全文获取类型
收费全文 | 17156篇 |
免费 | 542篇 |
国内免费 | 4篇 |
专业分类
17702篇 |
出版年
2021年 | 157篇 |
2020年 | 151篇 |
2019年 | 193篇 |
2018年 | 414篇 |
2017年 | 365篇 |
2016年 | 483篇 |
2015年 | 442篇 |
2014年 | 579篇 |
2013年 | 850篇 |
2012年 | 726篇 |
2011年 | 861篇 |
2010年 | 523篇 |
2009年 | 362篇 |
2008年 | 603篇 |
2007年 | 695篇 |
2006年 | 713篇 |
2005年 | 622篇 |
2004年 | 519篇 |
2003年 | 583篇 |
2002年 | 484篇 |
2001年 | 406篇 |
2000年 | 339篇 |
1999年 | 255篇 |
1998年 | 128篇 |
1992年 | 241篇 |
1991年 | 235篇 |
1990年 | 190篇 |
1989年 | 230篇 |
1988年 | 242篇 |
1987年 | 256篇 |
1986年 | 228篇 |
1985年 | 268篇 |
1984年 | 215篇 |
1983年 | 175篇 |
1980年 | 91篇 |
1979年 | 250篇 |
1978年 | 169篇 |
1977年 | 152篇 |
1976年 | 144篇 |
1975年 | 174篇 |
1974年 | 279篇 |
1973年 | 267篇 |
1972年 | 259篇 |
1971年 | 251篇 |
1970年 | 258篇 |
1969年 | 248篇 |
1968年 | 200篇 |
1967年 | 201篇 |
1966年 | 178篇 |
1965年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
D. Lewczuk A. Bereznowski M. Hecold M. Frąszczak A. Ruść A. Korwin-Kossakowska J. Szyda S. Kamiński 《Journal of applied genetics》2018,59(2):225-230
Horses lose potential opportunities because of health problems. Available breeding strategies are not effective enough, probably also because of the different definition used and its genetic usefulness. The aim of the study was to compare the genetic background estimated by the genome-wide association study (GWAS) for osteochondrosis using two different scaling osteochondrosis (OC)/healthy and osteochondrosis dissecans (OCD)/healthy systems for evaluating the disease status of investigated fetlock joints. Two hundred one Warmblood horses trained for performance tests (87 stallions and 114 mares) were phenotyped and genotyped. Four fetlock x-ray images per horse were collected using the RTG Girth HF 80 and Vet Scan ray 3600. The DNA of each horse was genotyped using the BeadChip 70K. To identify SNPs that significantly affect the probability of osteochondrosis, two different methods were applied: the Cochran-Armitage test based on an additive mode of inheritance and logistic regression. The genetic background for osteochondrosis, expressed in the number of SNPs found with significant associations with osteochondrosis, was higher by evaluation in the scale of OCD/healthy horses (16 SNPs on several chromosomes mainly on the ECA1 and ECA10) than OC/healthy (2 SNPs on the ECA15 and one SNP on the ECA10). Detailed definition of osteochondrosis is needed in breeding and in veterinary practice. The genetic background for osteochondrosis and osteochondrosis dissecans seems not the same. Suggestive SNPs could be the candidate markers for osteochondrosis but should be checked on a larger population before usage. 相似文献
42.
Dagmara Panas Urszula Malinowska Tadeusz Piotrowski Jaros?aw ?ygierewicz Piotr Suffczyński 《PloS one》2013,8(4)
Spindles - a hallmark of stage II sleep - are a transient oscillatory phenomenon in the EEG believed to reflect thalamocortical activity contributing to unresponsiveness during sleep. Currently spindles are often classified into two classes: fast spindles, with a frequency of around 14 Hz, occurring in the centro-parietal region; and slow spindles, with a frequency of around 12 Hz, prevalent in the frontal region. Here we aim to establish whether the spindle generation process also exhibits spatial heterogeneity. Electroencephalographic recordings from 20 subjects were automatically scanned to detect spindles and the time occurrences of spindles were used for statistical analysis. Gamma distribution parameters were fit to each inter-spindle interval distribution, and a modified Wald-Wolfowitz lag-1 correlation test was applied. Results indicate that not all spindles are generated by the same statistical process, but this dissociation is not spindle-type specific. Although this dissociation is not topographically specific, a single generator for all spindle types appears unlikely. 相似文献
43.
44.
Jacek Kęsy Beata Maciejewska Magdalena Sowa Magdalena Szumilak Krzysztof Kawałowski Maja Borzuchowska Jan Kopcewicz 《Plant Growth Regulation》2008,55(1):43-50
It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production
is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of
IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis
and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis. 相似文献
45.
I Urasiński G Uhlenbruck C Dienst 《Folia haematologica (Leipzig, Germany : 1928)》1985,112(3):403-408
The capacity to phagocytosis in monocytic macrophages was investigated in 24 patients with plasmocytoma. The investigation of this capacity was made by using short-term cultures with sheep erythrocytes loaded with antibodies and complement. In comparison to the control group the percentage of phagocyting macrophages was lowered in 16 from 24 patients. This impairment of the function of monocytic macrophages seems to be bound neither to the type of plasmocytoma nor to the stage of disease. Among other things, the nature of cell defect is discussed. The necessity of further investigations is emphasized. 相似文献
46.
M. Cycoń Z. Piotrowska-Seget J. Kozdrój 《World journal of microbiology & biotechnology》2010,26(3):409-418
Changes in microbiological characteristics in response to diazinon, applied at three different dosages of 7, 35 and 700 mg kg?1 soil, were studied in pots filled with sandy soils of different texture. The insecticide dosages corresponded to the maximum predicted environmental concentration (PEC) in field conditions and five or hundred times this rate, respectively. To ascertain these changes, activities of selected soil enzymes, numbers of some microbial populations and bacterial community structure (r/K-strategists) were determined. Acid phosphatase activity and concentrations of ammonium ions either increased or were unaffected by the diazinon dosages. In contrast, nitrate ions, alkaline phosphatase, urease and especially dehydrogenase activities decreased in both soils treated with the higher dosages of the insecticide. The diazinon treatments increased the numbers of culturable bacteria and fungi; however, N-fixing bacteria and nitrifiers (but not denitrifiers) were decreased in both soils. When the high concentration of diazinon (100-times PEC) was added to the loamy sand soil (LS), simulating an undiluted chemical spill, the bacterial community structure shifted towards domination of K-strategists over time. However, r-strategists dominated in the community exposed to the same dosage of the insecticide in the sandy loam soil (SL). Generally, SL soil characteristics were more suitable for microbial activity and growth than those of LS soil were. The results indicate that except a situation of undiluted spill diazinon seems to be a non-hazardous chemical for the culturable soil microorganisms when applied at recommended concentrations. 相似文献
47.
48.
49.
The effect of pteridine derivatives and analogues on the cell outgrowth from the ovarian explants of the waxmoth, Galleria mellonella, was examined in hanging-drop cultures and cytochemical tests were made for succinate and glucose-6-phosphate dehydrogenases. Most of the derivatives and analogues of 2-amino-4-hydroxypteridine injured to a lesser or greater extent insect ovarian tissues in vitro, depending on the drug structure and the concentration applied. Of all the pteridine derivatives and analogues tested only 2-amino-4-mercaptopteridine and its C-6,7-dimethyl derivative (10 μM) promoted cell outgrowth from the explants as did folate. 相似文献
50.