全文获取类型
收费全文 | 11094篇 |
免费 | 1002篇 |
国内免费 | 1篇 |
出版年
2022年 | 101篇 |
2021年 | 197篇 |
2020年 | 113篇 |
2019年 | 150篇 |
2018年 | 195篇 |
2017年 | 155篇 |
2016年 | 270篇 |
2015年 | 498篇 |
2014年 | 539篇 |
2013年 | 613篇 |
2012年 | 840篇 |
2011年 | 764篇 |
2010年 | 511篇 |
2009年 | 465篇 |
2008年 | 698篇 |
2007年 | 650篇 |
2006年 | 597篇 |
2005年 | 605篇 |
2004年 | 589篇 |
2003年 | 572篇 |
2002年 | 506篇 |
2001年 | 112篇 |
2000年 | 91篇 |
1999年 | 102篇 |
1998年 | 170篇 |
1997年 | 121篇 |
1996年 | 120篇 |
1995年 | 111篇 |
1994年 | 94篇 |
1993年 | 71篇 |
1992年 | 86篇 |
1991年 | 69篇 |
1990年 | 79篇 |
1989年 | 61篇 |
1988年 | 76篇 |
1987年 | 57篇 |
1986年 | 65篇 |
1985年 | 70篇 |
1984年 | 81篇 |
1983年 | 59篇 |
1982年 | 61篇 |
1981年 | 72篇 |
1980年 | 56篇 |
1979年 | 56篇 |
1978年 | 53篇 |
1977年 | 47篇 |
1976年 | 38篇 |
1974年 | 40篇 |
1973年 | 42篇 |
1970年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 687 毫秒
261.
Mouse testis cells have been separated by equilibrium density centrifugation in gradients of Renografin. Intact testis cells were not damaged by the separation procedure provided that, following separation, the osmolarity was reduced gradually. The various cell types were identified microscopically and by 3H-thymidine labelling with similar results. The present technique has demonstrated that significant variations in cell density occur during spermatogenesis. Approximately ten-fold enrichments of nearly all testis cell types were achieved by equilibrium density separation of testis cell suspensions. More homogeneous cell populations were prepared by density gradient centrifugation of cell fractions obtained from velocity sedimentation separations. Overall enrichments of spermatogonia, by 29-fold; pachytene spermatocytes, 45-fold; dividing meiotic cells, 170-fold; round spermatids, 30-fold; step 11–13 elongating spermatids, 12-fold; Leydig cells, 70-fold; and cytoplasmic fragments, 55-fold, were obtained. In this study, a method for preparation of cell suspensions was also developed to produce higher yields of spermatogonia and young primary spermatocytes; however, the density distribution of these cells was altered. 相似文献
262.
The nudibranch Coryphella rufibranchialis (JOHNSTON) feeds on a variety of hydroids, including Tubularia larynx Ellis & Solander. Experiments in which density of prey and predators were altered showed that more prey were eaten as prey density increased. However, more prey were consumed at low predator densities, presumably because of mutual interference among nudibranchs at the higher predator densities. The number of prey consumed per nudibranch was maximal with low predator densities and a ratio of 25–50 polyps per predator. Coryphella seems to show an opportunistic feeding strategy involving solitary predators rapidly depleting hydroid colonies and moving on to new colonies. 相似文献
263.
Najma Zaheer Baquer John S. Hothersall A.L. Greenbaum Patricia McLean 《Biochemical and biophysical research communications》1975,62(3):634-641
The effect of Mn2+ on the pattern of emergence of enzymes in rat liver and adipose tissue was studied in weaned rats given a milk diet (high fat) or sucrose-casein diet (high carbohydrate) for three weeks. Addition of Mn2+ to the high fat diet was associated with induction of key glycolytic, lipogenic and pentose pathway enzymes in both liver and adipose tissue; parallel increases were found in the incorporation of [1-14C] glucose into lipid and CO2. Mn2+ induced a change in the profile of enzyme activity similar in pattern to that found in rats given a high sucrose diet or that produced by insulin treatment. Mn2+ appears partially to overcome the regulatory feed-back mechanisms of the high fat diet and to provide a signal for the coordinated increase of glucose catabolic and lipogenic processes. 相似文献
264.
