全文获取类型
收费全文 | 705030篇 |
免费 | 80807篇 |
国内免费 | 859篇 |
专业分类
786696篇 |
出版年
2018年 | 6408篇 |
2016年 | 8694篇 |
2015年 | 12341篇 |
2014年 | 14414篇 |
2013年 | 20047篇 |
2012年 | 23041篇 |
2011年 | 23660篇 |
2010年 | 15864篇 |
2009年 | 14322篇 |
2008年 | 20685篇 |
2007年 | 21543篇 |
2006年 | 20164篇 |
2005年 | 19384篇 |
2004年 | 19494篇 |
2003年 | 18550篇 |
2002年 | 18068篇 |
2001年 | 29624篇 |
2000年 | 29620篇 |
1999年 | 23741篇 |
1998年 | 8860篇 |
1997年 | 8931篇 |
1996年 | 8511篇 |
1995年 | 8192篇 |
1994年 | 7911篇 |
1993年 | 7845篇 |
1992年 | 20121篇 |
1991年 | 19667篇 |
1990年 | 19347篇 |
1989年 | 18780篇 |
1988年 | 17440篇 |
1987年 | 16610篇 |
1986年 | 15530篇 |
1985年 | 15417篇 |
1984年 | 12789篇 |
1983年 | 11225篇 |
1982年 | 8612篇 |
1981年 | 7756篇 |
1980年 | 7266篇 |
1979年 | 12401篇 |
1978年 | 9748篇 |
1977年 | 8897篇 |
1976年 | 8322篇 |
1975年 | 9364篇 |
1974年 | 10225篇 |
1973年 | 10095篇 |
1972年 | 9117篇 |
1971年 | 8535篇 |
1970年 | 7241篇 |
1969年 | 7060篇 |
1968年 | 6387篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
A method for separation and visualization of the different apolipoprotein B species using 0.2% sodium dodecyl sulfate-1.5% agarose gel electrophoresis and immunoblotting is described. The method is capable of demonstrating the different forms of apolipoprotein B (apo B) in plasma volumes of 10-50 microliters without prior ultracentrifugation. After ultracentrifugation of samples, estimation of the ratio between apo B 48 and apo B 100 is possible by scanning of Coomassie-stained gels or immunoblots. 相似文献
892.
E Gomard Y Hénin G Sterkers M Masset R Fauchet J P Lévy 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(11):3961-3967
The clone TA10 is a T3+ T4+ T8- proliferative and cytolytic human T cell clone. This clone has been shown to be specific for the hemagglutinin of influenza A Texas virus and restricted by an HLA class II molecule associated with the DRw8-Dw8.1 phenotype. Here we show that TA10 and all of its subclones can also react with eight HLA-DRw8 negative, Epstein-Barr virus (EBV)-transformed cell lines or phytohemagglutinin blasts in the absence of influenza antigens. All of these cell lines are HLA-DR2/DR4 with a classic DR2 long haplotype. The only nonreactive HLA-DR2/DR4 cell line observed bears a DR2 short haplotype. Only heterozygous HLA-DR2/DR4 but not parental DR2 or DR4 EBV-transformed cell lines can be recognized by TA10, indicating that the cross-reacting determinant is a transcomplementation product between HLA-DR2 and HLA-DR4 haplotypes. DR-specific, but not DQ- or DP-specific monoclonal antibodies, inhibit in the proliferation assay and in the chromium release test both the DRw8-Dw8.1-restricted and the anti-DR2/DR4 reactions. These results show that HLA-DR-restricted, anti-viral human T cell clone can evidence cross-reactivity for allospecific class II molecules of the major histocompatibility complex, and human CTL can recognize transcomplementation products of class II HLA genes. In addition, the results suggest that a beta-chain coded for by an HLA-DR gene and associated with an alpha-chain coded for by a still unidentified but possibly HLA-DQ gene constitute this functional transcomplementation product. 相似文献
893.
Ye. P. Dulepova V. A. Nadtochii L. L. Budnikova 《Russian Journal of Marine Biology》2008,34(7):472-481
The trophic structure of benthic communities in the Sea of Okhotsk and Bering Sea was analyzed based on the results of macrobenthic
survey catches conducted in the Far Eastern seas in the 2000s. The production of trophic levels and entire communities was
determined. It was shown that production of benthic communities is still at a high level and has almost not changed since
the 1980s. The arrangement of the communities of some shelf areas by productivity characteristics was made. 相似文献
894.
895.
896.
Seven barley(Hordeum vulgäre L.) cultivars tested varied greatly in their responses to root medium salinity (electrical conductivity of 3, 5, 10, 15 and 20 dS nr-1)-lant growth was relatively more adversely affected than seed germination. Dry/fresh mass ratio increased at higher salinity levels in all barley cultivars indicating reduced water uptake. Higher K/Na ratio in plant shoots compared to that in the root medium solution indicated selective uptake of K that seems to be among processes involved in tolerance of cultivars to salinity stress. 相似文献
897.
898.
The variability of the cardiac rhythm was studied in males with different initial respiratory rates. At rest and during voluntarily controlled breathing, subjects with medium respiratory rates were found to have a less variable heart rate than their counterparts with low or high respiratory rates. 相似文献
899.
900.
We carried out a laboratory investigation of temperature effect on survival as well as reproductive and trophic activities of mesostigmatid mites. Representatives of gamasid (three species) and uropodid (two species) mites abundant in storm detritus were used as model species. The upper reproduction limit and the upper survival limit were determined for the mites and their preys in the thermal range from 29 to 47°C. Most of studied species managed to survive and propagate in a wide thermal range corresponding to the thermal gradient in the peripheral zones of algal belts. The role of temperature as a factor of ecological niche separation in saprophytic Mesostigmata and formation of polydominant mite communities in the algal belts were demonstrated. 相似文献