全文获取类型
收费全文 | 55212篇 |
免费 | 4574篇 |
国内免费 | 3971篇 |
出版年
2024年 | 117篇 |
2023年 | 696篇 |
2022年 | 1599篇 |
2021年 | 2741篇 |
2020年 | 1777篇 |
2019年 | 2153篇 |
2018年 | 2013篇 |
2017年 | 1532篇 |
2016年 | 2225篇 |
2015年 | 3304篇 |
2014年 | 3840篇 |
2013年 | 4199篇 |
2012年 | 4787篇 |
2011年 | 4559篇 |
2010年 | 2653篇 |
2009年 | 2471篇 |
2008年 | 2799篇 |
2007年 | 2463篇 |
2006年 | 2219篇 |
2005年 | 1813篇 |
2004年 | 1597篇 |
2003年 | 1435篇 |
2002年 | 1222篇 |
2001年 | 1094篇 |
2000年 | 940篇 |
1999年 | 909篇 |
1998年 | 595篇 |
1997年 | 582篇 |
1996年 | 549篇 |
1995年 | 482篇 |
1994年 | 445篇 |
1993年 | 372篇 |
1992年 | 525篇 |
1991年 | 441篇 |
1990年 | 381篇 |
1989年 | 294篇 |
1988年 | 274篇 |
1987年 | 224篇 |
1986年 | 158篇 |
1985年 | 207篇 |
1984年 | 139篇 |
1983年 | 113篇 |
1982年 | 98篇 |
1981年 | 71篇 |
1980年 | 62篇 |
1979年 | 82篇 |
1978年 | 76篇 |
1977年 | 53篇 |
1976年 | 52篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Aiyi Liu James F. Troendle Kai F. Yu Vivian W. Yuan 《Biometrical journal. Biometrische Zeitschrift》2004,46(6):760-768
We consider estimation after a group sequential test. An estimator that is unbiased or has small bias may have substantial conditional bias (Troendle and Yu, 1999, Coburger and Wassmer, 2001). In this paper we derive the conditional maximum likelihood estimators of both the primary parameter and a secondary parameter, and investigate their properties within a conditional inference framework. The method applies to both the usual and adaptive group sequential test designs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
74.
75.
Abstract: The leaf extracts of Populus nigra were collected and identified by steam distillation, air entrainment and gas chromatographic–mass spectrometric analysis. Electroantennograms were recorded from Helicoverpa armigera adults in response to the chemicals identified. Both aromatic compounds and green-leaf volatiles elicited strong responses. Field experiments revealed that the active compounds responsible for attracting H. armigera moths are mainly short-side-chain aromatic alcohols and aldehydes. We, for the first time, used agaropectin as the controlled-release matrix of insect attractants. A five-component lure containing all the aromatics without phenolics, mixed in the proportions as found in the steam distillate of the leaves collected in August, produced the best trap catch. The results showed that the volatiles of wilted leaves of P. nigra can attract H. armigera adults by feeding attraction. 相似文献
76.
77.
78.
Basic mechanical properties of retina in simple elongation 总被引:4,自引:0,他引:4
79.
Fang-Sheng Wu 《Planta》1987,171(3):346-357
The positively-charged fluorescent dye rhodamine 123 (r-123) specifically stains mitochondria in living plant protoplasts, suspensionculture cells, and root hairs. This dye functions as a vital stain and permits visualization of the localization, distribution and movement of the mitochondria. Dehydration of root hairs caused mitochondria to aggregate into clumps. Mitochondria were either homogenous or heterogeneous and were frequently seen to accumulate in the perinuclear regions of suspension-culture cells but not in those of protoplasts or root-hair cells. Dinitrophenol and high concentrations of ethyleneglycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid and KCl immediately eliminated fluorescence in r-123-stained mitochondria whereas ionomycin enhanced it. Treatment of seedlings with r-123 resulted in differential brightness of fluorescence in different tissues. Meristematic tissues, such as root and shoot tips, exhibited the brightest fluorescence. The cytotoxicity of r-123 in both germinating seedlings and suspension-culture cells was low. The specificity, sensitivity and low toxicity of r-123 should make it a useful tool in experiments designed to examine agents and conditions which affect the location, the physiological status or the viability of mitochondria.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethyl ether)N,N,N,N-tetraacetic acid
- DAPI
46-diamidino-2-phenylindole
- r-123
rhodamine 123 相似文献
80.
Changing Activity of Glucose-6-Phosphate Dehydrogenase from Pea Chloroplasts during Photosynthetic Induction 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Light inactivation of glucose 6-phosphate dehydrogenase is rapid and occurs before photosynthetic O2 evolution is measureable in intact chloroplasts. Likewise, dark activation is rapid. The major light induced change in the kinetic parameters of glucose 6-phosphate dehydrogenase is in maximal velocity. 相似文献