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   10944篇
  免费   698篇
  国内免费   46篇
耳鼻咽喉   107篇
儿科学   382篇
妇产科学   327篇
基础医学   1212篇
口腔科学   355篇
临床医学   768篇
内科学   2465篇
皮肤病学   225篇
神经病学   603篇
特种医学   374篇
外科学   1421篇
综合类   198篇
一般理论   5篇
预防医学   665篇
眼科学   515篇
药学   1002篇
中国医学   51篇
肿瘤学   1013篇
  2023年   59篇
  2022年   134篇
  2021年   275篇
  2020年   143篇
  2019年   207篇
  2018年   269篇
  2017年   171篇
  2016年   216篇
  2015年   276篇
  2014年   361篇
  2013年   453篇
  2012年   684篇
  2011年   707篇
  2010年   355篇
  2009年   350篇
  2008年   499篇
  2007年   540篇
  2006年   542篇
  2005年   495篇
  2004年   469篇
  2003年   425篇
  2002年   395篇
  2001年   317篇
  2000年   320篇
  1999年   237篇
  1998年   108篇
  1997年   72篇
  1996年   69篇
  1995年   69篇
  1992年   163篇
  1991年   166篇
  1990年   161篇
  1989年   143篇
  1988年   139篇
  1987年   170篇
  1986年   144篇
  1985年   115篇
  1984年   118篇
  1983年   90篇
  1982年   58篇
  1980年   53篇
  1979年   73篇
  1977年   64篇
  1976年   65篇
  1975年   65篇
  1974年   85篇
  1973年   75篇
  1972年   58篇
  1971年   60篇
  1970年   50篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In the presence of infection, neutropenia is considered to be a marker of poor prognosis; conversely, neutrophilia may not be a determinant of a better prognosis. Since apoptotic neutrophils are compromised functionally, we evaluated the effect of infection on neutrophil apoptosis. The rate of apoptosis was greater for neutrophils isolated from patients with infection than for healthy controls. Escherichia coli did not directly modulate the rate of neutrophil apoptosis. However, sera from infected patients promoted (P < 0.001) neutrophil apoptosis. Interestingly, the sera of patients with different types of infection (gram negative, gram positive, or culture negative) exerted a more or less identical response on neutrophil apoptosis. Sera of infected patients showed a fivefold greater content of FasL compared to controls. Moreover, anti-FasL antibody partly attenuated the infected-serum-induced neutrophil apoptosis. In in vitro studies, E. coli enhanced monocyte FasL expression. Moreover, conditioned media prepared from activated macrophages from control mice showed enhanced apoptosis of human as well as mouse neutrophils. On the contrary, conditioned media prepared from activated macrophages isolated from FasL-deficient mice induced only a mild degree of neutrophil apoptosis. These results suggest that neutrophils in patients with infection undergo apoptosis at an accelerated rate. Infection not only promoted monocyte expression of FasL but also increased FasL content of the serum. Because the functional status of apoptotic cells is compromised, a significant number of neutrophils may not be participating in the body's defense. Since neutrophils play the most important role in innate immunity, their compromised status in the presence of infection may transfer the host defense burden from an innate response to acquired immunity. The present study provides some insight into the lack of correlation between neutrophilia and the outcome of infection.  相似文献   
92.
Kidney aging has been recognized as a chronic process of compromised renal function and structural changes in the tubulointerstitium and glomerulus. Cell senescence is associated with alterations in cell structure and function, including expression of cytokines and structural and regulatory components of extracellular matrix proteins. In this investigation, we tested the hypothesis that senescent renal cells may accumulate in vivo with advancing age. We also evaluated the expression of transforming growth factor (TGF)-beta1 and p21WAF1/CIP1 in aging kidneys. Sprague-Dawley rats at the ages of 3, 12, and 24 months were used for this study. Renal tissues were processed for morphometric and senescence analysis. Expression of TGF-beta1 and p21WAF1/CIP1 was evaluated by Northern or Western blot analysis and immunohistochemistry. Substantial tubulointerstitial injury occurred at the age of 12 months, but significant glomerular structure alteration was observed at the age of 24 months. Tubular cells developed senescence, which was detected by beta-galactosidase staining. This staining increased in frequency and intensity with age. Renal cortices showed a significant increase in the mRNA expression for TGF-beta1 and protein level for p21WAF1/CIP1. The enhanced expression of TGF-beta1 and p21WAF1/CIP1 was localized in the tubulointersititial cells. These data suggest that tubular cells undergo senescence and express increased TGF-beta1 and p21WAF1/CIP1 with advancing age. These age-related cellular and molecular alterations may play an important role in the initiation and/or progression of tubulointerstitial fibrosis and glomerulosclerosis in aging.  相似文献   
93.
