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   7803篇
  免费   381篇
  国内免费   45篇
耳鼻咽喉   193篇
儿科学   163篇
妇产科学   150篇
基础医学   929篇
口腔科学   71篇
临床医学   555篇
内科学   2281篇
皮肤病学   52篇
神经病学   598篇
特种医学   273篇
外科学   1369篇
综合类   71篇
预防医学   341篇
眼科学   114篇
药学   537篇
中国医学   15篇
肿瘤学   517篇
  2023年   55篇
  2022年   277篇
  2021年   438篇
  2020年   132篇
  2019年   187篇
  2018年   258篇
  2017年   174篇
  2016年   209篇
  2015年   237篇
  2014年   284篇
  2013年   373篇
  2012年   525篇
  2011年   552篇
  2010年   297篇
  2009年   239篇
  2008年   408篇
  2007年   435篇
  2006年   442篇
  2005年   397篇
  2004年   376篇
  2003年   333篇
  2002年   266篇
  2001年   131篇
  2000年   119篇
  1999年   92篇
  1998年   42篇
  1997年   35篇
  1996年   31篇
  1995年   30篇
  1994年   24篇
  1992年   58篇
  1991年   48篇
  1990年   54篇
  1989年   42篇
  1988年   53篇
  1987年   51篇
  1986年   35篇
  1985年   50篇
  1984年   32篇
  1983年   34篇
  1982年   21篇
  1981年   20篇
  1979年   51篇
  1978年   32篇
  1977年   21篇
  1976年   24篇
  1975年   24篇
  1974年   29篇
  1973年   34篇
  1972年   25篇
排序方式: 共有8229条查询结果,搜索用时 0 毫秒
101.
Glulam beams are increasingly used in the construction industry because of their high strength and the possibility of using round timber with smaller cross-sections. The load-bearing capacity of beams is strongly related to the quality of the outer layers and, in the case of wood, especially the tension zones. For these reasons, this study decided to replace the outer lamella with tensile plywood. The produced beams were subjected to static bending strength and modulus of elasticity evaluation. It was shown that the best static bending strength values were obtained for beams containing plywood in the tension layer. However, the change in structure in the tension zone of beams made of glued laminated timber results not only in an increase in the load capacity of elements produced in this way but also in a decrease in the range/range of the obtained results of bending strength. This way of modifying the construction of glued laminated beams allows a more rational use of available pine timber.  相似文献   
102.
ObjectiveManagement of postoperative pain after head and neck cancer surgery is a complex issue, requiring a careful balance of analgesic properties and side effects. The objective of this review is to discuss the efficacy and safety of multimodal analgesia (MMA) for these patients.MethodsPubmed, Cochrane, Embase, Scopus, and clinicaltrials.gov were systematically searched for all comparative studies of patients receiving MMA (nonsteroidal anti‐inflammatory drugs (NSAIDs), acetaminophen, anticonvulsants, local anesthetics, and corticosteroids) for head and neck cancer surgeries. The primary outcome was additional postoperative opioid usage, and secondary outcomes included subjective pain scores, complications, adverse effects, and 30‐day outcomes.ResultsA total of five studies representing 592 patients (MMA, n = 275; non‐MMA, n = 317) met inclusion criteria. The most commonly used agents were gabapentin, NSAIDs, and acetaminophen (n = 221), NSAIDs (n = 221), followed by corticosteroids (n = 35), dextromethorphan (n = 40), and local nerve block (n = 19). Four studies described a significant decrease in overall postoperative narcotic usage with two studies reporting a significant decrease in hospital time. Subjective pain scores widely varied with two studies reporting reduced pain at postoperative day 3. There were no differences in surgical outcomes, medical complications, adverse effects, or 30‐day mortality and readmission rates.ConclusionMMA is an increasingly popular strategy that may reduce dependence on opioids for the treatment of postoperative pain. A variety of regimens and protocols are available for providers to utilize in the appropriate head and neck cancer patient.  相似文献   
103.
Antimony and potassium manganate(VII) compositions are widely used in time delay elements of detonators. Despite the existing literature on such systems, there is no complete information on the burning process of Sb/KMnO4 compositions in closed systems. There are also no data on the heat of their combustion in conditions of increased pressure without the access of oxygen from the air and on the composition of solid combustion products. These issues are the subject of the presented work.  相似文献   
104.
The goals of this study have been to determine the prevalence of the bipolar spectrum features in the population of women with postpartum depression (PPD) symptoms, as well as to analyze the personality differences between putative ‘unipolar’ and ‘bipolar’ PPD subjects. The sample enrolled into the cross-sectional study consisted of 344 women at 6–12 weeks postpartum. The authors used the Edinburgh Postnatal Depression Scale (EPDS; cut-off score: 13 pts.) for the assessment of the PPD symptoms, the Mood Disorder Questionnaire (MDQ; cut-off scores: 7 or 8 pts.) for diagnosing the bipolar features, and the NEO-Five Factor Inventory (NEO-FFI) for the assessment of personality traits. The EPDS-positive subjects were more likely to score positively on the MDQ, as compared to the EPDS-negative ones. The EPDS-positive subjects who also scored ≥8 pts. on the MDQ were characterized by higher index of neuroticism, as compared to those who scored positively on the EPDS only. The results suggest that the presence of PPD symptoms is related to significantly higher scores of bipolarity and neuroticism. The more robust trait of neuroticism might be a marker of the ‘bipolar’ PPD, as compared to the ‘unipolar’ form of the disorder.  相似文献   
