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   25552篇
  免费   1960篇
  国内免费   85篇
耳鼻咽喉   419篇
儿科学   929篇
妇产科学   398篇
基础医学   2630篇
口腔科学   552篇
临床医学   2288篇
内科学   5621篇
皮肤病学   584篇
神经病学   1361篇
特种医学   1177篇
外国民族医学   1篇
外科学   4811篇
综合类   359篇
一般理论   16篇
预防医学   1286篇
眼科学   956篇
药学   2209篇
中国医学   45篇
肿瘤学   1955篇
  2023年   212篇
  2022年   379篇
  2021年   1056篇
  2020年   509篇
  2019年   865篇
  2018年   1007篇
  2017年   644篇
  2016年   694篇
  2015年   743篇
  2014年   1080篇
  2013年   1254篇
  2012年   1891篇
  2011年   1838篇
  2010年   949篇
  2009年   893篇
  2008年   1396篇
  2007年   1347篇
  2006年   1213篇
  2005年   1053篇
  2004年   963篇
  2003年   830篇
  2002年   713篇
  2001年   627篇
  2000年   598篇
  1999年   530篇
  1998年   176篇
  1997年   155篇
  1996年   162篇
  1995年   153篇
  1994年   123篇
  1993年   110篇
  1992年   304篇
  1991年   306篇
  1990年   267篇
  1989年   226篇
  1988年   224篇
  1987年   232篇
  1986年   204篇
  1985年   193篇
  1984年   125篇
  1983年   138篇
  1982年   94篇
  1981年   77篇
  1980年   69篇
  1979年   135篇
  1978年   78篇
  1977年   73篇
  1975年   66篇
  1974年   72篇
  1973年   91篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
61.
Several potentially irreversible ligands (i.e., wash-resistant binding inhibitors) for the cocaine receptor site on the dopamine transporter, derived from (-)-cocaine or 3 beta-phenyltropan-2 beta-carboxylic acid methyl ester (WIN 35,065-2), were prepared and shown to produce wash-resistant inhibition of [3H]-3 beta-(p-fluorophenyl)tropan-2 beta-carboxylic acid methyl ester ([3H]WIN 35,428) binding. All the compounds prepared had the same absolute configuration as cocaine; they include analogues possessing chemically reactive groups such as the isothiocyanato and bromoacetamido as well as photoactive azido groups. The potentially irreversible ligands, as well as all the intermediates prepared in this study, were evaluated for their ability to inhibit the binding of [3H]WIN 35,428 in coincubation experiments. Of the potentially irreversible ligands, 3 beta-(p-chlorophenyl)tropan-2 beta-carboxylic acid 2-[p-(bromoacetamido)phenyl]ethyl ester (6c) had the highest apparent potency. The potentially irreversible ligands were also preincubated, and inhibition of [3H]WIN 35,428 binding was determined both before and after washing the ligand-exposed tissues. The most effective ligands in this regard were 3 beta-(3-iodo-4-azidophenyl)tropan-2 beta-carboxylic acid methyl ester (5) and 3 beta-(p-chlorophenyl)tropan-2 beta-carboxylic acid 2-(3-iodo-4-azidophenyl)ethyl ester (6d). The structure-activity relationships of these data are discussed.  相似文献   
62.
63.
OBJECTIVE: To evaluate impressions and usage of sinus surgery image-guided surgical (IGS) systems by ENT surgeons in the United States. STUDY DESIGN AND SETTING: A survey was mailed to selected practicing ENT physicians, investigating regional information, practice type, IGS usage patterns, perceived benefits and limitations, and usage of the 61795 surgery code. RESULTS: Seventy-three percent of respondents use IGS. Nonusers respond that it provides no benefit or is too expensive. Eighty percent of respondents replied that IGS may allow for increased safety in certain procedures. Most users attempt reimbursement with the 61795 code. CONCLUSION: IGS usage is increasing but appears to be perceived as expensive and nonbeneficial in certain situations. Most respondents, however, felt that IGS may lead to safer surgery in certain situations, including revision and frontal procedures. Several factors appear to limit routine use including ease of use, technical setup, code reimbursement, and initial purchase costs. SIGNIFICANCE: IGS use appears to be increasing. The most frequent users appear to agree with the previously issued AAO-HNS guidelines regarding appropriate indications. Expanded use may depend on ease of use, reimbursement, and affordability. EBM rating: D-5.  相似文献   
64.
The gold standard for definitive management of symptomatic benign prostatic hypertrophy is transurethral resection of the prostate (TURP). Despite its efficacy, TURP has significant morbidity/mortality concerns such as hemorrhage and transurethral resection syndrome. This is especially worrisome for the medically high-risk patient, but the high rates of retrograde ejaculation found with TURP also pose a problem for young patients. A minimally invasive, outpatient alternative to TURP that has long-term efficacy, low morbidity/mortality, and provides a cost-effective advantage is in high demand. This review article discusses microwave thermotherapy as such an option and reports the long-term experience with the CoreTherm (CoreTherm Operations AB, Sweden) device.  相似文献   
65.
66.
