全文获取类型
收费全文 | 3035篇 |
免费 | 289篇 |
国内免费 | 1篇 |
专业分类
3325篇 |
出版年
2023年 | 19篇 |
2022年 | 27篇 |
2021年 | 61篇 |
2020年 | 49篇 |
2019年 | 74篇 |
2018年 | 83篇 |
2017年 | 76篇 |
2016年 | 114篇 |
2015年 | 141篇 |
2014年 | 170篇 |
2013年 | 215篇 |
2012年 | 189篇 |
2011年 | 195篇 |
2010年 | 140篇 |
2009年 | 135篇 |
2008年 | 158篇 |
2007年 | 131篇 |
2006年 | 112篇 |
2005年 | 103篇 |
2004年 | 108篇 |
2003年 | 114篇 |
2002年 | 98篇 |
2001年 | 72篇 |
2000年 | 78篇 |
1999年 | 59篇 |
1998年 | 41篇 |
1997年 | 26篇 |
1996年 | 27篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 38篇 |
1987年 | 19篇 |
1986年 | 32篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1974年 | 17篇 |
1973年 | 12篇 |
1969年 | 7篇 |
排序方式: 共有3325条查询结果,搜索用时 15 毫秒
51.
J. del Mazo J. A. Abrisqueta Amalia Pérez-Castillo V. Aller M. Angeles Martín Lucas M. Luisa de Torres M. José Martín 《Human genetics》1978,44(1):105-108
Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports. 相似文献
52.
Two more "private" polymorphisms of Amerindian tribes: LDHb GUA-1 and ACP1 B GUA-1 in the Guaymi in Panama. 下载免费PDF全文
A survey of Guaymi Indians of Panama for the occurrence of genetic variants of 25 proteins of the erythrocytes and sera have revealed, in addition to seven well-known genetic polymorphisms, four rare variants and two "private polymorphisms," the latter involving erythrocyte acid phosphatase and lactate dehydrogenase. The significance of such private polymorphisms in tribal populations to the interpretation of rare variants in civilized populations is emphasized. 相似文献
53.
Two strains ofAspergillus flavus Linkex Fr. and two strains ofA. parasiticus Speare were cultured on crushed moist wheat (Triticum durum var. Pané no. 247) for aflatoxin production studies in correlation with morphological changes. The toxicogenic strains were adapted to the substratum by means of successive transfers at regular intervals (72 h.)The amount aflatoxins synthesized by the toxicogenic strains decreased gradually after succesive subculturing. The decrease was accompanied by marked morphological changes. One of the strains studied,A. flavus NRRL 3251, lost completly the capacity of aflatoxin synthesis after several subcultures, presenting at the same time strong morphological variations.A. flavus CBS 120.62 also lost its toxicogenicity after six subcultures. 相似文献
54.
Dr. Joseph Torres Jr. 《Cell and tissue research》1980,208(1):29-33
Summary A polytrophic ovariole of the queen honeybee, Apis mellifera, is composed of a linear series of increasingly mature egg chambers, each consisting of an oocyte, an interconnected cluster of nurse cells, and a covering layer of follicle cells. This study describes changes in the volume of each of these components, as a function of the position of the egg chamber in the ovariole. An oocyte increases in volume from approximately 8.9 × 103 m3 to approximately 9.6 × 106 m3 over an average series of 20 egg chambers. 相似文献
55.
56.
A birefringence technique is used to determine the average magnetic moments <μ> of magnetotactic bacteria in culture. Differences in <μ> are noted between live and dead bacteria, as well as between normal density and high density samples of live bacteria. 相似文献
57.
Characterization of immune type interferon (IFN gamma)-induced cytoplasmic protein kinase activity in mouse L cells 总被引:1,自引:0,他引:1
K Ohtsuki B A Torres H M Johnson 《Biochemical and biophysical research communications》1982,104(2):422-429
Mouse immune interferon (IFNγ) induced double-stranded RNA-independent protein kinase activity in the cytoplasmic fraction of mouse L cells as measured against a histone substrate. Chromatographic purification separated the activity into three distinct kinases of molecular weights of approximately 100K (kinase I), 70K (kinase II), and 70K (kinase III). Partially purified IFNγ was as effective as crude in inducing protein kinase activity. Induction was blocked by treatment of IFNγ with specific anti-IFNγ antibody or by treatment of the L cells with actinomycin D. Kinase II activity was different from that of kinases I and III in that it showed Ca-dependence in the absence of Mg2+, was inhibited in activity by the SH binding agent N-ethylmaleimide, and could use the cellular enzymes RNase A and hexokinase as substrates. The described protein kinases could play an important role in mediation of IFNγ effects, particularly where phosphorylated enzyme substrates were shown to have altered activity. 相似文献
58.
59.
Detection of salmonellas by DNA hybridization with a fluorescent alkaline phosphatase substrate. 总被引:2,自引:0,他引:2
R J Cano M J Torres R E Klem J C Palomares J Casadesus 《The Journal of applied bacteriology》1992,72(5):393-399
This study evaluates a DNA hybridization assay for salmonella with AttoPhos (JBL Scientific, San Luis Obispo, CA), a fluorescent substrate for alkaline phosphatase. The probe used (50 ng/ml) was a biotinylated 600 bp fragment consisting of a tandem repeat of an insertion sequence (IS200) found in most Salmonella spp. evaluated. The hybridization was carried out at 65 degrees C for 2 h without prior prehybridization and hybrids were detected by the addition of a streptavidin-alkaline phosphatase conjugate. Circles (5 mm) were cut from the membrane and placed in a cuvette containing 1 ml of 1 mmol/l AttoPhos. The reaction was evaluated after 30 min at 37 degrees C with a fluorometer with an excitation wavelength of 440 nm and an emission wavelength of 550 nm. The sensitivity of the probe was estimated to be 10,000 copies of target DNA or 5 x 10(-20) mol of DNA. All 74 salmonella strains tested reacted with the probe but none of the 98 heterologous species tested gave positive results. The results of this study indicate that our assay method, which employs a biotinylated tandem repeat of IS200 and AttoPhos, is a specific and highly sensitive quantitative method for the detection of salmonellas. 相似文献
60.
Calvet S Clapés P Vigo JP Xaus N Jorba X Mas RM Torres JL Valencia G Serralheiro ML Cabral JM Empis JM 《Biotechnology and bioengineering》1992,39(5):539-549
The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the alpha-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH(2) was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-alpha protection choice. Boc and Z were the most reactive N-alpha groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement. 相似文献