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   2032篇
  免费   125篇
  国内免费   16篇
耳鼻咽喉   12篇
儿科学   84篇
妇产科学   44篇
基础医学   321篇
口腔科学   50篇
临床医学   143篇
内科学   321篇
皮肤病学   13篇
神经病学   151篇
特种医学   70篇
外科学   164篇
综合类   63篇
预防医学   133篇
眼科学   152篇
药学   284篇
中国医学   50篇
肿瘤学   118篇
  2023年   12篇
  2022年   40篇
  2021年   60篇
  2020年   33篇
  2019年   49篇
  2018年   55篇
  2017年   37篇
  2016年   61篇
  2015年   56篇
  2014年   92篇
  2013年   90篇
  2012年   128篇
  2011年   138篇
  2010年   83篇
  2009年   61篇
  2008年   105篇
  2007年   85篇
  2006年   80篇
  2005年   66篇
  2004年   70篇
  2003年   69篇
  2002年   60篇
  2001年   40篇
  2000年   41篇
  1999年   29篇
  1998年   16篇
  1997年   23篇
  1996年   14篇
  1995年   10篇
  1993年   13篇
  1992年   47篇
  1991年   43篇
  1990年   32篇
  1989年   43篇
  1988年   29篇
  1987年   29篇
  1986年   15篇
  1985年   17篇
  1984年   26篇
  1983年   20篇
  1982年   10篇
  1980年   8篇
  1979年   23篇
  1976年   11篇
  1975年   11篇
  1974年   12篇
  1973年   13篇
  1972年   14篇
  1971年   10篇
  1969年   12篇
排序方式: 共有2173条查询结果,搜索用时 15 毫秒
141.
Heterotopic pregnancy involves coexisting intra-uterine and extra-uterine gestations. The incidence for natural uninduced pregnancy is 1 in 30,000 pregnancies. However the incidence is increasing with ovulation induction and artificial reproductive techniques. In more than 90% heterotopic pregnancies, the ectopic implantation is in the fallopian tube. A case of undiagnosed term heterotopic pregnancy in a 26-year-old primigravida is reported. She was referred from a practising obstetrician as a case of term twin pregnancy. Her regular antenatal records suggested intra-uterine growth restriction in one foetus of the twin. After confirmation of findings with ultrasound she was taken for emergency caesarean section. Heterotopic pregnancy was diagnosed on opening the abdomen. The term abdominal pregnancy was managed successfully. Although remained undiagnosed till term, good maternal and perinatal outcome was noted with survival of both the babies.  相似文献   
142.
143.
A simple and efficient route to develop various novel functionalized MOF materials for rapid and excellent recovery of U(vi) from aqueous medium, along with selective sensing has been demonstrated in the present study. In this connection, a set of four distinct post synthetically modified (PSM) iso-reticular metal organic frameworks were synthesized from IRMOF-3 namely, IRMOF-PC (2-pyridine carboxaldehyde), IRMOF-GA (glutaric anhydride), IRMOF-SMA (sulfamic acid), and IRMOF-DPC (diphenylphosphonic chloride) for the recovery and sensing of U(vi) from aqueous medium. The MOFs were characterized by Fourier transform infrared spectroscopy (FTIR), powder XRD, BET surface area analysis, thermogravimetric analysis (TGA), NMR (13C, 1H and 31P), Scanning Electron Microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Among all MOFs, post synthetically modified IRMOF-SMA showed enhanced thermal stability of about 420 °C. The MOFs were investigated for U(vi) sorption studies using a batch technique. All the MOFs exhibit excellent sorption capacity towards U(vi) (>90%) and maximum uptake was observed at pH 6. Sorption capacity of MOFs have the following order; IRMOF-3-DPC (300 mg U g−1) > IRMOF-SMA (292 mg U g−1) > IRMOF-PC (289 mg U g−1) > IRMOF-GA (280 mg U g−1) > IRMOF-3 (273 mg U g−1). IRMOF-DPC shows rapid sorption of uranium within 5 min with excellent uptake of U(vi) (>99%). The desorption of U(vi) was examined with different eluents and 0.01 M HNO3 was found to be most effective. The fluorescence sensing studies of U(vi) via IRMOF-3 and its PSM MOFs revealed high sensitivity and selectivity towards U(vi) over other competing rare earth metal ions (La3+, Ce4+, Sm3+, Nd3+, Gd3+, and Eu3+), wherein IRMOF-GA displayed an impressive detection limit of 0.36 mg L−1 for U(vi).

Four IRMOFs following PSM strategy were prepared. The MOFs were characterized by different techniques and were investigated for U(vi) sorption. PSM MOFs displayed impressive fluorescent sensing and selectivity of U(vi) over competing metal ions.  相似文献   
144.
145.

Background:

Studies show that immunization among migrant children is poor. India has a dropout rate of 17.7% between Bacillus Calmette-Guιrin (BCG) and measles (District Level Household Survey (DLHS)-3). Haridwar district had the highest dropout rate of 27.4% from BCG to diphtheria, pertussis, and tetanus (DPT) 3 (DLHS-3) in Uttarakhand. We evaluated the Universal Immunization Programme (UIP) among migrants in Haridwar in two blocks.

