with men (n = 30), we explored homonegativity and young men’s experiences within the Black Church. Findings reveal that despite the prevalence of homonegativity within Black churches, religious involvement remains important for young men and many remain involved in non-affirming churches. The importance of the Church for young men stems from their significant involvement as youth and the integration of religion, family and community. Young men may not be able to leave their religious homes as readily as other gay youth given the cultural relevance of the Church. As a result, young men made attempts to conceal their sexuality in church to avoid shame and gossip and find opportunities to balance their sexuality and religiosity.  相似文献   
3.
4.
5.

Objective

To determine whether differences in combination DTaP vaccine types at 2, 4 and 6?months of age were associated with mortality (all-cause or non-specific), within 30?days of vaccination.

Design

Observational nationwide cohort study.

Setting

Linked population data from the Australian Childhood Immunisation Register and National Death Index.

Participants

Australian infants administered a combination trivalent, quadrivalent or hexavalent DTaP vaccine (DTaP types) between January 1999 and December 2010 at 2, 4 and 6?months as part of the primary vaccination series. The study population included 2.9, 2.6, & 2.3?million children in the 2, 4 and 6?month vaccine cohorts, respectively.

Main outcome measures

Infants were evaluated for the primary outcome of all-cause mortality within 30?days. A secondary outcome was non-specific mortality (unknown cause of death) within 30?days of vaccination. Non-specific mortality was defined as underlying or other cause of death codes, R95 ‘Sudden infant death syndrome’, R96 ‘Other sudden death, cause unknown’, R98 ‘Unattended death’, R99 ‘Other ill-defined and unspecified cause of mortality’ or where no cause of death was recorded.

Results

The rate of 30?day all-cause mortality was low and declined from 127.4 to 59.3 deaths per 100,000 person-years between 2 and 6?month cohorts. When compared with trivalent DTaP vaccines, no elevated risk in all-cause or non-specific mortality was seen with any quadrivalent or hexavalent DTaP vaccines, for any cohort.

Conclusion

Use of routine DTaP combination vaccines with differing disease antigens administered during the first six months of life is not associated with infant mortality.  相似文献   
6.

Objective

The aim of this paper is to study the opportunity costs (OC) that are involved in being a caregiver and to compare them with the direct costs assumed by the State and the families. We evaluate direct cost (those that imply a payment-out-of-pocket) and indirect cost (those that imply a dedication in time). We hypothesized that costs increase with the severity of the dementia, with the educational level and active occupational situation of caregiver. They are greater if the caregiver is male, but if the patient and caregiver cohabit they are reduced.

Method

778 surveys were analyzed. Data was collected using a questionnaire specifically designed for the purpose, with the collaboration of Alzheimer's Diseases Associations in Andalusia (Spain). For the indirect cost, we used the reveal preferences method. For the comparison between groups an ANOVA and a MANOVA was done.

Results

The hypotheses were confirmed. The OC exponentially increases with severity. More than 55% of costs are assumed by families. Occupied people have higher educational level and incomes and contract more external support. Costs are significantly higher for male caregivers. Cohabiting reduces all kinds of costs.

Conclusions

The relationship between educational level and employment situation lead to think that if these variables are greater more people will seek professional support. Cultural reasons still maintain women as main caregivers for all educational levels. The existence of these informal caregivers as the main care providers is a saving for the State, and a brake for the development of professional supply.  相似文献   
7.
PURPOSE: The advantages of a focometer (FOCOMETER) over other methods of refraction for use in developing countries are that it is lightweight, compact, relatively inexpensive, fairly quick, and easy to use with minimal training. This clinical trial compared the repeatability, validity, and ease of use of the focometer with an autorefractor. METHODS: The refractive status of the right eye of 80 participants was determined with an autorefractor (Canon RK3). Three measurements were also taken with the focometer. RESULTS: The spherical equivalent (M) of the focometer was 0.25 D more positive than the autorefractor (p < 0.001) and 84% of measurements were within 0.75 D of the autorefractor. The autorefractor detected astigmatism in 91% (73) of the eyes, whereas the focometer identified only 32% (26). The design of the clock target restricts cylinder axis accuracy to the nearest 15 degrees . There was evidence of a learning effect for the focometer: the second and third measurements were more repeatable in the untrained group. There were no differences between the mean (1.03 +/- 2.28) and third focometer (-1.05 +/- 2.32) measurements (p = 0.34). However, using the third focometer measurement, 94% of participants had visual acuities of at least 6/12(-2). CONCLUSIONS: This study highlighted the focometer's restricted power range, inaccuracy of astigmatism and axis determination, and dependence on subject understanding and compliance. Therefore, in most clinical settings, the focometer would not be adequate for quantifying refractive error, but the focometer spherical equivalent was within acceptable limits of the autorefractor, and the visual acuity with lenses determined by the focometer indicates its potential usefulness in public health settings, especially where only spherical ready-made spectacles are dispensed. There may be more cost-effective ways to determine refractive error in these circumstances. A potentially important enhancement in focometer methodology that improves its ease of use was identified: use only the third measurement for each eye.  相似文献   
8.

Background  

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.  相似文献   
9.
10.
OBJECTIVE: To measure the effect of androgens or aromatase activity as an index of androgen responsiveness in patients with androgen insensitivity. DESIGN: Genital skin fibroblasts were established in culture using primary skin explants obtained from normal males at the time of circumcision and from androgen insensitive patients who had surgery either for gonadectomy (complete androgen insensitivity syndrome) or for reconstruction of the external genitalia (partial androgen insensitivity syndrome). PATIENTS: Foreskin samples were obtained at the time of circumcision in 27 normal males. Scrotal or labia majora skin was obtained at the time of surgery from 14 patients with the complete and 22 with the partial forms of the androgen insensitivity syndrome. MEASUREMENTS: Basal and stimulated levels of aromatase activity were measured in genital skin fibroblasts following preincubation with natural and synthetic, nonmetabolizable androgens. RESULTS: Following a 48-hour preincubation with testosterone or dihydrotestosterone, there was a five to six-fold stimulation of aromatase activity in normal fibroblasts. Mibolerone, a synthetic androgen, produced similar results. The stimulatory effect was blocked by anti-androgens. Seven patients with partial androgen insensitivity, of whom four were either receptor deficient or showed a qualitative defect in androgen binding, had reduced mibolerone induced stimulation of aromatase activity. All ten patients with receptor negative complete androgen insensitivity had an absent response. There was no aromatase induction in a further three patients with complete androgen insensitivity who were receptor positive. Two siblings in the latter group had an exon deletion encoding for part of the DNA binding domain of the androgen receptor. CONCLUSIONS: Androgens stimulate aromatase activity in genital skin fibroblasts from normals. The response is mediated via the androgen receptor and can be decreased or absent in patients with the androgen insensitivity syndrome. This may be a useful in-vitro marker of androgen responsiveness in such patients.  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