全文获取类型
收费全文 | 17774篇 |
免费 | 1521篇 |
国内免费 | 9篇 |
专业分类
19304篇 |
出版年
2023年 | 90篇 |
2022年 | 189篇 |
2021年 | 396篇 |
2020年 | 225篇 |
2019年 | 278篇 |
2018年 | 356篇 |
2017年 | 309篇 |
2016年 | 488篇 |
2015年 | 824篇 |
2014年 | 911篇 |
2013年 | 1075篇 |
2012年 | 1440篇 |
2011年 | 1315篇 |
2010年 | 878篇 |
2009年 | 837篇 |
2008年 | 1093篇 |
2007年 | 1109篇 |
2006年 | 984篇 |
2005年 | 1025篇 |
2004年 | 930篇 |
2003年 | 857篇 |
2002年 | 828篇 |
2001年 | 151篇 |
2000年 | 132篇 |
1999年 | 189篇 |
1998年 | 240篇 |
1997年 | 164篇 |
1996年 | 144篇 |
1995年 | 112篇 |
1994年 | 121篇 |
1993年 | 121篇 |
1992年 | 104篇 |
1991年 | 85篇 |
1990年 | 120篇 |
1989年 | 101篇 |
1988年 | 85篇 |
1987年 | 89篇 |
1986年 | 49篇 |
1985年 | 81篇 |
1984年 | 91篇 |
1983年 | 59篇 |
1982年 | 79篇 |
1981年 | 67篇 |
1980年 | 49篇 |
1979年 | 46篇 |
1978年 | 37篇 |
1977年 | 34篇 |
1976年 | 30篇 |
1975年 | 20篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Chang-Jie Jiang Alan G. Weeds Patrick J. Hussey 《The Plant journal : for cell and molecular biology》1997,12(5):1035-1043
The maize actin depolymerizing factor, ZmADF3, binds G-and F-actin, and increases in vitro actin dynamics. Polyclonal antibodies have been raised against ZmADF3 and these detect a single band of approximately 17 kDa in all maize tissues examined, with the exception of pollen. In the development of root hairs, the distribution of ZmADF3 is related to actin reorganization. In the early stages of hair development, ZmADF3 is distributed throughout the cytoplasm. As the hair emerges and the microfilament bundles redirect to the outgrowth there is a simultaneous redistribution of ZmADF3 which now concentrates at the tip of the emerging hair and remains in this position as elongation proceeds. These observations show that ZmADF3 localizes to a region where actin is being remodelled during tip growth. After cytochalasin D treatment which disrupts actin filaments, short rods of ZmADF3 and actin appear in the nucleus suggesting that ZmADF3 may function by guiding actin to sites of actin polymerization. 相似文献
112.
Ave Patrick Colucci-Guyon Emma Babinet Charles Huerre Michel-Rene 《Transgenic research》1997,6(1):37-40
The Escherichia coli -galactosidase gene is frequently used as a reporter gene in transgenic studies because its activity can be easily detected at the cellular level. Here we report a procedure for monitoring -galactosidase activity directly in tissue sections, which involves the use of a mixture of ethanol and poly-ethylene-glycol as a fixative (Kryofix) and a special paraffin characterized by a lower fusion point of 42 °C. After embedding and cutting, the sections are stained by the chromogenic substrate 5-bromo-4-chloro-3-indoyl--d galactopyranoside (X-Gal). This procedure allows both the retention of a high level of -galactosidase activity and the preservation of good tissue morphology. Furthermore, it can be combined with immunohistochemical methods to detect other cellular components without compromising reporter gene detection 相似文献
113.
George V. Triantaphyllidis Godelieve R. J. Criel Theodore J. Abatzopoulos Patrick Sorgeloos 《Hydrobiologia》1997,357(1-3):155-163
Eleven morphometric and one meristic character in 15 parthenogeneticArtemia populations have been studied by using discriminant andcluster analysis as well as scanning electron microscopy.Discriminant analysis revealed five main groups of morphologicalpatterns: (i) the coastal Chinese populations together with apopulation from Kazakhstan, (ii) the inland Chinese salt lakepopulations, (iii) the Greek populations, (iv) one African populationfrom Namibia and (v) a Chinese population from Xuyu (Jiangsuprovince). Cluster analysis was not always in agreement withdiscriminant analysis and these results are discussed. 相似文献
114.
