全文获取类型
收费全文 | 604683篇 |
免费 | 68343篇 |
国内免费 | 297篇 |
出版年
2018年 | 5213篇 |
2016年 | 7018篇 |
2015年 | 9726篇 |
2014年 | 11380篇 |
2013年 | 16285篇 |
2012年 | 18213篇 |
2011年 | 18355篇 |
2010年 | 12508篇 |
2009年 | 11248篇 |
2008年 | 16288篇 |
2007年 | 16988篇 |
2006年 | 15794篇 |
2005年 | 15320篇 |
2004年 | 15149篇 |
2003年 | 14625篇 |
2002年 | 14556篇 |
2001年 | 29262篇 |
2000年 | 29645篇 |
1999年 | 23185篇 |
1998年 | 7438篇 |
1997年 | 7719篇 |
1996年 | 7319篇 |
1995年 | 7164篇 |
1994年 | 7159篇 |
1993年 | 6887篇 |
1992年 | 19581篇 |
1991年 | 18830篇 |
1990年 | 18250篇 |
1989年 | 17669篇 |
1988年 | 16502篇 |
1987年 | 15522篇 |
1986年 | 14183篇 |
1985年 | 14226篇 |
1984年 | 11608篇 |
1983年 | 10150篇 |
1982年 | 7779篇 |
1981年 | 6860篇 |
1980年 | 6453篇 |
1979年 | 11396篇 |
1978年 | 8561篇 |
1977年 | 7901篇 |
1976年 | 7261篇 |
1975年 | 8108篇 |
1974年 | 8618篇 |
1973年 | 8602篇 |
1972年 | 7967篇 |
1971年 | 7165篇 |
1970年 | 6246篇 |
1969年 | 5991篇 |
1968年 | 5379篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
K Bell 《Animal genetics》1994,25(Z1):109-113
Transferrin, albumin, 6-phosphogluconate dehydrogenase and vitamin D-binding protein polymorphisms were detected in 242 feral and domesticated Australian donkeys by polyacrylamide gel electrophoresis, starch gel electrophoresis, autoradiography, immunoblotting with specific antisera and activity staining. All four TF and two ALB variants were donkey specific while only one of the PGD variants was donkey specific. The two GC variants were electrophoretically identical to the Equus caballus F and S proteins. Available evidence suggested that the TF, ALB, PGD and GC systems are controlled by co-dominant alleles with frequencies of the most common alleles of each system being 0·831, 0·946, 0·957 and 0·861 respectively. Glucose phosphate isomerase and plasminogen were monomorphic in the Australian population of donkeys. 相似文献
102.
K. Düring 《Journal of Phytopathology》1994,141(2):159-164
A comparison of the enzymatic activities of endogenous potato bacteriolytic enzymes with bacteriophage T4 and hen egg white lysozyme has been performed. Using Erwinia carotovora atroseptica and Pseudomonas solanacearum as substrates in, comparison to Micrococcus lysodeikticus a differential pattern of bacteriolytic activities could be detected. The expression pattern of endogenous potato lysozymes suggests that their functional activity against phytopathogenic bacteria in planta is unlikely. Antibacterial activities in transformed, T4 lysozyme expressing and non–transformed potato plants are evaluated. 相似文献
103.
104.
105.
In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators. 相似文献
106.
Response to treatment in hereditary metabolic disease: 1993 survey and 10-year comparison. 总被引:1,自引:1,他引:0
Knowledge about cause, pathogenesis, and manifestations of hereditary metabolic diseases puts them among the best known of all human diseases. On the other hand, outcomes of treatment are cause for uncertainty and concern. In 1985, Hayes et al. analyzed efficacy of treatment up to 1983 in 65 of these diseases selected randomly from the McKusick catalogs. Disease scores were calculated for seven parameters: longevity; reproductive capability; somatic and cognitive development; and handicaps affecting schooling, work, and cosmetic appearance. Scores of the untreated and treated phenotypes were then compared. We have now measured progress over the past decade by calculating scores on the same 65 diseases from data in several hundred new reports published since 1983. All seven parameters in the 1993 survey reflect improved efficacy of treatment in the 10-year interval. However, the percent of diseases for which all manifestations of the disease were removed by treatment has not changed (12% in 1983; 12% in 1993). The group in which manifestations were untouched by treatment has become smaller (48% in 1983; 31% in 1993), and the group partially ameliorated by treatment had increased reciprocally (40% in 1983; 57% in 1993). Progress in the treatment of hereditary metabolic disease is thus better than it was, but it is still only a partial success. The advances are attributable to greater success with organ and tissue transplantation, better pharmacotherapy, and better support systems. Restoration of normal homeostasis, the key to successful treatment, remains an elusive challenge and is a logical, major focus for research in human genetics. 相似文献
107.
malvolio, the Drosophila homologue of mouse NRAMP-1 (Bcg), is expressed in macrophages and in the nervous system and is required for normal taste behaviour. 总被引:4,自引:0,他引:4 下载免费PDF全文
We report the sequence, expression pattern and mutant phenotype of malvolio (mvl), the Drosophila homologue of mammalian natural resistance-associated macrophage proteins (NRAMPs). In the mouse, this novel transporter is encoded by Bcg, a dominant gene that confers natural resistance to intracellular parasites. mvl was identified in a screen for mutants that affect taste behaviour. We show that loss-of-function as well as insertional mutants in mvl display defects in taste behaviour with no alterations in the physiology of the sensory neurons. Activity of the reporter enzyme beta-galactosidase, that reflects the expression pattern of mvl, is seen in mature sensory neurons and in macrophages. The conceptual translation of the mvl cDNA shows a striking similarity (65% identity) with human NRAMP with almost complete identity in a conserved consensus motif found in a number of ATP-coupled transporters. Based on its phenotype and expression pattern as well as its structural similarities to NRAMPs and a nitrate transporter in Aspergillus nidulans, we discuss a possible role for MVL in nitrite/nitrate transport and its implications. 相似文献
108.
109.
110.