全文获取类型
收费全文 | 7719篇 |
免费 | 78篇 |
国内免费 | 54篇 |
专业分类
系统科学 | 41篇 |
丛书文集 | 90篇 |
教育与普及 | 13篇 |
理论与方法论 | 17篇 |
现状及发展 | 3351篇 |
研究方法 | 414篇 |
综合类 | 3841篇 |
自然研究 | 84篇 |
出版年
2016年 | 48篇 |
2012年 | 106篇 |
2011年 | 210篇 |
2010年 | 56篇 |
2009年 | 53篇 |
2008年 | 156篇 |
2007年 | 179篇 |
2006年 | 134篇 |
2005年 | 140篇 |
2004年 | 243篇 |
2003年 | 126篇 |
2002年 | 133篇 |
2001年 | 298篇 |
2000年 | 294篇 |
1999年 | 214篇 |
1992年 | 118篇 |
1991年 | 123篇 |
1990年 | 106篇 |
1989年 | 99篇 |
1988年 | 106篇 |
1987年 | 120篇 |
1986年 | 114篇 |
1985年 | 158篇 |
1984年 | 121篇 |
1983年 | 98篇 |
1982年 | 84篇 |
1981年 | 116篇 |
1980年 | 109篇 |
1979年 | 251篇 |
1978年 | 198篇 |
1977年 | 184篇 |
1976年 | 139篇 |
1975年 | 162篇 |
1974年 | 209篇 |
1973年 | 173篇 |
1972年 | 193篇 |
1971年 | 213篇 |
1970年 | 276篇 |
1969年 | 209篇 |
1968年 | 188篇 |
1967年 | 210篇 |
1966年 | 182篇 |
1965年 | 145篇 |
1959年 | 53篇 |
1958年 | 104篇 |
1957年 | 76篇 |
1956年 | 73篇 |
1955年 | 52篇 |
1954年 | 74篇 |
1948年 | 49篇 |
排序方式: 共有7851条查询结果,搜索用时 15 毫秒
21.
22.
J E Landegent N Jansen in de Wal G J van Ommen F Baas J J de Vijlder P van Duijn M Van der Ploeg 《Nature》1985,317(6033):175-177
During the past few years, several methods have been developed for the detection of specific nucleic acid sequences by in situ hybridization using non-radioactive labels such as fluorochromes, cytochemically detectable enzymes and electron-dense markers. These methods are preferable to autoradiography in terms of speed of performance and topological resolution. Their limited sensitivity, however, has so far restricted their use to the detection of repeated sequences. Here we report single gene detection with a procedure using 2-acetylaminofluorene (AAF)-modified probes, immunoperoxidase cytochemistry and reflection-contrast microscopy. We confirmed the autoradiographic data on the localization of the human thyroglobulin (Tg) gene to the distal end of the long arm of chromosome 8. A mixture of cosmid cHT2-derived subclones of the 3' part of the Tg gene, 22.3 kilobase pairs (kbp) in total, was used as a hybridization probe. This procedure can be used to map other unique sequences, if genomic clones are available from which clones with an appropriate amount of inserts can be isolated. 相似文献
23.
Antidiuretic effects of oxytocin in the Brattleboro rat 总被引:1,自引:0,他引:1
J. Lyness A. G. Robinson M. N. Sheridan D. M. Gash 《Cellular and molecular life sciences : CMLS》1985,41(11):1444-1446
Summary The antidiuretic activity of oxytocin (OT) was measured in Brattleboro rats with congenital diabetes insipidus. A dose dependent antidiuretic response was found in animals receiving chronic infusions of 0.1 g/h, 1.0 g/h, and 5 g/h of OT. OT infused at the rate of 5 g/h over a 7-day period completely reversed the symptoms of diabetes insipidus. The results support the concept that OT serves as a weak agonist of vasopressin at the level of the kidney and at pharmacological levels exhibits antidiuretic activity. 相似文献
24.
Summary Visual determination of MSH-induced pigment migration in melanophores of small pieces ofAnolis carolinensis skin is standardized by first measuring photoelectrometrically the change in reflection/transmission of the whole dorsal skin in response to different hormone concentrations. This method allows the rapid and precise recording of time-response curves after photoaffinity labeling of MSH receptors or of dose-response curves of large series of synthetic compounds.Acknowledgments. We wish to thank Ms V. Jäggin, Ms C. Schulthess and Ms G. van Hees for excellent technical assistance, Dr. R. Andreatta, Ciba-Geigy AG, Basel, for his generous gift of -MSH and Prof. A Pletscher for his continuous interest. This work was supported by the Swiss National Science Foundation. 相似文献
25.
N. Akaike K. Hattori Y. Oomura D. O. Carpenter 《Cellular and molecular life sciences : CMLS》1985,41(1):70-71
Summary Using isolated, internally perfused bullfrog dorsal root ganglion cells we have studied the dose-response curves for -aminobutyric acid (GABA) in the presence of internally or externally applied GABA antagonists. With external application of antagonists the inhibition of the GABA current by bicuculline was competitive and that by picrotoxin was noncompetitive. Picrotoxin but not bicuculline blocked when internally perfused.To whom reprint requests should be addressed.Acknowledgments. We thank Drs S. Minakami and S. Yasui for helpful discussions and comments. 相似文献
26.
Jupiter's ring system has previously been described as being composed of a 'bright' narrow ring and an interior, vertically-extended halo. The one image which reveals this morphology most clearly is Voyager 2's parting shot of the Jupiter system, a wide-angle (WA) view of the ring ansa in forward-scattered light (FDS 20693.02). The bright ring is plainly visible, and the halo appears after slight contrast enhancement. By further enhancement of this image we have discovered an additional ring, which is far fainter than either of the (already faint) components previously identified, extending to a radius of 210,000 km. 相似文献
27.
J. R. Martinez N. Cassity S. Barker 《Cellular and molecular life sciences : CMLS》1987,43(9):1013-1015
Summary The -adrenergic agonist isoproterenol and prostaglandins E1 and E2 (but not F2) increased the cAMP content of rat submandibular acini in vitro, but only isoproterenol enhanced ouabain-sensitive86Rb (K) uptake. These findings suggest that cAMP is not involved in the activation of the Na, K pump in salivary cells. 相似文献
28.
M. Kashimata M. Hiramatsu N. Minami Jr N. Minami 《Cellular and molecular life sciences : CMLS》1987,43(2):191-192
Summary An enzyme immunoassay for mouse epidermal growth factor (EGF) involving a liquid phase double-antibody system was developed. The EGF--galactosidase conjugate prepared was stable for at least 8 months. By this method, EGF was detectable at a concentration as low as 20 pg per tube. The concentrations of EGF in various tissues of mice are also presented.This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan. 相似文献
29.
Pineal gland changes of rats exposed to heat 总被引:1,自引:0,他引:1
30.
Summary Metabolism of 26-hydroxycholesterol to 3-hydroxychol-5-en-24-oic acid and other C24-bile acids has been expected to occur by way of 3-hydroxycholest-5-en-26-oic acid in studies in vitro. 3-Hydroxycholest-5-en-26-oic acid was infused intravenously into bile fistula hamsters and the following C24-bile acids were identified: 3-hydroxychol-5-en-24-oic acid, lithocholic acid, chenodeoxycholic acid, and a small amount of cholic acid. 相似文献