全文获取类型
收费全文 | 561611篇 |
免费 | 49549篇 |
国内免费 | 1064篇 |
专业分类
612224篇 |
出版年
2018年 | 15497篇 |
2017年 | 14187篇 |
2016年 | 12704篇 |
2015年 | 7457篇 |
2014年 | 8774篇 |
2013年 | 12549篇 |
2012年 | 17649篇 |
2011年 | 26405篇 |
2010年 | 21032篇 |
2009年 | 16573篇 |
2008年 | 21891篇 |
2007年 | 24023篇 |
2006年 | 12749篇 |
2005年 | 12429篇 |
2004年 | 13061篇 |
2003年 | 12795篇 |
2002年 | 12411篇 |
2001年 | 21325篇 |
2000年 | 21525篇 |
1999年 | 16702篇 |
1998年 | 5704篇 |
1997年 | 5883篇 |
1996年 | 5456篇 |
1995年 | 5238篇 |
1994年 | 5133篇 |
1993年 | 5157篇 |
1992年 | 14200篇 |
1991年 | 13897篇 |
1990年 | 13510篇 |
1989年 | 13195篇 |
1988年 | 12363篇 |
1987年 | 11851篇 |
1986年 | 10688篇 |
1985年 | 10894篇 |
1984年 | 8962篇 |
1983年 | 7833篇 |
1982年 | 5854篇 |
1981年 | 5171篇 |
1980年 | 5002篇 |
1979年 | 8839篇 |
1978年 | 6796篇 |
1977年 | 6248篇 |
1976年 | 5759篇 |
1975年 | 6497篇 |
1974年 | 7186篇 |
1973年 | 7173篇 |
1972年 | 6868篇 |
1971年 | 6412篇 |
1970年 | 5301篇 |
1969年 | 5097篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
We have analyzed dermatoglyphic finger patterns in a Spanish Basque population (841 males and 911 females). Bimanual and sexual comparisons have been carried out by means of contingency analysis. The results in the Basque population are compared with those of other Spanish populations, based on univariate (chi 2 contingency test and Student's t-test) and multivariate (principal components analyses) statistical methods. Bilateral distribution asymmetry and sexual dimorphism were observed in the Basque sample. The results of the chi 2 test for pattern types in males and females show statistically significant differences between the Basques and other Spanish populations, with the exception of the males from El Bierzo. Comparing populations with regard to the Pattern Intensity Index, the differences observed are much lower; therefore, this confirms what other authors have suggested regarding the limited usefulness of indexes in populational comparisons. In the Caucasian variation range of pattern types, Basques are located in the high part with regard to arches, in the low part with regard to whorls and radial loops, and in an intermediate part in relation to ulnar loops and overall pattern intensity. Results of the multivariate comparisons show which populations are more or less distant from the Basque population and which variables are significant in contributing to these population relationships. 相似文献
972.
973.
974.
975.
The receptor for transferrin on murine myeloma cells: one-step purification based on its physiology, and partial amino acid sequence 总被引:3,自引:0,他引:3
I R van Driel P A Stearne B Grego R J Simpson J W Goding 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(6):3220-3224
The receptor for transferrin is one of the major surface proteins of proliferating lymphocytes and other cells. It binds ferrotransferrin from serum and endocytoses it into an acidic nonlysosomal intracellular compartment where iron is released, but in which apotransferrin remains tightly bound to its receptor. Recycling of the apotransferrin-receptor complex to the cell surface is associated with a return to neutral pH and concomitant loss of affinity of apotransferrin for its receptor. Apotransferrin is then free to leave the cell and initiate a new cycle. We have exploited this cycle in a novel method for the purification of the receptor for transferrin. Murine myeloma cells were lysed in nonionic detergent, and the lysate passed over a column of ferrotransferrin-agarose at pH 7.4. After washing with sodium acetate at pH 5.0, iron was removed with sodium citrate pH 5.0 and desferrioxamine. Upon returning the pH to neutrality, the receptor was eluted and found to be homogeneous by SDS-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions. The degree of purification was estimated to be at least 3,000-fold, and the calculated yield was 10 to 20%. The purified receptor was capable of binding to transferrin. The receptor was digested with trypsin, and the resulting peptides were separated by reversed-phase high performance liquid chromatography in NH4HCO3. Selected peptides were rechromatographed in 0.1% trifluoroacetic acid, and their amino acid sequences were determined. 相似文献
976.
Five new species of Passiflora subgenera Plectostemma and Tacsonia from Ecuador are described, viz. P. discophora, P. monadelpha, P. subpurpurea, P. hirtiflora and P. sanctaebarbarae . Section Discophora of subg. Plectostemma is proposed. 相似文献
977.
R D Gavriliaka N A Semina L I Fiks S V Shabalina N V Tsvetkova 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(1):45-48
ELISA is used for detecting the soluble staphylococcal antigen in patients with purulent septic infections. The optimum conditions for the assay have been established: the dose of staphylococcal gamma globulin for plate sensitization should be 5.0-10.0 micrograms/ml, the pH of the buffer solution 9.6-10.0, the time and temperature of incubation 18-20 hours at 4 degrees C or 5 hours at 37 degrees C. The possibility of using plates manufactured in the USSR has been shown. The sensitivity of the above diagnostic test system is 0.005 microgram/ml. 相似文献
978.
979.
980.