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   1777篇
  免费   138篇
  国内免费   23篇
耳鼻咽喉   1篇
儿科学   45篇
妇产科学   57篇
基础医学   180篇
口腔科学   32篇
临床医学   174篇
内科学   368篇
皮肤病学   41篇
神经病学   102篇
特种医学   97篇
外科学   397篇
综合类   31篇
预防医学   141篇
眼科学   18篇
药学   122篇
中国医学   1篇
肿瘤学   131篇
  2023年   11篇
  2021年   34篇
  2020年   24篇
  2019年   29篇
  2018年   33篇
  2017年   32篇
  2016年   20篇
  2015年   33篇
  2014年   40篇
  2013年   67篇
  2012年   92篇
  2011年   115篇
  2010年   53篇
  2009年   56篇
  2008年   96篇
  2007年   93篇
  2006年   95篇
  2005年   80篇
  2004年   52篇
  2003年   64篇
  2002年   49篇
  2001年   53篇
  2000年   64篇
  1999年   34篇
  1998年   25篇
  1997年   14篇
  1996年   16篇
  1995年   10篇
  1994年   23篇
  1993年   10篇
  1992年   57篇
  1991年   46篇
  1990年   41篇
  1989年   38篇
  1988年   23篇
  1987年   20篇
  1986年   32篇
  1985年   26篇
  1984年   22篇
  1983年   23篇
  1982年   10篇
  1979年   15篇
  1978年   13篇
  1977年   13篇
  1975年   10篇
  1974年   19篇
  1973年   10篇
  1969年   10篇
  1968年   11篇
  1967年   13篇
排序方式: 共有1938条查询结果,搜索用时 46 毫秒
1.
The use of multifunctional materials for water remediation is a modern approach where adsorption phenomena and heterogeneous photocatalysis can be applied for the removal of pollutants. Since the ideal remediation system should be able to remove both organic and inorganic pollutants, a crucial aspect to consider is the knowledge of operational parameters affecting the removal process, especially when heavy metal ions are present in concoction as in real systems. Given the proven efficiency of multifunctional TiO2/Alg/FeNPs magnetic beads for the removal of model organic pollutants, this study investigated the possibility to exploit such system also for the removal of mixed heavy metals (MHM), specifically Cr(III), Cu(II), and Pb(II) ions, under ultraviolet irradiation at a wavelength of 254 nm. After a preliminary screening on the optimal catalyst loading, operating parameters such as the initial concentration of metal ions, contact and irradiation time, and pH were investigated to optimize the removal of metal ions using response surface methodology (RSM) via Box–Behnken design. Starting from a MHM solution containing 44 ppm of each metal ion, the removal of Pb(II), Cr(III), and Cu(II) ions in the aqueous solution was nearly completed (>98.4%) for all three ions within 72 min of irradiation at almost neutral pH (pH = 6.8). The stability of TiO2/Alg/FeNPs was confirmed by retrieving and reusing the beads in three consecutive cycles of heavy metals removal without observing significant changes in catalyst efficiency.  相似文献   
2.
The novel coronavirus SARS‐CoV‐2 has emerged as one of the most compelling and concerning public health challenges of our time. To address the myriad issues generated by this pandemic, an interdisciplinary breadth of research, clinical and public health communities has rapidly engaged to collectively find answers and solutions. One area of active inquiry is understanding the mode(s) of SARS‐CoV‐2 transmission. Although respiratory droplets are a known mechanism of transmission, other mechanisms are likely. Of particular importance to global health is the possibility of vertical transmission from infected mothers to infants through breastfeeding or consumption of human milk. However, there is limited published literature related to vertical transmission of any human coronaviruses (including SARS‐CoV‐2) via human milk and/or breastfeeding. Results of the literature search reported here (finalized on 17 April 2020) revealed a single study providing some evidence of vertical transmission of human coronavirus 229E; a single study evaluating presence of SARS‐CoV in human milk (it was negative); and no published data on MERS‐CoV and human milk. We identified 13 studies reporting human milk tested for SARS‐CoV‐2; one study (a non‐peer‐reviewed preprint) detected the virus in one milk sample, and another study detected SARS‐CoV‐2 specific IgG in milk. Importantly, none of the studies on coronaviruses and human milk report validation of their collection and analytical methods for use in human milk. These reports are evaluated here, and their implications related to the possibility of vertical transmission of coronaviruses (in particular, SARS‐CoV‐2) during breastfeeding are discussed.  相似文献   
3.
4.
Objectives

XR-hysterosalpingography currently represents the gold standard for tubal pathology evaluation. Magnetic resonance-HSG is an innovative technique. With our study, we aim to comprehend if and how MR-HSG, compared to traditional XR-HSG, could give us this additional information in the diagnostic/therapeutic process.

Materials and methods

This study included 19 patients between 30 and 42 years old (average age 37.7) affected by infertility. Patients underwent contextually both XR-HSG and MR-HSG, using a single catheterization. The dynamic MR-HSG exam consisted a MR sequence during contrast administration through the cervical catheter.

Results

Both XR-HSG and MR-HSG documented that 15 of the 19 patients had bilateral tubal patency, while four patients had monolateral tubal patency. However, MR-HSG allowed us to diagnose additional findings:

  • Two active endometriosis foci in adnexal localization and a condition of adenomyosis

  • A unicornuate uterus malformation

  • A submucous uterine myoma near the tubal ostium

  • A decrease of the ovarian reserve in a patient

So MR-HSG could potentially detect in 10/19 (52%) women the cause of their infertility, compared to 4/19 (21%) detected with XR-HSG and about 30% of women would have resulted as false negatives if we only used XR-HSG.

Finally, with a questionnaire, we demonstrated that MR-HSG is less painful than XR-HSG.

Conclusions

These data thus confirm that XR-HSG and MR-HSG present the same diagnostic of assessing tubal patency. We also demonstrated that MR-HSG is able to detect further collateral findings that could likewise be a possible therapeutic target and it could possibly become the new gold standard in female infertility diagnostics.

  相似文献   
5.
6.
7.
8.
9.
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