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   8472篇
  免费   512篇
  国内免费   37篇
耳鼻咽喉   96篇
儿科学   186篇
妇产科学   157篇
基础医学   928篇
口腔科学   139篇
临床医学   531篇
内科学   2490篇
皮肤病学   107篇
神经病学   855篇
特种医学   317篇
外科学   1057篇
综合类   49篇
一般理论   6篇
预防医学   639篇
眼科学   253篇
药学   561篇
  1篇
中国医学   19篇
肿瘤学   630篇
  2023年   59篇
  2022年   126篇
  2021年   266篇
  2020年   138篇
  2019年   235篇
  2018年   277篇
  2017年   208篇
  2016年   197篇
  2015年   254篇
  2014年   284篇
  2013年   442篇
  2012年   617篇
  2011年   597篇
  2010年   357篇
  2009年   316篇
  2008年   543篇
  2007年   562篇
  2006年   578篇
  2005年   510篇
  2004年   396篇
  2003年   382篇
  2002年   330篇
  2001年   145篇
  2000年   142篇
  1999年   112篇
  1998年   83篇
  1997年   58篇
  1996年   56篇
  1995年   40篇
  1994年   38篇
  1993年   27篇
  1992年   59篇
  1991年   56篇
  1990年   49篇
  1989年   54篇
  1988年   40篇
  1987年   37篇
  1986年   34篇
  1985年   30篇
  1984年   26篇
  1983年   28篇
  1982年   23篇
  1981年   20篇
  1980年   16篇
  1979年   27篇
  1978年   13篇
  1977年   16篇
  1974年   15篇
  1973年   13篇
  1970年   12篇
排序方式: 共有9021条查询结果,搜索用时 15 毫秒
991.
Chronic rhinosinusitis (CRS) is a common condition and affects the quality of life of approximately 16 % of adults in US and 10.9 % in Europe. Hyaluronan (HA) is a nonsulphate glycosaminoglycan found in the extracellular matrix of connective tissues, and plays an important role in the healing process and repair of mucosal surfaces. We aim to evaluate the effect of HA on nasal symptoms and endoscopic appearance in patients with CRS and nasal polyps (NP) who have not undergone sinus surgery. Eighty patients older than 18 years old were randomized to receive either open-label nebulized saline solution (NS) or intranasal corticosteroid spray (ICS) 200 µg bid or nebulized sodium hyaluronate (NHA, YABRO®) or both ICS and NHA. Results were collected at 1 month, 3 months and 3 months after treatment. Significant improvements in nasal symptoms scores, endoscopic appearance scores, radiologic scores, rhinomanometry and saccharine clearance test were observed in the NHA, ICS and ICS + NHA groups after 1 month and 3 months of treatment compared with baseline (all p ≤ 0.005). The use of oral steroids was significantly reduced after 3 months of therapy in the same groups versus baseline (all p < 0.05). The incidence of adverse events at 3 months was similar between the 4 groups (all p > 0.05). Throat irritation, nasal burning and drug-related epistaxis were not reported in the group NHA. HA, as a nebulized nasal douche preparation, improved nasal symptoms and endoscopic appearances in patients with CRS and NP who have not undergone sinus surgery.  相似文献   
992.

Statement of problem

Interim restorations are occasionally left in the mouth for extended periods and are susceptible to bacterial infiltration. Thus, dental interim cements with antibacterial properties are required.

Purpose

The purpose of this in vitro study was to determine in vitro antibacterial activity against Streptococcus mutans and to compare the diametrical tensile strength (DTSs) of dental interim cement modified with zinc oxide nanoparticles (ZnO-NPs) with that of cement modified with terpenes.

Material and methods

Antibacterial properties of ZnO-NPs, terpenes, and dental interim cement modified with ZnO-NPs and cement modified with terpenes against S mutans were tested according to minimum inhibitory concentration (MIC) and direct contact inhibition (DCI). Tensile strength levels were evaluated using DTS. Results were analyzed using the Kolmogorov-Smirnov, ANOVA, and Tamhane tests (α=.05).

