全文获取类型
收费全文 | 569篇 |
免费 | 12篇 |
国内免费 | 43篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 15篇 |
2009年 | 18篇 |
2008年 | 10篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 23篇 |
1983年 | 38篇 |
1982年 | 45篇 |
1981年 | 31篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 24篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1974年 | 16篇 |
1973年 | 7篇 |
1972年 | 3篇 |
排序方式: 共有624条查询结果,搜索用时 992 毫秒
11.
纵坑切梢小蠹蛀梢期空间分布 总被引:10,自引:1,他引:9
在昆明地区,纵坑切梢小蠹(Tomicus piniperda)成虫蛀梢多集中在蛀干木附近。 种群密度以蛀干木为中心向周围呈指数递减,散布半径约30m。在蛀梢过程中,该种群逐渐向新区扩张。在树冠内,纵坑切梢小蠹主要分布在4-10轮枝上。第7轮枝虫口百分率最高。6-7轮枝受害率最大。 树冠上层受害较其下层严重。从树冠水平层次考察,树冠外层虫量相对集中,约为树冠中、内层虫量之和。 树冠内层虫量最少。纵坑切梢小蠹在树冠内的种群分布系由梢径、种群密度、蛀梢行为、降落方式、光照等因素综合影响的结果。 相似文献
12.
Hélène Déméné Nathalie Jullian Nelly Morellet Hugues de Rocquigny Fabrice Cornille Bernard Maigret Bernard P. Roques 《Journal of biomolecular NMR》1994,4(2):153-170
Summary The nucleocapsid protein of Moloney murine leukemia virus (NCp10) is a 56-amino acid protein which contains one zinc finger of the CysX2CysX4HisX4Cys form, a highly conserved motif present in most retroviruses and retroelements. At pH5, NCp10 binds one zinc atom and the complexation induces a folding of the CysX2CysX4HisX4Cys box, similar to that observed for the zinc-binding domains of HIV-1 NC protein. The three-dimensional structure of NCp10 has been determined in aqueous solution by 600 MHz 1H NMR spectroscopy. The proton resonances could be almost completely assigned by means of phase-sensitive double-quantum-filtered COSY, TOCSY and NOESY techniques. NOESY spectra yielded 597 relevant structural constraints, which were used as input for distance geometry calculations with DIANA. Further refinement was performed by minimization with the program AMBER, which was modified by introducing a zinc force field. The solution structure is characterized by a well-defined central zinc finger (rmsd of 0.747±0.209 Å for backbone atoms and 1.709±0.187 Å when all atoms are considered), surrounded by flexible N- and C-terminal domains. The Tyr28, Trp35, Lys37, Lys41 and Lys42 residues, which are essential for activity, lie on the same face of the zinc finger, forming a bulge structure probably involved in viral RNA binding. The significance of these structural characteristics for the various biological functions of the protein is discussed, taking into account the results obtained with various mutants. 相似文献
13.
本研究在改进后短程序基础上,对氨基酸分离柱进行了改进。改进后的分离柱长为10cm。比原来20cm长柱分离3—MH的时间缩短了近1/2。实验所得的(回收率为97.59%,分离度0.89±0.02。变异系数1.17)这些指标较国外用其它方法所得的结果有良好的相关性。多次测定结果说明长柱与短柱比较无明显差异。证明了短柱对3—MH含量无影响。这一改进所建立的方法大大地缩短了样品的分析时间,节约了大量进口试剂,开展这方面的工作将有利益提高严重烧伤、创伤后蛋白质代谢和营养学等方面的研究水平。 相似文献
14.
One hundred and fifty four (86 male and 68 female) Punjabi infants residing in Chandigarh (India) were longitudinally measured
for head circumference at monthly age intervals during first year of life. The general pattern of growth of head circumference
was characterised by initial sharp rise followed by slow gain during second half of infancy. Beyond birth male infants, possessed
higher and statistically significant mean values than their female counterparts. The pattern-wise similarity between growth
curves plotted for Punjabi and Western infants, may be attributed to protective effects of breast feeding. Head circumference
velocity showed rapid deceleration immediately after birth up to about 4 months, thereafter, it declined slowly. Sex differences
in monthly growth rates were found to be statistically significant (p<0.05) at a few of the age intervals during first year
of life. 相似文献
15.
Gaetano Barbato Daniel O. Cicero Elisabetta Bianchi Antonello Pessi Renzo Bazzo 《Journal of biomolecular NMR》1996,8(1):36-48
Summary We describe the high-resolution structure by NMR of two peptides that belong to a combinatorial library based on the zinc-finger motif. The library represents, to the best of our knowledge, the first example of a conformationally homogeneous peptide library and was obtained by introducing random residues in five positions of the -helical portion of a 26-residue consensus peptide (CP1) belonging to the Cys2-Hys2 zinc-finger family. The result was shown to be a highly homogeneous -helical library (Bianchi et al., 1995). The structures of the parent compound (CP1) and of a representative member (CP1m) that was selected by screening the library with a monoclonal antibody are compared in detail as an example of the very high stability of the zinc-finger scaffold upon sequence variability. The two peptides exhibit an extremely high degree of structural similarity. The use of this type of conformationally constrained combinatorial library might represent a step forward in the design of peptidomimetics, as it considerably accelerates the process of the identification of the spatial relationship among the pharmacophoric groups.Abbreviations
t-Bu
tert-butyloxycarbonyl
- Fmoc
9-fluorenylmethoxycarbonyl 相似文献
16.