The Xenopus oocyte nucleus (GV) is a storehouse for a large number of proteins that are used during early development. We have cloned and characterized a cDNA coding for a maternal gene product that is localized in the GV and then becomes highly enriched in the nuclei of the central nervous system (CNS) of tadpoles and adult frogs. This cDNA (xlgv7) is 2.1 kb and hybridizes to a 2.4-kb RNA species on Northern blots. Southern blots of genomic DNA suggest that this gene is a member of a multigene family. The cDNA sequence reveals a long open reading frame (ORF) of 1773 nucleotides, with a putative nuclear targeting signal (Glu Arg Arg Lys Lys Lys Thr) at the extreme carboxyl terminus and an internal histidine (His)-rich region with a repeated conserved amino acid sequence between His pairs. The significance of this region is unclear, but the protein is a DNA-binding protein, and it is possible that this region is involved in this function. The xlgv7 protein also possesses a putative nucleotide-binding consensus sequence that is similar to the bacterial RecA and RecB and yeast RAD proteins. Protein xlgv7 exists as several isotypes that exhibit developmental and cell-specific changes during development. Northern blot analysis of the abundance of the xlgv7 mRNA shows an accumulation following neural induction at stages 15-16. There is a transient expression of the mRNA in the gut of tadpoles. In the adult, the mRNA is highly enriched in the brain and is absent or in very low abundance in other tissues. Immunohistochemical analysis of the protein shows that the protein is localized in the nuclei of the brain cells. We conclude that the xlgv7 gene product is a maternal protein that may serve several important functions, one of which may be in the development and maintanance of the CNS.  相似文献   
94.
Intracellular potentials of cells from isolated segments of microperfused human sweat ducts were measured in order to determine the electrical profiles of these cells under resting, transporting, and inhibited conditions. Even though the cells are relatively small (ca. 6–8 m), continuous recordings of intracellular potentials from the same impalement were stable for up to 2 h. In the resting condition in normal Ringer's solution when the lumen of the duct was collapsed and not perfused, the intracellular potential measured across the basal membrane was 34.6±1.5 mV (n=31; mean±SE). In the same bathing medium, when the duct lumen was also perfused with normal Ringer's solution, the basolateral membrane potential (V b), the apical membrane potential (V a) and transepithelial potential (V t) was –33.8±0.47 mV, –23.7±0.48 mV and –9.6±0.9 mV (n=73), respectively. The average input impedence (R i) of these cells was 19.6±0.4 M (n=36). The frequency distribution ofV b was unimodal suggesting that only one functional cell type exists in this tissue. Amiloride (0.1 mM) in the lumen hyperpolarized bothV a andV b by –40.5±3.6 mV and –33.2±3.7 mV (n=15), respectively, with a slight but significant increase inR i (15%), while abolishingV t. Removing luminal Cl depolarizedV a by +37.0±4.2 mV and hyperpolarizedV b by –19.0±4.2 mV (n=11). Removing Cl from the bath hyperpolarizedV a by –3.3±2.3 mV and depolarizedV b by +24.3±2.7 mV (n=15). Ouabain caused an initial fast depolarization (+8 mV) followed by a prolonged slow depolarization ofV b, and an increase inR i of about 84%. These results not only provide the first electrical profile of the human sweat duct tissue, but they also show that its cell membrane potentials are unusually low. This unusual property of this epithelium appears to be due to the combination of a significant Na+ conductance at the apical membrane and a remarkably high tissue Cl conductance.  相似文献   
95.
From 1975 to 1982, 205 patients with local prostate cancer were treated at the radiation oncology department, the University of Kansas Medical Center, Kansas City, Kansas. Patients'' median age was 73 years. All of the patients were staged according to American Urologic staging criteria. Twenty-eight patients had stage A2 cancer, 91 patients had stage B cancer, and 86 patients had stage C cancer. All patients were treated using megavoltage radiation (dosage range: 6000 cGy to 7100 cGy). The follow-up period ranged from a minimum of 8 years to a maximum of 15 years (median: 9.4 years). The clinical local control was 96% for stage A2, 94% for stage B, and 90% for stage C disease. The overall and disease-free survival rates were 71% and 60%, respectively. Fourteen patients developed moderate complications with one patient (0.5%) requiring surgical intervention. The local control and survival rates reported in this study are comparable with surgical results, suggesting that external beam irradiation in prostate cancer is safe and effective.  相似文献   
96.
One-stage surgery was successfully performed in a 44-year-old hypertensive man with uncontrolled angina, multiple coarctations of the thoracic and abdominal aorta, and a previous subtotal gastrectomy. There was a gradient of 120 mm Hg between the thoracic and abdominal aorta. A graft was placed retroperitoneally from the infrarenal aorta to the ascending aorta and was followed by a coronary artery bypass graft. Twenty-four months postoperatively, the patient was free of angina, and his hypertension was easily controlled.  相似文献   
97.
Aim

