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   10422篇
  免费   444篇
  国内免费   76篇
耳鼻咽喉   71篇
儿科学   169篇
妇产科学   91篇
基础医学   1244篇
口腔科学   152篇
临床医学   750篇
内科学   2748篇
皮肤病学   231篇
神经病学   656篇
特种医学   570篇
外科学   1849篇
综合类   27篇
预防医学   284篇
眼科学   116篇
药学   731篇
  1篇
中国医学   42篇
肿瘤学   1210篇
  2024年   26篇
  2023年   81篇
  2022年   138篇
  2021年   239篇
  2020年   125篇
  2019年   185篇
  2018年   184篇
  2017年   163篇
  2016年   208篇
  2015年   206篇
  2014年   283篇
  2013年   317篇
  2012年   517篇
  2011年   566篇
  2010年   312篇
  2009年   273篇
  2008年   447篇
  2007年   516篇
  2006年   513篇
  2005年   577篇
  2004年   625篇
  2003年   605篇
  2002年   569篇
  2001年   346篇
  2000年   359篇
  1999年   342篇
  1998年   132篇
  1997年   109篇
  1996年   90篇
  1995年   65篇
  1994年   67篇
  1993年   78篇
  1992年   160篇
  1991年   149篇
  1990年   161篇
  1989年   133篇
  1988年   133篇
  1987年   118篇
  1986年   113篇
  1985年   109篇
  1984年   62篇
  1983年   80篇
  1982年   28篇
  1981年   27篇
  1979年   59篇
  1978年   35篇
  1975年   36篇
  1974年   27篇
  1971年   23篇
  1970年   33篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
BACKGROUND: Major and minor depressive episodes in cancer patients are frequent and are frequently seen as the first depressive episode in a patient's life. However, the neurological basis of these depressive episodes remains largely unknown. METHODS: Subjects were 51 breast cancer survivors (BCS) who had no history of any depressive episode before the cancer diagnosis (11 BCS with a history of a first minor depressive episode after cancer diagnosis, 11 BCS with a history of a first major depressive episode after cancer diagnosis, and 29 BCS with no history of any depressive episode after cancer diagnosis). We analyzed the prefrontal cortex (PFC) and amygdala volumes in a 1.5-Tesla Magnetic Resonance Imaging scanner. We characterized the structural correlates of depression using two complementary approaches. The first was voxel-based morphometry (VBM) that allowed us to scan the entire brain for reactive gray matter deficit. The second was classical volumetry focusing on the amygdala. RESULTS: Voxel-based morphometry revealed no brain region, including PFC, for which volume was significantly different among the three groups. There were trend-level differences in the left amygdala volume in the manual tracing method among the three groups. The left amygdala volumes in the subjects with a first minor and/or major depressive episode were significantly smaller than in those with no history of any depressive episode. CONCLUSIONS: It might be suggested that amygdala volume was associated with a first minor and/or major depressive episode after cancer diagnosis.  相似文献   
52.
We examined four different learning and memory tasks in rats which had been subjected to left carotid artery ligation followed by 2 h hypoxia (8% oxygen) when they were 7 days old. The examination began on the 4th week after insult and continued to 18 weeks post-insult. Compared with the control group, the hypoxic-ischemic group showed significant learning impairments in choice reaction time tasks relating to the attention process, and in plus-maze tasks and water maze tasks which examine long-term reference memory. In eight-arm radial maze tasks representing both short-term working memory and long-term reference memory, inferiority of the hypoxic-ischemic group was transient. Results of the sensorimotor test were normal in the hypoxic-ischemic group although slight flexion and twisting in the right forelimb was observed in 30% of the hypoxic-ischemic group when suspended by the tail. These abnormalities did not affect the results of learning tests. Findings of the study indicate that left-side brain damage produced by hypoxia-ischemia at 7 days of age resulted in selective and long-lasting learning and memory impairment.  相似文献   
53.
We herein report a 36-year-old man with repeated necrotizing lymphadenitis due to MEFV gene mutations. The patient''s chief complaints were a fever and painful cervical lymphadenopathy. We diagnosed him with necrotizing lymphadenitis based on the pathological findings of the lymph nodes and the exclusion of other differential diseases. The same episode recurred four times. We speculated the involvement of autoinflammatory backgrounds and detected MEFV gene mutations of E148Q (homo), P369S, and R408Q. Considering the elevation of interleukin-18, these mutations probably played roles in the repeated necrotizing lymphadenitis.  相似文献   
54.
Objective Peripherally inserted central catheters (PICCs) are widely used in patients with hematologic malignancies. However, the risks of PICC-related complications during chemotherapy for acute myeloid leukemia (AML) are not fully understood. Methods We conducted a retrospective review of 128 adult patients with AML who received induction therapy by way of PICC insertion between 2012 and 2019. Results The median duration of PICC insertion was 30 days. The incidence rate of catheter-related bloodstream infection (CRBSI) was 2.4% at 30 days, and women were more likely to suffer from CRBSI than men. Local reactions at the insertion site were observed in 56 patients; however, these events did not predict CRBSI. The incidence rates of catheter-related thrombosis (CRT) were 1.6% at 30 days. Obesity put patients at an increased risk for CRT. Unexpected PICC removal occurred in 59 patients, and women were at a higher risk of catheter removal than men. Conclusion Low PICC-related complication rates, possibly associated with high rates of catheter removal, were observed during intensive chemotherapy for AML. Women and obese patients require careful monitoring of their PICC. Procedures to achieve appropriate PICC removal without increasing the complication rate need to be considered.  相似文献   
55.
