全文获取类型
收费全文 | 5892篇 |
免费 | 527篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 66篇 |
儿科学 | 250篇 |
妇产科学 | 102篇 |
基础医学 | 648篇 |
口腔科学 | 96篇 |
临床医学 | 667篇 |
内科学 | 1016篇 |
皮肤病学 | 50篇 |
神经病学 | 489篇 |
特种医学 | 490篇 |
外科学 | 855篇 |
综合类 | 112篇 |
一般理论 | 6篇 |
预防医学 | 766篇 |
眼科学 | 113篇 |
药学 | 335篇 |
中国医学 | 9篇 |
肿瘤学 | 368篇 |
出版年
2022年 | 34篇 |
2021年 | 86篇 |
2020年 | 50篇 |
2019年 | 77篇 |
2018年 | 99篇 |
2017年 | 80篇 |
2016年 | 84篇 |
2015年 | 94篇 |
2014年 | 148篇 |
2013年 | 182篇 |
2012年 | 292篇 |
2011年 | 296篇 |
2010年 | 193篇 |
2009年 | 166篇 |
2008年 | 223篇 |
2007年 | 290篇 |
2006年 | 294篇 |
2005年 | 264篇 |
2004年 | 233篇 |
2003年 | 190篇 |
2002年 | 188篇 |
2001年 | 131篇 |
2000年 | 137篇 |
1999年 | 103篇 |
1998年 | 151篇 |
1997年 | 115篇 |
1996年 | 113篇 |
1995年 | 80篇 |
1994年 | 95篇 |
1993年 | 94篇 |
1992年 | 126篇 |
1991年 | 93篇 |
1990年 | 104篇 |
1989年 | 132篇 |
1988年 | 120篇 |
1987年 | 115篇 |
1986年 | 91篇 |
1985年 | 93篇 |
1984年 | 90篇 |
1983年 | 57篇 |
1982年 | 55篇 |
1981年 | 58篇 |
1980年 | 63篇 |
1979年 | 59篇 |
1978年 | 42篇 |
1977年 | 57篇 |
1976年 | 54篇 |
1975年 | 43篇 |
1972年 | 36篇 |
1969年 | 32篇 |
排序方式: 共有6438条查询结果,搜索用时 312 毫秒
61.
Susceptibility testing of multidrug-resistant Staphylococcus aureus with the Sceptor microdilution system. 下载免费PDF全文
The antimicrobial susceptibilities of Staphylococcus aureus isolates were concurrently determined by the Sceptor system (BBL Microbiology Systems, Cockeysville, Md.) and by the standard disk diffusion method. For the methicillin-resistant isolates, there was greater than 98% agreement between the two test results with penicillin G, erythromycin, clindamycin, tetracycline, gentamicin, and tobramycin. Major disagreements (susceptible by one method and resistant by the other) were 7% for methicillin, 13.5% for cephalothin, 3.5% for cefamandole, and 27% for amikacin. The major discrepancies for methicillin were eliminated by supplementing the inoculum broth with salt. For methicillin-susceptible isolates, agreement between the two methods was 96 to 100% for all antibiotics except amikacin. 相似文献
62.
Comparison of three isolation systems for the culture of mycobacteria from respiratory and non-respiratory samples 总被引:3,自引:0,他引:3 下载免费PDF全文
AIMS: To compare the recovery of mycobacteria from clinical samples using the MB/BacT rapid culture system with that obtained using egg medium or the Bactec radiometric method. METHODS: The three methods were compared using 681 clinical samples (462 respiratory and 219 non-respiratory samples) and eight external quality control strains. Culture media were incubated at 35-37 degrees C for six weeks in the MB/BacT system and for 12 weeks in the Bactec system and on egg medium. Solid media were examined macroscopically once a week and the Bactec vials were read six times in the first two weeks, and then weekly for the next 10 weeks (a growth index > 50 indicated a positive vial). The MB/BacT system positive vials were unloaded from the machine as soon as possible after detection. Confirmation of growth for all systems was by Ziehl-Neelson stained smears. Isolates were identified by a combination of phenotypic and molecular methods. RESULTS: Of the 681 clinical samples, 59 (8.7%) were positive on culture, including 23 strains of Mycobacterium tuberculosis. None of the three systems recovered all of the isolates, but each recovered mycobacteria not detected by either of the other two systems. After six weeks incubation, isolation rates were 87%, 78%, and 90%, and mean times to detection were 13, 19, and nine days for the MB/BacT, egg medium, and Bactec systems, respectively. Although the MB/BacT system was slightly slower than the Bactec system, the biomass was greater, allowing earlier use of molecular probes and earlier inoculation of susceptibility tests. CONCLUSIONS: The MB/BacT system provides comparable performance to the Bactec radiometric system, without the problems of disposal of radioactive waste. Optimal recovery is obtained when culture on egg medium is used in conjunction with a rapid culture system. 相似文献
63.
