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   8328篇
  免费   670篇
  国内免费   37篇
耳鼻咽喉   27篇
儿科学   226篇
妇产科学   191篇
基础医学   1098篇
口腔科学   312篇
临床医学   795篇
内科学   1322篇
皮肤病学   136篇
神经病学   860篇
特种医学   406篇
外科学   1065篇
综合类   195篇
一般理论   8篇
预防医学   810篇
眼科学   66篇
药学   595篇
中国医学   5篇
肿瘤学   918篇
  2022年   51篇
  2021年   93篇
  2020年   61篇
  2019年   112篇
  2018年   121篇
  2017年   108篇
  2016年   125篇
  2015年   122篇
  2014年   202篇
  2013年   267篇
  2012年   393篇
  2011年   414篇
  2010年   232篇
  2009年   206篇
  2008年   388篇
  2007年   366篇
  2006年   358篇
  2005年   348篇
  2004年   378篇
  2003年   329篇
  2002年   303篇
  2001年   267篇
  2000年   281篇
  1999年   257篇
  1998年   130篇
  1997年   137篇
  1996年   109篇
  1995年   111篇
  1994年   116篇
  1993年   82篇
  1992年   231篇
  1991年   197篇
  1990年   160篇
  1989年   163篇
  1988年   144篇
  1987年   167篇
  1986年   151篇
  1985年   150篇
  1984年   88篇
  1983年   94篇
  1982年   58篇
  1981年   58篇
  1979年   70篇
  1978年   75篇
  1977年   54篇
  1976年   53篇
  1974年   64篇
  1973年   51篇
  1972年   56篇
  1971年   59篇
排序方式: 共有9035条查询结果,搜索用时 15 毫秒
91.
92.
OBJECTIVE: To quantify the dietary calcium and vitamin D intake in adult renal-transplant recipients attending at a large teaching hospital in Ireland for follow-up. SETTING: Outpatient renal-transplant follow-up clinic. SUBJECTS: Fifty-nine adult renal transplant recipients (58% male) with a mean age of 46 years, a median transplant duration of 6 years, and a mean estimated glomerular filtration rate (eGFR) of 50 mL/min per 1.73 m2. Fifty-three percent were at National Kidney Foundation stage 3 chronic kidney disease, and 14% had stage 4 chronic kidney disease. INTERVENTION: This cross-sectional, observational study used a tailored food frequency questionnaire specific for calcium and vitamin D intake in Irish adults, which was completed during a face-to-face interview with each subject. MAIN OUTCOME MEASURE: The main outcome measure was the average daily dietary and supplemented calcium and vitamin D intake. RESULTS: The median interquartile range (IQR) dietary calcium intake was 820 mg/day (range, 576-1,177 mg/day), and was similar in men and women (recommended intake > or = 1,000 mg/day in adult men and nonmenopausal adult women, > or = 1,500 mg/day in menopausal women). Five participants received calcium supplementation. Overall, 59% of men and 64% of women had total calcium intakes below the recommended amounts. The median IQR estimated dietary vitamin D intake was 5.2 microg/day (range, 2.4-6.4 microg/day) in women, and 4.6 microg/day (range, 2.2-6.6 microg/day) in men (recommended intake, > or = 10 microg/day). Six subjects received vitamin D supplementation. Total vitamin D intakes were suboptimal in 91% of men and 87% of women. Dietary calcium and vitamin D intakes significantly correlated with each other, but neither was significantly related to eGFR category, and was similarly low in both presumed menopausal women and in the initial year posttransplantation. CONCLUSION: These findings suggest that dietary and total calcium and vitamin D intakes in adult renal-transplant patients are in many cases inadequate.  相似文献   
93.
PURPOSE: The objective of this survey was to examine the services offered by multidisciplinary pain treatment facilities (MPTFs) across Canada and to compare access to care at these MPTFs. METHODS: A MPTF was defined as a clinic that advertised specialized multidisciplinary services for the diagnosis and management of patients with chronic pain, having a minimum of three different health care disciplines (including at least one medical speciality) available and integrated within the facility. The search method included approaching all hospital and rehabilitation centre administrators in Canada, the Insurance Bureau of Canada, the Workplace Safety and Insurance Board or similar body in each province. Designated investigators were responsible for confirming and supplementing MPTFs from the preliminary list for each province. Administrative leads at each eligible MPTF were asked to complete a detailed questionnaire regarding their MPTF infrastructure, clinical, research, teaching and administrative activities. RESULTS: Completed survey forms were received from 102 MPTFs (response rate 85%) with 80% concentrated in major cities, and none in Prince Edward Island and the Territories. The MPTFs offer a wide variety of treatments including non-pharmacological modalities such as interventional, physical and psychological therapy. The median wait time for a first appointment in public MPTFs is six months, which is approximately 12 times longer than non-public MPTFs. Eighteen pain fellowship programs exist in Canadian MPTFs and 64% engage in some form of research activities CONCLUSION: Canadian MPTFs are unable to meet clinical demands of patients suffering from chronic pain, both in terms of regional accessibility and reasonable wait time for patients' first appointment.  相似文献   
94.
