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   23942篇
  免费   1891篇
  国内免费   76篇
耳鼻咽喉   409篇
儿科学   841篇
妇产科学   377篇
基础医学   2437篇
口腔科学   533篇
临床医学   2157篇
内科学   5272篇
皮肤病学   552篇
神经病学   1319篇
特种医学   1105篇
外国民族医学   1篇
外科学   4638篇
综合类   333篇
一般理论   15篇
预防医学   1155篇
眼科学   859篇
药学   2076篇
中国医学   38篇
肿瘤学   1792篇
  2023年   204篇
  2022年   309篇
  2021年   1039篇
  2020年   492篇
  2019年   831篇
  2018年   975篇
  2017年   638篇
  2016年   675篇
  2015年   693篇
  2014年   1041篇
  2013年   1219篇
  2012年   1803篇
  2011年   1772篇
  2010年   893篇
  2009年   836篇
  2008年   1302篇
  2007年   1225篇
  2006年   1144篇
  2005年   985篇
  2004年   885篇
  2003年   751篇
  2002年   646篇
  2001年   587篇
  2000年   550篇
  1999年   488篇
  1998年   160篇
  1997年   135篇
  1996年   138篇
  1995年   142篇
  1994年   113篇
  1993年   97篇
  1992年   267篇
  1991年   284篇
  1990年   248篇
  1989年   212篇
  1988年   208篇
  1987年   219篇
  1986年   192篇
  1985年   177篇
  1984年   111篇
  1983年   126篇
  1982年   85篇
  1981年   70篇
  1979年   129篇
  1978年   77篇
  1977年   69篇
  1975年   58篇
  1974年   65篇
  1973年   88篇
  1970年   58篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
1 A novel series of non-quaternary oxadiazole-based muscarinic agonists demonstrated high affinity for muscarinic receptors. 2. These agonists possessed high efficacy in the nanomolar range at muscarinic receptors in the superior cervical ganglion, atrium and ileum but did not show selectivity across the tissue preparations. 3. Two amino oxadiazoles, one from a quinuclidine series (L-660,863) and one from a 1-azanorbornane series (L-670,207) possessed a high ratio of potency for displacing the binding of [3H]-N-methyl-scopolamine ([3H]-NMS) to potency for displacing the agonist [3H]-oxotremorine-M cortex. 4. The two azanorbornane derivatives L-670,548 and L-670,207 stimulated the turnover of phosphatidylinositol in the cortex with a potency higher than that obtained with any other known muscarinic agonist (ED50 0.26 and 0.18 microM respectively). 5. The maximum response obtained with L-670,207 was greater than that observed for carbachol but was comparable to that of the natural ligand acetylcholine. 6. These oxadiazole muscarinic agonists are among the most potent and efficacious non-quaternary muscarinic agonists ever described.  相似文献   
92.
The dose-duration effect of nebulized nedocromil sodium was studied in ten patients with exercise-induced asthma (7 males mean (SEM) age 30.1 (3.5) yrs and predicted forced expiratory volume in one second (FEV1) 102%). All of these patients showed > 40% protection of their exercise asthma with 4 mg of nedocromil sodium delivered via metered dose inhaler. Three concentrations of nedocromil sodium (0.5, 2.5 and 10 mg.ml-1) and placebo were administered in double-blind, randomized manner. One ml of each solution was nebulized via a Wright nebulizer. Effects were assessed from the mean maximal percentage fall in FEV1 after 6-8 min treadmill exercise at 15, 135 and 255 min following each treatment and expressed as percentage protection. The mean baseline FEV1 values before and after treatments were comparable on four days of testing. Nedocromil sodium inhibited exercise-induced fall in FEV1 at all concentrations (p < 0.001) and the inhibitory effect was still present at 255 min. No differences were observed between active treatments.  相似文献   
93.
94.
95.
96.
Although functional and clinical outcomes after total ankle arthroplasty have been promising, a steep learning curve has been recognized. In addition, the performance of concomitant hindfoot realignment procedures is controversial. The purpose of this study was to report on a single surgeon's experience with the first 50 total ankle arthroplasty procedures. We wanted to define the characteristics of the learning curve and whether the rate of complications was increased in patients who required complex reconstruction for preexistent foot and ankle deformities. This was a retrospective study of 50 cases with an average follow-up of 24.2 months. The patient population consisted of 18 men and 30 women with an average age of 57.6 years. Twenty-six percent of the cases had concomitant bony realignment procedures, while 20% had prior history of major hindfoot corrective procedures. There were 19 cases with intraoperative malleolar fractures, 12 cases that exhibited some degree of malalignment, and 6 cases of syndesmotic nonunion, and 8 ankles required early component revision. Minor wound complications that resolved with local wound care occurred in 9 cases, while 1 patient had a major wound complication requiring flap coverage. Each of these complications, other than wound complications, decreased with the surgeon's experience. Our results also indicate that the performance of major realignment procedures at the same time of implant arthroplasty is not associated with an increased incidence of complications. The results of this study suggest that total ankle arthroplasty is associated with a learning curve. Perioperative complications may potentially decrease with surgeon experience.  相似文献   
97.
