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   3761篇
  免费   419篇
  国内免费   45篇
耳鼻咽喉   29篇
儿科学   118篇
妇产科学   65篇
基础医学   457篇
口腔科学   55篇
临床医学   508篇
内科学   675篇
皮肤病学   73篇
神经病学   407篇
特种医学   222篇
外科学   484篇
综合类   117篇
一般理论   1篇
预防医学   369篇
眼科学   101篇
药学   324篇
中国医学   2篇
肿瘤学   218篇
  2022年   24篇
  2021年   46篇
  2020年   35篇
  2019年   55篇
  2018年   66篇
  2017年   41篇
  2016年   47篇
  2015年   63篇
  2014年   84篇
  2013年   105篇
  2012年   205篇
  2011年   204篇
  2010年   132篇
  2009年   95篇
  2008年   145篇
  2007年   178篇
  2006年   157篇
  2005年   145篇
  2004年   152篇
  2003年   135篇
  2002年   128篇
  2001年   142篇
  2000年   137篇
  1999年   139篇
  1998年   88篇
  1997年   70篇
  1996年   68篇
  1995年   53篇
  1994年   49篇
  1993年   52篇
  1992年   76篇
  1991年   73篇
  1990年   60篇
  1989年   79篇
  1988年   79篇
  1987年   93篇
  1986年   76篇
  1985年   69篇
  1984年   45篇
  1983年   44篇
  1982年   31篇
  1981年   32篇
  1980年   27篇
  1979年   31篇
  1978年   31篇
  1977年   30篇
  1976年   33篇
  1974年   23篇
  1973年   25篇
  1971年   31篇
排序方式: 共有4225条查询结果,搜索用时 15 毫秒
111.
112.
OBJECTIVE: To determine whether the relationship between smoking and disease severity in women with rheumatoid arthritis (RA) is associated with polymorphism at the glutathione S-transferase (GST) M1 locus. METHODS: Genotyping for GSTM1 was carried out using polymerase chain reaction methodology on 164 women with established RA. Smoking history was obtained on each patient. Radiographic damage was measured by the Larsen score, and functional outcome was assessed by the Health Assessment Questionnaire (HAQ). Data were analyzed by multiple regression analyses, with correction for age and disease duration. RESULTS: Ever having smoked was associated with a worse radiographic and functional outcome than was never having smoked. Both past and current smoking were associated with increased disease severity. Stratification by GSTM1 status revealed that polymorphism at this locus affected the relationship between smoking and disease outcome measures. Patients who lacked the GSTM1 gene and had ever smoked had significantly higher Larsen and HAQ scores than did those who lacked the gene and had never smoked. Radiographic outcome in these patients was worse than that in patients who had the GSTM1 gene and who had smoked. The associations were not affected by correction for socioeconomic status. Rheumatoid factor (RF) production was found to be associated with smoking in only the GSTM1-null patients. CONCLUSION: Our data suggest that disease outcome in female RA patients with a history of smoking is significantly worse than in those who have never smoked. Smoking was associated with the most severe disease in patients who carried the GSTM1-null polymorphism. This association may be due in part to a relationship between the GSTM1 polymorphism and RF production in smokers.  相似文献   
113.
The fate of the donor graft in allogeneic bone marrow transplantation, the presence of chimaerism and early relapse can be monitored by identification of the donor or recipient origin of haemopoietic cells in peripheral blood and bone marrow. We have done this by the use of highly informative locus-specific hypervariable DNA probes in two sex and blood group matched transplants. In four sex mismatched transplants the Y chromosome was identified by in situ hybridization using a biotinylated Y probe. Early engraftment by day 13 was detected in five of the six patients. Transient chimaerism occurred in half of the cases and was accompanied by the temporary appearance of the Philadelphia chromosome in one patient with chronic myeloid leukaemia without subsequent relapse. Persistence of the graft in the face of falling peripheral counts was documented in four of the six patients studied. The morphology as well as origin of the haemopoietic cells could be characterized by the Y probe analysis. In one patient, recipient lymphocytes were shown to co-exist with myeloid series of donor origin. We conclude that both techniques are highly specific, sensitive and can provide information within 24-48 h. Thus they are of value in guiding early therapeutic intervention in allogeneic transplantation.  相似文献   
114.
115.

Background

A suitable definition of primary care to capture the variety of prevailing international organisation and service-delivery models is lacking.

Aim

Evaluation of strength of primary care in Europe.

Design and setting

International comparative cross-sectional study performed in 2009–2010, involving 27 EU member states, plus Iceland, Norway, Switzerland, and Turkey.

Method

Outcome measures covered three dimensions of primary care structure: primary care governance, economic conditions of primary care, and primary care workforce development; and four dimensions of primary care service-delivery process: accessibility, comprehensiveness, continuity, and coordination of primary care. The primary care dimensions were operationalised by a total of 77 indicators for which data were collected in 31 countries. Data sources included national and international literature, governmental publications, statistical databases, and experts’ consultations.

Results

Countries with relatively strong primary care are Belgium, Denmark, Estonia, Finland, Lithuania, the Netherlands, Portugal, Slovenia, Spain, and the UK. Countries either have many primary care policies and regulations in place, combined with good financial coverage and resources, and adequate primary care workforce conditions, or have consistently only few of these primary care structures in place. There is no correlation between the access, continuity, coordination, and comprehensiveness of primary care of countries.

