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   18486篇
  免费   1447篇
  国内免费   51篇
耳鼻咽喉   136篇
儿科学   637篇
妇产科学   482篇
基础医学   2954篇
口腔科学   316篇
临床医学   2157篇
内科学   3359篇
皮肤病学   378篇
神经病学   2146篇
特种医学   407篇
外科学   2036篇
综合类   84篇
一般理论   23篇
预防医学   1991篇
眼科学   314篇
药学   1109篇
中国医学   34篇
肿瘤学   1421篇
  2024年   37篇
  2023年   212篇
  2022年   419篇
  2021年   799篇
  2020年   500篇
  2019年   702篇
  2018年   712篇
  2017年   573篇
  2016年   621篇
  2015年   656篇
  2014年   840篇
  2013年   1141篇
  2012年   1612篇
  2011年   1610篇
  2010年   754篇
  2009年   713篇
  2008年   1229篇
  2007年   1179篇
  2006年   1052篇
  2005年   1037篇
  2004年   959篇
  2003年   837篇
  2002年   721篇
  2001年   121篇
  2000年   59篇
  1999年   90篇
  1998年   127篇
  1997年   106篇
  1996年   69篇
  1995年   60篇
  1994年   53篇
  1993年   44篇
  1992年   31篇
  1991年   26篇
  1990年   23篇
  1989年   21篇
  1988年   19篇
  1987年   27篇
  1986年   14篇
  1985年   14篇
  1984年   15篇
  1983年   17篇
  1982年   24篇
  1981年   19篇
  1980年   17篇
  1979年   9篇
  1978年   7篇
  1977年   9篇
  1976年   5篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
OBJECTIVES: The objectives of this randomised controlled study were to determine if pre-admission patient education affects post-operative pain levels, domiciliary self-care capacity and patient recall following a laparoscopic cholecystectomy (LC). Participants were randomised to receive the standard preadmission program (SP) or an individualised, education intervention (El). DESIGN: A pre-operative questionnaire was administered in the pre-admission clinic to determine participants' knowledge of LC and post-operative management. Telephone follow-up and post-operative questionnaire were conducted approximately 14 days post discharge. SETTING: Preadmission clinic of a Sydney, Australia, tertiary referral hospital. SAMPLE: Ninety-three elective LC patients. RESULTS: EI participants experienced lower pain levels and had significantly greater recall of provided information. However, no significant differences were found between the control and intervention groups for domiciliary self-care. CONCLUSION: Pre-admission education intervention helps reduce post-operative pain levels following LC and significantly increases patients' knowledge of self-care and complication management.  相似文献   
2.
 The organization of the time frames for perceiving, generating, and updating information in the CNS has as of yet received little attention despite its elementary character for human behavior. We investigated temporal epochs in perceiving, acting, and updating in patients with anterior and posterior lesions of the left and right hemisphere, in patients with lesions in the left hemisphere without aphasia, and in healthy controls. Three temporal ranges, 30, 300, and 3000 ms, were assessed with different psychophysical paradigms. Prolongation of the temporal perception of order (30 ms) was most pronounced with left posterior lesions, of repetitive action (300 ms) with left anterior lesions, and updating (3000 ms) with left and right anterior lesions. Temporal deficits are group as well as parameter specific. Our results support the notion of coordinated coexistence of different temporal mechanisms.  相似文献   
3.
4.
PURPOSE: To identify the ocular features of the chromosome 22q11.2 deletion syndrome and to provide ophthalmologic examination recommendations for affected patients. METHODS: Ocular abnormalities were evaluated prospectively in patients with 22q11.2 deletion at the Children's Hospital of Philadelphia between 1997 and 1999. RESULTS: Ninety patients with confirmed 22q11.2 deletion were examined. Posterior embryotoxon was found in 49%, tortuous retinal vessels in 34%, eyelid hooding in 20%, strabismus in 18%, ptosis in 4%, amblyopia in 4%, and tilted optic nerves in 1%. CONCLUSIONS: The high incidence of ocular conditions that can potentially affect visual development suggest that children with 22q11.2 deletion should undergo a comprehensive eye examination upon diagnosis of the condition with follow-up as indicated by the findings in each case. In addition, knowledge of the ocular findings, in conjunction with certain cardiac, otolaryngologic, immunologic, and other systemic findings, may alert physicians to the possibility of a chromosome 22q11.2 deletion.  相似文献   
5.
Poverty influences health status, life expectancy, health behaviours, and use of health services. This study examined factors influencing the use of health-related services by people living in poverty. In the first phase, 199 impoverished users of health-related services in 2 large Canadian cities were interviewed by their peers. In the second phase, group interviews with people living in poverty (n = 52) were conducted. Data were analyzed using thematic content analysis. Diverse health-related services were used to meet basic and health needs, to maintain human contact, and to cope with life's challenges. Use of services depended on proximity, affordability, convenience, information, and providers' attitudes and behaviours. Use was impeded by inequities based on income status. To promote the health of people living in poverty, nurses and other health professionals can enhance the accessibility and quality of services, improve their interactions with people living in poverty, provide information about available programs, offer coordinated community-based services, collaborate with other sectors, and advocate for more equitable services and policies.  相似文献   
6.
