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   1054篇
  免费   221篇
  国内免费   5篇
耳鼻咽喉   7篇
儿科学   12篇
妇产科学   72篇
基础医学   172篇
口腔科学   104篇
临床医学   119篇
内科学   201篇
皮肤病学   34篇
神经病学   58篇
特种医学   14篇
外科学   119篇
综合类   46篇
预防医学   61篇
眼科学   11篇
药学   107篇
中国医学   7篇
肿瘤学   136篇
  2024年   1篇
  2023年   7篇
  2022年   18篇
  2021年   41篇
  2020年   34篇
  2019年   57篇
  2018年   54篇
  2017年   67篇
  2016年   48篇
  2015年   72篇
  2014年   56篇
  2013年   82篇
  2012年   51篇
  2011年   64篇
  2010年   69篇
  2009年   35篇
  2008年   50篇
  2007年   51篇
  2006年   38篇
  2005年   47篇
  2004年   43篇
  2003年   54篇
  2002年   39篇
  2001年   27篇
  2000年   22篇
  1999年   20篇
  1998年   7篇
  1997年   7篇
  1996年   5篇
  1995年   3篇
  1994年   3篇
  1993年   9篇
  1992年   9篇
  1991年   14篇
  1990年   11篇
  1989年   19篇
  1988年   8篇
  1987年   9篇
  1986年   9篇
  1985年   4篇
  1984年   6篇
  1982年   1篇
  1981年   2篇
  1977年   2篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
排序方式: 共有1280条查询结果,搜索用时 265 毫秒
81.
Existing literature suggests a relationship between the amount of remaining tooth structure and the fracture resistance of the restored endodontically treated tooth. This study investigated the amount of tooth structure remaining following various tooth preparations used in the restoration of the endodontically treated maxillary second premolar. Illustrations of the maxillary second premolar in buccopalatal, mesiodistal and occlusal sections were drawn to scale. Outlines of various intra- and extracoronal preparations were superim-posed on the illustrations to reveal the amount of tooth tissue remaining in each case. Preparations for a ceramic inlay, inlay with palatal cusp coverage and onlay left 2.0-2.5mm of tooth structure buccally and palatally. Following preparation for a metal-ceramic crown, approximately 1.0mm of tooth structure remained buccally, and between 1.6mm-1.8mm palatally. Preparation for an all-ceramic crown was observed to leave 1.0mm-1.2mm of tooth structure surrounding what remained of the endodontic access cavity. It was concluded that decisions as to the type of definitive restoration to restore the endodontically treated maxillary second premolar may be influenced, amongst other factors, by information on the amount of tooth tissue remaining following preparation.  相似文献   
82.
83.
OBJECTIVE: To assess the effect of short-term use of a gonadotropin releasing hormone (GnRH) analogue for 3 months before ovarian stimulation in patients with stage III and IV endometriosis after conservative surgery. STUDY DESIGN: Eleven patients were randomly selected to receive intramuscular injections of GnRH analogue, leuprolide acetate (3.75 mg), every 28 days, or 400 mg danazol orally 2 times per day for 3 months before ovarian stimulation after conservative laparoscopic or laparotomy surgeryfor stage III and IV symptomatic endometriosis (group 1), as compared with 30 patients who had received no postoperative treatment with GnRH analogue or danazol but underwent ovarian stimulation immediately after thefirst menses within 3 months postoperatively (group 2). RESULTS: Although the number of oocytes retrieved and number of embryos per cycle were significantly higher in group 1, the pregnancy rate per cycle in group 1 was not significantly different from that in group 2 (18% vs. 20%). The cumulative pregnancy rate at 12 months was 54.5% and 56.7% in group 1 and group 2, respectively. With regard to recurrence of disease after 24 months of follow-up, group 2 had a statistically significantly higher recurrence rate (13.3%) than did group 1 (0%). CONCLUSION: Short-term use of GnRH analogue before ovarian stimulation in women with stage III or IV endometriosis confers no definite benefits on pregnancy rates per cycle when compared with patients who received ovarian stimulation within 3 months after conservative surgery.  相似文献   
84.