Results

The MICs of ZnO-NPs and terpenes against S mutans were 61.94 μg/g and 0.25% v/v, respectively. The DCI assay under the cylinders of cement (area of contact with the agar surface) revealed significant bacterial growth inhibition on Temp-Bond NE specimens with ZnO-NPs at MIC of 495.2 μg/g (8× MIC) and with terpenes at MIC 0.999% v/v (4× MIC) (P<.05). The Temp-Bond NE cement cylinder (control group) showed the lowest DTS (1.05 ±0.27 MPa) of all other test groups. In the Zn-NPs group, the greatest increase occurred in the NP8 (8× MIC; 495.2 μg/g) group with a value of 1.50 ±0.23 MPa, a significant increase in DTS compared with the control and terpene groups (P<.05). In the terpene group, the highest increase corresponded to group T2 (2× MIC; 0.4995% v/v) with a value of 1.29 ±0.18 MPa.

Conclusions

The addition of terpenes and ZnO-NPs to interim cement showed antibacterial activity when in contact with S. mutans ATCC 25175. Both terpenes and ZnO-NPs antimicrobial agents increased diametral tensile strength.  相似文献   
993.
The electron donor–acceptor properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl) anthracene (BP4VA) are studied by means of surface-enhanced Raman scattering (SERS) spectroscopy and vibronic theory of resonance Raman spectroscopy. The SERS spectra recorded in an electrochemical cell with a silver working electrode have been interpreted on the basis of resonance Raman vibronic theory assisted by DFT calculations. It is demonstrated that the adsorbate–metal interaction occurs through the nitrogen atom of the pyridyl moiety. Concerning the electron donor–acceptor properties of the adsorbate, it is shown that the charge transfer excited states of BP4VA are not optically active, in contrast, an internal transition to an excited state of BP4VA, which is localized in the anthracene framework, is strongly allowed. The charge transfer states will be populated by an ultrafast non-radiative process, that is, internal conversion. Thus, irradiation of BP4VA interacting with an appropriate surface creates an effective charge separation.

Surface enhanced Raman spectroscopy in conjunction with quantum chemistry is a valuable tool for characterization of organic functional materials.  相似文献   
994.

Objectives

To evaluate feasibility, accuracy and reproducibility of combined US-MR of the breast using volume navigation technique.

Subjects and methods

Five healthy females underwent bilateral contrast-enhanced MR (CE-MR) of the breast in supine position, after positioning three couples of markers on the breast. After CE-MR data uploading in the ultrasound (US) database, manual co-registration was obtained during live US of the breast by means of an electromagnetic transmitter positioned near the subject under examination and two electromagnetic sensors were mounted on the transducer bracket. Transmitter and sensors were connected to a position-sensing unit embedded in the US equipment allowing to track probe position and orientation within the electromagnetic field. Live US image were co-registered to the previously loaded breast CE-MR volume by coupling markers. For each subject, two independent radiologists recorded the examination time and verified twice image alignment using five fixed checkpoints. Pair t Student test and Wilcoxon test were used for statistical analysis.

Results

In all subjects US and CE-MR images were successfully combined. The examination time was 10 ± 2 vs. 9 ± 4 min, respectively (p = 0.642; NS). A total of one hundred measurements of images misalignment were performed: the measurements recorded between the two operators were 0.42 ± 0.32 cm and 0.58 ± 0.41 cm (p = 0.161; NS), and 0.50 ± 0.32 cm and 0.56 ± 0.52 cm (p = 0.928; NS), respectively.

Discussion

In our preliminary experience, volume navigation technique appears to be a accurate and reproducible method to combine CE-MR image during unilateral US of the breast.  相似文献   
995.

