全文获取类型
收费全文 | 38391篇 |
免费 | 16535篇 |
国内免费 | 6篇 |
专业分类
54932篇 |
出版年
2023年 | 48篇 |
2022年 | 190篇 |
2021年 | 615篇 |
2020年 | 2327篇 |
2019年 | 3865篇 |
2018年 | 4016篇 |
2017年 | 4265篇 |
2016年 | 4409篇 |
2015年 | 4463篇 |
2014年 | 4251篇 |
2013年 | 4789篇 |
2012年 | 2642篇 |
2011年 | 2387篇 |
2010年 | 3598篇 |
2009年 | 2344篇 |
2008年 | 1394篇 |
2007年 | 1011篇 |
2006年 | 970篇 |
2005年 | 961篇 |
2004年 | 911篇 |
2003年 | 875篇 |
2002年 | 860篇 |
2001年 | 427篇 |
2000年 | 319篇 |
1999年 | 293篇 |
1998年 | 157篇 |
1997年 | 135篇 |
1996年 | 119篇 |
1995年 | 138篇 |
1994年 | 103篇 |
1993年 | 146篇 |
1992年 | 123篇 |
1991年 | 84篇 |
1990年 | 102篇 |
1989年 | 75篇 |
1988年 | 72篇 |
1987年 | 71篇 |
1986年 | 62篇 |
1985年 | 75篇 |
1984年 | 99篇 |
1983年 | 76篇 |
1982年 | 105篇 |
1981年 | 86篇 |
1980年 | 72篇 |
1979年 | 53篇 |
1978年 | 57篇 |
1977年 | 44篇 |
1975年 | 44篇 |
1974年 | 69篇 |
1973年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Internode length in Pisum. I. The effect of the Le/le gene difference on endogenous gibberellin-like substances 总被引:2,自引:0,他引:2
The allelopathic potential of the dry fruits of Washingtonia filifera (L. Linden) H. Wendl. was investigated. Leachates from fruits inhibited the germination of lettuce, wheat, red cabbage and cucumber seeds. The inhibitory effect was partly neutralized by kinetin (20 mg 1−1 ) and gibberellic acid (50 mg 1−1 ). The effect of kinetin was more pronounced at 25°C than at 20°C. Substances inhibiting germination were localized in the pericarp of the fruit and were resistant to high temperature. 相似文献
5.
Ian H. Frasher Timothy Coolbear Sailen Mookerjea 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,799(2):102-105
Induction of inflammation by turpentine injection caused 1.5–2-fold increase of both sialy- and galactosyltransferase activity in liver homogenates. The effect was apparent after 12 h turpentine treatment. Serum sialytransferase activity started to increase in the inflamed rats after 18 h, reaching a maximum of 4-fold at 48 h. In contrast, galactosyltransferase activity in serum showed no significant increase. The coordinated and temporal increase of sialytransferase activity in liver and serum suggest involvement of a specific mechanism for the preferential release of this enzyme into serum. 相似文献
6.
The RAINFOR database: monitoring forest biomass and dynamics 总被引:1,自引:0,他引:1
Problem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis. Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project. Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage. 相似文献
7.
Thirteen polymorphic microsatellite loci were developed for blowflies for use in studies of genetic differentiation in wild populations of Lucilia illustris, to detect the possible occurrence of bottlenecks and to study changes in genetic variation in laboratory populations of Lucilia sericata following artificial bottlenecks. In this preliminary study it was revealed that heterozygosity was lower than expected in wild populations and genetic variation had been lost in the laboratory population despite being kept at a large size. 相似文献
8.
9.
10.
Francisco Gutirrez‐Corchero M. Victoria Arruga Lourdes Sanz Cristina García M. Angeles Hernndez Francisco Campos 《Molecular ecology resources》2002,2(1):75-77
FTA® cards were used for long‐term storage of avian blood samples. Blood DNA was extracted by a simple method and used in PCR for sex identification of adult and nestling Great Grey Shrikes Lanius excubitor. 相似文献