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   25639篇
  免费   1810篇
  国内免费   54篇
耳鼻咽喉   256篇
儿科学   967篇
妇产科学   707篇
基础医学   3467篇
口腔科学   740篇
临床医学   2841篇
内科学   4924篇
皮肤病学   385篇
神经病学   2065篇
特种医学   933篇
外科学   3418篇
综合类   395篇
一般理论   46篇
预防医学   2650篇
眼科学   438篇
药学   1596篇
  1篇
中国医学   38篇
肿瘤学   1636篇
  2022年   246篇
  2021年   505篇
  2020年   324篇
  2019年   512篇
  2018年   560篇
  2017年   440篇
  2016年   436篇
  2015年   526篇
  2014年   745篇
  2013年   957篇
  2012年   1390篇
  2011年   1502篇
  2010年   810篇
  2009年   690篇
  2008年   1288篇
  2007年   1351篇
  2006年   1247篇
  2005年   1228篇
  2004年   1080篇
  2003年   1022篇
  2002年   889篇
  2001年   643篇
  2000年   631篇
  1999年   522篇
  1998年   248篇
  1997年   216篇
  1996年   212篇
  1995年   221篇
  1994年   202篇
  1993年   178篇
  1992年   472篇
  1991年   455篇
  1990年   434篇
  1989年   434篇
  1988年   396篇
  1987年   358篇
  1986年   305篇
  1985年   377篇
  1984年   293篇
  1983年   263篇
  1982年   163篇
  1979年   214篇
  1978年   182篇
  1977年   151篇
  1976年   149篇
  1975年   158篇
  1974年   161篇
  1973年   197篇
  1972年   160篇
  1971年   143篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Single breath-holding gradient echo techniques fast imaging with steady-state free precession (FISP) and fast low angle shot (FLASH) images were evaluated in the study of the abdomen in 16 patients (13 liver, two kidney, and one pancreas examinations). Gradient echo images were compared retrospectively with conventional spin echo images for image quality (depiction of pathology and representation of anatomic detail), and contrast characteristics were evaluated. All lesions were shown on gradient echo images, and in three of 16 cases gradient echo images were more diagnostic than spin echo images. On both FISP and FLASH images, most hepatic metastases were hyperintense relative to normal liver. The predicted flip angles for maximal contrast for the liver were modeled from signal intensity equations for FISP and FLASH and yielded predicted flip angles of approximately 40-55 degrees for FISP and 15-25 degrees for FLASH. Peak signal-to-noise ratio in liver of normal volunteers occurred at approximately 30 degrees for both FISP and FLASH. Single breath-holding gradient echo images are useful in the evaluation of abdominal structures and this study provides a framework for future work.  相似文献   
52.
53.
Designing behavior change programs and evaluating their effects on patient care has been a persistent challenge in research on continuing medical education. The challenge becomes even more complex when we aim to change behaviors that are interactive and highly influenced by the formal and informal institutional context. The authors describe an interdisciplinary continuing education program in bioethics that is designed to effect just such behaviors. The program aims to help hospital and long-term care facilities improve their ability to resolve the ethical dilemmas inherent in terminal care decisions. Targeted to interdisciplinary groups of physicians, nurses, social workers, pastoral counselors, and administrators, Decisions Near the End of Life will provide strategies and tools for examining institutional policies and team practices as well as more traditional information, education, and skill building. The authors describe the program's rationale and design, and raise questions about the potential for developing interdisciplinary, action-oriented CME on other topics.  相似文献   
54.
A group of six subjects with intractable spinal spasticity completed a double-blind cross-over paradigm in which they received two intrathecal bolus injections of baclofen solution five hours apart on two different days and two intrathecal bolus injections of placebo saline five hours apart on two other days. Each subject was repeatedly tested with a battery of clinical and physiological tests. In contrast to the placebo injections, the group responded to the baclofen injections with subjective and objective, clinically significant improvement in parameters of spasticity in their lower limbs, including muscle tone, frequency of spasms, hyperreflexia and passive range of joint motion. Furthermore, this improvement was maintained following thirty consecutive days of intrathecal bolus injections of baclofen at a fixed dose.  相似文献   
55.
