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   716篇
  免费   48篇
  国内免费   12篇
耳鼻咽喉   2篇
儿科学   34篇
妇产科学   6篇
基础医学   75篇
口腔科学   8篇
临床医学   79篇
内科学   133篇
皮肤病学   8篇
神经病学   34篇
特种医学   157篇
外科学   72篇
综合类   32篇
一般理论   2篇
预防医学   30篇
眼科学   15篇
药学   34篇
中国医学   3篇
肿瘤学   52篇
  2022年   3篇
  2021年   9篇
  2020年   10篇
  2019年   13篇
  2018年   13篇
  2017年   6篇
  2016年   13篇
  2015年   15篇
  2014年   17篇
  2013年   30篇
  2012年   24篇
  2011年   18篇
  2010年   26篇
  2009年   26篇
  2008年   25篇
  2007年   35篇
  2006年   21篇
  2005年   23篇
  2004年   23篇
  2003年   19篇
  2002年   18篇
  2001年   17篇
  2000年   13篇
  1999年   15篇
  1998年   42篇
  1997年   34篇
  1996年   18篇
  1995年   16篇
  1994年   15篇
  1993年   21篇
  1992年   7篇
  1991年   7篇
  1990年   17篇
  1989年   17篇
  1988年   14篇
  1987年   14篇
  1986年   18篇
  1985年   19篇
  1984年   4篇
  1983年   6篇
  1982年   11篇
  1981年   9篇
  1980年   9篇
  1978年   9篇
  1977年   9篇
  1976年   7篇
  1975年   7篇
  1973年   4篇
  1972年   3篇
  1970年   2篇
排序方式: 共有776条查询结果,搜索用时 31 毫秒
1.
2.
3.
The first attempt to provide a data base for comparing a pilot and full scale system for various organics produced results that require further investigation. Although both of the pilot systems had longer average contact times than their respective full scale systems, a uniform pattern of longer service time for the different substances evaluated did not occur. These results may not be consistent with the data collected using pilot contactors in series to observe the effect of contact time. The series pilot contactor system provided data that show the effect of varying empty bed contact time on the removal of the organic substances studied. Improved effluent quality was generally achieved with increased contact time. A pilot series system similar to the one used is considered essential in collecting and interpreting design data. A method of statistical interpretation of the results was developed that shows promise for use in evaluating pilot column results. Further evaluation is required to assess that all pertinent factors were properly controlled during the investigation. Also, repeat testing will be conducted, attempting to control more closely the contact times between the pilot and full scale systems. The comparative granular activated carbon particle sizes also will be more closely examined. Although pilot to full-scale comparisons have been successfully performed for single parameters, the results for multiple organics have not been previously reported. Such a data base, if properly collected, will provide invaluable background in assessing what types of design safety factors are required when using pilot column data to predict full scale results for a naturally occurring mixture of organic substances.  相似文献   
4.
5.
6.
The authors describe their experience with methyl tertiary butyl ether (MTBE) in a larger series of patients than previously reported in order to acquaint physicians with both its effectiveness for dissolution of common bile duct calculi and the limitations of its use. Ten patients with 13 biliary calculi underwent percutaneous stone dissolution treatment with the experimental cholesterol solvent, MTBE. Three stones completely dissolved within 30 minutes, seven were reduced in size, and three were visibly unaffected. All stones not completely dissolved were easily extracted by means of a stone basket except for one in a patient taken to surgery. Although MTBE perfusion is an effective technique for management of biliary calculi, practitioners should be aware that its use is quite time consuming and its odor difficult to control.  相似文献   
7.
DL-2-Amino-4-phosphonobutyric acid (APB) suppresses activity in retinal ON pathways. It is generally assumed that loss of the ON pathway would result in loss of ON responses in the visual system. We tested this assumption by recording activity from the optic nerves of intact goldfish (Carassius auratus) before and after intraocular injection of APB. Whole-nerve responses to increments and decrements of light were compared to electroretinogram responses and to tectal evoked potentials. APB severely reduced the amplitude of the electroretinogram b-wave but left ON and OFF responses from the optic nerve and tectum intact, although decreased in sensitivity. We conclude that APB does not completely eliminate ON responses in the visual system, at least in goldfish. The selectivity and effectiveness of APB must be evaluated in other species before this agent can be relied upon as a useful tool in understanding the roles of ON and OFF pathways in visual function.  相似文献   
8.
Reiman  TH; Heiken  JP; Totty  WG; Lee  JK 《Radiology》1988,169(2):564-566
Limited-field-of-view radio-frequency receiver antennas provide improved near-field sensitivity for magnetic resonance imaging by decreasing the antenna volume. The Helmholtz-type surface coil, consisting of two flat rings, is an organ-encompassing antenna that takes advantage of this principle to yield an improved signal-to-noise ratio (S/N). The coil was tested in a group of 50 patients and 16 healthy volunteers. Images obtained with the Helmholtz coil demonstrated quantitatively superior S/N of 2.2-fold or greater than that of comparison body coil images, as well as qualitatively superior anatomic resolution.  相似文献   
9.
10.
Uroscopy in the 21st century: high-field NMR spectroscopy   总被引:1,自引:1,他引:0  
From the experiments described, it can be seen that there are different research approaches that can be taken and these are summarized in Table 1. Whereas much scientific research is principally hypothesis led, there remains, nevertheless, an important place for exploratory research. High resolution NMR can measure, directly and simultaneously, a wide range of endogenous metabolites in biological fluids and has the unique capability of providing structural information on the metabolites detected. It has proved to be a powerful research tool with which to study inherited metabolic diseases, renal disease, drug metabolism, and toxicity, and can be used to monitor the effects of drug therapy. For instance, by using a library of experimental toxins one can map the metabolic profile of site-specific nephron injury. With this approach in man one could eventually take an unknown disease such as Balkan nephropathy and predict the initial site of tubular injury, the mode of injury and therefore the kind of toxin capable of producing that injury. NMR spectroscopic techniques are still advancing rapidly, with ever increasing sensitivity and sophistication of NMR pulse sequences to enhance structural elucidation in complex mixtures. Given the advances in directly coupled HPLC-NMR and even HPLC-NMR-mass spectroscopy it is likely that these technologies in conjunction with pattern recognition will make major contribution to our understanding of renal processes and provide new diagnostic insights in the 21st century.   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