全文获取类型
收费全文 | 2971篇 |
免费 | 291篇 |
国内免费 | 9篇 |
专业分类
3271篇 |
出版年
2022年 | 32篇 |
2021年 | 49篇 |
2020年 | 32篇 |
2019年 | 57篇 |
2018年 | 49篇 |
2017年 | 61篇 |
2016年 | 81篇 |
2015年 | 128篇 |
2014年 | 133篇 |
2013年 | 171篇 |
2012年 | 189篇 |
2011年 | 219篇 |
2010年 | 130篇 |
2009年 | 114篇 |
2008年 | 129篇 |
2007年 | 145篇 |
2006年 | 150篇 |
2005年 | 139篇 |
2004年 | 110篇 |
2003年 | 97篇 |
2002年 | 101篇 |
2001年 | 82篇 |
2000年 | 86篇 |
1999年 | 70篇 |
1998年 | 27篇 |
1997年 | 26篇 |
1996年 | 22篇 |
1995年 | 29篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 60篇 |
1991年 | 47篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 30篇 |
1986年 | 22篇 |
1985年 | 33篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1975年 | 13篇 |
1974年 | 16篇 |
1973年 | 20篇 |
1972年 | 14篇 |
1968年 | 9篇 |
排序方式: 共有3271条查询结果,搜索用时 8 毫秒
101.
102.
103.
104.
H G van der Poel M E Boon L P Kok E A van der Meulen R D van Caubergh W C de Bruijn F M Debruyne 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》1991,13(5):307-315
An image analysis method of grading histologic sections of bladder carcinoma was tested. The method was new in four respects. First, for fixation of the biopsies a coagulant fixative was used. Second, 2-microns plastic sections were used to ensure the reproducibility of nuclear imaging. Third, a new stereologic approach was used for calculation of the nuclear volume and DNA content. Fourth, for the classification rule the morphometric, densitometric and texture features were used in concert. The IBAS 2000 instrument was used for the measurements. Texture analysis of the chromatin patterns was performed using Markovian texture features. Using discriminant analysis, of 22 parameters, 2 morphometric, 2 densitometric and 3 texture features were selected for the classification rule. With them, 89% of the bladder carcinomas were correctly classified into the three grades. All grade III tumors were classified correctly. Among the features tested, the densitometry of the DNA had the highest F values. All of the grade III tumors and 45% of the grade II tumor group had DNA histograms indicating aneuploidy. This study showed that plastic-embedded material is well suited to morphometry and densitometry and can be used for quantitative grading of bladder carcinoma. 相似文献
105.
W. Frommer L. Archer B. Boon G. Brunius C. H. Collins P. Crooy R. Donikian I. Economidis C. Frontali T. Gaal S. Hamp H. Haymerle P. Krämer H. Lagast H. M. L. Lelieveld M. Th. Logtenberg S. Lund J. L. Mahler F. Normand-Plessier F. Rudan R. Simon G. Tuijnenberg Muijs R. G. Werner 《Applied microbiology and biotechnology》1992,38(2):139-140
The Working Party on Safety in Biotechnology of the European Federation of Biotechnology has proposed a classification of microorganisms that cause diseases in plants. In this paper appropriate safety levels are proposed for these classes of microorganisms in order to ensure that research, development and industrial fermentation work with plant pathogens will limit the risk of outbreaks of diseases in crops that could result from work with such microorganisms when they are cultivated in laboratories, glasshouses and biotechnology installations.Co-opted: J. Dähne, J. Drozd, M. Lemattre, I. M. Smith , E. M. A. WaterschootA Report prepared by the Working Party on Safety in Biotechnology of the European Federation of Biotechnology (EFB)
相似文献
相似文献
106.
M A Handel J Papaconstantinou D P Allison E M Julku E T Chin 《Developmental biology》1973,35(2):240-249
During the mid to late 4th instar period of larval development, the mitochondria of Rhynchosciara spermatocytes undergo highly characteristic morphological changes. In late meiosis the enlarged mitochondria fuse to form a single mitochondrial element which will ultimately extend the length of the spermatid tail. Our studies have shown that synthesis of a circular DNA occurs during this period of mitochondrial “differentiation.” This DNA has a density of 1.681 g/cm3; and its synthesis cannot be detected in somatic tissues such as salivary gland, fat body, or gastric cecum. From analysis of DNA extracted from mitochondrial pellets, we have shown that the circular DNA is associated with the mitochondria. The contour length of the mitochondrial DNA is 9 μm, equivalent to a molecular weight of 18 × 106. Although most metazoan mitochondrial DNAs exhibit contour lengths of approximately 5 μm (10 × 105 daltons), there is no extractable 5 μm circular DNA in these spermatocytes. Therefore, we conclude that either Rhynchosciara spermatocytes possess a distinct 9 μm mitochondrial DNA or that the spermatocyte mitochondrial DNA represents dimers of 5 μm monomers. 相似文献
107.
108.
Hung-Yen Ke Li-Han Chin Chien-Sung Tsai Feng-Zhi Lin Yen-Hui Chen Yung-Lung Chang Shih-Ming Huang Yao-Chang Chen Chih-Yuan Lin 《Journal of cellular and molecular medicine》2020,24(6):3669-3677
Cardiovascular complications are leading causes of morbidity and mortality in patients with chronic kidney disease (CKD). CKD significantly affects cardiac calcium (Ca2+) regulation, but the underlying mechanisms are not clear. The present study investigated the modulation of Ca2+ homeostasis in CKD mice. Echocardiography revealed impaired fractional shortening (FS) and stroke volume (SV) in CKD mice. Electrocardiography showed that CKD mice exhibited longer QT interval, corrected QT (QTc) prolongation, faster spontaneous activities, shorter action potential duration (APD) and increased ventricle arrhythmogenesis, and ranolazine (10 µmol/L) blocked these effects. Conventional microelectrodes and the Fluo-3 fluorometric ratio techniques indicated that CKD ventricular cardiomyocytes exhibited higher Ca2+ decay time, Ca2+ sparks, and Ca2+ leakage but lower [Ca2+]i transients and sarcoplasmic reticulum Ca2+ contents. The CaMKII inhibitor KN93 and ranolazine (RAN; late sodium current inhibitor) reversed the deterioration in Ca2+ handling. Western blots revealed that CKD ventricles exhibited higher phosphorylated RyR2 and CaMKII and reduced phosphorylated SERCA2 and SERCA2 and the ratio of PLB-Thr17 to PLB. In conclusions, the modulation of CaMKII, PLB and late Na+ current in CKD significantly altered cardiac Ca2+ regulation and electrophysiological characteristics. These findings may apply on future clinical therapies. 相似文献
109.
S.A. Mir M.W. Siddiqui B.N. Dar M.A. Shah M.H. Wani S. Roohinejad G.A. Annor K. Mallikarjunan C.F. Chin A. Ali 《Journal of applied microbiology》2020,129(3):474-485
Consumers’ demand is increasing for safe foods without impairing the phytochemical and sensory quality. In turn, it has increased research interest in the exploration of innovative food processing technologies. Cold plasma technology is getting popularity now days owing to its high efficacy in decontamination of microbes in fruit and fruit-based products. As a on-thermal approach, plasma processing maintains the quality of fruits and minimizes the thermal effects on nutritional properties. Cold plasma is also exploited for inactivating enzymes and degrading pesticides as both are directly related with quality loss and presently are most important concerns in fresh produce industry. The present review covers the influence of cold plasma technology on reducing microbial risks and enhancing the quality attributes in fruits. 相似文献
110.