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   46340篇
  免费   4118篇
  国内免费   93篇
耳鼻咽喉   367篇
儿科学   1959篇
妇产科学   1333篇
基础医学   6341篇
口腔科学   672篇
临床医学   5570篇
内科学   8550篇
皮肤病学   769篇
神经病学   5367篇
特种医学   973篇
外科学   4858篇
综合类   666篇
现状与发展   1篇
一般理论   81篇
预防医学   6143篇
眼科学   864篇
药学   3008篇
中国医学   37篇
肿瘤学   2992篇
  2023年   612篇
  2022年   988篇
  2021年   2068篇
  2020年   1250篇
  2019年   1811篇
  2018年   2024篇
  2017年   1393篇
  2016年   1542篇
  2015年   1622篇
  2014年   2136篇
  2013年   2763篇
  2012年   3931篇
  2011年   3840篇
  2010年   1937篇
  2009年   1685篇
  2008年   2628篇
  2007年   2730篇
  2006年   2371篇
  2005年   2188篇
  2004年   1913篇
  2003年   1565篇
  2002年   1465篇
  2001年   424篇
  2000年   379篇
  1999年   426篇
  1998年   319篇
  1997年   222篇
  1996年   201篇
  1995年   189篇
  1994年   180篇
  1993年   166篇
  1992年   258篇
  1991年   225篇
  1990年   244篇
  1989年   229篇
  1988年   213篇
  1987年   170篇
  1986年   178篇
  1985年   190篇
  1984年   142篇
  1983年   132篇
  1982年   100篇
  1981年   86篇
  1980年   80篇
  1979年   132篇
  1978年   111篇
  1977年   88篇
  1973年   100篇
  1972年   99篇
  1971年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Background: Numerous investigators have attempted to identify prognostic indicators for successful outcome following bariatric surgery. The purpose of this study was to determine whether degree of obesity affects outcome in super obese [>225% ideal body weight (IBW)] versus morbidly obese patients (160-225% IBW) undergoing gastric restrictive/bypass procedures. Methods: Since 1984, 157 patients underwent either gastric bypass or vertical banded gastroplasty. Super obese (78) and morbidly obese (79) patients were followed prospectively, documenting outcome and complications. Results: Super obese patients reached maximum weight loss 3 years following bariatric surgery, exhibiting a decrease in body mass index (BMI) from 61 to 39 kg/m2 and an average loss of 42% excess body weight (EBW). Morbidly obese patients had a decrease in BMI from 44 to 31 kg/m2 and carried 39% EBW at 1 year. After their respective nadirs, each group began to regain the lost weight with the super obese exhibiting a current BMI of 45 kg/m2 (61% EBW) versus 34 kg/m2 (52% EBW) in the morbidly obese at 72 months cumulative follow-up. Currently, loss of 50% or more of EBW occurred in 53% of super obese patients versus 72% of morbidly obese (P < 0.01). Twenty-six percent of super obese patients returned to within 50% of ideal body weight (IBW) while 71% of morbidly obese were able to reach this goal (P < 0.01). Co-morbidities and complications related to surgery were similar in each group. Conclusions: Super obese patients have a greater absolute weight loss after bariatric surgery than do morbidly obese patients. Using commonly utilized measures of success based on weight, morbidly obese patients tend to have better outcomes following bariatric surgery.  相似文献   
102.
The rare combination of spinal and intracranial meningeal hemangiopericytomas in the same patient is reported. The coexistence of cerebral and spinal meningiomas of all histological subtypes is distinctly uncommon with only nine cases found in the literature.  相似文献   
103.
104.
Osteocalcin and matrix Gla protein (MGP) are two vitamin K-dependent proteins present in bone and cartilage. Transgenic mice models were recently developed to isolate the function of each of these proteins. While osteocalcin-deficient mice have increased bone formation, MGP-deficient mice have abnormal calcification leading to osteopenia, fractures, and premature death owing to arterial calcification.  相似文献   
105.
106.
Primary dystonia is a disorder of movement for which no consistent pathophysiology has been identified; in the absence of evidence to the contrary, it is assumed to be cognitively benign. We have studied a clinically heterogeneous group of 14 patients with primary dystonia on a battery of neuropsychological tests. Despite well-preserved speed of information processing, language, spatial, memory and general intellectual skills relative to normal controls, we have identified a constellation of attentional-executive cognitive deficits on the Cambridge Neuropsychological Test Automated Battery (CANTAB). Specifically, patients demonstrated significant difficulties negotiating the extra-dimensional set-shifting phase of the IED task. The implications of these findings for the pathophysiology of primary dystonia are discussed. This is, to the best of our knowledge, the first report of a significant cognitive deficit in patients with primary dystonia.  相似文献   
107.
