全文获取类型
收费全文 | 10910篇 |
免费 | 711篇 |
国内免费 | 68篇 |
专业分类
耳鼻咽喉 | 108篇 |
儿科学 | 281篇 |
妇产科学 | 214篇 |
基础医学 | 2219篇 |
口腔科学 | 166篇 |
临床医学 | 879篇 |
内科学 | 2027篇 |
皮肤病学 | 245篇 |
神经病学 | 1273篇 |
特种医学 | 726篇 |
外科学 | 1273篇 |
综合类 | 61篇 |
一般理论 | 1篇 |
预防医学 | 530篇 |
眼科学 | 241篇 |
药学 | 868篇 |
2篇 | |
中国医学 | 10篇 |
肿瘤学 | 565篇 |
出版年
2023年 | 83篇 |
2021年 | 139篇 |
2020年 | 183篇 |
2019年 | 117篇 |
2018年 | 195篇 |
2017年 | 163篇 |
2016年 | 194篇 |
2015年 | 221篇 |
2014年 | 305篇 |
2013年 | 345篇 |
2012年 | 446篇 |
2011年 | 476篇 |
2010年 | 318篇 |
2009年 | 364篇 |
2008年 | 446篇 |
2007年 | 466篇 |
2006年 | 445篇 |
2005年 | 450篇 |
2004年 | 456篇 |
2003年 | 422篇 |
2002年 | 433篇 |
2001年 | 171篇 |
2000年 | 145篇 |
1999年 | 146篇 |
1998年 | 171篇 |
1997年 | 185篇 |
1996年 | 143篇 |
1995年 | 125篇 |
1994年 | 111篇 |
1993年 | 103篇 |
1992年 | 102篇 |
1991年 | 80篇 |
1990年 | 87篇 |
1989年 | 121篇 |
1988年 | 107篇 |
1987年 | 69篇 |
1986年 | 66篇 |
1985年 | 83篇 |
1984年 | 64篇 |
1982年 | 68篇 |
1981年 | 59篇 |
1940年 | 70篇 |
1938年 | 71篇 |
1937年 | 81篇 |
1936年 | 73篇 |
1935年 | 68篇 |
1932年 | 60篇 |
1930年 | 59篇 |
1928年 | 59篇 |
1924年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Patrice Hermann Dominique Blanchard Blandine de Saint-Vis Franois Fossiez Claude Gaillard BAtrice Vanbervliet Francine Brire Jacques Banchereau Jean-Pierre Galizzi 《European journal of immunology》1993,23(4):961-964
To identify the ligand(s) of the human CD40 antigen, a cDNA encoding the extracellular domain of the CD40 antigen was fused to a cDNA encoding the constant region (Fc) of human IgGl. The CD40-Fc fusion protein was able to specifically bind to CD4+ and various CD8+ T cell clones activated with immobilized anti-CD3. The 125I-labeled CD40-Fc fusion protein bound anti-CD3 activated CD4+ T cell clone (MT9) with an equilibrium dissociation constant (Ka) of 10-20 nM. The human CD40-binding protein expressed on the cell surface of activated T lymphocytes is a monomeric protein of ≈ 32 kDa. Minor components of 29 kDa and 17 kDa were also detected. A small proportion of CD4+ and CD8+ blood mononuclear T cells activated by anti-CD3 expressed the CD40 ligand but its detection was best observed following depletion of B cells. Addition of B cells to purified T cells abolished the binding of CD40-Fc obtained after anti-CD3 activation. 相似文献
92.
Evaluation of Murex CMV DNA Hybrid Capture Assay for Detection and Quantitation of Cytomegalovirus Infection in Patients following Allogeneic Stem Cell Transplantation
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Holger Hebart Daphne Gamer Juergen Loeffler Claudia Mueller Christian Sinzger Gerhard Jahn Peter Bader Thomas Klingebiel Lothar Kanz Hermann Einsele 《Journal of clinical microbiology》1998,36(5):1333-1337
Murex hybrid capture DNA assay (HCS) is a solution hybridization antibody capture assay for detection and quantitation of cytomegalovirus (CMV) DNA in leukocytes. To determine whether CMV HCS is sensitive enough to initiate and monitor antiviral therapy after allogeneic stem cell transplantation (SCT), 51 consecutive SCT recipients were prospectively screened for the appearance of CMV infection by HCS, PCR, and culture assays from blood samples. Preemptive antiviral therapy was initiated after the second positive PCR result in all patients, as previously reported, and HCS was not considered for clinical decision making. A total of 417 samples were analyzed. Of these, 21 samples were found to be positive by PCR and HCS, 88 samples were PCR positive but HCS negative, and 308 were negative by both assays. Concordance of results between PCR and HCS and between HCS and blood culture was observed in 78.9 and 95.9% of the samples assayed, respectively. PCR was found to be more sensitive than HCS, and HCS was more sensitive than the blood culture assay (P < 0.0001). Four patients with symptomatic CMV infection were PCR positive prior to the onset of CMV-related symptoms, whereas HCS detected CMV DNA in three patients prior to and one at onset of CMV disease. The numbers of genomes per milliliter of blood were higher in patients with symptomatic CMV infection than in those with asymptomatic CMV infection (P = 0.06). None of the HCS-negative patients developed CMV disease. Thus, all patients with CMV disease were correctly identified by HCS; however, the lower sensitivity limit of the HCS assay may still be insufficient to allow diagnosis of CMV infection early enough to prevent CMV disease in patients following allogeneic SCT. 相似文献
93.
