全文获取类型
收费全文 | 3407篇 |
免费 | 276篇 |
国内免费 | 4篇 |
出版年
2021年 | 42篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 23篇 |
2017年 | 39篇 |
2016年 | 60篇 |
2015年 | 93篇 |
2014年 | 105篇 |
2013年 | 154篇 |
2012年 | 187篇 |
2011年 | 177篇 |
2010年 | 127篇 |
2009年 | 95篇 |
2008年 | 137篇 |
2007年 | 147篇 |
2006年 | 131篇 |
2005年 | 130篇 |
2004年 | 146篇 |
2003年 | 124篇 |
2002年 | 130篇 |
2001年 | 62篇 |
2000年 | 66篇 |
1999年 | 70篇 |
1998年 | 55篇 |
1997年 | 42篇 |
1996年 | 36篇 |
1995年 | 28篇 |
1994年 | 37篇 |
1993年 | 40篇 |
1992年 | 53篇 |
1991年 | 45篇 |
1990年 | 38篇 |
1989年 | 45篇 |
1988年 | 44篇 |
1987年 | 33篇 |
1986年 | 30篇 |
1985年 | 37篇 |
1984年 | 45篇 |
1983年 | 24篇 |
1982年 | 50篇 |
1981年 | 38篇 |
1980年 | 42篇 |
1979年 | 36篇 |
1978年 | 43篇 |
1977年 | 27篇 |
1976年 | 37篇 |
1975年 | 25篇 |
1974年 | 33篇 |
1973年 | 29篇 |
1972年 | 25篇 |
排序方式: 共有3687条查询结果,搜索用时 15 毫秒
41.
Idiopathic pulmonary hemosiderosis is a rare condition manifested by recurrent pulmonary hemorrhage of unknown cause, diffuse radiologic abnormalities, cough, hemoptysis and moderate to severe hypochromic anemia. Diagnosis can be confirmed by iron stains of the sputum or lung aspiration or by biopsy. Prolonged spontaneous remission may occur without the use of corticosteroid therapy. Studies here reported indicated that the anemia is hypochromic and microcytic anemia of blood loss and iron deficiency, in spite of the presence of large amounts of iron in the pulmonary tissue. Correction of the anemia by intensive iron therapy and transfusion is considered an important part of therapy. 相似文献
42.
43.
44.
45.
46.
Maurice Partridge 《BMJ (Clinical research ed.)》1959,1(5126):915-916,917
47.
Maurice Campbell 《BMJ (Clinical research ed.)》1959,1(5133):1341-1342
48.
Paraspinibarbus, a new and monotypic genus, is erected forSpinibarbus macracanthus Pellegrin et Chevey, 1936, a cyprinid from the Red River basin. It is characterized by a procumbent predorsal spine and a
very thick lower lip with a continuous postlabial groove.Balantiocheilus hekouensis Wu, 1977 is a junior subjective synonym ofParaspinibarbus macracanthus. A lectotype is designated forS. macracanthus. 相似文献
49.
ß-Glucuronidase (GUS) and chloramphenicol acetyl transferase (CAT) were used as reporter proteins in protoplasts from embryogenic suspension cultures of Picea glauca (Moench) Voss (white spruce). Plasmid DNA enclosing chimeric GUS and CAT constructs, using the cauliflower mosaic virus 35S promoter, was introduced into Picea glauca protoplasts using polyethylene glycol (PEG). Transient expression was detected 12 to 40 h after PEG-mediated DNA delivery. Dose-response curves using covalently closed circular plasmid DNA, in the absence of carrier DNA, have been obtained for each of these reporter genes. Linearized plasmid DNA gave lower levels of expression than covalently closed circular plasmid DNA when assayed 40 h after PEG-mediated DNA transfer. The use of carrier DNA (herring sperm DNA), in combination with covalently closed circular plasmid DNA, increased the level of expression of GUS by about 50%. CAT expression was enhanced if PEG-mediated delivery was performed on ice rather than at room temperature. The highest level of expression for CAT, and the lowest signal-to-noise ratio, was found 24 h after PEG-mediated DNA transfer. Both GUS and CAT provided results that were quantifiable and can therefore be used as reporter genes in Picea glauca.Abbreviations CAT
chloramphenicol acetyl transferase
- GUS
ß-glucuronidase
- CaMV
cauliflower mosaic virus
- NOS
nopaline synthase
- CCC
covalently closed circular DNA
- L
linear DNA
- PEG
polyethylene glycol
- HS
herring sperm DNA
- P
protoplasts
- PCM
protoplast culture medium
- MES
morpholinoethane-sulfonic acid
- Cm
chloramphenicol
- Ac
acetylated
- MUG
4-methyl umbelliferyl ß-D-glucuronide
- TLC
thin layer chromatography 相似文献
50.
D Bauchart D Durand P M Laplaud P Forgez S Goulinet M J Chapman 《Journal of lipid research》1989,30(10):1499-1514
The in vivo role of the liver in lipoprotein homeostasis in the preruminant calf, a functional monogastric, has been evaluated. To this end, the hydrodynamic and physicochemical properties, density distribution, apolipoprotein content, and flow rates of the various lipoprotein particle species were determined in the hepatic afferent (portal vein and hepatic artery) and efferent (hepatic vein) vessels in fasting, 3-week-old male preruminant calves. Plasma lipoprotein profiles were established by physicochemical analyses of a series of subfractions isolated by isopycnic density gradient ultracentrifugation. Triglyceride-rich very low density lipoproteins (VLDL) (d less than 1.018 g/ml) were minor plasma constituents (approximately 1% or less of total d less than 1.180 g/ml lipoproteins). The major apolipoproteins of VLDL were apoB-like species, while the complement of minor components included bovine apoA-I and apoC-like peptides. Particles with diameters (193-207 A) typical of low density lipoproteins (LDL) were present over the density interval 1.026-1.076 g/ml; however, only LDL of d 1.026-1.046 g/ml were present as a unique and homogeneous size subspecies, containing the two apoB-like species as major protein components in addition to elevated cholesteryl ester contents. LDL represented approximately 10% of total d less than 1.180 g/ml lipoproteins in fasting plasma from all three hepatic vessels. Overlap in the density distribution of particles with the diameters of LDL and of high density lipoproteins (HDL) occurred in the density range from 1.046 to 1.076 g/ml; these HDL particles were 130-150 A in diameter. HDL were the major plasma particles (approximately 90% of total d less than 1.180 g/ml substances) and presented as two distinct populations which we have termed light (HDLL) and heavy (HDLH) HDL. Light HDL (d 1.060-1.091 g/ml) ranged in size from 120 to 140 A, and were distinguished by their high cholesteryl ester (29-33%) and low triglyceride (1-3%) contents; apoA-I was the principal apolipoprotein. Small amounts of apolipoproteins with Mr less than 60,000, including apoC-like peptides, were also present. Heavy HDL (d 1.091-1.180 g/ml) accounted for almost half (47%) of total calf HDL, and like HDLL, were also enriched in cholesteryl ester and apoA-I; they ranged in size from 93 to 120 A. The protein moiety of HDLH was distinct in its possession of an apoA-IV-like protein (Mr 42,000). Blood flow rates were determined by electromagnetic flowmetry, thereby permitting determination of net lipoprotein balance across the liver. VLDL were efficiently removed during passage through the liver (net uptake 1.06 mg/min per kg body weight).(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献