Summary Eight mares were infected with equid herpesvirus-1 subtype 1 isolated from a case of equine paresis. In two mares killed at 4 d.p.i. immunofluorescence showed endothelial cell infection together with thrombosis in the rete arteriosus of the nasal mucosa and also in the spinal cord of one of these mares. Circulating platelet counts in the other six mares fell as early as 2 d.p.i. and remained depressed for seven days. Circulating immune complexes started to appear at 2 d.p.i., reached maximum levels at 10 d.p.i., but were undetectable at 28 d.p.i. Three of the six remaining mares developed varying degrees of inco-ordination at 8 and 9 d.p.i. In the two inco-ordinate mares that were killed at 9 and 10 d.p.i. the haemorrhages in the spinal cord and brain were associated with extensive endothelial cell fluorescence and thrombus formation. Clinical paresis coincided with an increase in circulating complement fixing and neutralising antibodies which in all six mares were higher against the subtype 2 isolate than subtype 1.In five yearlings infected with a subtype 2 isolate of EHV-1 platelet counts remained normal and neither immune complexes nor viraemia, nor inco-ordination were detected.With 8 Figures  相似文献   
67.
Cocaine is a potent dopamine agonist that frequently stimulates the central nervous system and is often manifested by increased psychomotor activity, impulsivity, euphoria, and rapid thoughts. Attention deficit disorder (ADD) and bipolar disorder also present with physical restlessness, racing thoughts, distractibility, and mood instability. Although these three disorders rarely appear in the same individual, they are important differential diagnoses when considering any one illness with the above symptom complexes. We report two cases of cocaine abuse with ADD residual type in patients who were previously diagnosed as having atypical bipolar disorder. The adverse effects were reversed by the dopamine agonist bromocriptine.  相似文献   
68.
The effects of the calcium antagonists verapamil and nifedipine on blood glucose levels, glucose tolerance, insulin secretion during glucose tolerance and hypoglycaemic effect of tolbutamide were studied in normal nondiabetic rabbits. Daily dosage of 40 mg/kg verapamil and 5 mg/kg nifedipine given orally up to 7 days did not affect blood glucose level, glucose tolerance, insulin secretion during glucose tolerance and hypoglycaemic activity of tolbutamide 250 mg/kg p.o.  相似文献   
69.
Because chronic Mycoplasma pneumoniae respiratory infection is hypothesized to play a role in asthma, the potential of M. pneumoniae to establish chronic respiratory infection with associated pulmonary disease was investigated in a murine model. BALB/c mice were intranasally inoculated once with M. pneumoniae and examined at 109, 150, 245, 368, and 530 days postinoculation. M. pneumoniae was detected in bronchoalveolar lavage fluid by culture or PCR in 70 and 22% of mice at 109 and 530 days postinoculation, respectively. Lung histopathology was normal up to 368 days postinoculation. At 530 days, however, 78% of the mice inoculated with M. pneumoniae demonstrated abnormal histopathology characterized by peribronchial and perivascular mononuclear infiltrates. A mean histopathologic score (HPS) at 530 days of 5.1 was significantly greater (P < 0.01) than that for controls (HPS score of 0). Serum anti-M. pneumoniae immunoglobulin G was detectable in all of the mice inoculated with M. pneumoniae and was inversely correlated with HPS (r = -0.95, P = 0.01) at 530 days postinoculation. Unrestrained whole-body plethysmography measurement of enhanced pause revealed significantly elevated airway methacholine reactivity in M. pneumoniae-inoculated mice compared with that in controls at 245 days (P = 0.03) and increased airway obstruction at 530 days (P = 0.01). Murine M. pneumoniae respiratory infection can lead to chronic pulmonary disease characterized by airway hyperreactivity, airway obstruction, and histologic inflammation.  相似文献   
70.
BACKGROUND: Pravastatin and simvastatin prolong survival and reduce transplant-related coronary vasculopathy, although low-density lipoprotein (LDL) lowering with these agents is only modest. The objective of this study was to assess the safety of moderate dose atorvastatin and its efficacy when prior treatment with another statin had failed to lower LDL to < 100 mg/dl. METHODS: Data from 185 patients were retrospectively evaluated for adverse events, duration of exposure (person-days), and the mean atorvastatin dose exposure. Changes in lipid parameters, and prednisone and cyclosporine doses were determined. RESULTS: Safety: 48 patients received atorvastatin for 24,240 person-days at a mean dose exposure of 21 +/- 10 mg. Rhabdomyolysis, myositis, myalgias, and hepatotoxicity occurred in 0, 2, 2, and 0 patients, respectively. All events occurred at the 10-mg dose, within the first 3 months, and were rapidly reversible with atorvastatin discontinuation. Efficacy: Thirty-four patients evaluable for efficacy analyses had a pre-atorvastatin LDL of 145 +/- 38 mg/dl on the following statins: pravastatin (n = 30, 40 +/- 0mg), fluvastatin (n = 3, 33 +/- 12 mg), simvastatin (n = 1, 40 mg). After atorvastatin (21 +/- 9 mg/day) for 133 +/- 67 days, LDL was reduced to 97 +/- 24 mg/dl (relative reduction 31 +/- 20%, p < 0.0001). At the end of the observation period (418 +/- 229 days, atorvastatin final dose 24 +/- 14 mg/day), LDL was further decreased to 88 +/- 23 mg (relative reduction 37 +/- 17%, p < 0.0001). CONCLUSION: Atorvastatin, when used at moderate doses and with close biochemical and clinical monitoring, appears to be safe and is effective in aggressively lowering LDL in heart transplant recipients when treatment with other statins has failed to achieve LDL goals.  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