105.
Sackner-Bernstein JD  Kowalski M  Fox M  Aaronson K 《JAMA》2005,293(15):1900-1905
Context  Nesiritide improves symptoms in patients with acutely decompensated heart failure compared with placebo and appears to be safer than dobutamine. Its short-term safety relative to standard diuretic and vasodilator therapies is less clear. Objective  To investigate the safety of nesiritide relative to noninotrope-based control therapies, primarily consisting of diuretics or vasodilators. Data Sources  Primary reports of completed clinical trials as of December 2004 were obtained from the US Food and Drug Administration (FDA), the study sponsor (Scios Inc), a PubMed literature search using the terms nesiritide, clinical trials, and humans, and a manual search of annual meetings of 3 heart associations. Study Selection  Of 12 randomized controlled trials evaluating nesiritide, 3 met all inclusion criteria: randomized double-blind study of patients with acutely decompensated heart failure, therapy administered as single infusion (6 hours), inotrope not mandated as control, and reported 30-day mortality. Data Extraction  Data were extracted from FDA and sponsor documents and corroborated with published articles when available. Thirty-day survival was assessed by meta-analysis using a fixed-effects model and time-dependent risk by Kaplan-Meier analysis with Cox proportional hazards regression modeling. Where deaths were described within a range of days after treatment, an extreme assumption was made favoring nesiritide over control therapy, an approach relevant to the time-dependent analyses. Data Synthesis  In the 3 trials, 485 patients were randomized to nesiritide and 377 to control therapy. Death within 30 days tended to occur more often among patients randomized to nesiritide therapy (35 [7.2%] of 485 vs 15 [4.0%] of 377 patients; risk ratio from meta-analysis, 1.74; 95% confidence interval [CI], 0.97-3.12; P = .059; and hazard ratio after adjusting for study, 1.80; 95% CI, 0.98-3.31; P = .057). Conclusions  Compared with noninotrope-based control therapy, nesiritide may be associated with an increased risk of death after treatment for acutely decompensated heart failure. The possibility of an increased risk of death should be investigated in a large-scale, adequately powered, controlled trial before routine use of nesiritide for acutely decompensated heart failure.   相似文献   
106.
Numerous studies have shown that the geometry of micro-joints significantly affects the strength of the so joined timber element. The bending strength increases by creating a larger bonding area by increasing the length of the wedge joint. Although this type of joint has been successfully used for many years, it can still be troublesome to make. For these reasons, the present study investigated an easy-to-fabricate wedge joint, which we folded during the beams’ formation and glued with the same adhesive as the individual lamellas. Although the research has not fully answered all the questions relevant to both scientific and technological curiosity, it indicates the great potential of this solution. Following the principle adopted in the ongoing wood optimisation work, we concluded that the beams of the target cross-section should be produced, and it should only be possible to cut them to a certain length. In this approach, we only removed defects at critical points for the beam structure and, in this way, up to 30% of the timber processed could be saved or better utilised.  相似文献   
107.
Wool of mountain sheep, treated nowadays as a waste or troublesome byproduct of sheep husbandry, was used for the production of sound-absorbing materials. Felts of two different thicknesses were produced from loose fibres. Additionally, two types of yarn, ring spun and core rug, were obtained. The yarns were used for the production of tufted fabric with cut and loop piles. During the examinations, basic parameters of the obtained materials were determined. Then, according to standard procedure with the use of impedance tube, the sound absorption coefficient was measured, and the noise reduction coefficient (NRC) was calculated. It was revealed that felt produced from coarse wool exhibits high porosity, and its sound absorbing capacity is strongly related to the felt thickness. For thicker felt the NRC achieved 0.4, which is comparable with the NRC of commercial ceiling tiles. It was shown that the crucial parameter influencing the sound absorption of the tufted fabrics was the pile height. For both types of yarns, when the height of the pile was increased from 12 to 16 mm, the NRC increased from 0.4 to 0.42. The manufactured materials made from local wool possess good absorption capacity, similar to commercial products usually made from more expensive wool types. The materials look nice and can be used for noise reduction as inner acoustic screens, panels, or carpets.  相似文献   
108.

