全文获取类型
收费全文 | 14531篇 |
免费 | 797篇 |
国内免费 | 118篇 |
专业分类
耳鼻咽喉 | 190篇 |
儿科学 | 291篇 |
妇产科学 | 187篇 |
基础医学 | 2226篇 |
口腔科学 | 354篇 |
临床医学 | 1318篇 |
内科学 | 2776篇 |
皮肤病学 | 531篇 |
神经病学 | 1151篇 |
特种医学 | 632篇 |
外科学 | 2072篇 |
综合类 | 55篇 |
一般理论 | 2篇 |
预防医学 | 642篇 |
眼科学 | 376篇 |
药学 | 1332篇 |
中国医学 | 187篇 |
肿瘤学 | 1124篇 |
出版年
2023年 | 101篇 |
2022年 | 318篇 |
2021年 | 514篇 |
2020年 | 280篇 |
2019年 | 362篇 |
2018年 | 403篇 |
2017年 | 342篇 |
2016年 | 489篇 |
2015年 | 647篇 |
2014年 | 754篇 |
2013年 | 824篇 |
2012年 | 1310篇 |
2011年 | 1186篇 |
2010年 | 729篇 |
2009年 | 631篇 |
2008年 | 839篇 |
2007年 | 863篇 |
2006年 | 742篇 |
2005年 | 673篇 |
2004年 | 555篇 |
2003年 | 448篇 |
2002年 | 418篇 |
2001年 | 310篇 |
2000年 | 295篇 |
1999年 | 219篇 |
1998年 | 72篇 |
1997年 | 61篇 |
1996年 | 39篇 |
1995年 | 55篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 84篇 |
1991年 | 69篇 |
1990年 | 83篇 |
1989年 | 69篇 |
1988年 | 64篇 |
1987年 | 48篇 |
1986年 | 50篇 |
1985年 | 45篇 |
1984年 | 30篇 |
1983年 | 33篇 |
1981年 | 24篇 |
1980年 | 19篇 |
1979年 | 37篇 |
1978年 | 44篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1975年 | 30篇 |
1974年 | 27篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We present accidental findings that potassium channel blockers, such as tetraethyl-ammonium (TEA) or 4-aminopyridine (4-AP), inhibit the sustained tonic contraction induced by carbachol in rat detrusor muscle strips. The relatively lower concentrations (<2 mM) of TEA and 4-AP inhibited phasic and tonic contractions induced by 5 micro M carbachol, whilst the relatively higher concentrations of TEA and 4-AP (>5 mM) potentiated phasic contractions. The potentiation of phasic contraction was not observed in nicardipine pretreated condition. In nicardipine pretreated condition, the concentration-response curves for the negative inotropic effect of potassium channel blockers were shifted to the right by the increasing concentration of carbachol from 0.5 microM to 5 microM. IC50 was changed significantly from 0.19 to 0.64 mM (TEA) and from 0.21 to 0.96 (4-AP). Such inhibitory effects were also observed in Ca2+ depleted condition, where 0.1 mM EGTA and 1 microM thapsigargin were added into Ca2+ free solution. In conclusion, inhibitory effects of potassium channel blockers on carbachol-induced contraction may be ascribed to the direct inhibition of receptor-agonist binding. 相似文献
992.
The effect of reducing extracellular calcium concentration ([Ca(2+)](o)) on vagal afferent excitability was analyzed in a guinea pig isolated vagally innervated trachea-bronchus preparation. Afferent fibers were characterized as either having low-threshold, rapidly adapting mechanosensors (Adelta fibers) or nociceptive-like phenotypes (Adelta and C fibers). The nociceptors were derived from neurons within the jugular ganglia, whereas the low-threshold mechanosensors were derived from neurons within the nodose ganglia. Reducing [Ca(2+)](o) did not affect the excitability of the low-threshold mechanosensors in the airway. By contrast, reducing [Ca(2+)](o) selectively increased the excitability of airway nociceptors as manifested by a substantive increase in action potential discharge in response to mechanical stimulation, and in a subset of fibers, by overtly evoking action potential discharge. This increase in the excitability of nociceptors was not mimicked by a combination of omega-conotoxin and nifedipine or tetraethylammonium. Whole cell patch recordings from airway-labeled and unlabeled neurons in the vagal jugular ganglia support the hypothesis that [Ca(2+)](o) inhibits a nonselective cation conductance in vagal nociceptors that may serve to regulate excitability of the nerve terminals within the airways. 相似文献
993.