Materials and Methods:

We developed input, process, and output indicators on infrastructure, human resources, and service delivery. A facility, session site and cross-sectional survey of 180 children were done and proportions for various indicators were estimated. We determined factors associated with not taking vaccination using multivariate analysis.

Results:

We surveyed 11 cold chain centers, 25 subcenters, 14 sessions, and interviewed 180 mothers. Dropouts were supposed to be tracked using vaccination card counterfoils and tracking registers. The dropout rate from BCG to DPT3 was 30%. Lack of knowledge (adjusted odds ratio (AOR) 6.6,95% confidence interval (CI) 2.6–16.7), mother not being decision maker (AOR 4.0,95%CI 1.7–9.2), lack of contact by Accredited Social Health Activist (ASHA; AOR 3.0,95%CI 1.1–7.7), not being given four post-vaccination messages (AOR 7.7, 95% CI 2.9–20.2), and longer duration of stay in Haridwar (AOR 3.0 95% 1.9–7.6) were risk factors for nonimmunization. The reasons stated by mothers included lack of awareness of session site location (67%) and belief that child should only be vaccinated in their resident district (43%).

Conclusions:

There was low immunization coverage among migrants within adequate supervision, poor cold chain maintenance, and improper tracking of dropouts. Mobile immunization teams, prelisting of migrant children, and change in incentives of ASHAs for child tracking were needed. A monitoring plan for sessions and cold chain needed enforcement.  相似文献   
146.
147.
In the present study, a Box-Behnken experimental design was employed to statistically optimize the formulation parameters of chitosan phthalate and chitosan succinate microspheres preparation. These microspheres can be useful for oral insulin delivery system. The effects of three parameters namely polymer concentration, stirring speed and cross linking agent were studied. The fitted mathematical model allowed us to plot response surfaces curves and to determine optimal preparation conditions. Results clearly indicated that the crosslinking agent was the main factor influencing the insulin loading and releasing. The in vitro results indicated that chitosan succinate microspheres need high amount of crosslinking agent to control initial burst release compared to chitosan phthalate microspheres. The reason may be attributed that chitosan succinate is more hydrophilic than chitosan phthalate. The relative pharmacological efficacy for chitosan phthalate and chitosan succinate microspheres (18.66 ± 3.84%, 16.24 ± 4%) was almost three-fold higher than the efficacy of the oral insulin administration (4.68 ± 1.52%). These findings suggest that these microspheres are promising carrier for oral insulin delivery system.  相似文献   
148.
149.
In order to clarify the histological and immunohistochemical characteristics of suppurative granuloma in abscess-forming granulomatous lymphadenitis (AGL), and the relation between AGL and cat scratch disease (CSD), 36 cases of AGL were studied. The combined results showed that there were two types of suppurative granulomas. The suppurative granulomas histologically revealed small lymphocytes of predominantly T cell phenotype distributed among the epithelioid histiocytes bordering central necrotic areas in the suppurative granulomas. These suppurative granulomas could be further subdivided into two groups, mainly those with and without the intermingling of large transformed cells of B-cell phenotypes: Type B granuloma with large transformed B cells and Type A without large transformed B cells. Both types of granulomas were observed in a varying degree in most cases. According to the predominant type of granulomas, 36 patients with AGL were further classified into two groups: Group I of Type A dominance and Group II of Type B dominance. Warthin-Starry (WS) silver stain positive bacteria, which are said to be a causative agent of CSD, were present in about 50% of both groups. No Brown-Hopps' Gram-positive bacteria, fungus, toxoplasma, Chlamydia or Bacillus Calmette-Guerin antigen were found in any case. Clinically, there was no significant difference between these two groups. On the other hand, the detection of WS-positive bacteria seemed to have some relationship with the duration of disease and the history of exposure to cats, and 70% of AGL cases occurred in autumn without a single concurrent epidemic.  相似文献   
150.
Ten smoker sportsmen and 17 non-smoker sportsmen and 41 smoker non-sportsmen were studied. Lung function was assessed by means of Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), the ratio of FEV1 to FVC (FEV1%) and Peak Expiratory Flow Rate (PEFR). For the smokers, all the tests were conducted before smoking (BS) and 30 min after smoking (AS) two cigarettes consecutively to observe the acute effect of smoking. In the smoker sportsmen there was no significant difference between BS and AS measures of lung function. Before smoking smoker sportsmen had lower values for FEV1, FEV1% and PEFR than non-smoker sportsmen (p less than 0.05). However, smoker sportsmen show higher BS values of FEV1 (p less than 0.01), FEV1% (p less than 0.01) and PEFR (p less than 0.05) compared with those of smoker non-sportsmen who had similar smoking indices. These results indicated that the smoker sportsmen, despite exhibiting some degree of lung function impairment in relation to non-smoker sportsmen, still maintained rather better lung function status than the smoker non-sportsmen.  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