全文获取类型
收费全文 | 131192篇 |
免费 | 6846篇 |
国内免费 | 170篇 |
专业分类
耳鼻咽喉 | 1965篇 |
儿科学 | 5649篇 |
妇产科学 | 4303篇 |
基础医学 | 19159篇 |
口腔科学 | 3142篇 |
临床医学 | 9590篇 |
内科学 | 24909篇 |
皮肤病学 | 3836篇 |
神经病学 | 10248篇 |
特种医学 | 5655篇 |
外国民族医学 | 34篇 |
外科学 | 21243篇 |
综合类 | 1693篇 |
一般理论 | 38篇 |
预防医学 | 6713篇 |
眼科学 | 3601篇 |
药学 | 8960篇 |
中国医学 | 336篇 |
肿瘤学 | 7134篇 |
出版年
2018年 | 1093篇 |
2017年 | 978篇 |
2016年 | 1338篇 |
2015年 | 1448篇 |
2014年 | 1929篇 |
2013年 | 2830篇 |
2012年 | 3718篇 |
2011年 | 3783篇 |
2010年 | 2311篇 |
2009年 | 2323篇 |
2008年 | 3844篇 |
2007年 | 4088篇 |
2006年 | 4228篇 |
2005年 | 4323篇 |
2004年 | 4220篇 |
2003年 | 4061篇 |
2002年 | 4057篇 |
2001年 | 7501篇 |
2000年 | 7407篇 |
1999年 | 6267篇 |
1998年 | 1780篇 |
1997年 | 1704篇 |
1996年 | 1483篇 |
1995年 | 1313篇 |
1994年 | 1207篇 |
1993年 | 1229篇 |
1992年 | 3985篇 |
1991年 | 3849篇 |
1990年 | 3807篇 |
1989年 | 3604篇 |
1988年 | 3222篇 |
1987年 | 3115篇 |
1986年 | 3037篇 |
1985年 | 2851篇 |
1984年 | 2099篇 |
1983年 | 1741篇 |
1982年 | 1028篇 |
1981年 | 1006篇 |
1980年 | 863篇 |
1979年 | 2009篇 |
1978年 | 1470篇 |
1977年 | 1228篇 |
1976年 | 1035篇 |
1975年 | 1313篇 |
1974年 | 1357篇 |
1973年 | 1325篇 |
1972年 | 1167篇 |
1971年 | 1083篇 |
1970年 | 959篇 |
1969年 | 886篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
U Burchardt K Winkler M Klagge D Balschun A Barth 《Zeitschrift für klinische Chemie und klinische Biochemie》1988,26(8):491-496
The temporal courses of dipeptidyl peptidase IV gamma-glutamyltransferase and alanine aminopeptidase were followed over 70 days in the morning urine of 15 healthy persons. Subsequent to basic statistical analysis a two-step procedure was performed, including spectral analysis and the fit of a cosine function by non-linear regression. The excretion of the 3 enzymes followed an infradian biorhythm with a mean period length of 10.04 for dipeptidyl peptidase IV, 13.34 for gamma-glutamyltransferase and 10.17 for alanine aminopeptidase. In addition to the basic rhythmic process described by the fitted cosine functions, in most of the enzyme patterns steap peaks of very high excretory activity appeared which was verified in repeated measurements. These infradian biorhythms with changes in the range of 100% and more, as well as their interindividual variations, have to be considered in assessing the excretion of enzymes. 相似文献
82.
The mitochondrial intron rI1 is a self-splicing group-II intron of algal mitochondria that can be transferred into chloroplasts
from the green alga Chlamydomonas reinhardtii for in vivo investigations (Herdenberger et al. 1994). Thus, rI1 is a suitable system to compare in vitro and in vivo RNA
processing. Interestingly, rI1 shows correct RNA splicing, although typical cis-acting exon-sequences (IBS2, δ) of group-II introns are lacking. In order to examine the effect of these exon-intron interactions on splicing, we introduced
the endogenous mitochondrial IBS2 sequence in order to produce optimal IBS2-EBS2 base pairing. In addition, the first nucleotide
of the 3′exon (δ′) was substituted to create an optimal δ-δ′ interaction. Neither of the two mutations, nor a combination of both, had any effect on the precision of the splice-site
selection. Unexpectedly, introduction of IBS2 led to a reduction in the efficiency of the second splicing step in vitro but
not in vivo. These findings lead us to conclude that trans-acting factors are present in vivo to optimize splicing efficiency. The possibility is discussed that these factors may,
for example, stabilize tertiary intron structures that are a prerequisite for correct RNA processing. Furthermore, our data
indicate that similar trans-acting factors promote correct intron splicing in chloroplasts and mitochondria.
