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   230728篇
  免费   16229篇
  国内免费   7628篇
耳鼻咽喉   3004篇
儿科学   3444篇
妇产科学   2591篇
基础医学   29613篇
口腔科学   4871篇
临床医学   23256篇
内科学   37200篇
皮肤病学   5063篇
神经病学   15247篇
特种医学   11540篇
外国民族医学   25篇
外科学   28604篇
综合类   21573篇
现状与发展   30篇
一般理论   35篇
预防医学   15842篇
眼科学   5037篇
药学   21964篇
  111篇
中国医学   7629篇
肿瘤学   17906篇
  2024年   393篇
  2023年   1980篇
  2022年   5560篇
  2021年   8518篇
  2020年   5270篇
  2019年   5457篇
  2018年   6335篇
  2017年   5893篇
  2016年   6691篇
  2015年   9758篇
  2014年   12049篇
  2013年   13378篇
  2012年   20033篇
  2011年   20228篇
  2010年   13727篇
  2009年   11767篇
  2008年   14938篇
  2007年   14574篇
  2006年   13135篇
  2005年   11981篇
  2004年   9687篇
  2003年   8762篇
  2002年   7516篇
  2001年   5266篇
  2000年   4495篇
  1999年   3224篇
  1998年   1616篇
  1997年   1391篇
  1996年   988篇
  1995年   883篇
  1994年   752篇
  1993年   561篇
  1992年   945篇
  1991年   863篇
  1990年   760篇
  1989年   655篇
  1988年   542篇
  1987年   534篇
  1986年   401篇
  1985年   405篇
  1984年   307篇
  1983年   216篇
  1982年   158篇
  1981年   187篇
  1980年   149篇
  1979年   234篇
  1978年   181篇
  1976年   139篇
  1975年   136篇
  1974年   151篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Kim YH  Min SJ  Ko MH  Park JW  Jang SH  Lee PK 《Neuroscience letters》2005,382(3):280-285
Previous studies have demonstrated that repetitive transcranial magnetic stimulation (rTMS) could modulate the visuospatial functions. In this study, we investigated the effect of off-line high frequency subthreshold rTMS, when applied over the right or left posterior parietal cortex (PPC), on the visuospatial attention of the bilateral hemispaces. The subjects underwent visuospatial tasks before and immediately after receiving 1000 pulses of 10 Hz rTMS for a period of 20 min, and their responses were recorded. Our results demonstrated that the high frequency rTMS applied over the PPC produced facilitative effects on the visuospatial attention to the contralateral hemispace. The inhibitory effect to the ipsilateral hemispace was noticeable only in the left PPC.  相似文献   
982.
OBJECTIVE: To determine the relation between P53 tumor suppressor RNA expression and human immunodeficiency virus (HIV) disease progression. STUDY DESIGN/METHODS: A quantitative assay of P53 RNA expression was used to analyze a cohort of HIV-negative persons. The assay was then used in longitudinal and cross-sectional studies of HIV slow and rapid progressors. RESULTS: We demonstrate first that P53 expression in peripheral blood mononuclear cells from HIV-1-seronegative persons is minimal. Longitudinal studies in a small cohort of HIV-1-infected slow and rapid progressors reveal that rapid progressors seem to have greater P53 RNA expression over time. This was validated in a cohort of 26 HIV-1-infected persons in whom the expression of P53 RNA was significantly greater in persons with rapid progression of HIV-1 disease. CONCLUSION: These data suggest that P53 RNA expression may play a role in the pathogenesis of HIV-1 disease, though the mechanism of this interaction remains unknown.  相似文献   
983.
984.
One case of arthritis complicating leukemia is described in which leukemic cells were identified in synovial fluid by light microscopy. Although arthritis is a well-known manifestation of leukemia with an incidence of 13.5%, the pathogenesis often is unclear, and the direct demonstration of leukemic cells in synovial fluid has been very uncommon. A 16 year-old male patient was admitted due to left elbow joint pain and swelling. Synovial fluid examination revealed blast cells and this finding has directed to a final diagnosis of acute lymphoblastic leukemia.  相似文献   
985.
