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   1594篇
  免费   140篇
  国内免费   23篇
耳鼻咽喉   9篇
儿科学   30篇
妇产科学   29篇
基础医学   163篇
口腔科学   11篇
临床医学   130篇
内科学   320篇
皮肤病学   267篇
神经病学   84篇
特种医学   86篇
外科学   224篇
综合类   26篇
预防医学   108篇
眼科学   107篇
药学   70篇
中国医学   8篇
肿瘤学   85篇
  2023年   14篇
  2022年   21篇
  2021年   56篇
  2020年   50篇
  2019年   50篇
  2018年   52篇
  2017年   52篇
  2016年   71篇
  2015年   38篇
  2014年   54篇
  2013年   73篇
  2012年   78篇
  2011年   105篇
  2010年   55篇
  2009年   49篇
  2008年   64篇
  2007年   79篇
  2006年   65篇
  2005年   47篇
  2004年   59篇
  2003年   60篇
  2002年   53篇
  2001年   47篇
  2000年   42篇
  1999年   28篇
  1998年   28篇
  1997年   23篇
  1996年   22篇
  1995年   21篇
  1994年   28篇
  1993年   7篇
  1992年   10篇
  1991年   12篇
  1990年   14篇
  1989年   22篇
  1988年   14篇
  1987年   14篇
  1986年   13篇
  1985年   15篇
  1984年   12篇
  1983年   9篇
  1981年   9篇
  1980年   13篇
  1979年   10篇
  1978年   11篇
  1977年   7篇
  1971年   12篇
  1969年   4篇
  1966年   6篇
  1965年   4篇
排序方式: 共有1757条查询结果,搜索用时 1 毫秒
101.
The mammalian lignans enterolactone (ENL) and enterodiol, commonly found in human plasma and urine, are phytoestrogens that may contribute to the prevention of breast cancer and coronary heart disease. They are formed by the conversion of dietary precursors such as secoisolariciresinol and matairesinol lignans by the colonic microflora. The identification of lignins, cell-wall polymers structurally related to lignans, as precursors of mammalian lignans is reported here for the first time. In study 1, rats were fed rye or wheat bran (15% diet) for 5 d. Untreated brans and brans extracted with solvents to remove lignans were compared. ENL was estimated in urine samples collected for 24 h by time-resolved fluoroimmunoassay. ENL urinary excretion was reduced from 18.6 to 5.3 nmol/d (n=8; P<0.001) when lignans were removed from rye bran and from 30.5 to 6.2 nmol/d (P<0.001) when they were removed from wheat bran. These results suggest that lignins, embedded in the cell wall and retained in the bran during solvent extraction, account for 26-32% of the ENL formed from cereal brans. In study 2, rats were fed a deuterated synthetic lignin (0.2% diet) together with wheat bran (15%) for 3 d. The detection of deuterated ENL by LC-tandem MS in urine (20 nmol/d) clearly confirms the conversion of lignin into mammalian lignans. More research is warranted to determine the bioavailability of lignins in the human diet.  相似文献   
102.
PURPOSE: To quantify the oxidative tissue damage after phacoemulsification, correlate the damage to the energy applied, and investigate the influence of ophthalmic viscosurgical devices (OVDs). SETTING: Department of Ophthalmology, University of Mainz, Mainz, Germany. METHODS: The study comprised 130 eyes operated on by 1 surgeon using the same phacoemulsification machine. Some eyes received an OVD before phacoemulsification and some did not. Energy values were expressed as phaco time; that is, ultrasound (US) time (seconds) after conversion to 100% phaco power. Patients were grouped as follows: Group 1, phaco time less than 20 seconds and no OVD; Group 2, phaco time 20 to 40 seconds and no OVD; Group 3, phaco time more than 40 seconds and no OVD; Group 4, phaco time 20 to 40 seconds and hydroxypropyl methylcellulose 2% (HPMC); Group 5, phaco time 20 to 40 seconds and sodium hyaluronate 1%. Aqueous humor from pseudophakic eyes served as a control. At the end of surgery, anterior chamber fluid was analyzed for lipid peroxides using the thiobarbituric acid method. RESULTS: Lipid peroxides were detected in all groups. The values were significantly higher in Group 2 than in Group 1 (P<.01) and in Group 3 than in Groups 1 and 2 (P<.01). The differences in lipid peroxide values between all phaco groups and the control group were statistically significant. Sodium hyaluronate 1% and HPMC 2% produced significantly lower lipid peroxide values than in the respective phaco groups that did not receive an OVD (both P<.01). CONCLUSIONS: Oxidative tissue damage occurred during phacoemulsification. The damage, which correlated with the US energy applied, can be reduced by the use of OVDs.  相似文献   
103.
Dietary carbohydrates have different glycemic and insulinemic potentials depending on type (glycemic index, GI) and amount (glycemic load, GL) of carbohydrate consumed or both. Insulin in turn has been implicated as a risk factor for several cancers, including that of the prostate. We assessed the relationship of GI and GL with prostate cancer risk in a multicenter case-control study. Cases and controls were recruited between 1991 and 2002 in the network of major teaching and general hospitals in 4 Italian areas. Cases were 1,204 men (age range 46-74 years) admitted for incident, histologically confirmed prostate cancer. Controls were 1,352 men (age range 46-74 years) admitted for acute, nonmalignant conditions unrelated to long-term modifications of diet. ORs of prostate cancer and the corresponding 95% CIs were derived using unconditional multiple logistic regression, including terms for age, study center, education, family history of prostate cancer, smoking, body mass index, physical activity, alcohol consumption, intake of energy, fiber and lycopenes. Compared to the lowest quintile of GI, the ORs were 1.23, 1.24, 1.47 and 1.57 for subsequent levels of GI. The corresponding values for GL were 0.91, 1.00, 1.20 and 1.41. No heterogeneity was found among strata of selected covariates. We found direct relations between dietary GI and GL and prostate cancer risk. Correcting for potential confounding factors did not substantially modify these associations.  相似文献   
104.
