全文获取类型
收费全文 | 12190篇 |
免费 | 914篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 116篇 |
儿科学 | 288篇 |
妇产科学 | 294篇 |
基础医学 | 1921篇 |
口腔科学 | 198篇 |
临床医学 | 1205篇 |
内科学 | 2284篇 |
皮肤病学 | 198篇 |
神经病学 | 1323篇 |
特种医学 | 364篇 |
外科学 | 1762篇 |
综合类 | 171篇 |
一般理论 | 8篇 |
预防医学 | 873篇 |
眼科学 | 362篇 |
药学 | 938篇 |
中国医学 | 14篇 |
肿瘤学 | 820篇 |
出版年
2021年 | 125篇 |
2020年 | 64篇 |
2019年 | 113篇 |
2018年 | 160篇 |
2017年 | 132篇 |
2016年 | 138篇 |
2015年 | 207篇 |
2014年 | 285篇 |
2013年 | 501篇 |
2012年 | 581篇 |
2011年 | 653篇 |
2010年 | 356篇 |
2009年 | 346篇 |
2008年 | 613篇 |
2007年 | 634篇 |
2006年 | 617篇 |
2005年 | 669篇 |
2004年 | 644篇 |
2003年 | 585篇 |
2002年 | 592篇 |
2001年 | 178篇 |
2000年 | 150篇 |
1999年 | 160篇 |
1998年 | 148篇 |
1997年 | 141篇 |
1996年 | 108篇 |
1995年 | 107篇 |
1994年 | 102篇 |
1993年 | 90篇 |
1992年 | 130篇 |
1991年 | 130篇 |
1990年 | 98篇 |
1989年 | 83篇 |
1988年 | 106篇 |
1987年 | 90篇 |
1986年 | 105篇 |
1985年 | 118篇 |
1984年 | 144篇 |
1983年 | 110篇 |
1982年 | 129篇 |
1981年 | 153篇 |
1980年 | 153篇 |
1979年 | 119篇 |
1978年 | 99篇 |
1977年 | 100篇 |
1976年 | 93篇 |
1975年 | 113篇 |
1974年 | 104篇 |
1973年 | 99篇 |
1972年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Herbert J. Weingartner Robert Rawlings David T. George Michael Eckardt 《Psychopharmacology》1998,138(3-4):311-317
This study was designed to examine and contrast cognitive effects (explicit memory and access to semantic knowledge) of the
benzodiazepine Halcion (triazolam) in ten normal volunteers and ten cognitively unimpaired detoxified alcoholics. The two
groups were indistinguishable from one another under placebo conditions on all measures of cognitive functioning. Under Halcion
test conditions (0.375 mg PO), both groups were about equally impaired in their recall of to-be-remembered information. However,
alcoholics, were more likely to recall information that they were not asked to remember (intrusion errors) on all measures
of explicit remembering. Alcoholics also generated relatively uncommon (low frequency) responses from semantic memory, rather
than common, categorically related associations in response to stimuli such as types of vegetables, flowers, and fruit following
the administration of Halcion, but were not different from normal volunteers in the types of responses generated under placebo
conditions. These findings suggest that a drug challenge that simulates many of the effects of acute alcohol administration
induces alcoholics to think and remember differently (qualitatively) from normal volunteers.
Received: 7 July 1997 / Final version: 22 September 1997 相似文献
63.
Petit mal-grand mal (PM-GM) electroconvulsive therapy (ECT) is a technique developed by Impastato to elicit unconsciousness with a subconvulsive electrical stimulus, rather than with barbiturate anesthesia. Muscle relaxation is produced with succinylcholine chloride before stimulus is applied. The cases reported here illustrate applications of the technique to depressed patients with severe cardiac and pulmonary disease, and the use of PM-GM ECT in a patient in whom seizures could not be elicited by the usual ECT technique is described. 相似文献
64.
