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   1613384篇
  免费   94695篇
  国内免费   1824篇
耳鼻咽喉   21596篇
儿科学   51276篇
妇产科学   40802篇
基础医学   241456篇
口腔科学   40733篇
临床医学   142604篇
内科学   302265篇
皮肤病学   34758篇
神经病学   119187篇
特种医学   63945篇
外国民族医学   254篇
外科学   245237篇
综合类   28746篇
现状与发展   3篇
一般理论   360篇
预防医学   116187篇
眼科学   35857篇
药学   125092篇
  8篇
中国医学   3686篇
肿瘤学   95851篇
  2018年   25778篇
  2017年   20291篇
  2016年   23787篇
  2015年   15992篇
  2014年   21458篇
  2013年   31313篇
  2012年   46503篇
  2011年   55604篇
  2010年   34309篇
  2009年   30598篇
  2008年   52410篇
  2007年   58208篇
  2006年   47352篇
  2005年   46638篇
  2004年   45525篇
  2003年   45069篇
  2002年   42462篇
  2001年   78494篇
  2000年   80586篇
  1999年   66649篇
  1998年   17046篇
  1997年   14896篇
  1996年   14820篇
  1995年   13903篇
  1994年   12578篇
  1993年   12053篇
  1992年   49934篇
  1991年   49592篇
  1990年   49213篇
  1989年   47588篇
  1988年   43128篇
  1987年   42183篇
  1986年   39472篇
  1985年   37379篇
  1984年   27237篇
  1983年   23105篇
  1982年   12484篇
  1979年   24897篇
  1978年   17008篇
  1977年   14724篇
  1976年   13676篇
  1975年   15878篇
  1974年   18230篇
  1973年   17629篇
  1972年   16631篇
  1971年   15752篇
  1970年   14587篇
  1969年   13929篇
  1968年   12598篇
  1967年   11282篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods.  相似文献   
102.
Digestive Diseases and Sciences - To determine whether the presence of portal vein thrombosis (PVT) where venous flow within the liver may be altered may delay the diagnosis of HCC and be...  相似文献   
103.

Background and aims

It is not known whether non alcoholic fatty liver disease (NAFLD) is a risk factor for diabetes in non obese, non centrally-obese subjects. Our aim was to investigate relationships between fatty liver, insulin resistance and a biomarker score for liver fibrosis with incident diabetes at follow up, in subjects who were neither obese nor centrally-obese.

Methods and results

As many as 70,303 subjects with a body mass index (BMI) < 25 kg/m2 and without diabetes were followed up for a maximum of 7.9 years. At baseline, fatty liver was identified by liver ultrasound, insulin resistance (IR) by homeostatic model assessment of insulin resistance (HOMA-IR) ≥2.0, and central obesity by waist circumference (waist circumference ≥90 cm (men) and ≥85 cm (women). The Fibrosis-4 (FIB-4 score) was used to estimate extent of liver fibrosis. Cox proportional hazards models adjusted for confounders were used to estimate hazard ratios (aHRs) for incident diabetes. As many as 852 incident cases of diabetes occurred during follow up (median [IQR] 3.71 [2.03] years). Mean ± SD BMI was 22.8 ± 1.8 and 21.7 ± 2.0 kg/m2 in subjects with and without diabetes at follow up. In subjects without central obesity and with fatty liver, aHRs (95% CI) for incident diabetes at follow up were 2.17 (1.56, 3.03) for men, and 2.86 (1.50,5.46) for women. Similar aHRs for incident diabetes occurred with fatty liver, IR and the highest quartile of FIB-4 combined, in men; and there was a non significant trend toward increased risk in women.

