全文获取类型
收费全文 | 2022篇 |
免费 | 158篇 |
专业分类
2180篇 |
出版年
2023年 | 16篇 |
2022年 | 23篇 |
2021年 | 59篇 |
2020年 | 57篇 |
2019年 | 63篇 |
2018年 | 67篇 |
2017年 | 69篇 |
2016年 | 90篇 |
2015年 | 115篇 |
2014年 | 129篇 |
2013年 | 165篇 |
2012年 | 163篇 |
2011年 | 135篇 |
2010年 | 80篇 |
2009年 | 73篇 |
2008年 | 91篇 |
2007年 | 85篇 |
2006年 | 87篇 |
2005年 | 61篇 |
2004年 | 74篇 |
2003年 | 56篇 |
2002年 | 54篇 |
2001年 | 47篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 4篇 |
排序方式: 共有2180条查询结果,搜索用时 0 毫秒
91.
The incidence of apoptosis and nuclear instability, including the incidence of catastrophic death, were investigated in benzo[a]pyrene (BP)-transformed human breast epithelial cells (BP1-E cell line) after microcell-mediated transfer of chromosomes 11 and 17. Since the introduction of normal chromosomes 11 and 17 into tumorigenic human breast BP1-E cells reverts some of these cells' characteristics (especially those affected by microsatellite instabilities and loss of heterozygosity) to those of parental non-transformed MCF-10F cells, it was expected that the cell death rates would also be affected by this treatment. The transfer of the mentioned chromosomes, especially chromosome 17, to tumorigenic BP1-E cells increased the apoptotic ratios and decreased the nuclear instability ratios, thus showing that the microsatellite instability and loss of heterozygosity induced by BP in these chromosomes of MCF-10F cells affect the control of cell death mechanisms. 相似文献
92.
Nones K Ledur MC Zanella EL Klein C Pinto LF Moura AS Ruy DC Baron EE Ambo M Campos RL Boschiero C Burt DW Coutinho LL 《Animal genetics》2012,43(5):570-576
Major objectives of the poultry industry are to increase meat production and to reduce carcass fatness, mainly abdominal fat. Information on growth performance and carcass composition are important for the selection of leaner meat chickens. To enhance our understanding of the genetic architecture underlying the chemical composition of chicken carcasses, an F2 population developed from a broiler × layer cross was used to map quantitative trait loci (QTL) affecting protein, fat, water and ash contents in chicken carcasses. Two genetic models were applied in the QTL analysis: the line‐cross and the half‐sib models, both using the regression interval mapping method. Six significant and five suggestive QTL were mapped in the line‐cross analysis, and four significant and six suggestive QTL were mapped in the half‐sib analysis. A total of eleven QTL were mapped for fat (ether extract), five for protein, four for ash and one for water contents in the carcass using both analyses. No study to date has reported QTL for carcass chemical composition in chickens. Some QTL mapped here for carcass fat content match, as expected, QTL regions previously associated with abdominal fat in the same or in different populations, and novel QTL for protein, ash and water contents in the carcass are presented here. The results described here also reinforce the need for fine mapping and to perform multi‐trait analyses to better understand the genetic architecture of these traits. 相似文献
93.
94.
Contrasting Effects of Fire on Arboreal and Ground‐Dwelling Ant Communities of a Neotropical Savanna
Ants are a dominant group in tropical savannas and here we examined the responses of the arboreal and ground‐dwelling ant fauna to a fire in a Neotropical savanna (cerrado) reserve in Central Brazil. Ants were collected using pitfall traps and baits placed in trees and on the ground beneath each tree. Of the 36 trees marked along two transects, half (from each transect) were burned and half not. The same trees were sampled 1 wk before and again 3 and 12 mo after the fire. Rarefaction curves and ordination analyses using data from all trees from each side of each transect indicated that overall ant species richness and composition did not change after fire. Fire, however, reduced the mean number of ant species per tree, and increased the mean number of species on the ground. Fire increased the average abundance of specialist predators, Camponotini, and opportunistic species, and decreased that of arboreal specialists. Changes in the ground‐dwelling fauna were only detected 12 mo after the fire, while those in the arboreal fauna occurred earlier and were no longer apparent 12 mo after the fire. We suggest that these contrasting results represent mainly an indirect response of the ant communities to fire‐induced changes in vegetation. Given the temporary and small scale nature of the effects detected and the overall resilience of the ant fauna, our results indicate that a single fire in the cerrado vegetation does not greatly impact the structure of ant communities in the short term. 相似文献
95.
