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   11598篇
  免费   919篇
  国内免费   68篇
耳鼻咽喉   112篇
儿科学   626篇
妇产科学   301篇
基础医学   1751篇
口腔科学   239篇
临床医学   1101篇
内科学   2597篇
皮肤病学   132篇
神经病学   996篇
特种医学   522篇
外科学   1969篇
综合类   155篇
一般理论   3篇
预防医学   784篇
眼科学   218篇
药学   508篇
中国医学   11篇
肿瘤学   560篇
  2021年   107篇
  2019年   108篇
  2018年   137篇
  2017年   114篇
  2016年   116篇
  2015年   144篇
  2014年   227篇
  2013年   316篇
  2012年   402篇
  2011年   423篇
  2010年   242篇
  2009年   221篇
  2008年   431篇
  2007年   420篇
  2006年   381篇
  2005年   463篇
  2004年   428篇
  2003年   368篇
  2002年   387篇
  2001年   371篇
  2000年   362篇
  1999年   319篇
  1998年   149篇
  1997年   146篇
  1996年   139篇
  1995年   130篇
  1994年   105篇
  1992年   306篇
  1991年   284篇
  1990年   298篇
  1989年   317篇
  1988年   296篇
  1987年   293篇
  1986年   282篇
  1985年   267篇
  1984年   178篇
  1983年   201篇
  1982年   131篇
  1981年   133篇
  1980年   124篇
  1979年   224篇
  1978年   201篇
  1977年   163篇
  1976年   172篇
  1975年   146篇
  1974年   144篇
  1973年   146篇
  1972年   150篇
  1971年   108篇
  1969年   116篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
61.
M Kaplan 《Cancer nursing》1989,12(3):177-182
A retrospective study was conducted investigating the relationships between age and length of survival, and between age and the prognostic factors of disease stage, tumor size, histologic grade, and hematocrit. The subjects consisted of all of the women with early-stage invasive squamous cell cancer of the cervix, treated with radiation therapy alone in the Department of Radiation Oncology at the State University of New York-Health Science Center at Brooklyn between January 1, 1980, and December 31, 1986. The 105 eligible subjects were divided into two groups: those 39 and younger (n = 22) and those older than 39 (n = 83). Length of survival was significantly shorter for the younger group (p = 0.0009). Of this group, 50% had died from disease compared with 23% of the older group. Tumor size was also significantly greater in the younger group (p = 0.038). Further study is needed to determine the contributing risk factors for cancer of the cervix in young women and to develop a comprehensive gynecologic nursing assessment tool for identifying those at increased risk for this disease. In terms of developmental psychology, the young women fit into the stage of early adulthood. Knowledge of the tasks of this stage would facilitate the development of primary cancer prevention programs for this group.  相似文献   
62.
Does increased intracranial pressure in patients with pseudotumour cerebri PTC result in cognitive impairments The results of previous investigations have not clarified this question It may be that there is a subgroup within those diagnosed with PTC that does experience cognitive decline with increased intracranial pressure However elevated intracranial pressure headache and emotional distress also can contribute to reduced cognitive performance and increased self monitoring As a result of the lack of clarity regarding the impact of PTC on cognition clinicians are left with no empirically derived practice guidelines A case study demonstrates subjective complaints of concentration and memory deficits in a depressed patient with PTC whose neuropsychological stores except Seashore Rhythm Test were in the normal range  相似文献   
63.
It is not known whether patients with pulmonary arterial hypertension associated with portal hypertension (portopulmonary hypertension (PPHTN) have different disease characteristics from those of patients with other forms of pulmonary arterial hypertension. We performed a retrospective cohort study of patients with PPHTN and patients with pulmonary arterial hypertension that was idiopathic, familial, or associated with anorexigen use (IPAH) to determine whether hemodynamics or survival were different between these groups. We included consecutive patients who underwent initial pulmonary artery catheterization and vasodilator testing at our center between January 1997 and May 2001 and who were followed until January 2004. Patients with PPHTN (N = 13) had a higher cardiac index and lower pulmonary vascular resistance than patients with IPAH (N = 33) (P < or = 0.001). Right atrial pressure and pulmonary artery pressure were similar between the groups. Patients with PPHTN had a higher risk of death in multivariate analysis (hazard ratio: [HR] = 2.8, 95% CI 1.04-7.4; P = 0.04). These findings were not affected by adjustment for differences in laboratory values, hemodynamics, or therapy. In conclusion, patients with PPHTN have a higher risk of death than that of patients with IPAH, despite having a higher cardiac index and lower pulmonary vascular resistance. Future studies of the specific mechanisms of and therapy for pulmonary arterial hypertension should focus on the distinctions between the different forms of this disease.  相似文献   
64.
