全文获取类型
收费全文 | 202522篇 |
免费 | 7225篇 |
国内免费 | 826篇 |
专业分类
210573篇 |
出版年
2023年 | 706篇 |
2022年 | 607篇 |
2021年 | 1389篇 |
2020年 | 1309篇 |
2019年 | 1251篇 |
2018年 | 14146篇 |
2017年 | 12711篇 |
2016年 | 10823篇 |
2015年 | 5684篇 |
2014年 | 5481篇 |
2013年 | 7262篇 |
2012年 | 12041篇 |
2011年 | 19183篇 |
2010年 | 15837篇 |
2009年 | 11113篇 |
2008年 | 14943篇 |
2007年 | 16196篇 |
2006年 | 5566篇 |
2005年 | 5024篇 |
2004年 | 5449篇 |
2003年 | 5064篇 |
2002年 | 4466篇 |
2001年 | 3114篇 |
2000年 | 2920篇 |
1999年 | 2142篇 |
1998年 | 909篇 |
1997年 | 675篇 |
1996年 | 705篇 |
1995年 | 629篇 |
1992年 | 1222篇 |
1991年 | 1122篇 |
1990年 | 1045篇 |
1989年 | 1127篇 |
1988年 | 968篇 |
1987年 | 947篇 |
1986年 | 881篇 |
1985年 | 923篇 |
1984年 | 817篇 |
1983年 | 689篇 |
1982年 | 567篇 |
1979年 | 767篇 |
1978年 | 591篇 |
1975年 | 679篇 |
1974年 | 735篇 |
1973年 | 719篇 |
1972年 | 893篇 |
1971年 | 847篇 |
1970年 | 628篇 |
1969年 | 678篇 |
1968年 | 647篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Effect of precursors on biosynthesis of monensins A and B 总被引:1,自引:0,他引:1
Precursors of monensins (acetate, propionate, butyrate, isobutyrate) affect the total production and the relative proportion of monensins A and B. Addition of propionate into the fermentation medium causes a prevalence of monensin B whereas butyrate and isobutyrate stimulate the production of monensin A and suppress the production of monensin B. 相似文献
102.
M Lebl E E Sugg G van Binst P Vander Elst D Tourwé J Slaninová V J Hruby 《International journal of peptide and protein research》1987,30(3):318-322
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities. 相似文献
103.
Background
Radial chromosome positioning in interphase nuclei is nonrandom and can alter according to developmental, differentiation, proliferation, or disease status. However, it is not yet clear when and how chromosome repositioning is elicited. 相似文献104.
Background
In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy involving classical biparental inheritance in plants and in animals. 相似文献105.
H. Štorchová 《Biologia Plantarum》1994,36(3):358-358
106.
TNF inhibitors are currently considered both effective and cost-effective in patients with active rheumatoid arthritis (RA),
particularly in patients who have not responded fully to methotrexate. There is substantial doubt about the cost-effectiveness
of TNF inhibitors as initial treatment for active RA. New data from the National Data Bank for Rheumatic Diseases now question
the current consensus in methotrexate failures. The data suggest that in routine clinical practice TNF inhibitors provide
only modest incremental benefits over best conventional therapy. If confirmed, these observational studies suggest that the
economic argument underpinning the widespread use of TNF inhibitors in established RA is unsustainable. 相似文献
107.
Background
DNA Microarrays have become the standard method for large scale analyses of gene expression and epigenomics. The increasing complexity and inherent noisiness of the generated data makes visual data exploration ever more important. Fast deployment of new methods as well as a combination of predefined, easy to apply methods with programmer's access to the data are important requirements for any analysis framework. Mayday is an open source platform with emphasis on visual data exploration and analysis. Many built-in methods for clustering, machine learning and classification are provided for dissecting complex datasets. Plugins can easily be written to extend Mayday's functionality in a large number of ways. As Java program, Mayday is platform-independent and can be used as Java WebStart application without any installation. Mayday can import data from several file formats, database connectivity is included for efficient data organization. Numerous interactive visualization tools, including box plots, profile plots, principal component plots and a heatmap are available, can be enhanced with metadata and exported as publication quality vector files. 相似文献108.
109.
110.
Effect of pharmacological agents on the activity of the circular and longitudinal smooth muscle layers of human fallopian tube ampullar segments 总被引:1,自引:0,他引:1
The in vitro determination of the effects of some pharmacological agents on the outer diameter and axial tension of human Fallopian tube ampullar segments showed that some drugs may act on the circular and longitudinal smooth muscle layers relatively separately. PGF2 alpha elicited an excitatory response in both muscle layers while norepinephrine and isoproterenol decreased the activity. Oxytocin and indomethacin had relatively limited effects on the spontaneous motility of the ampullar segments. The calcium antagonist verapamil inhibited the spontaneous periodic activity. 相似文献