OBJECTIVE: Large midline abdominal wall defects are continuously a challenge for reconstructive surgeons. Adequate skin coverage and fascia repair of the abdominal wall is necessary for achieving acceptable results. The purpose of this paper is to present a new approach to abdominal wall reconstruction using a free vascularized composite anterolateral thigh (ALT) flap with fascia lata. METHODS: Seven patients with large full-thickness abdominal wall defects were successfully reconstructed by means of a composite ALT flap combined with vascularized fascia lata. The size of the skin islands ranged from 20 to 32 cm in length and 10 to 22 cm in width, and the vascularized fascia lata sheath measured 14 to 28 cm and 8 to 18 cm, respectively. Functional outcome of the abdominal wall strength and donor thigh morbidity were investigated by using a Cybex kinetic dynamometer. RESULTS: All flaps survived. No postoperative ventral hernia occurred except for one mild inguinal incision hernia. Subjectively there were no significant donor site problems. Objective assessment was performed in 4 patients 2 years postoperatively. In the reconstructed abdomen, isokinetic concentric and eccentric measurements of extension/flexion ratios of the abdominal wall strength showed no apparent decrease compared with other references. Functional evaluation of quadriceps femoris muscle contraction forces after free ALT composite flap harvest showed an averaged deficit of 30% as compared with the contralateral legs. However, no difficulties in daily ambulating were reported by the patients. CONCLUSION: The free composite ALT myocutaneous flap with vascularized fascia lata provides an alternative option for a stable repair in complex abdominal wall defects.  相似文献   
85.
Younger women who develop breast cancer are hypothesized to have poorer survival rates than women who develop it at a later stage in life. Several studies have suggested that differences in biologic characteristics of breast cancer in younger (premenopausal) and older (postmenopausal) women may account for the prognostic variation. This population-based cohort study reports on survival rates of breast cancer in Singapore and examines the hypothesis that younger breast cancer patients have a poorer prognosis. A total of 6,397 breast cancer patients diagnosed from 1968 to 1992 were identified from the population-based cancer registry and followed up through 1997. Outcome measures were relative survival rates (RSRs) calculated using Hakulinen's method and excess hazards ratios (HRs) derived from a regression model based on relative survival. The 2-, 5- and 10-year RSRs were worse among those aged > 75 (65%, 48% and 39%, respectively). The best survival rates were seen among those aged 40-44 (84%, 67% and 56%). Patients younger than 35 years faired reasonably well (79%, 60% and 50%). When the data were stratified according to clinical stage and calendar year, the highest risk of excess deaths was found in women > or = 75 years old. In patients with localized cancer and/or regional metastases, those in the 35-39 age group had the lowest excess risk. In patients with distant metastases, those younger than 35 years of age had the lowest excess risk of death. At the population level, younger women (< 45 years) with breast cancer in Singapore have higher relative survival rates.  相似文献   
86.
87.
In T-cell Acute Lymphocytic Leukemia (T-ALL), the inhibitors of cyclin-dependent kinases (CDK) 4 and 6, p16 and p15, are inactivated almost universally at the DNA, RNA and protein levels. This suggests that CDK-targeting may be an effective therapeutic approach for T-ALL and other cancers. In this study, we tested 3 inhibitors of CDK4, 3-aminothioacridone (3-ATA), thioacridone (TA), and oxindole, for their effects on DNA synthesis and viability in primary T-ALL. Each compound was an effective inhibitor, with overall IC(50)s in similar ranges. In colony formation assay, leukemic cells were approximately 10-fold more sensitive to 3-ATA than normal bone marrow cells. When sorted by G1 protein status of T-ALL, p16(+), p15(+) or pRb(-) samples were significantly less sensitive to 3-ATA and TA, but not to oxindole, than p16(-), p15(-) or pRb(+) samples. There was no relationship of sensitivity with ARF expression. Despite their in vitro function as inhibitors of CDK4, 3-ATA did not inhibit pRb phosphorylation or cause G1 arrest, but did cause DNA damage and result in the induction and phosphorylation of p53. We conclude that 3-ATA efficacy can be predicted by p16 status in T-ALL, but the mechanism of action may be distinct from their in vitro ability to regulate CDK4 kinase activity  相似文献   
88.