Jorge C. Nadal Cees J. van Groeningen Herbert M. Pinedo Godefridus J. Peters 《Investigational new drugs》1989,7(2-3):163-172
Summary The effect of leucovorin (LV) given in various doses and schedules on the in vivo antitumor activity and toxicity of 5-fluorouracil (5FU) was studied in two murine colon cancer lines, i.e., Colon 26 (relatively resistant to 5FU) and Colon 38 (5FU sensitive), maintained in Balb-c and C57B1/6 mice, respectively. Mice were treated weekly with 5FU at the maximum tolerated dose, alone and in combination with LV. In Colon 26, neither simultaneous administration of 5FU and LV nor 5FU combined with delayed administration of LV potentiated the antitumor activity of 5FU. LV given twice — 1 hr before (50 mg/kg) and then together (50 mg/kg) with 5FU (100 mg/kg) — gave significantly better delay of tumor growth of both tumor lines than 5FU did alone (100 mg/kg). No differences were found after a total LV dose of 100 or 200 mg/kg. Delayed administration of uridine (3500 mg/kg) allowed the use of higher 5FU doses, which improved the antitumor effect on Colon 26. Systemic toxicity led to moderate weight loss in treated mice, but was comparable for mice treated with 5FU alone or combined with LV. Hematological toxicity consisted of moderate leukopenia (nadir 40%), which was observed with the most active schedule and was less severe than with 5FU alone. This schedule did not cause thrombocytopenia, but after discontinuation the thrombocyte count showed an overshoot. Addition of uridine to this schedule reduced hematological toxicity only slightly. It is concluded that LV potentiated the antitumor activity of 5FU against two solid tumor lines, i.e., a relatively resistant and a sensitive murine colon carcinoma, and that toxicity was moderate.Abbreviations 5FU
5-fluorouracil
- LV
leucovorin (folinic acid, 5-formyl-tetrahydrofolate)
- FdUMP
5-fluoro 2-deoxyuridine 5monophosphate
- TS
thymidylate synthase
- CH2-THF
5-10 methylenetetrahydrofolate
- UR
uridine
- GDF
growth delay factor
- TD
tumor doubling time
- MTD
maximum tolerated dose
- T/C
mean tumor volume of treated mice divided by mean tumor volume of control mice 相似文献
65.
Schwarz G Santamaria-Araujo JA Wolf S Lee HJ Adham IM Gröne HJ Schwegler H Sass JO Otte T Hänzelmann P Mendel RR Engel W Reiss J 《Human molecular genetics》2004,13(12):1249-1255
Substitution therapies for orphan genetic diseases, including enzyme replacement methods, are frequently hampered by the limited availability of the required therapeutic substance. We describe the isolation of a pterin intermediate from bacteria that was successfully used for the therapy of a hitherto incurable and lethal disease. Molybdenum cofactor (Moco) deficiency is a pleiotropic genetic disorder characterized by the loss of the molybdenum-dependent enzymes sulphite oxidase, xanthine oxidoreductase and aldehyde oxidase due to mutations in Moco biosynthesis genes. An intermediate of this pathway-'precursor Z'-is more stable than the cofactor itself and has an identical structure in all phyla. Thus, it was overproduced in the bacterium Escherichia coli, purified and used to inject precursor Z-deficient knockout mice that display a phenotype which resembles that of the human deficiency state. Precursor Z-substituted mice reach adulthood and fertility. Biochemical analyses further suggest that the described treatment can lead to the alleviation of most symptoms associated with human Moco deficiency. 相似文献
66.
Localization of SNARE proteins and secretory organelle proteins in astrocytes in vitro and in situ 总被引:1,自引:0,他引:1
Wilhelm A Volknandt W Langer D Nolte C Kettenmann H Zimmermann H 《Neuroscience research》2004,48(3):249-257
Astrocytes are capable of regulated release of messenger molecules. Astrocytes cultured from new born rodent brain express a variety of classical presynaptic proteins. We investigated the question whether the capability to express synaptic proteins in culture was a feature only of immature astrocytes, and whether these proteins were also expressed by astrocytes in situ. Experiments were performed with transgenic mice expressing the enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Using double fluorescence and astrocytes cultured from 1 to 16 day-old animals we show that the astrocytic expression of synaptic proteins in culture is invariant of the age of donor animals. Culturing can induce the astrocytic expression of specific synaptic proteins such as SV2, synaptophysin and SNAP-25. Astrocytes in brain sections of 1-16 day-old animals revealed a punctuate immunofluorescence for secretory carrier membrane protein (SCAMP), SNAP-23, synaptobrevin II, and cellubrevin, to a minor extent for SNAP-25 and synaptophysin, and none for SV2. Our results demonstrate that cultured astrocytes express synaptic proteins not present in situ. Nevertheless, astrocytic organelles in situ are equipped with molecules that could be involved in regulated exocytosis of messenger substances. 相似文献
67.
