全文获取类型
收费全文 | 199937篇 |
免费 | 13758篇 |
国内免费 | 691篇 |
专业分类
耳鼻咽喉 | 2508篇 |
儿科学 | 5263篇 |
妇产科学 | 3110篇 |
基础医学 | 26165篇 |
口腔科学 | 3194篇 |
临床医学 | 20528篇 |
内科学 | 42465篇 |
皮肤病学 | 2758篇 |
神经病学 | 19349篇 |
特种医学 | 7132篇 |
外国民族医学 | 4篇 |
外科学 | 30160篇 |
综合类 | 2743篇 |
现状与发展 | 1篇 |
一般理论 | 253篇 |
预防医学 | 16767篇 |
眼科学 | 4797篇 |
药学 | 13790篇 |
2篇 | |
中国医学 | 260篇 |
肿瘤学 | 13137篇 |
出版年
2023年 | 1139篇 |
2022年 | 1824篇 |
2021年 | 4364篇 |
2020年 | 2506篇 |
2019年 | 4118篇 |
2018年 | 4734篇 |
2017年 | 3494篇 |
2016年 | 3764篇 |
2015年 | 4530篇 |
2014年 | 6495篇 |
2013年 | 9188篇 |
2012年 | 13900篇 |
2011年 | 14704篇 |
2010年 | 8191篇 |
2009年 | 7557篇 |
2008年 | 13047篇 |
2007年 | 13780篇 |
2006年 | 13204篇 |
2005年 | 13476篇 |
2004年 | 12546篇 |
2003年 | 12016篇 |
2002年 | 11196篇 |
2001年 | 1756篇 |
2000年 | 1310篇 |
1999年 | 1774篇 |
1998年 | 2460篇 |
1997年 | 1986篇 |
1996年 | 1616篇 |
1995年 | 1552篇 |
1994年 | 1323篇 |
1993年 | 1336篇 |
1992年 | 996篇 |
1991年 | 890篇 |
1990年 | 842篇 |
1989年 | 781篇 |
1988年 | 724篇 |
1987年 | 667篇 |
1986年 | 671篇 |
1985年 | 802篇 |
1984年 | 1005篇 |
1983年 | 974篇 |
1982年 | 1386篇 |
1981年 | 1274篇 |
1980年 | 1107篇 |
1979年 | 555篇 |
1978年 | 687篇 |
1977年 | 642篇 |
1976年 | 518篇 |
1975年 | 466篇 |
1974年 | 412篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Wynn L. Walker Elliot M. Landaw Richard E. Dickerson David S. Goodsell 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(11):5634-5639
Three- and four-ring polyamides containing N-methylimidazole and N-methylpyrrole, and their hairpin-linked derivatives, bind side-by-side in the minor groove of DNA in a sequence-specific manner. The sequences recognized by side-by-side molecules are dependent on the pairings of the polyamide rings to the bases. In this study we report a mathematical model for estimating the free energies of binding for γ-aminobutyric acid-linked polyamides to 5- and 6-bp DNA sequences. The model parameters are calibrated by a least-squares fit to 35 experimental binding constants. The model performs well in cross-validation experiments and the parameters are consistent with previously proposed empirical rules of polyamide–DNA binding. We apply the model to the design of targeted polyamides, evaluating the ability of the proposed polyamides to bind to a DNA sequence of interest while minimizing binding to the remaining DNA sequences. 相似文献
62.
Veronique Braud E. Yvonne Jones Andrew McMichael 《European journal of immunology》1997,27(5):1164-1169
Human histocompatibility leukocyte antigen E (HLA-E) and mouse major histocompatibility complex (MHC) class Ib antigen, Qa-1, share the same substitutions at two normally conserved positions 143 and 147, which are likely to affect binding of the C terminus of peptides. Qa-1 is able to bind a peptide derived from the leader sequence of H-2 D and H-2 L molecules. We developed a peptide binding assay in vitro to compare the binding specificity of HLA-E with the mouse MHC class Ib molecule Qa-1. We demonstrate that HLA-E binds, although poorly, the peptide which binds to Qa-1 and that it also binds nonamer signal sequence-derived peptides from human MHC class I molecules. Using alanine and glycine substitutions, we could define primary anchor residues at positions 2 and 9 and secondary anchor residues at position 7 and possibly 3. 相似文献
63.
64.
Frances J. Mather Richard M. Simon Gary M. Clark Daniel D. 《Statistics in medicine》1990,9(9):1118-1118
65.
Andrew Williams 《The British journal of general practice》2002,52(484):940-941
66.
