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   7687篇
  免费   693篇
  国内免费   17篇
耳鼻咽喉   64篇
儿科学   379篇
妇产科学   226篇
基础医学   901篇
口腔科学   143篇
临床医学   919篇
内科学   1309篇
皮肤病学   63篇
神经病学   716篇
特种医学   309篇
外科学   1265篇
综合类   174篇
一般理论   2篇
预防医学   727篇
眼科学   165篇
药学   551篇
中国医学   4篇
肿瘤学   480篇
  2021年   97篇
  2020年   64篇
  2019年   101篇
  2018年   123篇
  2017年   89篇
  2016年   97篇
  2015年   114篇
  2014年   143篇
  2013年   257篇
  2012年   295篇
  2011年   338篇
  2010年   193篇
  2009年   157篇
  2008年   309篇
  2007年   328篇
  2006年   343篇
  2005年   297篇
  2004年   291篇
  2003年   272篇
  2002年   261篇
  2001年   282篇
  2000年   286篇
  1999年   269篇
  1998年   150篇
  1997年   116篇
  1996年   117篇
  1995年   107篇
  1994年   92篇
  1993年   78篇
  1992年   192篇
  1991年   179篇
  1990年   179篇
  1989年   156篇
  1988年   170篇
  1987年   140篇
  1986年   152篇
  1985年   141篇
  1984年   135篇
  1983年   107篇
  1982年   69篇
  1981年   69篇
  1980年   50篇
  1979年   109篇
  1978年   70篇
  1977年   67篇
  1976年   50篇
  1975年   70篇
  1974年   74篇
  1973年   77篇
  1972年   62篇
排序方式: 共有8397条查询结果,搜索用时 15 毫秒
91.
Epidural fentanyl after a lidocaine and epinephrine test dose provides adequate analgesia and allows for ambulation during early labor. This study was designed to determine the influence of an epidural infusion of bupivacaine plus fentanyl administered after initiation of epidural labor analgesia with fentanyl. Specifically, we evaluated whether there is an increase in motor block or an increased time to request for further analgesic medication. Fifty-one laboring primigravid women at <5 cm cervical dilation who requested epidural analgesia were enrolled. After a 3-mL epidural test dose of 1.5% lidocaine with epinephrine (5 microg/mL), patients received fentanyl 100 microg via the epidural catheter. They then randomly received either an infusion (10 mL/h) of 0.0625% bupivacaine with fentanyl (3 microg/mL) or an infusion of preservative-free saline. After the administration of the initial analgesic, pain scores and side effects were recorded for each patient at 10, 20, and 30 min, every 30 min thereafter, and at the time of request for additional analgesic medication, by an observer blinded to the technique used. There were no demographic differences between the two groups. The mean duration of analgesia (time from initial dose to request for additional analgesia) was increased in the group that received a continuous infusion of bupivacaine and fentanyl compared with the Saline group (198 +/- 86 vs 145 +/- 50 min; P < 0.009). Side effects were similar between the two groups. No patient in either group experienced any detectable motor block. Fourteen patients chose to ambulate in the Saline group, and 12 patients chose to ambulate in the Infusion group. In early laboring patients, a continuous infusion of 0.0625% bupivacaine infusion with fentanyl (3 microg/mL) prolonged the duration until top-up was required, after epidural fentanyl 100 microg after a lidocaine and epinephrine test dose, and did not cause any clinically detectable motor block. IMPLICATIONS: A 0.0625% bupivacaine and fentanyl (3 microg/mL) infusion, when added to epidural fentanyl (100 microg), prolongs the analgesic duration without increasing motor block in women in early labor.  相似文献   
92.
