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   4010篇
  免费   325篇
  国内免费   10篇
耳鼻咽喉   20篇
儿科学   82篇
妇产科学   72篇
基础医学   469篇
口腔科学   91篇
临床医学   711篇
内科学   676篇
皮肤病学   43篇
神经病学   378篇
特种医学   62篇
外科学   503篇
综合类   56篇
一般理论   7篇
预防医学   520篇
眼科学   37篇
药学   357篇
中国医学   2篇
肿瘤学   259篇
  2024年   7篇
  2023年   37篇
  2022年   41篇
  2021年   106篇
  2020年   78篇
  2019年   101篇
  2018年   118篇
  2017年   86篇
  2016年   85篇
  2015年   92篇
  2014年   119篇
  2013年   183篇
  2012年   321篇
  2011年   302篇
  2010年   178篇
  2009年   150篇
  2008年   308篇
  2007年   276篇
  2006年   293篇
  2005年   271篇
  2004年   228篇
  2003年   193篇
  2002年   166篇
  2001年   47篇
  2000年   45篇
  1999年   49篇
  1998年   40篇
  1997年   33篇
  1996年   27篇
  1995年   16篇
  1994年   17篇
  1993年   14篇
  1992年   23篇
  1991年   27篇
  1990年   22篇
  1989年   22篇
  1988年   32篇
  1987年   13篇
  1986年   18篇
  1985年   18篇
  1984年   9篇
  1983年   12篇
  1982年   7篇
  1981年   12篇
  1980年   7篇
  1979年   11篇
  1978年   15篇
  1975年   12篇
  1974年   13篇
  1972年   7篇
排序方式: 共有4345条查询结果,搜索用时 15 毫秒
101.
While forced labor in the world’s fishing fleet has been widely documented, its extent remains unknown. No methods previously existed for remotely identifying individual fishing vessels potentially engaged in these abuses on a global scale. By combining expertise from human rights practitioners and satellite vessel monitoring data, we show that vessels reported to use forced labor behave in systematically different ways from other vessels. We exploit this insight by using machine learning to identify high-risk vessels from among 16,000 industrial longliner, squid jigger, and trawler fishing vessels. Our model reveals that between 14% and 26% of vessels were high-risk, and also reveals patterns of where these vessels fished and which ports they visited. Between 57,000 and 100,000 individuals worked on these vessels, many of whom may have been forced labor victims. This information provides unprecedented opportunities for novel interventions to combat this humanitarian tragedy. More broadly, this research demonstrates a proof of concept for using remote sensing to detect forced labor abuses.

