全文获取类型
收费全文 | 1337149篇 |
免费 | 145321篇 |
国内免费 | 630篇 |
出版年
2018年 | 11896篇 |
2016年 | 16413篇 |
2015年 | 22392篇 |
2014年 | 26351篇 |
2013年 | 37682篇 |
2012年 | 42315篇 |
2011年 | 43039篇 |
2010年 | 29569篇 |
2009年 | 27550篇 |
2008年 | 39071篇 |
2007年 | 40407篇 |
2006年 | 37738篇 |
2005年 | 36397篇 |
2004年 | 36079篇 |
2003年 | 34727篇 |
2002年 | 33869篇 |
2001年 | 55216篇 |
2000年 | 54908篇 |
1999年 | 44425篇 |
1998年 | 17347篇 |
1997年 | 17751篇 |
1996年 | 16831篇 |
1995年 | 15799篇 |
1994年 | 15458篇 |
1993年 | 15434篇 |
1992年 | 37293篇 |
1991年 | 36606篇 |
1990年 | 35850篇 |
1989年 | 35011篇 |
1988年 | 32396篇 |
1987年 | 31408篇 |
1986年 | 29140篇 |
1985年 | 29273篇 |
1984年 | 24395篇 |
1983年 | 21399篇 |
1982年 | 16650篇 |
1981年 | 15031篇 |
1980年 | 14165篇 |
1979年 | 23324篇 |
1978年 | 18676篇 |
1977年 | 16937篇 |
1976年 | 16087篇 |
1975年 | 17837篇 |
1974年 | 19238篇 |
1973年 | 18955篇 |
1972年 | 17179篇 |
1971年 | 15687篇 |
1970年 | 13573篇 |
1969年 | 13174篇 |
1968年 | 11673篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Training-induced bradycardia and intrinsic heart rate in rats 总被引:1,自引:0,他引:1
E Nylander K Sigvardsson A Kilbom 《European journal of applied physiology and occupational physiology》1982,48(2):189-199
After 10 weeks of treadmill training, female Sprague-Dawley rats had developed a bradycardia at exercise on submaximal work loads. This bradycardia was also present after autonomic denervation and in isolated perfused heart preparations. The heart weight/body weight ratio was increased in these trained animals compared to untrained littermates. Sympathectomized, trained rats developed the same degree of cardiac hypertrophy, but their heart rate after denervation and in the isolated heart was the same as in sympathectomized, untrained rats. It is concluded that the bradycardia of trained and thereafter denervated animals seen in this and a previous investigation represents an adaptation within the heart itself, since it was present in the isolated heart. These results thus provide further evidence for a non-neural component in training-induced bradycardia. Since the trained sympathectomized rats had a cardiac hypertrophy but no reduction of intrinsic heart rate, it seems likely that the myocardial mass is of minor importance for the level of intrinsic heart rate. 相似文献
43.
L J Petterborg M K Vaughan L Y Johnson T H Champney R J Reiter 《Comparative biochemistry and physiology. A, Comparative physiology》1984,78(1):31-34
Exposure of male Syrian hamsters (Mesocricetus auratus) for 10 weeks to short photoperiod (SP) providing 10 hr light: 14 hr darkness (10:14 LD) produced a significant reduction in the weights of the reproductive organs, plasma thyroxine (T4) levels and free T4 index (FT4I) compared to the values of animals exposed to long photoperiod (LP, 14:10 LD). C57bl male house mice (Mus musculus) kept in SP (10:14 LD) had reproductive organ weights equivalent to those of mice kept in long days (14:10 LD) and lower T3 uptake (T3U) values. Male gerbils (Meriones unguiculatus) exposed to 13 weeks of SP (10:14 LD) had lower body weights, testes and seminal vesicle weights and higher T3U values compared to LP (14:10 LD) controls. However, no effect was seen on plasma T4 and triiodothyronine (T3) values nor the FT4I and free T3 index (FT3I). White-footed male mice (Peromyscus leucopus) exposed to SP (8:16 LD) had significantly lower testes and seminal vesicle weights while plasma T4 and T3 levels were unaffected. Snell strain house mice (Mus musculus) exposed to SP (8:16 LD) had normal reproductive organ weights compared to the values of LP-exposed (16:8 LD) control animals. However, there was a significant depression in T3 and in the FT3I in the SP animals. 相似文献
44.
Airway area by acoustic reflections measured at the mouth 总被引:5,自引:0,他引:5
Fredberg J. J.; Wohl M. E.; Glass G. M.; Dorkin H. L. 《Journal of applied physiology》1980,48(5):749-758
45.
46.
P C de Visser N M A J Kriek P A V van Hooft A Van Schepdael D V Filippov G A van der Marel H S Overkleeft J H van Boom D Noort 《The journal of peptide research》2003,61(6):298-306
As part of a program towards the development of novel antibiotics, a convenient method for solid-phase synthesis of the cyclic cationic peptide polymyxin B1 and analogues thereof is described. The methodology, based on cleavage-by-cyclization using Kenner's safety-catch linker, yields crude products with purities ranging from 37-67%. Antibacterial assays revealed that analogues 23-26, in which the (S)-6-methyloctanoic acid moiety is replaced with shorter acyl chains, exhibit distinct antimicrobial activity. The results suggest that the length of the acyl chain is rather critical for antimicrobial activity. On the other hand, substitution of the hydrophobic ring-segment D-Phe-6/Leu-7 in polymyxin B1 with dipeptide mimics (i.e. analogues 27-33) resulted in almost complete loss of antimicrobial activity. 相似文献
47.
48.
49.
50.
R N Korotkina A A Papin A A Karelin 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(10):438-440
Experiments on 330 rats were made to study the influence of benzodiazepines (diazepam, dormicum and phenazepam) on 5'-nucleotidase activity in brain homogenates. It was discovered that diazepam and dormicum in doses of 3 and 4 mg, phenazepam in doses of 3.75 and 5 mg per 200 g bw provoked a 16-20% reduction in 5'-nucleotidase activity. The maximal effect of diazepam (3 and 4 mg doses) was attained 1 h after intraperitoneal injection, that of dormicum (3 mg) 30 min and of phenazepam (5 mg) 1 h after intraperitoneal injection. It is assumed that benzodiazepines are involved in AMP metabolism. 相似文献