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   3597篇
  免费   195篇
  国内免费   18篇
耳鼻咽喉   59篇
儿科学   281篇
妇产科学   64篇
基础医学   504篇
口腔科学   147篇
临床医学   207篇
内科学   667篇
皮肤病学   75篇
神经病学   162篇
特种医学   108篇
外科学   656篇
综合类   93篇
一般理论   1篇
预防医学   114篇
眼科学   120篇
药学   285篇
  1篇
中国医学   23篇
肿瘤学   243篇
  2023年   34篇
  2022年   53篇
  2021年   160篇
  2020年   76篇
  2019年   114篇
  2018年   127篇
  2017年   82篇
  2016年   116篇
  2015年   123篇
  2014年   164篇
  2013年   203篇
  2012年   342篇
  2011年   315篇
  2010年   181篇
  2009年   157篇
  2008年   237篇
  2007年   216篇
  2006年   183篇
  2005年   168篇
  2004年   153篇
  2003年   132篇
  2002年   91篇
  2001年   31篇
  2000年   27篇
  1999年   25篇
  1998年   26篇
  1997年   23篇
  1996年   16篇
  1995年   12篇
  1994年   10篇
  1993年   16篇
  1992年   14篇
  1991年   20篇
  1990年   5篇
  1989年   9篇
  1988年   16篇
  1987年   11篇
  1986年   12篇
  1985年   10篇
  1984年   14篇
  1983年   10篇
  1982年   8篇
  1981年   7篇
  1980年   5篇
  1979年   7篇
  1978年   12篇
  1977年   4篇
  1976年   6篇
  1973年   4篇
  1970年   3篇
排序方式: 共有3810条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
OBJECTIVE: To evaluate the user experience and acceptability of an electronic patient monitoring system. SETTING AND PARTICIPANTS: 822 Military and civilian personnel at a health clinic at a major US military headquarters used an Internet and telephone-based electronic monitoring system to report vaccination-site responses and symptoms after receiving the smallpox vaccination. Focus groups of vaccinees were conducted to help develop a survey about the experience that was distributed to 379 vaccinees (96% completion rate). RESULTS: Users of the electronic monitoring system reported that it was fast and easy to use and reported they would use a system like this again and recommend an electronic monitoring system to a friend or relative. Most users (84%) were comfortable with a physician tracking their vaccine reaction using their electronic reports, but only half (51%) were comfortable with eliminating the post-vaccination follow-up visit with their health-care provider based on their electronic reports. CONCLUSIONS: This electronic monitoring system was well received by vaccinees and allowed health-care providers to track the status of vaccinees. However, vaccinees were not comfortable replacing a physician visit with electronic monitoring, at least for the smallpox vaccination. A monitoring system like this may be useful in public health settings, such as mass vaccination or prophylaxis during a bioterrorism event, a pandemic influenza outbreak, or another public health emergency.  相似文献   
6.
7.
Magnetic resonance spectroscopic imaging (MRSI) provides spatially resolved metabolite information that is invaluable for both neuroscience studies and clinical applications. However, lengthy data acquisition times, which are a result of time-consuming phase encoding, represent a major challenge for MRSI. Fast MRSI pulse sequences that use echo-planar readout gradients, such as proton echo-planar spectroscopic imaging (PEPSI), are capable of fast spectral-spatial encoding and thus enable acceleration of image acquisition times. Combining PEPSI with recent advances in parallel MRI utilizing RF coil arrays can further accelerate MRSI data acquisition. Here we investigate the feasibility of ultrafast spectroscopic imaging at high field (3T and 4T) by combining PEPSI with sensitivity-encoded (SENSE) MRI using eight-channel head coil arrays. We show that the acquisition of single-average SENSE-PEPSI data at a short TE (15 ms) can be accelerated to 32 s or less, depending on the field strength, to obtain metabolic images of choline (Cho), creatine (Cre), N-acetyl-aspartate (NAA), and J-coupled metabolites (e.g., glutamate (Glu) and inositol (Ino)) with acceptable spectral quality and localization. The experimentally measured reductions in signal-to-noise ratio (SNR) and Cramer-Rao lower bounds (CRLBs) of metabolite resonances were well explained by both the g-factor and reduced measurement times. Thus, this technology is a promising means of reducing the scan times of 3D acquisitions and time-resolved 2D measurements.  相似文献   
8.
The purpose of the present investigation was to determine the effect of continuous exposure to the organophosphate monocrotophos at 2.5 ppm for over a period of 2 through 45 days on protein, RNA, and DNA contents and on 5'-nucleotidase activity in the liver of Tilapia mossambica. Protein content was decreased by 45% after 5 days, returned to control levels at 10-30 days, and again decreased by 45 days. DNA content was decreased by 2 days, returned to control values by 5 days, and remained constant throughout the exposure. In contrast, RNA content was significantly lower starting from 2 through 45 days of exposure. 5'-Nucleotidase activity showed a transient increase at 5 and 30 days of monocrotophos exposure. These results indicate that monocrotophos altered the protein, DNA, and RNA contents and the 5'-nucleotidase activity levels as early as 2 and 5 days. However, these changes were reversed by 10 days and after a short period of recovery, the alterations reappeared. This supports our earlier histological observations of hepatic pathology during monocrotophos exposure.  相似文献   
9.
This study deals with the generation and characterization of various solid-state forms of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor. The drug was subjected to polymorphic screen using different solvents to explore the possibility of existence of different solid forms. N,N-Dimethyl acetamide (DMA) and N,N-dimethyl formamide (DMF) yielded solvates in 1:1 stoichiometric ratio. Quench cooling of the melt resulted in amorphous form of the drug. All these solid-state forms were characterized by thermoanalytical (DSC, TGA, HSM), crystallographic (XRD), microscopic (polarized, SEM), spectroscopic (FTIR), and elemental analysis techniques. Solubility and van't Hoff studies were carried out for their thermodynamic interpretation. Influence of morphology of different solid-state forms on flow behavior was also investigated. Molecular modeling studies were used to elucidate the interaction between solute and solvent molecules in the solvate.  相似文献   
10.
Influence of some sugars was studied on activity of purified cellulase enzymes produced by two white-rot basidiomycetes cultures in submerged fermentation. Exo- and endo-glucanases were found to be stimulated by glucose, sucrose and xylose, but β-glucosidase was inhibited by all sugars tested except sucrose being neutral. Cellobiose severely inhibited all three cellulase activities at all three concentrations taken in reaction mixture.  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