64.
Macropotrema pertinax gen. et sp. nov. (Digenea: Paramphistomidae) is described from the caecum of the macropodid marsupial Macropus agilis (Gould, 1842) from northern Australia. The new genus is characterised as follows: ventro-terminal acetabulum bearing many papillae; oral sucker with constriction and paired diverticula; oesophagus with muscular bulb; cirrus sac and genital sucker absent; testes symmetrical, unlobed, preovarian; Laurer's canal opening anterior to excretory pore. The genus is placed in the subfamily Pseudodiscinae N?smark, 1937. At the point where the worm attaches to the caecal wall of the host, the entire mucosa is destroyed and there is an inflammatory cell infiltration in the intact mucosa surrounding the attachment site. 相似文献
65.
Role of nitric oxide in the biology, physiology and pathophysiology of reproduction 总被引:13,自引:0,他引:13
Following its benchmark discovery, nitric oxide (NO) is nowknown to play important functional roles in a variety of physiologicalsystems. Within the vasculature, NO induces vasodilation, inhibitsplatelet aggregation, prevents neutrophil/platelet adhesionto endothelial cells, inhibits smooth muscle cell proliferationand migration, regulates programmed cell death (apoptosis) andmaintains endothelial cell barrier function. NO generated byneurons acts as a neurotransmitter, whereas NO generated bymacrophages in response to invading microbes acts as an antimicrobialagent. Because neurons, blood vessels and cells of the immunesystem are integral parts of the reproductive organs, and inview of the important functional role that NO plays in thosesystems, it is likely that NO is an important regulator of thebiology and physiology of the reproductive system. Indeed, inthe past 10 years, NO has established itself as a polyvalentmolecule which plays a decisive role in regulating multiplefunctions within the female as well as the male reproductivesystem. This review provides an overview of the role of NO invarious reproductive organs under physiological and pathologicalconditions. 相似文献
66.
Mutation spectrum and genotype-phenotype analyses in Cowden disease and Bannayan-Zonana syndrome, two hamartoma syndromes with germline PTEN mutation 总被引:22,自引:1,他引:22
Marsh DJ; Coulon V; Lunetta KL; Rocca-Serra P; Dahia PL; Zheng Z; Liaw D; Caron S; Duboue B; Lin AY; Richardson AL; Bonnetblanc JM; Bressieux JM; Cabarrot-Moreau A; Chompret A; Demange L; Eeles RA; Yahanda AM; Fearon ER; Fricker JP; Gorlin RJ; Hodgson SV; Huson S; Lacombe D; Eng C 《Human molecular genetics》1998,7(3):507-515
The tumour suppressor gene PTEN , which maps to 10q23.3 and encodes a 403
amino acid dual specificity phosphatase (protein tyrosine phosphatase;
PTPase), was shown recently to play a broad role in human malignancy.
Somatic PTEN deletions and mutations were observed in sporadic breast,
brain, prostate and kidney cancer cell lines and in several primary tumours
such as endometrial carcinomas, malignant melanoma and thyroid tumours. In
addition, PTEN was identified as the susceptibility gene for two hamartoma
syndromes: Cowden disease (CD; MIM 158350) and Bannayan-Zonana (BZS) or
Ruvalcaba-Riley-Smith syndrome (MIM 153480). Constitutive DNA from 37 CD
families and seven BZS families was screened for germline PTEN mutations.
