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   15171篇
  免费   1335篇
  国内免费   47篇
耳鼻咽喉   181篇
儿科学   535篇
妇产科学   302篇
基础医学   2327篇
口腔科学   361篇
临床医学   1596篇
内科学   3272篇
皮肤病学   274篇
神经病学   1117篇
特种医学   537篇
外国民族医学   1篇
外科学   2154篇
综合类   143篇
现状与发展   20篇
一般理论   8篇
预防医学   1192篇
眼科学   349篇
药学   1168篇
中国医学   16篇
肿瘤学   1000篇
  2023年   119篇
  2022年   116篇
  2021年   240篇
  2020年   216篇
  2019年   254篇
  2018年   319篇
  2017年   308篇
  2016年   338篇
  2015年   316篇
  2014年   436篇
  2013年   586篇
  2012年   714篇
  2011年   683篇
  2010年   434篇
  2009年   429篇
  2008年   593篇
  2007年   624篇
  2006年   573篇
  2005年   544篇
  2004年   614篇
  2003年   506篇
  2002年   493篇
  2001年   437篇
  2000年   471篇
  1999年   423篇
  1998年   209篇
  1997年   172篇
  1996年   201篇
  1995年   170篇
  1994年   155篇
  1993年   155篇
  1992年   311篇
  1991年   342篇
  1990年   339篇
  1989年   351篇
  1988年   276篇
  1987年   289篇
  1986年   247篇
  1985年   300篇
  1984年   195篇
  1983年   169篇
  1982年   134篇
  1981年   105篇
  1980年   94篇
  1979年   166篇
  1978年   134篇
  1977年   114篇
  1975年   102篇
  1974年   117篇
  1973年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Erythropoietic protoporphyria (EPP) is a disease of the heme metabolism due to a deficiency of ferrochelatase, leading to accumulation of protoporphyrin (PPIX) in the erythrocyte (red blood cell [RBC]). The major clinical manifestation in EPP is photosensitivity; however, in a small number of patients liver failure is a significant complication and liver transplantation is the only treatment option. Damage to both abdominal skin and organs occurs when exposed to operating light; however, this problem can be ameliorated by the use of filters that block the transmission of light with wavelength below 470 nm. A more unusual but very serious complication postoperatively is severe motor neuropathy, with few or no known acute available precautions. An effective treatment option is needed to manage EPP crises and to prevent complications after liver transplantation. We successfully treated a patient with EPP-induced liver failure with the molecular adsorbents recirculating system (MARS) and Prometheus in independent sessions. Following treatment with MARS we found a 9.1% reduction of the RBC-PPIX concentration and a 5.9% reduction after treatment with the Prometheus system. Plasmapheresis made a reduction in RBC-PPIX concentration of 0.8%. Following treatment sessions with MARS and Prometheus, the clinical condition was markedly improved and orthotopic liver transplantation was performed without further complications. In conclusion, extracorporeal therapy with MARS or Prometheus seems to be efficient in reducing RBC-PPIX concentration in comparison to plasma exchange.  相似文献   
32.
AIMS: The glutamate decarboxylase gene (GAD2) encodes GAD65, an enzyme catalysing the production of the gamma-aminobutyric acid (GABA) which interacts with neuropeptide Y to stimulate food intake. It has been suggested that in pancreatic islets, GABA serves as a functional regulator of pancreatic hormone release. Conflicting results have been reported concerning the potential impact of GAD2 variation on estimates of energy metabolism. The aim of this study was to elucidate potential associations between the GAD2-243A-->G polymorphism and levels of body mass index (BMI) and estimates of glycaemia. METHODS: Using high-throughput chip-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, the GAD2-243A-->G (rs2236418) polymorphism was genotyped in a population-based sample (Inter99) of 5857 middle-aged, unrelated Danish White subjects. RESULTS: The G-allele was associated with modestly lower BMI (P = 0.01). In a case-control study of obesity, the G-allele frequency in 2582 participants with BMI < 25 kg/m2 was 19.5% (18.4-20.6) compared with 17.1% (15.5-18.8) in 968 participants having BMI > or = 30 kg/m2 (P = 0.03), odds ratio 0.9 (0.7-1.0). Of the 5857 subjects, GG carriers had lower fasting plasma glucose levels (mmol/l) [AA (n = 3859) 5.6 +/- 0.8; AG (n = 1792) 5.5 +/- 0.8; GG (n = 206) 5.5 +/- 0.8, P = 0.008] and lower 30-min oral glucose tolerance test (OGTT)-related plasma glucose levels (AA 8.7 +/- 1.9; AG 8.6 +/- 1.9; GG 8.6 +/- 2.0, P = 0.04), adjusted for sex, age and BMI. Analysing subjects who were both normoglycaemic and glucose tolerant (n = 4431) GG carriers still had lower fasting plasma glucose concentrations: AA (n = 2895) 5.3 +/- 0.4; AG (n = 1383) 5.3 +/- 0.4; GG (n = 153) 5.2 +/- 0.4 (P = 9.10(-5)). CONCLUSION: The present study suggests that the GAD2-243A-->G polymorphism in a population of middle-aged White people associates with a modest reduction in BMI and fasting and OGTT-related plasma glucose levels.  相似文献   
33.