Biochemical markers of compliance in the Physicians' Health Study   总被引:2,自引:0,他引:2  
The Physicians' Health Study is a randomized, double-blind, placebo-controlled trial using a 2 x 2 factorial design to test the effects of low-dose aspirin on risk of cardiovascular disease and beta-carotene supplementation on the incidence of cancer. To evaluate self-reported compliance with assigned treatment, we measured serum thromboxane B2, which is decreased after aspirin use, and plasma beta-carotene in samples of study participants drawn from three geographic locations in three different time periods. Thromboxane B2 levels were markedly lower in those assigned to aspirin (median = 63.5 pg/mL) than in those given aspirin placebo (median = 3,600 pg/mL, P less than .0001). Similarly, those assigned to beta-carotene had significantly higher levels (median = 1,176 ng/mL) than those given placebo (median = 306 ng/mL, P less than .0001). In addition, there was a highly significant positive correlation between levels of these biochemical markers and the self-reports of compliance (r = 0.65 for thromboxane B2 and r = 0.69 for beta-carotene, P less than .0001). These findings support the validity of the self-reported compliance in the Physicians' Health Study.  相似文献   
65.
Kaplan  PA; Reiskin  AB; Tu  HK 《Radiology》1987,163(1):217-220
Arthrograms of the temporomandibular joint were obtained in 20 symptomatic joints that had previous reconstructive arthroplasty with disk repositioning because of internal derangements. Preoperative arthrograms were available for comparison in 18 joints. Symptoms resulting in a postoperative arthrogram included pain, limited ability to open the mouth, and clicking of the joints. Postoperative arthrographic findings included limited anterior translation of the condyle (90%), irregularity in outline of the intraarticular contrast agent (60%), a conical configuration of the posterior recess (25%), decreased size of the joint (28%), anterior displacement of the meniscus (25%), and perforated meniscus (15%). Many of these findings may have resulted from fibrosis and scarring, which may be a response to intraarticular bleeding. The mechanism by which the fibrosis causes the postsurgical arthrographic features is discussed.  相似文献   
66.
In a test of the hypothesis that lysogeny of group A streptococci by a temperate bacteriophage might confer nephritogenicity, 283 sera from 69 patients were examined for IgG and IgM antibodies to M 49 streptococcal bacteriophage hyaluronidase. The IgG and IgM response to bacteriophage hyaluronidase was greatest in M 49 streptococci-infected individuals with nephritis, but M 49 streptococci-infected subjects without nephritis also had a greater immune response than did subjects infected with serotypes other than M 49. Although antibody to bacterial hyaluronidase was detected in all Streptococcus-infected groups, antibody to M 49 streptococcal bacteriophage hyaluronidase usually was found in only M 49 streptococci-infected patients. Although the greatest IgG and IgM antibody response to bacteriophage hyaluronidase can be demonstrated in individuals with glomerulonephritis, the antibody response does not indicate a direct relation of lysogeny and nephritis because subjects with and without nephritis after M 49 streptococcal infection all had a significant rise in antibody titer.  相似文献   
67.
A new bone graft substitute made by conversion of the calcium carbonate exoskeleton of reef-building sea coral into hydroxyapatite has recently become clinically available. The normal radiographic appearance of two forms of this material is described. In the immediate postoperative period, the exoskeletal architecture of these implants is readily appreciated. With graft incorporation over the ensuing months, their intrinsic structure is gradually lost in association with poor marginal definition. Evolving radiographic findings reflect the biocompatible nature of these implants, which provides the potential for ingrowth of native bone with preservation of the coralline scaffold, resulting in enhanced biomechanical properties.  相似文献   
68.
Knowledge of the response of the primary visual cortex to the various spatial frequencies and orientations in the visual scene should help us understand the principles by which the brain recognizes patterns. Current information about the cortical layout of spatial frequency response is still incomplete because of difficulties in recording and interpreting adequate data. Here, we report results from a study of the cat primary visual cortex in which we employed a new image-analysis method that allows improved separation of signal from noise and that we used to examine the neurooptical response of the primary visual cortex to drifting sine gratings over a range of orientations and spatial frequencies. We found that (i) the optical responses to all orientations and spatial frequencies were well approximated by weighted sums of only two pairs of basis pictures, one pair for orientation and a different pair for spatial frequency; (ii) the weightings of the two pictures in each pair were approximately in quadrature (1/4 cycle apart); and (iii) our spatial frequency data revealed a cortical map that continuously assigns different optimal spatial frequency responses to different cortical locations over the entire spatial frequency range.  相似文献   
69.
70.
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