全文获取类型
收费全文 | 28875篇 |
免费 | 1678篇 |
国内免费 | 329篇 |
专业分类
耳鼻咽喉 | 561篇 |
儿科学 | 390篇 |
妇产科学 | 332篇 |
基础医学 | 5128篇 |
口腔科学 | 624篇 |
临床医学 | 2428篇 |
内科学 | 5628篇 |
皮肤病学 | 1055篇 |
神经病学 | 2056篇 |
特种医学 | 1562篇 |
外科学 | 3645篇 |
综合类 | 175篇 |
现状与发展 | 1篇 |
一般理论 | 5篇 |
预防医学 | 1296篇 |
眼科学 | 520篇 |
药学 | 2744篇 |
中国医学 | 371篇 |
肿瘤学 | 2361篇 |
出版年
2023年 | 173篇 |
2022年 | 603篇 |
2021年 | 947篇 |
2020年 | 481篇 |
2019年 | 690篇 |
2018年 | 780篇 |
2017年 | 653篇 |
2016年 | 911篇 |
2015年 | 1297篇 |
2014年 | 1617篇 |
2013年 | 1753篇 |
2012年 | 2674篇 |
2011年 | 2571篇 |
2010年 | 1470篇 |
2009年 | 1299篇 |
2008年 | 1783篇 |
2007年 | 1683篇 |
2006年 | 1451篇 |
2005年 | 1285篇 |
2004年 | 1129篇 |
2003年 | 977篇 |
2002年 | 838篇 |
2001年 | 604篇 |
2000年 | 504篇 |
1999年 | 424篇 |
1998年 | 186篇 |
1997年 | 136篇 |
1996年 | 98篇 |
1995年 | 104篇 |
1994年 | 75篇 |
1993年 | 58篇 |
1992年 | 147篇 |
1991年 | 155篇 |
1990年 | 115篇 |
1989年 | 130篇 |
1988年 | 113篇 |
1987年 | 113篇 |
1986年 | 100篇 |
1985年 | 95篇 |
1984年 | 69篇 |
1983年 | 63篇 |
1982年 | 43篇 |
1981年 | 42篇 |
1980年 | 35篇 |
1979年 | 52篇 |
1978年 | 50篇 |
1977年 | 44篇 |
1976年 | 36篇 |
1974年 | 31篇 |
1973年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Hy De Lee Euy Young Soh Hoon Sang Chi Byong Ro Kim Kyong Sik Lee Kyung Soon Song Hyun Joo Jung 《Surgery today》1990,20(2):180-185
The relationship between primary tumor proliferative activity and clinical and pathologic characteristics was analyzed in
relation to menopausal status in 32 patients with malignant or benign breast disease. The thymidine labeling index (TLI) showed
significantly higher median values in the cancer patients (3.48 per cent) than in the patients with benign diseases (1.02
per cent). TLI was not significantly affected by delayed incubation at room temperature for about 1 hour. In the breast cancer
patients, TLI did not significantly correlate to tumor size, the presence of axillary lymph node metastasis or pathologic
nuclear grading. The only significant difference was limited to the breast cancer patients without axillary lymph node metastasis
in relation to menopausal status; the TLI in the premenopausal patients (5.10 per cent) was significantly higher (p<0.05)
than that in the postmenopausal patients (2.28 per cent). These data thus suggest that among premenopausal patients without
axillary lymph node metastasis, those with a high TLI could be potential candidates for adjuvant chemotherapy. 相似文献
72.
73.
The favored tautomeric and ionic structures were examined for the oxidative DNA damage adduct 8-hydroxy-2'-deoxyguanosine and its RNA analogue 8-hydroxyguanosine by 15N NMR spectroscopy. In addition, 15N chemical shifts and coupling constants from 13 different guanine nucleosides, including a wide variety of C8 substitutions (OH, SH, Br, OCH2C6H5, OCH3, SCH3, and SO2CH3), have been analyzed with respect to their tautomeric structures. A -98.5-Hz proton-nitrogen coupling constant observed for the N7 resonance of 8-hydroxyguanosine in dimethyl sulfoxide was evidence for 8-keto substitution, which is contrary to the structure implied by the generally used nomenclature. The pH dependence of 15N NMR spectra of 8-hydroxyguanosine in aqueous solution showed downfield shifts of the N1 and N7 resonances that were greater than 50 ppm, which indicated the conversion from a neutral 6,8-diketo to a 6-enolate-8-keto (pKa1 = 8.6) and finally to a 6,8-dienolate structure (pKa2 = 11.7). There was no evidence of an 8-enol substituent in the absence of ionization. It is proposed that the syn conformation of these oxidized bases in duplex DNA and RNA can be further stabilized by abnormal hydrogen bonding or mispairing that involves N7-H. The combined data show that 15N NMR is a sensitive probe to examine tautomerism of the guanine ring system. The analysis indicates that the change from a single to a double bond for the C8 substituent, and the accompanying removal of the normal double bond between N7 and C8 on the imidazole ring system, has no detectable effect on the tautomerism at the N1-O6 site of the pyrimidine ring system for both the 8-keto and 8-thio substitutions. In addition, large differences in electronegativity of the C8 substituents do not alter the N1-O6 tautomerism. 相似文献
74.
Perforation of the large bowel during colonoscopy in Singapore 总被引:1,自引:0,他引:1
The management of seven patients with colonoscopy-related perforations is described. This study demonstrates the need for an early laparotomy. A high index of suspicion is required to reach an early diagnosis. Patients with no preexisting medical problems who underwent early surgery recovered with little morbidity. In elderly patients (greater than 75 years), colonoscopic perforation can be fatal. Endoscopy should be performed with special care in such patients. 相似文献
75.
