全文获取类型
收费全文 | 553265篇 |
免费 | 52780篇 |
国内免费 | 1113篇 |
专业分类
607158篇 |
出版年
2018年 | 15017篇 |
2017年 | 13610篇 |
2016年 | 12741篇 |
2015年 | 9108篇 |
2014年 | 9850篇 |
2013年 | 13742篇 |
2012年 | 19548篇 |
2011年 | 27751篇 |
2010年 | 21553篇 |
2009年 | 17310篇 |
2008年 | 22806篇 |
2007年 | 24734篇 |
2006年 | 13151篇 |
2005年 | 13198篇 |
2004年 | 13402篇 |
2003年 | 12930篇 |
2002年 | 12240篇 |
2001年 | 22020篇 |
2000年 | 21990篇 |
1999年 | 17555篇 |
1998年 | 6416篇 |
1997年 | 6635篇 |
1996年 | 6416篇 |
1995年 | 5803篇 |
1994年 | 5867篇 |
1993年 | 5736篇 |
1992年 | 13769篇 |
1991年 | 13100篇 |
1990年 | 12759篇 |
1989年 | 12579篇 |
1988年 | 11263篇 |
1987年 | 10884篇 |
1986年 | 9944篇 |
1985年 | 9757篇 |
1984年 | 8283篇 |
1983年 | 7187篇 |
1982年 | 5635篇 |
1981年 | 5123篇 |
1980年 | 4753篇 |
1979年 | 7750篇 |
1978年 | 6000篇 |
1977年 | 5508篇 |
1976年 | 5141篇 |
1975年 | 5418篇 |
1974年 | 5895篇 |
1973年 | 5730篇 |
1972年 | 5352篇 |
1971年 | 5012篇 |
1970年 | 3956篇 |
1969年 | 3876篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Cell migration in the embryo and adult organism 总被引:1,自引:0,他引:1
C A Erickson 《Current opinion in cell biology》1990,2(1):67-74
152.
The present study was designed to determine whether the supplementation of vitamin E in the copper-deficient diet would ameliorate the severity of copper deficiency in fructose-fed rats. Lipid peroxidation was measured in the livers and hearts of rats fed a copper-deficient diet (0.6 microg Cu/g) containing 62% fructose with adequate vitamin E (0.1 g/kg diet) or supplemented with vitamin E (1.0 g/kg diet). Hepatic lipid peroxidation was significantly reduced by vitamin E supplementation compared with the unsupplemented adequate rats. In contrast, myocardial lipid peroxidation was unaffected by the level of vitamin E. Regardless of vitamin E supplementation, all copper-deficient rats exhibited severe signs of copper deficiency, and some of the vitamin E-supplemented rats died of this deficiency. These findings suggest that although vitamin E provided protection against peroxidation in the liver, it did not protect the animals against the severity of copper deficiency induced by fructose consumption. 相似文献
153.
154.
155.
A C de Groot 《BMJ (Clinical research ed.)》1990,300(6740):1636-1638
156.
E Hu K Watkins S Groshen S C Chen B Malloy R Agah P Nichols J Parker A Martin M G Boosalis 《Molecular biotherapy》1990,2(2):96-103
A phase I trial of interleukin-2 and interferon gamma combination treatment in patients with advanced malignancies was performed based on preclinical in vitro and in vivo data which demonstrated synergistic antitumor effect. The toxicities, immune parameters, and tumor responses are described. The clinical and biologic maximal tolerated doses were extrapolated from these data. 相似文献
157.
Distance between the propylbenzilylcholine mustard attachment site and carbohydrates and thiol groups in muscarinic acetylcholine receptor protein from rat cerebral cortex. 总被引:1,自引:1,他引:0 下载免费PDF全文
When rat cerebral-cortex membranes were labelled with [3H]propylbenzilylcholine mustard ([3H]PrBCM), a single protein of Mr 68,000 was found to carry the atropine-sensitive covalent label. After trypsinolysis of the receptors solubilized in 0.075% SDS, the resulting fragments were submitted to size analysis in combination with wheat-germ agglutinin (WGA)-Sepharose and organomercurial-agarose chromatography. Peptides of Mr 75,000, 50,000, 30,000, 18,000 and 8000 were specifically released from the receptor. All fragments above Mr 8000 were able to bind WGA-Sepharose and therefore the peptide of Mr 18,000 was taken as the upper limit of the distance between the antagonist and the glycan moieties. The limit fragment of Mr 8000 carried chemical groups which were modified by N-ethylmaleimide and reacted with an immobilized organomercurial. About 65-80% of the labelled receptors were adsorbed on concanavalin A-Sepharose with low affinity, generating two further components after sequential application to WGA-Sepharose. About 50% of the receptors were susceptible to neuraminidase treatment, with a concomitant slight modification of the SDS/polyacrylamide-gel-electrophoretic pattern. 相似文献
158.
Does a torn anterior cruciate ligament lead to change in the central nervous drive of the knee extensors? 总被引:2,自引:0,他引:2
L G Elmqvist R Lorentzon C Johansson A R Fugl-Meyer 《European journal of applied physiology and occupational physiology》1988,58(1-2):203-207
Integrated surface electromyograms of the three superficial parts of the quadriceps and isokinetic knee extensor maximum torque and power production were recorded simultaneously and at different angular velocities in both legs in 11 male subjects with unilateral tear of the anterior cruciate ligament. The cross-sectional area (CSA) of the thigh and its muscular components were measured by computerized tomography. The principal findings were a small but significant decrease in quadriceps CSA on the affected side; a decreased active, but not passive, range of movement; decreased mechanical output, whether or not corrected for differences in CSA; and decreased electromyographic activity--particularly in rectus femoris. These findings suggest that the reason for the decreased maximum and total knee extensor performance seen in these patients is a change in knee joint receptor afferent inflow. 相似文献
159.
160.