Digital nerve injuries in the hand are common and can result in significant impairment and functional restriction. Despite this, there is relatively little literature, particularly with respect to postoperative rehabilitation. Splinting after repair, purported to protect the repaired nerve from excessive stretch is still commonly used. Recent cadaveric studies indicate postoperative rehabilitation is not necessary with resection up to 2.5mm. A randomized controlled trial was therefore undertaken to determine whether splinting after isolated 5th degree digital nerve transection is in fact necessary. Twenty-six subjects were recruited over a two-year period and randomized to either three weeks of hand-based splinting or free active motion. ANCOVA indicated no differences in sensibility at six months between the two groups. Subjects also reported their greatest functional limitations were because of hyperesthesia. Although this study is underpowered, these limited results suggest splinting may not be required postoperatively.  相似文献   
7.
PURPOSE: The Esophageal-Tracheal Combitube (Combitube) is widely used for the management of the airway during cardiopulmonary resuscitation in the pre-hospital setting. Although serious complications have been reported with the Combitube, there is a paucity of data relative to the frequency and nature of such complications. The objective of this retrospective study was to determine the incidence and the nature of complications associated to the Combitube in the pre-hospital setting. METHODS: Since 1993, in the Quebec City Health Region, the basic life support treatment algorithm for emergency medical technicians has included the use of a Combitube as the primary airway device for management of all patients presenting with cardiac or respiratory arrest. The database of the emergency coordination services was searched for the period between 1993 and 2003 (2,981 patients). Only those patients who survived at least 12 hr were included. Medical records of these patients were reviewed to identify complications related to the use of the Combitube. RESULTS: Two-hundred-eighty (280) patients were identified. Fifty-eight (58) patients (20.7%, confidence interval (CI)95%=16.0%-25.4%) presented 69 complications: aspiration pneumonitis (n=31), pulmonary aspiration (n=16), pneumothorax (n=6), upper airway bleeding (n=4), esophageal laceration (n=3), sc emphysema (n=2), esophageal perforation and mediastinitis (n=2), tongue edema (n=2), vocal cord injury (n=1), tracheal injury (n=1), and pneumomediastinum (n=1). Thirteen of these complications (12 patients, 4.3%, CI95%=2.0%-6.3%) were judged as most likely resulting from trauma associated with insertion of the Combitube. CONCLUSION: The use of the Combitube in the pre-hospital setting is associated with a notable incidence of serious complications.  相似文献   
8.

Background  

Glioblastoma multiforme is the most malignant form of brain tumor. Despite treatment including surgical resection, adjuvant chemotherapy, and radiation, these tumors typically recur. The recurrent tumor is often resistant to further therapy with the same agent, suggesting that the surviving cells that repopulate the tumor mass have an intrinsic genetic advantage. We previously demonstrated that cells selected for resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) are near-diploid, with over-representation of part or all of chromosomes 7 and 22. While cells from untreated gliomas often have over-representation of chromosome 7, chromosome 22 is typically under-represented.  相似文献   
9.
Membrane-bound GTP-binding (G) proteins mediate signal transduction in a variety of cell systems. The exact mechanisms of G proteins action are still under investigation but they appear to involve effectors located in the plasma membrane as well as in other parts of the cell. With this study, we investigated the cellular and ultrastructural localization of G protein subunits, and particularly of Goa, in normal rat anterior pituitaries and in estrone-induced rat adenomatous lactotrophs. We also evaluated the effects of Goα cellular redistribution in rat adenomatous lactotrophs following short-term exposure to dopamine (DA). Using the Protein A-gold (PAG) methodology, Goα was found to be present in the cysternae of the endoplasmic reticulum of normal pituitary cells and of adenomatous lactotrophs. In the latter, Goα could be co-localized with prolactin (PRL). By immunoblots, using specific antisera, significant amounts of Goα and Gs42α, together with smaller amounts of Giα, Gs47α and Gβ were found to be present in the uncontaminated supernatant fraction of adenomatous lactotrophs. Unexpectedly, exposure of the cells to DA induced a rapid and short-lived decrease in the cytosolic fraction of Goα and Gβ associated with a decrease of PRL release. Since cytosolic Goα can be ADP-ribosylated by pertussis toxin (PT) and is therefore in a heterotrimeric form, our data suggest that the soluble Go protein may play a role during lactotrophs' exposure to an inhibitor of PRL release, perhaps through its relocalization after being internalized with the D2 receptor or by being used for interaction with intracellular and/or membrane-bound effectors.  相似文献   
10.
A novel approach that uses the concepts of parallel imaging to grid data sampled along a non-Cartesian trajectory using GRAPPA operator gridding (GROG) is described. GROG shifts any acquired data point to its nearest Cartesian location, thereby converting non-Cartesian to Cartesian data. Unlike other parallel imaging methods, GROG synthesizes the net weight for a shift in any direction from a single basis set of weights along the logical k-space directions. Given the vastly reduced size of the basis set, GROG calibration and reconstruction requires fewer operations and less calibration data than other parallel imaging methods for gridding. Instead of calculating and applying a density compensation function (DCF), GROG requires only local averaging, as the reconstructed points fall upon the Cartesian grid. Simulations are performed to demonstrate that the root mean square error (RMSE) values of images gridded with GROG are similar to those for images gridded using the gold-standard convolution gridding. Finally, GROG is compared to the convolution gridding technique using data sampled along radial, spiral, rosette, and BLADE (a.k.a. periodically rotated overlapping parallel lines with enhanced reconstruction [PROPELLER]) trajectories.  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