Received: 18 October / 4 December 1997 相似文献
83.
Wolfgang B. Fischer Petra Ptschke Giesela Pompe Klaus-Jochen Eichhorn Heinz W. Siesler 《Macromolecular chemistry and physics.》1997,198(7):2057-2072
Rheo-optical Fourier transform infrared spectroscopy was used to analyze the orientational behavior of hard and soft segments of thermoplastic poly(ether urethane)s (TPU-Et) and poly(ester urethane)s (TPU-Es) and their blends with a 20 mass-% contribution of either polyethylene (PE) or polypropylene with an amorphous rubber phase (PP). The blends show a reduced stress level, lower elongation-to-break and a lower degree of orientation of the segments — especially for the TPU-Es blends — compared to those of pure TPU's when uniaxially elongated. Blends of TPU-Et with PP show reduced stress but increased strain compared to pure films of TPU-Et. This is caused by an improved adhesion of the rubber phase in the polypropylene and the polyether phase of TPU-Et. Optical micrographs visualize deformed polyolefin particles in elongated films of TPU-Et/PP blends. In the TPU-Et/PP blend we could achieve equivalent orientation for the polyolefin phase and the segments of TPU-Et caused by this higher phase adhesion compared to the other blends. Orientation functions (OF's) of absorption bands which specifically represent hard or soft polyurethane segments or which are characteristic of the polyolefin phase have been calculated to monitor the molecular alignment due to the mechanical treatment. 相似文献
84.
Presence of synaptonemal complex protein 1 transversal filament-like protein in human primary spermatocytes 总被引:1,自引:0,他引:1
Pousette A; Leijonhufvud P; Arver S; Kvist U; Pelttari J; Hoog C 《Human reproduction (Oxford, England)》1997,12(11):2414-2417
The synaptonemal complex (SC) is involved in the pairing of chromosomes
during meiosis. We found that antibodies raised against a protein component
(P1) of the mouse synaptonemal complex, mouse SCP1, also identified the SC
in human primary spermatocytes. Biopsies from 18 men presented with
infertility were evaluated by light-field microscopy and grouped into five
categories: normal spermatogenesis, Sertoli cell-only syndrome, meiotic
disturbances, spermiogenic (i.e. differentiation) disturbances, and other
combined disturbances. In all the normal subjects the SCP1 antibody
distinctly stained the synaptonemal complexes of primary spermatocytes,
whereas Sertoli cells, spermatogonia or spermatids were never stained. In
three of the groups, which had germ cells but showed spermatogenic
disturbances, the staining was similar to that seen in normal subjects. In
sharp contrast to this, in sections from men with Sertoli cell-only
syndrome no specific staining was seen. This study demonstrates that a
SCP1-related protein is also conserved in the synaptonemal complex in
meiotic cells from man. Further studies will reveal to what extent the
absence or the non-functionality of SCP1 contributes to male infertility.
相似文献
85.
M. Isohanni T. Mäkikyrö J. Moring P. Räsanen H. Hakko U. Partanen M. Koiranen P. Jones 《Social psychiatry and psychiatric epidemiology》1997,32(5):303-308
As a prerequisite to the use of the Finnish National Hospital Discharge Register in psychiatric epidemiological research, we studied the diagnostic reliability of the register in terms of the psychiatric morbidity experienced by a national birth cohort. We investigated all entries to the register for a sample based upon the Northern Finland 1966 birth cohort at the age of 16 years (n=11017). Until the end of 1993 (age 27 years), a total of 563 subjects had a register diagnosis indicating a psychiatric illness, 37 of them being schizophrenia. When operational criteria (DSM-III-R) were applied to clinical information in the available original hospital records for cases of psychosis, personality disorder and substance abuse (n=249), 71 fulfilled criteria for schizophrenia, including all of the 37 cases in the register and an additional 34 (48% false-negatives), most frequently diagnosed in the register as schizophreniform or other psychosis. Despite the official use of DSM-III-R nomenclature, it appears that the clinical concept of schizophrenia in Finland, manifest within the register, remains very restrictive. The application of operational criteria is a necessary prerequisite for scientific research on schizophrenia. 相似文献
86.