OBJECTIVE: To determine outcome in diabetic pancreas transplant recipients according to risk factors and the surgical techniques and immunosuppressive protocols that evolved during a 33-year period at a single institution. SUMMARY BACKGROUND DATA: Insulin-dependent diabetes mellitus is associated with a high incidence of management problems and secondary complications. Clinical pancreas transplantation began at the University of Minnesota in 1966, initially with a high failure rate, but outcome improved in parallel with other organ transplants. The authors retrospectively analyzed the factors associated with the increased success rate of pancreas transplants. METHODS: From December 16, 1966, to March 31, 2000, the authors performed 1,194 pancreas transplants (111 from living donors; 191 retransplants): 498 simultaneous pancreas-kidney (SPK) and 1 simultaneous pancreas-liver transplant; 404 pancreas after kidney (PAK) transplants; and 291 pancreas transplants alone (PTA). The analyses were divided into five eras: era 0, 1966 to 1973 (n = 14), historical; era 1, 1978 to 1986 (n = 148), transition to cyclosporine for immunosuppression, multiple duct management techniques, and only solitary (PAK and PTA) transplants; era 2, 1986 to 1994 (n = 461), all categories (SPK, PAK, and PTA), predominantly bladder drainage for graft duct management, and primarily triple therapy (cyclosporine, azathioprine, and prednisone) for maintenance immunosuppression; era 3, 1994 to 1998 (n = 286), tacrolimus and mycophenolate mofetil used; and era 4, 1998 to 2000 (n = 275), use of daclizumab for induction immunosuppression, primarily enteric drainage for SPK transplants, pretransplant immunosuppression in candidates awaiting PTA. RESULTS: Patient and primary cadaver pancreas graft functional (insulin-independence) survival rates at 1 year by category and era were as follows: SPK, era 2 (n = 214) versus eras 3 and 4 combined (n = 212), 85% and 64% versus 92% and 79%, respectively; PAK, era 1 (n = 36) versus 2 (n = 61) versus 3 (n = 84) versus 4 (n = 92), 86% and 17%, 98% and 59%, 98% and 76%, and 98% and 81%, respectively; in PTA, era 1 (n = 36) versus 2 (n = 72) versus 3 (n = 30) versus 4 (n = 40), 77% and 31%, 99% and 50%, 90% and 67%, and 100% and 88%, respectively. In eras 3 and 4 combined for primary cadaver SPK transplants, pancreas graft survival rates were significantly higher with bladder drainage (n = 136) than enteric drainage (n = 70), 82% versus 74% at 1 year (P =.03). Increasing recipient age had an adverse effect on outcome only in SPK recipients. Vascular disease was common (in eras 3 and 4, 27% of SPK recipients had a pretransplant myocardial infarction and 40% had a coronary artery bypass); those with no vascular disease had significantly higher patient and graft survival rates in the SPK and PAK categories. Living donor segmental pancreas transplants were associated with higher technically successful graft survival rates in each era, predominately solitary (PAK and PTA) in eras 1 and 2 and SPK in eras 3 and 4. Diabetic secondary complications were ameliorated in some recipients, and quality of life studies showed significant gains after the transplant in all recipient categories. CONCLUSIONS: Patient and graft survival rates have significantly improved over time as surgical techniques and immunosuppressive protocols have evolved. Eventually, islet transplants will replace pancreas transplants for suitable candidates, but currently pancreas transplants can be applied and should be an option at all stages of diabetes. Early transplants are preferable for labile diabetes, but even patients with advanced complications can benefit.  相似文献   
93.
Morris DS  Dunn RL  Schuster TG  Ohl DA  Smith GD 《The Journal of urology》2007,178(5):2087-91; discussion 2091
PURPOSE: The motility of testicular derived spermatozoa reflects viability and predicts success during intracytoplasmic sperm injection. Although improvements in sperm motility are seen after incubation for extended periods, no guidelines suggest duration or media use for optimal improvement in motility. MATERIALS AND METHODS: Between July 1999 and February 2005 testicular aspirations were performed on 95 men with azoospermia, including 51 with obstructive azoospermia and 44 with nonobstructive azoospermia. Sperm motility was determined at initial collection and following incubation for 24 or 48 hours in processing media or Ham's F10 + protein. A mixed regression model controlling for testis side, media and baseline motility was created to analyze the change in motility between 24 and 48 hours. RESULTS: Mean motility improved from 3% to 20% at 24 hours and 25% at 48 hours for OA cases and from 0% to 5% at 24 hours and 11% at 48 hours for nonobstructive azoospermia cases. The improvement in motility from 24 to 48 hours was significant for obstructive azoospermia cases (p = 0.001). While media was a nonsignificant factor in regression models, when patients were grouped into categories of motility change there was a significantly better response to F10 compared to processing media (p = 0.03). CONCLUSIONS: Incubation in processing media or Ham's F10 + albumin media improves sperm motility with significant improvement noted between 24 and 48 hours for obstructive azoospermia cases. Ham's F10 + albumin media may provide extra benefit for cases of nonobstructive azoospermia or nerve injury. These results suggest the ideal timing of oocyte retrieval for intracytoplasmic sperm injection correlates with 48-hour sperm incubation for obstructive azoospermia cases, and 24 hours for nonobstructive azoospermia and nerve injury cases.  相似文献   
94.
