全文获取类型
收费全文 | 35052篇 |
免费 | 2845篇 |
国内免费 | 121篇 |
出版年
2021年 | 462篇 |
2020年 | 300篇 |
2019年 | 450篇 |
2018年 | 529篇 |
2017年 | 424篇 |
2016年 | 680篇 |
2015年 | 1110篇 |
2014年 | 1227篇 |
2013年 | 1750篇 |
2012年 | 1920篇 |
2011年 | 1820篇 |
2010年 | 1370篇 |
2009年 | 1095篇 |
2008年 | 1605篇 |
2007年 | 1560篇 |
2006年 | 1519篇 |
2005年 | 1366篇 |
2004年 | 1420篇 |
2003年 | 1352篇 |
2002年 | 1425篇 |
2001年 | 1052篇 |
2000年 | 944篇 |
1999年 | 884篇 |
1998年 | 494篇 |
1997年 | 463篇 |
1996年 | 375篇 |
1995年 | 391篇 |
1994年 | 299篇 |
1993年 | 357篇 |
1992年 | 596篇 |
1991年 | 566篇 |
1990年 | 540篇 |
1989年 | 479篇 |
1988年 | 398篇 |
1987年 | 375篇 |
1986年 | 373篇 |
1985年 | 400篇 |
1984年 | 405篇 |
1983年 | 358篇 |
1982年 | 286篇 |
1981年 | 300篇 |
1980年 | 266篇 |
1979年 | 325篇 |
1978年 | 282篇 |
1977年 | 302篇 |
1976年 | 281篇 |
1975年 | 280篇 |
1974年 | 278篇 |
1973年 | 250篇 |
1972年 | 204篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Phenotypic data on 203 Gram-negative non-fermentative bacteria of the Flavobacterium-Cytophaga group isolated from milk and butter were analyzed by numerical taxonomic techniques. Twenty reference strains including species of Flavobacterium, Cytophaga and strains of Pseudomonas paucimobilis were included in the study. Using the matching coefficient of Sokal & Michener with antibiotic susceptibility data included, 139 isolates were recovered in nine clusters. Six of these clusters were linked at or above the 85% S level while three were linked at or above the 79% S level. The largest cluster, representing 46.3% of the isolates, could be equated with Flavobacterium sp. Group IIb. Other clusters could be equated with Flavobacterium sp. L 16/1 (22.7% of isolates), F. balustinum (10.8% of isolates), F. breve (4.4%), F. multivorum (3.5%) and Cytophaga johnsonae (1.5%). The cluster resembling Flavobacterium sp. L 16/1 and a smaller unclassified cluster, were exceptional in being susceptible to the antibiotics cephalothin and penicillin G. 相似文献
32.
33.
F. Marsolat D. Tromson N. Tranchant P. Bergonzo F. Moignau L. De Carlan D. Lazaro M. Agelou C. Bassinet C. Huet S. Derreumaux M. Chea G. Boisserie I. Buchheit V. Marchesi 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2012
34.
Ruxandra Ion L. Telvi Jean-Louis Chaussain Jacques Patrick Barbet Manoel Nunes Anne Safar Marie-Odile Réthoré Marc Fellous Ken McElreavey 《Human genetics》1998,102(2):151-156
In 46,XY individuals, testes are determined by the activity of the SRY gene (sex-determining region Y), located on the short arm of the Ychromosome. The other genetic components of the cascade
that leads to testis formation are unknown and may be located on the Xchromosome or on the autosomes. Evidence for the existence
of several loci associated with failure of male sexual development is indicated by reports of 46,XY gonadal dysgenesis associated
with structural abnormalities of the Xchromosome or of autosomes (chromosomes9, 10, 11 and 17). In this report, we describe
the investigation of a child presenting with multiple congenital abnormalities, mental retardation and partial testicular
failure. The patient had a homogeneous de novo 46,XY,inv dup(9)(pter→p24.1::p21.1 →p23.3::p24.1→qter) chromosome complement.
No deletion was found by either cytogenetic or molecular analysis. The SRY gene and DSS region showed no abnormalities. Southern blotting dosage analysis with 9p probes and fluorescent in situ hybridisation data
indicated that the distal breakpoint of the duplicated fragment was located at 9p24.1, proximal to the SNF2 gene. We therefore suggest that a gene involved in normal testicular development and/or maintenance is present at this position
on chromosome 9.
Received: 20 January 1997 / Accepted: 5 November 1997 相似文献
35.
36.
37.
38.
39.
Graciela De Lara-Isassi Sergio Álvarez-Hernández Ligia Collado-Vides 《Journal of applied phycology》2000,12(1):45-52
Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity.
Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic,
if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species
were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were
moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for
extraction of toxic substances.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
40.
H. Elenga O. Peyron R. Bonnefille D. Jolly R. Cheddadi J. Guiot V. Andrieu S. Bottema G. Buchet J.-L. De Beaulieu A. C. Hamilton J. Maley R. Marchant R. Perez-Obiol M. Reille G. Riollet L. Scott H. Straka D. Taylor E. Van Campo A. Vincens F. Laarif H. Jonson 《Journal of Biogeography》2000,27(3):621-634
Pollen data from 18,000 14C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown. Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today. 相似文献