Pickering Gisele P.; Fellmann Nicole; Morio Beatrice; Ritz Patrick; Amonchot Aime; Vermorel Michel; Coudert Jean 《Journal of applied physiology》1997,83(4):1300-1306
Pickering, Gisèle P., Nicole Fellmann, BéatriceMorio, Patrick Ritz, Aimé Amonchot, Michel Vermorel, and JeanCoudert. Effects of endurance training on the cardiovascularsystem and water compartments in elderly subjects. J. Appl. Physiol. 83(4): 1300-1306, 1997.Theeffects of endurance training on the water compartments and thecardiovascular system were determined in 10 elderly subjects [age62 ± 2 yr, pretraining maximal oxygen consumption(O2 max)/kg = 25 ± 2 ml · min1 · kg1body wt]. They trained on a cycloergometer 3 times/wk for 16 wk(50-80%O2 max,then 80-85%O2 max). They werechecked at 8 wk, 16 wk, and 4 mo after detraining. Training improvedO2 max (+16%) andinduced plasma volume expansion (+11%). No change in total body water,extracellular fluid, interstitial and intracellular fluid volumes,fat-free mass, and body weight was detected in this small sample withtraining. Body fat mass decreased (2.1 ± 2.2 kg).Echocardiography at rest showed increased fractional shortening andejection fraction and decreased left ventricular end-systolic dimension(P < 0.05). Blood volume expansioncorrelates with cardiac contractility and has an impact on cardiacfunction. These improvements are precarious, however, and arecompletely lost after 4 mo of detraining, when elderly subjects losethe constraints and the social stimulation of the imposed protocol. 相似文献
115.
Sublocalization of an Ataxia-Telangiectasia Gene Distal to D11S384 by Ancestral Haplotyping In Costa Rican Families 总被引:8,自引:4,他引:4 下载免费PDF全文
Nancy Uhrhammer Ethan Lange Oscar Porras Arash Naeim Xiaoguang Chen Sepideh Sheikhavandi Sujata Chiplunkar Lan Yang Sugandha Dandekar Teresa Liang Nima Patel Sharon Teraoka Nitin Udar Nidia Calvo Patrick Concannon Kenneth Lange Richard A. Gatti 《American journal of human genetics》1995,57(1):103-111
In an effort to localize a gene for ataxia-telangiectasia (A-T), we have genotyped 27 affected Costa Rican families, with 13 markers, in the chromosome 11q22-23 region. Significant linkage disequilibrium was detected for 9/13 markers between D11S1816 and D11S1391. Recombination events observed in these pedigrees places A-T between D11S1819 and D11S1960. One ancestral haplotype is common to 24/54 affected chromosomes and roughly two-thirds of the families. Inferred (ancestral) recombination events involving this common haplotype in earlier generations suggest that A-T is distal to D11S384 and proximal to D11S1960. Several other common haplotypes were identified, consistent with multiple mutations in a single gene. When considered together with all other evidence, this study further sublocalizes the major A-T locus to ≈200 kb, between markers S384 and S535. 相似文献
116.
The purpose of this investigation was to determine whether Madurella mycetomatis, the most frequent agent of eumycotic mycetomas, produces siderophores and synthesizes new outer membrane proteins under iron-starvation conditions. Siderophore production, only of the hydroxamate type, was demonstrated in all nine strains tested. It was regulated by extracellular iron concentrations. Under iron-restricted conditions, M. mycetomatis expressed various outer membrane iron-regulated proteins, particularly of 24-kilodalton, that may participate in iron metabolism. 相似文献
117.
Characterization of Superoxide dismutase genes from Gram-positive bacteria by polymerase chain reaction using degenerate primers 总被引:13,自引:0,他引:13
Abstract An internal fragment representing approximately 85% of sod genes from seven Gram-positive bacteria was amplified by using degenerate primers in a polymerase chain reaction assay. The DNA sequences of sod polymerase chain reaction products from Clostridium perfringens, Enterococcus faecalis, Enterococcus faecium, Lactococcus lactis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae , and Streptococcus pyogenes were determined. Comparisons of their deduced amino acid sequences with those of the corresponding regions of the SOD proteins from Bacillus stearothermophilus, Listeria monocytogenes , and Streptococcus mutans revealed strong relatedness. Phylogenetic analysis of SOD peptides showed that members of the genera Streptococcus and those of the genera Enterococcus constitute two well-supported monophyletic groups. The method described in this study provides a means for easy recovery of sod genes and the construction of sod mutants of various Gram-positive pathogens. 相似文献
118.
Patrick H. Brown Steven A. Weinbaum Geno A. Picchioni 《Trees - Structure and Function》1995,9(3):158-164
The influence of alternate bearing on nutrient utilization and total tree nutrient content was investigated in mature pistachio
(Pistacia vera L. cv Kerman trees). Removal of N, P and Zn in fruit and abscised leaves of cropping (‘on’) trees averaged 5, 6, and 2 times,
respectively, the removal in abscised leaflets of the non-fruiting, ‘off’ year trees. One hundred and thirty-five kg N, 131
kg K, 86 kg Ca, 39 kg Mg and 18 kg P per hectare were removed in fruits and abscised leaves in ‘on’ year trees. Tree nutrient
contents and, presumably, the size of nutrient storage pools in dormant trees varied between ‘on’ and ‘off’ years. There was
22% and 14% more N and P, respectively, in dormant trees following ‘off’ than ‘on’ years. The greater N and P accumulation
in ‘off’ year trees is depleted in support of the large fruit demand for N and P during ‘on’ years. In contrast to N and P,
there was greater K and Ca accumulation in perennial tree parts during ‘on’ years than during ‘off’ years. The greater K accumulation
in perennial tree parts and approximately 30% greater removal of K in annual organs during ‘on’ than ‘off’ years suggests
that K uptake could be 4 times higher in ‘on’ year trees than in (non-cropping), ‘off’ year trees. 相似文献
119.
120.