Objectives  

To estimate the diagnostic accuracy of magnetic resonance imaging (MRI) in detecting additional lesions and contralateral cancer not identified using conventional imaging in primary breast cancer.  相似文献   
996.
997.
998.
Because many words are typically used in the context of their referent objects and actions, distributed cortical circuits for these words may bind information about their form with perceptual and motor aspects of their meaning. Previous work has demonstrated such semantic grounding for sensorimotor, visual, auditory, and olfactory knowledge linked to words, which is manifest in activation of the corresponding areas of the cortex. Here, we explore the brain basis of gustatory semantic links of words whose meaning is primarily related to taste. In a blocked functional magnetic resonance imaging design, Spanish taste words and control words matched for a range of factors (including valence, arousal, imageability, frequency of use, number of letters and syllables) were presented to 59 right-handed participants in a passive reading task. Whereas all the words activated the left inferior frontal (BA44/45) and the posterior middle and superior temporal gyri (BA21/22), taste-related words produced a significantly stronger activation in these same areas and also in the anterior insula, frontal operculum, lateral orbitofrontal gyrus, and thalamus among others. As these areas comprise primary and secondary gustatory cortices, we conclude that the meaning of taste words is grounded in distributed cortical circuits reaching into areas that process taste sensations.  相似文献   
999.

Background and Objective:

Studies on the role of laparoscopy in secondary or tertiary cytoreduction for recurrent ovarian cancer are limited. Our objective is to describe our preliminary experience with laparoscopic secondary/tertiary cytoreduction in patients with recurrent ovarian, fallopian, and primary peritoneal cancers.

Methods:

This is a retrospective analysis of a prospective case series. Women with recurrent ovarian, fallopian tube, or primary peritoneal cancers deemed appropriate candidates for laparoscopic debulking by the primary surgeon(s) were recruited. The patients underwent exploratory video laparoscopy, biopsy, and laparoscopic secondary/tertiary cytoreduction between June 1999 and October 2009. Variables analyzed include stage, site of disease, extent of cytoreduction, operative time, blood loss, length of hospital stay, complications, and survival time.

Results:

Twenty-three patients were recruited. Only one surgery involved conversion to laparotomy. Seventeen (77.3%) of the patients had stage IIIC disease at the time of their initial diagnosis, and 20 (90.9%) had laparotomy for primary debulking. Median blood loss was 75 mL, median operative time 200 min, and median hospital stay 2 d. No intraoperative complications occurred. One patient (4.5%) had postoperative ileus. Eighteen (81.8%) of the patients with recurrent disease were optimally cytoreduced to < 1cm. Overall, 12 patients have no evidence of disease (NED), 6 are alive with disease (AWD), and 4 have died of disease (DOD), over a median follow-up of 14 mo. Median disease-free survival was 71.9 mo.

Conclusions:

In a well-selected population, laparoscopy is technically feasible and can be utilized to optimally cytoreduce patients with recurrent ovarian, fallopian, or primary peritoneal cancers.  相似文献   
1000.
Background: Classically, the vertical-style reduction mammaplasty utilizing a superomedial pedicle has been limited to smaller reductions secondary to concerns for poor wound healing and nipple necrosis. Objectives: The authors reviewed a large cohort of patients who underwent a vertical-style superomedial pedicle reduction mammaplasty in an attempt to demonstrate its safety and efficacy in treating symptomatic macromastia. Methods: A retrospective review was performed of 290 patients (558 breasts) who underwent a vertical-style superomedial pedicle reduction mammaplasty. All procedures were conducted by one of 4 plastic surgeons over 6 years (JDR, MAA, DLV, DRA). Results: The average resection weight was 551.7 g (range, 176-1827 g), with 4.6% of resections greater than 1000 g. A majority of patients (55.2%) concomitantly underwent liposuction of the breast. The total complication rate was 22.7%, with superficial dehiscence (8.8%) and hypertrophic scarring (8.8%) comprising the majority. Nipple sensory changes occurred in 1.6% of breasts, with no episodes of nipple necrosis. The revision rate was 2.2%. Patients with complications had significantly higher resection volumes and nipple-to-fold distances (P = .014 and .010, respectively). Conclusions: The vertical-style superomedial pedicle reduction mammaplasty is safe and effective for a wide range of symptomatic macromastia. The nipple-areola complex can be safely transposed, even in patients with larger degrees of macromastia, with no episodes of nipple necrosis. The adjunctive use of liposuction should be considered safe. Last, revision rates were low, correlating with a high level of patient satisfaction.  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