PTEN mutations were identified in 30 of 37 (81%) CD families, including
missense and nonsense point mutations, deletions, insertions, a
deletion/insertion and splice site mutations. These mutations were
scattered over the entire length of PTEN , with the exception of the first,
fourth and last exons. A 'hot spot' for PTEN mutation in CD was identified
in exon 5 that contains the PTPase core motif, with 13 of 30 (43%) CD
mutations identified in this exon. Seven of 30 (23%) were within the core
motif, the majority (five of seven) of which were missense mutations,
possibly pointing to the functional significance of this region. Germline
PTEN mutations were identified in four of seven (57%) BZS families studied.
Interestingly, none of these mutations was observed in the PTPase core
motif. It is also worthy of note that a single nonsense point mutation,
R233X, was observed in the germline DNA from two unrelated CD families and
one BZS family. Genotype-phenotype studies were not performed on this small
group of BZS families. However, genotype-phenotype analysis inthe group of
CD families revealed two possible associations worthy of follow-up in
independent analyses. The first was an association noted in the group of CD
families with breast disease. A correlation was observed between the
presence/absence of a PTEN mutation and the type of breast involvement
(unaffected versus benign versus malignant). Specifically and more
directly, an association was also observed between the presence of a PTEN
mutation and malignant breast disease. Secondly, there appeared to be an
interdependent association between mutations upstream and within the PTPase
core motif, the core motif containing the majority of missense mutations,
and the involvement of all major organ systems (central nervous system,
thyroid, breast, skin and gastrointestinal tract). However, these
observations would need to be confirmed by studying a larger number of CD
families.
相似文献
67.
68.
ATRX encodes a novel member of the SNF2 family of proteins: mutations point to a common mechanism underlying the ATR-X syndrome 总被引:11,自引:3,他引:11
Picketts DJ; Higgs DR; Bachoo S; Blake DJ; Quarrell OW; Gibbons RJ 《Human molecular genetics》1996,5(12):1899-1907
It was shown recently that mutations of the ATRX gene give rise to a
severe, X-linked form of syndromal mental retardation associated with alpha
thalassaemia (ATR-X syndrome). In this study, we have characterised the
full-length cDNA and predicted structure of the ATRX protein. Comparative
analysis shows that it is an entirely new member of the SNF2 subgroup of a
superfamily of proteins with similar ATPase and helicase domains. ATRX
probably acts as a regulator of gene expression. Definition of its genomic
structure enabled us to identify four novel splicing defects by screening
52 affected individuals. Correlation between these and previously
identified mutations with variations in the ATR-X phenotype provides
insights into the pathophysiology of this disease and the normal role of
the ATRX protein in vivo.
相似文献
69.
70.
High-Throughput Generation of P. falciparum Functional Molecules by Recombinational Cloning 总被引:2,自引:0,他引:2 下载免费PDF全文
Joo Carlos Aguiar Joshua LaBaer Peter L. Blair Victoria Y. Shamailova Malvika Koundinya Joshua A. Russell Fengying Huang Wenhong Mar Robert M. Anthony Adam Witney Sonia R. Caruana Leonardo Brizuela John B. Sacci Jr. Stephen L. Hoffman Daniel J. Carucci 《Genome research》2004,14(10B):2076-2082
Large-scale functional genomics studies for malaria vaccine and drug development will depend on the generation of molecular tools to study protein expression. We examined the feasibility of a high-throughput cloning approach using the Gateway system to create a large set of expression clones encoding Plasmodium falciparum single-exon genes. Master clones and their ORFs were transferred en masse to multiple expression vectors. Target genes (n = 303) were selected using specific sets of criteria, including stage expression and secondary structure. Upon screening four colonies per capture reaction, we achieved 84% cloning efficiency. The genes were subcloned in parallel into three expression vectors: a DNA vaccine vector and two protein expression vectors. These transfers yielded a 100% success rate without any observed recombination based on single colony screening. The functional expression of 95 genes was evaluated in mice with DNA vaccine constructs to generate antibody against various stages of the parasite. From these, 19 induced antibody titers against the erythrocytic stages and three against sporozoite stages. We have overcome the potential limitation of producing large P. falciparum clone sets in multiple expression vectors. This approach represents a powerful technique for the production of molecular reagents for genome-wide functional analysis of the P. falciparum genome and will provide for a resource for the malaria resource community distributed through public repositories. 相似文献