Conclusion  The ACCF/ASNC AC for SPECT MPI provides recommendations for the appropriate use of SPECT MPI. After the publication of the AC document in 2005, the AC has been used by nuclear cardiology practices with many clinical studies evaluating the list of indications in routine clinical practice. From these data. ASNC recommends minor but important changes to the indication list, suggesting the addition of 6 new indications and the modification of the definitions for “chest pain syndrome” and “CHD high risk.”. An objective review of existing indications focused on only those indications that had significant variability among the reviewers (n=20). These indications were reviewed in the presence of existing and new evidence-based data, and ASNC recommends that the grades for 6 indications be re-evaluated. The AC for SPECT MPI will require periodic review as new evidence becomes available or as clinical practice evolves. ASNC recognizes the importance of these criteria to improve the quality of patient care, and it will continue to play a key role in assembling the information for this ongoing review. From the current summary of evidence, ASNC consensus opinions, and ASNC recommendations in this document, ASNC strongly recommends that the AC guidelines be reviewed Prepared by the American Society of Nuclear Cardiology Quality Assurance Subcommittee for Quality in Imaging Standards. Reviewed by members of the American Society of Nuclear Cardiology Quality Assurance Committee. Approved by the American Society of Nuclear Cardiology Board of Directors, September 6, 20.  相似文献   
34.
BACKGROUND:: During the 1980s reports describing the effect of systemic chemotherapyon brain metastases from chemosensitive tumours emerged, includinga few retrospective reports on small cell lung cancer (SCLC)patients. DESIGN:: Previously untreated SCLC patients with no other malignancy,but in some cases with mixed histological subtype, who had symptomaticbrain metastases verified by contrast enhanced CT-scan, weretreated with a multidrug combination chemotherapy regimen andno cranial irradiation. Radiotherapy was optional at cranialrelapse or progression at the discretion of the physician incharge. The intracranial effect was evaluated by 4-weekly CT-scanand neurological examination, according to a standardized scoringsystem. END POINTS:: Intracranial response, duration of response, neurological score,terminal CNS status, and survival. RESULTS:: 21 patients were included, corresponding to 8.6% of consecutiveSCLC patients at our institution. 8 patients died before follow-upleaving 13 evaluable for response. In the former group, allpatients had WHO performance status of 3–4 compared to6/13 in the latter group. Of the 13 evaluable patients, 1 hadearly progression in the CNS and 1 had no change. 11 had CT-scanverified response, with a median duration of 135 days. Mostpatients, including all complete responders, had improvementin their neurological score. 6 out of 11 responders died withoutactive CNS disease. The crude median survival was 111 days,whereas the median survival(early deaths excluded) was 197 days. CONCLUSION:: Systemic combination chemotherapy was effective for palliationof initial brain involvement in the majority of patients ina small consecutive series. The role of consolidating cranialirradiation in responders should be assessed by a randomizedtrial. small cell carcinoma, brain metastases, chemotherapy  相似文献   
35.
Summary Tibial hypo-/aplasia with preaxial syn- and polydactyly is a rare autosomal dominant condition. Fewer than 20 cases have so far been described. One is presented here.  相似文献   
36.