Background

Laparoscopic splenic vessel-preserving distal pancreatectomy (lap-SVPDP) is a popular procedure in pancreatic surgery. However, postoperative complications include false aneurysms of the splenic artery, splenic vein stenosis and thrombosis, pancreatic fistulas, abscess, and perigastric varices.

Methods

Eight patients (three men, five women, average age 66.1 years) with benign tumors underwent lap-SVPDP. Lap-SVPDP was performed in the lithotomy position with the head slightly elevated. The splenic vein was peeled longitudinally toward the pancreatic tail. A vessel-sealing system was used to detach the pancreatic body from the greater omentum, and the pancreas was transected using a surgical stapler.

Results

Mean operation time was 254 min; mean blood loss was 163 ml; and mean post-surgical hospitalization time was 13 days. No postoperative bleeding from the preserved splenic vessels occurred, and there were no splenic infarcts or splenic abscesses.

Conclusions

For safe performance of lap-SVPDP, the posterior surface of the pancreas should be completely exposed. The splenic vein should be ‘peeled away’, starting from its central rear, enabling easy detection of its course to avoid inadvertent sealing. With improved operational techniques, lap-SVPDP can be adopted as a standard procedure in pancreatic surgery.  相似文献   
109.
Of the 47 prefectures in Japan, Iwate had the fewest cases of coronavirus disease 2019 (COVID-19), with the first diagnosis officially confirmed on July 28, 2020. A baseline serological survey of COVID-19 antibodies is essential to accurately evaluate an epidemic outbreak. The primary purpose of this study was to determine pre-epidemic prevalence of COVID-19 antibodies among healthcare workers, using two laboratory-based quantitative tests. In addition, a point-of-care (POC) qualitative test, rapid, simple, and convenient for primary care clinics, was compared with the laboratory-based tests. All antibody tests were performed on serum from 1,000 healthcare workers (mean age, 40 ± 11 years) in Iwate Prefectural Central Hospital, May 29-31, 2020. A COVID-19 case was defined as showing positive results in both laboratory-based quantitative tests. None of 1,000 samples had positive results in both of the laboratory immunoassays. The POC test showed positive results in 33 of 1,000 samples (3.3%) (95% confidence interval: 2.19-4.41), but no samples were simultaneously positive in both laboratory-based tests. In conclusion, COVID-19 cases were not serologically confirmed by a baseline control study of healthcare workers at our hospital in late May, 2020. Moreover, the POC qualitative test may offer no advantage in areas with very low prevalence of COVID-19, due to higher false-positive reactions compared with laboratory-based quantitative immunoassays.  相似文献   
110.
Cervical cancer is one of the leading causes of death among women suffering from tumors. Current treatment options are insufficient. Here, we investigated the MET receptor as a potential molecular target in advanced cervical cancer. Downregulation of MET receptor expression via RNA interference in different cervical carcinoma cell lines dramatically decreased tumor growth and forced tumor differentiation in vivo. MET receptor silencing also led to a dramatic decrease in cell size and a decrease in proliferation rate under normal and stress conditions. MET receptor downregulation also resulted in decreased cyclin D1 and c-myc levels but did not increase apoptosis. Subsequent experiments showed that downregulation of the MET receptor decreased the expression of a key regulator of the epithelial-to-mesenchymal transition, SLUG. and increased the expression of E-cadherin, a hallmark of the epithelial phenotype. Moreover, MET downregulation impairs expression and signaling of CXCR4 receptor, responsible for invasive phenotype.Taken together, our results strongly suggest that the MET receptor influences the oncogenic properties of cervical carcinoma cells in vitro and in vivo. These findings highlight a unique role of the MET receptor in cervical carcinoma cells and indicate the MET receptor as a potential therapeutic target for advanced cervical carcinoma.  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