Background: The authors determined whether desflurane altered myocardial excitation-contraction coupling and electrophysiologic behavior in the same manner as isoflurane and sevoflurane.

Methods: The effects of desflurane on isometric force in guinea pig ventricular papillary muscles were studied in modified standard and in 26 mm K+ Tyrode solution with 0.1 [mu]m isoproterenol. Desflurane effects on sarcoplasmic reticulum Ca2+ release were also determined by examining its actions on rat papillary muscles, guinea pig papillary muscles in low-Na+ Tyrode solution, and rapid cooling contractures. Normal and slow action potentials were recorded using a conventional microelectrode technique. Ca2+ and K+ currents of guinea pig ventricular myocytes were examined.

Results: Desflurane (5.3% and 11.6%) decreased peak force to approximately 70% and 40% of the baseline, respectively, similar to the effects of equianesthetic isoflurane concentrations. With isoproterenol in 26 mm K+ Tyrode solution, desflurane markedly depressed late peaking force and modestly depressed early peak force. The rested state contractions of rat myocardium or guinea pig myocardium in low-Na+ Tyrode solution were modestly depressed, whereas rapid cooling contractures were virtually abolished after desflurane administration. Desflurane significantly prolonged the action potential duration. Desflurane reduced L-type Ca2+ current and the delayed outward K+ current but did not alter the inward rectifier K+ current.  相似文献   

95.
BACKGROUND: Active and young individuals with glenohumeral arthritis who are treated with total glenohumeral arthroplasty are at risk for loosening or wear of the prosthetic glenoid component. This study tests the hypothesis that patients with severe glenohumeral arthritis have improvement in self-assessed shoulder comfort and function at two to four years after treatment with the combination of humeral hemiarthroplasty and concentric glenoid reaming without tissue or prosthetic component interposition. METHODS: Thirty-seven consecutive patients (thirty-eight shoulders), with a mean age of fifty-seven years, who were managed by one surgeon were enrolled in this prospective study. The procedure consisted of an uncemented humeral hemiarthroplasty combined with reaming of the glenoid to a diameter 2 mm larger than that of the prosthetic humeral head. The duration of follow-up ranged from two to four years (average, 2.7 years) for thirty-five shoulders. Self-assessed comfort and function was documented with use of the Simple Shoulder Test, and radiographs were evaluated. RESULTS: Thirty-two shoulders demonstrated improved comfort and function according to patient self-assessment, one demonstrated no change, and two had worse function following the procedure. The total number of Simple Shoulder Test functions that could be performed increased from 4.7 (of a possible 12.0) before surgery to 9.4 at the time of the final follow-up. The patients demonstrated significant improvement in ten of the twelve individual functions of the Simple Shoulder Test (p < 0.022 to p < 0.00001). With the numbers studied, gender, diagnosis, age, glenoid wear, and preoperative glenoid erosion did not significantly affect final shoulder function or overall improvement. The range of motion was significantly improved for all individuals (p < 0.00001). Radiographically, twenty-two patients had a joint space between the glenoid bone and the humeral prosthesis at the time of final follow-up. These shoulders had significantly better function than those without a preserved joint space (p < 0.017). There were no surgical complications and no revisions to total shoulder arthroplasty. CONCLUSIONS: At a minimum follow-up of two years, a selected series of patients who had humeral hemiarthroplasty with concentric glenoid reaming for the treatment of glenohumeral arthritis showed significant improvement in self-assessed shoulder comfort and function. Further study, however, is needed before routine application of this procedure can be recommended. LEVEL OF EVIDENCE: Therapeutic Level IV.  相似文献   
96.
Despite advances in surgical technique, fracture fixation alternatives, and adjuncts to healing, femoral nonunion continues to be a significant clinical problem. Femoral fractures may fail to unite because of the severity of the injury, damage to the surrounding soft tissues, inadequate initial fixation, and demographic characteristics of the patient, including nicotine use, advanced age, and medical comorbidities. Femoral nonunion is a functional and economical challenge for the patient, as well as a treatment dilemma for the surgeon. Surgeons should understand the various treatment alternatives and their role in achieving the goals of deformity correction, infection management, and optimization of muscle strength and rehabilitation. Used appropriately, nail dynamization, exchange nailing, and plate osteosynthesis can help minimize pain and disability by promoting osseous union. A review of the potential risk factors and treatment alternatives should provide insight into the etiology and required treatment of femoral nonunion.  相似文献   
97.