U. Meyding-Lamadé K. Rieke D. Krieger W. Hacke Michael Forsting Klaus Sartor Christian Sommer 《Journal of neurology》1995,242(5):335-343
Acute ischaemia of the vertebrobasilar circulation leads to a variety of clinical manifestation and is mostly due to cardiogenic or artery-to-artery embolism. We describe four neurological emergency situations involving vertebrobasilar artery aclusion of other origins: basilar migraine, extrinsic compression by rheumatoid inflammatory tissue, generalized vasculitis in subacute rheumatic fever and basilar artery dissection. The differential diagnosis of acute vertebrobasilar artery occlusion may have an important impact on patient management. 相似文献
87.
J A Temlett A Ming M Saling V U Fritz A Blumenfeld T R Bilchik A L Becker P B Fourie H E Reef 《Suid-Afrikaanse tydskrif vir geneeskunde》1990,78(11):680-685
Patients with moderately severe Parkinson's disease complicated by the adverse effects of chronic levodopa use benefited from the addition of bromocriptine (Parlodel; Sandoz) in doses up to 26 mg daily, which allowed an approximate 30% reduction of levodopa dose. This resulted in a significant decrease in the amount of levodopa side-effects while maintaining or improving the original parkinsonian clinical stage. Increased effectiveness in these patients was not associated with increased dosage beyond 25-30 mg daily. When the doses of bromocriptine were increased slowly, the adverse reactions were minor and usually transient. 相似文献
88.
U K Wenderoth R Bachor G Egghart D Frohneberg K Miller R E Hautmann 《The Journal of urology》1990,143(3):492-6; discussion 496-7
The ileal neobladder produces a completely detubularized, low pressure, high capacity reservoir constructed from ileum without any valves. From April 1986 through May 1989, 113 patients underwent this procedure at our institution. Of these patients 99 underwent simultaneous radical cystectomy for bladder cancer and 14 underwent bladder augmentation. The mean postoperative followup was 14.4 months, with a range of 1 to 36 months. There was no perioperative mortality. However, 7 patients died more than 2 months postoperatively: 5 of tumor progression, 1 of pneumonia and severe metabolic acidosis, and 1 of septicemia of unknown cause. Reoperation was necessary in only 13 patients; 10 patients required urethrotomy or dilation of urethral strictures. Day and night continence was preserved in 82.1% of all patients. Stress incontinence, which must be corrected by an artificial sphincter, was found in 4 patients (4.2%) and night-time incontinence that required an external device occurred in 5 (5.3%). Eight patients (8.4%) with mild stress incontinence required no further treatment. Pressure waves exceeding 22 cm. water seldom occurred and then only at maximum capacity. Our experience with this relatively simple system without a nipple is an overwhelming success. The need for reoperation is extraordinarily low and the high reservoir capacity results in continence from the beginning in most patients. The concept is sound and offers a genuine alternative to any form of cutaneous urinary diversion with an incidence of complications not higher than after standard supravesical urinary diversion. 相似文献
89.
I U Svistoniuk 《Klinichna khirurhiia / Ministerstvo okhorony zdorov'ia Ukra?ny, Naukove tovarystvo khirurhiv Ukra?ny》1990,(3):47-49
In 15 patients with the postburn neck deformation, the plasty with a musculocutaneous flap of the musculus pectoralis major was employed. Use of the technique permits to avoid prolonged immobilization of a neck. A good functional and cosmetic result has been noted. 相似文献
90.
Liver transplantation in HBsAg positive patients 总被引:1,自引:0,他引:1
G Blumhardt P Neuhaus W O Bechstein R Steffen U Hopf B M?ller R Raakow H Keck 《Transplantation proceedings》1990,22(4):1517-1518