The opioid transmitters enkephalin and dynorphin are known to regulate pallidal output and consequently cortical excitability. Indeed, abnormal basal ganglia opioid transmission has been reported in several involuntary movement disorders, including levodopa-induced dyskinesias in Parkinson's disease (PD), tardive dyskinesias/dystonia, Huntington's disease, and Tourette's syndrome. Moreover, a previous 11C-diprenorphine PET study investigating levodopa-induced dyskinesias found reduced opioid receptor availability in PD with but not without dyskinesias. We wished to investigate if a similar alteration in basal ganglia opioid binding was present in DYT1 primary torsion dystonia (PTD). Regional cerebral 11C-diprenorphine binding was investigated in 7 manifesting carriers of the DYT1 gene and 15 age-matched normal controls using a region-of-interest (ROI) approach and statistical parametric mapping (SPM). No difference in regional mean 11C-diprenorphine binding was found between DYT1-PTD and controls, and no correlation between the severity of dystonia and opioid binding was seen. We conclude that aberrant opioid transmission is unlikely to be present in DYT1-PTD and altered opioid transmission is not a common mechanism underlying all disorders of involuntary movement.  相似文献   
108.
In the last century, both the health and life expectancy of Americans improved dramatically. These gains were primarily the result of advances in public health. But the approaches used may not be adequate to achieve the next level of improvements in health. Because health exists in the context of social, environmental, community, religious, political, and other spheres, ecological approaches that incorporate behavioral and social science theory and methodologies may provide the best avenue for advancing health in the 21st century. In 1999, the New York City Department of Health (NYCDOH) undertook the task of integrating behavioral and social science into its public health practice. The experience serves as a case study on the integration process at a public health agency.  相似文献   
109.
The effect of intraarticular infusions of albumin solution on transsynovial flow was studied in healthy rabbit knee joints and compared with the effect of albumin solution perfused through the synovial microcirculation. Increasing intravascular albumin levels enhanced fluid absorption from the joint cavity, whereas increasing intraarticular albumin levels reduced the absorption rate. The slope of intraarticular pressure-versus-absorption rate plots was reduced by albumin in proportion to the reduction in fluidity (1/viscosity). When joint pressure was held constant, the transsynovial absorption rate was reduced by albumin in excess of the fluidity reduction and even reversed to filtration into the joint cavity. Thus intraarticular albumin acts by a dual mechanism, namely by increasing synovial interstitial fluid viscosity and by exerting a peri-capillary oncotic pressure. However, the latter effect was much less than that of intravascular albumin. Reasons for this are discussed.  相似文献   
110.
PURPOSE: Perillyl alcohol (POH) displays preventive and therapeutic activity against a wide variety of tumor models, and it has been suggested that this might be associated with the ability of POH to interfere with Ras prenylation. POH also selectively induces G(1) arrest and apoptosis in Bcr/Abl-transformed hematopoietic cells. Because signaling through Ras is necessary for Bcr/Abl transformation, we examined whether POH induces its anti-leukemia effect by inhibiting Ras signaling. EXPERIMENTAL DESIGN: The ability of POH to inhibit posttranslational farnesylation and signaling from Ras as well as signaling through the Raf-Mek-Erk cascade was examined in Bcr/Abl-transformed and mock-transformed cells and related to the anti-leukemia effect of POH. RESULTS: POH does not affect Ras prenylation or Ras activity, but it blocks signaling downstream of Ras by reversing the state of activation of the Erk kinase, Mek. POH affects Mek activity only when it is added to intact cells. Treatment of either cell lysates or of purified Mek with POH has no effect on Mek activity. Inhibition of the Mek-Erk pathway seems to be related to the POH anti-leukemia effect for the following reasons: (a) the concentration of POH needed to block the Erk pathway, as well the kinetics with which POH inhibits this signaling cascade, both correlate with the anti-leukemia effect of POH; (b) both U0126 (a specific Mek inhibitor) and POH induce similar anti-leukemia effects; and (c) mock-transformed hematopoietic cells are simultaneously resistant to POH anti-leukemia effects and inhibition of the Mek-Erk pathway. CONCLUSION: Blocking Mek is sufficient to induce growth arrest and apoptosis in Bcr/Abl-transformed cells; therefore, POH represents a novel small molecule inhibitor of Mek that might be effective for treating Bcr/Abl leukemias.  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