In the present study, silver-doped silica thin films were successfully prepared by sol-gel method to apply for antibacterial materials. The starting solution was prepared from 1:0.24:3.75:2.2 molar ratios of Si(OC2H5)4):AgNO3:H2O:C2H5OCH2CH2OH and then the pH value controlled at 3 with 0.5 N HNO3 solution. The formation of silver-doped glassy silica thin films at various temperatures was investigated through infrared spectroscopy, ultraviolet-visible, scanning electron microscopy and X-ray diffraction. From these analysis data, it was found that silver ions were completely trapped in the silica matrix and their reduction could be achieved at 600 degrees C annealing temperature. The antibacterial effects of silica thin films against Escherichia coli and Staphylococcus aureus were examined by film attachment method. The coating films had an excellent antibacterial performance. 相似文献
994.
995.
We report the prenatal diagnosis of trisomy 6 mosaicism via amniocentesis, in which trisomy 6 cells were identified in three of five culture vessels with 33% (5/15) of colonies showing trisomic cells. The pregnancy was electively terminated and examination revealed minor abnormalities (shortening of the femurs, micrognathia, posterior malrotation of the ears, and bilateral camptomelia of the second digit of the hands and fifth digits of the feet). Cytogenetic analysis of the placenta showed trisomy 6 in 100% of 20 cells studied. Karyotype was 46,XX in 100 cells examined from fetal skin. There are relatively few prenatally diagnosed cases of mosaic trisomy 6 at amniocentesis. Confined placental mosaicism (CPM) has been postulated in other cases where follow-up cytogenetic studies were not available. The present case differs from those previously reported, as it appears to represent CPM of chromosome 6 with phenotypic effects to the fetus. 相似文献
996.
Minimal ventilation to prevent bronchopulmonary dysplasia in extremely-low-birth-weight infants 总被引:5,自引:0,他引:5
Carlo WA Stark AR Wright LL Tyson JE Papile LA Shankaran S Donovan EF Oh W Bauer CR Saha S Poole WK Stoll B 《The Journal of pediatrics》2002,141(3):370-374
OBJECTIVE: To determine whether minimal ventilation decreases death or bronchopulmonary dysplasia (BPD).Study design: Infants with birth weight 501 g to 1000 g and mechanically ventilated before 12 hours were randomly assigned to minimal ventilation (partial pressure of carbon dioxide [PCO(2)] target >52 mm Hg) or routine ventilation (PCO(2) target <48 mm Hg) and a tapered dexamethasone course or saline placebo for 10 days, using a 2 x 2 factorial design. The primary outcome was death or BPD at 36 weeks' postmenstrual age. RESULTS: After enrollment of 220 patients, the trial was halted because of unanticipated nonrespiratory adverse events related to dexamethasone therapy. The relative risk for death or BPD at 36 weeks in the minimal versus routine ventilation groups was 0.93 (95% CI, 0.77-1.12; P =.43). Ventilator support at 36 weeks was 1% in the minimal versus 16% in the routine group (P <.01). Major morbidities and long-term outcome were comparable in both treatment groups. CONCLUSIONS: With the sample size studied, minimal ventilation did not reduce the incidence of death or BPD. The reduced ventilator support at 36 weeks in the minimal ventilation group warrants further study of this intervention. 相似文献
997.