Steven Ganzberg Richard A Pape F Michael Beck 《Journal of oral and maxillofacial surgery》2002,60(3):244-50; discussion 250-1
PURPOSE: Remifentanil is a new, short-acting opioid that is similar pharmacodynamically to currently available opioids but differs in its pharmacokinetics. In the present study, we compared the use of remifentanil with the use of meperidine during intravenous conscious sedation for third molar surgery. PATIENTS AND METHODS: Forty patients who were scheduled for the removal of impacted third molars were randomly assigned to undergo 1 of 2 intravenous conscious sedation techniques. For both groups, 50:50 nitrous oxide oxygen were administered via nasal hood, and midazolam was titrated to Verril's sign. Twenty patients each then received either remifentanil 0.05 microgram/kg/min or meperidine 50 mg. Both patients and surgeons were blinded to the narcotic that was used. Blood pressure, heart rate, and oxygen saturation were determined before sedation and every 5 minutes during surgery. Recovery was measured using serial Trieger tests every 5 minutes after surgery. Patient and surgeon satisfaction of the quality of sedation was measured with a visual analog scale. RESULTS: Peak heart rate (91 beats/min for remifentanil vs 107 beats/min for meperidine, P <.01) and peak systolic blood pressure (131 mm Hg for remifentanil vs. 142 mm Hg for meperidine, P <.05) were significantly lower for the remifentanil group. Although there was a trend toward increased surgeon satisfaction with remifentanil (86 of 100 with remifentanil vs. 73 of 100 with meperidine), it was not found to be statistically significant. Likewise, other physiologic parameters were not found to be statistically significant. CONCLUSIONS: The lower peak heart rate and systolic blood pressure levels indicate that remifentanil may allow for less fluctuation in cardiovascular parameters. This could prove beneficial in patients with cardiovascular compromise. 相似文献
67.
68.
Meir Steiner Richard J. Katz Giulio Baldrighi Bernard J. Carroll 《Psychoneuroendocrinology》1981,6(1):81-90
(1) The estrous cycle in the rat may be used to study recurrent changes in motor behaviors and motivation which are strongly related to cyclic hormonal and CNS changes. (2) The peak in motivated behaviors occurs during a sharply defined period on the night between proestrus and estrus and is evident in facilitated wheel-running, lordosis, and intracranial self-stimulation. (3) Behaviors without a clearly motivated character do not show an estrous cyclicity. (4) The estrous cyclic variation in intracranial self-stimulation was observed at a specific locus — the pars campacta of the substantia nigra. (5) A neurochemical link between sexually motivated behavior, wheel running and intracranial self-stimulation is suggested. This link is in part dopaminergic but is probably also activated by many other systems. 相似文献
69.
Dr. Robert L. Geggel David R. Fulton Harvey L. Chernoff Richard Cleveland Thomas J. Hougen 《Pediatric cardiology》1987,8(4):279-283
Summary An infant girl is described who had cor triatriatum and partial anomalous pulmonary venous connection of the left pulmonary
veins to the coronary sinus, the first report of this combination of lesions. The infant also had a Dandy-Walker malformation
and multiple facial and intrathoracic hemangiomas. The cardiac diagnosis was made by two-dimensional echocardiography. Cardiac
catheterization and angiography confirmed the findings and also demonstrated a persistent left superior vena cava draining
to the coronary sinus. The infant underwent successful surgical repair. Partial anomalous pulmonary venous connection and
left superior vena cava not infrequently are associated with cor triatriatum. Although two-dimensional echocardiography is
sensitive for the detection of cor triatriatum, preoperative cardiac catheterization is necessary to identify unequivocally
systemic and pulmonary venous connections. 相似文献
70.
Paul Wexberg MD BM Richard Pacher MD Suzanne Rdler MD Katharina Kiss MD Gilbert Beran MD Michael Grimm MD Gerald Maurer MD Dietmar Glogar MD FESC 《The Journal of heart and lung transplantation》2002,21(12):583-1263
BACKGROUND: Endothelin, a peptide with strong vasoconstrictive and mitogenic properties, has been found to increase after cardiac transplantation. We therefore assessed the association between its precursor peptide, big endothelin-1, and intimal hyperplasia and coronary flow reserve after heart transplantation. METHODS: Thirty-five patients without hemodynamically significant coronary artery disease after heart transplantation were investigated: Average peak flow velocity in the left anterior descending artery (LAD) was assessed by intracoronary Doppler at baseline as well as after injection of adenosine; coronary flow reserve was calculated as a ratio of both and was corrected for patient age and baseline average peak flow velocity. Lumen, intima + media and total vessel area were measured by intracoronary ultrasound. The plasma concentration of big endothelin-1 in venous blood was determined by radioimmunoassay. RESULTS: Patients with elevated big endothelin-1 levels (>2 fmol/ml) tended to have a decreased corrected coronary flow reserve (2.60 +/- 0.9 vs 3.21 +/- 1.0, p = 0.078). They also had a significantly larger intima + media area (5.82 +/- 2.9 vs 2.37 +/- 2.9 mm(2), p = 0.004) and total vessel area (18.36 +/- 5.8 vs 12.81 +/- 4.8 mm(2), p = 0.012) than those with normal plasma concentrations. CONCLUSIONS: Our study suggests an association between elevated big endothelin-1 plasma levels and the development of intimal hyperplasia and reduction of coronary flow reserve after cardiac transplantation. 相似文献