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   15664篇
  免费   864篇
  国内免费   127篇
耳鼻咽喉   136篇
儿科学   272篇
妇产科学   160篇
基础医学   1893篇
口腔科学   261篇
临床医学   1104篇
内科学   4531篇
皮肤病学   362篇
神经病学   1012篇
特种医学   528篇
外科学   2758篇
综合类   105篇
预防医学   500篇
眼科学   176篇
药学   1038篇
中国医学   37篇
肿瘤学   1782篇
  2023年   109篇
  2022年   202篇
  2021年   442篇
  2020年   246篇
  2019年   323篇
  2018年   431篇
  2017年   295篇
  2016年   420篇
  2015年   438篇
  2014年   537篇
  2013年   623篇
  2012年   1060篇
  2011年   1118篇
  2010年   602篇
  2009年   515篇
  2008年   915篇
  2007年   1001篇
  2006年   921篇
  2005年   913篇
  2004年   865篇
  2003年   723篇
  2002年   788篇
  2001年   310篇
  2000年   274篇
  1999年   295篇
  1998年   163篇
  1997年   134篇
  1996年   113篇
  1995年   98篇
  1994年   109篇
  1993年   80篇
  1992年   196篇
  1991年   160篇
  1990年   162篇
  1989年   143篇
  1988年   118篇
  1987年   98篇
  1986年   69篇
  1985年   80篇
  1984年   65篇
  1983年   55篇
  1982年   27篇
  1981年   35篇
  1980年   29篇
  1979年   47篇
  1978年   29篇
  1977年   28篇
  1972年   29篇
  1970年   28篇
  1969年   27篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Direct measurement of intra-arterial blood pressure (BP) for 24-h provides approximately 100,000 values that vary enormously, but each (BPi) can be expressed by the equation BPi = BP0 + DeltaBPi (BP0, base BP; DeltaBPi, BP increment, i=1, 2, ..., 100 x 10(3)). About 20% of outpatients with hypertension exhibit white-coat hypertension (WCH). In such patients, DeltaBPc (i = c; c, time at the clinic) is surmised to be large. A method for explaining the physiological factors in DeltaBPc and the estimation of base BP in the outpatient clinic is important. This study addresses this issue. A total of 293 subjects were divided into four groups: 1) WCH group, 45 individuals (office BP > or = 140/90 mmHg and 24-h indirect BP < 125/80 mmHg); 2) normotensive (NT) group, 84 controls matched for age and sex; 3) WHO-I group, 95 hypertensive patients with WHO stage I (office BP > or = 140/90 mmHg and 24-h BP > or = 125/80 mmHg); and 4) WHO-II group, 69 hypertensive patients with WHO stage II. Their BPc and heart rate (HR; HRc, clinic HR) values were measured by a BP-ECG monitoring device in the outpatient clinic. Power-spectral analysis was used to obtain the ratio between the low-frequency component (LF) and high-frequency component (HF) of ECG-RR variability (LF/HF = LH). Twenty-four-hour indirect BP (and BP0) and base HR (HR0) were measured by a portable device (TM2425) at 30-min intervals. Then, DeltaBPc (= BPc - BP0) was estimated by performing linear multivariate analysis applying the model equation DeltaBPc = (BPc -alphaLH)(1-betaHR0/HRc) + epsilon to the above variables (alpha and beta, constant values; epsilon, error). This model equation made it possible to estimate BP0 (and DeltaBPc) with a high coefficient of correlation (r > or = 0.85, mean of error less than 0.82 +/- 5.9 mmHg). The predictive accuracy for discrimination between WCH and sustained hypertension (WHO-I and WHO-II groups) by this equation was 88%. The new DeltaBP-estimation device (BP-ECG monitor) enabled us to infer BP0 and is therefore useful in estimating WCH in the outpatient clinic.  相似文献   
4.
5.
6.
7.
8.
Killer lymphocytes play a major role in host defense against tumors and infectious diseases. Previously, we reported that delta-9-tetrahydrocannabinol (THC) and II-hydroxy-delta-9-tetrahydrocannabinol (II-hydroxy-THC) suppressed the cytolytic activity of cultured natural killer (NK) cells. Also, we showed that the drugs appeared to be affecting a stage in the killing process subsequent to the binding of the killer cell to the target cell. In the present report, we have extended these studies to an examination of the effect of cannabinoids on the activity of cytotoxic T lymphocytes (CTLs). The cytolytic activity of CTLs generated by cocultivation with either allospecific stimulators or TNP-modified-self stimulators were suppressed by both THC and II-hydroxy-THC treatment. Allospecific CTLs generated in vivo were also inhibited by an in vitro exposure to either THC or II-hydroxy-THC, and the sensitivity of these cells to drug effects appeared to be greater than the sensitivity of the in vitro generated CTLs. Suppression of cytolytic function by THC and II-hydroxy-THC was maximal after a 4-h drug treatment, suggesting that the drug effects were inducible and therefore required a finite period of time to develop maximally. As seen in previous studies involving NK cells, drug treatment of mature CTLs appears to have little effect on the binding capacity of these cells for the target. However, the maximal killing capacity of the cells and the frequency of CTLs were significantly reduced by drug treatment. In addition to suppressing the cytolytic activity of mature effector CTLs, we also show that drug treatment inhibits both the proliferation of lymphocytes responding to an allogeneic stimulus and the maturation of these lymphocytes to mature CTLs. Similarly, CTL activity developing in vivo could be inhibited by THC injection. These results suggest that CTLs are inhibited by cannabinoids by at least two mechanisms. First, the cytolytic activity of mature killers is suppressed at some point beyond the binding to the target cell. Second, the cannabinoids appear to suppress the normal development of these mature effector cells from less mature precursor cells.  相似文献   
9.
10.
Humoral hypercalcemia of malignancy (HHM) in neoplastic syndrome has been most commonly reported in squamous cell carcinoma. Gallbladder carcinoma with HHM is uncommon. In this report, we describe a male case of gallbladder carcinoma with marked hypercalcemia and a high level of serum parathyroid hormone-related peptide (PTHrP). An immunohistochemical examination using PTHrP was also positive.  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