In this paper we propose a method for construction of feed-forward neural classifiers based on regularization and adaptive architectures. Using a penalized maximum likelihood scheme, we derive a modified form of the entropic error measure and an algebraic estimate of the test error. In conjunction with optimal brain damage pruning, a test error estimate is used to select the network architecture. The scheme is evaluated on four classification problems.  相似文献   
37.
EMG responses in the external anal sphincter (EAS), the rectus abdominis muscle (RA), and the anterior tibial muscle (TA) were recorded following single magnetic transcranial cortical stimulations (TCCS) in seven healthy volunteers. The responses in the EAS differed from the responses in the other muscles. They had comparatively long durations ranging from 1 to 2 seconds, no inhibitory periods were observed, and there was no tendency for habituation to occur following a limited number of stimuli. The responses recorded in the EAS were used as test responses in order to evaluate the excitability changes in the EAS motoneurons occurring during bladder filling. Cystometries with filling rates of 15, 50 and 200 ml/min were done. During these cystometries TCCS were applied repeatedly, with constant strength, after each 50 ml of filling up to bladder capacity. The responses following TCCS changed in a highly reproducible way during bladder filling. After 100–200 ml of filling, the responses had longer latencies, diminished sizes, and shorter durations. When the filling reached a level 50–150 ml below capacity, the responses in most subjects again became greater and the latencies shorter. The changes were believed to be physiological. It was concluded that the EAS motoneurons are under both inhibitory and facilitatory influence during bladder filling in intact healthy humans. Facilitatory influences are often observed when the bladder is filled close to capacity. At lower bladder volumes the observed influence is always inhibitory. A decrease in the EMG activity of the EAS during filling cystometry should consequently not be regarded as a pathological response.  相似文献   
38.
39.
Intravenously injected polystyrene microspheres with functional amino groups (AP-MSs, 0.2,1.0, and 4.0 urn in diameter) were cleared from the blood very rapidly. The calculated half-lives for 0.2-, 1.0-, and 4.0-μm AP-MSs were about 55,60, and 50s; no significant differences were found with 106,107, and 108 microspheres/rat. Loading experiments showed that the liver, spleen, lung, kidney, and heart had a very high capacity to take up AP-MSs. The AP-MSs were distributed mainly to the liver, lung, and spleen, whereas other organs contained less than 1 % of injected AP-MSs. In terms of numbers of AP-MSs per gram of tissue, the highest contents were found in spleen, liver, and lung for 0.2-, 1.0-, and 4.0-um AP-MSs, respectively. There was indication of redistribution of particles from one organ to another during the first 6 h after injection. Chondroitin sulfate A (Chon) and hyaluronic acid (Hya) adsorbed or covalently linked to AP-MSs increased uptake in the liver, with Chon AP-MSs (adsorbed or linked) showing the best effect: about 25% increase compared with unadsorbed 1-μm AP-MSs. Experiments with separated cells in vitro demonstrated that 1 um AP-MSs, intravenously injected, associated only with Kupffer cells. When the microspheres were adsorbed with Chon, there was also association with liver endothelial cells. This finding indicates that conjugation of microspheres with ligands for endothelial receptors may be a useful method for directing microspheres to specific organs, even if the receptors are not by themselves phagocytic  相似文献   
40.
Synovial fluid (SF) and blood from 24 patients with non-traumatic, sterile hydarthron were examined for monocyte elastolysis (M?E) and for levels of interleukin 6 (IL-6) and of soluble interleukin 2 receptor (sIL-2R). Six patients had osteoarthrosis (OA) and 18 patients had inflammatory hydarthron (IH), 10 of whom had rheumatoid arthritis (RA). Blood M?E was lower in OA than in IH, both measured as basal M?E activity and after in vitro stimulation with immune complexes and phorbol myristate acetate (PMA). SF M?E was higher than M?E in blood (p less than 0.01). This increase in SF M?E could be mimicked in vitro by prestimulation of blood M? with low levels of IC. SF IL-6 and sIL-2R were also elevated (p less than 0.01). All three parameters correlated to the degree of joint inflammation evaluated by SF leucocyte level, complement activation, blood C Reactive Protein, and to the clinical evaluation of the joint. The increase in SF M?E, IL-6 and sIL-2R in patients with IH, points to a stimulation of M? and lymphocytes in the joint.  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