Souichi Morikawa Kazuhiro Ogata Ai Sekikawa Akinori Sarai Shunsuke Ishii Yoshifumi Nishimura Haruki Nakamura 《Journal of biomolecular NMR》1995,6(3):294-305
Summary The solution structure of a specific DNA complex of the minimum DNA-binding domain of the mouse c-Myb protein was determined by distance geometry calculations using a set of 1732 nuclear Overhauser enhancement (NOE) distance restraints. In order to determine the complex structure independent of the initial guess, we have developed two different procedures for the docking calculation using simulated annealing in four-dimensional space (4D-SA). One is a multiple-step procedure, where the protein and the DNA were first constructed independently by 4D-SA using only the individual intramolecular NOE distance restraints. Here, the initial structure of the protein was a random coil and that of the DNA was a typical B-form duplex. Then, as the starting structure for the next docking procedure, the converged protein and DNA structures were placed in random molecular orientations, separated by 50 Å. The two molecules were docked by 4D-SA utilizing all the restraints, including the additional 66 intermolecular distance restraints. The second procedure comprised a single step, in which a random-coil protein and a typical B-form DNA duplex were first placed 70 Å from each other. Then, using all the intramolecular and intermolecular NOE distance restraints, the complex structure was constructed by 4D-SA. Both procedures yielded the converged complex structures with similar quality and structural divergence, but the multiple-step procedure has much better convergence power than the single-step procedure. A model study of the two procedures was performed to confirm the structural quality, depending upon the number of intermolecular distance restraints, using the X-ray structure of the engrailed homeodomain-DNA complex.Abbreviations rmsd
root-mean-square deviation
- NOE
nuclear Overhauser enhancement
- 4D-SA
simulated annealing in four-dimensional space
- Myb-R2R3
repeats 2 and 3 of the DNA-binding domain of the c-Myb protein
- DNA 16
Myb-specific binding DNA duplex with 16 base pairs
- IHDD-C
residues 3 to 59 of the C-chain of the engrailed homeodomain-DNA complex
- DNA11
DNA duplex with base pairs 9 to 19 of the engrailed homeodomain-DNA complex 相似文献
17.
Monoclonal antibodies (QB01 and 1200) prepared against human proclatin (hPRL) have helped define a variant form of the hormone. This variant is of apparently higher molecular mass (26kDa) than the predominant form of the hormone (24kDa) and its presence does not appear to be species-restricted. The demonstration of the 26 kDa form of the hPRL in fresh pituitary tissue and amniotic fluid suggests it may retain some specific function. 相似文献
18.
19.
Isoelectric focusing following by electrophoresis of proteins for visualizing their titration curves by zymogram and immunofixation 总被引:1,自引:0,他引:1
After isoelectric focusing followed by electrophoresis at right angles in the same gel slab, it is possible to visualize the titration curve of proteins by zymograms or immunofixation even of an unpurified sample. This information can be very useful for the selection of the proper purification strategy by charge-dependent methods, e.g. ion-exchange chromatography, zone and disc electrophoresis and isotachophoresis. The titration curve also gives information on the stability of the protein as a function of the prevailing pH of the medium, in the pH 3-10 range. A region of instability is found for most proteins in acidic conditions, below pH 4.5, while most proteins are stable in the alkaline pH region, at least up to pH 10. The best method for developing zymograms and immunoprints appears to pH 10. The best method for developing zymograms and immunoprints appears to be the 'sandwich technique', by which a thin agarose slab, cast on an hydrophilic polyester sheet, and impregnated with appropriate reagents, is left in contact with a polyacrylamide gel thin layer used to generate the titration curves. 相似文献
20.
Maternal and neonatal disposition of pethidine in childbirth--a study using quantitative gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
J Caldwell L A Wakile L J Notarianni R L Smith G J Correy B A Lieberman R W Beard M D Finnie W Snedden 《Life sciences》1978,22(7):589-596
An assay for pethidine using gas chromatography-mass spectrometry with single ion monitoring has been developed for its analysis in the blood of neonates whose mothers received pethidine during childbirth. Concentrations were determined from the height of the peak at m/e 218 derived from pethidine compared with that at m/e 234 derived from the internal standard lignocaine. Results from 10 mothers and their babies show the time-related passage of pethidine across the placenta. The elimination half-life of the drug from neonatal blood was 22.7h compared with 3h in the adult. 相似文献