123I-MIBG myocardial scintigraphy as a noninvasive screen for the diagnosis of coronary artery spasm
Jong-Won Ha Jong-Doo Lee Yangsoo Jang Namsik Chung June Kwan Se-Joong Rim Young-Joon Lee Won-Heum Shim Seung-Yun Cho Sung-Soon Kim 《Journal of nuclear cardiology》1998,5(6):591-597
Background It has been suggested that the sympathetic nervous system might play an important role in the development of coronary artery
spasm. However, no cardiac imaging modality has been able to demonstrate abnormal sympathetic innervation in patients with
coronary artery spasm. The purpose of this study was to assess the presence and location of abnormal sympathetic innervation
using iodine 123-metaiodobenzylguanidine (123I-MIBG) single photon emission computed tomography (SPECT) and to evaluate the clinical efficacy of 123I-MIBG SPECT as a noninvasive screening test in patients with coronary artery spasm.
Methods and Results Coronary arteriography and a provocative test with intravenous administration of ergonovine maleate were performed in 26 patients
(20 men, 6 women, mean age 48.2±12.0 years, range 20 to 67 years) who were suspected of having a coronary artery spasm. The
subjects were divided into 2 groups: group 1 (n=18) comprised subjects with negative provocative provocative test result,
and group 2 (n=8) comprised subjects with negative provocative test results. Ten healthy subjects served as controls. No abnormal
MIBG uptake was observed in the control subjects. Abnormal sympathetic nervous innervation using 123I-MIBG SPECT was observed either as a reduced uptake or a defective pattern in the perfused areas in 13 of the 18 regions
supplied by vessels of ergonovine-induced vasospasm. Normal sympathetic innervation, as evidenced by normal 123I-MIBG uptake, was noted in all of the 60 segments of normal vessel territories. Reduced uptake of 123I-MIBG was not detected in the perfused areas of 5 vasospasm-induced vessels (perfusion territory of left anterior descending
coronary artery [LAD] and the right coronary artery [RCA] in 2 and 3 patients, respectively). The sensitivity and specificity
of 123I-MIBG for detection of coronary artery spasm were 72.2% (95% confidence interval, [CI] 55% to 89%) and 100%, respectively.
The positive predictive and negative predictive values were 100% and 92.3% (95% CI 91% to 93%), respectively.
Conclusion
123I-MIBG SPECT is a feasible method to evaluate noninvasively and localize the territories of coronary arteries with spasm.
Invasive diagnostic coronary arteriography with ergonovine provocation test may be unnecessary for diagnosis of coronary artery
spasm in patients with typical resting pain, negative exercise test or normal thallium perfusion scan results, but showing
abnormalities in 123I-MIBG SPECT.
Presented in part at the European Association of Nuclear Medicine Congress, September 1996, Copenhagen, Denmark. 相似文献
76.
77.
Chest radiographs and chest computed tomography (CT) scans were compared in 203 patients with newly diagnosed Hodgkin disease. The incidence of positive findings was tabulated from six intrathoracic lymph node groups, lung parenchyma, pericardium, pleura, and chest wall. The discordant cases were assessed to determine impact on clinical management. The CT scans provided additional evidence of disease involvement, ranging from 0% to 15% at each of the designated anatomic sites. Treatment was altered in 9.4% of all patients (19 of 203), including 13.8% (nine of 65) of those undergoing radiation therapy alone and 8.2% (ten of 122) of those undergoing combined-modality treatment. We conclude that routine chest CT examinations are valuable in the clinical management of those patients for whom radiation therapy is planned. 相似文献
78.
Shi Yong Ryu Chong-Kyo Lee Chong Ock Lee Hae Soo Kim Ok Pyo Zee 《Archives of pharmacal research》1992,15(3):242-245
Two triterpenes 1 and 2 with antiviral activity againstHerpes simplex virus type 1in vitro were isolated fromPrunella vulgaris. Each compound caused a significant reduction in viral cytopathic effect whenvero cells were exposed to them for 72 hours after viral challenge. They were identified asbetulinic acid(1) and 2α, 3α-dihydroxyurs-12-en-28-oic acid(2) on the basis of their spectroscopic properties. The antiviral activity of them was estimated as EC50=30 μg/ml(1) and 8 μg/ml(2), respectively by plaque reduction assay. 相似文献
79.
Molecular characterization of the mosquito vitellogenin receptor reveals unexpected high homology to the Drosophila yolk protein receptor. 总被引:2,自引:0,他引:2 下载免费PDF全文
T W Sappington V A Kokoza W L Cho A S Raikhel 《Proceedings of the National Academy of Sciences of the United States of America》1996,93(17):8934-8939
The mosquito (Aedes aegypti) vitellogenin receptor (AaVgR) is a large membrane-bound protein (214 kDa when linearized) that mediates internalization of vitellogenin, the major yolk-protein precursor, by oocytes during egg development. We have cloned and sequenced two cDNA fragments encompassing the entire coding region of AaVgR mRNA, to our knowledge the first insect VgR sequence to be reported. The 7.3-kb AaVgR mRNA is present only in female germ-line cells and is abundant in previtellogenic oocytes, suggesting that the AaVgR gene is expressed early in oocyte differentiation. The deduced amino acid sequence predicts a 202.7-kDa protein before posttranslational processing. The AaVgR is a member of the low density lipoprotein receptor superfamily, sharing significant homology with the chicken (Gallus gallus) VgR and particularly the Drosophila melanogaster yolk protein receptor, in spite of a very different ligand for the latter. Distance-based phylogenetic analyses suggest that the insect VgR/yolk protein receptor lineage and the vertebrate VgR/low density lipoprotein receptor lineage diverged before the bifurcation of nematode and deuterostome lines. 相似文献
80.