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   1334篇
  免费   152篇
  国内免费   49篇
耳鼻咽喉   8篇
儿科学   41篇
妇产科学   8篇
基础医学   162篇
口腔科学   22篇
临床医学   155篇
内科学   309篇
皮肤病学   27篇
神经病学   114篇
特种医学   225篇
外科学   144篇
综合类   39篇
一般理论   2篇
预防医学   138篇
眼科学   19篇
药学   85篇
中国医学   1篇
肿瘤学   36篇
  2022年   14篇
  2021年   33篇
  2020年   10篇
  2019年   13篇
  2018年   18篇
  2017年   10篇
  2016年   23篇
  2015年   36篇
  2014年   33篇
  2013年   32篇
  2012年   51篇
  2011年   49篇
  2010年   22篇
  2009年   35篇
  2008年   62篇
  2007年   96篇
  2006年   58篇
  2005年   42篇
  2004年   34篇
  2003年   31篇
  2002年   38篇
  2001年   26篇
  2000年   38篇
  1999年   31篇
  1998年   40篇
  1997年   37篇
  1996年   41篇
  1995年   36篇
  1994年   28篇
  1993年   31篇
  1992年   54篇
  1991年   31篇
  1990年   28篇
  1989年   41篇
  1988年   37篇
  1987年   25篇
  1986年   30篇
  1985年   23篇
  1984年   15篇
  1983年   16篇
  1982年   12篇
  1981年   14篇
  1980年   13篇
  1979年   10篇
  1978年   16篇
  1977年   16篇
  1976年   18篇
  1975年   9篇
  1969年   10篇
  1968年   11篇
排序方式: 共有1535条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Precise and accurate inversion-recovery (PAIR) magnetic resonance (MR) measurements of T1 were obtained in eight brain regions and cerebrospinal fluid of 26 healthy volunteers. Accuracy of the technique was assessed by measuring T1 in small fluid volumes with the PAIR technique and with two independent spectroscopic techniques. The mean difference between T1 measured with PAIR and with the two spectroscopic techniques was 3.1% ± 1.3. The precision (reproducibility) of measurements with the PAIR technique was excellent. The coefficient of variation (CV) across 16 measurements in a head phantom was 2.0%, compared with a CV of 2.7% across 45 separate measurements in a single subject. The within-subject CV was 1.8% ± 0.6 in white matter and 1.4% ± 1.0 in basal ganglia. The between-subject CV in 26 healthy volunteers was 3.6% ± 0.6 in white matter and 4.1% ± 1.9 in basal ganglia. Comparison between a patient with an active recurrent brain tumor and an agematched patient with an inactive brain tumor showed that T1 was significantly elevated throughout the brain of the active-tumor patient, especially in white matter tracts, even though no tumor or edema was detected in the white matter on standard MR images. Comparisons between five brain tumor patients and four healthy volunteers of similar age showed that T1 was significantly and substantially elevated throughout the white matter tracts and in the caudate nucleus, putamen, and thalamus. These results are consistent with the hypothesis that white matter tracts are selectively vulnerable to edema and that T1 increases in white matter are a sensitive indicator of patient status or tumor aggressiveness.  相似文献   
6.
Results of clinical, contrast enema (CE), and computed tomographic (CT) examinations in 39 patients with perforated colorectal neoplasms were retrospectively reviewed. Twenty patients were toxemic at initial presentation, but in only four patients was the diagnosis of perforated colorectal neoplasm initially suspected clinically. CE study was performed in 22 patients and enabled the diagnosis of perforated neoplasm in 11 cases, neoplasm alone in eight, and neither neoplasm nor perforation in three. CT was performed in 38 patients and enabled the diagnosis of perforated neoplasm in 36; pericolic phlegmon but no mass lesion was evident in two. In 16 patients, CT also demonstrated metastatic disease. Because of its reliability in establishing the diagnosis and staging the extent of the inflammatory and neoplastic disease, CT is indicated in cases of suspected or proved perforated colorectal neoplasm and in cases in which CE study findings are indeterminate or suggestive of perforated neoplasm.  相似文献   
7.
报道了氯仿重结晶的棉酚的化学性质,样品在不同温度下干燥恒重后,经熔点、薄层层析、紫外光谱、红外光谱、X-射线衍射、热重量分析、元素(C,H,Cl)分析及棉酚合量测定等一系列的分析,确证了在60℃以下棉酚与氯仿成溶剂化物(solvate)。随着干燥温度的升高或在室温长时间的贮存,此现象逐渐消失,100℃真空干燥恒重后成为纯棉酚。  相似文献   
8.
Proliferation of rheumatoid and control peripheral blood mononuclear cells to OKT3, phorbol myristic acid (PMA), phytohemagglutinin (PHA), tuberculin PPD and in the autologous mixed lymphocyte reaction (AMLR) was investigated. Only the responses to PPD and in the AMLR were depressed. This was not due to suppression by OKT8 lymphocytes. The proportion of antigen responsive (T4+ 4B4+) cells was normal but suppressor-inducer (T4+ 2H4+) cells were decreased. The depressed response was not completely restored by addition of recombinant interleukin-2. We propose that a basic defect in rheumatoid arthritis resides in T lymphocytes which react to self-major histocompatibility complex antigens either on their own, as in the AMLR, or as restriction elements in the presentations of soluble antigen.  相似文献   
9.
Child care agencies in Ohio were surveyed concerning their programs and child care workers so as to better understand factors that contribute to job stress, attrition, and satisfaction. The survey provided data regarding the population served at the agencies and the characteristics of child care workers, their services, concerns, desires, and rewards. The findings indicate that environmental variables contribute largely to perceived concern and desired changes, whereas success with children provides a prominent source of job satisfaction.  相似文献   
10.
The purpose of this prospective, randomized, double-blind study was to determine if the volume of a fixed milligram dose of hyperbaric tetracaine hydrochloride injected into the subarachnoid space affected the average maximal dermatomal spread of sensory anesthesia, determined by pinprick testing. One hundred two adults received spinal hyperbaric tetracaine in a volume of 2 mL, 3 mL, or 4 mL with the dose based on the patient's height. The addition of 0.2 mg of epinephrine to the anesthetic solution was allowed at the discretion of the attending anesthesiologist. A two-way analysis of variance (ANOVA) demonstrated that neither the dose selected nor the use of epinephrine affected anesthetic spread. ANOVA showed that anesthetic volume insignificantly affects the spread of sensory anesthesia. A Tukey HSD multiple comparisons test demonstrated a mean difference greater than 1 sensory dermatome between volumes of 2 mL and 4 mL, which was clinically detectable but statistically insignificant. Increasing the volume of hyperbaric spinal tetracaine solutions to improve anesthetic spread is unjustified.  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