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   36088篇
  免费   1620篇
  国内免费   298篇
耳鼻咽喉   266篇
儿科学   658篇
妇产科学   413篇
基础医学   4786篇
口腔科学   1014篇
临床医学   2110篇
内科学   8969篇
皮肤病学   856篇
神经病学   2454篇
特种医学   1260篇
外科学   6457篇
综合类   146篇
一般理论   1篇
预防医学   991篇
眼科学   635篇
药学   2088篇
中国医学   123篇
肿瘤学   4779篇
  2024年   26篇
  2023年   202篇
  2022年   541篇
  2021年   881篇
  2020年   451篇
  2019年   651篇
  2018年   846篇
  2017年   657篇
  2016年   774篇
  2015年   803篇
  2014年   1077篇
  2013年   1373篇
  2012年   2229篇
  2011年   2611篇
  2010年   1477篇
  2009年   1213篇
  2008年   2236篇
  2007年   2470篇
  2006年   2304篇
  2005年   2482篇
  2004年   2394篇
  2003年   2396篇
  2002年   2405篇
  2001年   361篇
  2000年   308篇
  1999年   430篇
  1998年   576篇
  1997年   455篇
  1996年   431篇
  1995年   372篇
  1994年   323篇
  1993年   297篇
  1992年   209篇
  1991年   189篇
  1990年   183篇
  1989年   168篇
  1988年   145篇
  1987年   110篇
  1986年   103篇
  1985年   90篇
  1984年   107篇
  1983年   85篇
  1982年   72篇
  1981年   87篇
  1980年   82篇
  1979年   60篇
  1978年   44篇
  1977年   29篇
  1976年   25篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
During the last 10 years, we have demonstrated morphological and biochemical abnormalities of skin extracellular matrices in amyotrophic lateral sclerosis (ALS). However, currently little is known concerning collagen of the spinal cord in ALS. We measured the amount of collagen and characterized collagen at light and electron microscopic levels in posterior funiculus, posterior half of lateral funiculus and anterior horn of cervical enlargement of the spinal cord obtained from ten patients with ALS, 11 patients with other neurologic diseases (control group A), and ten patients without neurologic ones (control group B). In posterior half of lateral funiculus and anterior horn, (1) by light microscopy, there was no significant difference in vessel wall area between ALS patients and control groups A and B; (2) ultrastructurally, collagen bundles were more fragmented and widely separated, and the fibrils were randomly oriented in the perivascular space of capillaries in ALS patients, which were not observed in any areas of control groups or in posterior funiculus of ALS patients; and (3) the collagen contents in ALS were significantly lower (P<0.001 and P<0.001, respectively) than those in control groups A and B. Fragmented and widely separated collagen bundles in the interstitial tissue surrounding capillaries and markedly decreased amount of collagen in posterior half of lateral funiculus and in anterior horn of ALS could be related to the degeneration of the upper and lower motor neurons in the spinal cord in ALS, that is, selective neuronal vulnerability in ALS.  相似文献   
102.
103.
104.
105.
We report herein the case of a 56-year-old woman who developed secondary Kwashiorkor 9 years after undergoing a total gastrectomy for early gastric cancer. Until she began developing the symptoms of Kwashiorkor, including general fatigue, edema of the face and extremities, anemia, alopecia, and weight loss, she had been leading a normal life post-gastrectomy. Her symptoms were alleviated by total parenteral nutrition (TPN) therapy, but reappeared soon after TPN therapy was discontinued. Therefore, she required several subsequent courses of TPN. In an attempt to permanently resolve the ongoing Kwashiorkor symptoms, reconstructive surgery involving transposition of the jejunum from the previous Graham method to the interposition method was performed 10 years after the initial gastrectomy. After the second operation, her malnutrition was completely alleviated, and she has been in good health for the 8 years since. To our knowledge, there has been no other report of the symptoms of secondary Kwashiorkor after total gastrectomy being alleviated by altering the procedure of reconstruction of the intestinal tract. Thus, we recommend surgical treatment to alter the digestive continuity to a more physiological pathway for selected patients with secondary Kwashiorkor syndrome.  相似文献   
106.