PURPOSE: The diffusion of laparoscopic renal surgery has been gradual. While surgery for benign and malignant kidney disease is usually within the urological domain, donor nephrectomy is multidisciplinary. Therefore, we compared the use of laparoscopy by procedure indication (kidney donor, and benign and malignant kidney disease) to examine potential specialty specific associations with the slow uptake of this technology. MATERIALS AND METHODS: Data on 53,461 patients undergoing nephrectomy for all indications between 1998 and 2003 were abstracted from the Nationwide Inpatient Sample using International Classification of Diseases, 9th Revision, Clinical Modification procedure and diagnostic codes. Generalized estimating equations were fitted to measure the association between laparoscopy use and the procedure indication (kidney donor, benign kidney disease and kidney cancer). RESULTS: The use of laparoscopy varied by treatment indication. In 2003, 33% of kidney donors underwent a laparoscopic approach compared to 22% and 16% of patients with benign and malignant kidney disease, respectively (p <0.0001). After adjusting for patient and hospital differences patients with benign (adjusted OR 0.71, 95% CI 0.58-0.94) and malignant (adjusted OR 0.51, 95% CI 0.35-0.74) kidney disease were significantly less likely to undergo laparoscopic nephrectomy than kidney donors. CONCLUSIONS: These data highlight that the use of laparoscopic renal surgery varies by procedure indication with slower adoption of laparoscopy for malignant or benign indications than for donor nephrectomy. This variation was not readily explained by differences in measurable patient and hospital factors. Further characterization of provider and nonclinical characteristics may provide additional insight into differences in the adoption of this technology, which appears to be a specialty specific phenomenon.  相似文献   
95.
PURPOSE: Autologous fascia, Pelvicol implant and polypropylene are common materials used in suburethral anti-incontinence procedures. We explored the relative effectiveness of the autologous fascia pubovaginal sling, Pelvicol pubovaginal sling and Gynecare TVT on self-reported postoperative urinary incontinence. MATERIALS AND METHODS: The study was a mailed cross-sectional survey of health related quality of life 1 to 3 years after suburethral anti-incontinence surgery performed at our institution. The Incontinence Symptom Index was used to assess the presence and severity of urinary incontinence symptoms and the Incontinence Impact Questionnaire-7 was used to assess impairment. Regression models were developed to identify factors with an independent effect on the presence, severity and impairment of urinary incontinence symptoms. RESULTS: The questionnaire was returned by 69% of eligible respondents (173 of 250). Those with previous incontinence surgery (OR 11.0, 95% CI 2.3-51.4) and medical comorbidities (OR 1.6, 95% CI 1.1-2.2) were more likely to report urinary incontinence symptoms, ie incontinence symptom index greater than 0. Symptom severity, which was analyzed only in respondents with urinary incontinence symptoms, was greater in the Pelvicol than in the autologous fascia pubovaginal sling and TVT groups (each p <0.01). No significant difference was observed between the TVT and autologous fascia pubovaginal sling groups (p = 0.15). Also associated with higher urinary incontinence symptom severity scores were body mass index (p = 0.03), a history of incontinence surgery (p = 0.01) and lower education (p <0.01). Impairment from urinary incontinence, as assessed by the Incontinence Impact Questionnaire-7, was associated with body mass index, severe depression and current smoking (each p = 0.01) but not with surgical treatment group. CONCLUSIONS: Women who received an autologous fascia pubovaginal sling or TVT reported lower symptom severity scores than those who had a Pelvicol pubovaginal sling. Impairment was not associated with procedure type. These findings suggest better outcomes with autologous fascia pubovaginal sling and TVT. Randomized, controlled trials are needed to confirm these findings.  相似文献   
96.
97.
