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   2741篇
  免费   126篇
  国内免费   12篇
耳鼻咽喉   20篇
儿科学   87篇
妇产科学   11篇
基础医学   352篇
口腔科学   53篇
临床医学   153篇
内科学   761篇
皮肤病学   25篇
神经病学   234篇
特种医学   81篇
外科学   462篇
综合类   10篇
预防医学   52篇
眼科学   10篇
药学   230篇
中国医学   6篇
肿瘤学   332篇
  2023年   19篇
  2022年   13篇
  2021年   62篇
  2020年   19篇
  2019年   48篇
  2018年   54篇
  2017年   38篇
  2016年   54篇
  2015年   56篇
  2014年   77篇
  2013年   101篇
  2012年   125篇
  2011年   140篇
  2010年   90篇
  2009年   80篇
  2008年   161篇
  2007年   152篇
  2006年   150篇
  2005年   158篇
  2004年   177篇
  2003年   179篇
  2002年   181篇
  2001年   44篇
  2000年   27篇
  1999年   37篇
  1998年   48篇
  1997年   31篇
  1996年   34篇
  1995年   22篇
  1994年   58篇
  1993年   53篇
  1992年   46篇
  1991年   29篇
  1990年   32篇
  1989年   28篇
  1988年   29篇
  1987年   26篇
  1986年   21篇
  1985年   18篇
  1984年   14篇
  1983年   9篇
  1982年   19篇
  1981年   15篇
  1980年   20篇
  1979年   10篇
  1977年   10篇
  1976年   10篇
  1973年   8篇
  1972年   6篇
  1969年   8篇
排序方式: 共有2879条查询结果,搜索用时 281 毫秒
61.
Malignant neoplasms rarely extend into the inferior vena cava and up to the right side of the heart. Although massive pulmonary tumor embolism occurs relatively rarely, it can be a catastrophic problem. Intraoperative pulmonary tumor embolism and cardiac arrest occurred in a 68-year-old woman while dissecting the inferior vena cava to resect a pararenal tumor extending into the retrohepatic inferior vena cava. Abrupt arterial hypotension, tachycardia, and increased central venous pressure lead to the diagnosis of massive pulmonary tumor embolism. Emergency cardiopulmonary bypass was commenced under profound hypothermia and cardiac arrest. The tumors in the main pulmonary artery were extracted, and fragments of remnant tumor were retrieved by a vascular endoscope, a Fogarty catheter, and milking of the lung. Following embolectomy, the tumor in the retrohepatic to infrarenal inferior vena cava was removed and the primary tumor together with the infrarenal inferior vena cava was resected under hepatic vascular exclusion and partial cardiopulmonary bypass. The inferior vena cava below the renal veins was not reconstructed. The patient recovered with slight retrograde amnesia. A postoperative pulmonary perfusion scintigram showed no defect in the pulmonary circulation. She is well now 8 months after surgery. Safe prevention measures should be accomplished as a part of the perioperative management of patients with inferior vena cava tumor thrombus that may be fragile, and cardiopulmonary bypass should always be stand-by on surgery.  相似文献   
62.
ObjectivesSialolipoma has been classified as a benign soft tissue lesion in the 2017 World Health Organization classification of head and neck tumors. To our knowledge, only one case of laryngeal sialolipoma has been reported in the English literature. We conducted a retrospective study to identify clinical characteristics of supraglottic sialolipoma-like lesion and differentiate it from other supraglottic subepithelial masses.MethodsMedical records of 16 patients with supraglottic subepithelial benign mass lesions who underwent histological evaluation between 2003 and 2019 were retrospectively analyzed. Sialolipoma-like lesion was defined as a local finding of a well-circumscribed gross mass with pathological presence of salivary gland-like parenchymal lobules with evenly interspersed adipose tissue.ResultsEight patients showed histological positivity for sialolipoma-like lesion, 3 for amyloidosis, 2 for hemangioma, and 1 each for cyst, lymphoid hyperplasia, and chondrometaplasia. Sialolipoma-like lesion tended to be predominant among men; those affected had a mean age of 52.8 (range, 39–74) years. By contrast, among patients with amyloidosis, the ratio of men to women was 1:2 (100% vs. 33%; p = 0.055). Fiberscopic examination of all patients with sialolipoma-like lesions identified well-circumscribed, yellowish masses, closely resembling local amyloidosis findings. Sialolipoma-like lesion was associated with a significantly higher body-mass index (BMI; 27.4 ± 2.8 kg/m2) than amyloidosis (21.6 ± 1.4 kg/m2; p = 0.014). The transoral approach was used for lesion resection in all patients with sialolipoma-like lesion. No patient experienced postoperative recurrence.ConclusionLaryngeal sialolipoma-like lesion might be more prevalent than was previously reported, and histological examination is important to differentiate it from amyloidosis. Supraglottic sialolipoma-like lesion must be differentially diagnosed in patients with high BMI presenting with well-circumscribed, yellowish supraglottic masses.  相似文献   
63.