Differential Expression of Matrix-Metalloproteinase-1 and -2 Genes in Normal and Fibrotic Human Liver 总被引:17,自引:9,他引:17
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
94.
Frequency of Cytotoxic T Lymphocyte Precursors to Herpes Simplex Virus Type 1 as Determined by Limiting Dilution Analysis 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The conditions for establishing a limiting dilution assay to measure cytotoxic T lymphocyte precursors (CTL-P) against herpes simplex virus type 1 (HSV-1) were determined. Analysis by Poisson statistics demonstrated that the estimated frequency of HSV-1-reactive cells in the spleens of normal mice was less than 1/250,000. In contrast, mice immunized previously with infectious HSV-1 demonstrated a CTL-P frequency between 1/3,500 and 1/15,670. The generation of a maximum cytotoxic T lymphocyte response required that mice be primed in vivo with infectious virus. Immunization with inactivated virus either failed to elicit detectable CTL-P frequencies or gave frequencies markedly less than those induced with infectious virus. To obtain positive cultures, the responder cell population had to be exposed to stimulator splenocytes expressing viral antigens. Normal splenocytes without virus or normal splenocytes with T cell growth factor did not result in significant cytotoxicity. Split culture analysis comparing cytotoxicity against syngeneic and allogeneic virus-infected targets provided evidence for specificity, H-2 restriction, and the T cell nature of the CTL-P. It was determined that precursors were eliminated by treatment with anti-Thy 1, Lyt 2.1, or Lyt 1.1, indicating the CTL-P were Lyt 1(+)2(+) cells. Cytotoxicity was reduced after treatment of the responders with anti-Lyt 2 plus complement, which gave further evidence of the T cell nature of the cytotoxic T lymphocytes. These experiments demonstrated the feasibility of using the limiting dilution approach as a highly sensitive and quantitative means to measure the cell-mediated immune response to HSV-1 antigens. 相似文献
95.
Autoimmunity and inflammation due to a gain-of-function mutation in phospholipase C gamma 2 that specifically increases external Ca2+ entry 总被引:3,自引:0,他引:3
Yu P Constien R Dear N Katan M Hanke P Bunney TD Kunder S Quintanilla-Martinez L Huffstadt U Schröder A Jones NP Peters T Fuchs H de Angelis MH Nehls M Grosse J Wabnitz P Meyer TP Yasuda K Schiemann M Schneider-Fresenius C Jagla W Russ A Popp A Josephs M Marquardt A Laufs J Schmittwolf C Wagner H Pfeffer K Mudde GC 《Immunity》2005,22(4):451-465
The identification of specific genetic loci that contribute to inflammatory and autoimmune diseases has proved difficult due to the contribution of multiple interacting genes, the inherent genetic heterogeneity present in human populations, and a lack of new mouse mutants. By using N-ethyl-N-nitrosourea (ENU) mutagenesis to discover new immune regulators, we identified a point mutation in the murine phospholipase Cg2 (Plcg2) gene that leads to severe spontaneous inflammation and autoimmunity. The disease is composed of an autoimmune component mediated by autoantibody immune complexes and B and T cell independent inflammation. The underlying mechanism is a gain-of-function mutation in Plcg2, which leads to hyperreactive external calcium entry in B cells and expansion of innate inflammatory cells. This mutant identifies Plcg2 as a key regulator in an autoimmune and inflammatory disease mediated by B cells and non-B, non-T haematopoietic cells and emphasizes that by distinct genetic modulation, a single point mutation can lead to a complex immunological phenotype. 相似文献
96.
