全文获取类型
收费全文 | 179863篇 |
免费 | 8393篇 |
国内免费 | 923篇 |
专业分类
189179篇 |
出版年
2023年 | 300篇 |
2022年 | 729篇 |
2021年 | 1608篇 |
2020年 | 914篇 |
2019年 | 1146篇 |
2018年 | 13016篇 |
2017年 | 11699篇 |
2016年 | 9445篇 |
2015年 | 4307篇 |
2014年 | 4438篇 |
2013年 | 5244篇 |
2012年 | 10841篇 |
2011年 | 19096篇 |
2010年 | 15898篇 |
2009年 | 11888篇 |
2008年 | 14990篇 |
2007年 | 16529篇 |
2006年 | 5599篇 |
2005年 | 5650篇 |
2004年 | 5936篇 |
2003年 | 5774篇 |
2002年 | 5256篇 |
2001年 | 1193篇 |
2000年 | 878篇 |
1999年 | 1075篇 |
1998年 | 1294篇 |
1997年 | 879篇 |
1996年 | 786篇 |
1995年 | 695篇 |
1994年 | 665篇 |
1993年 | 721篇 |
1992年 | 636篇 |
1991年 | 616篇 |
1990年 | 534篇 |
1989年 | 463篇 |
1988年 | 516篇 |
1987年 | 432篇 |
1986年 | 370篇 |
1985年 | 464篇 |
1984年 | 578篇 |
1983年 | 475篇 |
1982年 | 536篇 |
1981年 | 520篇 |
1980年 | 452篇 |
1979年 | 352篇 |
1978年 | 376篇 |
1977年 | 328篇 |
1976年 | 313篇 |
1972年 | 403篇 |
1971年 | 423篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
—A resolution of the enhancement of protein synthesis in the visual cortex of rats during first exposure to light (Richardson and Rose , 1972) was achieved by polyacrylamide gel electrophoresis using a double-labelling technique. Differential incorporation of lysine was established between exposed and control animals in two fractions of the soluble proteins and seven fractions of the insoluble proteins. This suggests that exposure to a new experience of this type involves a specific effect on protein synthesis, rather than a general stimulation across all fractions. 相似文献
13.
14.
15.
16.
The ultrastructure of the calcareous skeleton is described in twenty–one species of recent tubuliporine cyclostome bryozoans, using field emission SEM. The succession of skeletal fabrics in interior walls may be classified into four different fabric suites. The first–formed part of the calcitic skeleton in all species for which it has been observed is a precursory fabric of tiny, wedge–shaped crystallites. This is succeeded in about half of the species studied by a fabric of transverse fibres, followed by foliated fabric and often semi–nacre (fabric suite 1). Most of the remaining species lack transverse fibres and have interior walls largely comprising semi–nacre (fabric suite 2). A few species have skeletons consisting of predominantly distally–oriented, irregularly or regularly foliated fabric (fabric suite 3). A single species has a skeleton of proximally–oriented foliated fabric (fabric suite 4). Basal exterior walls in all species have a precursory fabric of tiny wedge–shaped crystallites without a strong preferred orientation, deposited directly upon the organic cuticle, followed by a layer of planar spherulitic structure, which in turn is succeeded by a similar fabric to that developed in the interior wall of the species concerned. Outermost layers of frontal exterior walls exhibit one of the following combinations of three fabrics: an outer layer of (1) finely granular or wedge–shaped crystallites; a thin dense granular layer followed by (2) distally accreting planar spherulitic fabric., or (3) obliquely accreting planar spherulitic fabric growing partly towards the midline of the frontal wall. Terminal diaphragms usually have outer layers dominated by planar spherulitic ultrastructure with centripetal growth directions. The fabric suites present in tubuliporines encompass most known fabrics found in the other cyclostome suborders and support the notion that this species–rich suborder occupies a central position in cyclostome evolution. 相似文献
17.
Local administration of phencyclidine (PCP) by pressure ejection elicited a dose-dependent slowing of the spontaneous discharge of cerebellar Purkinje neurons. Ketamine also depressed firing and was much less potent than PCP. Effects of both PCP and ketamine were antagonized by local or parenteral administration of antipsychotic drugs. The similarities between the electrophysiological and behavioral actions of phencyclidine suggest that alterations in neuronal discharge may underlie its psychotomimetic properties. 相似文献
18.
IN addition to its well known antiviral activity, interferon has recently been shown to inhibit the multiplication of tumour and mammalian cells in cell culture1–6. We report here the inhibition by interferon of DNA synthesis induced in mouse spleen lymphocytes by the non-viral stimuli phytohaemagglutinin (PHA) and allogeneic lymphocytes. These findings are in accord with our contention that interferon affects cell function and, furthermore, they suggest that by acting on lymphocytes, interferon plays a role in the immunological response of the host. 相似文献
19.
Bharat Lagu John M. Wetzel Carlos Forray Michael A. Patane Mark G. Bock 《Bioorganic & medicinal chemistry letters》2000,10(24)
The binding affinities and selectivities of antagonists Figure 1 and Scheme 2 for the α1A-adrenoceptor are dependent on the stereochemical orientation of the groups at the C-4 and C-5 positions of the oxazolidinone ring. The unambiguous assignment of the relative and absolute configurations of the diastereomers of SNAP 7915 (Figure 1 and Scheme 2) is reported. 相似文献
20.