全文获取类型
收费全文 | 2571篇 |
免费 | 283篇 |
国内免费 | 203篇 |
出版年
2024年 | 4篇 |
2023年 | 59篇 |
2022年 | 64篇 |
2021年 | 132篇 |
2020年 | 136篇 |
2019年 | 160篇 |
2018年 | 107篇 |
2017年 | 123篇 |
2016年 | 110篇 |
2015年 | 130篇 |
2014年 | 201篇 |
2013年 | 195篇 |
2012年 | 113篇 |
2011年 | 129篇 |
2010年 | 94篇 |
2009年 | 200篇 |
2008年 | 197篇 |
2007年 | 172篇 |
2006年 | 133篇 |
2005年 | 98篇 |
2004年 | 80篇 |
2003年 | 57篇 |
2002年 | 52篇 |
2001年 | 33篇 |
2000年 | 25篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 34篇 |
1996年 | 14篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有3057条查询结果,搜索用时 206 毫秒
1.
The ECF™ lateral flow assay test is marketed to detect non-pregnancy in mares. The objectives of the present study were to determine the accuracy of the ECF test, the accuracy of the electronic reader accompanying the ECF test, and agreement between two human readers and the electronic reader. Serum samples were collected from anestrus, cycling but not inseminated, and inseminated mares, and were evaluated with the ECF™ test (EDP Biotech Company, Knoxville, TN, USA) at The Ohio State University and at the EDP Biotech Laboratory. Specificity ranged from 0.07 to 0.16, the negative predictive value ranged from 0.15 to 0.33, and accuracy ranged from 0.43 to 0.52. The electronic reader did not add improve the accuracy or predictive values of the test. Based on the electronic reader, 80.0% of the serum samples collected from the anestrus mares were false positives; Readers 1 and 2 had 60.0 and 33.3% false positives, respectively. For samples collected during the estrous cycle, 83.9% were false positives by the electronic reader, whereas Readers 1 and 2 had 43.7 and 26.4% false positives. We concluded that, regardless of whether the test strips were evaluated by a human or electronic reader, this assay was not accurate for determination of the non-pregnant mare. 相似文献
2.
In Central Europe as in most other temperate regions of the world, Buddleja davidii has become a very successful invader. A thorough observation, documentation and analysis of the spread of invasive species is the precondition for the understanding of invasion processes. Therefore, I documented the occurrence of the species along a west–east transect as well as an altitudinal transect, and I tried to reconstruct the spread of the species in the course of the last decades along railroad areas, which have proved to be the most favorized habitats for colonization of Buddleja. Additionally, a literature review is given on its general spread and distribution in Germany. Based on the investigation of 52 stations, the results show that the species, in Germany, has its optimum in the Rhein-Ruhr- and the Rhein-Main-area, that its abundance significantly decreases from west to east and with increasing altitude. A literature review combined with own investigations shows, that it was very successful in Germany on ruins of World War II but decreased and sometimes totally disappeared in cities of East Germany and of the altitudinal higher regions of Germany, i.e. also in many towns of South Germany. In West Germany, the recent spread started about three decades ago and is still in process. As cold winters seem to be the limiting factor for the spread of Buddleja, even an accelerated spread of this species and perhaps a loss of its ruderal character can be expected, considering the progress of climate change. 相似文献
3.
Fourier transform infrared (FTIR) spectroscopic imaging is an emerging microscopy modality for clinical histopathologic diagnoses as well as for biomedical research. Spectral data recorded in this modality are indicative of the underlying, spatially resolved biochemical composition but need computerized algorithms to digitally recognize and transform this information to a diagnostic tool to identify cancer or other physiologic conditions. Statistical pattern recognition forms the backbone of these recognition protocols and can be used for highly accurate results. Aided by biochemical correlations with normal and diseased states and the power of modern computer-aided pattern recognition, this approach is capable of combating many standing questions of traditional histology-based diagnosis models. For example, a simple diagnostic test can be developed to determine cell types in tissue. As a more advanced application, IR spectral data can be integrated with patient information to predict risk of cancer, providing a potential road to precision medicine and personalized care in cancer treatment. The IR imaging approach can be implemented to complement conventional diagnoses, as the samples remain unperturbed and are not destroyed. Despite high potential and utility of this approach, clinical implementation has not yet been achieved due to practical hurdles like speed of data acquisition and lack of optimized computational procedures for extracting clinically actionable information rapidly. The latter problem has been addressed by developing highly efficient ways to process IR imaging data but remains one that has considerable scope for progress. Here, we summarize the major issues and provide practical considerations in implementing a modified Bayesian classification protocol for digital molecular pathology. We hope to familiarize readers with analysis methods in IR imaging data and enable researchers to develop methods that can lead to the use of this promising technique for digital diagnosis of cancer. 相似文献
4.
