全文获取类型
收费全文 | 238636篇 |
免费 | 276209篇 |
国内免费 | 36915篇 |
专业分类
耳鼻咽喉 | 2358篇 |
儿科学 | 4020篇 |
妇产科学 | 2094篇 |
基础医学 | 87234篇 |
口腔科学 | 2206篇 |
临床医学 | 57796篇 |
内科学 | 92104篇 |
皮肤病学 | 4583篇 |
神经病学 | 21558篇 |
特种医学 | 8436篇 |
外科学 | 40211篇 |
综合类 | 51660篇 |
一般理论 | 2篇 |
预防医学 | 41058篇 |
眼科学 | 18262篇 |
药学 | 57622篇 |
3篇 | |
中国医学 | 46669篇 |
肿瘤学 | 13884篇 |
出版年
2020年 | 5832篇 |
2019年 | 13091篇 |
2018年 | 13594篇 |
2017年 | 14296篇 |
2016年 | 12859篇 |
2015年 | 12683篇 |
2014年 | 12382篇 |
2013年 | 12234篇 |
2012年 | 12006篇 |
2011年 | 13578篇 |
2010年 | 16454篇 |
2009年 | 24311篇 |
2008年 | 11669篇 |
2007年 | 8152篇 |
2006年 | 7642篇 |
2005年 | 7613篇 |
2004年 | 9692篇 |
2003年 | 8951篇 |
2002年 | 9240篇 |
2001年 | 11202篇 |
2000年 | 6769篇 |
1999年 | 12046篇 |
1998年 | 13619篇 |
1997年 | 13546篇 |
1996年 | 14612篇 |
1995年 | 14854篇 |
1994年 | 14619篇 |
1993年 | 13405篇 |
1992年 | 12661篇 |
1991年 | 12067篇 |
1990年 | 11045篇 |
1989年 | 10909篇 |
1988年 | 10480篇 |
1987年 | 9833篇 |
1986年 | 9364篇 |
1985年 | 8442篇 |
1984年 | 6530篇 |
1983年 | 6542篇 |
1982年 | 7600篇 |
1981年 | 7141篇 |
1980年 | 6806篇 |
1979年 | 6639篇 |
1978年 | 5817篇 |
1977年 | 6122篇 |
1976年 | 5743篇 |
1975年 | 5482篇 |
1974年 | 5034篇 |
1973年 | 4753篇 |
1972年 | 4754篇 |
1971年 | 4094篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
M. D. Taylor M. L. de Ceballos S. Rose P. N. Chong P. Jenner C. D. Marsden 《Journal of neural transmission (Vienna, Austria : 1996)》1991,3(2):99-108
Summary Aged common marmosets were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 0.5–2.0 mg/kg/week i.p.) for 16 or 24 weeks, observed for a total of 30 weeks and then killed for measurement of biochemical pramaters in basal ganglia. The MPTP treatment induced a marked depletion in dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels in the caudate nucleus and putamen. In contrast, the concentrations of five neuropeptides: [Met5]-enkephalin, [Leu5]-enkephalin, cholecystokinin, substance P and neurotensin as measured by a combined HPLC/RIA method, remained unaltered in all basal ganglia regions examined. Enkephalin precursor levels, as reflected by cryptic [Met5]-enkephalin content, were increased in the putamen, but not in the caudate nucleus, as a consequence of MPTP administration. Cryptic [Leu5]-enkephalin content remained unchanged in the striatum of MPTP treated marmosets. Overall, these results suggest an increase in striatal [Met5]-enkephalin release following chronic MPTP treatment of aged marmosets. However, the chronic treatment of aged marmosets with MPTP does not reproduce the neuropeptide alterations characteristic of Parkinson's disease. 相似文献
63.
D. Caroline Blanchard Jon K. Shepherd Antonio De Padua Carobrez Robert J. Blanchard 《Neuroscience and biobehavioral reviews》1991,15(4):461-468
Female rats consistently show a pattern of differences in defensive behaviors compared to males which parallel the effects of exposure to a nonpainful threat stimulus (cat or cat odor) in the same tests and measures. These indications of greater defensiveness for females are particularly common in situations involving potential, as opposed to actual and present, threat, a factor which probably also reflects ceiling or floor effects in situations involving very intense defensiveness. In addition, pharmacological studies indicate sex differences in the effects of selective serotonin (5-HT) receptor agonists and antagonists on defensive responding. These findings indicate that sex effects must be considered in studies of the pharmacological control of defensive behaviors, and suggest that responsivity to sex effects may be an additional criterion for the suitability of animal models of anxiety. 相似文献
64.