Lee WY Kang MI Baek KH Oh ES Oh KW Lee KW Kim SW Kim CC 《Journal of Korean medical science》2002,17(6):749-754
Loss of bone mass is usually detected after bone marrow transplantation (BMT) during the early post-transplant period. However, little is known about the long-term effects of BMT on bone metabolism. We have prospectively investigated 11 patients undergoing BMT. Bone mineral density (BMD) was measured before BMT, and 1, 2, and 3 yr after BMT. Serum markers of bone turnover were serially measured before BMT and 1, 2, 3, 4, and 12 weeks, 6 months, and 1 yr after BMT. The mean change in the lumbar spine (L2-4) BMD, calculated as the percent change from the baseline to the level at 1, 2, and 3 yr was -4.7% (NS), -1.1% (NS), and +6.4% (p<0.05), respectively. The mean change in the total proximal femur BMD from the baseline to the level at 1, 2, and 3 yr was -8.5% (p<0.01), -8.7% (p<0.05) and -5.6% (p<0.05), respectively. In summary, there was little decline in lumbar BMD at 1 yr following BMT and gradual recovery until 3 yr. In contrast, femoral BMD decreased much more than the lumbar area at 1 yr and did not recover until 3 yr. The mechanism of skeletal site-selective differences in the changes of BMD needs to be elucidated. 相似文献
998.
Kim NH Park JP Jeon SH Lee YJ Choi HJ Jeong KM Lee JG Choi SP Lim JH Kim YH Kim YS Kim YM Hwang MH Cho JW Moon Y Oh SK Jeong JW 《Journal of Korean medical science》2002,17(4):571-573
Bacterial pericarditis has been recognized as a rare disease since the development of antibiotics. Usually, the disease is associated with underlying conditions or a seeding of infection elsewhere to the pericardium. Here we describe a case of group G streptococcal pericarditis as an initial presentation of colon cancer. A 52-yr-old man was admitted because of dyspnea. An electrocardiogram showed a diffuse ST-segment elevation and a two-dimensional echocardiogram showed a large amount of pericardial effusion. A pericardiocentesis was done and purulent fluid was drained. Group G streptococci was cultured in pericardial fluid. The patient was treated with antibiotics and pericardiostomy with saline irrigation. A colonoscopy revealed a small mass with moderately differentiated adenocarcinoma in rectosigmoid colon. He underwent a mucosectomy and was recovered without any complication. 相似文献
999.
We report a case of tuberculous thyroiditis in a woman with Behçet's syndrome. The initial physical examination in May 1998 revealed multiple soft, nontender, mobile lymph nodes, each measuring less than 1 cm, in the left lower internal jugular chain. Sonography performed in February 2000 showed multiple small (< 1 cm), oval lymph nodes, each with an intact fatty hilum, in the left lower internal jugular chain; the thyroid gland appeared normal. Follow‐up sonography 6 months later showed multifocal, heterogeneous, hypoechoic lesions with ill‐defined margins in both lobes of the thyroid and several small, oval lymph nodes, each with an intact fatty hilum, in the left lower internal jugular chain. Fine‐needle aspiration was performed on the largest thyroid lesion, and cytologic analysis of the aspirate revealed a small number of epithelioid histiocytes in a necrotic background, which was suggestive of tuberculosis. Follow‐up sonography after 3 months of antituberculosis chemotherapy showed that the thyroid lesions had resolved. © 2002 Wiley Periodicals, Inc. J Clin Ultrasound 30:184–188, 2002; DOI 10.1002/jcu.10041 相似文献
1000.
Role of efflux pumps and mutations in genes for topoisomerases II and IV in fluoroquinolone-resistant Pseudomonas aeruginosa strains 总被引:1,自引:0,他引:1
We have investigated the occurrence of mutations in topoisomerase II (DNA gyrase) subunit B(gyrB) and topoisomerase IV subunit E(parE) and the hyperexpression of genes for four efflux pump proteins in 20 previously described, fluoroquinolone-resistant clinical strains of Pseudomonas aeruginosa. Amino acid alterations were found in GyrB in five strains and in ParE in three strains with MIC of norfloxacin > or = 8 mg/L, and it is likely that some of the alterations contribute to the quinolone resistance exhibited by these strains. Seventeen of the 20 strains overproduced mRNA for one or more pump proteins (MexB, MexD, MexF, or MexY), which caused multidrug resistance phenotype in more than half of strains. Two strains were hypermutable and one of them was highly resistant, but the other strain was only moderately resistant. 相似文献