Forced labor in fisheries, a type of modern slavery, is increasingly recognized as a human rights crisis. The International Labor Organization (ILO) defines forced labor as “all work or service which is exacted from any person under the menace of any penalty and for which the said person has not offered himself voluntarily” (1). The ILO provides a framework of 11 forced labor risk indicators (2) that have all been documented within the fisheries sector, including indicators representative of debt-bonded labor, as well as indicators representative of servitude or slave labor such as abusive working and living conditions. In 2015, reports emerged on forced labor in Thai fisheries (3) and the role of forced labor in producing seafood imported to the United States (4). More recent reports have described the global nature of the problem (5), and there has been a call to integrate social responsibility into ocean science (6). Despite widespread condemnation and ambitious commitments, forced labor remains poorly understood in the fisheries sector. Here we show that recently available high-frequency vessel monitoring of the global industrial fishing fleet can shed new light on forced labor at a much finer resolution. We combine expertise from on-the-ground human rights practitioners and satellite vessel monitoring data for over 16,000 industrial fishing vessels to estimate 1) the number of high-risk vessels and the number of crew who may be victims working on those vessels, 2) where these vessels fish, and 3) what ports these vessels visit. This information can inform new market, policy, and enforcement interventions to combat forced labor in global fisheries. This research more generally demonstrates how remote sensing can detect forced labor abuses by observing dynamic behavior.Current estimates of forced labor in fisheries are coarse and are based on country-level statistics. Using country-level household surveys, the ILO estimated that 16 million people were victims of forced labor in 2016, with 11% of these in agriculture, forestry, or fisheries (7). The Global Slavery Index reports that the seven countries with highest slavery risk in 2018 generated 39% of global fisheries catch (3, 8), and Tickler et al. found that the United States has slavery risks of 0.2 kg per metric ton for domestic seafood and 3.1 kg per metric ton for imported seafood (9). While these studies are important for broadly understanding which countries have risk, current methods are unable to detect this problem at the level of individual fishing vessels, which will be essential for targeted interventions.We empirically examine whether vessels reported to exhibit any of the ILO indicators of forced labor behave in ways that are systematically different from other vessels, and then exploit this information using machine learning to discriminate between vessels that use forced labor from those that do not. We do so by measuring a suite of features that can be observed using satellite Automatic Identification System (AIS) vessel monitoring data made available by Global Fishing Watch (GFW) (10). There may be many behavioral correlates with forced labor that could help to differentiate between high-risk and low-risk vessels. To determine which model features to include, we first conducted a literature review of investigative journalism reports and looked for instances of forced labor case accounts that detailed specific behaviors that could be observed using vessel monitoring data. We next conducted informal phone interviews with experts from several nongovernmental organizations (NGOs) working in this field, during which we asked interviewees what observable vessel behaviors they would look for if they wanted to identify suspicious activity. The machine-learning approach we use does not assume that vessels behave in any particular way; rather, it merely uses the features identified by literature review and expert insight to exploit any observed empirical differences between vessels that use forced labor and other vessels. NGO experts and investigative journalism suggest that gaps in AIS transmission, port avoidance, transshipment, and extended time at sea may indicate the presence of forced labor (11). Certain features, like information on catch and the species being targeted, could also be helpful in discriminating between high- and low-risk behavior by providing more context on the fishing taking place. However, these data are not currently available at the vessel level on a global scale. Data on recruitment practices and vessel ownership and information on from where the crew originates could also be helpful, but, again, these data are not widely available. We arrived at a list of 27 vessel behavior and characteristic features for which we have globally available data at the vessel level (SI Appendix, Table S1, and SI Appendix).To build a predictive model for identifying high-risk vessels, we developed a training dataset that includes the behavior and characteristics of known forced-labor vessels, as well as the behavior and characteristics of other vessels. We compiled a comprehensive database of vessels that were reported to display one or more of the ILO forced labor indicators (2); these vessels are labeled as “positives.” We do not, however, know which vessels do not use forced labor (“negatives”). Rather, any vessel that we do not label as positive is “unlabeled,” and may in fact be a positive vessel that has not yet been identified or may truly be a negative vessel. This is an example of “positive-unlabeled (PU)” learning, a less straightforward problem than traditional supervised machine learning (12). We use PU learning to predict whether or not 16,261 longliner, trawler, and squid jigger fishing vessels were high-risk during each year they operated between 2012 and 2018 (“vessel-years”). We focus on this subset of vessels because they broadcasted sufficient and reliable AIS positions and because these are the only fishing gear types with documented cases of forced labor aboard vessels that broadcasted sufficient AIS data. These vessels represent 33% of the total time at sea spent by all fishing vessels operating in this time period tracked by GFW. Our PU approach leverages information from all positively labeled vessels (n = 22 unique vessels across 22 vessel-years using our baseline model assumption), but places less emphasis on unlabeled vessels given their uncertain nature (n = 16,257 unique vessels across 66,314 vessel-years using our baseline model assumption).  相似文献   
102.
Purpose  The study investigated the impact of prior abdominal surgery on conversions and outcomes of laparoscopic right colectomy. Methods  A consecutive series of 414 patients with cancer or adenomas who underwent a laparoscopic right colectomy from March 1996 to November 2006 were studied for surgical conversions and outcomes. Conversion was defined as an incision length > 7 cm. Results  Patients with prior abdominal surgery (n = 191) were compared with patients with no prior abdominal surgery (n = 223), and showed no significant differences in age, ASA classification, length of stay, operative time, blood loss, harvested nodes, tumor size, and specimen length. Significantly more wound infections occurred in the prior abdominal surgery group (22 vs.12, P = 0.023). Body mass index > 30 showed a three-fold increased risk of conversion. Fifteen percent of the no prior abdominal surgery patients and 17 percent of the prior abdominal surgery patients were converted (P > 0.05). Conversion was associated with a longer mean length of stay (8.8 days) relative to laparoscopically completed cases (6.3 days) regardless of prior abdominal surgery history (P < 0.0001). Conclusions  Laparoscopic right colectomy for neoplasia was not associated with a higher conversion rate or morbidity in patients with prior abdominal surgery. Prior abdominal surgery is not a contraindication to laparoscopic right colectomy. Presented at the 15th International Congress of the European Association of Endoscopic Surgery, Athens, Greece, July 4 to 7, 2007.  相似文献   
103.
104.
105.
Purpose: To appraise the application of accepted good practice guidance on public involvement in assistive technology research and to identify its impact on the research team, the public, device and trial design. Methods: Critical reflection and within-project evaluation were undertaken in a case study of the development of a functional electrical stimulation device. Individual and group interviews were undertaken with lay members of a 10 strong study user advisory group and also research team members. Results: Public involvement was seen positively by research team members, who reported a positive impact on device and study designs. The public identified positive impact on confidence, skills, self-esteem, enjoyment, contribution to improving the care of others and opportunities for further involvement in research. A negative impact concerned the challenge of engaging the public in dissemination after the study end. Conclusions: The public were able to impact significantly on the design of an assistive technology device which was made more fit for purpose. Research team attitudes to public involvement were more positive after having witnessed its potential first hand. Within-project evaluation underpins this case study which presents a much needed detailed account of public involvement in assistive technology design research to add to the existing weak evidence base.
  • Implications for Rehabilitation
  • The evidence base for impact of public involvement in rehabilitation technology design is in need of development.