Kim YH; de Kretser DM; Temple-Smith PD; Hearn MT; McFarlane JR 《Molecular human reproduction》1997,3(4):307-313
Using mechanical and chemical dissection methods, fibrous sheath was
isolated both from normal ejaculated human spermatozoa and from rabbit
cauda epididymal spermatozoa. The same techniques did not produce a pure
preparation of fibrous sheath from ejaculated rabbit spermatozoa,
suggesting that further cross-linking and stabilization of sperm structures
occurs in response to components of the seminal plasma. The isolation
procedures were monitored by phase contrast microscopy and the purity of
the fibrous sheath was verified by electron microscopy. Sodium dodecyl
sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of isolated human
fibrous sheath revealed at least 14 protein bands of which the most
intensely stained were of molecular weight 84, 72, 66.2, 57, 32 and 28.5
kDa. The rabbit fibrous sheath revealed at least 10 protein bands, of which
the most intensely stained were 35.2, 32.7 and 28.5 kDa. The amino acid
composition of the purified fibrous sheath from human and rabbit
spermatozoa was similar, being high in aspartic acid and/or asparagine and
glutamic acid and/or glutamine, serine, alanine, leucine, lysine and
glycine, but low in histidine, tyrosine and isoleucine. This composition is
similar to that reported for the rat and suggests that mammalian sperm tail
fibrous sheaths are composed of similar types of proteins, although there
are apparent differences in protein components between species.
相似文献
97.
Marjolein P de Vries Lisette van den Bemt Karen Aretz Bart PA Thoonen Jean WM Muris Arnold DM Kester Sonja Cloosterman CP Onno van Schayck 《The British journal of general practice》2007,57(536):184-190
BACKGROUND: The efficacy of bed covers that are impermeable to house dust mites has been disputed. AIM: The aim of the present study was to investigate whether the combination of 'house dust mite impermeable' covers and a self-management plan, based on peak flow values and symptoms, leads to reduced use of inhaled corticosteroids (ICS) than self-management alone. DESIGN OF STUDY: Prospective, randomised, double blind, placebo-controlled trial. SETTING: Primary care in a south-eastern region of the Netherlands. METHOD: Asthma patients aged between 16 and 60 years with a house dust mite allergy requiring ICS were randomised to intervention and placebo groups. They were trained to use a self-management plan based on peak flow and symptoms. After a 3-month training period, the intervention commenced using house dust mite impermeable and placebo bed covers. The follow-up period was 2 years. Primary outcome was the use of ICS; secondary outcomes were peak expiratory flow parameters, asthma control, and symptoms. RESULTS: One hundred and twenty-six patients started the intervention with house dust mite impermeable or placebo bed covers. After 1 and 2 years, significant differences in allergen exposure were found between the intervention and control groups (P<0.001). No significant difference between the intervention and control groups was found in the dose of ICS (P = 0.08), morning peak flow (P = 0.52), peak flow variability (P = 0.36), dyspnoea (P = 0.46), wheezing (P = 0.77), or coughing (P = 0.41). There was no difference in asthma control between the intervention and control groups. CONCLUSION: House dust mite impermeable bed covers combined with self-management do not lead to reduced use of ICS compared with self-management alone. 相似文献
98.
Properties and regulation of chloride channels in cystic fibrosis and normal airway cells 总被引:4,自引:0,他引:4
Karl Kunzelmann Hermann Pavenstädt Rainer Greger 《Pflügers Archiv : European journal of physiology》1989,415(2):172-182
The present study examines the properties of Cl–channels in cultured respiratory cells of cystic fibrosis (CF) patients and normal (N) individuals. In excised membrane patches the conductances for CF and N Cl– channels were larger at positive as compared to negative clamp voltages (V
c): 74±2.6 (V
c > 0) and 47±2.0 pS (V
c < 0) for CF (n= 57) and 69±3.6 (V
c > 0) and 45±2.3 pS (V
c < 0) for N (n=35). The open probability (P
o) of the channel increased markedly with depolarization. Both the voltage dependence of the conductance and of P
o contribute to the outward rectification of the channel. The time histogram analysis reveals two open and two closed time constants. The selectivity of the channel was Cl–=Br– =I– > NO
3
–
gluconate. The channel was inhibited reversibly by 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) at 10–7 mol/l to 10–5 mol/l. While Cl– channels were present in cell attached patches of N cells, they were absent in those of CF cells. The mean conductance for cell attached (N) Cl– channels was 76±3.2 pS for positive clamp voltages (V
c) and 46±3.9 pS for negative V
c (n=8). When the membrane patches were excised from CF cells Cl– currents appeared spontaneously (n=19). The immediate appearance (within 1 s) of Cl– channels after excision was observed at positive (n=6) as well as at negative clamp voltage (n=13). Excision activation of CF Cl– channels was observed at low (< 10–9 mol/l) or high (10–3 mol/l) calcium activities on the cytosolic side of the excised patch. Variation of the Ca+ activity (< 10–9–10–3 mol/l) or pH (6.5–8.5) on the cytosolic side exerted no effects on these Cl– channels. These results suggest that Cl– channels are present in the apical membrane of CF and N respiratory cells but they seem to be inhibited in intact CF cells. Excision of the patch and hence removal of the cytosolic inhibitor leads to an activation of Cl– channels. The Cl– channels in excised patches of N and CF cells have identical properties. 相似文献
99.
