全文获取类型
收费全文 | 10136篇 |
免费 | 752篇 |
国内免费 | 1篇 |
出版年
2023年 | 69篇 |
2022年 | 99篇 |
2021年 | 293篇 |
2020年 | 186篇 |
2019年 | 213篇 |
2018年 | 249篇 |
2017年 | 213篇 |
2016年 | 348篇 |
2015年 | 568篇 |
2014年 | 621篇 |
2013年 | 700篇 |
2012年 | 904篇 |
2011年 | 825篇 |
2010年 | 524篇 |
2009年 | 461篇 |
2008年 | 644篇 |
2007年 | 577篇 |
2006年 | 537篇 |
2005年 | 465篇 |
2004年 | 424篇 |
2003年 | 352篇 |
2002年 | 360篇 |
2001年 | 72篇 |
2000年 | 57篇 |
1999年 | 61篇 |
1998年 | 76篇 |
1997年 | 50篇 |
1996年 | 47篇 |
1995年 | 59篇 |
1994年 | 41篇 |
1993年 | 31篇 |
1992年 | 64篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 43篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 31篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 27篇 |
1980年 | 27篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1973年 | 23篇 |
1971年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Hugo R. Permingeat Maria V. Romagnoli Juliana I. Sesma Ruben H. Vallejos 《Plant Molecular Biology Reporter》1998,16(1):89-89
An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase. 相似文献
2.
3.
4.
5.
6.
7.
Nicolas Delaleu Heike Immervoll Janet Cornelius Roland Jonsson 《Arthritis research & therapy》2008,10(1):R22
Introduction
Sj?gren's syndrome (SS) is a systemic autoimmune disease that mainly targets the exocrine glands. The aim of this study was to investigate the involvement of 87 proteins measured in serum and 75 proteins analyzed in saliva in spontaneous experimental SS. In addition, we intended to compute a model of the immunological situation representing the overt disease stage of SS. 相似文献8.
Pablo Manrique-Saide Sergio Ibáñez-Bernal Hugo Delfín-González Victor Parra Tabla 《Medical and veterinary entomology》1998,12(4):386-390
Abstract .The effect of the introduction of the entomophagous copepod Mesocyclops longisetus (Acuacultura F.C.B. strain) on the survival of Aedes aegypti immature stages in car tyres was evaluated under semi-natural conditions in the municipality of Merida, Yucatan, Mexico. Life tables were constructed for the immature stages of the mosquito in the presence and absence of M. longisetus , and the survival data were compared using log–linear models. The data set was adjusted using the GLIM statistical package and the quality of adjustment was evaluated with a chi-squared test . Survivorship curves were constructed for each treatment.
In the absence of M. longisetus , the survivorship of Ae. aegypti immature stages averaged 9%. The highest mortality rate was observed during the fourth larval instar (54%) and the resulting survival pattern corresponded to a type II survivorship curve. The mortality rate of Ae. aegypti first-instar larvae (fifty per tyre) increased more than 200-fold in the presence of M. longisetus (twenty per tyre) and the highest mortality was during the first two larval instars, where it reached 98.9%, with a resulting survivorship of 0.2%. Overall mortality was sixfold greater in the presence of the copepod than in its absence. The survival pattern of immature stages of Ae. aegypti in the presence of the copepod corresponded to a type III survivorship curve. As M. longisetus was so effective against Ae. aegypti immature stages in tyres under semi-natural conditions, its long-term effectiveness should be evaluated under socially and ecologically realistic field conditions in Mexico. 相似文献
In the absence of M. longisetus , the survivorship of Ae. aegypti immature stages averaged 9%. The highest mortality rate was observed during the fourth larval instar (54%) and the resulting survival pattern corresponded to a type II survivorship curve. The mortality rate of Ae. aegypti first-instar larvae (fifty per tyre) increased more than 200-fold in the presence of M. longisetus (twenty per tyre) and the highest mortality was during the first two larval instars, where it reached 98.9%, with a resulting survivorship of 0.2%. Overall mortality was sixfold greater in the presence of the copepod than in its absence. The survival pattern of immature stages of Ae. aegypti in the presence of the copepod corresponded to a type III survivorship curve. As M. longisetus was so effective against Ae. aegypti immature stages in tyres under semi-natural conditions, its long-term effectiveness should be evaluated under socially and ecologically realistic field conditions in Mexico. 相似文献
9.
10.
Eighty-five catalase- and oxidase-positive Gram-negative rods and cocci susceptible to penicillin G were isolated from a variety of food sources. The phenotypic relationships of these isolates with reference cultures of Bergeyella -like, Chryseobacterium, Empedobacter, Myroides , Moraxella , Sphingobacterium and Weeksella -like strains were examined by numerical taxonomy. Seventy-three isolates were recovered in five groups; 80% of the isolates clustered in groups 1, 2 and 3 and produced indole, bearing a strong resemblance to Weeksella and Bergeyella . They could not, however, be regarded as belonging to the known species of W. virosa and B. zoohelcum . It is suggested that three species may be necessary to accommodate the environmental Weeksella - or Bergeyella -like bacteria. The isolates in groups 4 and 5 had white colonies and were unable to produce indole, in this way resembling the Moraxella genus. 相似文献