Xiaoqing Wu Xiaorui Xie Linjuan Su Na Lin Bin Liang Nan Guo Qingquan Chen Liangpu Xu Hailong Huang 《Journal of cellular and molecular medicine》2021,25(18):8929-8935
Pallister-Killian syndrome (PKS) is a rare sporadic genetic disorder usually caused by mosaicism of an extra isochromosome of 12p (i(12p)). This retrospective study analysed the prenatal ultrasound manifestations and molecular and cytogenetic results of five PKS foetuses. Samples of amniotic fluid and/or cord blood, skin biopsy and placenta were collected. Conventional karyotyping and single nucleotide polymorphism array (SNP array) were performed on all the amniotic fluid or cord blood samples. Copy number variants sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were also used for the validation for one foetus. All the five foetuses were from pregnancies with advanced parental age. Two foetuses involved structural abnormalities and one foetus had only soft markers, all of which included increased nuchal translucency. The rest two foetuses had normal ultrasounds in the second trimester, which has rarely been reported before. The karyotype revealed typical i(12p) in four cases and a small supernumerary marker chromosome consisting of 12p and 20p in the remaining one case. The proportion of cells with i(12p) ranged from 0 to 100% in cultural cells, while SNP array results suggested 2−4 copies of 12p. For one foetus, metaphase FISH showed normal results, but the interphase FISH suggested cell lines with two, three and four copies of 12p in the amniotic fluid. Advanced parental age may be an important risk factor for PKS, and there were no typical ultrasound manifestations related to PKS. A combination of karyotype analysis and molecular diagnosis is an effective method for the diagnosis of PKS. 相似文献
5.
6.
《Cell》2022,185(20):3753-3769.e18
7.
H. Schutkowski 《International Journal of Anthropology》1987,2(4):347-352
Facing the requirements of refined paleodemographical analyses, the access to the early ontogenetic sex ratio of skeletal
populations is an important feature. Using raw data provided byFazekas & Kosa (1978) for a sample of known sex, discriminant functions are derived from hip and thigh bone dimensions that allow an almost
unbiased classification of more than 70% of fetal and neonate individuals. 相似文献
8.
Nina Safar-Hermann Mohammed N. Ismail Han Sun Choi Erich Mstl Elmar Bamberg 《Zoo biology》1987,6(2):189-193
Estrogen concentration in feces was investigated in five different herbivorous species of zoo animals. Using a nonspecific estrogen radioimmunoassay, in four species (red buffalo, yak, Grevy's zebra, and Nubian ibex) pregnancy was revealed by measuring estrogen concentration in feces. In hippopotamus, the levels of fecal estrogens were not different between pregnant and nonpregnant animals. 相似文献
9.
Spectrophotometric assay for ornithine decarboxylase 总被引:11,自引:0,他引:11
That T. Ngo Kurt L. Brillhart Rowland H. Davis Raphael C. Wong Jack H. Bovaird Joseph J. Digangi Janet L. Ristow J. Lawrence Marsh Andrew P. H. Phan Howard M. Lenhoff 《Analytical biochemistry》1987,160(2):290-293
A rapid and sensitive spectrophotometric assay for ornithine decarboxylase is described. It is based on the observation that the product of ornithine decarboxylase, putrescine, reacts with 2,4,6-trinitrobenzenesulfonic acid to give a colored product soluble in 1-pentanol whereas ornithine does not. The amount of putrescine produced by the enzyme was determined by measuring the absorbance of the 1-pentanol extract of the reaction mixture at 420 nm, and by comparing the results to those obtained by the trapping of 14CO2 and by HPLC assays. The three assays were found to be equivalent in sensitivity, with the spectrophotometric assay having the advantages of being relatively rapid, requiring only common laboratory equipment, and not requiring the use of radioactive isotopes. 相似文献
10.
A firm, mobile, oblong mass was discovered as an incidental finding in the stomach of a chimpanzee (Pan troglodytes) during routine surgery. It was removed and determined to be a trichobezoar. 相似文献