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   6000篇
  免费   182篇
  国内免费   27篇
耳鼻咽喉   134篇
儿科学   232篇
妇产科学   262篇
基础医学   795篇
口腔科学   67篇
临床医学   436篇
内科学   1477篇
皮肤病学   77篇
神经病学   491篇
特种医学   76篇
外科学   401篇
综合类   37篇
一般理论   1篇
预防医学   477篇
眼科学   191篇
药学   635篇
中国医学   11篇
肿瘤学   409篇
  2024年   15篇
  2023年   54篇
  2022年   159篇
  2021年   245篇
  2020年   106篇
  2019年   130篇
  2018年   141篇
  2017年   136篇
  2016年   158篇
  2015年   155篇
  2014年   222篇
  2013年   270篇
  2012年   442篇
  2011年   481篇
  2010年   260篇
  2009年   205篇
  2008年   341篇
  2007年   426篇
  2006年   404篇
  2005年   392篇
  2004年   400篇
  2003年   369篇
  2002年   330篇
  2001年   22篇
  2000年   18篇
  1999年   21篇
  1998年   32篇
  1997年   31篇
  1996年   20篇
  1995年   25篇
  1994年   10篇
  1993年   8篇
  1992年   13篇
  1991年   11篇
  1990年   6篇
  1989年   10篇
  1988年   7篇
  1987年   8篇
  1986年   7篇
  1985年   10篇
  1984年   11篇
  1983年   12篇
  1982年   12篇
  1981年   11篇
  1980年   7篇
  1978年   5篇
  1977年   6篇
  1975年   9篇
  1974年   8篇
  1966年   4篇
排序方式: 共有6209条查询结果,搜索用时 31 毫秒
1.
Patients with schizophrenia are predisposed toward developing cardiovascular disease. Although neuroleptics affect the cardiovascular system, it is also important to consider the consequences of the disease itself such as lower physical activity due to living on disability pension, inadequate nutrition, and/or nicotine addiction, being more common among patients with schizophrenia versus the general population. All these factors combined lead to an increased risk of death caused by cardiovascular conditions in schizophrenic patients. Individuals receiving typical antipsychotic drugs have been reported to have elevated concentrations of antiphospholipid antibodies, including anticoagulants and anticardiolipin antibodies. The presence of both antibodies is associated with an increased risk for thromboembolism. It is also likely that mental illness is accompanied by increased procoagulant activity. Patients with acute psychosis have been shown to have a statistically significant increase in the concentrations of D-dimer, P-selectin, and in the expression of platelet glycoprotein IIb/IIIa receptors. Learning about causes and mechanisms of venous thromboembolism could help to reduce or neutralize the adverse effects of antipsychotic treatment and facilitate the identification of appropriate markers necessary to monitor changes and provide preventive care against hazardous and potentially fatal complications such as deep venous thrombosis and pulmonary embolism. Before atypical neuroleptic treatment is administered to hospitalized patients, all possible risk factors for thromboembolism should be considered to allow the application of lower risk drugs. Also, other preventive measures should be taken into account, including hydration, compression stockings, regular exercise of lower extremities, and low-molecular-weight heparin injections.  相似文献   
2.
In the following respects, tooth enamel is a unique tissue in the mammalian body: (a) it is the most mineralized and hardest tissue in it comprising up to 95 wt% of apatite; (b) its microstructure is dominated by parallel rods composed of bundles of 40–60 nm wide apatite crystals with aspect ratios reaching up to 1:10,000 and (c) not only does the protein matrix that gives rise to enamel guides the crystal growth, but it also conducts its own degradation and removal in parallel. Hence, when mimicking the process of amelogenesis in vitro, crystal growth has to be coupled to proteolytic digestion of the amelogenin assemblies that are known to play a pivotal role in conducting the proper crystal growth. Experimental settings based on controlled and programmable titration of amelogenin sols digested by means of MMP-20 with buffered calcium and phosphate solutions were employed to imitate the formation of elongated, plate-shaped crystals. Whilst amelogenin can act as a promoter of nucleation and crystal growth alone, in this study we show that proteolysis exerts an additional nucleation- and growth-promoting effect. Hydrolysis of full-length amelogenin by MMP-20 decreases the critical time needed for the protein and peptides to adhere and to cover the substrate. The formation and immobilization of a protein layer subsequently reduces the time for calcium phosphate crystallization. Coupling the proteolytic reaction to titration in the presence of 0.4 mg/ml rH174 has been shown to have the same effect on the crystal growth promotion as quadrupling the concentration of rH174 to 1.6 mg/ml. Controlling the rate and the extent of the proteolytic cleavage can thus be used to control the nucleation and growth rates in a protein-guided crystallization system.  相似文献   
3.