68.
The Modality Specificity of the Slow Negative Wave 总被引:1,自引:0,他引:1
Event-related potentials were recorded in a simple reaction time task using a 3-sec interval between S1 and S2. The sensory modalities of S1 and S2 were varied across 4 conditions to yield all possible combinations of tones and flashes. A negative component which peaked between 600 and 800 msec after S1 was specific in scalp distribution to the modality of S1 but not S2. It was concluded that this negative component is a response to S1 and not related to processes associated with anticipation of S2. A slow negative shift which peaked at S2 was largest at the vertex in all conditions, suggesting its motor origin. A trend for the latter activity to be more negative in posterior recordings when S2 was visual than auditory leaves open the possibility that the terminal CNV is a combination of motor activities and anticipation of the sensory modality of S2. 相似文献
69.
The L RNA of three Lassa virus strains originating from Nigeria, Ghana/Ivory Coast, and Sierra Leone was sequenced and the data subjected to structure predictions and phylogenetic analyses. The L gene products had 2218-2221 residues, diverged by 18% at the amino acid level, and contained several conserved regions. Only one region of 504 residues (positions 1043-1546) could be assigned a function, namely that of an RNA polymerase. Secondary structure predictions suggest that this domain is very similar to RNA-dependent RNA polymerases of known structure encoded by plus-strand RNA viruses, permitting a model to be built. Outside the polymerase region, there is little structural data, except for regions of strong alpha-helical content and probably a coiled-coil domain at the N terminus. No evidence for reassortment or recombination during Lassa virus evolution was found. The secondary structure-assisted alignment of the RNA polymerase region permitted a reliable reconstruction of the phylogeny of all negative-strand RNA viruses, indicating that Arenaviridae are most closely related to Nairoviruses. In conclusion, the data provide a basis for structural and functional characterization of the Lassa virus L protein and reveal new insights into the phylogeny of negative-strand RNA viruses. 相似文献
70.
Wilson disease: novel mutations in the ATP7B gene and clinical correlation in Brazilian patients 总被引:1,自引:0,他引:1
Deguti MM Genschel J Cancado EL Barbosa ER Bochow B Mucenic M Porta G Lochs H Carrilho FJ Schmidt HH 《Human mutation》2004,23(4):398
Wilson disease (WD) is a rare inherited autosomal recessive disorder caused by a defect in a metal transporting P-type ATPase, resulting in copper overload in various tissues and cells. The aim was to assess both the phenotype in Brazilian WD patients and the corresponding ATP7B genotype. Sixty subjects belonging to 46 pedigrees diagnosed as WD were included in this study. Direct sequencing of all 21 exons within ATP7B and their flanking introns was performed. Demographic, clinical, laboratory and histopathological data at the time of diagnosis were obtained. We identified twenty-five mutations, twelve of them reported for the first time. The c.3402delC mutation had the highest allelic frequency (30.8%), followed by the c.2123T>C (p.L708P) (16.7%). Exons 8 and 15 were the site of 62.5% of the mutations. The common European mutation c.3207C>A (p.H1069Q) was not present at all. Phenotype varied greatly among individuals with the same ATP7B genotype. Our data confirm the heterogeneity of ATP7B genotype in Brazilian WD patients. The mutational spectrum is compatible with the Brazilian history of Mediterranean immigration; however, new mutations, and different frequencies and phenotype associated with the previously known mutations characterize this population. Exons 8 and 15 should be preferentially screened in WD cases from Brazil. Phenotype variation among subjects with the same ATP7B genotype suggests that modifying factors play an additional role in the pathogenesis of WD. 相似文献