H. Campos de Quiros R. Magrath D. McCallum J. Kroymann D. Scnabelrauch T. Mitchell-Olds R. Mithen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(3):429-437
QTL mapping of glucosinolates in a RI population derived from an F1 hybrid between the Arabidopsis thaliana ecotypes Columbia and Landsberg erecta identified a single major QTL coincident with the GSL-ELONG locus which regulates side chain elongation. Physical mapping and sequencing identified two members of an isopropylmalate
synthase-like gene family within the region of maximum LOD score for the QTL and the GSL-ELONG non-recombinant region. These genes are prime candidates for regulating glucosinolate biosynthesis.
Received: 19 November 1999 / Accepted: 16 December 1999 相似文献
96.
Jacqueline de Melo Barcelar Andrea Aliverti Catarina Rattes Maria Eduarda Ximenes Shirley Lima Campos Daniella Cunha Brand?o Guilherme Fregonezi Armèle Dornelas de Andrade 《PloS one》2014,9(11)
Objective
To analyze in obese women the acute effects of the breath stacking technique on thoraco-abdominal expansion.Design and Methods
Nineteen obese women (BMI≥30 kg/m2) were evaluated by anthropometry, spirometry and maximal respiratory muscle pressures and successively analyzed by Opto-Electronic Plethysmography and a Wright respirometer during quiet breathing and breath stacking maneuvers and compared with a group of 15 normal-weighted healthy women. The acute effects of the maneuvers were assessed in terms of total and compartmental chest wall volumes at baseline, end of the breath stacking maneuver and after the maneuver. Obese subjects were successively classified into two groups, accordingly to the response during the maneuver, group 1 = prevalent rib cage or group 2 = abdominal expansion.Results
Age was significantly lower in group 1 than group 2. When considering the two obese groups, FEV1 was lower and minute ventilation was higher only in group 2 compared to controls group. During breath stacking, inspiratory capacity was significant differences in obese subjects with a smaller expansion of the pulmonary rib cage and a greater expansion of the abdomen compared to controls and also between groups 1 and 2. A significant inverse linear relationship was found between age and inspiratory capacity of the pulmonary rib cage but not of the abdomen.Conclusions
In obese women the maximal expansion of the rib cage and abdomen is influenced by age and breath stacking maneuver could be a possible therapy for preventing respiratory complications. 相似文献97.
98.
Eduardo G. Mendonça Rafael de Almeida Barros Gláucia Cordeiro Carolina R. da Silva Welligton G. Campos Joel A. de Oliveira Maria G. de Almeida Oliveira 《Archives of insect biochemistry and physiology》2020,103(1):e21637
Anticarsia gemmatalis represents a relevant factor for lowering soybean and other legume crop productivities. Protease inhibitors affect protein degradation and reduce the availability of amino acids, impairing the development and survival of insect pests. To evaluate the possible use of proteinaceous protease inhibitors in the management of this pest, the activities of midgut proteases and the growth and development of A. gemmatalis larvae exposed to soybean Bowman–Birk trypsin-chymotrypsin inhibitor (SBBI) and soybean Kunitz trypsin inhibitor (SKTI) were determined. The survival curves obtained using Kaplan–Meier estimators indicated that SKTI and SBBI stimulated larval survival. However, the development of A. gemmatalis was delayed, and prepupal weight decreased in the presence of both inhibitors. The results showed that SKTI and SBBI inhibited the trypsin-like and total proteolytic activities of larvae on the 12th day after eclosion. On the 15th day after eclosion, larvae exposed to SKTI increased the activities of trypsin and total proteases. Although SKTI and SBBI did not affect the survival of the insect, they had effects on midgut proteases in a stage wherein A. gemmatalis fed voraciously, increased the larval cycle, and decreased prepupal weight. These findings provide baseline information about the potential of proteinaceous protease inhibitors to manage the velvetbean caterpillar, avoiding chemical pesticides. 相似文献
99.
100.
We study the process of adaptation in a spatially structured asexual haploid population. The model assumes a local competition
for replication, where each organism interacts only with its nearest neighbors. We observe that the substitution rate of beneficial
mutations is smaller for a spatially structured population than that seen for populations without structure. The difference
between structured and unstructured populations increases as the adaptive mutation rate increases. Furthermore, the substitution
rate decreases as the number of neighbors for local competition is reduced. We have also studied the impact of structure on
the distribution of adaptive mutations that fix during adaptation. 相似文献