Leon Salganicoff Patricia A. Hebda John Yandrasitz Miriam H. Fukami 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,385(2):394-411
Subcellular components were obtained from pig platelets, disrupted by means of a French press and separated into 4 primary fractions. The granule fraction (10 000 g) was subjected to a sucrose gradient fractionation. Primary fractions and the granule subfractions were studied electron microscopically and biochemically by following the distribution of markers of membranes, lysosomes of α-granules, mitochondria and dense granules. With this technique of platelet homogenization, 80% of the serotonin and 93% of the β-N-acetylglucosaminidase were found to be particulate. In the gradient, mitochondria were sharply banded in a fraction (density 1.16–1.17) having a specific activity 10–100 times higher than the other fractions of the gradient. Serotonin-containing granules were found in a pellet of density greater than 1.27 and contained 60% of the serotonin and adenine nucleotides of the granule fraction. The lysosome markers that were monitored, acid phosphatase and β-N-acetylglucosaminidase, exhibited different distribution patterns. Acid phosphatase showed the highest specific activity in the microsomal fraction with only 2.8% in the granule fraction, and this latter amount also appeared to be associated with membranes upon further fractionation. β-N-Acetylglucosaminidase was present in both the granule fraction and in the microsomal fraction with nearly the same specific activity. However, that present in the granule fraction was clearly associated with granules that distributed over a wide range of densities on a sucrose gradient. The calcium distribution was followed to attempt to determine its subcellular location; 19% was found in the same subfraction as the serotonin-containing granules, but at least 50% of the particulate calcium was associated with granules distinctly separate from the storage granules. 相似文献
265.
266.
Rachid Zerrouki Traki Benhassine Mustapha Bensaada Patricia Lauzon Anissa Trabzi 《Genetics and molecular biology》2016,39(1):7-13
Many subtypes of acute lymphoblastic leukemia (ALL) are associated with specific chromosomal rearrangements. The complex translocation t(9;14;14), a variant of the translocation (14;14)(q11;q32), is a rare but recurrent chromosomal abnormality involving the immunoglobulin heavy-chain (IGH) and CCAAT enhancer-binding protein (CEBPE) genes in B-lineage ALL (B-ALL) and may represent a new B-ALL subgroup. We report here the case of a 5-year-old girl with B-ALL, positive for CD19, CD38 and HLA-DR. A direct technique and G-banding were used for chromosomal analysis and fluorescentin situ hybridization (FISH) with BAC probes was used to investigate a possible rearrangement of the IGH andCEBPE genes. The karyotype exhibit the chromosomal aberration 46,XX,del(9)(p21),t(14;14)(q11;q32). FISH with dual-color break-apartIGH-specific and CEPBE-specific bacterial artificial chromosome (BAC) probes showed a complex t(9;14;14) associated with a deletion of cyclin-dependent kinase inhibitor 2A (CDKN2A) and paired box gene 5 (PAX5) at 9p21-13 and duplication of the fusion gene IGH-CEBPE. 相似文献
267.
Luiz Henrique Soares de Andrade Wilson Max Almeida Monteiro de Moraes Eduardo Hiroshi Matsuo Junior Elizabeth de Orleans Carvalho de Moura Hanna Karen Moreira Antunes Jairo Montemor Ednei Luiz Antonio Danilo Sales Bocalini Andrey Jorge Serra Paulo José Ferreira Tucci Patricia Chakur Brum Alessandra Medeiros 《Molecular and cellular biochemistry》2015,402(1-2):193-202
268.
269.
Patricia Easterbrook Roberts 《Arts Education Policy Review》2013,114(4):153-172
270.