We report here on the ionic mechanisms underlying the depolarizing afterpotential (DAP) in neocortical pyramidal cells, with special interest in those underlying the burst afterdischarge. Injections of short depolarizing current pulses under whole-cell current clamp with a CsCl-based internal medium generated, in most pyramidal cells, a single action potential with a plateau phase (plateau-AP), followed by a slowly decaying DAP both in the absence and presence of TTX. Under voltage-clamp, the same cells displayed a slow tail current (tail-I) at the offset of depolarization. When intracellular free Ca2+ was chelated with 10 mm BAPTA or when extracellular Ca2+ was replaced with equimolar Ba2+, neither the slow DAP nor the slow tail-I was observed. Extracellular application of Co2+ or Cd2+ reduced Ca2+ currents and the slow tail-I. Cation substitution experiments revealed that the channel generating the slow tail-I was permeable to K+ and Cs+ more than to Na+ (PKPCs > PNa > PNMDGPTEA). The cationic slow tail-I was not reduced by applying antagonists of the metabotropic glutamate receptor (MCPG, 1 mm ) and the muscarinic receptor (atropine, 1–10 μm ). Thus, the slow DAP was produced by activation of the cationic channel whose gating is solely dependent on [Ca2+]i. An increase in [K+]o from 3 to 6 or 9 mm enhanced the slow DAP, and resulted in a generation of burst afterdischarges. An anticonvulsant, phenytoin (PT; 1–10 μm ) suppressed the slow DAP while enhancing the plateau-AP in the presence of TTX, most likely by blocking the cationic channel.  相似文献   
107.
The effects of glucocorticoids on the proportion of lymphocytes in bronchoalveolar lavage (BAL) fluid in relation to humoral and cellular immunity were studied in 56 patients with steroid-dependent intractable asthma. To analyze the mechanism responsible for reduced numbers of BAL lymphocytes, we divided the subjects into 4 groups according to their BAL lymphocyte proportions: 0—4.9%, 5.0-9.9%, 10.0-14.9%, and 15.0-20.0%. Serum IgG levels and the peripheral lymphocyte count were significantly reduced in patients with a low proportion of BAL lymphocytes (less than 9.9%) than in those with more than 10% BAL lymphocytes. Delayed cutaneous reactivity to purified protein derivative was suppressed in patients with a low proportion of BAL lymphocytes (less than 4.9%). The mean proportion of BAL neutrophils tended to increase as the proportion of BAL lymphocytes decreased. These results show that the reduction in BAL lymphocytes produced by glucocorticoids is associated with suppressed humoral and cellular immunity, and that under such conditions the proportion of BAL neutrophils increases.  相似文献   
108.
The effects of calcium (Ca) on a hyperkalemic cardioplegic solution for continuous cardioplegia were examined in an isolated perfused working rat heart model. The coronary arteries were perfused with a modified Krebs-Henseleit bicarbonate buffer (K-H) solution, containing various concentrations of Ca(0.1, 0.6, 1.2, and 2.5 mmol/l) and a high concentration of potassium (20 mmol/l), for 180 min, after which cardiac arrest was induced at 37°C for 180 min. Cardiac function and creatine kinase (CK) were measured. In the control group, K-H solution was infused in place of the cardioplegic solution, and cardiac arrest was not induced. No significant differences were observed between the groups infused with the K-H solution containing Ca concentrations of 0.6, 1.2, and 2.5 mmol/l in the percent recovery of aortic flow (82.1±2.9%, 80.6±2.0%, and 71.5±3.7% (mean±SEM) respectively) or in the recovery of other indices of cardiac function, or in CK leakage. There were also no significant differences in the recovery of cardiac function and CK leakage between these groups and the control group. In the Ca 0.1 mmol/l group, however, the characteristic Ca paradox was observed. These findings suggest that if the Ca concentration in a cardioplegic solution is higher than 0.6 mmol/l during continuous cardioplegia, excellent cardioprotective effects will be achieved.  相似文献   
109.
In this study, we clinically and radiographically evaluated open reduction with shortening of the femur in children more than 1 year old with refractory congenital dislocation of the hip. In 19 children (aged 1–4 years), 22 joints were operated on. The patients were followed-up for an average of 8.7 years (range, 2–13 years). Functional results were satisfactory in all joints, and differences in limb length were not significant. Radiographically, good results (grades I and II) were obtained in 16 of the 22 joints, according to Severin's criteria. This surgical procedure may be indispensable for treating refractory congenital dislocation of the hip in children over 1 year old. Received for publication on May 2, 1997; accepted June 3, 1998  相似文献   
110.
The effects of long-term glucocorticoid therapy on airway inflammation were examined in 84 asthma patients. The proportion of lymphocytes in bronchoalveolar lavage (BAL) fluid was significantly decreased in patients with steroid-dependent intractable asthma (SDIA) compared to results in non-SDIA patients, while BAL neutrophils were significantly increased in SDIA patients compared to results in non-SDIA patients. Regarding age, in patients under the age of 69 (except those between 30 and 39), BAL lymphocyte number was significantly decreased in SDIA compared with non-SDIA subjects, and in patients between 50 and 69, BAL neutrophils were significantly increased in SDIA compared with non-SDIA subjects. The number of BAL lymphocytes was significantly lower in patients with serum cortisol levels of less than 5.0 μg/dl than in those with levels of more than 5.1 μg/dl. BAL lymphocyte number was also significantly lower in patients who had received glucocorticoid therapy for more than 6 years than in those who had received such therapy for 2 years. These results show that long-term glucocorticoid therapy decreases the number of lymphocytes and increases neutrophil numbers in the airways.  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