The role of laparoscopy in penetrating abdominal trauma.   总被引:1,自引:0,他引:1  
BACKGROUND: Minimally invasive surgery has become increasingly utilized in the trauma setting. When properly applied, it offers several advantages, including reduced morbidity, lower rates of negative laparotomy, and shortened length of hospital stay. The purpose of this study was to evaluate the role of laparoscopy in the management of trauma patients with penetrating abdominal injuries. METHODS: We conducted a 3-year retrospective chart review of 4541 trauma patients admitted to our urban Level II trauma center. Penetrating abdominal injuries accounted for 209 of these admissions. Patients were divided into 3 treatment groups based on the characteristics of their abdominal injuries. Management was either observation, immediate laparotomy, or screening laparoscopy. RESULTS: Thirty-three patients were observed in the Emergency Department based on their initial physical examination and radiologic studies. After Emergency Department evaluation, 154 patients underwent immediate laparotomy. In this group, 119 therapeutic laparotomies, 11 nontherapeutic laparotomies, and 24 negative laparotomies were performed. A review of the negative laparotomies revealed that possibly 8 of 10 gun shot wounds and all 14 stab wounds could have been done laparoscopically. Twenty-two patients underwent laparoscopic evaluation, 9 of which were converted to open procedures. CONCLUSION: Minimally invasive surgical techniques are particularly helpful as a screening tool for anterior abdominal wall wounds and lower chest injuries to rule out peritoneal penetration. Increased use of laparoscopy in select patients with penetrating abdominal trauma will decrease the rate of negative and nontherapeutic laparotomies, thus lowering morbidity and decreasing length of hospitalization. As technology and expertise among surgeons continues to improve, more therapeutic intervention may be done laparoscopically in the future.  相似文献   
98.
The human T-lymphotropic virus type III (HTLV-III) is the primary cause of the acquired immunodeficiency syndrome (AIDS) and related disorders (ARC). Prior studies have reported that nearly all symptomatic patients with AIDS or ARC manifest antibody to HTLV-III. This observation has engendered efforts to screen for HTLV-III, especially prior to blood donation, with assays for antibody to HTLV-III. We report the first two cases, one with AIDS and one with ARC, that are HTLV-III virus positive but antibody negative. Accurate diagnosis of HTLV-III infection in some cases may require direct virus culture or tests for antigen. In addition, lack of HTLV-III antibody may indicate an atypical clinical course of AIDS.  相似文献   
99.
In order to assess blood factors which might explain why some cigarette smokers develop airflow obstruction while others do not, we compared two groups of PiM phenotype volunteers matched for age, sex and total pack-years of cigarette smoking; one group had airflow obstruction and the other did not. Functional levels of alpha-2-macroglobulin (alpha-2-M) and alpha-1-protease inhibitor (alpha-1-PI) were separately assessed by a protease binding procedure. Neutrophils were isolated from blood by counterflow centrifugation, and their elastase content was assayed with 3H-elastin-SDS (sodium dodecyl sulfate). The obstructed and nonobstructed groups were not different with respect to functional or immunoreactive levels of alpha-1-PI and alpha-2-M or elastase levels in their neutrophils. We do not find imbalances of circulating elastase or antielastase levels in PiM phenotype smokers with airflow obstruction.  相似文献   
100.
Systemic immunization with gram-negative organisms enhances the subsequent pulmonary clearance of these organisms. We studied the early time course of this phenomenon and related it to the time of appearance of polymorphonuclear leukocytes (PMN) and anti-Pseudomonas antibody in bronchoalveolar lavage (BAL). Mice were immunized intraperitoneally twice, separated by 1 wk, with 10(8) formalin-treated Pseudomonas aeruginosa. Two weeks later, they received an intrabronchial inoculum of 2.9 X 10(6) or 4.6 X 10(7) Pseudomonas organisms. Two, 4, and 6 h later, clearance and total PMN and anti-Pseudomonas antibody in the BAL were assessed. Clearance was enhanced in immunized mice at the lower inoculum. At the higher inoculum, bacteria were growing in lungs of both groups, although they were inhibited in immunized mice. Total PMN in the BAL increased progressively in both groups of mice, but net recruitment was diminished with the high inoculum. There were significant differences in the PMN in the BAL between control and immunized mice with high inoculum. Anti-Pseudomonas IgG first appeared in the BAL at 2 h, anti-Pseudomonas IgM at 6 h. These data suggest that anti-Pseudomonas IgG is an effective early pulmonary opsonin. Further, with high inoculums, immunization may aid pulmonary defenses by diminishing the magnitude of the decrement of PMN in the lung.  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