Conclusions

In normal weight, non-centrally obese subjects NAFLD is an independent risk factor for incident diabetes.  相似文献   
104.
Pharmaceutical Chemistry Journal - N-Substituted 4-aryl-2-hydroxy-4-oxobut-2-enoic acid hydrazides and their complexes with Ni(II), Mn(II), Co(II), Cu(II), and Zn(II) were prepared. Their...  相似文献   
105.
106.
Parhiala  P.  Ranta  K.  Gergov  V.  Kontunen  J.  Law  R.  La Greca  A. M.  Torppa  M.  Marttunen  M. 《School mental health》2020,12(2):265-283

In order to offer early and accessible treatment for adolescents with depression, brief and effective treatments in adolescents’ everyday surroundings are needed. This randomized controlled trial studied the preliminary effectiveness, feasibility, and acceptability of interpersonal counseling (IPC) and brief psychosocial support (BPS) in school health and welfare services. The study was conducted in the 28 lower secondary schools of a large city in Southern Finland, randomized to provide either IPC or BPS. Help-seeking 12–16-year-old adolescents with mild-to-moderate depression, with and without comorbid anxiety, were included in the study. Fifty-five adolescents received either 6 weekly sessions of IPC or BPS and two follow-up sessions. Outcome measures included self- and clinician-rated measures of depression, global functioning, and psychological distress/well-being. To assess feasibility and acceptability of the treatments, adolescents’ and counselors’ treatment compliance and satisfaction with treatment were assessed. Both treatments were effective in reducing depressive disorders and improving adolescents’ overall functioning and well-being. At post-treatment, in both groups, over 50% of adolescents achieved recovery based on self-report and over 70% based on observer report. Effect sizes for change were medium or large in both groups at post-treatment and increased at 6-month follow-up. A trend indicating greater baseline symptom severity among adolescents treated in the IPC-providing schools was observed. Adolescents and counselors in both groups were satisfied with the treatment, and 89% of the adolescents completed the treatments and follow-ups. This trial suggests that both IPC and BPS are feasible, acceptable, and effective treatments for mild-to-moderate depression in the school setting. In addition, IPC seems effective even if comorbid anxiety exists. Our study shows that brief, structured interventions, such as IPC and BPS, are beneficial in treating mild-to-moderate depression in school settings and can be administered by professionals working at school.

Trial registrationhttp://www.clinicaltrials.gov. Unique identifier: NCT03001245.

  相似文献   
107.
108.

Introduction

The nature of community pharmacy is changing, shifting from the preparation and distribution of medicines to the provision of cognitive pharmaceutical services (CPS); however, often the provision of traditional services leaves little time for innovative services. This study investigated the time community pharmacists spend on the tasks and activities of daily practice and to what extent they are able to implement CPS-related services in daily practice.

Methods

Self-reporting work sampling was used to register the activities of community pharmacists. A smartphone application, designed specifically for this purpose, alerted participants to register their current activity five times per working day for 6 weeks. Participants also completed an online survey about baseline characteristics.

Results

Ninety-one Dutch community pharmacists provided work-sampling data (7848 registered activities). Overall, 51.5% of their time was spent on professional activities, 35.4% on semi-professional activities, and 13.1% on non-professional activities. The proportion of time devoted to CPS decreased during the workweek, whereas the time spent on traditional task increased.

Discussion and conclusion

This study shows it is feasible to collect work-sampling data using smartphone technology. Community pharmacists spent almost half of their time on semi-professional and non-professional activities, activities that could be delegated to other staff members. In practice, the transition to CPS is hampered by competing traditional tasks, which prevents community pharmacists from profiling themselves as pharmaceutical experts in daily practice.  相似文献   
109.
This study qualitatively examined factors that influenced contraceptive choices in a sample of young, HIV-infected women. Individual qualitative interviews were conducted among 30 vertically and horizontally HIV-infected women (= 26 African American) from the ages of 14 to 24 years (Mean age = 20.9 years). We recruited sample groups with the following characteristics: (a) current contraceptive/condom use with ≥1 child (= 11); (b) current contraceptive/condom use with no children (= 12); and (c) no current contraceptive/condom use with no children (= 7). A semi-structured interview guide was used to ask participants about factors influencing past and current contraceptive choices. Individual interviews were digitally recorded and transcribed verbatim; analyses to identify core themes were informed by the Grounded Theoretical approach. Young, HIV-infected women did not identify their HIV serostatus or disease-related concerns as influential in their contraceptive decisions. However, they reported that recommendations from health-care providers and input from family and friends influenced their contraceptive choices. They also considered a particular method’s advantages (e.g., menstrual cycle improvements) and disadvantages (e.g., increased pill burden) when selecting a method. Findings suggested that HIV-infected young women’s contraceptive decisions were influenced by factors other than those related to their infection.  相似文献   
110.
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