Early inhaled corticosteroid treatment improves symptom control and pulmonary function in children with asthma; however, long-term safety data are limited in infants and young children. This study assessed the long-term safety of budesonide inhalation suspension (BIS) in young children with persistent asthma. To continue to provide BIS to children who needed it—prior to US Food and Drug Administration approval—children 8 years of age or younger with mild, moderate, or severe persistent asthma who previously completed a 52-week open-label study of BIS were enrolled in an additional multicenter, open-label study that was to be concluded upon BIS approval. Patients already receiving BIS continued their current regimens. Patients younger than 4 years and those 4 years of age or older not receiving BIS at baseline started with total daily doses of 0.5 and 1.0 mg, respectively. BIS doses were adjusted throughout the study based on individual response. Adverse events and changes in laboratory parameters, vital signs, and physical examination findings were assessed. Of 198 enrolled patients, 152 (76.8%), 68 (34.3%), and 31 (15.7%) completed 1, 2, and 3 years of BIS treatment (mean daily dose 0.62±0.32 mg), respectively. One hundred sixty-six (83.8%) patients experienced an adverse event, of which 8.6% were considered by the investigator to be drug related. Adverse events were those typically occurring in a pediatric asthma population, with respiratory infection (49.0%) and sinusitis (25.3%) occurring at the greatest incidence. Only 2 patients withdrew due to adverse events. Mean changes in laboratory test results and physical examination findings were not clinically important throughout the study. Long-term BIS treatment is well tolerated in young children with persistent asthma, with a safety profile similar to that of short-term administration.  相似文献   
4.
Organ transplantation is limited by access to suitable organs. Infant recipient waitlist mortality is increased due to the scarcity of size-matched organs. Neonatal organ donors have been proposed as an underutilized source of donor organs. However, the literature on the actual prevalence and outcome of neonatal organ donation and transplantation is fragmented and not well analyzed. This literature review aims to summarize the available literature on the potential of neonatal organ donation and to analyze published cases of neonatal organ transplantation. A systematic search of the Medline and Cochrane databases yielded 2964 articles, which were screened for eligibility. In total, 86 articles were considered eligible, of which 34 were included in the literature review: 8 articles describing the potential of neonatal organ donation programs, and 26 articles describing clinical transplantation. Current evidence suggests there is a large pool of potential neonatal organ donors. In contrast, the literature on neonatal organ donor utilization is sparse. However, case series of successful kidney, heart, liver, hepatocyte, and multivisceral transplantation using organs from neonatal donors are summarized. Although good posttransplant organ function was achieved, the use of neonatal organs is associated with increased risk of thrombosis in both kidney and liver transplantation. Neonatal organ donation is a promising alternative for expanding the current donor pool. Experience is limited, but reported patient and graft survival are acceptable and more research on the subject is warranted.  相似文献   
5.
The fibroblast growth factor 1 (FGF1) gene is expressed primarily in the kidney and may contribute to hypertension. However, the biologic mechanisms underlying the association between FGF1 and BP regulation remain unknown. We report that the major allele of FGF1 single nucleotide polymorphism rs152524 was associated in a dose-dependent manner with systolic BP (P=9.65×10−5) and diastolic BP (P=7.61×10−3) in a meta-analysis of 14,364 individuals and with renal expression of FGF1 mRNA in 126 human kidneys (P=9.0×10−3). Next-generation RNA sequencing revealed that upregulated renal expression of FGF1 or of each of the three FGF1 mRNA isoforms individually was associated with higher BP. FGF1-stratified coexpression analysis in two separate collections of human kidneys identified 126 FGF1 partner mRNAs, of which 71 and 63 showed at least nominal association with systolic and diastolic BP, respectively. Of those mRNAs, seven mRNAs in five genes (MME, PTPRO, REN, SLC12A3, and WNK1) had strong prior annotation to BP or hypertension. MME, which encodes an enzyme that degrades circulating natriuretic peptides, showed the strongest differential coexpression with FGF1 between hypertensive and normotensive kidneys. Furthermore, higher level of renal FGF1 expression was associated with lower circulating levels of atrial and brain natriuretic peptides. These findings indicate that FGF1 expression in the kidney is at least under partial genetic control and that renal expression of several FGF1 partner genes involved in the natriuretic peptide catabolism pathway, renin-angiotensin cascade, and sodium handling network may explain the association between FGF1 and BP.  相似文献   
6.