The primary objective of this study was to investigate temporal changes in HIV testing rates and quantify the degree to which these trends can be attributed to certain socio-economic characteristics, as well as exposure to information sources.

Subjects and methods

Data from a nationally representative sample of 30,020 sexually active black Africans who participated in the first, second, third and fourth South African National HIV, Behaviour and Health Surveys conducted in 2002, 2005, 2008 and 2012, respectively. Multivariable logistic regression models and population-attributable risks were calculated for the socio-economic characteristics and the information sources.

Results

The socio-economic characteristics of the survey participants remained stable over time, while HIV testing rates increased substantially from 20% in 2002 to 70% in 2012. However, there was little improvement in condom use rates. Combined impact of education, employment and geographical locations were associated with increased levels of HIV testing rates. Most of the survey participants (> 80%) were exposed to several mass-media and interpersonal information sources. The combined impact of mass-media tools on HIV testing rates ranged between 48 and 60%, while 40–50% of the HIV tests were collectively attributed to the interpersonal information sources.

Conclusion

We observed significant temporal changes in population-level impacts of several key socio-economic characteristics and information sources on HIV testing rates. Widespread nationwide HIV awareness efforts led to significant increases in access to testing facilities and substantial increases in HIV testing rates over time. However, this increase was not mirrored in condom use behaviour.

  相似文献   
98.
Maternal and Child Health Journal - The Maternal and Child Health (MCH) Pipeline Training Program, promotes development of a diverse health workforce by training undergraduate students from...  相似文献   
99.
Provision of safe drinking water in the United States is a great public health achievement. However, new waterborne disease challenges have emerged (e.g., aging infrastructure, chlorine-tolerant and biofilm-related pathogens, increased recreational water use). Comprehensive estimates of the health burden for all water exposure routes (ingestion, contact, inhalation) and sources (drinking, recreational, environmental) are needed. We estimated total illnesses, emergency department (ED) visits, hospitalizations, deaths, and direct healthcare costs for 17 waterborne infectious diseases. About 7.15 million waterborne illnesses occur annually (95% credible interval [CrI] 3.88 million–12.0 million), results in 601,000 ED visits (95% CrI 364,000–866,000), 118,000 hospitalizations (95% CrI 86,800–150,000), and 6,630 deaths (95% CrI 4,520–8,870) and incurring US $3.33 billion (95% CrI 1.37 billion–8.77 billion) in direct healthcare costs. Otitis externa and norovirus infection were the most common illnesses. Most hospitalizations and deaths were caused by biofilm-associated pathogens (nontuberculous mycobacteria, Pseudomonas, Legionella), costing US $2.39 billion annually.  相似文献   
100.
PurposeTo report outcomes of Debridement, Antibiotic therapy and Implant Retention (DAIR) for periprosthetic knee joint infections (PJI) in the Indian population and to study factors influencing outcomes.MethodsThis was a Retrospective study of 80 cases of acute PJI after total knee arthroplasty who were treated by DAIR, within 2 weeks of onset of infection. A standardised institutional management protocol was applied to all cases. Patients were followed up for a minimum 1 year. Outcomes of DAIR were classified as successful or unsuccessful based on resolution or persistence of infection, and subsequent requirement of revision surgery. Influence of factors, like comorbidities, culture status and microbiological characteristics of causative organism, on outcomes was assessed.ResultsOverall 55 patients (68.75%) had successful eradication of infection after DAIR. 27 (33.7%) patients were culture negative and 53 (66.2%) patients grew organisms on culture. There was no statistically significant difference in outcomes (p = 0.082) between culture-positive cases (69.8% success rate) and (66.7% success rate) in culture negative cases. Furthermore, no difference in outcomes was observed in culture-positive patients between those who grew Gram-positive organisms versus Gram-negative organisms (p = 0.398) Similarly, patient comorbidities did not significantly alter the outcomes after DAIR (p = 0.732).ConclusionOur study demonstrates that early DAIR within 2 weeks of onset of infection using a standard protocol during surgery and postoperatively can result in good outcomes. Patient comorbidities, culture status (positive versus negative), Gram staining characteristics of organisms and the identity of pathogenic bacteria did not influence outcomes of DAIR for acute PJI.  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