Laparoscopic uterine suspension by round ligament plication   总被引:2,自引:0,他引:2  
OBJECTIVE: To describe a method for laparoscopic uterine suspension by round ligament plication using standard suturing instruments. STUDY DESIGN: Forty-six women underwent uterine suspension for treatment of chronic pelvic pain due to uterine retroversion over a period of five years. All operations were performed by the principal author. RESULTS: Forty-six patients treated with this technique were selected from 388 who underwent clinical evaluation and diagnostic laparoscopy for chronic pelvic pain, defined as lasting more than six months. There were no intraoperative complications in this series. Mean follow-up was 23.6 months (range, 6-42). At each follow-up, patients were asked to rate their pain relative to preoperatively as unchanged, minor, moderate, significant or resolved. At six months, 44 of 46 patients (96%) reported at least some improvement, with 17 (37%) reporting significant improvement, and 18 (39%) reporting resolution of pain. Sixteen of 27 patients (59%) at 24 months' follow-up and 15 of 23 patients (65%) with 36 months' follow-up reported significant improvement in or resolution of their pain. CONCLUSION: For patients experiencing chronic pelvic pain associated with uterine retroversion, round ligament plication is an effective method of repositioning the uterus and reducing or eliminating the patient's symptoms.  相似文献   
89.
OBJECTIVE: Our aim was to evaluate the feasibility of acquiring an MR signal intensity-time renographic curve and dynamic serial images in a way similar to that of acquiring radionuclide renograms, with a dynamic gradient-echo sequence and a low-dose gadopentetate dimeglumine technique, using a commonly available 1.5-T MR scanner. SUBJECTS AND METHODS. Patients who underwent both radionuclide and MR renographic studies within a 3-month period were included in the analysis. This yielded 21 studies from 19 patients. Nineteen of the 21 studies were available for analysis. Two studies were excluded because of technical errors during MR renographic acquisition. Serial MR renograms were obtained using a dynamic two-dimensional spoiled gradient-echo fast low-angle shot T1-weighted sequence. Low-dose IV furosemide and gadopentetate dimeglumine (0.025 mmol/kg of body weight) were administered. Intensity-time curves were obtained from the manually selected regions of interest over the renal parenchyma and whole kidney for calculation of split renal function and assessment of urinary excretion, respectively. Results were compared with those obtained with radionuclide renography. RESULTS: Good correlation (Pearson's correlation coefficient, r = 0.97, p < 0.001) was observed when the volume-corrected split renal function acquired with MR renography was compared with that obtained with radionuclide renography. There was also good agreement in the excretory curve patterns (weighted kappa(observer 1) = 0.77 and kappa(observer 2) = 0.81) between the two techniques. CONCLUSION: Dynamic MR gradient-echo imaging with a low-dose gadopentetate dimeglumine technique can produce an intensity-time curve and serial dynamic images of the urinary system, in a way similar to that of radionuclide renography. This technique allows assessment of split renal function and urinary excretory status and is a feasible alternative to radionuclide renography.  相似文献   
90.
A seven-year-old girl was referred to our clinic with absent eyelids and a mass which was gradually increasing in size from the right orbit. The child was diagnosed to have Fraser syndrome (cryptophthalmos, abnormal genitalia, mental deficiency, renal agenesis and abnormal ears). On examination, there was cryptophthalmos and a cystic swelling arising from the right orbit. The cyst was removed. On gross examination, there was a posterior eyeball with normal optic nerve. Placed in the anterior part of the eyeball was a cyst measuring about 2 cm in diameter filled with a yellow-coloured fluid. The cavity of the eyeball was communicating with the cyst. The cyst wall was lined by a single layer of epithelium. The posterior eyeball had well developed sclera, choroid, retina and optic nerve. There have been many reports of cryptophthalmos in Fraser syndrome. The most common eye deformity described with cryptophthalmos is microphthalmia or anophthalmia. To the author's knowledge, there is one other report of cystic eyeball with cryptophthalmos in the literature. The cyst seems to be due to a surface ectodermal anomaly, rather than a neuro-ectodermal anomaly where there is failure of invagination of the primary optic cup during development. The cyst wall in those cases has inverted retinal elements. In our case, differentiation of retinal elements was present in the posterior eyeball. The abnormality seemed to lie in the derivatives of surface ectoderm, namely the eyelids and the anterior segment structures.  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