全文获取类型
收费全文 | 1885篇 |
免费 | 145篇 |
国内免费 | 1篇 |
出版年
2022年 | 8篇 |
2021年 | 24篇 |
2019年 | 21篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 26篇 |
2015年 | 47篇 |
2014年 | 69篇 |
2013年 | 75篇 |
2012年 | 81篇 |
2011年 | 80篇 |
2010年 | 36篇 |
2009年 | 55篇 |
2008年 | 67篇 |
2007年 | 91篇 |
2006年 | 69篇 |
2005年 | 76篇 |
2004年 | 79篇 |
2003年 | 58篇 |
2002年 | 54篇 |
2001年 | 57篇 |
2000年 | 62篇 |
1999年 | 57篇 |
1998年 | 37篇 |
1997年 | 41篇 |
1996年 | 31篇 |
1995年 | 35篇 |
1994年 | 21篇 |
1993年 | 33篇 |
1992年 | 34篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 35篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 47篇 |
1985年 | 32篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 36篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1976年 | 24篇 |
1975年 | 21篇 |
1974年 | 28篇 |
1973年 | 17篇 |
1972年 | 8篇 |
排序方式: 共有2031条查询结果,搜索用时 15 毫秒
81.
Comparative immunocytochemical localization of putative opioid ligands in the central nervous system 总被引:1,自引:0,他引:1
We report a detailed comparative immunocytochemical mapping of enkephalin, CCK and ACTH/beta-endorphin immunoreactive nerves in the central nervous system of rat and guinea pig. Enkephalin immunoreactivity was detected in many groups of nerve cell bodies, fibers and terminals in the limbic system, basal ganglia, hypothalamus, thalamus, brain stem and spinal cord. beta-endorphin and ACTH immunoreactivity was limited to a single group of nerve cell bodies in and around the arcuate nucleus and in fibers and terminals in the midline areas of the hypothalamus, thalamus and mesencephalic periaqueductal gray with lateral extensions to the amygdaloid area. Cholecystokinin immunoreactive nerve fibers and terminals displayed a distribution similar to that of enkephalin in many regions; but striking differences were also found. An immunocytochemical doublestaining technique, which allowed simultaneous detection of two different peptides in the same tissue section, showed that enkephalin-, CCK- and ACTH/beta-endorphin-immunoreactive nerves although closely intermingled in many brain areas, occurred separately. The distributions of nerve terminals containing these neuropeptides showed striking overlaps and also paralleled the distribution of opiate receptors. This may suggest that enkephalin, CCK, ACTH and beta-endorphin may interact with each other and with opiate receptors. 相似文献
82.
83.
The metabolic response to L-lysine of Escherichia coli ATCC 13002, a lysine-histidine double auxotroph, has been examined in a synthetic medium containing sucrose. In shaken cultures largest amounts of extracellular DAP were produced with an initial lysine concentration of 7·5 mg/1 and in static cultures of 2·5 mg/1. Considerably smaller amounts of DAP accumulated under stationary conditions. In cultures shaken for 20 and 43 h there was an overall decrease in the yields of DAP, expressed in terms of cell biomass and of sucrose consumed, as the initial concentration of lysine was increased from 0·75 mg/1 in steps up to 25 mg/1. The regulatory effect of lysine on DAP production was also observed when lysine was supplied to cultures at a constant rate employing diffusion capsules. 相似文献
84.
The aim of the study was to evaluate the importance of mother-concaptus relationships for the elevated embryonic loss in repeat breeder heifers. Embryos were collected by non-surgical technique, classified and transferred surgically or non-surgically to synchronized, inseminated recipients. The embryos were transferred to the uterinehorn contralateral to the corpus luteum. The embryos were transferred from repeat breeder heifers (RBH) to virgin heifers (VH) or from VH to RBH. After slaughter 4 weeks after transfer there was no difference in emhryonic survival between heifer categories following transfer or insemination. In some animals degenerated foetal membranes were found in the nonpregnant horn. The study indicates embryonic morphology rather than the category of donor or recipient as influencing the embryonic survival rate. 相似文献
85.