56.
Objective. Tumor angiogenesis has been shown to play an important role in tumor growth and metastasis. This study examines the prognostic significance of two histological markers of angiogenesis, i.e., vascular cuffing (VC), a bead-like arrangement of microvessels closely surrounding microscopic tumor nests, and microvessel density (MVD), the number of microvessels in a unit area, in cervical squamous cell carcinoma.Methods. One hundred twenty-two specimens from surgically resected uteri with cervical squamous cell carcinoma were histologically reviewed and immunostained for CD34. VC was graded into “none,” “incomplete,” and “complete.” The MVD was determined by counting the microvessels with a light microscope within a ×200 field area where neovascularization occurred most actively. Stromal inflammation was also split into three grades. The relationship of VC or MVD to clinicopathological prognostic factors such as FIGO stage, cervical stromal invasion, lymph–vascular space invasion, pelvic lymph node metastasis, and parametrial invasion was evaluated using univariate and multivariate analyses.Results. The patients with a complete VC pattern showed a significantly worse prognosis compared to those with a pattern graded as either none or incomplete (P < 0.011 and P < 0.0001, respectively). The Cox regression analysis revealed the complete VC pattern, together with parametrial invasion, to be an independent prognostic indicator for overall survival. MVD and the grading of stromal inflammation showed no significant relationship with VC or overall survival.Conclusions. The complete VC pattern may therefore be a useful prognostic indicator in cervical squamous cell carcinoma.  相似文献   
57.
PURPOSE: To characterize thin-section computed tomographic (CT) findings of pathologic subgroups of nonspecific interstitial pneumonia (NIP) in a sizeable number of patients. MATERIALS AND METHODS: The study included 55 cases of pathologically proven NIP. The 55 cases were categorized histologically into four grades: grade 1, interstitial inflammation without fibrosis (n = 6); grade 2, interstitial inflammation predominating over fibrosis (n = 16); grade 3, fibrosis predominating over inflammation (n = 5); and grade 4, fibrosis only (n = 28). Two independent observers evaluated the presence, extent, and distribution of various CT findings. Thin-section CT findings and histologic grades were compared by using the Spearman rank correlation coefficient. Observer agreement was assessed. RESULTS: Areas with ground-glass attenuation and architectural distortion were present in all 55 patients. Traction bronchiectasis and intralobular reticular opacities were seen in 52 and 48 patients, respectively. The extent of traction bronchiectasis (r = 0.68; P <.001) and intralobular reticular opacities (r = 0.35; P <.05) correlated with the histologic grade. Honeycombing was seen in 12 (43%) of 28 patients with grade 4 NIP and in three (11%) of the remaining 27 patients (chi(2) test, P <.001). There was good agreement between the observers for the presence (kappa = 0.7-1.0) and extent (Spearman rank correlation; r = 0.87-0.98; P <.001) of various abnormalities. CONCLUSION: The extent of traction bronchiectasis and intralobular reticulation at thin-section CT correlates with increased fibrosis in NIP. Honeycombing is seen almost exclusively in patients with fibrotic NIP.  相似文献   
58.
From the dried rhizomes of Curcuma comosa cultivating in Thailand, 26 known sesquiterpenes were isolated: zederone, zederone epoxide, furanodienone, isofuranodienone, 1(10)Z,4Z-furanodiene-6-one, glechomanolide, dehydrocurdione, neocurdione, curdione, 7α-hydroxyneocurdione, 7β-hydroxycurdione, germacrone-1(10),4-diepoxide, germacrone, 13-hydroxygermacrone, curzerenone, curcolonol, alismol, alismoxide, zedoarondiol, isozedoarondiol, procurcumenol, isoprocurcumenol, aerugidiol, zedoalactone B, curcumenone, and curcumadione. Their structures were elucidated on the basis of physicochemical evidence. Among them, glechomanolide, curzerenone, curcolonol, alismol, alismoxide, and zedoarondiol showed no significant optical activities, so they may be artifact products during the isolation or drying process.  相似文献   
59.
60.
Theiler’s murine encephalomyelitis viruses (TMEV) are divided into two subgroups on the basis of their different biological activities. The GDVII strain produces acute polioencephalomyelitis in mice, whereas the DA strain produces demyelination with virus persistence in the spinal cord. A comparative study of GDVII and DA strains suggested that low host immune responses are responsible for the development of acute GDVII infection and that the persistence of infected macrophages plays a crucial role in the development of chronic white matter lesions in DA infection. All 78 mice infected with GDVII died or became moribund by day 13, while none of 54 mice infected with DA died. In the acute stage, the distribution of viral antigens in the central nervous system (CNS) tissue was similar in both GDVII and DA infections, although the virus titer was higher in GDVII infection. In DA infection, a substantial number of T cells were recruited to the CNS on day 6 when they were virtually absent in GDVII infection. The titer of neutralizing antibody was already high on day 6 in DA infection but was negligible in GDVII infection. Development of chronic paralytic disease from day 35 of the DA infection was accompanied by focal accumulation of viral antigen-positive macrophages in the spinal white matter. In addition, white matter lesions comparable to those in chronic DA infection were induced in the spinal cord within 7 days after intracerebral injection of DA-infected murine macrophages. Received: 26 June 1995 / Revised, accepted: 27 December 1995  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