Liver microsomal epoxide hydrolase (mEH) is active in the detoxificationof epoxide-containing carcinogens. The effects of thiazole andpyrazine, constituents of tobacco and tobacco smoke as wellas of a variety of foods, on the expression and regulation ofmEH were examined in rats (200 mg/kg body wt/day, i.p., 1/emdash3 days). Immunoblot analyses using rabbit anti-rat mEH antibodyrevealed a significant increase in mEH levels in hepatic microsomesisolated from either thiazole- or pyrazine-treated animals.Another protein (43 kd) cross-reacting with polyclonal mEH antibodywas found to be increased concomitantly following pyrazine treatment.Northern and slot blot analyses showed substantial increasesin mEH mRNA following either thiazole or pyrazine treatment.The level of mEH mRNA increased 17-fold at 24 h following thiazoletreatment, relative to control. Approximately 20- and 16-foldincreases in mEH mRNA were also observed at 48 and 72 h respectivelyfollowing treatment with pyrazine. The level of polymerase chainreaction (PCR)-amplified mEH DNA derived from poly(A)+ RNA wasclearly elevated following either thiazole or pyrazine treatmentrelative to that from untreated animals. Both sense and antisensestrands of PCR-amplified mEH DNA were cloned into an M13mpl9phage vector in order to examine the nucleotide sequences ofPCR-amplified mEH DNA derived from the poly(A)+ RNA isolatedfrom thiazole- or pyrazine-treated animals. Sequence analysesrevealed that the sequence of PCR-amplified DNA from the inducedmRNA was identical to that published for mEH cDNA. Epoxide hydrolaseactivity toward the hydrolysis of 2-cyanoethylene oxide (CEO),the epoxide metabolite of the rat carcinogen acrylonitrile,was not significant in hepatic microsomes from untreated rats,but was substantially induced by treatment with thiazole orpyrazine. Microsomal hydrolysis activity was heat-sensitiveand potently inhibited by l, l, l-trichloropropene-2, 3-oxide,indicating that mEH was the catalyst. The Vmax for the hydrolysisof CEO by hepatic microsomes from thiazole-treated rats (13.4nmol/min/mg protein) was 1.5-fold greater than that with microsomesfrom pyrazine-treated rats, whereas similar Km values ( 1 mM)were observed for both microsomal preparations. These kineticdata correlate well with the increases in mEH mRNA observedafter administration of thiazole or pyrazine to rats. Theseresults provide evidence that administration of thiazole orpyrazine induces mEH with a large increase in mEH mRNA, andthat the induced mEH catalyzes the hydrolysis of CEO.  相似文献   
986.
A huge rectosigmoidal cancer which extended into the urinary bladder in a 64-year-old man is herein described. The tumor occupied the pelvic and lower abdominal cavities, while the rectosigmoid was totally obstructed. No hepatic or pulmonary metastasis was evident. The ventral and flank sides of the peritoneum in the right lower abdomen, right common iliac vessels, bilateral ureters, terminal ileum, cecum, ascending colon, and urinary bladder were all directly invaded by the tumor, but the aorta, sacrum, and lower rectum were free of cancer. Consequently, an anterior pelvic exenteration was carried out along with an ileal conduit and a right hemicolectomy. Immediately after the exenteration, intra-pelvic hyperthermochemotherapy was performed using a 46–47°C perfusate containing 40 g/ml of mitomycin C (MMC) and 200 g/ml of cisplatin (CDDP), for 90 min, in an attempt to prevent any further local recurrence. A right hemicolectomy and a permanent colostomy were done simultaneously with the hyperthermia treatment. After an uneventful postoperative course, the patient was prescribed adjuvant chemotherapy, i.e., two administrations of 17 mg/m2 and 21 mg/m2 of MMC, and ten doses of 710 mg/m2 of 5-fluorouracil (5-FU) followed by five doses of 535 mg/m2 of 5-FU. At the time of this writing, the patient is still alive without recurrence at 21 months after surgery.  相似文献   
987.
Summary The present studies characterize the binding of [14C]citric acid to synthetic hydroxyapatite (HA) crystals. [14C]Citric acid specifically bound to HA and was dependent upon the concentration of HA in the assay. The binding of [14C]citric acid to HA reached equilibrium within 20 min and remained stable for at least 90 min. Dissociation of bound [14C]citric acid was biphasic in nature since both rapid and more slowly reversible binding components were detected. Saturation experiments also indicated that [14C]citric acid labeled two recognition sites with different affinity (KdH=42 nM and KdL=24,000 nM) and density (BmaxH=161 fmol/g HA and BmaxL=8.8 pmol/g HA). Ligand competition experiments revealed that compounds that are known to readily bind bone (e.g., sodium pyrophosphate, methylene diphosphonic acid, etidronate) potently inhibited the binding of [14C]citric acid to HA, whereas compounds known to have poorer affinity for bone (e.g., oxalic acid and GABA) did not. Computer analysis of these inhibition curves revealed specific ligand interactions at two different affinity recognition sites. The present results indicate that [14C]citric acid binds discrete sites on synthetic HA in a fashion consistent with a specific labeling of the bisphosphonate recognition site. Analysis of the binding of [14C]citric acid to HA provides a useful method to further explore the structure activity relationships of novel compounds that have binding affinity for bone.  相似文献   
988.
A developer is about to break ground on a $6.2 million medical office building on land owned by a California hospital. The deal will result in a haven for referral physicians at no cost to the hospital, though it will forgo equity and some management control.  相似文献   
989.
990.
As the population of rural America ages, rural hospitals are seeing opportunities for new revenue in long-term care. To meet those needs, they are turning to tax-exempt revenue bonds, something they rarely used in the past, and private venture capital, an entirely new wrinkle.  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