64.
BACKGROUND: Endoscopic submucosal dissection (ESD) enables direct submucosal dissection so even large early stage GI tumors can be resected en bloc. Colorectal ESD is technically more difficult, however, and there is an increased risk of complications such as perforation and bleeding compared with gastric ESD. As a result, further refinements are required in this procedure. OBJECTIVE: Our purpose was to evaluate thin endoscope-assisted (TEA) ESD, a new traction system for improving submucosal cutting line visualization. DESIGN: Case series. SETTING: Okayama University Hospital. MAIN OUTCOME MEASUREMENTS: Efficacy and safety of the TEA-ESD procedure. RESULTS: Three cases of large, flat, elevated colorectal tumors (laterally spreading tumors) in the rectum and rectosigmoid colon were safely and successfully removed en bloc without complications. Total procedure times were 3 hours, 40 minutes, and 30 minutes with resected specimens measuring 70 x 68 mm, 38 x 35 mm, and 30 x 20 mm, respectively. LIMITATIONS: TEA-ESD was performed in only the rectum and rectosigmoid colon. CONCLUSIONS: This limited case series demonstrated that large laterally spreading tumors in the rectum and rectosigmoid colon could be safely resected en bloc with TEA-ESD.  相似文献   
65.
66.
The subsets of tumor-infiltrating lymphocytes (TIL) and prostaglandin (PG) E 2 were measured in the resected tissues of 32 colorectal cancers without metastasis and 14 with metastasis in order to investigate the local immunity in metastasis of colorectal carcinoma. Subsets of TIL (Leu 1, Leu 2a, Leu 3a, Leu 10, Leu 1 1b, IL-2 receptor) were detected by immunohistochemical staining of frozen tissues. The number of positive cells was counted and expressed as number positive per 250 × 250 m 2.The numbers of T cells (Leu 1) and natural killer cells (Leu 11b) were larger in early cancers and decreased in parallel with the presence of metastasis (control [n=9]: 89±28, 6±4; early cancers [n=9]: 269±112 *,76±56 *;advanced cancers without metastasis [n=11]: 182±80 *,56±59 *;advanced cancers with metastasis [n=11]: 76±42 *,26±21; values are mean ± SD; * P < 0.05, ANOVA). The level of PG E 2 from the draining vein (V) measured by radioimmunoassay was higher than that from the feeding artery (A) (119.1±14.3 vs. 15.4±1.9 pg/ml; P <0.001). The PG E 2 V/A ratio of cancers with metastasis was significantly higher than that of those without metastasis (132±2.4 vs. 5.6 ±0.8; P <0.001). TIL was decreased in parallel with the increase of PG E 2 V/A ratio. We conclude that TIL and PG E 2 may play an important role in metastasis of colorectal carcinoma and that PG E 2 has an adverse effect in suppressing local immunity and enhancing metastasis.Supported by grants from the Japanese Ministry of Science, Education, and Culture (60570619 and 63480299).Read at the meeting of The American Society of Colon and Rectal Surgeon, Boston, Massachusetts, May 12 to 17, 1991.  相似文献   
67.
OBJECTIVE: Transplantation of hematopoietic stem cells (HSCs) is usually accomplished through intravenous injection, a complex process that requires recognition of bone marrow vasculature and migration to a supportive microenvironment. Hence, some populations of HSCs, including cord blood (CB) Lin(-)CD34(-) stem cells, do not engraft well in bone marrow (BM) of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. In this study, we examined the effect of human stromal interactions on the properties of CB Lin(-)CD34(-) cells. MATERIALS AND METHODS: CD34 and CXCR4 expression on fresh CB Lin(-)CD34(-) cells and CB Lin(-)CD34(-) cells cocultured with human stromal cells were analyzed. Homing activity and engraftment of these cells were assessed using NOD/SCID mice. In an attempt to identify the stromal CXCR4-inducing factor, CB Lin(-)CD34(-) cells were cocultured with a noncontact culture system in the presence of several inhibitors. RESULT: Coculture with human stromal cells induced expression of CD34 and CXCR4 on CB Lin(-)CD34(-) cells. CXCR4 expression on CB Lin(-)CD34(-) cells was induced even in the noncontact culture condition, suggesting that this CXCR4-inducing factor is soluble. Moreover, CXCR4 induction was inhibited by the soluble Wnt inhibitor DKK1. Furthermore, these cells acquired homing activity and engrafted in the BM of NOD/SCID mice after intravenous injection. CONCLUSION: These findings may be useful for understanding the role of stromal cells in homing and engraftment of HSCs.  相似文献   
68.
