全文获取类型
收费全文 | 4316篇 |
免费 | 461篇 |
国内免费 | 235篇 |
专业分类
5012篇 |
出版年
2024年 | 16篇 |
2023年 | 165篇 |
2022年 | 115篇 |
2021年 | 171篇 |
2020年 | 199篇 |
2019年 | 244篇 |
2018年 | 204篇 |
2017年 | 204篇 |
2016年 | 166篇 |
2015年 | 166篇 |
2014年 | 206篇 |
2013年 | 256篇 |
2012年 | 160篇 |
2011年 | 152篇 |
2010年 | 138篇 |
2009年 | 189篇 |
2008年 | 196篇 |
2007年 | 206篇 |
2006年 | 176篇 |
2005年 | 167篇 |
2004年 | 164篇 |
2003年 | 158篇 |
2002年 | 141篇 |
2001年 | 119篇 |
2000年 | 121篇 |
1999年 | 95篇 |
1998年 | 56篇 |
1997年 | 53篇 |
1996年 | 35篇 |
1995年 | 35篇 |
1994年 | 41篇 |
1993年 | 39篇 |
1992年 | 39篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 37篇 |
1987年 | 41篇 |
1986年 | 21篇 |
1985年 | 30篇 |
1984年 | 22篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1971年 | 6篇 |
排序方式: 共有5012条查询结果,搜索用时 15 毫秒
21.
22.
M. J. A. Werger 《Plant Ecology》1982,49(3):187-190
Editing of community data matrices is complementary to analyzing data by multivariate techniques of classification and ordination in the overall task of data analysis. A computer program, DATAEDIT, is described that can perform numerous editing functions, including data transformation, deletion of certain species or samples, deletion of rare species, deletion of outliers, separation of disjunet sample groups, reordering of the species or samples of a data matrix, and the formation of composite samples or of sample subsets. DATAEDIT can use the information in a nonhierarchical or hierarchical classification, and includes its own internal routine for reciprocal averaging ordination.We appreciate valuable suggestions from the late Robert H. Whittaker, and from Philip Dixon, David Hieks, Laura Huenneke, Linda Olsvig-whittaker, and Mark Wilson. Mark O. Hill kindly supplied a fast subroutine for reciprocal averaging. 相似文献
23.
Linear rank tests with right censored data 总被引:6,自引:0,他引:6
24.
Multivariate binary discrimination by the kernel method 总被引:10,自引:0,他引:10
25.
The sequences of the internal transcribed spacer (ITS) region of 18S–26S nrDNA for a sample of 16 taxa from theInuleae s. str. and two outgroup taxa are analysed cladistically with PAUP. A consensus tree of the four most parsimonious cladograms is presented. Three different tests of cladogram stability are conducted (Bremer support, parsimony jackknifing and bootstrapping); all tests indicate a high degree of support for the basal nodes of the tree. The ITS phylogeny of the tribe is compared with previous hypotheses based on morphological data. The position ofAnisopappus as sister group to the rest of the tribe is supported by the molecular data, but the proposed subdivision ofInuleae s. str. into a paleate grade group and an epaleate clade is not. The interpretation of the character evolution of, e.g. receptacular paleae and pappus features within the tribe is discussed. 相似文献
26.
Wong L 《Briefings in bioinformatics》2002,3(4):389-404
The process of building a new database relevant to some field of study in biomedicine involves transforming, integrating and cleansing multiple data sources, as well as adding new material and annotations. This paper reviews some of the requirements of a general solution to this data integration problem. Several representative technologies and approaches to data integration in biomedicine are surveyed. Then some interesting features that separate the more general data integration technologies from the more specialised ones are highlighted. 相似文献
27.
Istem Fer Anthony K. Gardella Alexey N. Shiklomanov Eleanor E. Campbell Elizabeth M. Cowdery Martin G. De Kauwe Ankur Desai Matthew J. Duveneck Joshua B. Fisher Katherine D. Haynes Forrest M. Hoffman Miriam R. Johnston Rob Kooper David S. LeBauer Joshua Mantooth William J. Parton Benjamin Poulter Tristan Quaife Ann Raiho Kevin Schaefer Shawn P. Serbin James Simkins Kevin R. Wilcox Toni Viskari Michael C. Dietze 《Global Change Biology》2021,27(1):13-26
In an era of rapid global change, our ability to understand and predict Earth's natural systems is lagging behind our ability to monitor and measure changes in the biosphere. Bottlenecks to informing models with observations have reduced our capacity to fully exploit the growing volume and variety of available data. Here, we take a critical look at the information infrastructure that connects ecosystem modeling and measurement efforts, and propose a roadmap to community cyberinfrastructure development that can reduce the divisions between empirical research and modeling and accelerate the pace of discovery. A new era of data‐model integration requires investment in accessible, scalable, and transparent tools that integrate the expertise of the whole community, including both modelers and empiricists. This roadmap focuses on five key opportunities for community tools: the underlying foundations of community cyberinfrastructure; data ingest; calibration of models to data; model‐data benchmarking; and data assimilation and ecological forecasting. This community‐driven approach is a key to meeting the pressing needs of science and society in the 21st century. 相似文献
28.
29.
Correlated binary regression using a quadratic exponential model 总被引:5,自引:0,他引:5
30.