全文获取类型
收费全文 | 26512篇 |
免费 | 1921篇 |
国内免费 | 382篇 |
出版年
2023年 | 160篇 |
2022年 | 369篇 |
2021年 | 615篇 |
2020年 | 463篇 |
2019年 | 560篇 |
2018年 | 689篇 |
2017年 | 589篇 |
2016年 | 862篇 |
2015年 | 1317篇 |
2014年 | 1452篇 |
2013年 | 1799篇 |
2012年 | 2083篇 |
2011年 | 1935篇 |
2010年 | 1238篇 |
2009年 | 1066篇 |
2008年 | 1465篇 |
2007年 | 1385篇 |
2006年 | 1356篇 |
2005年 | 1193篇 |
2004年 | 1092篇 |
2003年 | 1092篇 |
2002年 | 964篇 |
2001年 | 424篇 |
2000年 | 404篇 |
1999年 | 382篇 |
1998年 | 243篇 |
1997年 | 210篇 |
1996年 | 191篇 |
1995年 | 155篇 |
1994年 | 179篇 |
1993年 | 151篇 |
1992年 | 227篇 |
1991年 | 208篇 |
1990年 | 184篇 |
1989年 | 203篇 |
1988年 | 161篇 |
1987年 | 140篇 |
1986年 | 140篇 |
1985年 | 144篇 |
1984年 | 106篇 |
1983年 | 113篇 |
1982年 | 91篇 |
1981年 | 87篇 |
1980年 | 70篇 |
1979年 | 85篇 |
1978年 | 61篇 |
1977年 | 96篇 |
1975年 | 69篇 |
1974年 | 76篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
51.
52.
Antonio Grinyo 《Biotechnic & histochemistry》1968,43(1):19-25
Specimens of brain or spinal cord fixed in formalin, Cajal's formol-bromide, or Koenig, Groat and Windle's formalin-acacia can be used to stain oligodendrocytes in frozen, in paraffin, or in celloidin sections. The sections are soaked 3-5 min in 0.02% acetic acid, pH 3.4, then rinsed 2-3 sec in 3% H2O2 and transferred to a silver bath prepared as follows: Mix equal parts of 10% AgNO3 and 10% Na2WO4, and dissolve the precipitate with concentrated NH4OH; avoid an excess of ammonia. Silver at room temperature for 15-20 sec, develop in 1% formalin, dehydrate, and mount. For embedded material, prepare a mixture consisting of 1 part of 10% aqueous Aerosol MA and 4 parts of 10% Aerosol OT in 95% alcohol. Add 5 drops of this mixture to each 50 ml of dilute acetic acid and 3% H2O2; 5 drops to each 20 ml of the silver bath. 相似文献
53.
Initial reaction rates for the hydrolysis of nucleic acids with micrococcal endonuclease (EC 3.1.31.1) insolubilized on Sepharose are strongly influenced by diffusional limitations. Although the absolute values are low, they can be increased substantially by changing particle and pore size of the support, or enzyme concentration in the insoluble derivative. As a result of steric and diffusional limitations, the course of the reaction and selectivity to hydrolysis products for the insoluble derivatives are different to those of the native enzyme; the former produces mainly large and small fragments but few of intermediate size. Because of these differences in course and selectivity of the reaction, diffusional limitations become less important when high initial reaction rates are not required. 相似文献
54.
55.
A retrovirus carrying the polyomavirus middle T gene induces acute thrombocythemic myeloproliferative disease in mice. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A Fusco G Portella M Grieco G Tajana G Di Minno N Polli A Pinto 《Journal of virology》1988,62(1):361-365
Mice inoculated with an artificially constructed retrovirus carrying the middle T gene of polyomavirus develop acute myeloproliferative disease with severe thrombotic and hemorrhagic disorder and impaired platelet function. The megakaryocytic lineage appears to be a target for polyoma-murine leukemia virus infection and middle T gene expression. This newly described disease represents a unique model system for studying disorders of the megakaryocytic lineage. 相似文献
56.
57.
Pedigree analysis is a central component of many current efforts to locate genes that contribute to diseases or to valuable traits. The analysis usually involves solving one of two very computation-intense problems. We analyze the complexity of these two problems. Surprisingly, we show that both problems are NP-hard even for pedigrees that contain no inbreeding loops. 相似文献
58.
Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (Km=2.1 mM) and L-glutamine (Km=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (Km=1 mM) and L-glutamine (Km=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.Abbreviations A
Absorbance
- CCP
p-Trichlorometoxi-carbonylcyanide-phenylhydrazone
- Chl
Chlorophyll
- CMU
3-(p-Chlorophenyl)-1,1-dimethyl urea
- DPIP
2,6-Dichlorophenol-indophenol
- DTE
Dithioerythritol
- MSX
L-Methionine, D-L, sulfoximine
- MV
Methyl viologen 相似文献
59.
Behavioural expression of D-1 receptor supersensitivity depends on previous stimulation of D-2 receptors 总被引:1,自引:0,他引:1
SKF 38393 (2 mg/kg s.c.), a reportedly selective D-1 agonist, failed to induce contralateral turning behaviour in naive rats bearing 12 days old unilateral 6-hydroxydopamine lesions. On the other hand strong contraversive turning in response to SKF 38393 was obtained if rats had been tested 2 or 7 days before with apomorphine (0.1 mg/kg s.c.) or with LY 171555 (0.2 mg/kg s.c.), a selective D-2 receptor agonist. Contraversive turning in response to SKF 38393 was blocked by a low dose (0.05 mg/kg s.c.) of the specific D-1 antagonist SCH 23390. The results indicate that the behavioural expression of D-1 receptor supersensitivity following lesion of dopaminergic neurons depends on previous exposure to a stimulation of D-2 receptors. 相似文献
60.