  • Public involvement in co-design of rehabilitation devices can lead to technologies that are fit for purpose.

  • Rehabilitation researchers need to consider the merits of active public involvement in research.

  相似文献   
106.
107.

Objective:

To systematically review and assess the effectiveness and safety of antidepressants for neuropathic pain among individuals with spinal cord injury (SCI).

Methods:

A systematic search was conducted using multiple databases for relevant articles published from 1980 to April 2014. Randomized controlled trials (RCTs) involving antidepressant treatment of neuropathic pain with ≥3 individuals and ≥50% of study population with SCI were included. Two independent reviewers selected studies based on inclusion criteria and then extracted data. Pooled analysis using Cohen’s d to calculate standardized mean difference, standard error, and 95% confidence interval for primary (pain) and other secondary outcomes was conducted.

Results:

Four RCTs met inclusion criteria. Of these, 2 studies assessed amitriptyline, 1 trazadone, and 1 duloxetine among individuals with neuropathic SCI pain. A small effect was seen in the effectiveness of antidepressants in decreasing pain among individuals with SCI (standardized mean difference = 0.34 ± 0.15; 95% CI, 0.05-0.62; P = .02). A number needed to treat of 3.4 for 30% or more pain relief was found by pooling 2 studies. Of these, significantly higher risk of experiencing constipation (risk ratio [RR] = 1.74; 95% CI, 1.09-2.78; P = .02) and dry mouth (RR = 1.39; 95% CI, 1.04-1.85; P = .02) was found amongst individuals receiving antidepressant treatment compared to those in the control group.

Conclusion:

The current meta-analysis demonstrates that antidepressants are effective in reducing neuropathic SCI pain. However, this should be interpreted with caution due to the limited number of studies. Further evaluation of long-term therapeutic options may be required.  相似文献   
108.
Fibrillary glomerulonephritis is a rare cause of glomerulonephritis characterized by non‐amyloid fibrillary deposits of unknown aetiology. It is generally considered idiopathic but may be associated with secondary causes such as monoclonal gammopathy, hepatitis B and C infections, autoimmune diseases and malignancies. We report two Australian families with apparent familial fibrillary glomerulonephritis inherited in an autosomal dominant pattern, and postulate the existence of a primary familial entity. Family 1 consists of an affected father and daughter; the daughter progressed to end‐stage renal failure within 18 months of diagnosis, despite immunosuppressive therapy. The father, however, remains stable at 10 months follow up. Family 2 comprises an affected mother and son; the mother commenced haemodialysis 5 years after diagnosis and subsequently underwent successful renal transplantation. The son is presently stable at last follow‐up after 5 years. A further review of the second family history reveals a third family member (maternal father) dying of ‘Bright's disease’. We describe their histopathology, clinical progression and treatment outcomes, and provide a review of the current understanding of this heterogeneous condition that is associated with poor renal outcomes.  相似文献   
109.
110.

Background

At laparoscopic cholecystectomy, most surgeons have adopted the operative approach where the ‘critical view of safety’ (CVS) is achieved prior to dividing the cystic duct and artery. This prospective study evaluated whether an adequate critical view was achieved by scoring standardized intra-operative photographic views and whether there were other factors that might impact on the ability to obtain an adequate critical view.

Methods

One hundred consecutive patients undergoing a laparoscopic cholecystectomy were studied. At each operation, two photographs were taken. Two independent experienced hepatobiliary surgeons scored the photographs on whether a critical view of safety was achieved. Inter-observer agreement was calculated using the weighted kappa coefficient. The Cochran–Mantel–Haenszel test was used to analyse the scores with potential confounding clinical factors.

Results

The kappa coefficient for adequate display of the cystic duct and artery was 0.49; 95% confidence interval (CI) 0.33 to 0.64; P = 0.001. No bias was detected in the overall scorings between the two observers (χ2 1.33; P = 0.312). Other clinical factors including surgeon seniority did not alter the outcome [odds ratio (OR) 0.902; 95% confidence interval 0.622 to 1.264].

Conclusion

Heightened awareness of the CVS through mandatory documentation may improve both trainee and surgeon technique.  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