全文获取类型
收费全文 | 11386篇 |
免费 | 1561篇 |
国内免费 | 13篇 |
出版年
2021年 | 115篇 |
2018年 | 141篇 |
2017年 | 121篇 |
2016年 | 204篇 |
2015年 | 343篇 |
2014年 | 339篇 |
2013年 | 432篇 |
2012年 | 500篇 |
2011年 | 483篇 |
2010年 | 300篇 |
2009年 | 313篇 |
2008年 | 412篇 |
2007年 | 478篇 |
2006年 | 422篇 |
2005年 | 406篇 |
2004年 | 377篇 |
2003年 | 355篇 |
2002年 | 320篇 |
2001年 | 299篇 |
2000年 | 313篇 |
1999年 | 321篇 |
1998年 | 150篇 |
1997年 | 118篇 |
1996年 | 131篇 |
1995年 | 128篇 |
1994年 | 136篇 |
1993年 | 143篇 |
1992年 | 247篇 |
1991年 | 235篇 |
1990年 | 216篇 |
1989年 | 214篇 |
1988年 | 224篇 |
1987年 | 212篇 |
1986年 | 206篇 |
1985年 | 226篇 |
1984年 | 202篇 |
1983年 | 153篇 |
1982年 | 143篇 |
1981年 | 120篇 |
1980年 | 116篇 |
1979年 | 187篇 |
1978年 | 152篇 |
1977年 | 126篇 |
1976年 | 152篇 |
1975年 | 146篇 |
1974年 | 120篇 |
1973年 | 151篇 |
1972年 | 143篇 |
1971年 | 120篇 |
1970年 | 136篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Daren Lee Seth Ruffins Queenie Ng Nikhil Sane Steve Anderson Arthur Toga 《BMC bioinformatics》2010,11(1):608
Background
Digital atlases provide a common semantic and spatial coordinate system that can be leveraged to compare, contrast, and correlate data from disparate sources. As the quality and amount of biological data continues to advance and grow, searching, referencing, and comparing this data with a researcher's own data is essential. However, the integration process is cumbersome and time-consuming due to misaligned data, implicitly defined associations, and incompatible data sources. This work addressing these challenges by providing a unified and adaptable environment to accelerate the workflow to gather, align, and analyze the data. 相似文献52.
Purification and characterization of purple acid phosphatase from developing rat bone 总被引:1,自引:0,他引:1
Tartrate-resistant acid phosphatase active on nucleoside di- and triphosphate substrates was isolated from developing rat bone and purified 2500-fold. The enzyme concentration had a purple coloration and activity that was sensitive to reducing agents. Mild reducing agents such as ferrous ion and ascorbic acid caused loss of purple color and increased activity toward substrates severalfold; however, a strong reductant such as dithionite caused loss of both color and activity which were partially restored by addition of ferrous ion and ascorbic acid. Enzyme activity was homogeneous with protein during the final gel permeation steps of chromatography and gave an apparent molecular size of about 40,000 Da. Determination of iron in the most pure preparation revealed the presence of 1.3 atoms of iron per molecule of the tartrate-resistant enzyme E2. Other properties of the purified enzyme include a pI of approximately 9.5 and sensitivity to inhibition by ions of copper, zinc, fluoride, and molybdate. Antibody prepared to the pre-concanavalin A (Con A)-Sepharose purified enzyme reacted with all protein from the Con A step, but it did not react with tartrate-sensitive acid phosphatase from rat bone or with potato acid phosphatase. Purple acid phosphatase from rat bone has many properties that parallel the iron-containing purple acid phosphatases from rat spleen, bovine spleen, and pig uterine secretions. 相似文献
53.
54.
Transposable elements derived from the 7SL RNA gene, such as Alu elements in primates, have had remarkable success in several mammalian lineages. The results presented here show a broad spectrum of functions for genomic segments that display sequence composition similarities with the 7SL RNA gene. Using thoroughly documented loci, we report that DNaseI-hypersensitive sites can be singled out in large genomic sequences by an assessment of sequence composition similarities with the 7SL RNA gene. We apply a root word frequency approach to illustrate a distinctive relationship between the sequence of the 7SL RNA gene and several classes of functional genomic features that are not presumed to be of transposable origin. Transposable elements that show noticeable similarities with the 7SL sequence include Alu sequences, as expected, but also long terminal repeats and the 5′-untranslated regions of long interspersed repetitive elements. In sequences masked for repeated elements, we find, when using the 7SL RNA gene as query sequence, distinctive similarities with promoters, exons and distal gene regulatory regions. The latter being the most notoriously difficult to detect, this approach may be useful for finding genomic segments that have regulatory functions and that may have escaped detection by existing methods. 相似文献
55.
56.
57.
58.
J E Pugh M R Horwitz D J Anderson E F Singleton 《American journal of physical anthropology》1973,38(2):351-356
A new technique for the continuous recording of peripheral bioelectrical activity in the auditory system of primates is described. Because of basic differences in the anatomy of the temporal bone, the approach to the round window of the cochlea is more difficult in most primates than in lower animals. A relatively simple surgical approach, which made possible the placement of an electrode into the perilymph of the inner ear via the well-demarcated horizontal semicircular canal was therefore developed and is described in detail. The bared tip of a Teflon-coated wire was cemented into the canal opening with carboxylate cement, and the wire attached to a permanent electrical connector on the skull. Cochlear microphonic and action potentials of 50 to 100 μV amplitude were thus recorded on a continuing basis at the same time that behavioral studies of primate auditory acuity were conducted. 相似文献
59.
Multigene DNA Priming-Boosting Vaccines Protect Macaques from Acute CD4+-T-Cell Depletion after Simian-Human Immunodeficiency Virus SHIV89.6P Mucosal Challenge 下载免费PDF全文
60.
The ultrastructure of sporulation of a new parasite, Marteilioides branchialis (Paramyxea), in the Sydney Rock oyster, Saccostrea commercialis, is described. The development is typical of other Paramyxea whereby a stem cell internally cleaves a secondary cell contained within a vacuole. It differs from other species in the phylum in that each secondary cell produces a single spore composed of two concentric cells, one within a vacuole of the other. This type of sporulation represents the simplest of all known Paramyxea. Infection results in focal gill lesions and was observed concurrently with an epizootic of another paramyxean, Marteilia sydneyi. 相似文献