Mahadevan MM; McIntosh Q; Miller MM; Breckinridge SM; Maris M; Moutos DM 《Human reproduction (Oxford, England)》1998,13(4):979-982
Cryopreservation of human zygotes and embryos has been routinely performed
by in-vitro fertilization clinics for many years. Karran and Legge (1996)
first reported that formaldehyde (FA) present in the cryoprotective
solutions can have a deleterious effect on mouse oocytes. FA is a
cytotoxic, carcinogenic and mutagenic chemical. The effect of FA on mouse
zygotes was investigated. In addition, the concentrations of FA in
propanediol (PROH) obtained from various sources were determined. Pooled
1-cell embryos were dispensed into droplets of modified Ham's F10 or human
tubal fluid containing various concentrations of FA. Since bovine serum
albumin (BSA) may minimize toxicity additional trials were done as above in
the absence of BSA. FA concentration in the standard 1.5 M PROH, from
different sources in water, was measured in the same assay using a standard
curve of 0-100 microM FA. FA in a complex medium had a significant
deleterious effect on embryo development and hatching but only at 1 mM
concentration (P < 0.000001; see Tables I-III). There was no significant
effect of FA at 100 microM. However, in a simple medium even 50 microM FA
decreased embryo hatching. FA was present in 1.5 M PROH from different
sources (range 1.0-35.3 microM concentration). It appears that FA
concentrations do not increase with storage because FA concentrations were
low even after opening and storage for 3 years on the shelf. This suggests
that FA is a contaminant during the manufacturing process and may vary from
manufacturer to manufacturer and batch to batch. Until further studies are
done to confirm the lack of toxicity to embryos during cryopreservation
(with or without FA scavengers) it may be prudent to screen all batches of
cryoprotectants for FA as part of quality control.
相似文献
100.
High throughput parallel analysis of hundreds of patient samples for more than 100 mutations in multiple disease genes 总被引:5,自引:0,他引:5
Shuber AP; Michalowsky LA; Nass GS; Skoletsky J; Hire LM; Kotsopoulos SK; Phipps MF; Barberio DM; Klinger KW 《Human molecular genetics》1997,6(3):337-347
As more mutations are identified in genes of known sequence, there is a
crucial need in the areas of medical genetics and genome analysis for
rapid, accurate and cost-effective methods of mutation detection. We have
developed a multiplex allele-specific diagnostic assay (MASDA) for analysis
of large numbers of samples (> 500) simultaneously for a large number of
known mutations (> 100) in a single assay. MASDA utilizes
oligonucleotide hybridization to interrogate DNA sequences. Multiplex DNA
samples are immobilized on a solid support and a single hybridization is
performed with a pool of allele-specific oligonucleotide (ASO) probes. Any
probes complementary to specific mutations present in a given sample are in
effect affinity purified from the pool by the target DNA. Sequence-specific
band patterns (fingerprints), generated by chemical or enzymatic sequencing
of the bound ASO(s), easily identify the specific mutation(s). Using this
design, in a single diagnostic assay, we tested samples for 66 cystic
fibrosis (CF) mutations, 14 beta-thalassemia mutations, two sickle cell
anemia (SCA) mutations, three Tay-Sachs mutations, eight Gaucher mutations,
four mutations in Canavan disease, four mutations in Fanconi anemia, and
five mutations in BRCA1. Each mutation was correctly identified. Finally,
in a blinded study of 106 of these mutations in > 500 patients, all
mutations were properly identified. There were no false positives or false
negatives. The MASDA assay is capable of detecting point mutations as well
as small insertion or deletion mutations. This technology is amenable to
automation and is suitable for immediate utilization for high-throughput
genetic diagnostics in clinical and research laboratories.
相似文献