全文获取类型
收费全文 | 17973篇 |
免费 | 100篇 |
国内免费 | 86篇 |
专业分类
系统科学 | 85篇 |
丛书文集 | 280篇 |
教育与普及 | 52篇 |
理论与方法论 | 72篇 |
现状及发展 | 8211篇 |
研究方法 | 810篇 |
综合类 | 8432篇 |
自然研究 | 217篇 |
出版年
2013年 | 140篇 |
2012年 | 248篇 |
2011年 | 490篇 |
2010年 | 119篇 |
2008年 | 313篇 |
2007年 | 355篇 |
2006年 | 322篇 |
2005年 | 353篇 |
2004年 | 414篇 |
2003年 | 309篇 |
2002年 | 313篇 |
2001年 | 526篇 |
2000年 | 545篇 |
1999年 | 372篇 |
1992年 | 279篇 |
1991年 | 250篇 |
1990年 | 250篇 |
1989年 | 246篇 |
1988年 | 255篇 |
1987年 | 262篇 |
1986年 | 273篇 |
1985年 | 372篇 |
1984年 | 251篇 |
1983年 | 222篇 |
1982年 | 178篇 |
1981年 | 229篇 |
1980年 | 248篇 |
1979年 | 606篇 |
1978年 | 462篇 |
1977年 | 467篇 |
1976年 | 346篇 |
1975年 | 374篇 |
1974年 | 526篇 |
1973年 | 431篇 |
1972年 | 468篇 |
1971年 | 503篇 |
1970年 | 672篇 |
1969年 | 556篇 |
1968年 | 532篇 |
1967年 | 524篇 |
1966年 | 460篇 |
1965年 | 346篇 |
1964年 | 104篇 |
1959年 | 166篇 |
1958年 | 305篇 |
1957年 | 234篇 |
1956年 | 225篇 |
1955年 | 179篇 |
1954年 | 201篇 |
1948年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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
82.
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
83.
S. S. Tobe R. P. Ruegg B. A. Stay F. C. Baker C. A. Miller D. A. Schooley 《Cellular and molecular life sciences : CMLS》1985,41(8):1028-1034
Summary Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of femaleDiploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instarD. punctata. Maximum values of 1500 ng/ml (6M) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH levels obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool inD. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool. 相似文献
84.
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
85.
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
86.
The significance of glycosylated proteins 总被引:15,自引:0,他引:15
87.
Pineal gland changes of rats exposed to heat 总被引:1,自引:0,他引:1
88.
Stereochemistry of cooperative effects in haemoglobin 总被引:136,自引:0,他引:136
M F Perutz 《Nature》1970,228(5273):726-739
89.
X-linked gene for testicular feminization in the mouse 总被引:38,自引:0,他引:38
90.
RNA synthesis during early development of the mouse 总被引:5,自引:0,他引:5