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   256722篇
  免费   18095篇
  国内免费   1151篇
耳鼻咽喉   2818篇
儿科学   6634篇
妇产科学   4697篇
基础医学   33681篇
口腔科学   4627篇
临床医学   25700篇
内科学   54893篇
皮肤病学   3503篇
神经病学   24735篇
特种医学   8458篇
外国民族医学   11篇
外科学   38790篇
综合类   3477篇
一般理论   321篇
预防医学   21853篇
眼科学   6658篇
药学   17257篇
  6篇
中国医学   397篇
肿瘤学   17452篇
  2023年   1417篇
  2022年   2582篇
  2021年   5692篇
  2020年   3378篇
  2019年   5458篇
  2018年   6132篇
  2017年   4597篇
  2016年   5106篇
  2015年   6002篇
  2014年   8810篇
  2013年   12063篇
  2012年   18407篇
  2011年   19324篇
  2010年   10737篇
  2009年   9584篇
  2008年   16869篇
  2007年   17682篇
  2006年   17531篇
  2005年   17475篇
  2004年   16391篇
  2003年   15208篇
  2002年   14240篇
  2001年   2125篇
  2000年   1613篇
  1999年   2342篇
  1998年   3092篇
  1997年   2589篇
  1996年   2204篇
  1995年   2112篇
  1994年   1755篇
  1993年   1586篇
  1992年   1274篇
  1991年   1162篇
  1990年   1007篇
  1989年   989篇
  1988年   975篇
  1987年   957篇
  1986年   957篇
  1985年   972篇
  1984年   1220篇
  1983年   1127篇
  1982年   1378篇
  1981年   1321篇
  1980年   1152篇
  1979年   712篇
  1978年   752篇
  1977年   641篇
  1976年   589篇
  1975年   473篇
  1974年   473篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The induction of antibody response in syngeneic rats by the Gross virus cell surface antigen (GCSAa) was dependent on the presentation of GCSAa into liposomes made from distearoylphosphatidylcholine (DSPC). GCSAa liposomes made from dimyristoylphosphatidylethanolamine (DMPE) were nonimmunogenic, even when used as anamnestic immunogens. Spleen cells, from rats twice immunized with GCSAa-DSPC-liposomes and used to transfer the anti-GCSAa immune response into naive recipients after a tertiary immunostimulation in vitro in the presence of naive peritoneal exudate cells (PEC), responded to soluble GCSAa only after irradiation at 500 rds and to GCSAa-DMPE-liposomes only when indomethacin was added during the in vitro stimulation. The preincubation of these cells with empty DMPE liposomes or the addition of supernatant from PEC fed with DMPE liposomes abrogated the response to GCSAa-DSPC liposomes. Using a specific radioimmunoassay, prostaglandin E2 was demonstrated to be produced by PEC when fed with DMPE liposomes, and not when fed with DSPC liposomes. This prostaglandin E2 secretion by PEC induced by DMPE liposomes was inhibited by indomethacin.  相似文献   
992.
The authors retrospectively assessed with sonography the prevalence of thyroid gland abnormalities in 30 patients who underwent radiation therapy for Hodgkin disease between 1962 and 1984. Doses ranged from 3,000 to 4,500 rad (3,000-4,500 cGy). Abnormalities were found in the sonograms of 24 patients and included unilateral (n = 6) or bilateral (n = 2) atrophy; multiple hypoechoic lesions smaller than 0.75 cm (n = 18); and dominant cystic (n = 2), solid (n = 3), or complex lesions (n = 4) larger than 0.75 cm. The risk of development of an abnormality increased as the time from irradiation increased and was comparable between patients who did and did not receive chemotherapy as part of the treatment regimen. Although the pathologic correlates of the various abnormalities seen on sonograms may differ, the findings indicate a need for long-term follow-up of patients who underwent cervical irradiation for Hodgkin disease.  相似文献   
993.