Can localization studies be used to direct focused parathyroid operations?   总被引:32,自引:0,他引:32  
BACKGROUND: There is considerable controversy today concerning the most appropriate surgical approach for patients with primary hyperparathyroidism. The conventional surgical operation involves a bilateral neck exploration through a collar incision with identification of all parathyroid tissue and removal of abnormal parathyroid glands while the patient is under general anesthesia. The success rate of this operation is about 95% or greater in the hands of an experienced endocrine surgeon. Preoperative localization techniques are generally considered to be unnecessary before initial parathyroid operations. The purpose of this investigation was (1) to evaluate the individual and combined accuracy of ultrasonography and technetium 99m sestamibi scans in localizing abnormal parathyroid glands and (2) to determine whether such scans could be used to direct a focused operation. METHODS: We retrospectively studied 338 patients with sporadic primary hyperparathyroidism who had preoperative neck localization studies, ultrasonography and/or technetium 99m sestamibi scans, and parathyroid exploration (238 patients or, reexploration, 60 patients) from January 1996 to April 2000 at the University of California San Francisco/Mount Zion Medical Center. The preoperative localization studies were recorded as true-positive, false-positive, and false-negative and compared with the surgical and pathologic findings and with the outcome of the operation. RESULTS: All of the abnormal parathyroid glands were correctly identified by ultrasonography in 184 of 303 patients (60.7%) and by technetium 99m sestamibi scanning in 183 of 237 patients (77.2%). The sensitivities of ultrasonography and sestamibi were 65% and 80%, respectively. Among the 202 patients who received both ultrasonography and sestamibi scans, a parathyroid tumor was identified at the same site in 105 (52%) of them. When both techniques identified a parathyroid tumor at the same site, the tests were correct in 101 of 105 patients and the sensitivity increased to 96%. CONCLUSIONS: When both the ultrasonography and sestamibi scans identified the same, solitary parathyroid tumor in patients with sporadic primary hyperparathyroidism, this was the only abnormal parathyroid gland in 96% of the patients. A focused parathyroidectomy could therefore be performed in such patients with an acceptable ( approximately 95%) success rate.  相似文献   
98.
PURPOSE: Brachytherapy with 103palladium (103Pd) is an increasingly administered treatment modality for localized prostate cancer. We compared general and disease specific health related quality of life after 103Pd treatment, radical prostatectomy and external beam radiation therapy given during the same time frame. MATERIALS AND METHODS: We performed a retrospective cross-sectional survey study of patients treated at a single community medical center between 1995 and 1999. We mailed 5 validated health related quality of life survey instruments to 269, 142 and 222 men who underwent radical prostatectomy, 103Pd treatment and external beam radiation therapy, respectively, with a response rate of greater than 80% in all groups. RESULTS: General health related quality of life assessed by the SF-36 showed the same scores in patients who underwent prostatectomy and 103Pd treatment. The University of California-Los Angeles Prostate Cancer Index was used to assess bowel, urinary and sexual function/bothersomeness. External beam radiation therapy reported was associated with worse bowel function and greater bowel bothersomeness. Prostatectomy was associated with worse urinary function compared to 103Pd and external beam radiation therapy. Prostatectomy was associated with worse sexual function than 103Pd or external beam radiation therapy, although nerve sparing surgery and erectile aids minimized the difference. American Urological Association symptom scores were initially higher for 103Pd but became equal to those in the other groups in patients treated greater than 12 months from survey time. Disease-free men who underwent prostatectomy and 103Pd brachytherapy were equally confident that cancer would not recur in the future. Satisfaction rates were equivalent and biochemical failure significantly decreased satisfaction in all groups. CONCLUSIONS: While general health related quality of life was mostly unaffected by the 3 most common treatments for prostate cancer, there were differences in bowel, urinary and sexual function. This information may aid patients in the decision making process.  相似文献   
99.
The authors evaluated magnetic resonance (MR) images obtained with intravenously administered gadolinium in ten patients who had facial paralysis and no facial nerve tumor. In patients with either Bell palsy (four patients) or facial paralysis after temporal bone surgery (six patients), intratemporal facial nerve enhancement was seen. Facial nerve enhancement on MR images proved to be a nonspecific finding.  相似文献   
100.
Henry MK  Lynch JT  Eapen AK  Quelle FW 《Blood》2001,98(3):834-841
Exposure of hematopoietic cells to DNA-damaging agents induces cell-cycle arrest at G1 and G2/M checkpoints. Previously, it was shown that DNA damage-induced growth arrest of hematopoietic cells can be overridden by treatment with cytokine growth factors, such as erythropoietin (EPO) or interleukin-3 (IL-3). Here, the cytokine-activated signaling pathways required to override G1 and G2/M checkpoints induced by gamma-irradiation (gamma-IR) are characterized. Using factor-dependent myeloid cells stably expressing EPO receptor (EPO-R) mutants, it is shown that removal of a minimal domain required for PI-3K signaling abrogated the ability of EPO to override gamma-IR-induced cell-cycle arrest. Similarly, the ability of cytokines to override gamma-IR-induced arrest was abolished by an inhibitor of PI-3K (LY294002) or by overexpression of dominant-negative Akt. Moreover, the ability of EPO to override these checkpoints in cells expressing defective EPO-R mutants could be restored by overexpression of a constitutively active Akt. Thus, activation of a PI-3K/Akt signaling pathway is required for cytokine-dependent suppression of DNA-damage induced checkpoints. Together, these findings suggest a novel role for PI-3K/Akt pathways in the modulation of growth arrest responses to DNA damage in hematopoietic cells. (Blood. 2001;98:834-841)  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