Drug‐induced lung injury is an adverse effect of drug treatment that can result in respiratory failure. Because lipid profiling could provide cutting‐edge understanding of the pathophysiology of toxicological responses, we performed lipidomic analyses of drug‐induced lung injury. We used a mouse model of bleomycin‐induced lung injury and followed the physiological responses at the acute inflammatory (day 2), inflammatory‐to‐fibrosis (day 7) and fibrosis (day 21) phases. The overall lipid profiles of plasma, lung and bronchoalveolar lavage fluid (BALF) revealed that drastic changes in lipids occurred in the lung and BALF, but not in the plasma, after 7 and 21 days of bleomycin treatment. In the lung, the levels of ether‐type phosphatidylethanolamines decreased, while those of phosphatidylcholines, bismonophosphatidic acids and cholesterol esters increased on days 7 and 21. In BALF, the global lipid levels increased on days 7 and 21, but only those of some lipids, such as phosphatidylglycerols/bismonophosphatidic acids and phosphatidylinositols, increased from day 2. The lung levels of prostaglandins, such as prostaglandin D2, were elevated on day 2, and those of 5‐ and 15‐lipoxygenase metabolites of docosahexaenoic acid were elevated on day 7. In BALF, the levels of 12‐lipoxygenase metabolites of polyunsaturated fatty acids were elevated on day 7. Our comprehensive lipidomics approach suggested anti‐inflammatory responses in the inflammatory phase, phospholipidosis and anti‐inflammatory responses in the inflammatory‐to‐fibrosis phase, and increased oxidative stress and/or cell phenotypic transitions in the fibrosis phase. Understanding these molecular changes and potential mechanisms will help develop novel drugs to prevent or treat drug‐induced lung injury.  相似文献   
69.
This study was conducted to examine the post-initiation carcinogenic potential of coated and uncoated titanium dioxide nanoparticles (CTDN and UCTDN) using a mouse medium-term skin carcinogenesis bioassay. For this purpose, 5, 10 and 20 mg/animal doses of CTDN or UCTDN were applied to mouse skin in the post-initiation phase (up to 20 weeks) in a two-stage skin carcinogenesis model using 7 week old CD1 (ICR) female mice. 7,12-dimethylbenz[a]anthracene (DMBA) and 12-o-tetradecanoylphorbol 13-acetate (TPA) were used as the initiator and a positive control promoter, respectively. Pentalan 408 served as a vehicle control. No changes in survival rate, general condition and body weight related to the test materials were observed. On macroscopic observation, 1-2 nodules/group on the skin were observed in each group applied CTDN and UCTDN as well as the control group after DMBA initiation. The nodules were histopathologically diagnosed as squamous cell hyperplasia, sebaceous gland hyperplasia, squamous cell papilloma and keratoacanthoma. CTDN and UCTDN experiments, while enlargement of the mandibular, pancreatic, lumbar region and inguinofemoral lymph nodes, spleen and thymus was observed in mice given 5 and 10 mg but not 20 mg, the lack of dose-dependence suggests no biological significance.In the present study, CTDN and UCTDN applied in post-initiation stages at doses of up to 20 mg/mouse did not increase the development of nodules, and thus it was concluded that titanium dioxide nanoparticles do not possess post-initiation potential for mouse skin carcinogenesis.  相似文献   
70.
In this study, we report poly(1H-thieno[3,4-d]imidazol-2(3H)-one) (pTIO) derivatives for an electrochromic (EC) type e-paper and its novel printing fabrication process. pTIO is a kind of conductive polymer (CP) s which are known as one of the EC materials. The electrochromism of pTIO is unique, because its color in doped state is almost transparent (pale gray). A transparent state is required to show a white color in a see-through view of an EC type e-paper. An electrochromism of CP has a good memory effect which is applicable for e-paper. The corresponding monomers of CP are able to be polymerized with an electrochemical method, which be made good use of for the fabrication process of e-paper. pTIO derivatives are copolymerized with other pi-conjugated X unit, which adjusts the color of electrochromism. Finally, we fabricated a segment matrix EC display using pTIO derivatives by ink-jet printing.  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