The use of item banks and computerized adaptive testing (CAT) begins with clear definitions of important outcomes, and references those definitions to specific questions gathered into large and well-studied pools, or “banks” of items. Items can be selected from the bank to form customized short scales, or can be administered in a sequence and length determined by a computer programmed for precision and clinical relevance. Although far from perfect, such item banks can form a common definition and understanding of human symptoms and functional problems such as fatigue, pain, depression, mobility, social function, sensory function, and many other health concepts that we can only measure by asking people directly. The support of the National Institutes of Health (NIH), as witnessed by its cooperative agreement with measurement experts through the NIH Roadmap Initiative known as PROMIS (www.nihpromis.org), is a big step in that direction. Our approach to item banking and CAT is practical; as focused on application as it is on science or theory. From a practical perspective, we frequently must decide whether to re-write and retest an item, add more items to fill gaps (often at the ceiling of the measure), re-test a bank after some modifications, or split up a bank into units that are more unidimensional, yet less clinically relevant or complete. These decisions are not easy, and yet they are rarely unforgiving. We encourage people to build practical tools that are capable of producing multiple short form measures and CAT administrations from common banks, and to further our understanding of these banks with various clinical populations and ages, so that with time the scores that emerge from these many activities begin to have not only a common metric and range, but a shared meaning and understanding across users. In this paper, we provide an overview of item banking and CAT, discuss our approach to item banking and its byproducts, describe testing options, discuss an example of CAT for fatigue, and discuss models for long term sustainability of an entity such as PROMIS. Some barriers to success include limitations in the methods themselves, controversies and disagreements across approaches, and end-user reluctance to move away from the familiar.  相似文献   
994.
995.
996.
997.
998.
999.
Background: Intervention trials with self-selected participants have shown that mailed stage-targeted print materials can increase participation in physical activity in the short term. We examined the effects of a mailed stage-targeted print intervention designed to promote physical activity, in a random sample of adults living in a regional city.Method: Participants (n = 462, 40–60 years of age) were randomly allocated to an intervention in - 227) or control group (n - 235). Measures included validated 2-week physical activity recall and stage of motivational readiness for physical activity. The intervention consisted of a single mailing of a letter and full-color stage-targeted booklets (specific to precontemplation, contemplation, preparation, and action/maintenance) 1 week postbaseline. Follow-up interviews were conducted at 2 and 6 months postbaseline.Results: After 2 months, participants in the intervention group were significantly More likely to meet the current American College of Sports Medicine/Centers for Disease Control and Prevention recommendation for sufficient physical activity than those in the control group (adjusted odds ratio [OR] - 2.40; 95% confidence interval [CI] = 1.44–3.99). After 6 months, intervention participants who reported receiving and reading the intervention materials were significantly more likely to be meeting the sufficient physical activity criterion compared with the control group (adjusted OR = 2.03; 95% Cl = 1.16–3.56).Conclusions: The stage-targeted print intervention was effective in promoting short-term increases in physical activity and was most effective for participants who recognized and used the materials. This low-cost, generalizable intervention has demonstrated potential as a practical population-based physical activity promotion strategy. Further research is required before widespread dissemination would be justified, as additional strategies may be required to ensure sustained change. This project was supported by a National Heart Foundation of Australia Research Project Grant. David Crawford was supported by a Nutrition Research fellowship from the National Heart Foundation.  相似文献   
1000.
Deficits in visual-spatial ability can be associated with Parkinson's disease (PD), and there are several possible reasons for these deficits. Dysfunction in frontal-striatal and/or frontal-parietal systems, associated with dopamine deficiency, might disrupt cognitive processes either supporting (e.g., working memory) or subserving visual-spatial computations. The goal of this study was to assess visual-spatial orientation ability in individuals with PD using the Mental Rotations Test (MRT), along with other measures of cognitive function. Non-demented men with PD were significantly less accurate on this test than matched control men. In contrast, women with PD performed similarly to matched control women, but both groups of women did not perform much better than chance. Further, mental rotation accuracy in men correlated with their executive skills involving mental processing and psychomotor speed. In women with PD, however, mental rotation accuracy correlated negatively with verbal memory, indicating that higher mental rotation performance was associated with lower ability in verbal memory. These results indicate that PD is associated with visual-spatial orientation deficits in men. Women with PD and control women both performed poorly on the MRT, possibly reflecting a floor effect. Although men and women with PD appear to engage different cognitive processes in this task, the reason for the sex difference remains to be elucidated.  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