Principal components analysis is a statistical method that is used to reduce and explore data to facilitate further analyses. This method was applied to bone mineral densities measured at seven sites in 109 black and 44 white women, ages 22-80, at an internal medicine clinic in urban Detroit. We excluded subjects with a history of diseases or drugs known to affect bone metabolism. Principal components analysis was used to summarize the interrelationship of the densities and yielded two major results. First, the seven site measurements were reduced to a single, composite index (PC1) of skeletal mass that accounted for 73% of the variation in density among subjects. PC1 had roughly equal weights among the sites. A second combination of the seven sites indicated that the contrast between axial and appendicular regional densities accounted for another 10% of the variation among subjects. In investigating the relationship of density to age, body mass index, and ethnic group, we found that the principal components composite index had a stronger correlation with age (r = -0.58) and with body mass index (r = 0.34) than almost all of the regional densities. Black-white differences were larger for the composite index than for any single site density. A multiple regression of the composite index on ethnicity, body mass index, and age yielded a larger R2 (0.46) than any of the individual site densities. The second principal component, although of theoretical interest, showed a minimal ability to discriminate among subjects using the three independent variables of this study.  相似文献   
56.
Background. Injection of DEAE dextran into Lewis rats can produce proteinuria and has been reported as a model of IgA nephropathy. Methods. Cationic diethyl aminoethyl (DEAE) dextran of molecular weight 500 KDa was injected into male Lewis rats. After a pre-immunization period of 3 weeks, the animals were divided into two groups: group 1 (n=14) received daily i.v. injections of 3.5 mg of antigen, group 2 (n=14) was injected with 1.5 mg three times per week for a total period of 6 weeks. I.v. treatment was initiated with gradually increasing doses of DEAE dextran in both groups for 1 week, after which the maintenance dose was reached. Results. We observed the appearance of proteinuria in a nephrotic range after 5 weeks of i.v. injections in group 1 (urinary excretion: 332±83 mg/24 h, controls: 53±14 mg/24 h). In group 2, the proteinuria was almost equal to protein excretion of healthy rats of the same weight (67±20 mg/24 h). The serum and urine creatinine were normal. By light microscopy of kidney biopsies, the presence of focal and segmental proliferation of mesangial cells after 6 weeks of i.v. injections was identified. Immunohistochemistry revealed no deposition of IgA, IgM, IgG, or C3. Using anti-ED1 antibodies, there was no evidence of interstitial infiltration of monocytes/macrophages after 6 weeks of i.v. injections. Staining for proliferating cell nuclear antigen (PCNA) did not show the presence of proliferating cells either in glomeruli or in the interstitium. Staining with FITC-WGA lectin revealed focal and segmental loss of the negative charge in the capillary wall. By electron microscopy there was deposition of dextran in the basal membrane and segmental and focal damage of the podocyte foot processes. As the chemokine RANTES may be involved in glomerular injury, we examined the kidneys of proteinuric and non-proteinuric rats for the presence of RANTES. By indirect immunofluorescence only the proteinuric rats showed RANTES deposition in mesangium. Conclusions. Injection of rats with DEAE dextran leads to dose-dependent proteinuria without deposition of immune complexes but with podocyte damage. This is associated with local expression of the chemokine RANTES which may play a role in proteinuria of glomerular disease.  相似文献   
57.
Some nonprofit mental health organizations are buying real estate in order to own service delivery sites and to provide housing for clients. Owning real estate generally requires long-term financing to conserve cash. This article explores tax exempt financing methods available to nonprofit mental health organizations.  相似文献   
58.
59.
A retrospective study of 42 adolescent patients diagnosed as being pregnant between June 1987 and February 1990 at the Downtown Health Center (DHC), an inner city pediatric primary care clinic, was conducted to determine whether patients referred to a hospital-based Teen Pregnancy Clinic (TPC) were seen within a reasonable period of time. The frequency of sexually transmitted diseases (STDs) was also determined when these women were initially seen at TPC. Only 5 of the 42 patients seen at DHC had a pelvic exam prior to referral. Of the 40 patients seen at TPC, 20% were not seen until four weeks or more after initial diagnosis. Fifty percent had a STD. Pediatricians should recognize that pregnant teenagers may have a significant delay between diagnosis of pregnancy and entry into obstetrical care. Pelvic exam including cultures for STDs is recommended prior to referral.  相似文献   
60.
Between July 1985 and January 1990, pseudomonas scepticaemia occurred in 19 out of 584 patients with AIDS attending the Westminster and St Stephen's AIDS Unit, London, UK. Ten of these 19 were being treated for active cytomegalovirus infection. Fourteen of the 19 patients had a central venous catheter in situ, which was the source of infection in 11. Seven patients died. Mortality was significantly greater in those patients infected with Pseudomonas aeruginosa, in those patients whose source of infection was not the central venous line, and in those patients whose central line was not removed.  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