Theoretical calculation of relative binding affinity in host-guest systems. 总被引:5,自引:3,他引:2 下载免费PDF全文
T P Lybrand J A McCammon G Wipff 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(4):833-835
The relative free energy of binding the anions Cl- and Br- to the macrotricyclic receptor SC24 in water has been computed by a computer simulation technique. This result and an incidental result for the relative free energy of hydration of the anions are in excellent agreement with experimental data. The simulation approach to ligand-receptor interactions that is described here has significant potential as a predictive tool in chemistry, biochemistry, and pharmacology. 相似文献
65.
66.
67.
Performance characteristics of pooled rabbit IgG polyclonal anti-C3d are compared with one mouse IgM and three mouse IgG monoclonal anti-C3d antibodies (MAs). IgG MA,s employed singly or in combination, failed to precipitate C3d; by contrast, IgM MA and polyclonal anti-C3d precipitated C3d. Measurements of polyclonal anti-C3d concentration by chemical means and by 125I-C3d radioimmunoassay (RIA) agreed closely. RIA values were 50% of chemical measurement values for three of the four MAs. Use of sucrose density gradient ultracentrifugation to assess MA C3d/anti-C3d molar combining ratios for soluble anti-C3d/C3d was not possible because fast-sedimenting multimeric C3d/anti-C3d complexes did not form. Dissociation and competitive binding studies indicate that (1) two MAs had substantially lower affinities than the other anti-C3d antibodies, and (2) polyclonal anti-C3d recognizes more C3d epitopes than are recognized by individual MAs. The results demonstrate antigenic complexity of C3d fragment and illustrate the difficulties of predicting individual MA performance based on prior experience with polyclonal antibodies. 相似文献
68.
Torsten T. Bauer Joachim Lorenz Klaus-Friedrich Bodmann Friedrich Vogel 《Medizinische Klinik》2005,26(13):355-360
Hintergrund:
Die nosokomiale Pneumonie gehört zu den häufigsten nosokomialen Infektionen und ist die häufigste auf der Intensivstation. Die nosokomiale Pneumonie ist mit einer signifikanten Mortalität und Morbidität assoziiert, und ihr Auftreten verschlechtert die Prognose des Patienten deutlich. Nach der Definition der DRGs auch im deutschen Krankenhaussystem ist die nosokomiale Pneumonie überwiegend Sache des Krankenhauses und kann somit nicht nur das Ergebnis der Patientenbehandlung, sondern auch das finanzielle Ergebnis des Krankenhauses beeinträchtigen. 相似文献69.
70.
Transplantation of microencapsulated bovine chromaffin cells reduces lesion-induced rotational asymmetry in rats 总被引:7,自引:0,他引:7
Surrounding bovine chromaffin cells by a semipermeable membrane may protect the transplanted cells from a host immune response and shield them from the inflammatory process resulting from the surgical trauma. Encapsulation of the chromaffin cells was achieved by inter-facial adsorption of a polycation on a polyanionic colloid matrix in which the chromaffin cells were entrapped. Basal and potassium-evoked release of catecholamines from encapsulated bovine chromaffin cells was analyzed over a 4-week period in vitro. Norepinephrine and dopamine release remained constant over time whereas epinephrine release significantly decreased. The chromaffin cells also retained the capacity for depolarization-elicited catecholamine release 4 weeks following the encapsulation procedure. Morphological analysis revealed the presence of intact chromaffin cells with well-preserved secretory granules. Striatial implantation of chromaffin cell-loaded capsules significantly reduced apomorphine-induced rotation compared to empty polymer capsules in animals lesioned with 6-hydroxydopamne frr at least 4 weeks. Intact chromaffin cells expressing tyrosine hydroxylase and dopamine-β-hydroxylase were observed in all capsules implanted in the striatum for 4 weeks. The assessment of the clinical potential of transplanting encapsulated adrenal chromaffin cells of either allo- or xenogeneic origin for Parkinson's disease will require long-term behavioral studies. The present study suggests, however, that the polymer encapsulation procedure may offer an alternative to adrenal autografts as a source of dopaminergic tissue. 相似文献