OBJECTIVE: Interstitial brachytherapy is becoming an accepted treatment option for lung cancer patients for whom surgery poses a high risk. Robotic surgery has the potential to deliver brachytherapy seeds into tumors while keeping surgeons at a safe distance from the radioactive source. Our aim was to compare the accuracy, number of attempts, and time needed to place seeds next to a target when using a manual technique, video-assisted thoracoscopic surgery (VATS), and the ZEUS robot for minimally invasive surgery (MIS). METHODS: A brachytherapy seed injector was developed and attached to one of the ZEUS robotic arms. Four subjects each inserted inactive dummy brachytherapy seeds into clear agar-gelatin cubes containing a 1.6-mm stainless steel ball target. Two orthogonal radiographs were taken of each agar cube, and the corresponding distances were measured in triplicate using ImageJ processing software. The mean distance between the center of each seed and the corresponding target was calculated using the Pythagorean theorem. Comparisons were made using analysis of variance, t-tests, and Kruskal-Wallis tests, as appropriate. RESULTS: A total of 384 tests (128 for each technique) were performed. The median accuracies for the manual technique, VATS, and ZEUS were 1.8 mm (range: 0.9-6.7 mm), 2.4 mm (range: 1.0-11.3 mm), and 3.6 mm (range: 1.3-16.7 mm), respectively (p < 0.01). The median numbers of attempts for the manual technique, VATS, and ZEUS were 1 (range: 1-5), 4 (range: 1-14), and 3 (range: 1-20), respectively (p < 0.01). The median times for the manual technique, VATS, and ZEUS were 3.0 s (range: 1-43 s), 86.5 s (range: 6-372 s), and 64.5 s (range: 5-356 s), respectively (p < 0.01). CONCLUSIONS: The manual technique is the most accurate, least traumatic, and fastest method of inserting seeds into tumors. The ZEUS robotic platform was able to place seeds beside a target within a clinically acceptable distance, with an acceptable amount of trauma and time required. It achieved results equal to or better than those obtained with VATS.  相似文献   
98.
A lump on the midface of a child can pose as a diagnostic dilemma. There is a wide variety of possible differential diagnoses, ranging from simple benign conditions such as a sebaceous cyst, dermoid cyst, lipoma, neuroma and neurofibroma, to potentially devastating conditions such as odontogenic myxoma.A case of a child in which the formulation of a definite diagnosis was clinically and histologically challenging is presented.  相似文献   
99.
BACKGROUND: Systemic vascular resistance (SVR) is an integral therapeutic component of patients with heart failure and shock. We hypothesized that the ratio of the peak mitral regurgitant velocity (MRV) (m/s) to left ventricular outflow time-velocity integral (TVI(LVOT)) (cm) by Doppler would provide a noninvasive correlate of SVR. METHODS: SVR was correlated to MRV/TVI(LVOT) in 33 patients undergoing right heart catheterization. Receiver operating characteristic curves were generated to determine the best-balanced sensitivity and specificity to identify SVR > 14 Wood units (WU) and <10 WU. RESULTS: MRV/TVI(LVOT) correlated well with SVR (r = 0.842, 95% confidence interval 0.7-0.92, P <.001, Y = 0.459 + 49.397*X). By receiver operating characteristics, MRV/TVI(LVOT) > 0.27 had a 70% sensitivity and a 77% specificity to identify SVR > 14 WU. MRV/TVI(LVOT) < 0.2 had a 92% sensitivity and a 88% specificity to identify SVR < 10 WU. CONCLUSION: Doppler echocardiography provides a reliable noninvasive assessment of SVR.  相似文献   
100.
PURPOSE: To evaluate the effects of dissolvable collagen punctal plugs on the symptoms, tear stability and volume in aqueous deficient dry eyes. METHODS: Sixty-two aqueous deficient dry eye patients of mixed aetiology underwent lacrimal punctal occlusion with dissolvable collagen plugs. The subjects were randomly allocated to one of two treatment groups: group I (n = 36) had their lower puncta occluded and group II (n = 26) had both their upper and lower puncta occluded. The effectiveness of this treatment was clinically assessed by (1). scoring subject symptoms and (2). measuring the tear parameters of tear thinning time (TTT) and tear meniscus height (TMH) as indicators of tear stability and volume, respectively. Following baseline measurements, patients were reviewed at time intervals of 5 and 12 days post-occlusion. A group of age- and gender-matched normals (n = 45) was recruited for comparison (group III). RESULTS: Tear volume and stability were significantly higher in group III compared with I and II at baseline. In the treated groups on both days 5 and 12: (1). symptom score reduced significantly from a median value of 7 to 3 (p = <0.001); (2). tear stability increased significantly from a median value of 3 to 5 s by day 5 (p 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