Conclusion

Variation is shown in the strength of primary care across Europe, indicating a discrepancy in the responsibility given to primary care in national and international policy initiatives and the needed investments in primary care to solve, for example, future shortages of workforce. Countries are consistent in their primary care focus on all important structure dimensions. Countries need to improve their primary care information infrastructure to facilitate primary care performance management.  相似文献   
116.
Musculoskeletal computer models allow us to quantitatively relate morphological features to biomechanical performance. In non-human apes, certain morphological features have long been linked to greater arm abduction potential and increased arm-raising performance, compared to humans. Here, we present the first musculoskeletal model of a western lowland gorilla shoulder to test some of these long-standing proposals. Estimates of moment arms and moments of the glenohumeral abductors (deltoid, supraspinatus and infraspinatus muscles) over arm abduction were conducted for the gorilla model and a previously published human shoulder model. Contrary to previous assumptions, we found that overall glenohumeral abduction potential is similar between Gorilla and Homo. However, gorillas differ by maintaining high abduction moment capacity with the arm raised above horizontal. This difference is linked to a disparity in soft tissue properties, indicating that scapular morphological features like a cranially oriented scapular spine and glenoid do not enhance the abductor function of the gorilla glenohumeral muscles. A functional enhancement due to differences in skeletal morphology was only demonstrated in the gorilla supraspinatus muscle. Contrary to earlier ideas linking a more obliquely oriented scapular spine to greater supraspinatus leverage, our results suggest that increased lateral projection of the greater tubercle of the humerus accounts for the greater biomechanical performance in Gorilla. This study enhances our understanding of the evolution of gorilla locomotion, as well as providing greater insight into the general interaction between anatomy, function and locomotor biomechanics.  相似文献   
117.
Aqueous‐phase free‐radical batch polymerizations of N‐vinylimidazole (NVI) and quaternized N‐vinylimidazole (QVI) are conducted with varying initial monomer and initiator concentrations at 70 and 85 °C. The polymerization rate of NVI is very slow at the natural pH of 9 due to degradative radical addition to monomer. The rates are increased by lowering the pH, wherein the degradative addition to NVI monomer is partially (at pH 4) and completely (at pH 1) hindered, with the polymerization rate matching that of QVI at pH 1. The initial rates of polymerization for both NVI and QVI are independent of temperature. A kinetic model developed in Predici that includes the pH‐dependent side reactions can reasonably represent both QVI and NVI polymerization.

  相似文献   

118.
119.
Aims. To examine the association between recipient-sharing of needles and syringes and demographic characteristics, injecting behaviour and needle and syringe exchange utilisation . Design. Self-report data from serial cross-sectional surveys. Setting. Multiple street, needle and syringe exchange and drug treatment sites throughout Glasgow. Participants. 2576 current injecting drug users (IDUs) recruited during 1990–94. Findings. In the multiple logistic regression analysis, a significantly lower level of recipientsharing was associated with respondents who resided within 1 mile of a needle and syringe exchange compared to those who lived further away (adjusted OR 1.3; 95% CI 1.0–1.6), and by IDUs who reported obtaining either 6–15, 16–30, or > 30 sterile needles and syringes in an average week from a needle exchange and/or pharmacist (adjusted ORs 0.55, 0.34, 0.25; 95% CIs 0.3–0.9, 0.2–0.6 and 0.2–0.4, respectively) compared to those who obtained no sterile equipment from these sources. Recipient-sharing of needles and syringes in the previous 6 months reduced significantly between 1990 (43%) and 1991–94 (27–33%) (p < 0.0001); this decline was not explained by needle and syringe exchange utilization, suggesting that additional factors were influencing behavioural change at that time. Conclusion. Our data indicate that improving injectors' convenience of access to exchange facilities and increasing the numbers of sterile needles and syringes available to them is likely to result in further reductions in recipient-sharing, and thus the potential for blood-borne virus transmission, among IDUs.  相似文献   
120.
OBJECTIVE: To determine if antibodies to cyclic citrullinated peptide (anti-CCP) are found in chronic hepatitis C virus (HCV) infection. METHODS: Rheumatoid factor (RF) and anti-CCP were measured in sera from 50 patients with HCV infection but without cryoglobulinemia, sera from 29 patients with mixed cryoglobulinemia (including 13 with rheumatic symptoms and 5 with arthritis), and sera from 20 normal blood donors. Anti-CCP was measured by second-generation enzyme-linked immunosorbent assay (ELISA). RESULTS: No sera with elevated anti-CCP were found in patients with HCV infection without cryoglobulinemia, and in that population, the maximum anti-CCP was 10 units, well below the positive cutoff of 20 units. Positive findings on RF testing >13 IU/ml were present in 22 (44%) of the HCV patients, with RF >50 IU/ml in 8 (16%) and a maximum RF of 526 IU/ml. Of the cryoglobulinemia patients, 22 (76%) had positive results on tests for RF, including 18 (62%) with RF >50 IU/ml and a maximum RF of 5,540 IU/ml. Two (6.9%) of the cryoglobulinemia patients had borderline-positive findings on tests for anti-CCP (25 units and 37 units), which were false-positive results caused by nonspecific binding in the ELISA. No association between the RF and the anti-CCP concentrations was found. CONCLUSION: Whereas RF was frequent in patients with HCV infection with and without cryoglobulinemia, anti-CCP was not observed in patients with uncomplicated HCV infection. Borderline-positive anti-CCP results were observed infrequently in patients with mixed cryoglobulinemia and were caused by nonspecific binding to plastic. Measurement of anti-CCP may help in diagnosing RA in patients with chronic HCV infection.  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