Objective

To assess the prevalence of pain in the musculoskeletal system and possible reasons for these complaints among early age children from Warsaw schools.

Material and methods

The study was conducted in 34 randomly selected primary schools in Warsaw in 2011. 2748 survey-questionnaires were given to parents or legal guardians by children. Of these, 1509 surveys were subject to a final analysis. The survey included 66 questions regarding, among other things, pain in the musculoskeletal system in children. Additionally, there were questions about possibly occurring diseases, any postural defects, significant obesity, as well as effects of these complaints on the child''s physical activity. Survey data regarded 6–7-year-old children.

Results

In the group of 1509 respondents, 242 children (16%) complained about pain in the musculoskeletal system. Pain was located most frequently in the knee joints, and more rarely in the spine and joints in the upper extremities. In the group of children who complained about pain, moderate physical activity was statistically significantly limited. According to parents, physicians did not diagnose any medical conditions in 106 children. Joint disease was diagnosed in 33 children. Postural defects were diagnosed in 589 children. In 123 children complaining about pain at least one postural defect was diagnosed. Such defects were diagnosed statistically significantly more rarely (p = 0.011) in 1234 children who did not complain about pain (460 children). Platypodia or other foot deformation was observed in 25% of these children, spinal curvature in 12%, abnormal knee joint position in 11% and uneven hip position in 2% children. Of note, 17% of all children were significantly overweight. In overweight children the prevalence of pain, especially in the knee joints and feet, was significantly higher.

Conclusions

This study aims to underline the problem of musculoskeletal pain in early-age children which limits their physical activity. Also the authors draw attention to the issue of postural defects in a large group of school children. This issue undoubtedly requires more attention and a plan how to create more effective methods of prevention.  相似文献   
7.
8.
9.
Penicillin-binding proteins (PBPs) in representatives of two Streptococcus pneumoniae clonal groups that are prevalent in Poland, Poland 23F-16 and Poland 6B-20, were investigated by PBP profile analysis, antibody reactivity pattern analysis, and DNA sequence analysis of the transpeptidase (TP) domain-encoding regions of the pbp2x, pbp2b, and pbp1a genes. The isolates differed in their MICs of beta-lactam antibiotics. The majority of the 6B isolates were intermediately susceptible to penicillin (penicillin MICs, 0.12 to 0.5 microg/ml), whereas all 23F isolates were penicillin resistant (MICs, >or=2 microg/ml). The 6B isolates investigated had the same sequence type (ST), determined by multilocus sequence typing, as the Poland 6B-20 reference strain (ST315), but in the 23F group, isolates with three distinct single-locus variants (SLVs) in the ddl gene (ST173, ST272, and ST1506) were included. None of the isolates showed an identical PBP profile after labeling with Bocillin FL and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and only one pair of 6B isolates and one pair of 23F isolates (ST173 and ST272) each contained an identical combination of PBP 2x, PBP 2b, and PBP 1a TP domains. Some 23F isolates contained PBP 3 with an apparently higher electrophoretic mobility, and this feature also did not correlate with their STs. The data document a highly variable pool of PBP genes as a result of multiple gene transfer and recombination events within and between different clonal groups.  相似文献   
10.
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