PURPOSE: To present a new concept and technique for subretinal surgery. METHODS: Twenty-four eyes of 24 patients with subfoveal choroidal neovascularization (CNV) were included in this study. Nine patients were operated on in Mexico City by one surgeon, 15 patients in Frankfurt by another surgeon. The retina at the posterior pole was detached and subretinal thermal photocoagulation of the CNVs was performed using a 20/19-gauge GRIN rod laser endoscope (Insight Instruments Inc., Sanford, Fla., USA). This procedure was termed PEELS (pigment epithelium endoscopic laser surgery). RESULTS: In 7 patients (Mexico), moderate improvement or stabilization of vision over 6 months or longer was achieved. In 10 out of 12 patients (Frankfurt), stabilization of vision over a follow-up period of 6-18 months was achieved, at least. Serious complications were not observed. Four of the Frankfurt series patients improved their vision. CONCLUSION: PEELS can stabilize or improve vision.  相似文献   
105.
This article presents initial efficacy data for an innovative vocational rehabilitation model designed for methadone-maintained patients--the Customized Employment Supports (CES) model. In this model, a CES counselor works intensively with a small caseload of patients in order to overcome the vocational as well as nonvocational barriers that hinder their employment, with the goal of attaining rapid placement in competitive employment. The CES model was implemented at two Manhattan methadone treatment programs as part of a randomized clinical trial comparing the model's employment outcomes with those of standard vocational counseling. The study tested the hypothesis that patients in the experimental group will have better employment outcomes than those in the comparison group. The data were collected from May 2001 through September 2003. The sample consisted of the first 121 patients who had completed their 6-month follow-up interviews. The preliminary results supported the hypothesis for two indices of paid employment, i.e., the CES group was more likely to obtain both competitive employment and informal paid employment. The clinical trial is continuing.  相似文献   
106.
107.
OBJECTIVES: To up date counselling of patients in an experienced center, we assessed intraoperative and perioperative complications in a consecutive series of contemporary radical retropubic prostatectomy for localized prostate cancer. METHODS: In a prospective study, we analyzed all intraoperative and perioperative complications within 30 days in a consecutive series of 1243 patients undergoing radical prostatectomy between January 1999 and February 2002. All adverse events were graduated in major and minor complications by their severity and sequel. RESULTS: There were no deaths. Overall, 996 patients (80.2%) were not affected by any complication. Major complications were observed in 50 patients (4.0%), minor complications in 197 (15.8%). Pelvic lymphadenectomy was performed in 861 (69.3%) patients. This procedure was associated with a significantly higher rate of lymphoceles requiring a drainage, 4.2% versus 0.3% (p<0.006) and a higher rate of deep venous thrombosis, 1.4% versus 0.5% (p<0.2), respectively. CONCLUSION: Radical retropubic prostatectomy is a safe surgical procedure. Postoperatively the majority of our patients was not compromised by any complication within 30 days. Furthermore, due to a higher rate of lymphoceles and thromboembolic events the indication for pelvic lymphadenectomy should be considered carefully.  相似文献   
108.
We report a case of bilateral chronic subdural hematoma (SDH) in a 48-year-old man, who presented with postural headaches, tinnitus and progressive confusion without intoxication, head trauma or abnormal hemostasis. Magnetic resonance imaging revealed cerebellar tonsillar herniation in the foramen magnum and a deformation of the brainstem. Outcome was normal after surgery. We discuss about the rare causes of SDH in young adults.  相似文献   
109.
110.
OBJECTIVE: To identify the zonal location of prostate cancers before surgery, by analysing the mapping of ultrasonography-guided systematic sextant biopsies for differences between cancers located in the transition zone (TZ) and peripheral zone (PZ); and to compare the correlation between Gleason scores of needle biopsies and those of radical prostatectomy (RP) specimens. PATIENTS AND METHODS: In all, 186 patients with TZ (46) and PZ cancers (140) underwent ultrasonography-guided systematic sextant biopsy and RP at the same institution. The clinical and pathological characteristics, and the anatomical location of positive biopsies, were determined and compared using t-tests and chi-square tests. Differences between Gleason scores of needle biopsies and those of RP specimens were evaluated and compared by Cohen kappa testing. RESULTS: TZ cancers had a significantly lower rate of positive biopsies in the middle (63% vs 80%) and base (50% vs 80%) of the prostate than had PZ cancers. Positive biopsies were exclusively obtained from the apex in 19.6% of TZ and 5% of PZ cancers (P = 0.002). There was exact agreement between Gleason scores of needle biopsies and those of RP specimens in 15.2% of TZ (kappa = 0.02) and 55% of PZ cancers (kappa = 0.25), respectively. CONCLUSION: Compared with PZ cancers, TZ cancers had a different anatomical pattern of positive biopsies, with lower rates in the middle and base of the prostate. The finding of positive biopsies exclusively in the apex favoured prostate cancer located in the TZ. Furthermore, the correlation between needle biopsy Gleason scores and those of the RP specimens was clearly lower in TZ cancers.  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