Rune Bergman Lennart Larsson Göran Odham Gunilla Westerdahl 《Journal of microbiological methods》1983,1(1):19-22
Gas chromatography/mass spectrometry adapted for selected ion monitoring was used to detect C32 mycocerosic acid in short-term incubated cultures of procineand canine strains of mycobacteria. The method can be employed for rapid differentiation of Mycobacterium tuberculosis from M. avium-intracellulare. 相似文献
86.
Cartilage matrix proteins. A basic 36-kDa protein with a restricted distribution to cartilage and bone 总被引:2,自引:0,他引:2
T Larsson Y Sommarin M Paulsson P Antonsson E Hedbom M Wendel D Heineg?rd 《The Journal of biological chemistry》1991,266(30):20428-20433
A non-collagenous quantitatively prominent protein was purified from guanidine hydrochloride extracts of bovine tracheal cartilage. Purification was achieved by cesium chloride density gradient centrifugation and chromatography on DEAE-cellulose at pH 7.0 followed by CM-cellulose at pH 5.0. The protein has a marked tendency to form aggregates in denaturing solutions of high ionic strength, e.g. 6 M guanidine hydrochloride. The purified protein contains a single, Mr 36,000 polypeptide chain, with a particularly high content of leucine. It contains about 1% carbohydrate with a remarkable absence of hexosamines and sialic acid, whereas xylose, galactose, mannose, and fucose were identified in the preparation. The protein was identified in extracts of cartilage and bone and could be shown to be primarily extracellular. Tendon may contain trace amounts of the protein, whereas extracts of several other tissues showed no immunoreactivity in enzyme-linked immunosorbent assay. 相似文献
87.
Phenotypes of cat plasma apolipoprotein A4 (APOA4), antithrombin 3 (AT3), alpha 1B-glycoprotein (A1BG), transferrin (TF), vitamin D-binding protein (GC), and an unidentified pretransferrin (PTF) were determined by using simple methods of horizontal, nondenaturing gel electrophoresis followed by protein staining. The cat proteins were identified by immunoblotting using antisera for human plasma proteins. Three alleles were reported for each of TF and PTF, and two alleles were reported for each of GC, APOA4, AT3, and A1BG. The mongrels and Persians showed a high degree of polymorphism at most of the loci whereas the Birmans exhibited much less variation. Genetic evidence indicating the occurrence of a monomeric and a dimeric form of APOA4 in cat plasma was reported. 相似文献
88.
Petter Larsson 《Hydrobiologia》1991,225(1):281-290
Natural clones and clones from laboratory crossings of Daphnia pulex have been tested in their response to stimuli for male and ephippia formation. The clones are from ponds in Illinois, USA, an area with both obligate and cyclical clones of D. pulex. The progeny from two types of crosses were studied: 1) crosses between an obligate clone producing males and a cyclical clone producing only females, and 2) self-fertilization within a cyclical clone producing both sexes. Both the natural and the artificial clones showed great variation in response to environmental stimuli for males. Ephippia response seems more equal among the clones, but two of the artificial clones could hardly be stimulated to produce ephippia in the induction experiments. In crowded cultures, however, they produced a few. Crossings between cyclicals and obligates yielded mostly cyclical progeny. Progeny from the selfed clone had low survival and fecundity. 相似文献
89.
Secondary alcohols of Mycobacterium xenopi were studied by gas chromatography and gas chromatography-mass spectrometry. Mycobacterial cells were hydrolysed and the liberated alcohols separated by extraction and analysed both underivatized and as trimethylsilyl, methyl ether- and pentafluorobenzoyl derivatives. Seven straight-chain secondary alcohols containing from 18 to 24 carbon atoms and two branched-chain secondary alcohols with 21 and 23 carbon atoms were present in all of the studied strains. 相似文献
90.